[simpits-tech] PSU loading

[Mark Doran]

Switching power supplies usually need a load on all output circuits to
function.  A suggestion based on what I did to get an old AT supply
usable as a 12V power source for EPIC kit testing...

I took a pair of generic RS fuse holders and mounted them inside the
power supply casing.  I jammed the non-conducting body of a power
resistor for the 5 volt circuit into the fuse holders (the power
resistors tend to be quite chunky :-).  The mounting of the fuse holders
used solder terminal spades -- these I bent into the "grill" air inlet
of the power supply to effect the mounting so that as air is drawn in by
the fan, it cools the resistor also.  This arrangement seems to work
quite well...this supply has been on continuously for months with no
sign of trouble.

Cheers,

Mark.


> -----Original Message-----
> From: simpits-tech-admin@simpits.org [mailto:simpits-tech-
> admin@simpits.org] On Behalf Of Dave
> Sent: Friday, December 27, 2002 9:57 AM
> To: simpits-tech@simpits.org
> Subject: Re: [simpits-tech] PSU loading
> 
> Guys
> According to my reading Roy is correct. A load is required on both +5v
and
> +12v outputs. Modern M/boards like the ATX usually draw enough power
> themselves but the 12v needs a hard disk or such like connected.
Apparenly
> 2.0-4.0 amps are needed on the +5v and 0.5-1.0 amps on the +12v. Some
more
> expensive PSU's do have built in resistors so Gene is right as
> well...nothing new there then, eh :o) You can connect a 5 Ohm, 50 watt
> sandbar resistor between pins 1 and 2 on a disk drive power
connector...
> mind it will get  HOT!
> ----- Original Message -----
> From: "Roy Coates" <roy@flightlab.liv.ac.uk>
> To: <simpits-tech@simpits.org>
> Sent: Friday, December 27, 2002 4:42 PM
> Subject: RE: [simpits-tech] Resistor for LEDs?
> 
> 
> > On Wed, 25 Dec 2002, Gene Buckle wrote:
> >
> > > Actually, you only have to trick the power good return line into
> thinking
> > > it's hooked to a PC.
> > >
> >
> > I do recall the "power good" line on AT supplies but I'm sure to
keep a
> > switched mode PSU happy it NEEDS a load.
> >
> > Roy.
> >
> >
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