Switching power for PC in cars

[eric schumacher]

On the subject of using PC motherboards in automoble applications I would
suggest some care in the power supply could eliminate a lot of odd buggy
behaviour once you get in a real life enviornment. The PC unlike most
industrial equipment connects logic ground to the case. This prevents you
from having good control of ground loops on the I/O.  I would suggest that
you galvanicaly isolate ith incoming power to the PC. This might not be
necessary if the PC was being used as a PC with no sensors and no outputs.
This will be a problem if you have sensors, the only question is how bad it
will be. A little conservatism early on will avoid a lot of grief later on.
Electrically the automobile is an evil place, you need all the help you can get.

I would suggest a flyback converter with transformer output and an opto
isolator and TL531 sensing Vcc to generate the 5.0 VDC The other required
outputs will be co-regulated for input variation and a LDO regulator should
clean things up nicely.  Use a bi-filar choke on the input. These techniques
are well covered in LTC and National literature.
























Lotsa Luck Eric
85 GTI with VR6 power