homemade EFIS system and EMI

All kinds unfortunately this is for aircraft use, he's starting with 12v
DC (transformers don't work with DC) and needs to get +-12v +5 and +3.3v
all DC.
John

John,

I think you'll find that the -12V is used only in "legacy" PC design for
ISA busses, or serial ports (which he probably isn't using).

Evan


Yes I did a little research on it and the only thing the negative is needed
for is the rs232 serial ports. for this you can get a $1.50 ic to convert
+12 to -12 V low current.
That said, what I'd do is get a 1.5 amp 5v TO-3 regulator and a 1 amp TO-220
regulator along with one of the TO-220 adjustable 1 amp regulators for the
3.3 v and run it all off the 12V (highly filtered) input. That said,
(again) you might have problems with th 12V regulator if the input drops
below 13.8V! So you might need to use a separate battery for it and diode
isolate it from the aircrafts electrical systm and have it charged when it
exceeds the 13.8 volt figure.
John