Power supply from an old 'puter

Nightrider7731

I have an old, gutted, Dell computer that I'd love to strip out its power supply to use as a 5V/12V bench power supply for my stamp projects.· Does anyone know if these·units are regulated?· And equally important, is there a way to override·an ATX power supply so it doesn't need the motherboard attached to it?

Thanks!

Post Edited (Nightrider7731) : 1/12/2005 7:57:42 AM GMT

steve_b

I think your power supply will probably be a 'switched' power supply.

I'm sure there are mods on the 'Net to be able to use it for a straight DC supply.

I'd imagine it involves a couple caps and a regulator.· Google it.



So far as the ATX....I think there's just an enable line from the motherboard.· google the pin out of an ATX connector.

Here's a couple quick links I found:

http://www.ts-consulting.net/ATXPS.HTM

http://www.powerstream.com/itx-atx-pinout.htm

One site said you just need to ground pin 14 to get it to turn on.

http://www.marcee.org/Articles/PCPowerSupply.htm

Anyhow, there's some sites out there!

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Steve
http://members.rogers.com/steve.brady
http://www.geocities.com/paulsopenstage

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

LoopyByteloose

I wonder if the switcher requires a minimum power consumption (which is likely above the BasicStamps) to be stable. Originally switchers were very touchy in low current situations.

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G. Herzog in Taiwan

Robert Kubichek

To use a computer power supply, you need to put a load resistor on one of the power outputs to keep the supply turned on, and regulate.
I would add some more caps for filtering. As they are used for computers, they will be fine for stamp circuits, just watch the amperage, as
I have low amperage fast blow fuses in line to my breadboard.

Nightrider7731

Does anyone know if the draw from a typical internal computer fan would generate enough load to keep·the PS stable?· The proj I'm working all will be using 6 SSRs and I had thought about adding a fan to the enclosure to keep things cool.· The other suggested precations are all great.

Thanks!

allanlane5

No, the main load resistor must be on the +5 to ground leg, I believe. The Fan (typically 12 volt DC) won't be on the right voltage leg.

steve_b

Remember too, that when you use those LM regulators, your source needs to be a few volts higher than what you want to regulate to.

So, to properly regulate 12Vdc, you need 14 or 15volts going in.· I think you CAN find rail-to-rail type regulators, but they still need a little bit of overhead.

Of course, if you don't load the power supply properly, you'll find the voltage to be higher (similar to unloaded wallwarts~~12Vdc unloaded wall wart will be up near 20volts.).

Anyhow, MAYBE, and I've never tried this, if you don't load down the power supply too much, it'll allow you to put a regulator on the end to get your 12volts.

Of course, just using some good sized filter caps would probably work fine!· smaller component count too! haha

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Steve
http://members.rogers.com/steve.brady
http://www.geocities.com/paulsopenstage

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

MikeS

Most switchers require a load for stable output. IBM use to recommend 5ohm/50watt resistor across +5v output. This would allow regulation for +5 and +12. Here is·a load resistor for switchers that you can purchase.

http://shop.store.yahoo.com/directron/1130282.html

MikeS