homemade EFIS system and EMI

"jcpearce" wrote in message
ups.com...
Thanks Dean, Elippse, Colin Lamb, Bob, AINut Don, Kayroc & Tim, I
really appreciate the advice.

Your comments rekindle my drive, I had hit a low point after designing
the data capture board, OS, circuits etc.. and then... being killed
with RF noise.

An odd, but beneficial I suppose, confluence of circumstances
involving a broken window pane and a mischievous dog and a storm lead
to water getting on the DC to DC power supply (11~14 DC - 12V, 5V,
3.3V +-) for the EPIA M motherboard. Not surprisingly it decided not
to continue functioning. I then pulled out a traditional power supply
to use, and.. amazingly 80% of the noise went away! I would hate to
curse but the blasted PW-60 #!@! (
http://store.ituner.com/ituner/pw60caatxpos.html ) power supply was the
primary culprit. It is a switching power supply with evidently little
RF and EMI protection. I am trying to find another DC-DC power supply
without these issues, they all appear to be switching power supplies, I
would rather deal with energy/heat loss than RF noise.

I don't want to go through the space and elaborate hastle of going from
the 11-14V bus to 120V AC to a bulky PC power supply (space is
critical) to 12,5,3.3V so I need to find a suitable non noisy power
supply and then deal with the issues you knowledgeable fellows
enumerated in the posts.

Thanks again to Dean, Elippse, Colin Lamb, Bob, AINut Don, Kayroc &
Tim.
Your comments rekindle my drive, I had hit a low point after designing
the data capture board, OS, circuits etc.. and then... being killed
with RF noise.

An odd, but beneficial I suppose, confluence of circucumstances
involving a broken window pane and a mischevious dog and a storm lead
to water getting on the DC to DC power supply (11~14 DC - 12V, 5V,
3.3V +-) for the EPIA M motherboard. Not surprisingly it decided not
to continue functioning. I then pulled out a traditional power supply
to use, and.. amazingly 90% of the noise went away! I would hate to
curse but the blasted PW-60 #!@! (
http://store.ituner.com/ituner/pw60caatxpos.html ) power supply was the
primary culprit. It is a switching power supply with evidently all
the wrong harmonics. I am trying to find another DC-DC power supply
without these issues, they all appear to be switching power supplies, I
would rather deal with energy/heat loss than RF noise.

I don't want to go through the space and elaborate hastle of going from
the 11-14V bus to 120V AC to a bulky PC power supply (space is
critical) to 12,5,3.3V so I need to find a suitable non noisy power
supply and then deal with the issues you knowledgable fellows
enumerated in the posts.

Thanks again to Dean, Elippse, Colin Lamb, Bob, AINut Don, Kayroc &
Tim.


Ahhh.... yes. I should have thought to mention the importance of a quiet
power supply. A PI filter between the supply and the PC is a good idea to
help ensure that switching noise from your supply doesn't get into your PC
board.

I'm used to designing my own power supplies for systems like this, so I
didn't stop to think that you might be using an off-the-shelf supply.

Dean