CAN-Do noise abatement plan and questions
Good morning Stephen,
I do have a few questions. Thanks for asking!
1) What if the CAN-Do module suffers a failure that causes a current overload? Is it protected by a fuse? The next generation receiver should continue to function as long as it has power. An overload in either unit should not cause the other to fail.
2) Do you have any information of previous efforts to reduce CAN-Do noise by either shielding the module or replacing the inductor with a shielded version?
3) Do you have a shielded inductor that I could swap for the existing one if that proved necessary?
4) Have you designed a circuit that would allow temperature to be determined inside the receiver PCB itself, and not just on the CAN-Do module? This will be important, especially if the receiver is split into two separate enclosures.
My plan is to desolder the CAN-Do module from the receiver PCB today and move the receiver PCB to the enclosure's rear set of mounts. This will put about 2-inches of space between the two. I'll make up two interconnecting cables - one just long enough to attach the two while in the case, and one that is a foot or two long, assuming that I can find the parts I need and don't have to solder the cable to the two units. I can use that long cable to try some troubleshooting. I'll use that CAN-Do's noisy inductor as the noise source and move it around over the receiver to see what affect it has. Perhaps I can find the area that is the most susceptible to noise that way.
I think the next receiver could use the entire available board space to:
1) Put distance between the two modules
2) Further isolate the CAN-Do module with a shield if necessary
3) Add power supply input filtering and input current overload protection
4) Include CAN-Do data line filtering if that turns out to be necessary
5) Add a temperature sensor in the vicinity of the SAW filters, and another on the second PCB if it gets split into two sections
One last question. How do I reduce the heartbeat timing below three seconds? I couldn't find any way to do that using the net controller. I'd like to confirm that the jump in frequency I see in the CAN-Do module's 5 kHz noise every three seconds goes away.
73,
Juan
_____
From: [email protected] [mailto:[email protected]] On Behalf Of Stephen Moraco Sent: Tuesday, June 12, 2007 7:21 PM To: Juan Rivera; Juan Rivera Cc: Jim Sanford; Bdale Garbee Subject: late to tonight's meeting
Juan,
Sorry I missed your presentation/discussion tonight.
Any questions/issues for me re: CAN Do! ?
Regards, Stephen --
On Wed, 2007-06-13 at 05:06 -0700, Juan Rivera wrote:
Good morning Stephen,
I happen to be online earlier than Stephen today, due to being in Atlanta on business, so let me provide some replies and he can chime in later if I miss anything.
And by the way, sorry about missing the TeamSpeak meeting last night. I was at dinner with a number of customers in Atlanta, and then realized the notebook I'm using now does not have a built-in microphone (and I'm not in the habit of traveling with a headset... should probably fix that!).
What if the CAN-Do module suffers a failure that causes acurrent overload? Is it protected by a fuse? The next generation receiver should continue to function as long as it has power. An overload in either unit should not cause the other to fail.
There is no fuse on the CAN-Do! widget. A sufficiently bad short would probably cause a trace to cook acting as a fuse, but all of the active circuitry is downstream of the switching regulator and thus fairly well isolated from the spacecraft power bus in case of failure anyway. Since you'll be bypassing the power switch on the CAN-Do! widget anyway, I don't think we have any significant coupled-failure scenarios.
Do you have any information of previous efforts to reduceCAN-Do noise by either shielding the module or replacing the inductor with a shielded version?
No. As I indicated in my email the other day, you are the first person integrating a CAN-Do! widget with an RF payload module... at least that we've had any feedback from.
Do you have a shielded inductor that I could swap for theexisting one if that proved necessary?
No. And frankly, solutions that involve *any* modification of the CAN-Do! widget boards at this point are going to be problematic, since all of the flight units have already been manufactured and functionally tested. That's not to say that we *can't* change the CAN-Do! widgets, but given the relatively small number of the total that are likely to end up in RF modules, choosing a solution that allows the CAN-Do! widget board to be used as-is may be a better systems-level design decision.
Have you designed a circuit that would allow temperature to bedetermined inside the receiver PCB itself, and not just on the CAN-Do module? This will be important, especially if the receiver is split into two separate enclosures.
Not specifically, but AMSAT has significant experience with a specific model of YSI 3-lead thermistor, and some thoughts have accumulated in the folklore over time about other alternatives. I'm sure Lyle or others on-list can provide a suitable circuit example for you to use if that becomes necessary.
My plan is ...
Sounds good. Looking forward to hearing what you learn!
One last question… How do I reduce the heartbeat timing below three seconds? I couldn’t find any way to do that using the net controller. I’d like to confirm that the jump in frequency I see in the CAN-Do module’s 5 kHz noise every three seconds goes away.
I'll let Stephen answer that, since I don't use Windows and thus haven't run his recent software that I suspect you're using other than under his direct supervision... ;-)
Bdale
All: My OPINION, based on my experience, is that we're better off eliminating the noise at the source.
I understand Bdale's comments about flight units being delivered already, but if it is as simple as replacing one (easily replaceable, I'm assuming) component, I think we should at least consider that option in the system level engineering decision. I'd sure like to see the idea tested somewhere.
Again, that's my INPUT to the discussion.
Thanks & 73, Jim [email protected]
Bdale Garbee wrote:
On Wed, 2007-06-13 at 05:06 -0700, Juan Rivera wrote:
Good morning Stephen,
I happen to be online earlier than Stephen today, due to being in Atlanta on business, so let me provide some replies and he can chime in later if I miss anything.
And by the way, sorry about missing the TeamSpeak meeting last night. I was at dinner with a number of customers in Atlanta, and then realized the notebook I'm using now does not have a built-in microphone (and I'm not in the habit of traveling with a headset... should probably fix that!).
What if the CAN-Do module suffers a failure that causes acurrent overload? Is it protected by a fuse? The next generation receiver should continue to function as long as it has power. An overload in either unit should not cause the other to fail.
There is no fuse on the CAN-Do! widget. A sufficiently bad short would probably cause a trace to cook acting as a fuse, but all of the active circuitry is downstream of the switching regulator and thus fairly well isolated from the spacecraft power bus in case of failure anyway. Since you'll be bypassing the power switch on the CAN-Do! widget anyway, I don't think we have any significant coupled-failure scenarios.
Do you have any information of previous efforts to reduceCAN-Do noise by either shielding the module or replacing the inductor with a shielded version?
No. As I indicated in my email the other day, you are the first person integrating a CAN-Do! widget with an RF payload module... at least that we've had any feedback from.
Do you have a shielded inductor that I could swap for theexisting one if that proved necessary?
No. And frankly, solutions that involve *any* modification of the CAN-Do! widget boards at this point are going to be problematic, since all of the flight units have already been manufactured and functionally tested. That's not to say that we *can't* change the CAN-Do! widgets, but given the relatively small number of the total that are likely to end up in RF modules, choosing a solution that allows the CAN-Do! widget board to be used as-is may be a better systems-level design decision.
Have you designed a circuit that would allow temperature to bedetermined inside the receiver PCB itself, and not just on the CAN-Do module? This will be important, especially if the receiver is split into two separate enclosures.
Not specifically, but AMSAT has significant experience with a specific model of YSI 3-lead thermistor, and some thoughts have accumulated in the folklore over time about other alternatives. I'm sure Lyle or others on-list can provide a suitable circuit example for you to use if that becomes necessary.
My plan is ...
Sounds good. Looking forward to hearing what you learn!
One last question… How do I reduce the heartbeat timing below three seconds? I couldn’t find any way to do that using the net controller. I’d like to confirm that the jump in frequency I see in the CAN-Do module’s 5 kHz noise every three seconds goes away.
I'll let Stephen answer that, since I don't use Windows and thus haven't run his recent software that I suspect you're using other than under his direct supervision... ;-)
Bdale
To the extent that we have the ability to change things based on our experience, I agree. The CAN-Do modules are new to us in using them specifically in a spacecraft. The Germans demanded their flight modules over the objections of the designers and manufacturers so they are on their own with the consequences. I am expecting them to roll them again if they run into problems.
This kind of noise source is different in that we have decided to mount them as part and parcel of the individual boxes, inside them in fact. They must be treated differently from other power and control devices and demand more noise mitigation than we have power and control devices.
We cannot expect to overcome noise that has a huge 1/r^2 advantage over the weak signals from the ground.
My suggestion on the receiver testing, given that we know we are going another round, is we do everything possible to separate the noise source from the receiver so we are only testing and debugging the receiver.
Bob
Jim Sanford wrote:
All: My OPINION, based on my experience, is that we're better off eliminating the noise at the source.
I understand Bdale's comments about flight units being delivered already, but if it is as simple as replacing one (easily replaceable, I'm assuming) component, I think we should at least consider that option in the system level engineering decision. I'd sure like to see the idea tested somewhere.
Again, that's my INPUT to the discussion.
Thanks & 73, Jim [email protected]
Hi Bob,
Just curious - what were the "objections?"
Regards...Bill - N6GHz
Robert McGwier wrote:
The Germans demanded their flight modules over the objections of the designers and manufacturers so they are on their own with the consequences.
That they were not sufficiently tested by anyone who was to use them to build flight units. This consumed tantalum slides, and lots of effort. Stephen got essentially zero feedback from the engineering test units he sent. This noise issue could have easily been found. They have had the engineering units for a LONG time.
Bob
Bill Ress wrote:
Hi Bob,
Just curious - what were the "objections?"
Regards...Bill - N6GHz
Robert McGwier wrote:
The Germans demanded their flight modules over the objections of the designers and manufacturers so they are on their own with the consequences.
Bob:
Were they tested sufficiently for radiation resistance? I'm assuming that the tantalum was used to add radiation shielding for things like flash memory on the MCU. Mirek's receiver also uses flash memory to store the frequency. The PLLs used in the existing 70 cm receiver can be purchased in a pin-compatible rad-hard version. However, the frequency has to be stored in flash memory. PIC MCUs hold data for 40 years on earth but space is a harsher environment.
We have the option of buying PLLs (with more pins) that can be hard-wired to a particular frequency. These PLLs are much more expensive and have longer lead times as they are space rated.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" [email protected] To: "Bill Ress" [email protected] Cc: [email protected] Sent: Thursday, June 14, 2007 10:46 UTC Subject: [eagle] Re: CAN-Do noise abatement plan and questions
That they were not sufficiently tested by anyone who was to use them to build flight units. This consumed tantalum slides, and lots of effort. Stephen got essentially zero feedback from the engineering test units he sent. This noise issue could have easily been found. They have had the engineering units for a LONG time.
Bob
Bill Ress wrote:
Hi Bob,
Just curious - what were the "objections?"
Regards...Bill - N6GHz
Robert McGwier wrote:
The Germans demanded their flight modules over the objections of the designers and manufacturers so they are on their own with the consequences.
-- AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair "If you're going to be crazy, you have to get paid for it or else you're going to be locked up." Hunter S. Thompson _______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
John,
Yes, the CAN-Do! s were radiation tested and did very well. That was one of the first things done. It was a special PCB that had some alternate parts on it for us to choose from for the final version. The test was run without the Tantalum shields. The Tantalum shields reduce the dose rate so we are very comfortable with the device for the mission. We probably didn't need to shield everything like we did but it's easier to do that after testing the total device rather than try to figure out what each component can tolerate. Our police is to shield any device that contains an FET, top and bottom. I took this into consideration when designing the layout for this and the IHU so there are ICs of similar size on opposite sides of the PCB as much as possible so that the top shield on one provides bottom shielding for the other. It's not possible to shield the bottom of an SMD IC except to put the shield on the other side of the PCB anyway (J-lead SMDs are an exception to this but we don't use very many of them). Tantalum does an outstanding job of shielding. Sometime when I see you, ask me to tell you about the time I forgot I had a piece about 6" square in my brief-case when going through airport security.
Chuck
John B. Stephensen wrote:
Bob:
Were they tested sufficiently for radiation resistance? I'm assuming that the tantalum was used to add radiation shielding for things like flash memory on the MCU. Mirek's receiver also uses flash memory to store the frequency. The PLLs used in the existing 70 cm receiver can be purchased in a pin-compatible rad-hard version. However, the frequency has to be stored in flash memory. PIC MCUs hold data for 40 years on earth but space is a harsher environment.
We have the option of buying PLLs (with more pins) that can be hard-wired to a particular frequency. These PLLs are much more expensive and have longer lead times as they are space rated.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" [email protected] To: "Bill Ress" [email protected] Cc: [email protected] Sent: Thursday, June 14, 2007 10:46 UTC Subject: [eagle] Re: CAN-Do noise abatement plan and questions
That they were not sufficiently tested by anyone who was to use them to build flight units. This consumed tantalum slides, and lots of effort. Stephen got essentially zero feedback from the engineering test units he sent. This noise issue could have easily been found. They have had the engineering units for a LONG time.
Bob
Bill Ress wrote:
Hi Bob,
Just curious - what were the "objections?"
Regards...Bill - N6GHz
Robert McGwier wrote:
The Germans demanded their flight modules over the objections of the designers and manufacturers so they are on their own with the consequences.
-- AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair "If you're going to be crazy, you have to get paid for it or else you're going to be locked up." Hunter S. Thompson _______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
OK. The PIC MCU that I'm considering should be safe. It's rated for 40 years data retention in an automotive temperature range. Most parts guarantee only 10 year data retention or say nothing on the data sheet.
The PLLs are in J-lead PLCC packages, but they are silicon on sapphire so they may not need shielding.
73,
John KD6OZH
----- Original Message ----- From: "Chuck Green" [email protected] To: "John B. Stephensen" [email protected] Cc: "Robert McGwier" [email protected]; "Bill Ress" [email protected]; [email protected] Sent: Thursday, June 14, 2007 15:55 UTC Subject: Re: [eagle] Re: CAN-Do noise abatement plan and questions
John,
Yes, the CAN-Do! s were radiation tested and did very well. That was one of the first things done. It was a special PCB that had some alternate parts on it for us to choose from for the final version. The test was run without the Tantalum shields. The Tantalum shields reduce the dose rate so we are very comfortable with the device for the mission. We probably didn't need to shield everything like we did but it's easier to do that after testing the total device rather than try to figure out what each component can tolerate. Our police is to shield any device that contains an FET, top and bottom. I took this into consideration when designing the layout for this and the IHU so there are ICs of similar size on opposite sides of the PCB as much as possible so that the top shield on one provides bottom shielding for the other. It's not possible to shield the bottom of an SMD IC except to put the shield on the other side of the PCB anyway (J-lead SMDs are an exception to this but we don't use very many of them). Tantalum does an outstanding job of shielding. Sometime when I see you, ask me to tell you about the time I forgot I had a piece about 6" square in my brief-case when going through airport security.
Chuck
John B. Stephensen wrote:
Bob:
Were they tested sufficiently for radiation resistance? I'm assuming that the tantalum was used to add radiation shielding for things like flash memory on the MCU. Mirek's receiver also uses flash memory to store the frequency. The PLLs used in the existing 70 cm receiver can be purchased in a pin-compatible rad-hard version. However, the frequency has to be stored in flash memory. PIC MCUs hold data for 40 years on earth but space is a harsher environment.
We have the option of buying PLLs (with more pins) that can be hard-wired to a particular frequency. These PLLs are much more expensive and have longer lead times as they are space rated.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" [email protected] To: "Bill Ress" [email protected] Cc: [email protected] Sent: Thursday, June 14, 2007 10:46 UTC Subject: [eagle] Re: CAN-Do noise abatement plan and questions
That they were not sufficiently tested by anyone who was to use them to build flight units. This consumed tantalum slides, and lots of effort. Stephen got essentially zero feedback from the engineering test units he sent. This noise issue could have easily been found. They have had the engineering units for a LONG time.
Bob
Bill Ress wrote:
Hi Bob,
Just curious - what were the "objections?"
Regards...Bill - N6GHz
Robert McGwier wrote:
The Germans demanded their flight modules over the objections of the designers and manufacturers so they are on their own with the consequences.
-- AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair "If you're going to be crazy, you have to get paid for it or else you're going to be locked up." Hunter S. Thompson _______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
I would strongly suggest that after you have a prototype unit working enough that you are convinced you have chosen the right parts, it be radiation tested. Hopefully your PCB is of a size that will fit in Stacey's chamber. This should be a consideration when sizing any project's PCB. If it is not, you may have to produce a PCB sized for the purpose, not for flight. That's why the IHU is 100mm wide; Stacey's chamber had a 4" limit. He has a new, larger, chamber now (I don't know it's size).
SOS technology parts are inherently rad-hard. Of course, "rad-hard" is a relative term. The manufacturer may specify the tolerance since it is something they can feature. If they don't publicly state it, they may still know what it is and you might be able to talk to them and pry it out of them. We had some rad-hard memory ICs for the IHU in P3D but we still shielded them - probably unnecessary.
Chuck
John B. Stephensen wrote:
OK. The PIC MCU that I'm considering should be safe. It's rated for 40 years data retention in an automotive temperature range. Most parts guarantee only 10 year data retention or say nothing on the data sheet.
The PLLs are in J-lead PLCC packages, but they are silicon on sapphire so they may not need shielding.
73,
John KD6OZH
----- Original Message ----- From: "Chuck Green" [email protected] To: "John B. Stephensen" [email protected] Cc: "Robert McGwier" [email protected]; "Bill Ress" [email protected]; [email protected] Sent: Thursday, June 14, 2007 15:55 UTC Subject: Re: [eagle] Re: CAN-Do noise abatement plan and questions
John,
Yes, the CAN-Do! s were radiation tested and did very well. That was one of the first things done. It was a special PCB that had some alternate parts on it for us to choose from for the final version. The test was run without the Tantalum shields. The Tantalum shields reduce the dose rate so we are very comfortable with the device for the mission. We probably didn't need to shield everything like we did but it's easier to do that after testing the total device rather than try to figure out what each component can tolerate. Our police is to shield any device that contains an FET, top and bottom. I took this into consideration when designing the layout for this and the IHU so there are ICs of similar size on opposite sides of the PCB as much as possible so that the top shield on one provides bottom shielding for the other. It's not possible to shield the bottom of an SMD IC except to put the shield on the other side of the PCB anyway (J-lead SMDs are an exception to this but we don't use very many of them). Tantalum does an outstanding job of shielding. Sometime when I see you, ask me to tell you about the time I forgot I had a piece about 6" square in my brief-case when going through airport security.
Chuck
John B. Stephensen wrote:
Bob:
Were they tested sufficiently for radiation resistance? I'm assuming that the tantalum was used to add radiation shielding for things like flash memory on the MCU. Mirek's receiver also uses flash memory to store the frequency. The PLLs used in the existing 70 cm receiver can be purchased in a pin-compatible rad-hard version. However, the frequency has to be stored in flash memory. PIC MCUs hold data for 40 years on earth but space is a harsher environment.
We have the option of buying PLLs (with more pins) that can be hard-wired to a particular frequency. These PLLs are much more expensive and have longer lead times as they are space rated.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" [email protected] To: "Bill Ress" [email protected] Cc: [email protected] Sent: Thursday, June 14, 2007 10:46 UTC Subject: [eagle] Re: CAN-Do noise abatement plan and questions
That they were not sufficiently tested by anyone who was to use them to build flight units. This consumed tantalum slides, and lots of effort. Stephen got essentially zero feedback from the engineering test units he sent. This noise issue could have easily been found. They have had the engineering units for a LONG time.
Bob
Bill Ress wrote:
Hi Bob,
Just curious - what were the "objections?"
Regards...Bill - N6GHz
Robert McGwier wrote:
The Germans demanded their flight modules over the objections of the designers and manufacturers so they are on their own with the consequences.
-- AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair "If you're going to be crazy, you have to get paid for it or else you're going to be locked up." Hunter S. Thompson _______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
SOS technology parts are inherently rad-hard.
In the sense that they are latchup-immune.
73,
Lyle KK7P
All of the Peregrine products are SoS but they have more expensive versions of some that are good for a 100 krad total dose.
73,
John KD6OZH
----- Original Message ----- From: "lyle johnson" [email protected] To: "Chuck Green" [email protected]; "John B. Stephensen" [email protected] Cc: [email protected] Sent: Thursday, June 14, 2007 18:06 UTC Subject: Re: [eagle] Re: CAN-Do noise abatement plan and questions
SOS technology parts are inherently rad-hard.
In the sense that they are latchup-immune.
73,
Lyle KK7P
I think they are also inherently are more background radiation tolerant. But why they have whatever tolerance they have is not really the question. The question is, just how hard are they?
If they have parts that are 100 krad tolerant, then there is a good chance all their parts are (probably come off the same wafer). They just have more paperwork with them, hence the extra cost. Assuming the cost delta is significant, I'd try the less expensive version and test it.
Lyle, I assume Heather is driving!!!
Chuck
John B. Stephensen wrote:
All of the Peregrine products are SoS but they have more expensive versions of some that are good for a 100 krad total dose.
73,
John KD6OZH
----- Original Message ----- From: "lyle johnson" [email protected] To: "Chuck Green" [email protected]; "John B. Stephensen" [email protected] Cc: [email protected] Sent: Thursday, June 14, 2007 18:06 UTC Subject: Re: [eagle] Re: CAN-Do noise abatement plan and questions
SOS technology parts are inherently rad-hard.
In the sense that they are latchup-immune.
73,
Lyle KK7P
lyle johnson wrote:
SOS technology parts are inherently rad-hard.
In the sense that they are latchup-immune.
Yes, not in the sense that they cannot degrade in other ways over time in the harsh environment like the Van Allen Belts four times a day.
73,
Lyle KK7P
Bob
Hi John
OK. The PIC MCU that I'm considering should be safe. It's rated for 40 years data retention in an automotive temperature range. Most parts guarantee only 10 year data retention or say nothing on the data sheet.
On ESEO, we have avoided PLLs because of the requirement to program them at power on, although I have used them often before for programming PLLs on the ground: those PIC10F SOT23 packages are really neat! ESEO has a default mode of a traditional analog linear transponder. PICs have not faired particularly well in radiation tests, and I'd suggest that it may be wise to consider both SELs/SEBs as well as total dose.
You can shield against TID to a large extent by depending on tantalum as previously described, as well as the spacecraft's aluminum structure and enclosures, but this will not prevent SEEs from happening. After shielding, SEEs that are predominently caused by high energy protons. You may well need to consider other mitigation efforts against these high energy inner Van Allen (proton) belt effects.
On designs with PICs, I have implemented over current protection using INA200 devices that cut the power for about 30s as soon as a preset current is passed. This is an attempt to reduce the chance of an SEB, when a FET effectively turns into an SCR clamping VSS and VDD.
Care should be taken when setting the current trip - not only do you not want to power down the device if it genuinely wants extra current, but equally TID (total ionising dose) means that over time the FETs will take gradually more current anyway.
Achim Volhardt DH2VA already did some radiation tests on a PIC12F device programming an SPI DDS (AD9834) at CERN when the CANDo's were done also. I attach his notes. As well as the CREME96 simultations that Achim describes, there is also SPENVIS: unlike CREME96, SPENVIS can include both the electron and the proton belts in its analyses. I cannot stress enough the effect that the orbit has on the amount of ionizing radiation that a spacecraft is subjected to! Indeed, the AO-10 IHU's early demise is due to its low inclination HEO orbit, spending inordinate amounts of unplanned time within the Van Allen belts. By increasing the inclination, significantly reducing the time spent in the Van Allen belts during an elliptic HEO orbit, ionising radiation can be reduced by orders of magnitude.
Although there is some science in this, it's a fairly subjective risk analysis that guides the tradeoff between the complexity of mitigation circuitry against the KISS principal. After all, if the planned propulsion fails, you're left in a near equatorial orbit and a big dose of radiation!
73, Howard G6LVB
Hi Guys,
This is the first time I have seen something written about radiation where I came away believing that the author actually understood what he was talking about!
If you want the inside information regarding PICs and radiation, I'd suggest contacting Steve Bible. But keep in mind that he is an employee of the company that makes PICs.
Chuck
Howard Long wrote:
Hi John
OK. The PIC MCU that I'm considering should be safe. It's rated for 40 years data retention in an automotive temperature range. Most parts guarantee only 10 year data retention or say nothing on the data sheet.
On ESEO, we have avoided PLLs because of the requirement to program them at power on, although I have used them often before for programming PLLs on the ground: those PIC10F SOT23 packages are really neat! ESEO has a default mode of a traditional analog linear transponder. PICs have not faired particularly well in radiation tests, and I'd suggest that it may be wise to consider both SELs/SEBs as well as total dose.
You can shield against TID to a large extent by depending on tantalum as previously described, as well as the spacecraft's aluminum structure and enclosures, but this will not prevent SEEs from happening. After shielding, SEEs that are predominently caused by high energy protons. You may well need to consider other mitigation efforts against these high energy inner Van Allen (proton) belt effects.
On designs with PICs, I have implemented over current protection using INA200 devices that cut the power for about 30s as soon as a preset current is passed. This is an attempt to reduce the chance of an SEB, when a FET effectively turns into an SCR clamping VSS and VDD.
Care should be taken when setting the current trip - not only do you not want to power down the device if it genuinely wants extra current, but equally TID (total ionising dose) means that over time the FETs will take gradually more current anyway.
Achim Volhardt DH2VA already did some radiation tests on a PIC12F device programming an SPI DDS (AD9834) at CERN when the CANDo's were done also. I attach his notes. As well as the CREME96 simultations that Achim describes, there is also SPENVIS: unlike CREME96, SPENVIS can include both the electron and the proton belts in its analyses. I cannot stress enough the effect that the orbit has on the amount of ionizing radiation that a spacecraft is subjected to! Indeed, the AO-10 IHU's early demise is due to its low inclination HEO orbit, spending inordinate amounts of unplanned time within the Van Allen belts. By increasing the inclination, significantly reducing the time spent in the Van Allen belts during an elliptic HEO orbit, ionising radiation can be reduced by orders of magnitude.
Although there is some science in this, it's a fairly subjective risk analysis that guides the tradeoff between the complexity of mitigation circuitry against the KISS principal. After all, if the planned propulsion fails, you're left in a near equatorial orbit and a big dose of radiation!
73, Howard G6LVB
And is someone who happens to know a lot about radiation :-)
Did somebody ring?
- Steve N7HPR
On 6/14/07 2:15 PM, "Chuck Green" [email protected] wrote:
Hi Guys,
This is the first time I have seen something written about radiation where I came away believing that the author actually understood what he was talking about!
If you want the inside information regarding PICs and radiation, I'd suggest contacting Steve Bible. But keep in mind that he is an employee of the company that makes PICs.
Chuck
Howard Long wrote:
Hi John
OK. The PIC MCU that I'm considering should be safe. It's rated for 40 years data retention in an automotive temperature range. Most parts guarantee only 10 year data retention or say nothing on the data sheet.
On ESEO, we have avoided PLLs because of the requirement to program them at power on, although I have used them often before for programming PLLs on the ground: those PIC10F SOT23 packages are really neat! ESEO has a default mode of a traditional analog linear transponder. PICs have not faired particularly well in radiation tests, and I'd suggest that it may be wise to consider both SELs/SEBs as well as total dose.
You can shield against TID to a large extent by depending on tantalum as previously described, as well as the spacecraft's aluminum structure and enclosures, but this will not prevent SEEs from happening. After shielding, SEEs that are predominently caused by high energy protons. You may well need to consider other mitigation efforts against these high energy inner Van Allen (proton) belt effects.
On designs with PICs, I have implemented over current protection using INA200 devices that cut the power for about 30s as soon as a preset current is passed. This is an attempt to reduce the chance of an SEB, when a FET effectively turns into an SCR clamping VSS and VDD.
Care should be taken when setting the current trip - not only do you not want to power down the device if it genuinely wants extra current, but equally TID (total ionising dose) means that over time the FETs will take gradually more current anyway.
Achim Volhardt DH2VA already did some radiation tests on a PIC12F device programming an SPI DDS (AD9834) at CERN when the CANDo's were done also. I attach his notes. As well as the CREME96 simultations that Achim describes, there is also SPENVIS: unlike CREME96, SPENVIS can include both the electron and the proton belts in its analyses. I cannot stress enough the effect that the orbit has on the amount of ionizing radiation that a spacecraft is subjected to! Indeed, the AO-10 IHU's early demise is due to its low inclination HEO orbit, spending inordinate amounts of unplanned time within the Van Allen belts. By increasing the inclination, significantly reducing the time spent in the Van Allen belts during an elliptic HEO orbit, ionising radiation can be reduced by orders of magnitude.
Although there is some science in this, it's a fairly subjective risk analysis that guides the tradeoff between the complexity of mitigation circuitry against the KISS principal. After all, if the planned propulsion fails, you're left in a near equatorial orbit and a big dose of radiation!
73, Howard G6LVB
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Howard:
The discussions last year were about placing Eagle in a low inclination HEO orbit. Your comments imply that the ionizing radiation dose will increase by a factor of 100. This would be 500 krad over 10 years. Is this literally true?
73,
John KD6OZH
----- Original Message ----- From: "Howard Long" [email protected] To: "'John B. Stephensen'" [email protected]; "'Chuck Green'" [email protected] Cc: [email protected] Sent: Thursday, June 14, 2007 20:58 UTC Subject: RE: [eagle] Re: CAN-Do noise abatement plan and questions
Hi John
OK. The PIC MCU that I'm considering should be safe. It's rated for 40 years data retention in an automotive temperature range. Most parts guarantee only 10 year data retention or say nothing on the data sheet.
On ESEO, we have avoided PLLs because of the requirement to program them at power on, although I have used them often before for programming PLLs on the ground: those PIC10F SOT23 packages are really neat! ESEO has a default mode of a traditional analog linear transponder. PICs have not faired particularly well in radiation tests, and I'd suggest that it may be wise to consider both SELs/SEBs as well as total dose.
You can shield against TID to a large extent by depending on tantalum as previously described, as well as the spacecraft's aluminum structure and enclosures, but this will not prevent SEEs from happening. After shielding, SEEs that are predominently caused by high energy protons. You may well need to consider other mitigation efforts against these high energy inner Van Allen (proton) belt effects.
On designs with PICs, I have implemented over current protection using INA200 devices that cut the power for about 30s as soon as a preset current is passed. This is an attempt to reduce the chance of an SEB, when a FET effectively turns into an SCR clamping VSS and VDD.
Care should be taken when setting the current trip - not only do you not want to power down the device if it genuinely wants extra current, but equally TID (total ionising dose) means that over time the FETs will take gradually more current anyway.
Achim Volhardt DH2VA already did some radiation tests on a PIC12F device programming an SPI DDS (AD9834) at CERN when the CANDo's were done also. I attach his notes. As well as the CREME96 simultations that Achim describes, there is also SPENVIS: unlike CREME96, SPENVIS can include both the electron and the proton belts in its analyses. I cannot stress enough the effect that the orbit has on the amount of ionizing radiation that a spacecraft is subjected to! Indeed, the AO-10 IHU's early demise is due to its low inclination HEO orbit, spending inordinate amounts of unplanned time within the Van Allen belts. By increasing the inclination, significantly reducing the time spent in the Van Allen belts during an elliptic HEO orbit, ionising radiation can be reduced by orders of magnitude.
Although there is some science in this, it's a fairly subjective risk analysis that guides the tradeoff between the complexity of mitigation circuitry against the KISS principal. After all, if the planned propulsion fails, you're left in a near equatorial orbit and a big dose of radiation!
73, Howard G6LVB
John B. Stephensen wrote:
Bob:
Were they tested sufficiently for radiation resistance? I'm assuming that the tantalum was used to add radiation shielding for things like flash memory on the MCU. Mirek's receiver also uses flash memory to store the frequency. The PLLs used in the existing 70 cm receiver can be purchased in a pin-compatible rad-hard version. However, the frequency has to be stored in flash memory. PIC MCUs hold data for 40 years on earth but space is a harsher environment.
Yes, the CAN=Do were beat to heck and back in the radiation chamber. They will do just fine. We will test the heck out of the receiver in the same manner we do everything else so whatever radiation mitigation that needs to be done should be attempted BEFORE the test because the desired result is PASSING.
We have the option of buying PLLs (with more pins) that can be hard-wired to a particular frequency. These PLLs are much more expensive and have longer lead times as they are space rated.
This is an option that we should consider. I would like more details.
73,
John KD6OZH
73's Bob
Peregrine makes two delta-sigma PLLs (PE9763 and PE97632) with pins for setting the frequency in small increments. They are only available in a rad-hard version but I haven't received a response from Peregrine about pricing and availability. The rad-hard versions of the integer-N PLLs that are compatible with the current devices are $2600 for 25 units with a 16-week lead time. I expect that the delta-sigma PLLs will be somewhat more expensive. The URX Initialization document describes the options for PLLs.
73,
John KD6OZH
We have the option of buying PLLs (with more pins) that can be hard-wired to a particular frequency. These PLLs are much more expensive and have longer lead times as they are space rated.
This is an option that we should consider. I would like more details.
73's Bob
Hi Juan,
I'll take a cut at some of your questions and let Stephen correct me.
Juan Rivera wrote:
Good morning Stephen,
I do have a few questions. Thanks for asking!
- What if the CAN-Do module suffers a failure that causes a current
overload? Is it protected by a fuse? The next generation receiver should continue to function as long as it has power. An overload in either unit should not cause the other to fail.
The CAN-Do! does have a 2 amp fuse at it's power input. The switched current to the module also goes through this fuse. If the module mission requires it to be impervious to the condition of this fuse, then additional power input to the box is needed. If this power requirement is small (less than a couple of amps) then you could use one or more of the "user" pins on the CAN-Do! If the power requirements are large (such as a transmitter) then an external connector should be used and that power controlled by the CAN-Do! supplied "switched" power. In either case, the module design should measure the current and provide that as telemetry (more on telemetry below).
- Do you have any information of previous efforts to reduce CAN-Do
noise by either shielding the module or replacing the inductor with a shielded version?
I think you are the first.
- Do you have a shielded inductor that I could swap for the existing
one if that proved necessary?
None has been looked for.
- Have you designed a circuit that would allow temperature to be
determined inside the receiver PCB itself, and not just on the CAN-Do module? This will be important, especially if the receiver is split into two separate enclosures.
There are some "user" analog inputs to the CAN-Do! that can be used for this or any other analog thing you want included in the telemetry.
My plan is to desolder the CAN-Do module from the receiver PCB today and move the receiver PCB to the enclosure’s rear set of mounts. This will put about 2-inches of space between the two. I’ll make up two interconnecting cables – one just long enough to attach the two while in the case, and one that is a foot or two long, assuming that I can find the parts I need and don’t have to solder the cable to the two units. I can use that long cable to try some troubleshooting. I’ll use that CAN-Do’s noisy inductor as the noise source and move it around over the receiver to see what affect it has. Perhaps I can find the area that is the most susceptible to noise that way.
I think the next receiver could use the entire available board space to:
Put distance between the two modules
Further isolate the CAN-Do module with a shield if necessary
Add power supply input filtering and input current overload protection
Include CAN-Do data line filtering if that turns out to be necessary
Add a temperature sensor in the vicinity of the SAW filters, and
another on the second PCB if it gets split into two sections
One last question… How do I reduce the heartbeat timing below three seconds? I couldn’t find any way to do that using the net controller. I’d like to confirm that the jump in frequency I see in the CAN-Do module’s 5 kHz noise every three seconds goes away.
I think your question is "How do I stop the CAN-Do! from having its watchdog time out?" You can't change the length of the watchdog timeout as that is set by the firmware in the CAN-Do! Sending the CAN-Do! config. packets at intervals of less that three seconds should stop the CAN-Do! from resetting. It is intended that the IHU will do this in the satellite at 20 ms intervals while collecting telemetry.
I hope this helps, Chuck
73,
Juan
*From:* [email protected] [mailto:[email protected]] *On Behalf Of *Stephen Moraco *Sent:* Tuesday, June 12, 2007 7:21 PM *To:* Juan Rivera; Juan Rivera *Cc:* Jim Sanford; Bdale Garbee *Subject:* late to tonight's meeting
Juan,
Sorry I missed your presentation/discussion tonight.
Any questions/issues for me re: CAN Do! ?
Regards, Stephen --
[email protected] mailto:[email protected]
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
On Wed, 2007-06-13 at 07:24 -0700, Chuck Green wrote:
The CAN-Do! does have a 2 amp fuse at it's power input.
Oops. Juan, Chuck is right and I was wrong on this one.
Bdale
Juan,
Thanks Bdale and Chuck for providing some of the answers!
How do I reduce the heartbeat timing below three seconds?
The CDNC hartbeat control is in two pieces: (1) the pulldown for changing frequency of the heartbeat and (2) the button to enable or disable the heartbeat.
So: select the rate using the pulldown, then press the [Heartbeat] button to enable it. If you want to change rate then press the button to stop it, adjust the pulldown to change rate, then press the button to enable it once more.
This help?
Regards, Stephen
participants (11)
-
Bdale Garbee -
Bill Ress -
Chuck Green -
Howard Long -
Jim Sanford -
John B. Stephensen -
Juan Rivera -
lyle johnson -
Robert McGwier -
Stephen Moraco -
Steven Bible