Hello All,
I'm trying to arrive at a reliable method of measuring phase noise for the testing I'm doing on the 70 cm Eagle Receiver.
I recently purchased an SDR-IQ software defined radio. It makes a great spectrum analyzer below 30 MHz, with a very low noise floor and great resolution. I took it to work to show to my coworkers and the lab manager liked it so much he purchased the big brother of this unit, the SDR-14, which I borrowed and brought back to my shop. I also sent my Agilent 8566B spectrum analyzer out for calibration so now I have three pieces of test equipment that I can use to measure the phase noise of the 70 cm Receiver. My problem is that I cant get any two of them to agree...
Ive fed the same 10 MHz 0 dBm signal into each unit, recorded all of their settings and created the attached PDF file. As you will see, they all differ. If we look at the 120 Hz power supply sidebands you get the following:
SDR-IQ: -102 dBm
SDR-14: -93 dBm
8566B: -84 dBm
The 8566B automatically calculates RMS noise levels normalized to a 1 Hz noise power bandwidth by correcting for the analyzers log amplifier and detector response and compensating for the resolution bandwidth setting. Its capable of accurately measuring noise levels down to 10 dB above the spectrum analyzers noise level (-131.6 dBm) and reading out in steps of ±0.1 dB. At a 150 Hz offset it measures -104.0 dBc/Hz. Looking at the two SDR units its hard to reconcile this measurement with either of them, or to reconcile any of the power supply sidebands.
Both SDR units measure power levels in a very linear way. Ive confirmed their accuracy at the levels Im interested in around -90 dBm.
Can anyone shed any light on this? No combination of FFT block size, span, RF or IF gain, or filter bandwidth can make any two of these devices agree on the noise floor or the amplitude of the power supply sidbands.
73,
Juan WA6HTP
A man with a watch will always know what time it is - a man with two watched can never be sure.
Since the HP 8566 is calibrated, I'd trust it more for making absolute level measurements.
Each of these units is measuring the sum of the phase noise of their internal oscillator and the external signal. The SDR14 and SDR-IQ have lower close-in phase noise because of the crystal oscillator. The source and measurement equipment may both have 120 Hz sidebands and they may interact. In the case of the HP 8566, the 120 Hz sidebands are riding on top of the 1/f phase noise so they appear elevated.
Is the 10 MHz source running on battery power? At 120 Hz there will also be interaction because of multiple ground paths. The resulting currents can modulate the oscillators or amplifiers and induce extraneous signals. You need a single point ground for measurements in this range.
73,
John KD6OZH ----- Original Message ----- From: Juan Rivera To: eagle@amsat.org ; Bill Ress ; Dave Black (Home) ; Dave Black (Work) ; Dave hartzell ; David Smith ; Don Ferguson ; Juan. Rivera (Home) ; Juan.Rivera (Work) ; Samsonoff@Mac. Com Sent: Saturday, July 07, 2007 17:19 UTC Subject: [eagle] Help Needed
Hello All,
I'm trying to arrive at a reliable method of measuring phase noise for the testing I'm doing on the 70 cm Eagle Receiver.
I recently purchased an SDR-IQ software defined radio. It makes a great spectrum analyzer below 30 MHz, with a very low noise floor and great resolution. I took it to work to show to my coworkers and the lab manager liked it so much he purchased the big brother of this unit, the SDR-14, which I borrowed and brought back to my shop. I also sent my Agilent 8566B spectrum analyzer out for calibration so now I have three pieces of test equipment that I can use to measure the phase noise of the 70 cm Receiver. My problem is that I can't get any two of them to agree...
I've fed the same 10 MHz 0 dBm signal into each unit, recorded all of their settings and created the attached PDF file. As you will see, they all differ. If we look at the 120 Hz power supply sidebands you get the following:
SDR-IQ: -102 dBm
SDR-14: -93 dBm
8566B: -84 dBm
The 8566B automatically calculates RMS noise levels normalized to a 1 Hz noise power bandwidth by correcting for the analyzer's log amplifier and detector response and compensating for the resolution bandwidth setting. It's capable of accurately measuring noise levels down to 10 dB above the spectrum analyzer's noise level (-131.6 dBm) and reading out in steps of ±0.1 dB. At a 150 Hz offset it measures -104.0 dBc/Hz. Looking at the two SDR units it's hard to reconcile this measurement with either of them, or to reconcile any of the power supply sidebands.
Both SDR units measure power levels in a very linear way. I've confirmed their accuracy at the levels I'm interested in around -90 dBm.
Can anyone shed any light on this? No combination of FFT block size, span, RF or IF gain, or filter bandwidth can make any two of these devices agree on the noise floor or the amplitude of the power supply sidbands.
73,
Juan - WA6HTP
A man with a watch will always know what time it is - a man with two watched can never be sure.
------------------------------------------------------------------------------
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Hi Juan,
What your likely seeing when looking at your low noise 10 MHz signal is the phase noise floors of the three devices your using for measurement.
For instance, the 8566B has a typical phase noise floor at 100 to 320 Hz of around -95 dBc/Hz and it's spec'ed at -80 dBc/Hz (yours might be lower) which is essentially the noise of the phase locked YIG first LO in the 8566B and you won't be able to resolve any thing lower than that, at those frequency offsets. The -85dBc spur at 120 Hz could very well be the 120 Hz spur on the 8566B's LO's. I can't recall what the power line spurious spec is for the 8566B but it should be in your manual.
I can't speak for the SDR's, not having played with them, but I would guess that their phase noise will be much better than the 8566B. Hence you would read a different value than obtained on the 8566B. So what now - right?
Well, from the data you've shown earlier for the 10.7 MHz output of the URx, its phase noise is greater than that of the 8566B's phase noise floor (not to be confused with its "sensitivity floor"). Hence the reading you get on the 8566B is the phase noise of the combined LO's in the URx and the phase noise of your 435 MHz signal generator (and let's assume its at least 10dB lower than the phase of the URx LO's and hence you can ignore it) . Now if you take that data on the 8566B and then run the URx 10.7 output into the SDR's, you should get the same phase noise readings (or very close to it).
In other words - if the expected phase noise of the device under test is greater (by at least 10dB) than the phase noise floor of the measuring device, the measurement is going to be accurate enough for our application.
Clear as mud - huh? Phase noise measurements are not straight forward in most cases unless you have a "phase noise analyzer" ala HP or RDL.
Regards...Bill - N6GHz
Juan Rivera wrote:
Hello All,
I'm trying to arrive at a reliable method of measuring phase noise for the testing I'm doing on the 70 cm Eagle Receiver.
I recently purchased an SDR-IQ software defined radio. It makes a great spectrum analyzer below 30 MHz, with a very low noise floor and great resolution. I took it to work to show to my coworkers and the lab manager liked it so much he purchased the big brother of this unit, the SDR-14, which I borrowed and brought back to my shop. I also sent my Agilent 8566B spectrum analyzer out for calibration so now I have three pieces of test equipment that I can use to measure the phase noise of the 70 cm Receiver. My problem is that I can’t get any two of them to agree...
I’ve fed the same 10 MHz 0 dBm signal into each unit, recorded all of their settings and created the attached PDF file. As you will see, they all differ. If we look at the 120 Hz power supply sidebands you get the following:
SDR-IQ: -102 dBm
SDR-14: -93 dBm
8566B: -84 dBm
The 8566B automatically calculates RMS noise levels normalized to a 1 Hz noise power bandwidth by correcting for the analyzer’s log amplifier and detector response and compensating for the resolution bandwidth setting. It’s capable of accurately measuring noise levels down to 10 dB above the spectrum analyzer’s noise level (-131.6 dBm) and reading out in steps of ±0.1 dB. At a 150 Hz offset it measures -104.0 dBc/Hz. Looking at the two SDR units it’s hard to reconcile this measurement with either of them, or to reconcile any of the power supply sidebands.
Both SDR units measure power levels in a very linear way. I’ve confirmed their accuracy at the levels I’m interested in around -90 dBm.
Can anyone shed any light on this? No combination of FFT block size, span, RF or IF gain, or filter bandwidth can make any two of these devices agree on the noise floor or the amplitude of the power supply sidbands.
73,
Juan – WA6HTP
/A man with a watch will always know what time it is - a man with two watched can never be sure./
Hi everyone and thanks for the suggestions!
I rummaged around in my junk box and found a high quality ovenized 10 MHz oscillator that I pulled out of an organ donor HP signal generator last year. I mounted that bad boy in a box and powered it up with two 9-volt batteries (The oven is off so its slightly off frequency). The plot below shows what it looks like on the 8566B. Thats the cleanest signal Ive ever seen from anything in my shop. The 8566B says the SSB phase noise at a 5 kHz offset is -106.7 dBc/Hz.
I then looked at it on the SDR-14 which is powered from a wall wart and it had lots of 120 Hz sidebands. I whipped up a power cord so I could run the SDR-14 from a lab bench supply, and guess what... Sidebands gone! Its a loaner so I wont use it after this weekend.
Next I went to my SDR-IQ half way expecting to have to dig into it to fix ripple since its powered from the PCs USB port, but it was clean. I had to stick a 21.5 dB pad in the line to keep from overloading the SDR-IQ so the levels are relative.
Now, were starting to cook with Gas! My plan is to take the battery-powered oscillator to work Monday and see if I can check phase noise using something expensive and designed for the job. Then Ill have a standard I can bring back here for comparison. Once we iron out this last ambiguity we should all have confidence when we get to the Rev-B receiver testing.
73, and thanks for the help!
Juan
-----Original Message----- From: Bill Ress [mailto:bill@hsmicrowave.com] Sent: Saturday, July 07, 2007 6:14 PM To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org Subject: Re: Help Needed
Hi Juan,
What your likely seeing when looking at your low noise 10 MHz signal is
the phase noise floors of the three devices your using for measurement.
For instance, the 8566B has a typical phase noise floor at 100 to 320 Hz
of around -95 dBc/Hz and it's spec'ed at -80 dBc/Hz (yours might be
lower) which is essentially the noise of the phase locked YIG first LO
in the 8566B and you won't be able to resolve any thing lower than that,
at those frequency offsets. The -85dBc spur at 120 Hz could very well be
the 120 Hz spur on the 8566B's LO's. I can't recall what the power line
spurious spec is for the 8566B but it should be in your manual.
I can't speak for the SDR's, not having played with them, but I would
guess that their phase noise will be much better than the 8566B. Hence
you would read a different value than obtained on the 8566B. So what now
- right?
Well, from the data you've shown earlier for the 10.7 MHz output of the
URx, its phase noise is greater than that of the 8566B's phase noise
floor (not to be confused with its "sensitivity floor"). Hence the
reading you get on the 8566B is the phase noise of the combined LO's in
the URx and the phase noise of your 435 MHz signal generator (and let's
assume its at least 10dB lower than the phase of the URx LO's and hence
you can ignore it) . Now if you take that data on the 8566B and then run
the URx 10.7 output into the SDR's, you should get the same phase noise
readings (or very close to it).
In other words - if the expected phase noise of the device under test is
greater (by at least 10dB) than the phase noise floor of the measuring
device, the measurement is going to be accurate enough for our application.
Clear as mud - huh? Phase noise measurements are not straight forward in
most cases unless you have a "phase noise analyzer" ala HP or RDL.
Regards...Bill - N6GHz
Juan Rivera wrote:
Hello All,
I'm trying to arrive at a reliable method of measuring phase noise for
the testing I'm doing on the 70 cm Eagle Receiver.
I recently purchased an SDR-IQ software defined radio. It makes a
great spectrum analyzer below 30 MHz, with a very low noise floor and
great resolution. I took it to work to show to my coworkers and the
lab manager liked it so much he purchased the big brother of this
unit, the SDR-14, which I borrowed and brought back to my shop. I also
sent my Agilent 8566B spectrum analyzer out for calibration so now I
have three pieces of test equipment that I can use to measure the
phase noise of the 70 cm Receiver. My problem is that I cant get any
two of them to agree...
Ive fed the same 10 MHz 0 dBm signal into each unit, recorded all of
their settings and created the attached PDF file. As you will see,
they all differ. If we look at the 120 Hz power supply sidebands you
get the following:
SDR-IQ: -102 dBm
SDR-14: -93 dBm
8566B: -84 dBm
The 8566B automatically calculates RMS noise levels normalized to a 1
Hz noise power bandwidth by correcting for the analyzers log
amplifier and detector response and compensating for the resolution
bandwidth setting. Its capable of accurately measuring noise levels
down to 10 dB above the spectrum analyzers noise level (-131.6 dBm)
and reading out in steps of ±0.1 dB. At a 150 Hz offset it measures
-104.0 dBc/Hz. Looking at the two SDR units its hard to reconcile
this measurement with either of them, or to reconcile any of the power
supply sidebands.
Both SDR units measure power levels in a very linear way. Ive
confirmed their accuracy at the levels Im interested in around -90 dBm.
Can anyone shed any light on this? No combination of FFT block size,
span, RF or IF gain, or filter bandwidth can make any two of these
devices agree on the noise floor or the amplitude of the power supply
sidbands.
73,
Juan WA6HTP
/A man with a watch will always know what time it is - a man with two
watched can never be sure./
Hi Bill,
See my progress report for details on my afternoon project. If I can get this battery powered oscillator tested with the latest and greatest equipment then I can bring it back here and use it as a standard while reconciling the differences I see between the 8566 and the SDR-IQ.
I first started spotting 120 Hz spurs in my two signal generators before the 8566 went into cal. It was in cal when it went in but of course I had no way to know that until I got it back, so previous data I have put out is accurate. Now it's tweaked and tuned up. I can tell it's even better than before. Anyway, the expensive precision signal generator has a much cleaning-looking signal than the inexpensive one. They're both Agilent but the expensive one is made up of a collection of milled enclosures interconnected with lots of semi-rigid .141 coax and the inexpensive one is mostly one huge PCB with a few tin compartments for the RF.
As to relative phase noise, the "good" signal generator is much cleaner than the 70 cm Receiver so that shouldn't be an issue, at least with this rev-A version. I'll do a quick check of the battery -powered unit and the "good" HP 8662A and let you know how they compare.
Lastly, everything you say is clear. What I dont understand is the workings of the SDR-IQ. You can adjust the RF and IF gain, the FFT bin size, the span, and so forth. They often have unexpected impacts on the signal. Spurs come and go, 120 Hz goes up and down, etc. Once I get back here with that battery-powered oscillator I think I can come up with a procedure to get accurate phase noise results from the DSR-IQ, or reach a determination that it is not suited for that particular measurement. I'm anxious to find out which it will be...
73,
Juan
-----Original Message----- From: Bill Ress [mailto:bill@hsmicrowave.com] Sent: Saturday, July 07, 2007 6:14 PM To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org Subject: Re: Help Needed
Hi Juan,
What your likely seeing when looking at your low noise 10 MHz signal is the phase noise floors of the three devices your using for measurement.
For instance, the 8566B has a typical phase noise floor at 100 to 320 Hz of around -95 dBc/Hz and it's spec'ed at -80 dBc/Hz (yours might be lower) which is essentially the noise of the phase locked YIG first LO in the 8566B and you won't be able to resolve any thing lower than that, at those frequency offsets. The -85dBc spur at 120 Hz could very well be the 120 Hz spur on the 8566B's LO's. I can't recall what the power line spurious spec is for the 8566B but it should be in your manual.
I can't speak for the SDR's, not having played with them, but I would guess that their phase noise will be much better than the 8566B. Hence you would read a different value than obtained on the 8566B. So what now - right?
Well, from the data you've shown earlier for the 10.7 MHz output of the URx, its phase noise is greater than that of the 8566B's phase noise floor (not to be confused with its "sensitivity floor"). Hence the reading you get on the 8566B is the phase noise of the combined LO's in the URx and the phase noise of your 435 MHz signal generator (and let's assume its at least 10dB lower than the phase of the URx LO's and hence you can ignore it) . Now if you take that data on the 8566B and then run the URx 10.7 output into the SDR's, you should get the same phase noise readings (or very close to it).
In other words - if the expected phase noise of the device under test is greater (by at least 10dB) than the phase noise floor of the measuring device, the measurement is going to be accurate enough for our application.
Clear as mud - huh? Phase noise measurements are not straight forward in most cases unless you have a "phase noise analyzer" ala HP or RDL.
Regards...Bill - N6GHz
Juan Rivera wrote:
Hello All,
I'm trying to arrive at a reliable method of measuring phase noise for the testing I'm doing on the 70 cm Eagle Receiver.
I recently purchased an SDR-IQ software defined radio. It makes a great spectrum analyzer below 30 MHz, with a very low noise floor and great resolution. I took it to work to show to my coworkers and the lab manager liked it so much he purchased the big brother of this unit, the SDR-14, which I borrowed and brought back to my shop. I also sent my Agilent 8566B spectrum analyzer out for calibration so now I have three pieces of test equipment that I can use to measure the phase noise of the 70 cm Receiver. My problem is that I cant get any two of them to agree...
Ive fed the same 10 MHz 0 dBm signal into each unit, recorded all of their settings and created the attached PDF file. As you will see, they all differ. If we look at the 120 Hz power supply sidebands you get the following:
SDR-IQ: -102 dBm
SDR-14: -93 dBm
8566B: -84 dBm
The 8566B automatically calculates RMS noise levels normalized to a 1 Hz noise power bandwidth by correcting for the analyzers log amplifier and detector response and compensating for the resolution bandwidth setting. Its capable of accurately measuring noise levels down to 10 dB above the spectrum analyzers noise level (-131.6 dBm) and reading out in steps of ±0.1 dB. At a 150 Hz offset it measures -104.0 dBc/Hz. Looking at the two SDR units its hard to reconcile this measurement with either of them, or to reconcile any of the power supply sidebands.
Both SDR units measure power levels in a very linear way. Ive confirmed their accuracy at the levels Im interested in around -90 dBm.
Can anyone shed any light on this? No combination of FFT block size, span, RF or IF gain, or filter bandwidth can make any two of these devices agree on the noise floor or the amplitude of the power supply sidbands.
73,
Juan WA6HTP
/A man with a watch will always know what time it is - a man with two watched can never be sure./
Hi Guys,
Juan has done a lot of outstanding work which resulted in some substantial critiquing of the CAN-Do! (Affectionately called a "widget.") It is unfortunate that it has taken several years since the CAN-Do! was designed and then 100 units built before an application of sufficient sensitivity used it to discover it's shortcomings. History can provide lessons that I hope we can learn from, but it seldom provides solutions to the problems encountered. Lyle and I have exchanged a few thoughts privately and it seems it may now be time to consider solutions to the problems found.
The only practical way to accomplish this is to develop the next generation CAN interface device. Dare I call it the CAN-Do-Too! ?
All technical specifications should remain the same. What this really means is that a next-generation controller must run *exactly* the same firmware currently running the CAN-Do! .
All specifications added or redefined should be carefully defined and be measurable.
General specifications that we worked from before were that the widget should use as little power as possible and consume as little of a module's volume as possible. The first of these should remain the same, "use as little power as possible."
But the second should be changed to "consume as little of the connector panel space as possible" even if it means consuming a little more of the module volume. This means the widget PCB and components should not extend beyond the dimensions of the DA-15P connector in either dimension. A possible compromise to this would be to let the PCB run past one end of the DA-15P but not more than the DA-15P is forced away from the side of the box by the box design.
The power supply could be completely redesigned. Or the inductor of the existing supply could be exchanged for one that is a toroid (the existing one is not). If someone wants to step up and design a new power supply, great! If not, then we would simply change the inductor. I'd sure like to see someone take this on. With so many of these in the satellite, only a few milliwatts is important. And the noise issue Juan uncovered is *very* important.
It may be that some, or maybe all, of the widget should be enclosed in a metal box. It may be that just changing the inductor would allow a new widget to meet the yet-to-be-defined noise specifications.
The input power filter for module power should be separate from the widget power supply input filter. The module power filter is a filter that will not meet all module requirements, but would likely meet the requirements of a digital module. Some modules, such as receivers, may need additional power conditioning. But in any case, the widget power supply should not add to the module power supply noise.
There should be a simple way to disconnect the filter capacitors on the widget from the data lines when the widget is in Byte mode. Most people are not aware of this problem which was uncovered by another module builder. It only effects those using the CAN-Do! in Byte mode.
Using a synchronizing signal does not seem practical to us. It would complicate the design of the widget power supply so that it would function with or without the presence of the synchronizing signal (we don't want to introduce a single-point-of-failure). It would dramatically increase the satellite wiring harness complexity, something the widget was intended to a simplify. And it would inhibit the widget power supply from going into various power-saving modes.
Recruit some new people into this project. Lyle simply doesn't have any time for doing new designs right now. We need a power supply designer as stated above. And my time is limited. I'm willing to lay out the new design and build a few prototypes, but I need others to do parts procurement and volume building of widgets. I'll prepare flight units if desired. We've talked about having someone skilled in parts procurement before but I don't know of anything having come of it. The bottom line, if this is going to happen, Lyle and I need others to be involved.
If you think this is a good idea, or bad, please express yourself. And if you have other comments to add to the above, or would like to modify/expand on above comments, please do so.
Looking forward to your comments,
Chuck and Lyle
Chuck, Lyle,
Good to hear from you. I'm excited to see a plan forming!
You probably expect this but I want to confirm... you have my support for the firmware, User's Guide authoring, control software development, etc.
Regards, Stephen --
On 7/9/07, Chuck Green greencl@mindspring.com wrote:
Hi Guys,
Juan has done a lot of outstanding work which resulted in some substantial critiquing of the CAN-Do! (Affectionately called a "widget.") It is unfortunate that it has taken several years since the CAN-Do! was designed and then 100 units built before an application of sufficient sensitivity used it to discover it's shortcomings. History can provide lessons that I hope we can learn from, but it seldom provides solutions to the problems encountered. Lyle and I have exchanged a few thoughts privately and it seems it may now be time to consider solutions to the problems found.
The only practical way to accomplish this is to develop the next generation CAN interface device. Dare I call it the CAN-Do-Too! ?
All technical specifications should remain the same. What this really means is that a next-generation controller must run *exactly* the same firmware currently running the CAN-Do! .
All specifications added or redefined should be carefully defined and be measurable.
General specifications that we worked from before were that the widget should use as little power as possible and consume as little of a module's volume as possible. The first of these should remain the same, "use as little power as possible."
But the second should be changed to "consume as little of the connector panel space as possible" even if it means consuming a little more of the module volume. This means the widget PCB and components should not extend beyond the dimensions of the DA-15P connector in either dimension. A possible compromise to this would be to let the PCB run past one end of the DA-15P but not more than the DA-15P is forced away from the side of the box by the box design.
The power supply could be completely redesigned. Or the inductor of the existing supply could be exchanged for one that is a toroid (the existing one is not). If someone wants to step up and design a new power supply, great! If not, then we would simply change the inductor. I'd sure like to see someone take this on. With so many of these in the satellite, only a few milliwatts is important. And the noise issue Juan uncovered is *very* important.
It may be that some, or maybe all, of the widget should be enclosed in a metal box. It may be that just changing the inductor would allow a new widget to meet the yet-to-be-defined noise specifications.
The input power filter for module power should be separate from the widget power supply input filter. The module power filter is a filter that will not meet all module requirements, but would likely meet the requirements of a digital module. Some modules, such as receivers, may need additional power conditioning. But in any case, the widget power supply should not add to the module power supply noise.
There should be a simple way to disconnect the filter capacitors on the widget from the data lines when the widget is in Byte mode. Most people are not aware of this problem which was uncovered by another module builder. It only effects those using the CAN-Do! in Byte mode.
Using a synchronizing signal does not seem practical to us. It would complicate the design of the widget power supply so that it would function with or without the presence of the synchronizing signal (we don't want to introduce a single-point-of-failure). It would dramatically increase the satellite wiring harness complexity, something the widget was intended to a simplify. And it would inhibit the widget power supply from going into various power-saving modes.
Recruit some new people into this project. Lyle simply doesn't have any time for doing new designs right now. We need a power supply designer as stated above. And my time is limited. I'm willing to lay out the new design and build a few prototypes, but I need others to do parts procurement and volume building of widgets. I'll prepare flight units if desired. We've talked about having someone skilled in parts procurement before but I don't know of anything having come of it. The bottom line, if this is going to happen, Lyle and I need others to be involved.
If you think this is a good idea, or bad, please express yourself. And if you have other comments to add to the above, or would like to modify/expand on above comments, please do so.
Looking forward to your comments,
Chuck and Lyle _______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Chuck and Lyle,
I'm in the process of writing up my presentation for the next AMSAT symposium so all of these issues have been on my mind constantly as I write.
I believe that any modification of the CAN-Do module should flow out of a comprehensive review of the top-level satellite requirements. There needs to be an EMI specification that covers radiated and conducted emissions and susceptibility for Eagle. Any need for changes to the CAN-Do module should flow directly from that EMI spec. An analysis of the requirements might show a need to break the module enclosure into two sections. If the module enclosure was changed to a two-section configuration, with all of the digital electronics in the front and the analog in the rear, then the RF would need to enter and exit out the side. If that were the case, I believe that the existing CAN-Do PCB size would be OK as currently configured. And of course, all of the above would directly impact the next revision of the receiver since it would determine the physical layout of the PCB as well as the size and configuration of any EMI filtering that was needed.
An analysis of the Eagle EMI requirements might also show that a move to a much higher switching frequency would be advised since it would ease the burden on filters and move any artifacts outside the passband of most analog payloads.
Bottom line - I would hold off making any hard decisions until a comprehensive EMI requirement for Eagle is created and analyzed.
73, Juan
If designing a new power supply is determined to be necessary then I would strongly suggest a move to as high a switching frequency as is practical. This will make filtering much easier.
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Monday, July 09, 2007 7:57 AM To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org; Bill Ress; Dave Black (Home); Dave Black (Work); Dave hartzell; David Smith; Don Ferguson; Juan.Rivera (Work); Samsonoff@Mac. Com Subject: CAN-Do-Too! ??????????
Hi Guys,
Juan has done a lot of outstanding work which resulted in some substantial critiquing of the CAN-Do! (Affectionately called a "widget.") It is unfortunate that it has taken several years since the CAN-Do! was designed and then 100 units built before an application of sufficient sensitivity used it to discover it's shortcomings. History can provide lessons that I hope we can learn from, but it seldom provides solutions to the problems encountered. Lyle and I have exchanged a few thoughts privately and it seems it may now be time to consider solutions to the problems found.
The only practical way to accomplish this is to develop the next generation CAN interface device. Dare I call it the CAN-Do-Too! ?
All technical specifications should remain the same. What this really means is that a next-generation controller must run *exactly* the same firmware currently running the CAN-Do! .
All specifications added or redefined should be carefully defined and be measurable.
General specifications that we worked from before were that the widget should use as little power as possible and consume as little of a module's volume as possible. The first of these should remain the same, "use as little power as possible."
But the second should be changed to "consume as little of the connector panel space as possible" even if it means consuming a little more of the module volume. This means the widget PCB and components should not extend beyond the dimensions of the DA-15P connector in either dimension. A possible compromise to this would be to let the PCB run past one end of the DA-15P but not more than the DA-15P is forced away from the side of the box by the box design.
The power supply could be completely redesigned. Or the inductor of the existing supply could be exchanged for one that is a toroid (the existing one is not). If someone wants to step up and design a new power supply, great! If not, then we would simply change the inductor. I'd sure like to see someone take this on. With so many of these in the satellite, only a few milliwatts is important. And the noise issue Juan uncovered is *very* important.
It may be that some, or maybe all, of the widget should be enclosed in a metal box. It may be that just changing the inductor would allow a new widget to meet the yet-to-be-defined noise specifications.
The input power filter for module power should be separate from the widget power supply input filter. The module power filter is a filter that will not meet all module requirements, but would likely meet the requirements of a digital module. Some modules, such as receivers, may need additional power conditioning. But in any case, the widget power supply should not add to the module power supply noise.
There should be a simple way to disconnect the filter capacitors on the widget from the data lines when the widget is in Byte mode. Most people are not aware of this problem which was uncovered by another module builder. It only effects those using the CAN-Do! in Byte mode.
Using a synchronizing signal does not seem practical to us. It would complicate the design of the widget power supply so that it would function with or without the presence of the synchronizing signal (we don't want to introduce a single-point-of-failure). It would dramatically increase the satellite wiring harness complexity, something the widget was intended to a simplify. And it would inhibit the widget power supply from going into various power-saving modes.
Recruit some new people into this project. Lyle simply doesn't have any time for doing new designs right now. We need a power supply designer as stated above. And my time is limited. I'm willing to lay out the new design and build a few prototypes, but I need others to do parts procurement and volume building of widgets. I'll prepare flight units if desired. We've talked about having someone skilled in parts procurement before but I don't know of anything having come of it. The bottom line, if this is going to happen, Lyle and I need others to be involved.
If you think this is a good idea, or bad, please express yourself. And if you have other comments to add to the above, or would like to modify/expand on above comments, please do so.
Looking forward to your comments,
Chuck and Lyle
All - -
To add support to Juan's conviction that we need to start developing "top down" specifications versus the bottom up activities we've been involved with, I would add that in order to develop a "realistic" EMI spec for the satellites power distribution system, we really need to know what those circuits will do.
With that in mind, I feel we need to breadboard the key circuits associated with that system and get hard data versus shooting from the hip with assumptions. At some point this power system is needed anyway, so why not focus design attention on that "top level" system now and get that issue settled - or at least better understood?
On the issue of housing panel area, and the possible consideration of a Mark 2 version, I think if I remember correctly, there were comments on wondering why a DB-9 (or even a physically smaller connector series) couldn't be used or are all the 15 pins needed?
Regards...Bill - N6GHz
Juan Rivera wrote:
Chuck and Lyle,
I'm in the process of writing up my presentation for the next AMSAT symposium so all of these issues have been on my mind constantly as I write.
I believe that any modification of the CAN-Do module should flow out of a comprehensive review of the top-level satellite requirements. There needs to be an EMI specification that covers radiated and conducted emissions and susceptibility for Eagle. Any need for changes to the CAN-Do module should flow directly from that EMI spec. An analysis of the requirements might show a need to break the module enclosure into two sections. If the module enclosure was changed to a two-section configuration, with all of the digital electronics in the front and the analog in the rear, then the RF would need to enter and exit out the side. If that were the case, I believe that the existing CAN-Do PCB size would be OK as currently configured. And of course, all of the above would directly impact the next revision of the receiver since it would determine the physical layout of the PCB as well as the size and configuration of any EMI filtering that was needed.
An analysis of the Eagle EMI requirements might also show that a move to a much higher switching frequency would be advised since it would ease the burden on filters and move any artifacts outside the passband of most analog payloads.
Bottom line - I would hold off making any hard decisions until a comprehensive EMI requirement for Eagle is created and analyzed.
73, Juan
If designing a new power supply is determined to be necessary then I would strongly suggest a move to as high a switching frequency as is practical. This will make filtering much easier.
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Monday, July 09, 2007 7:57 AM To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org; Bill Ress; Dave Black (Home); Dave Black (Work); Dave hartzell; David Smith; Don Ferguson; Juan.Rivera (Work); Samsonoff@Mac. Com Subject: CAN-Do-Too! ??????????
Hi Guys,
Juan has done a lot of outstanding work which resulted in some substantial critiquing of the CAN-Do! (Affectionately called a "widget.") It is unfortunate that it has taken several years since the CAN-Do! was designed and then 100 units built before an application of sufficient sensitivity used it to discover it's shortcomings. History can provide lessons that I hope we can learn from, but it seldom provides solutions to the problems encountered. Lyle and I have exchanged a few thoughts privately and it seems it may now be time to consider solutions to the problems found.
The only practical way to accomplish this is to develop the next generation CAN interface device. Dare I call it the CAN-Do-Too! ?
All technical specifications should remain the same. What this really means is that a next-generation controller must run *exactly* the same firmware currently running the CAN-Do! .
All specifications added or redefined should be carefully defined and be measurable.
General specifications that we worked from before were that the widget should use as little power as possible and consume as little of a module's volume as possible. The first of these should remain the same, "use as little power as possible."
But the second should be changed to "consume as little of the connector panel space as possible" even if it means consuming a little more of the module volume. This means the widget PCB and components should not extend beyond the dimensions of the DA-15P connector in either dimension. A possible compromise to this would be to let the PCB run past one end of the DA-15P but not more than the DA-15P is forced away from the side of the box by the box design.
The power supply could be completely redesigned. Or the inductor of the existing supply could be exchanged for one that is a toroid (the existing one is not). If someone wants to step up and design a new power supply, great! If not, then we would simply change the inductor. I'd sure like to see someone take this on. With so many of these in the satellite, only a few milliwatts is important. And the noise issue Juan uncovered is *very* important.
It may be that some, or maybe all, of the widget should be enclosed in a metal box. It may be that just changing the inductor would allow a new widget to meet the yet-to-be-defined noise specifications.
The input power filter for module power should be separate from the widget power supply input filter. The module power filter is a filter that will not meet all module requirements, but would likely meet the requirements of a digital module. Some modules, such as receivers, may need additional power conditioning. But in any case, the widget power supply should not add to the module power supply noise.
There should be a simple way to disconnect the filter capacitors on the widget from the data lines when the widget is in Byte mode. Most people are not aware of this problem which was uncovered by another module builder. It only effects those using the CAN-Do! in Byte mode.
Using a synchronizing signal does not seem practical to us. It would complicate the design of the widget power supply so that it would function with or without the presence of the synchronizing signal (we don't want to introduce a single-point-of-failure). It would dramatically increase the satellite wiring harness complexity, something the widget was intended to a simplify. And it would inhibit the widget power supply from going into various power-saving modes.
Recruit some new people into this project. Lyle simply doesn't have any time for doing new designs right now. We need a power supply designer as stated above. And my time is limited. I'm willing to lay out the new design and build a few prototypes, but I need others to do parts procurement and volume building of widgets. I'll prepare flight units if desired. We've talked about having someone skilled in parts procurement before but I don't know of anything having come of it. The bottom line, if this is going to happen, Lyle and I need others to be involved.
If you think this is a good idea, or bad, please express yourself. And if you have other comments to add to the above, or would like to modify/expand on above comments, please do so.
Looking forward to your comments,
Chuck and Lyle
Yes, we need a specification for the DC power bus before approval of the requirements for the next U-band receiver. I've got the DC voltage in there, but there needs to be a specification for conducted EMI.
73,
John KD6OZH
----- Original Message ----- From: "Bill Ress" bill@hsmicrowave.com To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org; "Juan.Rivera (Work)" Juan.Rivera@gd-ais.com Sent: Monday, July 09, 2007 17:29 UTC Subject: [eagle] Re: CAN-Do-Too! ??????????
All - -
To add support to Juan's conviction that we need to start developing "top down" specifications versus the bottom up activities we've been involved with, I would add that in order to develop a "realistic" EMI spec for the satellites power distribution system, we really need to know what those circuits will do.
With that in mind, I feel we need to breadboard the key circuits associated with that system and get hard data versus shooting from the hip with assumptions. At some point this power system is needed anyway, so why not focus design attention on that "top level" system now and get that issue settled - or at least better understood?
On the issue of housing panel area, and the possible consideration of a Mark 2 version, I think if I remember correctly, there were comments on wondering why a DB-9 (or even a physically smaller connector series) couldn't be used or are all the 15 pins needed?
Regards...Bill - N6GHz
Juan Rivera wrote:
Chuck and Lyle,
I'm in the process of writing up my presentation for the next AMSAT symposium so all of these issues have been on my mind constantly as I write.
I believe that any modification of the CAN-Do module should flow out of a comprehensive review of the top-level satellite requirements. There needs to be an EMI specification that covers radiated and conducted emissions and susceptibility for Eagle. Any need for changes to the CAN-Do module should flow directly from that EMI spec. An analysis of the requirements might show a need to break the module enclosure into two sections. If the module enclosure was changed to a two-section configuration, with all of the digital electronics in the front and the analog in the rear, then the RF would need to enter and exit out the side. If that were the case, I believe that the existing CAN-Do PCB size would be OK as currently configured. And of course, all of the above would directly impact the next revision of the receiver since it would determine the physical layout of the PCB as well as the size and configuration of any EMI filtering that was needed.
An analysis of the Eagle EMI requirements might also show that a move to a much higher switching frequency would be advised since it would ease the burden on filters and move any artifacts outside the passband of most analog payloads.
Bottom line - I would hold off making any hard decisions until a comprehensive EMI requirement for Eagle is created and analyzed.
73, Juan
If designing a new power supply is determined to be necessary then I would strongly suggest a move to as high a switching frequency as is practical. This will make filtering much easier.
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Monday, July 09, 2007 7:57 AM To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org; Bill Ress; Dave Black (Home); Dave Black (Work); Dave hartzell; David Smith; Don Ferguson; Juan.Rivera (Work); Samsonoff@Mac. Com Subject: CAN-Do-Too! ??????????
Hi Guys,
Juan has done a lot of outstanding work which resulted in some substantial critiquing of the CAN-Do! (Affectionately called a "widget.") It is unfortunate that it has taken several years since the CAN-Do! was designed and then 100 units built before an application of sufficient sensitivity used it to discover it's shortcomings. History can provide lessons that I hope we can learn from, but it seldom provides solutions to the problems encountered. Lyle and I have exchanged a few thoughts privately and it seems it may now be time to consider solutions to the problems found.
The only practical way to accomplish this is to develop the next generation CAN interface device. Dare I call it the CAN-Do-Too! ?
All technical specifications should remain the same. What this really means is that a next-generation controller must run *exactly* the same firmware currently running the CAN-Do! .
All specifications added or redefined should be carefully defined and be measurable.
General specifications that we worked from before were that the widget should use as little power as possible and consume as little of a module's volume as possible. The first of these should remain the same, "use as little power as possible."
But the second should be changed to "consume as little of the connector panel space as possible" even if it means consuming a little more of the module volume. This means the widget PCB and components should not extend beyond the dimensions of the DA-15P connector in either dimension. A possible compromise to this would be to let the PCB run past one end of the DA-15P but not more than the DA-15P is forced away from the side of the box by the box design.
The power supply could be completely redesigned. Or the inductor of the existing supply could be exchanged for one that is a toroid (the existing one is not). If someone wants to step up and design a new power supply, great! If not, then we would simply change the inductor. I'd sure like to see someone take this on. With so many of these in the satellite, only a few milliwatts is important. And the noise issue Juan uncovered is *very* important.
It may be that some, or maybe all, of the widget should be enclosed in a metal box. It may be that just changing the inductor would allow a new widget to meet the yet-to-be-defined noise specifications.
The input power filter for module power should be separate from the widget power supply input filter. The module power filter is a filter that will not meet all module requirements, but would likely meet the requirements of a digital module. Some modules, such as receivers, may need additional power conditioning. But in any case, the widget power supply should not add to the module power supply noise.
There should be a simple way to disconnect the filter capacitors on the widget from the data lines when the widget is in Byte mode. Most people are not aware of this problem which was uncovered by another module builder. It only effects those using the CAN-Do! in Byte mode.
Using a synchronizing signal does not seem practical to us. It would complicate the design of the widget power supply so that it would function with or without the presence of the synchronizing signal (we don't want to introduce a single-point-of-failure). It would dramatically increase the satellite wiring harness complexity, something the widget was intended to a simplify. And it would inhibit the widget power supply from going into various power-saving modes.
Recruit some new people into this project. Lyle simply doesn't have any time for doing new designs right now. We need a power supply designer as stated above. And my time is limited. I'm willing to lay out the new design and build a few prototypes, but I need others to do parts procurement and volume building of widgets. I'll prepare flight units if desired. We've talked about having someone skilled in parts procurement before but I don't know of anything having come of it. The bottom line, if this is going to happen, Lyle and I need others to be involved.
If you think this is a good idea, or bad, please express yourself. And if you have other comments to add to the above, or would like to modify/expand on above comments, please do so.
Looking forward to your comments,
Chuck and Lyle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
All,
This last flurry of email is gratifying! I've been working on my presentation for the AMSAT symposium so my mind has been going over the entire receiver design/construction/test process step by step for the last week or two. I really think the focus has to shift away from the receiver until these top-level questions have all been answered.
EMI will directly impact both the ultimate design of the CAN-Do module and the enclosure. They need to be looked at as one subsystem. That subsystem needs to be held up against the most sensitive analog circuitry anticipated. Then you can start looking at tradeoffs between the enclosure, the CAN-DO radiated and conducted emissions, and the EMI susceptibility of the analog circuitry that will have to operate in that environment.
Isn't this fun?
73, Juan
-----Original Message----- From: John B. Stephensen [mailto:kd6ozh@comcast.net] Sent: Monday, July 09, 2007 11:14 AM To: Bill Ress; juan-rivera@sbcglobal.net Cc: eagle@amsat.org; Juan.Rivera (Work) Subject: Re: [eagle] Re: CAN-Do-Too! ??????????
Yes, we need a specification for the DC power bus before approval of the requirements for the next U-band receiver. I've got the DC voltage in there,
but there needs to be a specification for conducted EMI.
73,
John KD6OZH
----- Original Message ----- From: "Bill Ress" bill@hsmicrowave.com To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org; "Juan.Rivera (Work)" Juan.Rivera@gd-ais.com Sent: Monday, July 09, 2007 17:29 UTC Subject: [eagle] Re: CAN-Do-Too! ??????????
All - -
To add support to Juan's conviction that we need to start developing "top down" specifications versus the bottom up activities we've been involved with, I would add that in order to develop a "realistic" EMI spec for the satellites power distribution system, we really need to know what those circuits will do.
With that in mind, I feel we need to breadboard the key circuits associated with that system and get hard data versus shooting from the hip with assumptions. At some point this power system is needed anyway, so why not focus design attention on that "top level" system now and get that issue settled - or at least better understood?
On the issue of housing panel area, and the possible consideration of a Mark 2 version, I think if I remember correctly, there were comments on wondering why a DB-9 (or even a physically smaller connector series) couldn't be used or are all the 15 pins needed?
Regards...Bill - N6GHz
Juan Rivera wrote:
Chuck and Lyle,
I'm in the process of writing up my presentation for the next AMSAT symposium so all of these issues have been on my mind constantly as I write.
I believe that any modification of the CAN-Do module should flow out of a comprehensive review of the top-level satellite requirements. There needs to be an EMI specification that covers radiated and conducted emissions and susceptibility for Eagle. Any need for changes to the CAN-Do module should flow directly from that EMI spec. An analysis of the requirements might show a need to break the module enclosure into two sections. If the module enclosure was changed to a two-section configuration, with all of the digital electronics in the front and the analog in the rear, then the RF would need to enter and exit out the side. If that were the case, I believe that the existing CAN-Do PCB size would be OK as currently configured. And of course, all of the above would directly impact the next revision of the receiver since it would determine the physical layout of the PCB as well as the size and configuration of any EMI filtering that was needed.
An analysis of the Eagle EMI requirements might also show that a move to a much higher switching frequency would be advised since it would ease the burden on filters and move any artifacts outside the passband of most analog payloads.
Bottom line - I would hold off making any hard decisions until a comprehensive EMI requirement for Eagle is created and analyzed.
73, Juan
If designing a new power supply is determined to be necessary then I would strongly suggest a move to as high a switching frequency as is practical. This will make filtering much easier.
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Monday, July 09, 2007 7:57 AM To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org; Bill Ress; Dave Black (Home); Dave Black (Work); Dave hartzell; David Smith; Don Ferguson; Juan.Rivera (Work); Samsonoff@Mac. Com Subject: CAN-Do-Too! ??????????
Hi Guys,
Juan has done a lot of outstanding work which resulted in some substantial critiquing of the CAN-Do! (Affectionately called a "widget.") It is unfortunate that it has taken several years since the CAN-Do! was designed and then 100 units built before an application of sufficient sensitivity used it to discover it's shortcomings. History can provide lessons that I hope we can learn from, but it seldom provides solutions to the problems encountered. Lyle and I have exchanged a few thoughts privately and it seems it may now be time to consider solutions to the problems found.
The only practical way to accomplish this is to develop the next generation CAN interface device. Dare I call it the CAN-Do-Too! ?
All technical specifications should remain the same. What this really means is that a next-generation controller must run *exactly* the same firmware currently running the CAN-Do! .
All specifications added or redefined should be carefully defined and be measurable.
General specifications that we worked from before were that the widget should use as little power as possible and consume as little of a module's volume as possible. The first of these should remain the same, "use as little power as possible."
But the second should be changed to "consume as little of the connector panel space as possible" even if it means consuming a little more of the module volume. This means the widget PCB and components should not extend beyond the dimensions of the DA-15P connector in either dimension. A possible compromise to this would be to let the PCB run past one end of the DA-15P but not more than the DA-15P is forced away from the side of the box by the box design.
The power supply could be completely redesigned. Or the inductor of the existing supply could be exchanged for one that is a toroid (the existing one is not). If someone wants to step up and design a new power supply, great! If not, then we would simply change the inductor. I'd sure like to see someone take this on. With so many of these in the satellite, only a few milliwatts is important. And the noise issue Juan uncovered is *very* important.
It may be that some, or maybe all, of the widget should be enclosed in a metal box. It may be that just changing the inductor would allow a new widget to meet the yet-to-be-defined noise specifications.
The input power filter for module power should be separate from the widget power supply input filter. The module power filter is a filter that will not meet all module requirements, but would likely meet the requirements of a digital module. Some modules, such as receivers, may need additional power conditioning. But in any case, the widget power supply should not add to the module power supply noise.
There should be a simple way to disconnect the filter capacitors on the widget from the data lines when the widget is in Byte mode. Most people are not aware of this problem which was uncovered by another module builder. It only effects those using the CAN-Do! in Byte mode.
Using a synchronizing signal does not seem practical to us. It would complicate the design of the widget power supply so that it would function with or without the presence of the synchronizing signal (we don't want to introduce a single-point-of-failure). It would dramatically increase the satellite wiring harness complexity, something the widget was intended to a simplify. And it would inhibit the widget power supply from going into various power-saving modes.
Recruit some new people into this project. Lyle simply doesn't have any time for doing new designs right now. We need a power supply designer as stated above. And my time is limited. I'm willing to lay out the new design and build a few prototypes, but I need others to do parts procurement and volume building of widgets. I'll prepare flight units if desired. We've talked about having someone skilled in parts procurement before but I don't know of anything having come of it. The bottom line, if this is going to happen, Lyle and I need others to be involved.
If you think this is a good idea, or bad, please express yourself. And if you have other comments to add to the above, or would like to modify/expand on above comments, please do so.
Looking forward to your comments,
Chuck and Lyle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Bill Ress wrote:
All - -
To add support to Juan's conviction that we need to start developing "top down" specifications versus the bottom up activities we've been involved with, I would add that in order to develop a "realistic" EMI spec for the satellites power distribution system, we really need to know what those circuits will do.
With that in mind, I feel we need to breadboard the key circuits associated with that system and get hard data versus shooting from the hip with assumptions. At some point this power system is needed anyway, so why not focus design attention on that "top level" system now and get that issue settled - or at least better understood?
On the issue of housing panel area, and the possible consideration of a Mark 2 version, I think if I remember correctly, there were comments on wondering why a DB-9 (or even a physically smaller connector series) couldn't be used or are all the 15 pins needed?
Regards...Bill - N6GHz
I also support the breadboarding of primary circuits. And we did develop our specifications for the latest incarnation of Eagle top down. We started with what services we wanted to deliver and moved down from there.
When I rejoined the project, and started the software defined transponder movement, and long before I was leadership, the Can-Do was "in the can". I had almost no input to it. That said, I really do support the goal of the CanDo. Anyone who has heard of the horror stories of Marie Marr and the wiring harness or seen Lou's spreadsheet for interconnections for AO-40 knows that these few words do not do it justice. We have found a gremlin. That is normal in any project of this complexity and is not easily remedied by specifications in a project like this where the work and the tools necessary to make the relevant measurements are spread over the globe.
I look forward to our doing better as a team.
Bob
All: I'm excited to read all of the emails on this topic. Several thoughts, which I'd really like to discuss in more detail with all of you tomorrow night on TeamSpeak. 1. As an experiment, and data collection exercise, I'd like to see the inductor Juan identified as the source of radiated EMI replaced with a shielded inductor or toroid. As I mentioned to some of you, I saw a similar noise problem (source & victim were reversed) in my day job solved with exactly that one change. I think this would tell us much about how big a problem we have (radiated and conducted), and be a useful piece of data for posterity. As Bdale said almost two years ago, "Our legacy may very well be our documentation."
2. Second, I'd like to see if we can, with a few ccomponent changes on the existing widget board change the switching power supply frequency as Juan suggested. Another useful data point, with minimal effort.
Request for action: Can one of Chuck, Lyle, Stephen, or Bdale take on obtaining a shielded/toroidal inductor of the same value and provide to Juan for testing, and then take on researching a change to the switching PS frequency? IF so, Juan, would you and your team please make the changes and repeat testing?
3. Regarding Chuck's comment: If we wind up with Can-Do Too, I'd ask Juan if his accomplished project oscar team could take on component selection/purchase and construction of a couple of prototypes? This could happen in parallel with John's redesign of the U-band receiver. I know you guys have done a lot, but, YOU"RE GOOD!
4. EMI Spec: You put a gun to my head, and I'm going to pull out the MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable. In general, I'd like to eliminate as much mass and extra "touch" labor in the assembly process (multiple shields) as possible. Bob Davis: Please weigh in here, if the possible milled modules simplify this issue, please enlighten us.
5. Chuck: I appreciate your comments on lessons learned. You obviously have some things in mind, please scribble them down, get them to me, and I'll get placed on the EaglePedia lessons learned page.
6. CAN-Do! team: Several folks have opined to me that it appears that the widget design is final, complete, and we'd better live with it. I'd intended to discuss some of the above with you when Bdale got back. I am EXTREMELY PLEASED AND GRATEFUL to see you stepping up to the plate and acknowledging the need and willingness to do something based on what Juan has learned. Your intellectual honesty, integrity, and willingness to take on more for the team are recognized and appreciated.
7. Requirements: Bob McGwier is correct, we really did start with a very top-level requirements document. It is not perfect (Bob has hated it from the word go), but can be found on EaglePedia under Functional Requirements. It is also in need of updating, after the October BoD decision. On my list to do. Like you, I have finite energy and time, but it is on my list. I think John did an EXCELLENT job of documenting the UHF Receiver requirements based on what he knew. The need for an EMI spec was not obvious, but is now, thanks to Juan's testing efforts and exceptional documentation. Lou: Functional requirements for power supplies? Bob Davis: Functional requirements for structure and thermal performance? etc. etc.....we have much to do, but I think worthwhile effort. By the way, I'm reading (in a few spare minutes here and there) an EXCELLENT book on requirements management. When I finish, look for a review of it on my project management page. I will also be providing suggestions on writing "good" requirements, based on that book and my recent experiences in the day job.
8. Somebody brought up the issue of CAN bus vs. discrete wiring harness. In my mind, the discrete harness is a non-starter. WAY too much room for error and difficulty in testing. Yeah, I know the AO-40 harness was perfect the first time, but the guys who made that happen have made it clear to me that they don't ever want to do it again -- and I agree. So, I think we should remain committed to the CAN bus for many reasons. In my view, the recent "issues" with the CAN-Do! widget are just issues to deal with, not show stoppers. The CAN-Do! team is willing to deal with the issues, and so should the rest of us. Case closed in my mind. As always, open to well-justified better idea, but I think the writing remains on the wall.
I'm sure there's more action following this recent discussion, but specifics currently elude me. Feel free to send me suggestions, update the agenda for tomorrow night's TeamSpeak, and please be there.
Thank you all. Very 73, Jim wb4gcs@amsat.org
Robert McGwier wrote:
Bill Ress wrote:
All - -
To add support to Juan's conviction that we need to start developing "top down" specifications versus the bottom up activities we've been involved with, I would add that in order to develop a "realistic" EMI spec for the satellites power distribution system, we really need to know what those circuits will do.
With that in mind, I feel we need to breadboard the key circuits associated with that system and get hard data versus shooting from the hip with assumptions. At some point this power system is needed anyway, so why not focus design attention on that "top level" system now and get that issue settled - or at least better understood?
On the issue of housing panel area, and the possible consideration of a Mark 2 version, I think if I remember correctly, there were comments on wondering why a DB-9 (or even a physically smaller connector series) couldn't be used or are all the 15 pins needed?
Regards...Bill - N6GHz
I also support the breadboarding of primary circuits. And we did develop our specifications for the latest incarnation of Eagle top down. We started with what services we wanted to deliver and moved down from there.
When I rejoined the project, and started the software defined transponder movement, and long before I was leadership, the Can-Do was "in the can". I had almost no input to it. That said, I really do support the goal of the CanDo. Anyone who has heard of the horror stories of Marie Marr and the wiring harness or seen Lou's spreadsheet for interconnections for AO-40 knows that these few words do not do it justice. We have found a gremlin. That is normal in any project of this complexity and is not easily remedied by specifications in a project like this where the work and the tools necessary to make the relevant measurements are spread over the globe.
I look forward to our doing better as a team.
Bob
Jim Sanford wrote:
- EMI Spec: You put a gun to my head, and I'm going to pull out the
MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable. In general, I'd like to eliminate as much mass and extra "touch" labor in the assembly process (multiple shields) as possible. Bob Davis: Please weigh in here, if the possible milled modules simplify this issue, please enlighten us.
Jim, I think an EMI spec pulled out of a MIL-STD would be an over kill effort and likely not representative of "our" real world. What we need is not assumptions but data reflecting what the hardware does. The problem is that we don't have the hardware - and that's my issue. The power distribution circuits are what I call a "top level" subsystem which feeds "everyone." Instead of working on the circuitry that will run from it and trying to "imagine" what we can expect, let's focus on breadboarding the key power distribution circuits and get some hard data so we know what we're working with.
I'll again reiterate (as I have several times in the past) the same thing for the satellite's 10 MHz reference. It's another top level "subsystem" that will feed "all" LO's. Instead of guessing what we'll be working with, let's get it defined too.
(I'm proposing we put that one to bed and use the time tested, well defined, high stability, low noise HP (OK - Agilent) 10811 series of reference standards used in most of their test instruments. If that won't cut it - someone please tell me why!)
- Requirements: Bob McGwier is correct, we really did start with a
very top-level requirements document. It is not perfect (Bob has hated it from the word go), but can be found on EaglePedia under Functional Requirements. It is also in need of updating, after the October BoD decision. On my list to do. Like you, I have finite energy and time, but it is on my list. I think John did an EXCELLENT job of documenting the UHF Receiver requirements based on what he knew. The need for an EMI spec was not obvious, but is now, thanks to Juan's testing efforts and exceptional documentation. Lou: Functional requirements for power supplies? Bob Davis: Functional requirements for structure and thermal performance? etc. etc.....we have much to do, but I think worthwhile effort. By the way, I'm reading (in a few spare minutes here and there) an EXCELLENT book on requirements management. When I finish, look for a review of it on my project management page. I will also be providing suggestions on writing "good" requirements, based on that book and my recent experiences in the day job.
Yes, we have "top level requirements" for desired satellite functions, operating modes and parameters and link budgets. But again, I think we're sorely lacking in key "system" performance requirements based on real data - - - which can only be obtained by building and testing these key functions.
I'm not a power supply guy, but I'll offer to assist in building and testing the circuits we need to characterize. Lou - point me in the right direction - tell me what you need!
Regards...Bill - N6GHz
Bill: Thanks.
I'm exhausted. More detailed response tomorrow. YOu make good points, we need to decide how to proceed.
Thanks & 73, Jim wb4gcs@amsat.org
Bill Ress wrote:
Jim Sanford wrote:
- EMI Spec: You put a gun to my head, and I'm going to pull out
the MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable. In general, I'd like to eliminate as much mass and extra "touch" labor in the assembly process (multiple shields) as possible. Bob Davis: Please weigh in here, if the possible milled modules simplify this issue, please enlighten us.
Jim, I think an EMI spec pulled out of a MIL-STD would be an over kill effort and likely not representative of "our" real world. What we need is not assumptions but data reflecting what the hardware does. The problem is that we don't have the hardware - and that's my issue. The power distribution circuits are what I call a "top level" subsystem which feeds "everyone." Instead of working on the circuitry that will run from it and trying to "imagine" what we can expect, let's focus on breadboarding the key power distribution circuits and get some hard data so we know what we're working with.
I'll again reiterate (as I have several times in the past) the same thing for the satellite's 10 MHz reference. It's another top level "subsystem" that will feed "all" LO's. Instead of guessing what we'll be working with, let's get it defined too.
(I'm proposing we put that one to bed and use the time tested, well defined, high stability, low noise HP (OK - Agilent) 10811 series of reference standards used in most of their test instruments. If that won't cut it - someone please tell me why!)
- Requirements: Bob McGwier is correct, we really did start with a
very top-level requirements document. It is not perfect (Bob has hated it from the word go), but can be found on EaglePedia under Functional Requirements. It is also in need of updating, after the October BoD decision. On my list to do. Like you, I have finite energy and time, but it is on my list. I think John did an EXCELLENT job of documenting the UHF Receiver requirements based on what he knew. The need for an EMI spec was not obvious, but is now, thanks to Juan's testing efforts and exceptional documentation. Lou: Functional requirements for power supplies? Bob Davis: Functional requirements for structure and thermal performance? etc. etc.....we have much to do, but I think worthwhile effort. By the way, I'm reading (in a few spare minutes here and there) an EXCELLENT book on requirements management. When I finish, look for a review of it on my project management page. I will also be providing suggestions on writing "good" requirements, based on that book and my recent experiences in the day job.
Yes, we have "top level requirements" for desired satellite functions, operating modes and parameters and link budgets. But again, I think we're sorely lacking in key "system" performance requirements based on real data - - - which can only be obtained by building and testing these key functions.
I'm not a power supply guy, but I'll offer to assist in building and testing the circuits we need to characterize. Lou - point me in the right direction - tell me what you need!
Regards...Bill - N6GHz
Jim,
I concur completely with Bill,
I beg you, don't open that MIL spec! Abandon all hope ye who enter there! There are actually two specs. One is how to test and the other is what the government wants to see for EMI shielding on tanks, ships, aircraft, etc. They're both impractical for our purposes.
What is does offer is a method of describing EMI so we can all discuss it. They break it down into 4 categories':
Conducted Emissions Radiated emissions Conducted susceptibility Radiated susceptibility
I agree with Bill. Guessing about something as universal as the quality of the primary power is not a good way to start. We need to characterize "noise" from the perspective of the power distribution point. The amplitude and spectral distribution of the conducted EMI coming out of there is a critical item. The same goes for the switched power from the CAN-Do module. Those two sources of noise will impact everything on the spacecraft.
That leaves radiated emissions and susceptibility to nail down. This is where it impacts the module chassis directly. Can we get by with one compartment with digital and analog circuitry together? This is generally considered a very bad design practice. But we'll only be able to tell after testing, and then it may only apply to the 70 cm Receiver so we have to be careful. Some effort should be expended identifying other payloads that may have EMI susceptibility issues - receivers, magnetometers, etc...
I think this is a good example of the phase, "measure twice and cut once". If the requirements are unrealistic you'll find out very late in the integration phase when there is no time to fix anything.
Lastly, we need to be able to generate a realistic noisy power source for testing. It needs to be capable of being duplicated so we can have multiple units for each team to use. Once we have a realistic noise source then we can come up with a series of tests to determine if the unit meets the specs.
73,
Juan
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Bill Ress Sent: Monday, July 09, 2007 7:34 PM To: Jim Sanford Cc: eagle@amsat.org Subject: [eagle] Re: CAN-Do-Too! ??????????
Jim Sanford wrote:
- EMI Spec: You put a gun to my head, and I'm going to pull out the
MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable. In general, I'd like to eliminate as much mass and extra "touch" labor in the assembly process (multiple shields) as possible. Bob Davis: Please weigh in here, if the possible milled modules simplify this issue, please enlighten us.
Jim, I think an EMI spec pulled out of a MIL-STD would be an over kill effort and likely not representative of "our" real world. What we need is not assumptions but data reflecting what the hardware does. The problem is that we don't have the hardware - and that's my issue. The power distribution circuits are what I call a "top level" subsystem which feeds "everyone." Instead of working on the circuitry that will run from it and trying to "imagine" what we can expect, let's focus on breadboarding the key power distribution circuits and get some hard data so we know what we're working with.
I'll again reiterate (as I have several times in the past) the same thing for the satellite's 10 MHz reference. It's another top level "subsystem" that will feed "all" LO's. Instead of guessing what we'll be working with, let's get it defined too.
(I'm proposing we put that one to bed and use the time tested, well defined, high stability, low noise HP (OK - Agilent) 10811 series of reference standards used in most of their test instruments. If that won't cut it - someone please tell me why!)
- Requirements: Bob McGwier is correct, we really did start with a
very top-level requirements document. It is not perfect (Bob has hated it from the word go), but can be found on EaglePedia under Functional Requirements. It is also in need of updating, after the October BoD decision. On my list to do. Like you, I have finite energy and time, but it is on my list. I think John did an EXCELLENT job of documenting the UHF Receiver requirements based on what he knew. The need for an EMI spec was not obvious, but is now, thanks to Juan's testing efforts and exceptional documentation. Lou: Functional requirements for power supplies? Bob Davis: Functional requirements for structure and thermal performance? etc. etc.....we have much to do, but I think worthwhile effort. By the way, I'm reading (in a few spare minutes here and there) an EXCELLENT book on requirements management. When I finish, look for a review of it on my project management page. I will also be providing suggestions on writing "good" requirements, based on that book and my recent experiences in the day job.
Yes, we have "top level requirements" for desired satellite functions, operating modes and parameters and link budgets. But again, I think we're sorely lacking in key "system" performance requirements based on real data - - - which can only be obtained by building and testing these key functions.
I'm not a power supply guy, but I'll offer to assist in building and testing the circuits we need to characterize. Lou - point me in the right direction - tell me what you need!
Regards...Bill - N6GHz
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Jim wrote:
- EMI Spec: You put a gun to my head, and I'm going to pull out the
MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable.
I specified several power supplies when I worked for HP/Agilent. I found it really hard to come up with system-level noise specifications in instruments for the same reasons as in the Eagle project. The problem is that it's a complicated multi-dimensional problem.
Dimension 1: Emissions (power supply) vs susceptibility (modules) Dimension 2: Radiated vs conducted emissions Dimension 3: Interference path: Radiated: - Magnetic (inductive) vs electric (capacitive) coupling Conducted: - Power supply bus vs signal lines vs ground loops - Voltage (open circuit) vs current (short circuit) specification Dimension 4: Emissions level versus frequency (audio to microwave) Dimension 5: Broadband vs narrowband interference (Some circuits are more susceptible to sine-wave interference, some to pulse-type interference, some to broadband noise.)
If you specified every box in the N-dimensional matrix you would have hundreds of specifications.
Add to that the fact that the power supply must be specified before the subassemblies are designed/built/tested and vice versa, and it becomes an almost intractable problem.
The military's solution is to specify all power supplies and subassemblies for the worst-possible situation you can imagine. While that does improve the probability of success, it still is not perfect and is very expensive.
On the projects I worked on, we basically just specified the power supply as good as reasonably practicable using standard shielding and filtering techniques and then did whatever was needed in the various subassemblies to make the instrument meet specifications.
One point to pay attention to is ground loops. Ideally there would be a single-point ground in the spacecraft (probably in the main power supply). The idea is that each assembly's ground return connects only with a separate wire to the single-point ground.
It's not practical to do that 100% (think of the Can-Do power bus for example) but any module that can draw large current transients from the power supply should probably have separate power and ground wires that connect directly to the power supply. Also, any sensitive modules should not have any additional ground returns on the module side of their power supply filters. (That is, the ground return should go through the on-board filter.)
Al N1AL
On Mon, 2007-07-09 at 18:30, Jim Sanford wrote:
All: I'm excited to read all of the emails on this topic. Several thoughts, which I'd really like to discuss in more detail with all of you tomorrow night on TeamSpeak.
- As an experiment, and data collection exercise, I'd like to see
the inductor Juan identified as the source of radiated EMI replaced with a shielded inductor or toroid. As I mentioned to some of you, I saw a similar noise problem (source & victim were reversed) in my day job solved with exactly that one change. I think this would tell us much about how big a problem we have (radiated and conducted), and be a useful piece of data for posterity. As Bdale said almost two years ago, "Our legacy may very well be our documentation."
- Second, I'd like to see if we can, with a few ccomponent changes
on the existing widget board change the switching power supply frequency as Juan suggested. Another useful data point, with minimal effort.
Request for action: Can one of Chuck, Lyle, Stephen, or Bdale take on obtaining a shielded/toroidal inductor of the same value and provide to Juan for testing, and then take on researching a change to the switching PS frequency? IF so, Juan, would you and your team please make the changes and repeat testing?
- Regarding Chuck's comment: If we wind up with Can-Do Too, I'd ask
Juan if his accomplished project oscar team could take on component selection/purchase and construction of a couple of prototypes? This could happen in parallel with John's redesign of the U-band receiver. I know you guys have done a lot, but, YOU"RE GOOD!
- EMI Spec: You put a gun to my head, and I'm going to pull out the
MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable. In general, I'd like to eliminate as much mass and extra "touch" labor in the assembly process (multiple shields) as possible. Bob Davis: Please weigh in here, if the possible milled modules simplify this issue, please enlighten us.
- Chuck: I appreciate your comments on lessons learned. You
obviously have some things in mind, please scribble them down, get them to me, and I'll get placed on the EaglePedia lessons learned page.
- CAN-Do! team: Several folks have opined to me that it appears
that the widget design is final, complete, and we'd better live with it. I'd intended to discuss some of the above with you when Bdale got back. I am EXTREMELY PLEASED AND GRATEFUL to see you stepping up to the plate and acknowledging the need and willingness to do something based on what Juan has learned. Your intellectual honesty, integrity, and willingness to take on more for the team are recognized and appreciated.
- Requirements: Bob McGwier is correct, we really did start with a
very top-level requirements document. It is not perfect (Bob has hated it from the word go), but can be found on EaglePedia under Functional Requirements. It is also in need of updating, after the October BoD decision. On my list to do. Like you, I have finite energy and time, but it is on my list. I think John did an EXCELLENT job of documenting the UHF Receiver requirements based on what he knew. The need for an EMI spec was not obvious, but is now, thanks to Juan's testing efforts and exceptional documentation. Lou: Functional requirements for power supplies? Bob Davis: Functional requirements for structure and thermal performance? etc. etc.....we have much to do, but I think worthwhile effort. By the way, I'm reading (in a few spare minutes here and there) an EXCELLENT book on requirements management. When I finish, look for a review of it on my project management page. I will also be providing suggestions on writing "good" requirements, based on that book and my recent experiences in the day job.
- Somebody brought up the issue of CAN bus vs. discrete wiring
harness. In my mind, the discrete harness is a non-starter. WAY too much room for error and difficulty in testing. Yeah, I know the AO-40 harness was perfect the first time, but the guys who made that happen have made it clear to me that they don't ever want to do it again -- and I agree. So, I think we should remain committed to the CAN bus for many reasons. In my view, the recent "issues" with the CAN-Do! widget are just issues to deal with, not show stoppers. The CAN-Do! team is willing to deal with the issues, and so should the rest of us. Case closed in my mind. As always, open to well-justified better idea, but I think the writing remains on the wall.
I'm sure there's more action following this recent discussion, but specifics currently elude me. Feel free to send me suggestions, update the agenda for tomorrow night's TeamSpeak, and please be there.
Thank you all. Very 73, Jim wb4gcs@amsat.org
Robert McGwier wrote:
Bill Ress wrote:
All - -
To add support to Juan's conviction that we need to start developing "top down" specifications versus the bottom up activities we've been involved with, I would add that in order to develop a "realistic" EMI spec for the satellites power distribution system, we really need to know what those circuits will do.
With that in mind, I feel we need to breadboard the key circuits associated with that system and get hard data versus shooting from the hip with assumptions. At some point this power system is needed anyway, so why not focus design attention on that "top level" system now and get that issue settled - or at least better understood?
On the issue of housing panel area, and the possible consideration of a Mark 2 version, I think if I remember correctly, there were comments on wondering why a DB-9 (or even a physically smaller connector series) couldn't be used or are all the 15 pins needed?
Regards...Bill - N6GHz
I also support the breadboarding of primary circuits. And we did develop our specifications for the latest incarnation of Eagle top down. We started with what services we wanted to deliver and moved down from there.
When I rejoined the project, and started the software defined transponder movement, and long before I was leadership, the Can-Do was "in the can". I had almost no input to it. That said, I really do support the goal of the CanDo. Anyone who has heard of the horror stories of Marie Marr and the wiring harness or seen Lou's spreadsheet for interconnections for AO-40 knows that these few words do not do it justice. We have found a gremlin. That is normal in any project of this complexity and is not easily remedied by specifications in a project like this where the work and the tools necessary to make the relevant measurements are spread over the globe.
I look forward to our doing better as a team.
Bob
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Designing for the worst case probably makes sense for Eagle. The number of units being built is tiny so component cost for the electronics is not a big issue. The big issue is weight.
73,
John KD6OZH
----- Original Message ----- From: "Alan Bloom" n1al@cds1.net To: eagle@amsat.org Cc: eaglesensor@vom.com Sent: Tuesday, July 10, 2007 06:37 UTC Subject: [eagle] Re: CAN-Do-Too! ??????????
Jim wrote:
- EMI Spec: You put a gun to my head, and I'm going to pull out the
MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable.
I specified several power supplies when I worked for HP/Agilent. I found it really hard to come up with system-level noise specifications in instruments for the same reasons as in the Eagle project. The problem is that it's a complicated multi-dimensional problem.
Dimension 1: Emissions (power supply) vs susceptibility (modules) Dimension 2: Radiated vs conducted emissions Dimension 3: Interference path: Radiated:
- Magnetic (inductive) vs electric (capacitive) coupling
Conducted:
- Power supply bus vs signal lines vs ground loops
- Voltage (open circuit) vs current (short circuit) specification
Dimension 4: Emissions level versus frequency (audio to microwave) Dimension 5: Broadband vs narrowband interference (Some circuits are more susceptible to sine-wave interference, some to pulse-type interference, some to broadband noise.)
If you specified every box in the N-dimensional matrix you would have hundreds of specifications.
Add to that the fact that the power supply must be specified before the subassemblies are designed/built/tested and vice versa, and it becomes an almost intractable problem.
The military's solution is to specify all power supplies and subassemblies for the worst-possible situation you can imagine. While that does improve the probability of success, it still is not perfect and is very expensive.
On the projects I worked on, we basically just specified the power supply as good as reasonably practicable using standard shielding and filtering techniques and then did whatever was needed in the various subassemblies to make the instrument meet specifications.
One point to pay attention to is ground loops. Ideally there would be a single-point ground in the spacecraft (probably in the main power supply). The idea is that each assembly's ground return connects only with a separate wire to the single-point ground.
It's not practical to do that 100% (think of the Can-Do power bus for example) but any module that can draw large current transients from the power supply should probably have separate power and ground wires that connect directly to the power supply. Also, any sensitive modules should not have any additional ground returns on the module side of their power supply filters. (That is, the ground return should go through the on-board filter.)
Al N1AL
On Mon, 2007-07-09 at 18:30, Jim Sanford wrote:
All: I'm excited to read all of the emails on this topic. Several thoughts, which I'd really like to discuss in more detail with all of you tomorrow night on TeamSpeak.
- As an experiment, and data collection exercise, I'd like to see
the inductor Juan identified as the source of radiated EMI replaced with a shielded inductor or toroid. As I mentioned to some of you, I saw a similar noise problem (source & victim were reversed) in my day job solved with exactly that one change. I think this would tell us much about how big a problem we have (radiated and conducted), and be a useful piece of data for posterity. As Bdale said almost two years ago, "Our legacy may very well be our documentation."
- Second, I'd like to see if we can, with a few ccomponent changes
on the existing widget board change the switching power supply frequency as Juan suggested. Another useful data point, with minimal effort.
Request for action: Can one of Chuck, Lyle, Stephen, or Bdale take on obtaining a shielded/toroidal inductor of the same value and provide to Juan for testing, and then take on researching a change to the switching PS frequency? IF so, Juan, would you and your team please make the changes and repeat testing?
- Regarding Chuck's comment: If we wind up with Can-Do Too, I'd ask
Juan if his accomplished project oscar team could take on component selection/purchase and construction of a couple of prototypes? This could happen in parallel with John's redesign of the U-band receiver. I know you guys have done a lot, but, YOU"RE GOOD!
- EMI Spec: You put a gun to my head, and I'm going to pull out the
MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable. In general, I'd like to eliminate as much mass and extra "touch" labor in the assembly process (multiple shields) as possible. Bob Davis: Please weigh in here, if the possible milled modules simplify this issue, please enlighten us.
- Chuck: I appreciate your comments on lessons learned. You
obviously have some things in mind, please scribble them down, get them to me, and I'll get placed on the EaglePedia lessons learned page.
- CAN-Do! team: Several folks have opined to me that it appears
that the widget design is final, complete, and we'd better live with it. I'd intended to discuss some of the above with you when Bdale got back. I am EXTREMELY PLEASED AND GRATEFUL to see you stepping up to the plate and acknowledging the need and willingness to do something based on what Juan has learned. Your intellectual honesty, integrity, and willingness to take on more for the team are recognized and appreciated.
- Requirements: Bob McGwier is correct, we really did start with a
very top-level requirements document. It is not perfect (Bob has hated it from the word go), but can be found on EaglePedia under Functional Requirements. It is also in need of updating, after the October BoD decision. On my list to do. Like you, I have finite energy and time, but it is on my list. I think John did an EXCELLENT job of documenting the UHF Receiver requirements based on what he knew. The need for an EMI spec was not obvious, but is now, thanks to Juan's testing efforts and exceptional documentation. Lou: Functional requirements for power supplies? Bob Davis: Functional requirements for structure and thermal performance? etc. etc.....we have much to do, but I think worthwhile effort. By the way, I'm reading (in a few spare minutes here and there) an EXCELLENT book on requirements management. When I finish, look for a review of it on my project management page. I will also be providing suggestions on writing "good" requirements, based on that book and my recent experiences in the day job.
- Somebody brought up the issue of CAN bus vs. discrete wiring
harness. In my mind, the discrete harness is a non-starter. WAY too much room for error and difficulty in testing. Yeah, I know the AO-40 harness was perfect the first time, but the guys who made that happen have made it clear to me that they don't ever want to do it again -- and I agree. So, I think we should remain committed to the CAN bus for many reasons. In my view, the recent "issues" with the CAN-Do! widget are just issues to deal with, not show stoppers. The CAN-Do! team is willing to deal with the issues, and so should the rest of us. Case closed in my mind. As always, open to well-justified better idea, but I think the writing remains on the wall.
I'm sure there's more action following this recent discussion, but specifics currently elude me. Feel free to send me suggestions, update the agenda for tomorrow night's TeamSpeak, and please be there.
Thank you all. Very 73, Jim wb4gcs@amsat.org
Robert McGwier wrote:
Bill Ress wrote:
All - -
To add support to Juan's conviction that we need to start developing "top down" specifications versus the bottom up activities we've been involved with, I would add that in order to develop a "realistic" EMI spec for the satellites power distribution system, we really need to know what those circuits will do.
With that in mind, I feel we need to breadboard the key circuits associated with that system and get hard data versus shooting from the hip with assumptions. At some point this power system is needed anyway, so why not focus design attention on that "top level" system now and get that issue settled - or at least better understood?
On the issue of housing panel area, and the possible consideration of a Mark 2 version, I think if I remember correctly, there were comments on wondering why a DB-9 (or even a physically smaller connector series) couldn't be used or are all the 15 pins needed?
Regards...Bill - N6GHz
I also support the breadboarding of primary circuits. And we did develop our specifications for the latest incarnation of Eagle top down. We started with what services we wanted to deliver and moved down from there.
When I rejoined the project, and started the software defined transponder movement, and long before I was leadership, the Can-Do was "in the can". I had almost no input to it. That said, I really do support the goal of the CanDo. Anyone who has heard of the horror stories of Marie Marr and the wiring harness or seen Lou's spreadsheet for interconnections for AO-40 knows that these few words do not do it justice. We have found a gremlin. That is normal in any project of this complexity and is not easily remedied by specifications in a project like this where the work and the tools necessary to make the relevant measurements are spread over the globe.
I look forward to our doing better as a team.
Bob
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Re electromagnetic interference in Eagle:
I suspect the big issue will be neigher component cost nor weight, but rather the size of the engineering task, both for the specification writer and the hardware designers.
An over-complicated spec just makes extra work for everybody. A too-simple spec risks a last-minute re-design. Paraphrasing Einstein, the specification should be as simple as possible, but no simpler.
Alan
Designing for the worst case probably makes sense for Eagle. The number of units being built is tiny so component cost for the electronics is not a big issue. The big issue is weight.
73,
John KD6OZH
----- Original Message ----- From: "Alan Bloom" n1al@cds1.net To: eagle@amsat.org Cc: eaglesensor@vom.com Sent: Tuesday, July 10, 2007 06:37 UTC Subject: [eagle] Re: CAN-Do-Too! ??????????
Jim wrote:
- EMI Spec: You put a gun to my head, and I'm going to pull out the
MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable.
I specified several power supplies when I worked for HP/Agilent. I found it really hard to come up with system-level noise specifications in instruments for the same reasons as in the Eagle project. The problem is that it's a complicated multi-dimensional problem.
Dimension 1: Emissions (power supply) vs susceptibility (modules) Dimension 2: Radiated vs conducted emissions Dimension 3: Interference path: Radiated:
- Magnetic (inductive) vs electric (capacitive) coupling
Conducted:
- Power supply bus vs signal lines vs ground loops
- Voltage (open circuit) vs current (short circuit) specification
Dimension 4: Emissions level versus frequency (audio to microwave) Dimension 5: Broadband vs narrowband interference (Some circuits are more susceptible to sine-wave interference, some to pulse-type interference, some to broadband noise.)
If you specified every box in the N-dimensional matrix you would have hundreds of specifications.
Add to that the fact that the power supply must be specified before the subassemblies are designed/built/tested and vice versa, and it becomes an almost intractable problem.
The military's solution is to specify all power supplies and subassemblies for the worst-possible situation you can imagine. While that does improve the probability of success, it still is not perfect and is very expensive.
On the projects I worked on, we basically just specified the power supply as good as reasonably practicable using standard shielding and filtering techniques and then did whatever was needed in the various subassemblies to make the instrument meet specifications.
One point to pay attention to is ground loops. Ideally there would be a single-point ground in the spacecraft (probably in the main power supply). The idea is that each assembly's ground return connects only with a separate wire to the single-point ground.
It's not practical to do that 100% (think of the Can-Do power bus for example) but any module that can draw large current transients from the power supply should probably have separate power and ground wires that connect directly to the power supply. Also, any sensitive modules should not have any additional ground returns on the module side of their power supply filters. (That is, the ground return should go through the on-board filter.)
Al N1AL
On Mon, 2007-07-09 at 18:30, Jim Sanford wrote:
All: I'm excited to read all of the emails on this topic. Several thoughts, which I'd really like to discuss in more detail with all of you tomorrow night on TeamSpeak.
- As an experiment, and data collection exercise, I'd like to see
the inductor Juan identified as the source of radiated EMI replaced with a shielded inductor or toroid. As I mentioned to some of you, I saw a similar noise problem (source & victim were reversed) in my day job solved with exactly that one change. I think this would tell us much about how big a problem we have (radiated and conducted), and be a useful piece of data for posterity. As Bdale said almost two years ago, "Our legacy may very well be our documentation."
- Second, I'd like to see if we can, with a few ccomponent changes
on the existing widget board change the switching power supply frequency as Juan suggested. Another useful data point, with minimal effort.
Request for action: Can one of Chuck, Lyle, Stephen, or Bdale take on obtaining a shielded/toroidal inductor of the same value and provide to Juan for testing, and then take on researching a change to the switching PS frequency? IF so, Juan, would you and your team please make the changes and repeat testing?
- Regarding Chuck's comment: If we wind up with Can-Do Too, I'd ask
Juan if his accomplished project oscar team could take on component selection/purchase and construction of a couple of prototypes? This could happen in parallel with John's redesign of the U-band receiver. I know you guys have done a lot, but, YOU"RE GOOD!
- EMI Spec: You put a gun to my head, and I'm going to pull out the
MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable. In general, I'd like to eliminate as much mass and extra "touch" labor in the assembly process (multiple shields) as possible. Bob Davis: Please weigh in here, if the possible milled modules simplify this issue, please enlighten us.
- Chuck: I appreciate your comments on lessons learned. You
obviously have some things in mind, please scribble them down, get them to me, and I'll get placed on the EaglePedia lessons learned page.
- CAN-Do! team: Several folks have opined to me that it appears
that the widget design is final, complete, and we'd better live with it. I'd intended to discuss some of the above with you when Bdale got back. I am EXTREMELY PLEASED AND GRATEFUL to see you stepping up to the plate and acknowledging the need and willingness to do something based on what Juan has learned. Your intellectual honesty, integrity, and willingness to take on more for the team are recognized and appreciated.
- Requirements: Bob McGwier is correct, we really did start with a
very top-level requirements document. It is not perfect (Bob has hated it from the word go), but can be found on EaglePedia under Functional Requirements. It is also in need of updating, after the October BoD decision. On my list to do. Like you, I have finite energy and time, but it is on my list. I think John did an EXCELLENT job of documenting the UHF Receiver requirements based on what he knew. The need for an EMI spec was not obvious, but is now, thanks to Juan's testing efforts and exceptional documentation. Lou: Functional requirements for power supplies? Bob Davis: Functional requirements for structure and thermal performance? etc. etc.....we have much to do, but I think worthwhile effort. By the way, I'm reading (in a few spare minutes here and there) an EXCELLENT book on requirements management. When I finish, look for a review of it on my project management page. I will also be providing suggestions on writing "good" requirements, based on that book and my recent experiences in the day job.
- Somebody brought up the issue of CAN bus vs. discrete wiring
harness. In my mind, the discrete harness is a non-starter. WAY too much room for error and difficulty in testing. Yeah, I know the AO-40 harness was perfect the first time, but the guys who made that happen have made it clear to me that they don't ever want to do it again -- and I agree. So, I think we should remain committed to the CAN bus for many reasons. In my view, the recent "issues" with the CAN-Do! widget are just issues to deal with, not show stoppers. The CAN-Do! team is willing to deal with the issues, and so should the rest of us. Case closed in my mind. As always, open to well-justified better idea, but I think the writing remains on the wall.
I'm sure there's more action following this recent discussion, but specifics currently elude me. Feel free to send me suggestions, update the agenda for tomorrow night's TeamSpeak, and please be there.
Thank you all. Very 73, Jim wb4gcs@amsat.org
Robert McGwier wrote:
Bill Ress wrote:
All - -
To add support to Juan's conviction that we need to start
developing
"top down" specifications versus the bottom up activities we've
been
involved with, I would add that in order to develop a "realistic" EMI spec for the satellites power distribution system, we really need
to
know what those circuits will do.
With that in mind, I feel we need to breadboard the key circuits associated with that system and get hard data versus shooting from the hip with assumptions. At some point this power system is needed anyway, so why not focus design attention on that "top level" system now
and
get that issue settled - or at least better understood?
On the issue of housing panel area, and the possible consideration
of
a Mark 2 version, I think if I remember correctly, there were
comments
on wondering why a DB-9 (or even a physically smaller connector
series)
couldn't be used or are all the 15 pins needed?
Regards...Bill - N6GHz
I also support the breadboarding of primary circuits. And we did develop our specifications for the latest incarnation of Eagle top down. We started with what services we wanted to deliver and moved down from there.
When I rejoined the project, and started the software defined transponder movement, and long before I was leadership, the Can-Do
was
"in the can". I had almost no input to it. That said, I really do support the goal of the CanDo. Anyone who has heard of the horror stories of Marie Marr and the wiring harness or seen Lou's
spreadsheet
for interconnections for AO-40 knows that these few words do not do
it
justice. We have found a gremlin. That is normal in any project of this complexity and is not easily remedied by specifications in a project like this where the work and the tools necessary to make the relevant measurements are spread over the globe.
I look forward to our doing better as a team.
Bob
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
All,
An EMI spec doesn't have to become an intractable problem. Let's approach this from a purely practical standpoint.
From a Global Perspective:
1) Build up the proposed switching battery charger circuitry and quantify the conducted noise output. Do the same for anything else that is part of the common power distribution for Eagle.
2) Create a piece of hardware that mimics that conducted noise - just copy some of the switching supplies that will actually be used and stick them in a box...
Write a spec that says that while receiving primary DC power from this noisy power source the stuff has to still work, and then define 'work'.
CAN-Do/Enclosure combination:
Once these two are sorted out then you can do the same thing again here. Equipment receiving switched power from CAN-DO has to be able to work while getting the noisy primary power fed through the CAN-Do module, and sitting inside the enclosure.
Obviously this is a simplification, but if we create several noisy power sources that mimic what we expect to see in orbit, then the spec doesn't have to deal with radiated field intensity and other parameters that we can't measure anyway. Just stick your board in an enclosure, close the lid, run it off the noisy power, and see how it works...
That's my two cents worth.
73,
Juan
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of John B. Stephensen Sent: Tuesday, July 10, 2007 8:35 AM To: n1al@cds1.net; eagle@amsat.org Cc: eaglesensor@vom.com Subject: [eagle] Re: CAN-Do-Too! ??????????
Designing for the worst case probably makes sense for Eagle. The number of units being built is tiny so component cost for the electronics is not a big
issue. The big issue is weight.
73,
John KD6OZH
----- Original Message ----- From: "Alan Bloom" n1al@cds1.net To: eagle@amsat.org Cc: eaglesensor@vom.com Sent: Tuesday, July 10, 2007 06:37 UTC Subject: [eagle] Re: CAN-Do-Too! ??????????
Jim wrote:
- EMI Spec: You put a gun to my head, and I'm going to pull out the
MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable.
I specified several power supplies when I worked for HP/Agilent. I found it really hard to come up with system-level noise specifications in instruments for the same reasons as in the Eagle project. The problem is that it's a complicated multi-dimensional problem.
Dimension 1: Emissions (power supply) vs susceptibility (modules) Dimension 2: Radiated vs conducted emissions Dimension 3: Interference path: Radiated:
- Magnetic (inductive) vs electric (capacitive) coupling
Conducted:
- Power supply bus vs signal lines vs ground loops
- Voltage (open circuit) vs current (short circuit) specification
Dimension 4: Emissions level versus frequency (audio to microwave) Dimension 5: Broadband vs narrowband interference (Some circuits are more susceptible to sine-wave interference, some to pulse-type interference, some to broadband noise.)
If you specified every box in the N-dimensional matrix you would have hundreds of specifications.
Add to that the fact that the power supply must be specified before the subassemblies are designed/built/tested and vice versa, and it becomes an almost intractable problem.
The military's solution is to specify all power supplies and subassemblies for the worst-possible situation you can imagine. While that does improve the probability of success, it still is not perfect and is very expensive.
On the projects I worked on, we basically just specified the power supply as good as reasonably practicable using standard shielding and filtering techniques and then did whatever was needed in the various subassemblies to make the instrument meet specifications.
One point to pay attention to is ground loops. Ideally there would be a single-point ground in the spacecraft (probably in the main power supply). The idea is that each assembly's ground return connects only with a separate wire to the single-point ground.
It's not practical to do that 100% (think of the Can-Do power bus for example) but any module that can draw large current transients from the power supply should probably have separate power and ground wires that connect directly to the power supply. Also, any sensitive modules should not have any additional ground returns on the module side of their power supply filters. (That is, the ground return should go through the on-board filter.)
Al N1AL
On Mon, 2007-07-09 at 18:30, Jim Sanford wrote:
All: I'm excited to read all of the emails on this topic. Several thoughts, which I'd really like to discuss in more detail with all of you tomorrow night on TeamSpeak.
- As an experiment, and data collection exercise, I'd like to see
the inductor Juan identified as the source of radiated EMI replaced with a shielded inductor or toroid. As I mentioned to some of you, I saw a similar noise problem (source & victim were reversed) in my day job solved with exactly that one change. I think this would tell us much about how big a problem we have (radiated and conducted), and be a useful piece of data for posterity. As Bdale said almost two years ago, "Our legacy may very well be our documentation."
- Second, I'd like to see if we can, with a few ccomponent changes
on the existing widget board change the switching power supply frequency as Juan suggested. Another useful data point, with minimal effort.
Request for action: Can one of Chuck, Lyle, Stephen, or Bdale take on obtaining a shielded/toroidal inductor of the same value and provide to Juan for testing, and then take on researching a change to the switching PS frequency? IF so, Juan, would you and your team please make the changes and repeat testing?
- Regarding Chuck's comment: If we wind up with Can-Do Too, I'd ask
Juan if his accomplished project oscar team could take on component selection/purchase and construction of a couple of prototypes? This could happen in parallel with John's redesign of the U-band receiver. I know you guys have done a lot, but, YOU"RE GOOD!
- EMI Spec: You put a gun to my head, and I'm going to pull out the
MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable. In general, I'd like to eliminate as much mass and extra "touch" labor in the assembly process (multiple shields) as possible. Bob Davis: Please weigh in here, if the possible milled modules simplify this issue, please enlighten us.
- Chuck: I appreciate your comments on lessons learned. You
obviously have some things in mind, please scribble them down, get them to me, and I'll get placed on the EaglePedia lessons learned page.
- CAN-Do! team: Several folks have opined to me that it appears
that the widget design is final, complete, and we'd better live with it. I'd intended to discuss some of the above with you when Bdale got back. I am EXTREMELY PLEASED AND GRATEFUL to see you stepping up to the plate and acknowledging the need and willingness to do something based on what Juan has learned. Your intellectual honesty, integrity, and willingness to take on more for the team are recognized and appreciated.
- Requirements: Bob McGwier is correct, we really did start with a
very top-level requirements document. It is not perfect (Bob has hated it from the word go), but can be found on EaglePedia under Functional Requirements. It is also in need of updating, after the October BoD decision. On my list to do. Like you, I have finite energy and time, but it is on my list. I think John did an EXCELLENT job of documenting the UHF Receiver requirements based on what he knew. The need for an EMI spec was not obvious, but is now, thanks to Juan's testing efforts and exceptional documentation. Lou: Functional requirements for power supplies? Bob Davis: Functional requirements for structure and thermal performance? etc. etc.....we have much to do, but I think worthwhile effort. By the way, I'm reading (in a few spare minutes here and there) an EXCELLENT book on requirements management. When I finish, look for a review of it on my project management page. I will also be providing suggestions on writing "good" requirements, based on that book and my recent experiences in the day job.
- Somebody brought up the issue of CAN bus vs. discrete wiring
harness. In my mind, the discrete harness is a non-starter. WAY too much room for error and difficulty in testing. Yeah, I know the AO-40 harness was perfect the first time, but the guys who made that happen have made it clear to me that they don't ever want to do it again -- and I agree. So, I think we should remain committed to the CAN bus for many reasons. In my view, the recent "issues" with the CAN-Do! widget are just issues to deal with, not show stoppers. The CAN-Do! team is willing to deal with the issues, and so should the rest of us. Case closed in my mind. As always, open to well-justified better idea, but I think the writing remains on the wall.
I'm sure there's more action following this recent discussion, but specifics currently elude me. Feel free to send me suggestions, update the agenda for tomorrow night's TeamSpeak, and please be there.
Thank you all. Very 73, Jim wb4gcs@amsat.org
Robert McGwier wrote:
Bill Ress wrote:
All - -
To add support to Juan's conviction that we need to start developing "top down" specifications versus the bottom up activities we've been involved with, I would add that in order to develop a "realistic" EMI spec for the satellites power distribution system, we really need to know what those circuits will do.
With that in mind, I feel we need to breadboard the key circuits associated with that system and get hard data versus shooting from the hip with assumptions. At some point this power system is needed anyway, so why not focus design attention on that "top level" system now and get that issue settled - or at least better understood?
On the issue of housing panel area, and the possible consideration of
a Mark 2 version, I think if I remember correctly, there were comments on wondering why a DB-9 (or even a physically smaller connector series) couldn't be used or are all the 15 pins needed?
Regards...Bill - N6GHz
I also support the breadboarding of primary circuits. And we did develop our specifications for the latest incarnation of Eagle top down. We started with what services we wanted to deliver and moved down from there.
When I rejoined the project, and started the software defined transponder movement, and long before I was leadership, the Can-Do was "in the can". I had almost no input to it. That said, I really do support the goal of the CanDo. Anyone who has heard of the horror stories of Marie Marr and the wiring harness or seen Lou's spreadsheet for interconnections for AO-40 knows that these few words do not do it justice. We have found a gremlin. That is normal in any project of this complexity and is not easily remedied by specifications in a project like this where the work and the tools necessary to make the relevant measurements are spread over the globe.
I look forward to our doing better as a team.
Bob
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Hi all,
Good meeting Jim. Nice turn out.
Below, Juan wrote what I know he wanted to say on the conference (but had hardware problems) and what I tried to say but didn't say it as well as he wrote it.
Juan has identified some long poles in the tent that have serious trickle down effects. No doubt we'll uncover more show stoppers. I especially like his idea for a power distribution "black box" which can be provided to or duplicated by module designers.
Clearly, in my opinion, Juan has also uncovered the fact that don't know enough about some critical hardware - one being the power distribution system. To reiterate his suggestion, lets get started on building the key circuit blocks that will help define what the power will look like. I'll bet we'll find that the noise gremlins might not be as bad as we're thinking and we might find fixes to mitigate what we do find right there at the source. Instead of forcing modules like the URx to be designed for some worst case, unknown condition, lets start getting these gremlins out of the closet.
Lou, I understand that your the power distribution guy and I'm sure, like many of us, your strapped for time. While I'm not a power supply guy, but I take direction well, so 'm offering my time, test facility and soldering iron to help get answers. I need you to tell me what you need done to get some of these answers. If you've got it covered, then I fade away back to my microwave world and shut up.
Really glad to see the support and understanding of the "widget's" noise problem from the CAN-Do team.
Golly - we're just starting to have fun!!
Regards...Bill - N6GHz
Juan Rivera wrote:
All,
An EMI spec doesn't have to become an intractable problem. Let's approach this from a purely practical standpoint.
From a Global Perspective:
- Build up the proposed switching battery charger circuitry and quantify
the conducted noise output. Do the same for anything else that is part of the common power distribution for Eagle.
- Create a piece of hardware that mimics that conducted noise - just copy
some of the switching supplies that will actually be used and stick them in a box...
Write a spec that says that while receiving primary DC power from this noisy power source the stuff has to still work, and then define 'work'.
CAN-Do/Enclosure combination:
Once these two are sorted out then you can do the same thing again here. Equipment receiving switched power from CAN-DO has to be able to work while getting the noisy primary power fed through the CAN-Do module, and sitting inside the enclosure.
Obviously this is a simplification, but if we create several noisy power sources that mimic what we expect to see in orbit, then the spec doesn't have to deal with radiated field intensity and other parameters that we can't measure anyway. Just stick your board in an enclosure, close the lid, run it off the noisy power, and see how it works...
That's my two cents worth.
73,
Juan
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of John B. Stephensen Sent: Tuesday, July 10, 2007 8:35 AM To: n1al@cds1.net; eagle@amsat.org Cc: eaglesensor@vom.com Subject: [eagle] Re: CAN-Do-Too! ??????????
Designing for the worst case probably makes sense for Eagle. The number of units being built is tiny so component cost for the electronics is not a big
issue. The big issue is weight.
73,
John KD6OZH
----- Original Message ----- From: "Alan Bloom" n1al@cds1.net To: eagle@amsat.org Cc: eaglesensor@vom.com Sent: Tuesday, July 10, 2007 06:37 UTC Subject: [eagle] Re: CAN-Do-Too! ??????????
Jim wrote:
- EMI Spec: You put a gun to my head, and I'm going to pull out the
MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable.
I specified several power supplies when I worked for HP/Agilent. I found it really hard to come up with system-level noise specifications in instruments for the same reasons as in the Eagle project. The problem is that it's a complicated multi-dimensional problem.
Dimension 1: Emissions (power supply) vs susceptibility (modules) Dimension 2: Radiated vs conducted emissions Dimension 3: Interference path: Radiated:
- Magnetic (inductive) vs electric (capacitive) coupling
Conducted:
- Power supply bus vs signal lines vs ground loops
- Voltage (open circuit) vs current (short circuit) specification
Dimension 4: Emissions level versus frequency (audio to microwave) Dimension 5: Broadband vs narrowband interference (Some circuits are more susceptible to sine-wave interference, some to pulse-type interference, some to broadband noise.)
If you specified every box in the N-dimensional matrix you would have hundreds of specifications.
Add to that the fact that the power supply must be specified before the subassemblies are designed/built/tested and vice versa, and it becomes an almost intractable problem.
The military's solution is to specify all power supplies and subassemblies for the worst-possible situation you can imagine. While that does improve the probability of success, it still is not perfect and is very expensive.
On the projects I worked on, we basically just specified the power supply as good as reasonably practicable using standard shielding and filtering techniques and then did whatever was needed in the various subassemblies to make the instrument meet specifications.
One point to pay attention to is ground loops. Ideally there would be a single-point ground in the spacecraft (probably in the main power supply). The idea is that each assembly's ground return connects only with a separate wire to the single-point ground.
It's not practical to do that 100% (think of the Can-Do power bus for example) but any module that can draw large current transients from the power supply should probably have separate power and ground wires that connect directly to the power supply. Also, any sensitive modules should not have any additional ground returns on the module side of their power supply filters. (That is, the ground return should go through the on-board filter.)
Al N1AL
On Mon, 2007-07-09 at 18:30, Jim Sanford wrote:
All: I'm excited to read all of the emails on this topic. Several thoughts, which I'd really like to discuss in more detail with all of you tomorrow night on TeamSpeak.
- As an experiment, and data collection exercise, I'd like to see
the inductor Juan identified as the source of radiated EMI replaced with a shielded inductor or toroid. As I mentioned to some of you, I saw a similar noise problem (source & victim were reversed) in my day job solved with exactly that one change. I think this would tell us much about how big a problem we have (radiated and conducted), and be a useful piece of data for posterity. As Bdale said almost two years ago, "Our legacy may very well be our documentation."
- Second, I'd like to see if we can, with a few ccomponent changes
on the existing widget board change the switching power supply frequency as Juan suggested. Another useful data point, with minimal effort.
Request for action: Can one of Chuck, Lyle, Stephen, or Bdale take on obtaining a shielded/toroidal inductor of the same value and provide to Juan for testing, and then take on researching a change to the switching PS frequency? IF so, Juan, would you and your team please make the changes and repeat testing?
- Regarding Chuck's comment: If we wind up with Can-Do Too, I'd ask
Juan if his accomplished project oscar team could take on component selection/purchase and construction of a couple of prototypes? This could happen in parallel with John's redesign of the U-band receiver. I know you guys have done a lot, but, YOU"RE GOOD!
- EMI Spec: You put a gun to my head, and I'm going to pull out the
MIL-STD, which is probably overkill, but MAYBE NOT. I'd really prefer that one of you guiys current in the INDUSTRIAL world take on this task and come up with something good enough and reasonable. In general, I'd like to eliminate as much mass and extra "touch" labor in the assembly process (multiple shields) as possible. Bob Davis: Please weigh in here, if the possible milled modules simplify this issue, please enlighten us.
- Chuck: I appreciate your comments on lessons learned. You
obviously have some things in mind, please scribble them down, get them to me, and I'll get placed on the EaglePedia lessons learned page.
- CAN-Do! team: Several folks have opined to me that it appears
that the widget design is final, complete, and we'd better live with it. I'd intended to discuss some of the above with you when Bdale got back. I am EXTREMELY PLEASED AND GRATEFUL to see you stepping up to the plate and acknowledging the need and willingness to do something based on what Juan has learned. Your intellectual honesty, integrity, and willingness to take on more for the team are recognized and appreciated.
- Requirements: Bob McGwier is correct, we really did start with a
very top-level requirements document. It is not perfect (Bob has hated it from the word go), but can be found on EaglePedia under Functional Requirements. It is also in need of updating, after the October BoD decision. On my list to do. Like you, I have finite energy and time, but it is on my list. I think John did an EXCELLENT job of documenting the UHF Receiver requirements based on what he knew. The need for an EMI spec was not obvious, but is now, thanks to Juan's testing efforts and exceptional documentation. Lou: Functional requirements for power supplies? Bob Davis: Functional requirements for structure and thermal performance? etc. etc.....we have much to do, but I think worthwhile effort. By the way, I'm reading (in a few spare minutes here and there) an EXCELLENT book on requirements management. When I finish, look for a review of it on my project management page. I will also be providing suggestions on writing "good" requirements, based on that book and my recent experiences in the day job.
- Somebody brought up the issue of CAN bus vs. discrete wiring
harness. In my mind, the discrete harness is a non-starter. WAY too much room for error and difficulty in testing. Yeah, I know the AO-40 harness was perfect the first time, but the guys who made that happen have made it clear to me that they don't ever want to do it again -- and I agree. So, I think we should remain committed to the CAN bus for many reasons. In my view, the recent "issues" with the CAN-Do! widget are just issues to deal with, not show stoppers. The CAN-Do! team is willing to deal with the issues, and so should the rest of us. Case closed in my mind. As always, open to well-justified better idea, but I think the writing remains on the wall.
I'm sure there's more action following this recent discussion, but specifics currently elude me. Feel free to send me suggestions, update the agenda for tomorrow night's TeamSpeak, and please be there.
Thank you all. Very 73, Jim wb4gcs@amsat.org
Robert McGwier wrote:
Bill Ress wrote:
All - -
To add support to Juan's conviction that we need to start developing "top down" specifications versus the bottom up activities we've been involved with, I would add that in order to develop a "realistic" EMI spec for the satellites power distribution system, we really need to know what those circuits will do.
With that in mind, I feel we need to breadboard the key circuits associated with that system and get hard data versus shooting from the hip with assumptions. At some point this power system is needed anyway, so why not focus design attention on that "top level" system now and get that issue settled - or at least better understood?
On the issue of housing panel area, and the possible consideration of
a Mark 2 version, I think if I remember correctly, there were comments on wondering why a DB-9 (or even a physically smaller connector series) couldn't be used or are all the 15 pins needed?
Regards...Bill - N6GHz
I also support the breadboarding of primary circuits. And we did develop our specifications for the latest incarnation of Eagle top down. We started with what services we wanted to deliver and moved down from there.
When I rejoined the project, and started the software defined transponder movement, and long before I was leadership, the Can-Do was "in the can". I had almost no input to it. That said, I really do support the goal of the CanDo. Anyone who has heard of the horror stories of Marie Marr and the wiring harness or seen Lou's spreadsheet for interconnections for AO-40 knows that these few words do not do it justice. We have found a gremlin. That is normal in any project of this complexity and is not easily remedied by specifications in a project like this where the work and the tools necessary to make the relevant measurements are spread over the globe.
I look forward to our doing better as a team.
Bob
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Sorry that I couldn't make the conference call. The air conditioner repairman decided that he had to switch his appointment from 9 AM to 2 PM so I had to move my mother's neurologist appointment and be the last patient.
73,
John KD6OZH
All -
I'm sure you all have been reading the interesting and perhaps timely discussion on the AMSAT thread about "Future Radical Satellite Designs."
I hope someone has been taking names with the intent of recruiting some of this talent out there to fill our lack or manpower resources that Chuck Green alluded to!!
Regards...Bill - N6GHz
This will be a very useful project, especially if it can be done in parallel with the next revision of the U-band receiver. A shielded (either torroidal or pot core) inductor will go a long way in reducing EMI as will changing the configuration of the filtering. There will still be a radiated electric field so a sheilding box should be designed at the same as the new PCB. It's useful to keep input and output connectors at opposite ends of the connector mounting bracket, so the new widget should be as narrow as possible. The shield should sit above the module PCB, if possible.
73,
John KD6OZH
----- Original Message ----- From: "Chuck Green" greencl@mindspring.com To: juan-rivera@sbcglobal.net Cc: "David Smith" w6te@msn.com; "Dave Black (Work)" dblack@mail.arc.nasa.gov; "Dave Black (Home)" dblack1054@yahoo.com; eagle@amsat.org; "Samsonoff@Mac. Com" samsonoff@mac.com; "Juan.Rivera (Work)" Juan.Rivera@gd-ais.com Sent: Monday, July 09, 2007 14:56 UTC Subject: [eagle] CAN-Do-Too! ??????????
Hi Guys,
Juan has done a lot of outstanding work which resulted in some substantial critiquing of the CAN-Do! (Affectionately called a "widget.") It is unfortunate that it has taken several years since the CAN-Do! was designed and then 100 units built before an application of sufficient sensitivity used it to discover it's shortcomings. History can provide lessons that I hope we can learn from, but it seldom provides solutions to the problems encountered. Lyle and I have exchanged a few thoughts privately and it seems it may now be time to consider solutions to the problems found.
The only practical way to accomplish this is to develop the next generation CAN interface device. Dare I call it the CAN-Do-Too! ?
All technical specifications should remain the same. What this really means is that a next-generation controller must run *exactly* the same firmware currently running the CAN-Do! .
All specifications added or redefined should be carefully defined and be measurable.
General specifications that we worked from before were that the widget should use as little power as possible and consume as little of a module's volume as possible. The first of these should remain the same, "use as little power as possible."
But the second should be changed to "consume as little of the connector panel space as possible" even if it means consuming a little more of the module volume. This means the widget PCB and components should not extend beyond the dimensions of the DA-15P connector in either dimension. A possible compromise to this would be to let the PCB run past one end of the DA-15P but not more than the DA-15P is forced away from the side of the box by the box design.
The power supply could be completely redesigned. Or the inductor of the existing supply could be exchanged for one that is a toroid (the existing one is not). If someone wants to step up and design a new power supply, great! If not, then we would simply change the inductor. I'd sure like to see someone take this on. With so many of these in the satellite, only a few milliwatts is important. And the noise issue Juan uncovered is *very* important.
It may be that some, or maybe all, of the widget should be enclosed in a metal box. It may be that just changing the inductor would allow a new widget to meet the yet-to-be-defined noise specifications.
The input power filter for module power should be separate from the widget power supply input filter. The module power filter is a filter that will not meet all module requirements, but would likely meet the requirements of a digital module. Some modules, such as receivers, may need additional power conditioning. But in any case, the widget power supply should not add to the module power supply noise.
There should be a simple way to disconnect the filter capacitors on the widget from the data lines when the widget is in Byte mode. Most people are not aware of this problem which was uncovered by another module builder. It only effects those using the CAN-Do! in Byte mode.
Using a synchronizing signal does not seem practical to us. It would complicate the design of the widget power supply so that it would function with or without the presence of the synchronizing signal (we don't want to introduce a single-point-of-failure). It would dramatically increase the satellite wiring harness complexity, something the widget was intended to a simplify. And it would inhibit the widget power supply from going into various power-saving modes.
Recruit some new people into this project. Lyle simply doesn't have any time for doing new designs right now. We need a power supply designer as stated above. And my time is limited. I'm willing to lay out the new design and build a few prototypes, but I need others to do parts procurement and volume building of widgets. I'll prepare flight units if desired. We've talked about having someone skilled in parts procurement before but I don't know of anything having come of it. The bottom line, if this is going to happen, Lyle and I need others to be involved.
If you think this is a good idea, or bad, please express yourself. And if you have other comments to add to the above, or would like to modify/expand on above comments, please do so.
Looking forward to your comments,
Chuck and Lyle _______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
I agree with all your comments Chuck. I would add one additional and that is make some provisions for mounting the widget other than the connector.
Lou McFadin W5DID w5did@mac.com
On Jul 9, 2007, at 10:56 AM, Chuck Green wrote:
Hi Guys,
Juan has done a lot of outstanding work which resulted in some substantial critiquing of the CAN-Do! (Affectionately called a "widget.") It is unfortunate that it has taken several years since the CAN-Do! was designed and then 100 units built before an application of sufficient sensitivity used it to discover it's shortcomings. History can provide lessons that I hope we can learn from, but it seldom provides solutions to the problems encountered. Lyle and I have exchanged a few thoughts privately and it seems it may now be time to consider solutions to the problems found.
The only practical way to accomplish this is to develop the next generation CAN interface device. Dare I call it the CAN-Do-Too! ?
All technical specifications should remain the same. What this really means is that a next-generation controller must run *exactly* the same firmware currently running the CAN-Do! .
All specifications added or redefined should be carefully defined and be measurable.
General specifications that we worked from before were that the widget should use as little power as possible and consume as little of a module's volume as possible. The first of these should remain the same, "use as little power as possible."
But the second should be changed to "consume as little of the connector panel space as possible" even if it means consuming a little more of the module volume. This means the widget PCB and components should not extend beyond the dimensions of the DA-15P connector in either dimension. A possible compromise to this would be to let the PCB run past one end of the DA-15P but not more than the DA-15P is forced away from the side of the box by the box design.
The power supply could be completely redesigned. Or the inductor of the existing supply could be exchanged for one that is a toroid (the existing one is not). If someone wants to step up and design a new power supply, great! If not, then we would simply change the inductor. I'd sure like to see someone take this on. With so many of these in the satellite, only a few milliwatts is important. And the noise issue Juan uncovered is *very* important.
It may be that some, or maybe all, of the widget should be enclosed in a metal box. It may be that just changing the inductor would allow a new widget to meet the yet-to-be-defined noise specifications.
The input power filter for module power should be separate from the widget power supply input filter. The module power filter is a filter that will not meet all module requirements, but would likely meet the requirements of a digital module. Some modules, such as receivers, may need additional power conditioning. But in any case, the widget power supply should not add to the module power supply noise.
There should be a simple way to disconnect the filter capacitors on the widget from the data lines when the widget is in Byte mode. Most people are not aware of this problem which was uncovered by another module builder. It only effects those using the CAN-Do! in Byte mode.
Using a synchronizing signal does not seem practical to us. It would complicate the design of the widget power supply so that it would function with or without the presence of the synchronizing signal (we don't want to introduce a single-point-of-failure). It would dramatically increase the satellite wiring harness complexity, something the widget was intended to a simplify. And it would inhibit the widget power supply from going into various power-saving modes.
Recruit some new people into this project. Lyle simply doesn't have any time for doing new designs right now. We need a power supply designer as stated above. And my time is limited. I'm willing to lay out the new design and build a few prototypes, but I need others to do parts procurement and volume building of widgets. I'll prepare flight units if desired. We've talked about having someone skilled in parts procurement before but I don't know of anything having come of it. The bottom line, if this is going to happen, Lyle and I need others to be involved.
If you think this is a good idea, or bad, please express yourself. And if you have other comments to add to the above, or would like to modify/expand on above comments, please do so.
Looking forward to your comments,
Chuck and Lyle _______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Hi Guys,
I've collected a few topics from various peoples comments.
The CAN-Do! was designed to be mounted to the front wall of the module box. Since the connector could do this with the greatest simplicity, that's the way we went. Part of this had to do with minimizing the module volume used and part with heat conduction for the module power switch transistor. With the new mechanical configuration I have in mind, that will not be sufficient. Mounting spacers to the module PCB will likely be used. But this is all preliminary thinking and any specific suggestions would be appreciated.
It has been suggested that a DE-9 would be sufficient. Technically, this is correct. But it would require the elimination of five of the six user pins. Maybe "require" is too strong a word. Note that there are two CAN-H, two CAN-L, two power, and two ground (well, we ended up with three grounds). Technically, only one of each is needed. But two each were were provided to simplify the construction of the wiring harness (no small issue). The six user pins (one of them is named EB) were for special needs a module might have. Six may be overkill? The naming of one "EB" is a legacy from P3D where the engineering beacon was so pervasive throughout the satellite that it was decided to actually name one of the user pins as such. Part of this is also driven by P3E/P5A perceived requirements. P3E has used some of the user pins to input structure thermistor signals to modules that do not otherwise use all of their analog input pins on the 40 pin connector.
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
The switching frequency of approximately 5 kHz observed is not the natural frequency of the existing supply. It is likely the supply running in an idle mode since the actual power requirement of the widget is relatively small. To verify this, Juan might try putting an additional load on it. This can be done at the 40 pin connector. In any event, this points to the desirability for an experienced power supply designer re-designing the power supply.
It has been assumed, and enforced by the widget design, that a high power module would have a separate power input connector. If switching such a module on/off by the IHU is desired, the widget switched power would be used as a control line to switch the module power. The widget is capable of supplying several amps to the module but the current limit is specified at under an amp as a "normal" module can only dissipate a limited amount of heat anyway. We also scaled the upper end of the current measuring circuit at the specified current limit. And we added a two amp fuse.
Chuck
Hi Chuck,
I really appreciate you explaining the reasoning for the 15 versus 9 pins. Not having been around when the CAN-Do evolved, I wasn't aware of the thinking behind it but had noticed the currently "unused" pins and had to ask the question.
I have used a slightly thiner version of the D-Subs made by AMP but can put my hands on the P/N. But it's hard to beat the ubiquitous D-Subs.
Regards...Bill - N6GHz
Chuck Green wrote:
It has been suggested that a DE-9 would be sufficient. Technically, this is correct. But it would require the elimination of five of the six user pins. Maybe "require" is too strong a word. Note that there are two CAN-H, two CAN-L, two power, and two ground (well, we ended up with three grounds). Technically, only one of each is needed. But two each were were provided to simplify the construction of the wiring harness (no small issue). The six user pins (one of them is named EB) were for special needs a module might have. Six may be overkill? The naming of one "EB" is a legacy from P3D where the engineering beacon was so pervasive throughout the satellite that it was decided to actually name one of the user pins as such. Part of this is also driven by P3E/P5A perceived requirements. P3E has used some of the user pins to input structure thermistor signals to modules that do not otherwise use all of their analog input pins on the 40 pin connector.
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
Hi Chuck
The naming of one "EB" is a legacy from P3D where the engineering beacon was so pervasive throughout the satellite that it was decided to actually name one of the user pins as such. Part of this is also driven by P3E/P5A
perceived requirements. P3E has used some of the user pins to input structure thermistor signals to modules that do not otherwise use all of their analog input pins on the 40 pin connector.
On P3E, the EB signal goes to the P3E U/V transponder from the IHU3. In the U/V transponder, it hits a DSP GPIO pin via a voltage level adjustment and isolation circuit. The DSP uses this to generate the BPSK beacon.
73, Howard G6LVB
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
Bdale,
I used the high density 15-pin D connectors on the USNA Midstar-1 satellite with good results.
Rick W2GPS AMSAT LM2232
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Bdale Garbee Sent: Monday, July 16, 2007 11:57 AM To: Chuck Green Cc: David Smith; Dave Black ((Work)); Dave Black ((Home)); Louis McFadin; AMSAT Eagle; Samsonoff@Mac. Com; Juan.Rivera ((Work)) Subject: [eagle] Re: CAN-Do-Too! ??????????
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
Chuck, Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock. I see no inherent reason for not using them.
Lou McFadin W5DID w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$% &^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
Chuck,
I seem to recall that you wanted me to try loading down the CAN-Do switcher to see if the frequency went up. Was that you? I can't find the email. If it was, what additional load do you want me to apply? And are you going to send me some shielded inductors to test? Let me know and I'll jump on it for you.
73,
Juan
_____
From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Louis McFadin Sent: Monday, July 16, 2007 6:10 PM To: Chuck Green Cc: Dave Black ((Work)); Dave Black ((Home)); David Smith; AMSAT Eagle; Samsonoff@Mac. Com; Juan.Rivera ((Work)) Subject: [eagle] Re: CAN-Do-Too! ??????????
Chuck,
Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock.
I see no inherent reason for not using them.
Lou McFadin
W5DID
w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a
couple of years ago (three?), someone approached me after the CAN-Do!
talk that Stephen and I gave to ask why we weren't using the
higher-density connectors that put 15 pins in the same shell size as the
9-pin version of the series we have been using... and followed up by
sending me what looked like mil/aero-spec samples of such a part that I
probably still have in my basement somewhere. I'm sorry that I can't
recall at all who that person was, but it was someone who claimed to be
using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time
soon, so I didn't take any action on this suggestion. If we're going to
revisit the design and think we need more than 9 pins, it might be worth
investigating higher density connectors like that?
Bdale
Hi Juan,
I think you are referring to an e-mail I sent out. It was simply a suggestion to verify the hypothesis that the power supply is in a low power idle mode and hence the 5kHz you were seeing. It really doesn't matter if someone is going to redesign the power supply anyway.
I don't have any shielded inductors to send you. There may not be any such thing in the same footprint as the inductor used. But even if it has to be cobbled in somehow, it would be a good test to run. If anyone has such an inductor, or knows the part number of such a device, it might be worth getting one. But again, if someone is going to redesign the power supply anyway, I would assume they will at least use a toroid, and possibly a shielded one.
Chuck
Juan Rivera wrote:
Chuck,
I seem to recall that you wanted me to try loading down the CAN-Do switcher to see if the frequency went up. Was that you? I can’t find the email. If it was, what additional load do you want me to apply? And are you going to send me some shielded inductors to test? Let me know and I’ll jump on it for you.
73,
Juan
*From:* eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] *On Behalf Of *Louis McFadin *Sent:* Monday, July 16, 2007 6:10 PM *To:* Chuck Green *Cc:* Dave Black ((Work)); Dave Black ((Home)); David Smith; AMSAT Eagle; Samsonoff@Mac. Com; Juan.Rivera ((Work)) *Subject:* [eagle] Re: CAN-Do-Too! ??????????
Chuck,
Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock.
I see no inherent reason for not using them.
Lou McFadin
W5DID
w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a
couple of years ago (three?), someone approached me after the CAN-Do!
talk that Stephen and I gave to ask why we weren't using the
higher-density connectors that put 15 pins in the same shell size as the
9-pin version of the series we have been using... and followed up by
sending me what looked like mil/aero-spec samples of such a part that I
probably still have in my basement somewhere. I'm sorry that I can't
recall at all who that person was, but it was someone who claimed to be
using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time
soon, so I didn't take any action on this suggestion. If we're going to
revisit the design and think we need more than 9 pins, it might be worth
investigating higher density connectors like that?
Bdale
What is the value of the inductor at hand? Jim
Chuck Green wrote:
Hi Juan,
I think you are referring to an e-mail I sent out. It was simply a suggestion to verify the hypothesis that the power supply is in a low power idle mode and hence the 5kHz you were seeing. It really doesn't matter if someone is going to redesign the power supply anyway.
I don't have any shielded inductors to send you. There may not be any such thing in the same footprint as the inductor used. But even if it has to be cobbled in somehow, it would be a good test to run. If anyone has such an inductor, or knows the part number of such a device, it might be worth getting one. But again, if someone is going to redesign the power supply anyway, I would assume they will at least use a toroid, and possibly a shielded one.
Chuck
Juan Rivera wrote:
Chuck,
I seem to recall that you wanted me to try loading down the CAN-Do switcher to see if the frequency went up. Was that you? I can’t find the email. If it was, what additional load do you want me to apply? And are you going to send me some shielded inductors to test? Let me know and I’ll jump on it for you.
73,
Juan
*From:* eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] *On Behalf Of *Louis McFadin *Sent:* Monday, July 16, 2007 6:10 PM *To:* Chuck Green *Cc:* Dave Black ((Work)); Dave Black ((Home)); David Smith; AMSAT Eagle; Samsonoff@Mac. Com; Juan.Rivera ((Work)) *Subject:* [eagle] Re: CAN-Do-Too! ??????????
Chuck,
Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock.
I see no inherent reason for not using them.
Lou McFadin
W5DID
w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a
couple of years ago (three?), someone approached me after the CAN-Do!
talk that Stephen and I gave to ask why we weren't using the
higher-density connectors that put 15 pins in the same shell size as the
9-pin version of the series we have been using... and followed up by
sending me what looked like mil/aero-spec samples of such a part that I
probably still have in my basement somewhere. I'm sorry that I can't
recall at all who that person was, but it was someone who claimed to be
using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time
soon, so I didn't take any action on this suggestion. If we're going to
revisit the design and think we need more than 9 pins, it might be worth
investigating higher density connectors like that?
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
470 uH Chuck
Jim Sanford wrote:
What is the value of the inductor at hand? Jim
Chuck Green wrote:
Hi Juan,
I think you are referring to an e-mail I sent out. It was simply a suggestion to verify the hypothesis that the power supply is in a low power idle mode and hence the 5kHz you were seeing. It really doesn't matter if someone is going to redesign the power supply anyway.
I don't have any shielded inductors to send you. There may not be any such thing in the same footprint as the inductor used. But even if it has to be cobbled in somehow, it would be a good test to run. If anyone has such an inductor, or knows the part number of such a device, it might be worth getting one. But again, if someone is going to redesign the power supply anyway, I would assume they will at least use a toroid, and possibly a shielded one.
Chuck
Juan Rivera wrote:
Chuck,
I seem to recall that you wanted me to try loading down the CAN-Do switcher to see if the frequency went up. Was that you? I can’t find the email. If it was, what additional load do you want me to apply? And are you going to send me some shielded inductors to test? Let me know and I’ll jump on it for you.
73,
Juan
*From:* eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] *On Behalf Of *Louis McFadin *Sent:* Monday, July 16, 2007 6:10 PM *To:* Chuck Green *Cc:* Dave Black ((Work)); Dave Black ((Home)); David Smith; AMSAT Eagle; Samsonoff@Mac. Com; Juan.Rivera ((Work)) *Subject:* [eagle] Re: CAN-Do-Too! ??????????
Chuck,
Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock.
I see no inherent reason for not using them.
Lou McFadin
W5DID
w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a
couple of years ago (three?), someone approached me after the CAN-Do!
talk that Stephen and I gave to ask why we weren't using the
higher-density connectors that put 15 pins in the same shell size as the
9-pin version of the series we have been using... and followed up by
sending me what looked like mil/aero-spec samples of such a part that I
probably still have in my basement somewhere. I'm sorry that I can't
recall at all who that person was, but it was someone who claimed to be
using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time
soon, so I didn't take any action on this suggestion. If we're going to
revisit the design and think we need more than 9 pins, it might be worth
investigating higher density connectors like that?
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Check,
OK. I just ordered some parts I need to look into the ripple but I forgot about this. I'll wait to see what comes up with the supply...
Juan
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Monday, July 16, 2007 7:28 PM To: juan-rivera@sbcglobal.net Cc: 'Dave Black ((Work))'; 'David Smith'; 'AMSAT Eagle'; 'Samsonoff@Mac. Com'; 'Louis McFadin' Subject: Re: CAN-Do-Too!
Hi Juan,
I think you are referring to an e-mail I sent out. It was simply a suggestion to verify the hypothesis that the power supply is in a low power idle mode and hence the 5kHz you were seeing. It really doesn't matter if someone is going to redesign the power supply anyway.
I don't have any shielded inductors to send you. There may not be any such thing in the same footprint as the inductor used. But even if it has to be cobbled in somehow, it would be a good test to run. If anyone has such an inductor, or knows the part number of such a device, it might be worth getting one. But again, if someone is going to redesign the power supply anyway, I would assume they will at least use a toroid, and possibly a shielded one.
Chuck
Juan Rivera wrote:
Chuck,
I seem to recall that you wanted me to try loading down the CAN-Do switcher to see if the frequency went up. Was that you? I can't find the email. If it was, what additional load do you want me to apply? And are you going to send me some shielded inductors to test? Let me know and I'll jump on it for you.
73,
Juan
*From:* eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] *On Behalf Of *Louis McFadin *Sent:* Monday, July 16, 2007 6:10 PM *To:* Chuck Green *Cc:* Dave Black ((Work)); Dave Black ((Home)); David Smith; AMSAT Eagle; Samsonoff@Mac. Com; Juan.Rivera ((Work)) *Subject:* [eagle] Re: CAN-Do-Too! ??????????
Chuck,
Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock.
I see no inherent reason for not using them.
Lou McFadin
W5DID
w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a
couple of years ago (three?), someone approached me after the CAN-Do!
talk that Stephen and I gave to ask why we weren't using the
higher-density connectors that put 15 pins in the same shell size as the
9-pin version of the series we have been using... and followed up by
sending me what looked like mil/aero-spec samples of such a part that I
probably still have in my basement somewhere. I'm sorry that I can't
recall at all who that person was, but it was someone who claimed to be
using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time
soon, so I didn't take any action on this suggestion. If we're going to
revisit the design and think we need more than 9 pins, it might be worth
investigating higher density connectors like that?
Bdale
Thanks, Lou.
I don't know of any reason not to use them either. Obviously, it needs to meet our mounting configuration requirement so the new mechanical design can meet the objectives I stated earlier. This means it must mount on the edge of a PCB. I think the HD15-D has three rows of pins so I'm not sure how this can work, but I haven't looked at the various parts available so maybe this problem has been solved.
If we are going to seriously consider using HD connectors I think we need the blessing of AMSAT's VP of Engineering and the EAGLE project coordinator. This would be true for any change that would be pervasive in the satellite.
I am a little disappointed that there have not been any comments regarding the changes I saw as being made with a new design. Additions/changes/questions/etc. I don't think we should do a new design without this discussion. Maybe people feel these issues have been well covered in the past. If so, a simple "looks good to me" would be helpful.
And no one has stepped up to say they are well qualified and will design a new power supply. Without this, I don't see a new design happening, but maybe.
And finally, I see that no one has dared touch the subject of parts procurement I raised.
Obviously, most of these comments are really meant for the Cc list.
Thanks, Chuck
Louis McFadin wrote:
Chuck, Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock. I see no inherent reason for not using them.
Lou McFadin W5DID w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
Chuck,
My comments might have been buried in the flurry of email a while back. Things seem a bit quieter now so here they are:
1) Don't get too far into a redesign until a top-level EMI requirement is created. This can't be done properly until prototype solar panel power converters are fabricated and tested. I would work to create a new power supply with a switching frequency of at least 500 kHz while you wait however. This will make filtering much easier, the filter components will be smaller, and any spurs that make it into the receiver will be outside the passband of the IF.
2) The EMI requirements for radiated and conducted emissions and susceptibility should flow out of that test data and not be guesses.
3) Once we have an EMI requirement then tradeoffs need to be considered between the CAN-Do module and the enclosure - one or two compartment? Sheet metal or milled construction? The results of that tradeoff study will determine how much room you have to work with, how much front panel space, and how much shielding and filtering are required.
If I had my way the enclosure would be a two-cell milled enclosure with all the RF and IF exiting out the side of the rear cell. The CAN-Do module and the Receiver switching power supply would both be located in the first cell with feed-thru filtering in the common bulkhead between cells (all digital power in the front and all analog in the rear). That would mean that the CAN-Do connector would be the only connector on the front of the case. If that were true then the only reason to change connectors would be to save weight or increase reliability. It would also mean that the existing CAN-Do PCB footprint would be fine as it is.
In my presentation I will suggest that the next revision of the 70 cm receiver should be postponed until all of these issues are resolved.
73,
Juan
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Chuck Green Sent: Monday, July 16, 2007 7:47 PM To: Louis McFadin Cc: Dave Black ((Work)); Dave Black ((Home)); David Smith; AMSAT Eagle; Samsonoff@Mac. Com; Juan.Rivera ((Work)) Subject: [eagle] Re: CAN-Do-Too! ??????????
Thanks, Lou.
I don't know of any reason not to use them either. Obviously, it needs to meet our mounting configuration requirement so the new mechanical design can meet the objectives I stated earlier. This means it must mount on the edge of a PCB. I think the HD15-D has three rows of pins so I'm not sure how this can work, but I haven't looked at the various parts available so maybe this problem has been solved.
If we are going to seriously consider using HD connectors I think we need the blessing of AMSAT's VP of Engineering and the EAGLE project coordinator. This would be true for any change that would be pervasive in the satellite.
I am a little disappointed that there have not been any comments regarding the changes I saw as being made with a new design. Additions/changes/questions/etc. I don't think we should do a new design without this discussion. Maybe people feel these issues have been well covered in the past. If so, a simple "looks good to me" would be helpful.
And no one has stepped up to say they are well qualified and will design a new power supply. Without this, I don't see a new design happening, but maybe.
And finally, I see that no one has dared touch the subject of parts procurement I raised.
Obviously, most of these comments are really meant for the Cc list.
Thanks, Chuck
Louis McFadin wrote:
Chuck, Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock. I see no inherent reason for not using them.
Lou McFadin W5DID w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Hi Juan,
I agree that specifications prior to design would be helpful (required?). But as far as the EMI issues are concerned, we do seem to have a chicken/egg problem. And I'm not sure it is practical to design a widget that meets the requirements of receiver modules. Most modules simply don't need anything nearly this good. But we should do everything practical to accommodate receiver modules, and maybe meet their requirements completely.
Thanks, Chuck
Juan Rivera wrote:
Chuck,
My comments might have been buried in the flurry of email a while back. Things seem a bit quieter now so here they are:
- Don't get too far into a redesign until a top-level EMI requirement is
created. This can't be done properly until prototype solar panel power converters are fabricated and tested. I would work to create a new power supply with a switching frequency of at least 500 kHz while you wait however. This will make filtering much easier, the filter components will be smaller, and any spurs that make it into the receiver will be outside the passband of the IF.
- The EMI requirements for radiated and conducted emissions and
susceptibility should flow out of that test data and not be guesses.
- Once we have an EMI requirement then tradeoffs need to be considered
between the CAN-Do module and the enclosure - one or two compartment? Sheet metal or milled construction? The results of that tradeoff study will determine how much room you have to work with, how much front panel space, and how much shielding and filtering are required.
If I had my way the enclosure would be a two-cell milled enclosure with all the RF and IF exiting out the side of the rear cell. The CAN-Do module and the Receiver switching power supply would both be located in the first cell with feed-thru filtering in the common bulkhead between cells (all digital power in the front and all analog in the rear). That would mean that the CAN-Do connector would be the only connector on the front of the case. If that were true then the only reason to change connectors would be to save weight or increase reliability. It would also mean that the existing CAN-Do PCB footprint would be fine as it is.
In my presentation I will suggest that the next revision of the 70 cm receiver should be postponed until all of these issues are resolved.
73,
Juan
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Chuck Green Sent: Monday, July 16, 2007 7:47 PM To: Louis McFadin Cc: Dave Black ((Work)); Dave Black ((Home)); David Smith; AMSAT Eagle; Samsonoff@Mac. Com; Juan.Rivera ((Work)) Subject: [eagle] Re: CAN-Do-Too! ??????????
Thanks, Lou.
I don't know of any reason not to use them either. Obviously, it needs to meet our mounting configuration requirement so the new mechanical design can meet the objectives I stated earlier. This means it must mount on the edge of a PCB. I think the HD15-D has three rows of pins so I'm not sure how this can work, but I haven't looked at the various parts available so maybe this problem has been solved.
If we are going to seriously consider using HD connectors I think we need the blessing of AMSAT's VP of Engineering and the EAGLE project coordinator. This would be true for any change that would be pervasive in the satellite.
I am a little disappointed that there have not been any comments regarding the changes I saw as being made with a new design. Additions/changes/questions/etc. I don't think we should do a new design without this discussion. Maybe people feel these issues have been well covered in the past. If so, a simple "looks good to me" would be helpful.
And no one has stepped up to say they are well qualified and will design a new power supply. Without this, I don't see a new design happening, but maybe.
And finally, I see that no one has dared touch the subject of parts procurement I raised.
Obviously, most of these comments are really meant for the Cc list.
Thanks, Chuck
Louis McFadin wrote:
Chuck, Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock. I see no inherent reason for not using them.
Lou McFadin W5DID w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Chuck,
Forgive this long email...
SInce everything is interrelated the only way to deal with it is from a system engineering perspective (in my opinion). You can't design the various subsystems with each group working in a vacuum. If you do, this is what happens.
For example: I've researched the maximum amount of bending that should be allowed on a SMT circuit board. AVX, the capacitor manufacturer, suggests a maximum bend radius spec for SMT circuit boards of 60 inches. That works out to 0.0084" maximum deflection over any 1" segment. That's about the thickness of three sheets of paper. The tolerances of the existing sheet metal enclosure with separate heat sinks and multiple swaged-on stand-offs is way too loose, by at least an order of magnitude. The enclosure I have is also warped and flexes. To me that means we need a milled enclosure...
If we're going to do that we might as well do it right and make it into two separate cells with noisy digital circuits in the front and analog in the back...
If we do that then you probably don't have to worry too much about radiated emissions or changing the PCB form factor or connector...
Filtering conducted EMI would rise to the top of the list of concerns. Moving the switching frequecies of all the supplies up as high as possible would ease the filtering burden on everything on the satellite and tend to push any spurs out of the passband. And so forth and so on...
Once we had some hard data on the amount and characteristics of the conducted EMI from the power distribution point, then John could start designing in the necessary EMI filtering and CPB layout to fit into the box and meet the yet to be determined EMI susceptability requirement for the receiver. If his design didn't look like it would be able to meet the requiement then there would be some push-back to the power distrubution subsystem to clean up their radiated EMI, etc.
I guess the bottom line would be that since you can't know the radiated and conducted EMI susceptability of everything that may end up connected to the CAN-Do module, all you can do is try to make it as clean as you can and get the switching frequency as high as possible. By the way, I just looked up the Maxim converter you're using and it looks like it's very lightly loaded which would explain wny its running at 5 kHz instead of the 200 kHz they spec. I spent some time looking for a better choice and couldn't find anything, but I don't know what you requirements are.
73,
Juan
On 7/17/07, Chuck Green greencl@mindspring.com wrote:
Hi Juan,
I agree that specifications prior to design would be helpful (required?). But as far as the EMI issues are concerned, we do seem to have a chicken/egg problem. And I'm not sure it is practical to design a widget that meets the requirements of receiver modules. Most modules simply don't need anything nearly this good. But we should do everything practical to accommodate receiver modules, and maybe meet their requirements completely.
Thanks, Chuck
Juan Rivera wrote:
Chuck,
My comments might have been buried in the flurry of email a while back. Things seem a bit quieter now so here they are:
- Don't get too far into a redesign until a top-level EMI requirement
is
created. This can't be done properly until prototype solar panel power converters are fabricated and tested. I would work to create a new
power
supply with a switching frequency of at least 500 kHz while you wait however. This will make filtering much easier, the filter components
will
be smaller, and any spurs that make it into the receiver will be outside
the
passband of the IF.
- The EMI requirements for radiated and conducted emissions and
susceptibility should flow out of that test data and not be guesses.
- Once we have an EMI requirement then tradeoffs need to be considered
between the CAN-Do module and the enclosure - one or two
compartment? Sheet
metal or milled construction? The results of that tradeoff study will determine how much room you have to work with, how much front panel
space,
and how much shielding and filtering are required.
If I had my way the enclosure would be a two-cell milled enclosure with
all
the RF and IF exiting out the side of the rear cell. The CAN-Do module
and
the Receiver switching power supply would both be located in the first
cell
with feed-thru filtering in the common bulkhead between cells (all
digital
power in the front and all analog in the rear). That would mean that
the
CAN-Do connector would be the only connector on the front of the
case. If
that were true then the only reason to change connectors would be to
save
weight or increase reliability. It would also mean that the existing
CAN-Do
PCB footprint would be fine as it is.
In my presentation I will suggest that the next revision of the 70 cm receiver should be postponed until all of these issues are resolved.
73,
Juan
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf
Of
Chuck Green Sent: Monday, July 16, 2007 7:47 PM To: Louis McFadin Cc: Dave Black ((Work)); Dave Black ((Home)); David Smith; AMSAT Eagle; Samsonoff@Mac. Com; Juan.Rivera ((Work)) Subject: [eagle] Re: CAN-Do-Too! ??????????
Thanks, Lou.
I don't know of any reason not to use them either. Obviously, it needs to meet our mounting configuration requirement so the new mechanical design can meet the objectives I stated earlier. This means it must mount on the edge of a PCB. I think the HD15-D has three rows of pins so I'm not sure how this can work, but I haven't looked at the various parts available so maybe this problem has been solved.
If we are going to seriously consider using HD connectors I think we need the blessing of AMSAT's VP of Engineering and the EAGLE project coordinator. This would be true for any change that would be pervasive in the satellite.
I am a little disappointed that there have not been any comments regarding the changes I saw as being made with a new design. Additions/changes/questions/etc. I don't think we should do a new design without this discussion. Maybe people feel these issues have been well covered in the past. If so, a simple "looks good to me" would be helpful.
And no one has stepped up to say they are well qualified and will design a new power supply. Without this, I don't see a new design happening, but maybe.
And finally, I see that no one has dared touch the subject of parts procurement I raised.
Obviously, most of these comments are really meant for the Cc list.
Thanks, Chuck
Louis McFadin wrote:
Chuck, Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock. I see no inherent reason for not using them.
Lou McFadin W5DID w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as
the
9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that
I
probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to
be
using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going
to
revisit the design and think we need more than 9 pins, it might be
worth
investigating higher density connectors like that?
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Juan:
You keep commenting on the flexure of the PCB and relate it to the module hardware that you have in hand. It is my very greatly considered opinion that the baseplate that you have has been modified (butchered) to allow for the soldering of the CAN 40pin connector and this has created not only reduced sections in this plate, but probably has also distorted the plate considerable. Such distortions in all likelihood have created a non-normal flexure condition in that particular plate. As such, your opinion of the design has been biased, and that is unfortunate. It seems to me that you should try to acquire an E05 21 base plate that is in "stock" condition. I don't have any in hand here in Florida, or I would have sent it to you some time ago. These parts, unfortunately are in a limited supply at this time.
'73,
Dick Jansson, KD1K
mailto:kd1k@amsat.org kd1k@amsat.org
mailto:kd1k@arrl.net kd1k@arrl.net
Dick,
You could be correct although I wouldn't call it butchered. I enlarged the holes using my milling machine, a few thousandths of an inch at a time. But aside from the altered state of this base plate I think there are other issues to address. It may come to pass that two compartments are required to deal with the radiated EMI from the CAN-Do module. I think it will be very hard to partition this enclosure into two RF-tight compartments using sheet metal. I also think the AVX guide specifying no more than 0.0038" flex in any one-inch segment of the PCB might be hard to meet with this enclosure. AVX is one of the largest manufacturers of ceramic chip capacitors in the world so I believe they know what they are talking about. If anyone disagrees and wants to put out another argument for maximum SMT PCB flex I'd be interested to see it.
Anyway my opinions are just that. Once the dust settles and there is an EMI requirement and a PCB flex requirement, a determination can be made to see if the existing enclosure meets the requirements. If it does then there is no need to change it. That removes all the subjective opinions out of the decision loop. You hold everything up to the peer-reviewed requirements, run some peer-reviewed tests, and either it passes of it fails. The same goes for the CAN-Do module and the Receiver. At least that's the way I'm used to doing things at work.
73,
Juan
_____
From: Dick Jansson-rr [mailto:rjansson@cfl.rr.com] Sent: Tuesday, July 17, 2007 11:36 AM To: 'Juan Rivera'; 'Chuck Green' Cc: 'David Smith'; 'Dave Black ((Work))'; 'Dave Black ((Home))'; 'Louis McFadin'; 'AMSAT Eagle'; 'Samsonoff@Mac. Com'; 'Juan.Rivera ((Work))' Subject: RE: [eagle] Re: CAN-Do Suggestions from Juan
Juan:
You keep commenting on the flexure of the PCB and relate it to the module hardware that you have in hand. It is my very greatly considered opinion that the baseplate that you have has been modified (butchered) to allow for the soldering of the CAN 40pin connector and this has created not only reduced sections in this plate, but probably has also distorted the plate considerable. Such distortions in all likelihood have created a non-normal flexure condition in that particular plate. As such, your opinion of the design has been biased, and that is unfortunate. It seems to me that you should try to acquire an E05 21 base plate that is in "stock" condition. I don't have any in hand here in Florida, or I would have sent it to you some time ago. These parts, unfortunately are in a limited supply at this time.
'73,
Dick Jansson, KD1K
kd1k@amsat.org
kd1k@arrl.net
DIck: Do you know where any exist? Let's get them in Juan's hand and SEE. 73, Jim
Dick Jansson-rr wrote:
Juan:
You keep commenting on the flexure of the PCB and relate it to the module hardware that you have in hand. It is my very greatly considered opinion that the baseplate that you have has been modified (butchered) to allow for the soldering of the CAN 40pin connector and this has created not only reduced sections in this plate, but probably has also distorted the plate considerable. Such distortions in all likelihood have created a non-normal flexure condition in that particular plate. As such, your opinion of the design has been biased, and that is unfortunate. It seems to me that you should try to acquire an E05 21 base plate that is in "stock" condition. I don't have any in hand here in Florida, or I would have sent it to you some time ago. These parts, unfortunately are in a limited supply at this time.
'73,
Dick Jansson, KD1K
kd1k@amsat.org mailto:kd1k@amsat.org
kd1k@arrl.net mailto:kd1k@arrl.net
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Jim:
You and others have the modules that have been constructed. I have no idea where they are located...
'73,
Dick Jansson, KD1K
mailto:kd1k@amsat.org kd1k@amsat.org
mailto:kd1k@arrl.net kd1k@arrl.net
From: Jim Sanford [mailto:wb4gcs@amsat.org] Sent: Wednesday, 18 July, 2007 00.40 To: Dick Jansson-rr Cc: 'Juan Rivera'; 'Chuck Green'; 'David Smith'; 'Dave Black ((Work))'; 'Dave Black ((Home))'; 'Louis McFadin'; 'AMSAT Eagle'; 'Samsonoff@Mac. Com'; 'Juan.Rivera ((Work))' Subject: Re: [eagle] Re: CAN-Do Suggestions from Juan
DIck: Do you know where any exist? Let's get them in Juan's hand and SEE. 73, Jim
Dick Jansson-rr wrote:
Juan:
You keep commenting on the flexure of the PCB and relate it to the module hardware that you have in hand. It is my very greatly considered opinion that the baseplate that you have has been modified (butchered) to allow for the soldering of the CAN 40pin connector and this has created not only reduced sections in this plate, but probably has also distorted the plate considerable. Such distortions in all likelihood have created a non-normal flexure condition in that particular plate. As such, your opinion of the design has been biased, and that is unfortunate. It seems to me that you should try to acquire an E05 21 base plate that is in "stock" condition. I don't have any in hand here in Florida, or I would have sent it to you some time ago. These parts, unfortunately are in a limited supply at this time.
'73,
Dick Jansson, KD1K
kd1k@amsat.org
kd1k@arrl.net
_____
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Team: Some comments on this thread, as I indicated earlier.
In no particular order:
" . . working in a vacuum." To not do so is why we have EaglePedia, and why I have been pushing for requirements and sharing of lessons learned. The harsh reality is that Juan and his team have been testing some of our stuff in new ways, and we're learning things. Perhaps we could/should have learned some of these things in the past, I don't know. We didn't, but we know them now, so let's press ahead.
Regarding the board flexing issue: Juan, please add this to your lessons learned. It would be a welcome addition to the component selection talk that Lyle gave at Pittsburgh. In the mean time, please extract all the things that you've learned we should do differently into a text document that I can add to the lessons learned sub page from my project management page. I'll get Dave to post, this is all good stuff.
Milled enclosure: Bob Davis is looking into that. I've asked Dick Jansson to locate an unmodified sheet metal enclosure to get into Juan's hands for evaluation. Many considerations here, let's make decisions based on EVALUATION.
EMI: We need requirements, but nobody has stepped up to write or extract. My threat (grin) to dig out the MIL-SPEC was properly incinerated. So, we still have no requirements. I offer the following "top level" EMI requirements, based on my earlier post regarding the 3 things it takes to have EMI: 1. Every potential EMI source (like switching power supplies) should be as quiet and well shielded as reasonably posible. 2. Every potential EMI victim should be as immune to conducted and radiated (other than on-channel thru the antenna) as reasonably possible I'll leave it to guys like Tom Clark to tell me what exponent we should attach to the value of this in the aggregate of many sources and victims, I just know that attention to the basics on a per module basis will make our lives much easier at integration/testing time.
We also need to standardize on IF output levels from RX modules and input levels from SDX to TX modules. Volunteers?
I think the above provides all the guidance we need to proceed with an electrical redesign of the U RX based on what we've learned so far. We'll need Bob's input on housing studies and we'll need to assess what the CAN-Do! team is up to before committing to PCboard layout and construction. Juan thinks we should wait until some top-level specs are better refined; we'll come through this discussion.
Regarding the CAN-Do widgets: The team has offered to do a redesign. I'm reluctant to get too carried away on this. We've learned some things that we'd like to change regarding the power supply, but the rest of it works, and we should not toss that. So, this is an area where I very strongly feel that incremental improvement is in order, not a wholesale redesign. My sense is that the power supply noise issues we've discovered IN TESTING were not anticipated by design folks who are not necessarily power supply experts. (Bdale just confirmed this on the phone.) Now that we have them, we're seeking such experts. We may get some input soon from someone who is such an expert who knows somebody who knows somebody who is on the team. If any of the rest of you have such expertise or know somebody who has it, please step up to the plate. I'm gratified at the willingness of the CAN-Do! team to do whatever it takes, but DO NOT want to toss the baby with the bath water -- we then start over, and cannot afford that in time, intellectual effort, or $$ Part of this discussion is the recent conversation regarding high density connectors. If we need them and they're acceptable, so be it. Some seem to think this is a big deal, I do not -- it's a technical issue to be evaluated and dealt with.
One commentor expressed disappointment about silence regarding these changes and lack of direction from "management". I have been following this conversation closely, but have not weighed in since I had no new thoughts or extraordinary value to add. Rest assured, I follow these issues closely, and try not to weigh in unless I have something significant to say. My silence to this point should be interpreted as satisfaction with the conversation and apparent direction. If ever you think I should weigh in and am not, ask the explicit question.
Chuck asked if someone would pursue alternative inductor components to reduce radiated noise. I have asked Juan to see of Project Oscar would take this on. I think there is tremendous value in testing with substitues of this single component.
Finally: SYMPOSIUM It is CRITICALLY important that we demonstrate something this year. We need it to dispel doubts and we need it to encourage fund-raising. Our hosts, the Wireless Association fo the South Hills (WASH) have committed to helping us do this. They will provide a 30+ foot tower on a trailer, antennas, coax, and I'll provide a power supply. We have a working U-band RX, and may have a better one. Bob McGwier assures me that we'll have a working SDX to demonstrate. I'll get a 2m TX for it to drive at significant power. This will allow us to demonstrate Eagle in the hotel and in the surrounding area -- vital for publicity and fundraising. We also need to show IHU and CAN-Do!, ifthey're working and sending telemetry on the "downlink", so much the better!
We have much to do in a few short months. Let's get on with it.
Thanks & 73, Jim wb4gcs@amsat.org
Juan Rivera wrote:
Chuck,
Forgive this long email...
SInce everything is interrelated the only way to deal with it is from a system engineering perspective (in my opinion). You can't design the various subsystems with each group working in a vacuum. If you do, this is what happens.
For example: I've researched the maximum amount of bending that should be allowed on a SMT circuit board. AVX, the capacitor manufacturer, suggests a maximum bend radius spec for SMT circuit boards of 60 inches. That works out to 0.0084" maximum deflection over any 1" segment. That's about the thickness of three sheets of paper. The tolerances of the existing sheet metal enclosure with separate heat sinks and multiple swaged-on stand-offs is way too loose, by at least an order of magnitude. The enclosure I have is also warped and flexes. To me that means we need a milled enclosure...
If we're going to do that we might as well do it right and make it into two separate cells with noisy digital circuits in the front and analog in the back...
If we do that then you probably don't have to worry too much about radiated emissions or changing the PCB form factor or connector...
Filtering conducted EMI would rise to the top of the list of concerns. Moving the switching frequecies of all the supplies up as high as possible would ease the filtering burden on everything on the satellite and tend to push any spurs out of the passband. And so forth and so on...
Once we had some hard data on the amount and characteristics of the conducted EMI from the power distribution point, then John could start designing in the necessary EMI filtering and CPB layout to fit into the box and meet the yet to be determined EMI susceptability requirement for the receiver. If his design didn't look like it would be able to meet the requiement then there would be some push-back to the power distrubution subsystem to clean up their radiated EMI, etc.
I guess the bottom line would be that since you can't know the radiated and conducted EMI susceptability of everything that may end up connected to the CAN-Do module, all you can do is try to make it as clean as you can and get the switching frequency as high as possible. By the way, I just looked up the Maxim converter you're using and it looks like it's very lightly loaded which would explain wny its running at 5 kHz instead of the 200 kHz they spec. I spent some time looking for a better choice and couldn't find anything, but I don't know what you requirements are.
73,
Juan
On 7/17/07, *Chuck Green* <greencl@mindspring.com mailto:greencl@mindspring.com> wrote:
Hi Juan, I agree that specifications prior to design would be helpful (required?). But as far as the EMI issues are concerned, we do seem to have a chicken/egg problem. And I'm not sure it is practical to design a widget that meets the requirements of receiver modules. Most modules simply don't need anything nearly this good. But we should do everything practical to accommodate receiver modules, and maybe meet their requirements completely. Thanks, Chuck Juan Rivera wrote: > Chuck, > > My comments might have been buried in the flurry of email a while back. > Things seem a bit quieter now so here they are: > > 1) Don't get too far into a redesign until a top-level EMI requirement is > created. This can't be done properly until prototype solar panel power > converters are fabricated and tested. I would work to create a new power > supply with a switching frequency of at least 500 kHz while you wait > however. This will make filtering much easier, the filter components will > be smaller, and any spurs that make it into the receiver will be outside the > passband of the IF. > > 2) The EMI requirements for radiated and conducted emissions and > susceptibility should flow out of that test data and not be guesses. > > 3) Once we have an EMI requirement then tradeoffs need to be considered > between the CAN-Do module and the enclosure - one or two compartment? Sheet > metal or milled construction? The results of that tradeoff study will > determine how much room you have to work with, how much front panel space, > and how much shielding and filtering are required. > > If I had my way the enclosure would be a two-cell milled enclosure with all > the RF and IF exiting out the side of the rear cell. The CAN-Do module and > the Receiver switching power supply would both be located in the first cell > with feed-thru filtering in the common bulkhead between cells (all digital > power in the front and all analog in the rear). That would mean that the > CAN-Do connector would be the only connector on the front of the case. If > that were true then the only reason to change connectors would be to save > weight or increase reliability. It would also mean that the existing CAN-Do > PCB footprint would be fine as it is. > > In my presentation I will suggest that the next revision of the 70 cm > receiver should be postponed until all of these issues are resolved. > > 73, > > Juan > > > > -----Original Message----- > From: eagle-bounces@amsat.org <mailto:eagle-bounces@amsat.org> [mailto:eagle-bounces@amsat.org <mailto:eagle-bounces@amsat.org>] On Behalf Of > Chuck Green > Sent: Monday, July 16, 2007 7:47 PM > To: Louis McFadin > Cc: Dave Black ((Work)); Dave Black ((Home)); David Smith; AMSAT Eagle; > Samsonoff@Mac. Com; Juan.Rivera ((Work)) > Subject: [eagle] Re: CAN-Do-Too! ?????????? > > Thanks, Lou. > > I don't know of any reason not to use them either. Obviously, it needs > to meet our mounting configuration requirement so the new mechanical > design can meet the objectives I stated earlier. This means it must > mount on the edge of a PCB. I think the HD15-D has three rows of pins > so I'm not sure how this can work, but I haven't looked at the various > parts available so maybe this problem has been solved. > > If we are going to seriously consider using HD connectors I think we > need the blessing of AMSAT's VP of Engineering and the EAGLE project > coordinator. This would be true for any change that would be pervasive > in the satellite. > > I am a little disappointed that there have not been any comments > regarding the changes I saw as being made with a new design. > Additions/changes/questions/etc. I don't think we should do a new > design without this discussion. Maybe people feel these issues have > been well covered in the past. If so, a simple "looks good to me" would > be helpful. > > And no one has stepped up to say they are well qualified and will design > a new power supply. Without this, I don't see a new design happening, > but maybe. > > And finally, I see that no one has dared touch the subject of parts > procurement I raised. > > Obviously, most of these comments are really meant for the Cc list. > > Thanks, > Chuck > > Louis McFadin wrote: > >> Chuck, >> Mouser has a very large selection of D-sub connectors including the >> high density versions. Most are in stock. >> I see no inherent reason for not using them. >> >> Lou McFadin >> W5DID >> w5did@mac.com <mailto:w5did@mac.com> <mailto:w5did@mac.com <mailto:w5did@mac.com>> >> >> >> On Jul 16, 2007, at 7:19 PM, Chuck Green wrote: >> >> >>> I have had one experience with the high density D connectors. They >>> were much larger pin count than 9 or 15! After someone absolutely >>> insisted that we use them I did the board lay out. Turned out that >>> they were *totally* unavailable!!! I did the board layout >>> again@#$%&^* using standard Sub-D's. That was a number of years ago >>> so I would hope things have changed. If someone is absolutely >>> confident they can obtain the parts we need then I'm not at all >>> opposed to using them (remember, I'm not volunteering to do parts >>> procurement for this project; this is a good time to use someone >>> that's good at parts procurement). >>> >>> While at Goddard for P3D vib test I noticed NASA satellites using >>> standard Sub-D's. That was also a few years ago. Anyone know of >>> High Density Sub-D's being used on other satellites? >>> >>> Chuck >>> >>> Bdale Garbee wrote: >>> >>>> On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote: >>>> >>>> >>>> >>>>> The sub-miniature D connector series has served us well. If anyone >>>>> has *experience* with something they think might be a better >>>>> choice, we'd love to hear about it. >>>>> >>>>> >>>> At the AMSAT annual meeting that was held near Washington, D.C., a >>>> couple of years ago (three?), someone approached me after the CAN-Do! >>>> talk that Stephen and I gave to ask why we weren't using the >>>> higher-density connectors that put 15 pins in the same shell size as the >>>> 9-pin version of the series we have been using... and followed up by >>>> sending me what looked like mil/aero-spec samples of such a part that I >>>> probably still have in my basement somewhere. I'm sorry that I can't >>>> recall at all who that person was, but it was someone who claimed to be >>>> using such connectors professionally with good results. >>>> >>>> At the time, we weren't likely to be redesigning the units any time >>>> soon, so I didn't take any action on this suggestion. If we're going to >>>> revisit the design and think we need more than 9 pins, it might be worth >>>> investigating higher density connectors like that? >>>> >>>> Bdale >>>> >>>> >>>> >>>> > _______________________________________________ > Via the Eagle mailing list courtesy of AMSAT-NA > Eagle@amsat.org <mailto:Eagle@amsat.org> > http://amsat.org/mailman/listinfo/eagle > > > >
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Jim and gang,
I have a bit of new information for you regarding the CAN-Do step-down converter:
The Maxim 1836 step-down converter is designed to deliver output currents of up to 125 milliamps, but in this circuit it is only supplying 11 mills. The spec sheet shows that the efficiency and the switching frequency both drop off badly at that low output current. It's pretty clear that this IC is not the ideal choice for this very small load. I can think of several alternatives:
1) Replace the noisy switching downconverter with a linear regulator and remove all traces of generated EMI
2) Find another more suitable step-down converter and design a new circuit and a new PCB
3) At least for the 70 cm Receiver, disconnect the CAN-Do step-down converter and power the CAN-Do module from the +5 volt receiver supply. It shouldn't even notice another 11 mills.
Let's assume for the moment that we end up with a two-compartment enclosure. What if we just disable the CAN-Do module's step-down converter and create a small PCB that would attach to the 40-pin header and be the home for the power supplies for whatever was in the other side of the enclosure - in this case the receiver analog circuitry. The CAN-Do module would get its power from that little board and so would the receiver. In the case of this receiver we could put all the power supplies on a PCB about the size of a large postage stamp.
Don, KD6IRE amplifies on my idea and suggests that the digital compartment be placed off to the side - just wide enough to allow the existing CAN-Do module to fit. The main compartment would then be an 'L' shape, but with access to the front panel. All RF and IF I/O from the rear compartment would come up the leg on the "L", with SMA connectors all located on one side of the CAN-Do D connector.
Again speaking only from the perspective of the 70 cm receiver, I think this would require the least amount of redesign and result in a pretty clean passband. The benefits would be:
1) No major modifications to the CAN-Do module required (same PCB and same connector)
2) No connectors out the side or the top creating wiring headaches
3) No more 5 kHz radiated or conducted CAN-Do EMI inside the enclosure or propagated back up the DC power lines (5 kHz spurs completely gone)
4) Moves the 157 kHz receiver switching power supply to the separate compartment in the front on that little daughter board and gets rid of that spur in the passband
5) Minor modifications to the enclosure - just another internal sheet metal piece
6) The Receiver PCB form factor could remain the same or it could change to the "L" shape, depending on what works best.
This still leaves the issue of flex unresolved and this suggestion might not work for every project but it seems like it might be worth trying.
73,
Juan
P.S. Maxim 1836 link --> http://datasheets.maxim-ic.com/en/ds/MAX1836-MAX1837.pdf
Juan:
One difficulty in your suggested "little daughter board" is that while the circuitry may not take much space, getting the cooling of that PCB to the module baseplate may require much more volume and it is restrictive as to where you place this daughter board. In the current design of the URx that is one of the three areas needing the added heat sinks.
Dick Jansson, KD1K
mailto:kd1k@amsat.org kd1k@amsat.org
mailto:kd1k@arrl.net kd1k@arrl.net
From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Juan Rivera Sent: Wednesday, 18 July, 2007 05.06 To: 'Jim Sanford' Cc: 'David Smith'; 'Dave Black ((Work))'; 'Dave Black ((Home))'; 'Louis McFadin'; 'AMSAT Eagle'; 'Samsonoff@Mac. Com'; 'Juan.Rivera ((Work))' Subject: [eagle] Re: Jim's comments
(snip)
What if we just disable the CAN-Do module's step-down converter and create a small PCB that would attach to the 40-pin header and be the home for the power supplies for whatever was in the other side of the enclosure - in this case the receiver analog circuitry. The CAN-Do module would get its power from that little board and so would the receiver. In the case of this receiver we could put all the power supplies on a PCB about the size of a large postage stamp.
1)
2) Moves the 157 kHz receiver switching power supply to the separate compartment in the front on that little daughter board and gets rid of that spur in the passband
(snip)
I guess I should have finished reading before I send my previous email. I'm trying to visualize this dual compartment idea which still provides connector face area to both compartments. See attached (as ppt or jpg). If heat is the issue of the power board, then we can make it a bigger postage stamp as necessary, right? But it would stay in the same compartment as CAN-DO. At first blush, I think this idea is better than having connections on 2 different walls of the module. bob Robert Davis KF4KSS
On 7/18/07, Dick Jansson-rr rjansson@cfl.rr.com wrote:
Juan:
One difficulty in your suggested "little daughter board" is that while the circuitry may not take much space, getting the cooling of that PCB to the module baseplate may require much more volume and it is restrictive as to where you place this daughter board. In the current design of the URx that is one of the three areas needing the added heat sinks.
Dick Jansson, KD1K
kd1k@amsat.org
kd1k@arrl.net
*From:* eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] *On Behalf Of *Juan Rivera *Sent:* Wednesday, 18 July, 2007 05.06 *To:* 'Jim Sanford' *Cc:* 'David Smith'; 'Dave Black ((Work))'; 'Dave Black ((Home))'; 'Louis McFadin'; 'AMSAT Eagle'; 'Samsonoff@Mac. Com'; 'Juan.Rivera ((Work))' *Subject:* [eagle] Re: Jim's comments
(snip)
What if we just disable the CAN-Do module's step-down converter and create a small PCB that would attach to the 40-pin header and be the home for the power supplies for whatever was in the other side of the enclosure – in this case the receiver analog circuitry. The CAN-Do module would get its power from that little board and so would the receiver. In the case of this receiver we could put all the power supplies on a PCB about the size of a large postage stamp.
Moves the 157 kHz receiver switching power supply to the separate
compartment in the front on that little daughter board and gets rid of that spur in the passband
(snip)
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Bob,
First of all I should warn everyone that I woke up this morning doubting my 11 milliamp CAN-Do power supply load figure. I was rushed last night and I want to recheck my work.
Also in this thread somewhere someone mentioned 0.008" as the max bend per 1" PCB segment. It's worse than that if you accept the AVX suggestion. Their number was 0.0038" I've written all this up in my AMSAT presentation and it's getting peer reviewed at the moment. I hope to get it out in the next week.
Bob, I think your sketch is more or less what we (the OSCAR group) are suggesting as a solution for the 70 cm Receiver. I'm not sure it will be a good universal solution, and if that 11 milliamp load ir correct then I think we could just dump the switching step-down converter on the CAN-Do module and completely eliminate the EMI emission problem by going to a linear regulator or tapping power off of the main PCB. That would side-step a potentially troubesome problem.
73, Juan
On 7/18/07, Robert Davis bob2leo@gmail.com wrote:
I guess I should have finished reading before I send my previous email. I'm trying to visualize this dual compartment idea which still provides connector face area to both compartments. See attached (as ppt or jpg). If heat is the issue of the power board, then we can make it a bigger postage stamp as necessary, right? But it would stay in the same compartment as CAN-DO. At first blush, I think this idea is better than having connections on 2 different walls of the module. bob Robert Davis KF4KSS
On 7/18/07, Dick Jansson-rr rjansson@cfl.rr.com wrote:
Juan:
One difficulty in your suggested "little daughter board" is that while the circuitry may not take much space, getting the cooling of that PCB to the module baseplate may require much more volume and it is restrictive as to where you place this daughter board. In the current design of the URx that is one of the three areas needing the added heat sinks.
Dick Jansson, KD1K
kd1k@amsat.org
kd1k@arrl.net
*From:* eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] *On Behalf Of *Juan Rivera *Sent:* Wednesday, 18 July, 2007 05.06 *To:* 'Jim Sanford' *Cc:* 'David Smith'; 'Dave Black ((Work))'; 'Dave Black ((Home))'; 'Louis McFadin'; 'AMSAT Eagle'; 'Samsonoff@Mac . Com'; 'Juan.Rivera((Work))' *Subject:* [eagle] Re: Jim's comments
(snip)
What if we just disable the CAN-Do module's step-down converter and create a small PCB that would attach to the 40-pin header and be the home for the power supplies for whatever was in the other side of the enclosure – in this case the receiver analog circuitry. The CAN-Do module would get its power from that little board and so would the receiver. In the case of this receiver we could put all the power supplies on a PCB about the size of a large postage stamp.
Moves the 157 kHz receiver switching power supply to the separate
compartment in the front on that little daughter board and gets rid of that spur in the passband
(snip)
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
All: I'm not going to say much on this, because I want the discussion to flow, and then for John to make recommendations that we can peer reivew re the redesign.
I will say this: Juan makes an interesting proposal, which will solve much of the EMI issue for weak signal receivers. I still think we need to reduce, as much as reasonably possible, the noise generated, radiated, and conducted by the CAN-Do! widget under all postulated uses in Eagle. There are many reasons why this is just a good idea.
73, Jim wb4gcs@amsat.org
Juan Rivera wrote:
Jim and gang,
I have a bit of new information for you regarding the CAN-Do step-down converter:
The Maxim 1836 step-down converter is designed to deliver output currents of up to 125 milliamps, but in this circuit it is only supplying 11 mills. The spec sheet shows that the efficiency and the switching frequency both drop off badly at that low output current. It's pretty clear that this IC is not the ideal choice for this very small load. I can think of several alternatives:
Replace the noisy switching downconverter with a linearregulator and remove all traces of generated EMI
Find another more suitable step-down converter and design anew circuit and a new PCB
At least for the 70 cm Receiver, disconnect the CAN-Dostep-down converter and power the CAN-Do module from the +5 volt receiver supply. It shouldn't even notice another 11 mills.
Let's assume for the moment that we end up with a two-compartment enclosure. What if we just disable the CAN-Do module's step-down converter and create a small PCB that would attach to the 40-pin header and be the home for the power supplies for whatever was in the other side of the enclosure - in this case the receiver analog circuitry. The CAN-Do module would get its power from that little board and so would the receiver. In the case of this receiver we could put all the power supplies on a PCB about the size of a large postage stamp.
Don, KD6IRE amplifies on my idea and suggests that the digital compartment be placed off to the side - just wide enough to allow the existing CAN-Do module to fit. The main compartment would then be an 'L' shape, but with access to the front panel. All RF and IF I/O from the rear compartment would come up the leg on the "L", with SMA connectors all located on one side of the CAN-Do D connector.
Again speaking only from the perspective of the 70 cm receiver, I think this would require the least amount of redesign and result in a pretty clean passband. The benefits would be:
No major modifications to the CAN-Do module required (samePCB and same connector)
No connectors out the side or the top creating wiring headachesNo more 5 kHz radiated or conducted CAN-Do EMI inside theenclosure or propagated back up the DC power lines (5 kHz spurs completely gone)
Moves the 157 kHz receiver switching power supply to theseparate compartment in the front on that little daughter board and gets rid of that spur in the passband
Minor modifications to the enclosure - just another internalsheet metal piece
The Receiver PCB form factor could remain the same or it couldchange to the "L" shape, depending on what works best.
This still leaves the issue of flex unresolved and this suggestion might not work for every project but it seems like it might be worth trying.
73,
Juan
P.S. Maxim 1836 link à http://datasheets.maxim-ic.com/en/ds/MAX1836-MAX1837.pdf
Jim, Juan, and all, I'm sorry for not being active in this conversation earlier. I'm absolutely creamed at work. I forecast being at my maximum at work for about another week or two. I'll spare you the details. I am sure that we can redesign a module that is at least partially milled, that will maintain the flatness that Juan quotes from a vendor of .008" per 1". It really isn't that hard, but absolutely throws out the sheetmetal baseplate we've had until now. In my mind, for this one issue it's only a decision as to whether the entire module height is milled (and then there's just a simple flat cover) or whether the milled portion is part of the height of a module and a shorter "bent cover" is used. I think I'm favoring a milled module with simple flat cover. For the issue of the isolation of the CAN-DO in a separate compartment, this can be done and I guess I've seen it frequently with milled modules. I'd like to avoid it because it moves farther towards having truly customized modules, instead of a generic with minor connector or heatsink mods. For the issue of the RF connectors exiting the side of the module, this is potentially a larger issue. In our current arrangement, we have identified a connector face on the modules because all the modules are (potentially) packed side-by-side to consume a dimension of the spacecraft. If we had an accurate accounting of how many modules, and what sizes they are, then we might be able to say with confidence what gap is present between modules available for RF connections. I've attached a spreadsheet with the only accounting of modules that we've attempted and it's pretty old. The flip side of this would be: impose a requirement on mechanical to provide room for RF connectors on specific (or all) modules, and specify what the module sizes are and we can see where we stand. Maybe it would help to have an idea of what kind of protrusion from the side of a module we're talking about. 20mm? So, comments on the list of modules & sizes can get us started with determining what is available next to a module for RF. bob Robert Davis KF4KSS
On 7/17/07, Jim Sanford wb4gcs@amsat.org wrote:
Team: Some comments on this thread, as I indicated earlier.
In no particular order:
" . . working in a vacuum." To not do so is why we have EaglePedia, and why I have been pushing for requirements and sharing of lessons learned. The harsh reality is that Juan and his team have been testing some of our stuff in new ways, and we're learning things. Perhaps we could/should have learned some of these things in the past, I don't know. We didn't, but we know them now, so let's press ahead.
Regarding the board flexing issue: Juan, please add this to your lessons learned. It would be a welcome addition to the component selection talk that Lyle gave at Pittsburgh. In the mean time, please extract all the things that you've learned we should do differently into a text document that I can add to the lessons learned sub page from my project management page. I'll get Dave to post, this is all good stuff.
Milled enclosure: Bob Davis is looking into that. I've asked Dick Jansson to locate an unmodified sheet metal enclosure to get into Juan's hands for evaluation. Many considerations here, let's make decisions based on EVALUATION.
EMI: We need requirements, but nobody has stepped up to write or extract. My threat (grin) to dig out the MIL-SPEC was properly incinerated. So, we still have no requirements. I offer the following "top level" EMI requirements, based on my earlier post regarding the 3 things it takes to have EMI: 1. Every potential EMI source (like switching power supplies) should be as quiet and well shielded as reasonably posible. 2. Every potential EMI victim should be as immune to conducted and radiated (other than on-channel thru the antenna) as reasonably possible I'll leave it to guys like Tom Clark to tell me what exponent we should attach to the value of this in the aggregate of many sources and victims, I just know that attention to the basics on a per module basis will make our lives much easier at integration/testing time.
We also need to standardize on IF output levels from RX modules and input levels from SDX to TX modules. Volunteers?
I think the above provides all the guidance we need to proceed with an electrical redesign of the U RX based on what we've learned so far. We'll need Bob's input on housing studies and we'll need to assess what the CAN-Do! team is up to before committing to PCboard layout and construction. Juan thinks we should wait until some top-level specs are better refined; we'll come through this discussion.
Regarding the CAN-Do widgets: The team has offered to do a redesign. I'm reluctant to get too carried away on this. We've learned some things that we'd like to change regarding the power supply, but the rest of it works, and we should not toss that. So, this is an area where I very strongly feel that incremental improvement is in order, not a wholesale redesign. My sense is that the power supply noise issues we've discovered IN TESTING were not anticipated by design folks who are not necessarily power supply experts. (Bdale just confirmed this on the phone.) Now that we have them, we're seeking such experts. We may get some input soon from someone who is such an expert who knows somebody who knows somebody who is on the team. If any of the rest of you have such expertise or know somebody who has it, please step up to the plate. I'm gratified at the willingness of the CAN-Do! team to do whatever it takes, but DO NOT want to toss the baby with the bath water -- we then start over, and cannot afford that in time, intellectual effort, or $$ Part of this discussion is the recent conversation regarding high density connectors. If we need them and they're acceptable, so be it. Some seem to think this is a big deal, I do not -- it's a technical issue to be evaluated and dealt with.
One commentor expressed disappointment about silence regarding these changes and lack of direction from "management". I have been following this conversation closely, but have not weighed in since I had no new thoughts or extraordinary value to add. Rest assured, I follow these issues closely, and try not to weigh in unless I have something significant to say. My silence to this point should be interpreted as satisfaction with the conversation and apparent direction. If ever you think I should weigh in and am not, ask the explicit question.
Chuck asked if someone would pursue alternative inductor components to reduce radiated noise. I have asked Juan to see of Project Oscar would take this on. I think there is tremendous value in testing with substitues of this single component.
Finally: SYMPOSIUM It is CRITICALLY important that we demonstrate something this year. We need it to dispel doubts and we need it to encourage fund-raising. Our hosts, the Wireless Association fo the South Hills (WASH) have committed to helping us do this. They will provide a 30+ foot tower on a trailer, antennas, coax, and I'll provide a power supply. We have a working U-band RX, and may have a better one. Bob McGwier assures me that we'll have a working SDX to demonstrate. I'll get a 2m TX for it to drive at significant power. This will allow us to demonstrate Eagle in the hotel and in the surrounding area -- vital for publicity and fundraising. We also need to show IHU and CAN-Do!, ifthey're working and sending telemetry on the "downlink", so much the better!
We have much to do in a few short months. Let's get on with it.
Thanks & 73, Jim wb4gcs@amsat.org
Juan Rivera wrote:
Chuck,
Forgive this long email...
SInce everything is interrelated the only way to deal with it is from a system engineering perspective (in my opinion). You can't design the various subsystems with each group working in a vacuum. If you do, this is what happens.
For example: I've researched the maximum amount of bending that should be allowed on a SMT circuit board. AVX, the capacitor manufacturer, suggests a maximum bend radius spec for SMT circuit boards of 60 inches. That works out to 0.0084" maximum deflection over any 1" segment. That's about the thickness of three sheets of paper. The tolerances of the existing sheet metal enclosure with separate heat sinks and multiple swaged-on stand-offs is way too loose, by at least an order of magnitude. The enclosure I have is also warped and flexes. To me that means we need a milled enclosure...
If we're going to do that we might as well do it right and make it into two separate cells with noisy digital circuits in the front and analog in the back...
If we do that then you probably don't have to worry too much about radiated emissions or changing the PCB form factor or connector...
Filtering conducted EMI would rise to the top of the list of concerns. Moving the switching frequecies of all the supplies up as high as possible would ease the filtering burden on everything on the satellite and tend to push any spurs out of the passband. And so forth and so on...
Once we had some hard data on the amount and characteristics of the conducted EMI from the power distribution point, then John could start designing in the necessary EMI filtering and CPB layout to fit into the box and meet the yet to be determined EMI susceptability requirement for the receiver. If his design didn't look like it would be able to meet the requiement then there would be some push-back to the power distrubution subsystem to clean up their radiated EMI, etc.
I guess the bottom line would be that since you can't know the radiated and conducted EMI susceptability of everything that may end up connected to the CAN-Do module, all you can do is try to make it as clean as you can and get the switching frequency as high as possible. By the way, I just looked up the Maxim converter you're using and it looks like it's very lightly loaded which would explain wny its running at 5 kHz instead of the 200 kHz they spec. I spent some time looking for a better choice and couldn't find anything, but I don't know what you requirements are.
73,
Juan
On 7/17/07, Chuck Green greencl@mindspring.com wrote:
Hi Juan,
I agree that specifications prior to design would be helpful (required?). But as far as the EMI issues are concerned, we do seem to have a chicken/egg problem. And I'm not sure it is practical to design a widget that meets the requirements of receiver modules. Most modules simply don't need anything nearly this good. But we should do everything practical to accommodate receiver modules, and maybe meet their requirements completely.
Thanks, Chuck
Juan Rivera wrote:
Chuck,
My comments might have been buried in the flurry of email a while
back.
Things seem a bit quieter now so here they are:
- Don't get too far into a redesign until a top-level EMI requirement
is
created. This can't be done properly until prototype solar panel
power
converters are fabricated and tested. I would work to create a new
power
supply with a switching frequency of at least 500 kHz while you wait however. This will make filtering much easier, the filter components
will
be smaller, and any spurs that make it into the receiver will be
outside the
passband of the IF.
- The EMI requirements for radiated and conducted emissions and
susceptibility should flow out of that test data and not be guesses.
- Once we have an EMI requirement then tradeoffs need to be
considered
between the CAN-Do module and the enclosure - one or two
compartment? Sheet
metal or milled construction? The results of that tradeoff study will
determine how much room you have to work with, how much front panel
space,
and how much shielding and filtering are required.
If I had my way the enclosure would be a two-cell milled enclosure
with all
the RF and IF exiting out the side of the rear cell. The CAN-Do
module and
the Receiver switching power supply would both be located in the first
cell
with feed-thru filtering in the common bulkhead between cells (all
digital
power in the front and all analog in the rear). That would mean that
the
CAN-Do connector would be the only connector on the front of the
case. If
that were true then the only reason to change connectors would be to
save
weight or increase reliability. It would also mean that the existing
CAN-Do
PCB footprint would be fine as it is.
In my presentation I will suggest that the next revision of the 70 cm receiver should be postponed until all of these issues are resolved.
73,
Juan
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On
Behalf Of
Chuck Green Sent: Monday, July 16, 2007 7:47 PM To: Louis McFadin Cc: Dave Black ((Work)); Dave Black ((Home)); David Smith; AMSAT
Eagle;
Samsonoff@Mac. Com; Juan.Rivera ((Work)) Subject: [eagle] Re: CAN-Do-Too! ??????????
Thanks, Lou.
I don't know of any reason not to use them either. Obviously, it
needs
to meet our mounting configuration requirement so the new mechanical design can meet the objectives I stated earlier. This means it must mount on the edge of a PCB. I think the HD15-D has three rows of pins
so I'm not sure how this can work, but I haven't looked at the various parts available so maybe this problem has been solved.
If we are going to seriously consider using HD connectors I think we need the blessing of AMSAT's VP of Engineering and the EAGLE project coordinator. This would be true for any change that would be
pervasive
in the satellite.
I am a little disappointed that there have not been any comments regarding the changes I saw as being made with a new design. Additions/changes/questions/etc. I don't think we should do a new design without this discussion. Maybe people feel these issues have been well covered in the past. If so, a simple "looks good to me"
would
be helpful.
And no one has stepped up to say they are well qualified and will
design
a new power supply. Without this, I don't see a new design happening,
but maybe.
And finally, I see that no one has dared touch the subject of parts procurement I raised.
Obviously, most of these comments are really meant for the Cc list.
Thanks, Chuck
Louis McFadin wrote:
Chuck, Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock. I see no inherent reason for not using them.
Lou McFadin W5DID w5did@mac.com <mailto:w5did@mac.com >
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago
so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
> The sub-miniature D connector series has served us well. If
anyone
> has *experience* with something they think might be a better > choice, we'd love to hear about it. > > At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the
CAN-Do!
talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size
as the
9-pin version of the series we have been using... and followed up
by
sending me what looked like mil/aero-spec samples of such a part
that I
probably still have in my basement somewhere. I'm sorry that I
can't
recall at all who that person was, but it was someone who claimed
to be
using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time
soon, so I didn't take any action on this suggestion. If we're
going to
revisit the design and think we need more than 9 pins, it might be
worth
investigating higher density connectors like that?
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NAEagle@amsat.orghttp://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
As we consider flex stresses we also need to ensure we've considered the launch adapter specs for G-forces and are providing adequate support for the boards.
For ESPA: 10.6 G on all axis For ASAP5: X +/- 6 g Y +/- 6 g Z -7.5 g / +5.5 g
Lee-KU4OS
On Wednesday 18 July 2007 08:41:23 Robert Davis wrote:
Jim, Juan, and all, I'm sorry for not being active in this conversation earlier. I'm absolutely creamed at work. I forecast being at my maximum at work for about another week or two. I'll spare you the details. I am sure that we can redesign a module that is at least partially milled, that will maintain the flatness that Juan quotes from a vendor of .008" per 1". It really isn't that hard, but absolutely throws out the sheetmetal baseplate we've had until now. In my mind, for this one issue it's only a decision as to whether the entire module height is milled (and then there's just a simple flat cover) or whether the milled portion is part of the height of a module and a shorter "bent cover" is used. I think I'm favoring a milled module with simple flat cover. For the issue of the isolation of the CAN-DO in a separate compartment, this can be done and I guess I've seen it frequently with milled modules. I'd like to avoid it because it moves farther towards having truly customized modules, instead of a generic with minor connector or heatsink mods. For the issue of the RF connectors exiting the side of the module, this is potentially a larger issue. In our current arrangement, we have identified a connector face on the modules because all the modules are (potentially) packed side-by-side to consume a dimension of the spacecraft. If we had an accurate accounting of how many modules, and what sizes they are, then we might be able to say with confidence what gap is present between modules available for RF connections. I've attached a spreadsheet with the only accounting of modules that we've attempted and it's pretty old. The flip side of this would be: impose a requirement on mechanical to provide room for RF connectors on specific (or all) modules, and specify what the module sizes are and we can see where we stand. Maybe it would help to have an idea of what kind of protrusion from the side of a module we're talking about. 20mm? So, comments on the list of modules & sizes can get us started with determining what is available next to a module for RF. bob Robert Davis KF4KSS
On 7/17/07, Jim Sanford wb4gcs@amsat.org wrote:
Team: Some comments on this thread, as I indicated earlier.
In no particular order:
" . . working in a vacuum." To not do so is why we have EaglePedia, and why I have been pushing for requirements and sharing of lessons learned. The harsh reality is that Juan and his team have been testing some of our stuff in new ways, and we're learning things. Perhaps we could/should have learned some of these things in the past, I don't know. We didn't, but we know them now, so let's press ahead.
Regarding the board flexing issue: Juan, please add this to your lessons learned. It would be a welcome addition to the component selection talk that Lyle gave at Pittsburgh. In the mean time, please extract all the things that you've learned we should do differently into a text document that I can add to the lessons learned sub page from my project management page. I'll get Dave to post, this is all good stuff.
Milled enclosure: Bob Davis is looking into that. I've asked Dick Jansson to locate an unmodified sheet metal enclosure to get into Juan's hands for evaluation. Many considerations here, let's make decisions based on EVALUATION.
EMI: We need requirements, but nobody has stepped up to write or extract. My threat (grin) to dig out the MIL-SPEC was properly incinerated. So, we still have no requirements. I offer the following "top level" EMI requirements, based on my earlier post regarding the 3 things it takes to have EMI: 1. Every potential EMI source (like switching power supplies) should be as quiet and well shielded as reasonably posible. 2. Every potential EMI victim should be as immune to conducted and radiated (other than on-channel thru the antenna) as reasonably possible I'll leave it to guys like Tom Clark to tell me what exponent we should attach to the value of this in the aggregate of many sources and victims, I just know that attention to the basics on a per module basis will make our lives much easier at integration/testing time.
We also need to standardize on IF output levels from RX modules and input levels from SDX to TX modules. Volunteers?
I think the above provides all the guidance we need to proceed with an electrical redesign of the U RX based on what we've learned so far. We'll need Bob's input on housing studies and we'll need to assess what the CAN-Do! team is up to before committing to PCboard layout and construction. Juan thinks we should wait until some top-level specs are better refined; we'll come through this discussion.
Regarding the CAN-Do widgets: The team has offered to do a redesign. I'm reluctant to get too carried away on this. We've learned some things that we'd like to change regarding the power supply, but the rest of it works, and we should not toss that. So, this is an area where I very strongly feel that incremental improvement is in order, not a wholesale redesign. My sense is that the power supply noise issues we've discovered IN TESTING were not anticipated by design folks who are not necessarily power supply experts. (Bdale just confirmed this on the phone.) Now that we have them, we're seeking such experts. We may get some input soon from someone who is such an expert who knows somebody who knows somebody who is on the team. If any of the rest of you have such expertise or know somebody who has it, please step up to the plate. I'm gratified at the willingness of the CAN-Do! team to do whatever it takes, but DO NOT want to toss the baby with the bath water -- we then start over, and cannot afford that in time, intellectual effort, or $$ Part of this discussion is the recent conversation regarding high density connectors. If we need them and they're acceptable, so be it. Some seem to think this is a big deal, I do not -- it's a technical issue to be evaluated and dealt with.
One commentor expressed disappointment about silence regarding these changes and lack of direction from "management". I have been following this conversation closely, but have not weighed in since I had no new thoughts or extraordinary value to add. Rest assured, I follow these issues closely, and try not to weigh in unless I have something significant to say. My silence to this point should be interpreted as satisfaction with the conversation and apparent direction. If ever you think I should weigh in and am not, ask the explicit question.
Chuck asked if someone would pursue alternative inductor components to reduce radiated noise. I have asked Juan to see of Project Oscar would take this on. I think there is tremendous value in testing with substitues of this single component.
Finally: SYMPOSIUM It is CRITICALLY important that we demonstrate something this year. We need it to dispel doubts and we need it to encourage fund-raising. Our hosts, the Wireless Association fo the South Hills (WASH) have committed to helping us do this. They will provide a 30+ foot tower on a trailer, antennas, coax, and I'll provide a power supply. We have a working U-band RX, and may have a better one. Bob McGwier assures me that we'll have a working SDX to demonstrate. I'll get a 2m TX for it to drive at significant power. This will allow us to demonstrate Eagle in the hotel and in the surrounding area -- vital for publicity and fundraising. We also need to show IHU and CAN-Do!, ifthey're working and sending telemetry on the "downlink", so much the better!
We have much to do in a few short months. Let's get on with it.
Thanks & 73, Jim wb4gcs@amsat.org
Juan Rivera wrote:
Chuck,
Forgive this long email...
SInce everything is interrelated the only way to deal with it is from a system engineering perspective (in my opinion). You can't design the various subsystems with each group working in a vacuum. If you do, this is what happens.
For example: I've researched the maximum amount of bending that should be allowed on a SMT circuit board. AVX, the capacitor manufacturer, suggests a maximum bend radius spec for SMT circuit boards of 60 inches. That works out to 0.0084" maximum deflection over any 1" segment. That's about the thickness of three sheets of paper. The tolerances of the existing sheet metal enclosure with separate heat sinks and multiple swaged-on stand-offs is way too loose, by at least an order of magnitude. The enclosure I have is also warped and flexes. To me that means we need a milled enclosure...
If we're going to do that we might as well do it right and make it into two separate cells with noisy digital circuits in the front and analog in the back...
If we do that then you probably don't have to worry too much about radiated emissions or changing the PCB form factor or connector...
Filtering conducted EMI would rise to the top of the list of concerns. Moving the switching frequecies of all the supplies up as high as possible would ease the filtering burden on everything on the satellite and tend to push any spurs out of the passband. And so forth and so on...
Once we had some hard data on the amount and characteristics of the conducted EMI from the power distribution point, then John could start designing in the necessary EMI filtering and CPB layout to fit into the box and meet the yet to be determined EMI susceptability requirement for the receiver. If his design didn't look like it would be able to meet the requiement then there would be some push-back to the power distrubution subsystem to clean up their radiated EMI, etc.
I guess the bottom line would be that since you can't know the radiated and conducted EMI susceptability of everything that may end up connected to the CAN-Do module, all you can do is try to make it as clean as you can and get the switching frequency as high as possible. By the way, I just looked up the Maxim converter you're using and it looks like it's very lightly loaded which would explain wny its running at 5 kHz instead of the 200 kHz they spec. I spent some time looking for a better choice and couldn't find anything, but I don't know what you requirements are.
73,
Juan
The module design has been done with these forces in mind. The designer has been through the hoops associated with operating in this environment.
Dick Jansson, KD1K kd1k@amsat.org kd1k@arrl.net
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Lee McLamb Sent: Thursday, 19 July, 2007 02.57 To: eagle@amsat.org Cc: David Smith; Dave Black ((Work)); Dave Black ((Home)); Samsonoff@Mac. Com; Juan.Rivera ((Work)) Subject: [eagle] Re: CAN-Do Suggestions from Juan
As we consider flex stresses we also need to ensure we've considered the launch adapter specs for G-forces and are providing adequate support for the
boards.
For ESPA: 10.6 G on all axis For ASAP5: X +/- 6 g Y +/- 6 g Z -7.5 g / +5.5 g
Lee-KU4OS
On Wednesday 18 July 2007 08:41:23 Robert Davis wrote:
Jim, Juan, and all, I'm sorry for not being active in this conversation earlier. I'm
absolutely
creamed at work. I forecast being at my maximum at work for about another week or two. I'll spare you the details. I am sure that we can redesign a module that is at least partially milled, that will maintain the flatness that Juan quotes from a vendor of .008"
per
1". It really isn't that hard, but absolutely throws out the sheetmetal baseplate we've had until now. In my mind, for this one issue it's only a decision as to whether the entire module height is milled (and then
there's
just a simple flat cover) or whether the milled portion is part of the height of a module and a shorter "bent cover" is used. I think I'm
favoring
a milled module with simple flat cover. For the issue of the isolation of the CAN-DO in a separate compartment, this can be done and I guess I've seen it frequently with milled modules. I'd like to avoid it because it moves farther towards having truly customized modules, instead of a generic with minor connector or heatsink mods. For the issue of the RF connectors exiting the side of the module, this is potentially a larger issue. In our current arrangement, we have identified a connector face on the modules because all the modules are (potentially) packed side-by-side to consume a dimension of the
spacecraft.
If we had an accurate accounting of how many modules, and what sizes they are, then we might be able to say with confidence what gap is present between modules available for RF connections. I've attached a spreadsheet with the only accounting of modules that we've attempted and it's pretty old. The flip side of this would be: impose a requirement on mechanical to provide room for RF connectors on specific (or all) modules, and specify what the module sizes are and we can see where we stand. Maybe it would help to have an idea of what kind of protrusion from the side of a module we're talking about. 20mm? So, comments on the list of modules & sizes can get us started with determining what is available next to a module for RF. bob Robert Davis KF4KSS
On 7/17/07, Jim Sanford wb4gcs@amsat.org wrote:
Team: Some comments on this thread, as I indicated earlier.
In no particular order:
" . . working in a vacuum." To not do so is why we have EaglePedia, and why I have been pushing for requirements and sharing of lessons learned. The harsh reality is that Juan and his team have been testing some of
our
stuff in new ways, and we're learning things. Perhaps we could/should have learned some of these things in the past, I don't know. We didn't, but we know them now, so let's press ahead.
Regarding the board flexing issue: Juan, please add this to your
lessons
learned. It would be a welcome addition to the component selection talk that Lyle gave at Pittsburgh. In the mean time, please extract all the things that you've learned we should do differently into a text document that I can add to the lessons learned sub page from my project
management
page. I'll get Dave to post, this is all good stuff.
Milled enclosure: Bob Davis is looking into that. I've asked Dick Jansson to locate an unmodified sheet metal enclosure to get into Juan's hands for evaluation. Many considerations here, let's make decisions based on EVALUATION.
EMI: We need requirements, but nobody has stepped up to write or extract. My threat (grin) to dig out the MIL-SPEC was properly incinerated. So, we still have no requirements. I offer the following "top level" EMI requirements, based on my earlier post regarding the 3 things it takes to have EMI: 1. Every potential EMI source (like switching power supplies)
should
be as quiet and well shielded as reasonably posible. 2. Every potential EMI victim should be as immune to conducted and radiated (other than on-channel thru the antenna) as reasonably possible I'll leave it to guys like Tom Clark to tell me what exponent we should attach to the value of this in the aggregate of many sources and
victims,
I just know that attention to the basics on a per module basis will make our lives much easier at integration/testing time.
We also need to standardize on IF output levels from RX modules and
input
levels from SDX to TX modules. Volunteers?
I think the above provides all the guidance we need to proceed with an electrical redesign of the U RX based on what we've learned so far. We'll need Bob's input on housing studies and we'll need to assess what the CAN-Do! team is up to before committing to PCboard layout and construction. Juan thinks we should wait until some top-level specs are better refined; we'll come through this discussion.
Regarding the CAN-Do widgets: The team has offered to do a redesign. I'm reluctant to get too carried away on this. We've learned some
things
that we'd like to change regarding the power supply, but the rest of it works, and we should not toss that. So, this is an area where I very strongly feel that incremental improvement is in order, not a wholesale redesign. My sense is that the power supply noise issues we've discovered IN TESTING were not anticipated by design folks who are not necessarily power supply experts. (Bdale just confirmed this on the phone.) Now that we have them, we're seeking such experts. We may get some input soon from someone who is such an expert who knows somebody
who
knows somebody who is on the team. If any of the rest of you have such expertise or know somebody who has it, please step up to the plate. I'm gratified at the willingness of the CAN-Do! team to do whatever it
takes,
but DO NOT want to toss the baby with the bath water -- we then start over, and cannot afford that in time, intellectual effort, or $$ Part
of
this discussion is the recent conversation regarding high density connectors. If we need them and they're acceptable, so be it. Some
seem
to think this is a big deal, I do not -- it's a technical issue to be evaluated and dealt with.
One commentor expressed disappointment about silence regarding these changes and lack of direction from "management". I have been following this conversation closely, but have not weighed in since I had no new thoughts or extraordinary value to add. Rest assured, I follow these issues closely, and try not to weigh in unless I have something significant to say. My silence to this point should be interpreted as satisfaction with the conversation and apparent direction. If ever you think I should weigh in and am not, ask the explicit question.
Chuck asked if someone would pursue alternative inductor components to reduce radiated noise. I have asked Juan to see of Project Oscar would take this on. I think there is tremendous value in testing with substitues of this single component.
Finally: SYMPOSIUM It is CRITICALLY important that we demonstrate something this year. We need it to dispel doubts and we need it to encourage fund-raising. Our hosts, the Wireless Association fo the South Hills (WASH) have committed to helping us do this. They will provide a 30+ foot tower on a trailer, antennas, coax, and I'll provide a power supply. We have a working U-band RX, and may have a better one. Bob McGwier assures me that we'll have a working SDX to demonstrate. I'll get a 2m TX for it to drive at significant power. This will allow us to demonstrate Eagle in the hotel and in the surrounding area -- vital for publicity and fundraising. We also need to show IHU and CAN-Do!, ifthey're working and sending telemetry on the "downlink", so much the better!
We have much to do in a few short months. Let's get on with it.
Thanks & 73, Jim wb4gcs@amsat.org
Juan Rivera wrote:
Chuck,
Forgive this long email...
SInce everything is interrelated the only way to deal with it is from a system engineering perspective (in my opinion). You can't design the various subsystems with each group working in a vacuum. If you do, this is what happens.
For example: I've researched the maximum amount of bending that should be allowed on a SMT circuit board. AVX, the capacitor manufacturer, suggests a maximum bend radius spec for SMT circuit boards of 60 inches.
That works out to 0.0084" maximum deflection over any 1" segment.
That's
about the thickness of three sheets of paper. The tolerances of the existing sheet metal enclosure with separate heat sinks and multiple swaged-on stand-offs is way too loose, by at least an order of
magnitude.
The enclosure I have is also warped and flexes. To me that means we need a milled enclosure...
If we're going to do that we might as well do it right and make it into two separate cells with noisy digital circuits in the front and analog
in
the back...
If we do that then you probably don't have to worry too much about radiated emissions or changing the PCB form factor or connector...
Filtering conducted EMI would rise to the top of the list of concerns. Moving the switching frequecies of all the supplies up as high as possible would ease the filtering burden on everything on the satellite and tend to push any spurs out of the passband. And so forth and so on...
Once we had some hard data on the amount and characteristics of the conducted EMI from the power distribution point, then John could start designing in the necessary EMI filtering and CPB layout to fit into the box and meet the yet to be determined EMI susceptability requirement for the receiver. If his design didn't look like it would be able to meet the requiement then there would be some push-back to the power distrubution subsystem to clean up their radiated EMI, etc.
I guess the bottom line would be that since you can't know the radiated and conducted EMI susceptability of everything that may end up connected to the CAN-Do module, all you can do is try to make it as clean as you can and get the switching frequency as high as possible. By the way, I just looked up the Maxim converter you're using and it looks like it's very lightly loaded which would explain wny its running at 5 kHz instead of the 200 kHz they spec. I spent some time looking for a better choice and couldn't find anything, but I don't know what you requirements are.
73,
Juan
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Team: I'm going to weigh in later tonight after several notes in this thread, but want to respond to this ASAP.
I very strongly feel that we should try our best to get the CAN-Do! widget to work with receivers. I don't care if it's redesign, shielding, both, or whatever.
Rationale: In my demented mind, there are three mandatory requirements for EMI -- a source, a path (conducted or emitted), and a victim receptor. We will need to work on all three, but (to a point) working on the source has the most bang for the buck. I say this because, we might do a nice job of shielding a particular receiver, but if we ignore the source, we run a huge risk of unintended and unexpected/untested collateral effects -- like there being so much radiated noise that the noise floor at some antenna is unacceptable. Reducing source strength.reduces total radiated noise by a factor of however many widgets we fly.
That said, I'm ABSOLUTELY willing to be convinced that, "We've done this, we've spent that, any more is diminishing returne."
I truly feel that we should do our best to limit the source as part of an integrated attack on this issue.
More later tonight.
Thanks & 73, Jim wb4gcs@amsat.org
Chuck Green wrote:
Hi Juan,
I agree that specifications prior to design would be helpful (required?). But as far as the EMI issues are concerned, we do seem to have a chicken/egg problem. And I'm not sure it is practical to design a widget that meets the requirements of receiver modules. Most modules simply don't need anything nearly this good. But we should do everything practical to accommodate receiver modules, and maybe meet their requirements completely.
Thanks, Chuck
Juan Rivera wrote:
Chuck,
My comments might have been buried in the flurry of email a while back. Things seem a bit quieter now so here they are:
- Don't get too far into a redesign until a top-level EMI requirement is
created. This can't be done properly until prototype solar panel power converters are fabricated and tested. I would work to create a new power supply with a switching frequency of at least 500 kHz while you wait however. This will make filtering much easier, the filter components will be smaller, and any spurs that make it into the receiver will be outside the passband of the IF.
- The EMI requirements for radiated and conducted emissions and
susceptibility should flow out of that test data and not be guesses.
- Once we have an EMI requirement then tradeoffs need to be considered
between the CAN-Do module and the enclosure - one or two compartment? Sheet metal or milled construction? The results of that tradeoff study will determine how much room you have to work with, how much front panel space, and how much shielding and filtering are required.
If I had my way the enclosure would be a two-cell milled enclosure with all the RF and IF exiting out the side of the rear cell. The CAN-Do module and the Receiver switching power supply would both be located in the first cell with feed-thru filtering in the common bulkhead between cells (all digital power in the front and all analog in the rear). That would mean that the CAN-Do connector would be the only connector on the front of the case. If that were true then the only reason to change connectors would be to save weight or increase reliability. It would also mean that the existing CAN-Do PCB footprint would be fine as it is.
In my presentation I will suggest that the next revision of the 70 cm receiver should be postponed until all of these issues are resolved.
73,
Juan
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Chuck Green Sent: Monday, July 16, 2007 7:47 PM To: Louis McFadin Cc: Dave Black ((Work)); Dave Black ((Home)); David Smith; AMSAT Eagle; Samsonoff@Mac. Com; Juan.Rivera ((Work)) Subject: [eagle] Re: CAN-Do-Too! ??????????
Thanks, Lou.
I don't know of any reason not to use them either. Obviously, it needs to meet our mounting configuration requirement so the new mechanical design can meet the objectives I stated earlier. This means it must mount on the edge of a PCB. I think the HD15-D has three rows of pins so I'm not sure how this can work, but I haven't looked at the various parts available so maybe this problem has been solved.
If we are going to seriously consider using HD connectors I think we need the blessing of AMSAT's VP of Engineering and the EAGLE project coordinator. This would be true for any change that would be pervasive in the satellite.
I am a little disappointed that there have not been any comments regarding the changes I saw as being made with a new design. Additions/changes/questions/etc. I don't think we should do a new design without this discussion. Maybe people feel these issues have been well covered in the past. If so, a simple "looks good to me" would be helpful.
And no one has stepped up to say they are well qualified and will design a new power supply. Without this, I don't see a new design happening, but maybe.
And finally, I see that no one has dared touch the subject of parts procurement I raised.
Obviously, most of these comments are really meant for the Cc list.
Thanks, Chuck
Louis McFadin wrote:
Chuck, Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock. I see no inherent reason for not using them.
Lou McFadin W5DID w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Chuck:
Not that my opinion counts for anything in this issue, but I for one support the concept of edge mounting of the CAN module, using whatever connector is finally selected. The edge mounting would not of itself mandate the use of the HD connector as you will not really same much more space by its use. One issue related to the edge-mounted CAN module is a mechanical one, in that such a mounting presupposes a cantilevered mass of the CAN module supported by the connector, this is totally unacceptable as it would ring like a church bell under these conditions. The CAN module must be basically attached to a main PCB that brings the CAN module connector to the Connector Bracket, along with other connectors.
This edge mounting of the CAN module will also occupy space on the Connector Bracket that could also be used by other of the PCB's edge mounted connectors, and I am very sure that we will hear about that waste of connector space, too! To some degree, this is a no-win situation.....
Dick Jansson, KD1K kd1k@amsat.org kd1k@arrl.net
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Chuck Green Sent: Tuesday, 17 July, 2007 03.47 To: Louis McFadin Cc: Dave Black ((Work)); Dave Black ((Home)); David Smith; AMSAT Eagle; Samsonoff@Mac. Com; Juan.Rivera ((Work)) Subject: [eagle] Re: CAN-Do-Too! ??????????
(snip).
I am a little disappointed that there have not been any comments regarding the changes I saw as being made with a new design. Additions/changes/questions/etc. I don't think we should do a new design without this discussion. Maybe people feel these issues have been well covered in the past. If so, a simple "looks good to me" would be helpful.
(snip)
Thanks, Chuck
Are P3E and P5 also using our CAN-Do widgets? If so, we should be coordinating any change is design with them.
I would think that they would have the same concerns regarding RF noise as we do.
73,
Bill Tynan, W3XO
----- Original Message ----- From: "Chuck Green" greencl@mindspring.com To: "Louis McFadin" w5did@amsat.org Cc: "Dave Black ((Work))" dblack@mail.arc.nasa.gov; "Dave Black ((Home))" dblack1054@yahoo.com; "David Smith" w6te@msn.com; "AMSAT Eagle" eagle@amsat.org; "Samsonoff@Mac. Com" samsonoff@mac.com; "Juan.Rivera ((Work))" Juan.Rivera@gd-ais.com Sent: Monday, July 16, 2007 9:47 PM Subject: [eagle] Re: CAN-Do-Too! ??????????
Thanks, Lou.
I don't know of any reason not to use them either. Obviously, it needs to meet our mounting configuration requirement so the new mechanical design can meet the objectives I stated earlier. This means it must mount on the edge of a PCB. I think the HD15-D has three rows of pins so I'm not sure how this can work, but I haven't looked at the various parts available so maybe this problem has been solved.
If we are going to seriously consider using HD connectors I think we need the blessing of AMSAT's VP of Engineering and the EAGLE project coordinator. This would be true for any change that would be pervasive in the satellite.
I am a little disappointed that there have not been any comments regarding the changes I saw as being made with a new design. Additions/changes/questions/etc. I don't think we should do a new design without this discussion. Maybe people feel these issues have been well covered in the past. If so, a simple "looks good to me" would be helpful.
And no one has stepped up to say they are well qualified and will design a new power supply. Without this, I don't see a new design happening, but maybe.
And finally, I see that no one has dared touch the subject of parts procurement I raised.
Obviously, most of these comments are really meant for the Cc list.
Thanks, Chuck
Louis McFadin wrote:
Chuck, Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock. I see no inherent reason for not using them.
Lou McFadin W5DID w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Hi Bill,
Yes, they are using the same device. Both engineering and flight units have been delivered to them. I have heard nothing regarding their use. If they have had any issues with them, they have resolved them themselves.
My communications with them have been severely limited due to ITAR issues. I really despise this situation and am looking forward to the day that I can resume my normal very good working relations with them. It is unfortunate that our government is such an inhibitor of technical development and destroyer of international relations. Oops, I probably shouldn't have said that. It's all your fault for getting me started :)
Chuck
Bill Tynan wrote:
Are P3E and P5 also using our CAN-Do widgets? If so, we should be coordinating any change is design with them.
I would think that they would have the same concerns regarding RF noise as we do.
73,
Bill Tynan, W3XO
----- Original Message ----- From: "Chuck Green" greencl@mindspring.com To: "Louis McFadin" w5did@amsat.org Cc: "Dave Black ((Work))" dblack@mail.arc.nasa.gov; "Dave Black ((Home))" dblack1054@yahoo.com; "David Smith" w6te@msn.com; "AMSAT Eagle" eagle@amsat.org; "Samsonoff@Mac. Com" samsonoff@mac.com; "Juan.Rivera ((Work))" Juan.Rivera@gd-ais.com Sent: Monday, July 16, 2007 9:47 PM Subject: [eagle] Re: CAN-Do-Too! ??????????
Thanks, Lou.
I don't know of any reason not to use them either. Obviously, it needs to meet our mounting configuration requirement so the new mechanical design can meet the objectives I stated earlier. This means it must mount on the edge of a PCB. I think the HD15-D has three rows of pins so I'm not sure how this can work, but I haven't looked at the various parts available so maybe this problem has been solved.
If we are going to seriously consider using HD connectors I think we need the blessing of AMSAT's VP of Engineering and the EAGLE project coordinator. This would be true for any change that would be pervasive in the satellite.
I am a little disappointed that there have not been any comments regarding the changes I saw as being made with a new design. Additions/changes/questions/etc. I don't think we should do a new design without this discussion. Maybe people feel these issues have been well covered in the past. If so, a simple "looks good to me" would be helpful.
And no one has stepped up to say they are well qualified and will design a new power supply. Without this, I don't see a new design happening, but maybe.
And finally, I see that no one has dared touch the subject of parts procurement I raised.
Obviously, most of these comments are really meant for the Cc list.
Thanks, Chuck
Louis McFadin wrote:
Chuck, Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock. I see no inherent reason for not using them.
Lou McFadin W5DID w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Chuck:
I thought I remembered that they are using them as well, but I was out of the Eagle loop for a number of months. Just got back in in time to see all the EMI problems being unearthed.
Yes, ITAR is %$&@ nuisance. I tried to do something about it 6 years ago, but Sept. 20, 2001 (9 days after 9/11) was the wrong time to begin.
Our DL friends are certainly aware of the EMI situation our folks have uncovered.
73, Bill
----- Original Message ----- From: "Chuck Green" greencl@mindspring.com To: "Bill Tynan" btynan@beecreek.net Cc: "Louis McFadin" w5did@amsat.org; "Dave Black ((Work))" dblack@mail.arc.nasa.gov; "Dave Black ((Home))" dblack1054@yahoo.com; "David Smith" w6te@msn.com; "AMSAT Eagle" eagle@amsat.org; "Samsonoff@Mac. Com" samsonoff@mac.com; "Juan.Rivera ((Work))" Juan.Rivera@gd-ais.com Sent: Tuesday, July 17, 2007 10:05 AM Subject: Re: [eagle] Re: CAN-Do-Too! ??????????
Hi Bill,
Yes, they are using the same device. Both engineering and flight units have been delivered to them. I have heard nothing regarding their use. If they have had any issues with them, they have resolved them themselves.
My communications with them have been severely limited due to ITAR issues. I really despise this situation and am looking forward to the day that I can resume my normal very good working relations with them. It is unfortunate that our government is such an inhibitor of technical development and destroyer of international relations. Oops, I probably shouldn't have said that. It's all your fault for getting me started :)
Chuck
Bill Tynan wrote:
Are P3E and P5 also using our CAN-Do widgets? If so, we should be coordinating any change is design with them.
I would think that they would have the same concerns regarding RF noise as we do.
73,
Bill Tynan, W3XO
----- Original Message ----- From: "Chuck Green" greencl@mindspring.com To: "Louis McFadin" w5did@amsat.org Cc: "Dave Black ((Work))" dblack@mail.arc.nasa.gov; "Dave Black ((Home))" dblack1054@yahoo.com; "David Smith" w6te@msn.com; "AMSAT Eagle" eagle@amsat.org; "Samsonoff@Mac. Com" samsonoff@mac.com; "Juan.Rivera ((Work))" Juan.Rivera@gd-ais.com Sent: Monday, July 16, 2007 9:47 PM Subject: [eagle] Re: CAN-Do-Too! ??????????
Thanks, Lou.
I don't know of any reason not to use them either. Obviously, it needs to meet our mounting configuration requirement so the new mechanical design can meet the objectives I stated earlier. This means it must mount on the edge of a PCB. I think the HD15-D has three rows of pins so I'm not sure how this can work, but I haven't looked at the various parts available so maybe this problem has been solved.
If we are going to seriously consider using HD connectors I think we need the blessing of AMSAT's VP of Engineering and the EAGLE project coordinator. This would be true for any change that would be pervasive in the satellite.
I am a little disappointed that there have not been any comments regarding the changes I saw as being made with a new design. Additions/changes/questions/etc. I don't think we should do a new design without this discussion. Maybe people feel these issues have been well covered in the past. If so, a simple "looks good to me" would be helpful.
And no one has stepped up to say they are well qualified and will design a new power supply. Without this, I don't see a new design happening, but maybe.
And finally, I see that no one has dared touch the subject of parts procurement I raised.
Obviously, most of these comments are really meant for the Cc list.
Thanks, Chuck
Louis McFadin wrote:
Chuck, Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock. I see no inherent reason for not using them.
Lou McFadin W5DID w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
> The sub-miniature D connector series has served us well. If anyone > has *experience* with something they think might be a better > choice, we'd love to hear about it. >
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Their receiver module is long and skinny. Perhaps they have the RF and CAN bus connectors at different ends of the module.
73.
John KD6OZH
----- Original Message ----- From: "Chuck Green" greencl@mindspring.com To: "Bill Tynan" btynan@beecreek.net Cc: "David Smith" w6te@msn.com; "Dave Black ((Work))" dblack@mail.arc.nasa.gov; "Dave Black ((Home))" dblack1054@yahoo.com; "Louis McFadin" w5did@amsat.org; "AMSAT Eagle" eagle@amsat.org; "Samsonoff@Mac. Com" samsonoff@mac.com; "Juan.Rivera ((Work))" Juan.Rivera@gd-ais.com Sent: Tuesday, July 17, 2007 15:05 UTC Subject: [eagle] Re: CAN-Do-Too! ??????????
Hi Bill,
Yes, they are using the same device. Both engineering and flight units have been delivered to them. I have heard nothing regarding their use. If they have had any issues with them, they have resolved them themselves.
My communications with them have been severely limited due to ITAR issues. I really despise this situation and am looking forward to the day that I can resume my normal very good working relations with them. It is unfortunate that our government is such an inhibitor of technical development and destroyer of international relations. Oops, I probably shouldn't have said that. It's all your fault for getting me started :)
Chuck
Bill Tynan wrote:
Are P3E and P5 also using our CAN-Do widgets? If so, we should be coordinating any change is design with them.
I would think that they would have the same concerns regarding RF noise as we do.
73,
Bill Tynan, W3XO
----- Original Message ----- From: "Chuck Green" greencl@mindspring.com To: "Louis McFadin" w5did@amsat.org Cc: "Dave Black ((Work))" dblack@mail.arc.nasa.gov; "Dave Black ((Home))" dblack1054@yahoo.com; "David Smith" w6te@msn.com; "AMSAT Eagle" eagle@amsat.org; "Samsonoff@Mac. Com" samsonoff@mac.com; "Juan.Rivera ((Work))" Juan.Rivera@gd-ais.com Sent: Monday, July 16, 2007 9:47 PM Subject: [eagle] Re: CAN-Do-Too! ??????????
Thanks, Lou.
I don't know of any reason not to use them either. Obviously, it needs to meet our mounting configuration requirement so the new mechanical design can meet the objectives I stated earlier. This means it must mount on the edge of a PCB. I think the HD15-D has three rows of pins so I'm not sure how this can work, but I haven't looked at the various parts available so maybe this problem has been solved.
If we are going to seriously consider using HD connectors I think we need the blessing of AMSAT's VP of Engineering and the EAGLE project coordinator. This would be true for any change that would be pervasive in the satellite.
I am a little disappointed that there have not been any comments regarding the changes I saw as being made with a new design. Additions/changes/questions/etc. I don't think we should do a new design without this discussion. Maybe people feel these issues have been well covered in the past. If so, a simple "looks good to me" would be helpful.
And no one has stepped up to say they are well qualified and will design a new power supply. Without this, I don't see a new design happening, but maybe.
And finally, I see that no one has dared touch the subject of parts procurement I raised.
Obviously, most of these comments are really meant for the Cc list.
Thanks, Chuck
Louis McFadin wrote:
Chuck, Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock. I see no inherent reason for not using them.
Lou McFadin W5DID w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
> The sub-miniature D connector series has served us well. If anyone > has *experience* with something they think might be a better > choice, we'd love to hear about it. >
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
The only concern with a smaller contact would be current carrying capacity for the power and ground pins.
73,
John KD6OZH
----- Original Message ----- From: "Chuck Green" greencl@mindspring.com To: "Louis McFadin" w5did@amsat.org Cc: "Dave Black ((Work))" dblack@mail.arc.nasa.gov; "Dave Black ((Home))" dblack1054@yahoo.com; "David Smith" w6te@msn.com; "AMSAT Eagle" eagle@amsat.org; "Samsonoff@Mac. Com" samsonoff@mac.com; "Juan.Rivera ((Work))" Juan.Rivera@gd-ais.com Sent: Tuesday, July 17, 2007 02:47 UTC Subject: [eagle] Re: CAN-Do-Too! ??????????
Thanks, Lou.
I don't know of any reason not to use them either. Obviously, it needs to meet our mounting configuration requirement so the new mechanical design can meet the objectives I stated earlier. This means it must mount on the edge of a PCB. I think the HD15-D has three rows of pins so I'm not sure how this can work, but I haven't looked at the various parts available so maybe this problem has been solved.
If we are going to seriously consider using HD connectors I think we need the blessing of AMSAT's VP of Engineering and the EAGLE project coordinator. This would be true for any change that would be pervasive in the satellite.
I am a little disappointed that there have not been any comments regarding the changes I saw as being made with a new design. Additions/changes/questions/etc. I don't think we should do a new design without this discussion. Maybe people feel these issues have been well covered in the past. If so, a simple "looks good to me" would be helpful.
And no one has stepped up to say they are well qualified and will design a new power supply. Without this, I don't see a new design happening, but maybe.
And finally, I see that no one has dared touch the subject of parts procurement I raised.
Obviously, most of these comments are really meant for the Cc list.
Thanks, Chuck
Louis McFadin wrote:
Chuck, Mouser has a very large selection of D-sub connectors including the high density versions. Most are in stock. I see no inherent reason for not using them.
Lou McFadin W5DID w5did@mac.com mailto:w5did@mac.com
On Jul 16, 2007, at 7:19 PM, Chuck Green wrote:
I have had one experience with the high density D connectors. They were much larger pin count than 9 or 15! After someone absolutely insisted that we use them I did the board lay out. Turned out that they were *totally* unavailable!!! I did the board layout again@#$%&^* using standard Sub-D's. That was a number of years ago so I would hope things have changed. If someone is absolutely confident they can obtain the parts we need then I'm not at all opposed to using them (remember, I'm not volunteering to do parts procurement for this project; this is a good time to use someone that's good at parts procurement).
While at Goddard for P3D vib test I noticed NASA satellites using standard Sub-D's. That was also a few years ago. Anyone know of High Density Sub-D's being used on other satellites?
Chuck
Bdale Garbee wrote:
On Tue, 2007-07-10 at 09:02 -0700, Chuck Green wrote:
The sub-miniature D connector series has served us well. If anyone has *experience* with something they think might be a better choice, we'd love to hear about it.
At the AMSAT annual meeting that was held near Washington, D.C., a couple of years ago (three?), someone approached me after the CAN-Do! talk that Stephen and I gave to ask why we weren't using the higher-density connectors that put 15 pins in the same shell size as the 9-pin version of the series we have been using... and followed up by sending me what looked like mil/aero-spec samples of such a part that I probably still have in my basement somewhere. I'm sorry that I can't recall at all who that person was, but it was someone who claimed to be using such connectors professionally with good results.
At the time, we weren't likely to be redesigning the units any time soon, so I didn't take any action on this suggestion. If we're going to revisit the design and think we need more than 9 pins, it might be worth investigating higher density connectors like that?
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Hi Chuck
Anyone know of High Density Sub-D's being used on other satellites?
ESA use them frequently. During the many days I've spent locked away at ESA's integration clean rooms, I've nosed a number of designs that have used high density sub-Ds.
Howard
Hi Howard,
This and other things I have now heard have me convinced there is no reason not to use them.
Thanks, Chuck
Howard Long wrote:
Hi Chuck
Anyone know of High Density Sub-D's being used on other satellites?
ESA use them frequently. During the many days I've spent locked away at ESA's integration clean rooms, I've nosed a number of designs that have used high density sub-Ds.
Howard
And the project manager has no objections. (Somebody was concerned . . . ) Not that I'd intervene in such a technical detail unless I really saw it going south or bad wrong -- not likely with this crowd. 73, Jim
Chuck Green wrote:
Hi Howard,
This and other things I have now heard have me convinced there is no reason not to use them.
Thanks, Chuck
Howard Long wrote:
Hi Chuck
Anyone know of High Density Sub-D's being used on other satellites?
ESA use them frequently. During the many days I've spent locked away at ESA's integration clean rooms, I've nosed a number of designs that have used high density sub-Ds.
Howard
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
ESA use them frequently. During the many days I've spent locked away at ESA's integration clean rooms, I've nosed a number of designs that have used high density sub-Ds.
They're referred to here https://escies.org/ReadArticle?docId=115 (ESCIES is ESA's bible for space qual. parts).
Howard
participants (19)
-
Alan Bloom -
Bdale Garbee -
Bill Ress -
Bill Tynan -
Chuck Green -
Dick Jansson-rr -
Dick-rr
-
Howard Long -
Howard Long -
Jim Sanford -
John B. Stephensen -
Juan Rivera -
Lee McLamb -
Louis McFadin -
n1al＠cds1.net
-
Rick Hambly (W2GPS) -
Robert Davis -
Robert McGwier -
Stephen Moraco