Searching \ for '[OT]PC Power Supply' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/power/actodc.htm?key=power
Search entire site for: 'PC Power Supply'.

Exact match. Not showing close matches.
PICList Thread
'[OT]PC Power Supply'
2000\06\04@142452 by John De Villiers

flavicon
face
What does one need to use a standard PC power supply as a normal bench power
supply? I want to use the 12v and 5v lines on one, but a pc techie friend of
mine says the power supply wont "come on" unless it detects a motherboard. I
presume this is just a load across one of the many wires on a MB power plug.

PS - im talking about the normal AT style power suppply.  Theyre cheap and
the 5v line can deliver a whopping 20A. They also have all the neccesary
short circuit and overcurrent protection that a test bench rig would need.

Regards
  John

2000\06\04@162524 by Mark Willis

flavicon
face
Pretty sure you just need a load resistor across the +5V to Ground
lines.  Draw an amp or so anyways there, should get you going.  (5 Ohm,
10 Watt resistor.)  IBM used to provide these for early XT users who
didn't have a hard drive so their system would boot.  Or just put a mini
system together & throw in some A/D and a tiny monitor and have yourself
a benchtop tool that also provides some other utility <G>  (that's what
I have, used a blank panel to provide a couple sets of power outputs.)
If I messed up it's a resistor across the 12V lines, pretty sure most of
these have 5V as primary switcher output and the 12V line is a parasitic
output.  If you have problems I'll go find that IBM AT tech ref manual
set, it sets the spec.  Probably, someone else on-list knows this
exactly <G>

It's an artifact of the switcher having a minimum Load Current rating on
the one power supply (it needs to keep running so it can still output
the other voltages, in a small nutshell.)

Hint:  Some PC power supplies are somewhat over-rated.  (At 150W at 5V
vs. 144W at 12V plus 8W for -5V and -12V, someone's over-rating this
250W power supply, methinks!)  Don't push the limits too hard IOW.

Hint:  FUSE that puppy.  Raychem Polyswitches are nice toys,
self-resetting, fairly cheap.  "Short circuit protection" on the supply
I use here, means if I exceed 5V at 28Aish, 12V at 10Aish, or -5 or -12V
at 0.5A, it self-protects.  That pic you put in backwards from having a
"bad brain day",won't like being fed 28A at 5V much.  PIC as light
source, a pricey concept <G>  (It's a 30A@5V and 12A@12V power supply, I
figure the momboard uses a couple amps anyways, the HDD a little too.)

Hint:  This isn't a "low-noise" power supply.  You may want to use R-L-C
filtering if you need cleaner power - don't know your needs.  For PIC
projects I just down-regulate from 9V, works.  (7809 inside that panel.)

Not hard to charge NiMH's off one of these, either.

 Mark

John De Villiers wrote:
{Quote hidden}

--
I re-ship for small US & overseas businesses, world-wide.
(For private individuals at cost; ask.)

2000\06\04@193401 by John C. Frenzel

flavicon
face
> John De Villiers wrote:
> > What does one need to use a standard PC power supply as a normal bench
power
> > supply? I want to use the 12v and 5v lines on one, but a pc techie
friend of
> > mine says the power supply wont "come on" unless it detects a
motherboard. I
> > presume this is just a load across one of the many wires on a MB power
plug.
> >
> > PS - im talking about the normal AT style power suppply.  Theyre cheap
and
> > the 5v line can deliver a whopping 20A. They also have all the neccesary
> > short circuit and overcurrent protection that a test bench rig would
need.
> >
> > Regards
> >    John
>
You can also plug a cpu fan into the floppy connector to load the supply
enough to regulate.  I have an old supply setup this way on my bench.
John

2000\06\05@170249 by Arthur Brown

flavicon
face
One problem using a PC Power Supply is that they nearly always need a load
on the 12+ or they don't start or may be damaged at switch on.

Art

{Original Message removed}

More... (looser matching)
- Last day of these posts
- In 2000 , 2001 only
- Today
- New search...