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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