homemade EFIS system and EMI

jcpearce wrote:

I built a test linear regulator power supply this evening and the TO-3
regulator bringing ~12v down to 3.3 Volts nearly burnt a hole in the
test board. I looked over the wiring which was OK so it looks like the
thermal output of bringing 12volts down to 3.3 for 3 amps is just way
too high. So so much for that idea (unless I am missing something)

I may just end up getting on the EPIA TC models as UltraJohn mentioned
and hope that their EMI/RFI solution is better. The plane battery
voltage is ~12volts idle and ~14 volts running, what is a way of doing
the "power stabilizing" necessary for the EPIA TC which requires
11.6-12.4 Volts? If I just put a 12V linear regulator on there the drop
off in voltage would prevent the system running off battery.

You could use an external wirewound resistor(around 20 ohm), mount it to
your metal chassis, this should drop it to around 5v at 3 amp draw and will
make your voltage regulator a lot happier!
No matter how you look at it dropping 12+ to 3.3 v you'll have to disipitate
some heat somewhere.
John
Unless you use a switching regulator vbg.