Thread: computer supply on?

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in the past used old IBM/HP/Compaq computer power supplys to drive windsheild motors. they had a hard switch wired from the case to the power supply to turn on and off. In some cases 386 computers even had a hard rod that push a button inside the power supply No problem. Grabbed a few "newer" old Emachines computers and noticed that their aint no stink'n hard switch but all the wires now runs into the mother board and the case switch runs into the motherboard too. Plus "shut down" turns off the power supply without a physical button push. So when the power supply is hookedup correctly to the motherboard, it powers up. Remove it and attached to prop... just sits there and keeps the prop from falling over. (dead weight)

So I'm thinking that one of the wires that goes to the motherboard acts like some type of trigger to a relay in the powersupply? !@#$%, just when i thought things would be cheap and easy, i find myself looking at adds for Battery chargers! !@##$%.

HELP! How do I turn this thing on?

.....please....

If you look at the big (20 or 24 pin) connector from the power supply, you'll see one green wire. Short that green wire to any one of the black ground wires & the power supply will turn on. Yellow is 12V, red is 5V, and orange is 3v.

thanks for confirming that there is a internal switch/relay and the wire to trigger it. After reading your post, i went on to researching and found this...

How to Convert a Computer power supply to a lab power supply.

hope it helps someone beside me.

No problem! I've built a few of them myself.

or an even quicker method:



Dont get me wrong, the work station thing with an atx power supply is a better long term solution, but if your just going for the quick fix, I just thought I would share!


Fordman

So on the newer atx power supplies, do you need to run a resistor as shown on scary terry's page, or can you just jump the green pin to the common?

Just run the Jumper from 14 to 15, 16 or 17 and the PS will work, no extra wires needed. I dont use any resistors. I believe you need a resistor if there will not be a load on the PS, if your using a wiper motor, that becomes the load.

Originally Posted by meltdown211

Just run the Jumper from 14 to 15, 16 or 17 and the PS will work, no extra wires needed. I dont use any resistors. I believe you need a resistor if there will not be a load on the PS, if your using a wiper motor, that becomes the load.

I disagree to a point. It depends on the power supply. i have done a number of these as well and it all depends on the model of PS. I have ones where i could simply jump the wires. Then i have had others where it required a "load" for it to stay running for any period of time. I solved the issue easily by using a LED push button:

SPST 10A 12VDC Illuminated Push Button Switch with Red LED - RadioShack.com

that i got from Radio $hack. It solves the issue of beign able to turn the PS on and off when you want and gives enough resistance to keep the PS working.