ATX power supply on/off

Can any one tell me how to effect a simple on/off control of a standard ATX type power supply to use it on bench or for other projects? How does motherboard control this function? Thanks

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While we're at it, you can power up an ATX power supply by shorting the green wire with any black ground wire. As you know, the ATX power supply will not turn on normally without a motherboard connected to it. There are times when you may want to test an ATX power supply or use the voltage from one but don't really want to hook up a motherboard. There's only one green wire and there are plenty of ground wires so it's easy to do. To use a bent paper clip and insert one end in the green wire connector and bend it around and put it into a black wire connector.

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Also you usually need a load on the output of the supply before it will start or stay on .

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Ralph Mowery

In article , (known to some as ee_design) scribed...

It's usually a 'soft' logic switch. A momentary contact closure toggles a flip-flop in the supply which turns it on. A continuous closure of more than ten or so seconds usually turns it off.

With that said: Using a PC supply for any type of serious bench work is a poor idea, IMO. They are often very (electrically) noisy, in terms of RF emissions, their outputs are rarely variable, and most of them need a minimum load on the +5V line to even regulate properly.

There are plenty of very decent and affordable 'lab' type variable power supplies that show up at ham radio swap meets and electronic surplus places, to say nothing of Greed-bay. If you're serious about clean experiment power for your bench, or something noise-critical like servicing radio equipment, you should seriously consider investing in such.

Happy hunting.

Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
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Dr. Anton T. Squeegee

On Sun, 6 Aug 2006 09:06:15 -0700, Dr. Anton T. Squeegee put finger to keyboard and composed:

The logic is on the motherboard. The PS_ON signal is 'hard', ie there is no flip-flop in the PSU.

- Franc Zabkar

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Franc Zabkar

for load you could use a light bulb 12v or a resistor accross ground and 5vline 50-100ohm. and a led on the power good se if it lights.

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