Russell,

I don't think the GNDs for PC supplies are isolated from mains ground, so
unless you float all three supplies, I don't think you can just tie GND
to 5V on adjacent supplies. I'm not sure, but I would probably want to
check that the GNDs are isolated from the neutral wire, too.

Sean


On Tue, 28 Mar 2000, Russell McMahon wrote:

> 500+watt slotcar power supply:
>
> If you want a really cheap design that might even work consider trying 3 x 5
> volt power supplies from standard IBM PC compatibles. These are available
> for very little surplus or second hand - even new they are cheap.
> 3 x 5 volt outputs in series, one from each supply = about 500 watts.
> These need some load to  regulate and you would probably need a moderate
> divided load across each of the 3 - probably a light bulb each :-)
> Something like an indicator bulb would probably be about right.
>
>
> x--------------------------------------- +
> x      Bulb                psu1
> x------
>     \
>     /
> x- ---- +
> x       Bulb               psu2
> x------ -
>     \
>     /
> x- --- +
> x      Bulb                psu3
> x ---- - ----------------------------- ground
>
>
> Nasty but cheap and may be good enough with a little playing.
>
>
>
>       Russell McMahon
> _____________________________
>
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>
>
> -----Original Message-----
> From: Chris Eddy <    >
> To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
> Date: Tuesday, 28 March 2000 13:00
> Subject: Re: [OT] PSU for slot cars
>
>
> >Quentin;
> >
> >Late breaking discovery;
> >
> >I was going through a book titled 'power supplies, switching regulators,
> >inverters, and conveters' by Irving Gottlieb.  It is relatively popular,
> >I happen to know that there is another copy at the Borders near here at
> >this moment.  It has some really comprehensive design info on
> >converters, and a number of design case studies.  You still have to
> >create a transformer, but many of these converters are not flyback
> >converters, but the more gentle forward converter.  I have mine eyes on
> >an example of a 225 watt line operated 15V power supply design example,
> >and a 500 watt example that is similar.  I think that the basic
> >principles in here will solve your quest.
> >
> >Chris Eddy
> >
>