Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!att!alberta!dvinci!dueck
From: dueck@dvinci.USask.CA (Harvey C. Dueck)
Newsgroups: sci.electronics
Subject: Re: DC power supply for IBM PC?
Message-ID: <2045@dvinci.USask.CA>
Date: 2 Jun 89 19:58:14 GMT
References: <4682@drivax.UUCP> <1989May28.214142.26384@utzoo.uucp>
Reply-To: dueck@dvinci.UUCP (Harvey C. Dueck)
Distribution: na
Organization: University of Saskatchewan, Saskatoon, Canada
Lines: 25

In article <4682@drivax.UUCP> macleod@drivax.UUCP (MacLeod) writes:
>... Since the internal AT power supply takes
>120Vac to produce +5Vdc @20A, -5Vdc @.5A, +12Vdc @8A, and -12Vdc @.5A,
>shouldn't it be relatively easy to cook up a modification to the power 
>supply (or a replacement for it) which would run directly from 12Vdc power?

On the table behind me is a CMOS PC clone which our lab uses for field
processing.  The power supply runs off two car batteries which are used
to provide +12V and -12V to a DC to DC converter (PICO KRA5S, according
to the label on the converter).  A simple circuit using a diode and
two miniature relays protects the converter against inadvertently
connecting the batteries incorrectly and a voltage regulator is used
to improve regulation of the converter output.  In all, the supply
requires 13 components including a heat sink.  I think that the total
parts cost was something like $450 Canadian.  The converter itself
cost ~$350.

I don't know if there exist converters which will provide +12V and
-12V from a single 12V supply.  Ask your local electronics parts dealer.
If someone wants schematics for our supply, I could probably be
induced to mail them a copy.

			- harv
dueck@dvinci.usask.ca
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