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

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From: smmoraco@gmail.com [mailto:smmoraco@gmail.com] 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
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kc0ftq@amsat.org