Why does a PC need 12V?
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I need to build a power-supply to run a PC in a car, so I'm
trying to figure out why I really need +/- 12V, which may be
tough to produce with the ignition off (not enough overhead
for the regulator). I could build a DC-to-DC coverter that
would raise the voltage, but that means $$$.
Thinking of a regular desktop PC with a MB, audio card, video
card, fan, and IDE drive only (no floppy or CD)...
- 5V around board, which may be regulated to lower for
processor, etc, but that should not affect me.
- The motherboard has a 12V requirement (standard ATX
PS), but does it really need it, or does it pass on
the 12V to other devices?
- AFAIK, the parallel port does not require 12V.
- AFAIK, USB does not require 12V.
- Does the built-in serial require a +/-12V supply? Or
does it generate +/-12V (like a MAX232 for example)?
If I need to supply it, and decide not to use serial
comms, then can I just ignore it? Or can I just supply
it with +/-5V (as an RS423 device) and make sure the
other end handles that level?
- COOLING FAN:
- I can always get or modify the fan for 5V use, or I
could generate 10-ish volts for that. So no prob
- AUDIO CARD:
- I believe line-out sound levels go to 10V, so +/-12V
is probably needed there. Any way around this?
- VIDEO CARD:
- No idea? Anyone know anything about these? Or would
it vary by manufacturer? (Which I doubt).
- HARD DRIVE:
- Have an IDE laptop drive which says 5V at 500ma, so I
should be okay here.
Anything else I'm missing?
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