So this suggests that the audio card does not require 12V.
And the video card.  So I could clip the +/-12V lines on a
desktop system and use it w/o any probs (if no comms)?

Cheers,
-Neil.


> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Nick Veys
> Sent: Friday, August 30, 2002 10:48 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: Why does a PC need 12V?
>
>
> Serial Communication...
>
> Many, many car-computer power supplies people have made for mp3 players
> and such just didn't put a 12V supply in and had no problems.
>
> nick@veys.com | www.veys.com
>
> > -----Original Message-----
> > From: pic microcontroller discussion list
> > [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Pic Dude
> > Sent: Friday, August 30, 2002 9:14 AM
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: [EE]: Why does a PC need 12V?
> >
> >
> > 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)...
> >
> > - MOTHERBOARD:
> >     - 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
> >       here.
> >
> > - 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?
> >
> > Cheers,
> > -Neil.
> >
> > --
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