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ATX PSU help

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USSEnterprise:
This may have been asked before, but I couldn't find anything. How do you make an ATX PSU power up if you don't have a switch, because you aren't building it into a case?

RayB:
There is a wire you can "short" to ground to make it turn on.

USSEnterprise:
thanks, but nevermind. I figured it out. I stuck a jumper from a disk drive over the two pins

webgeek:
I know this is an old thread but it seems to come up a lot...

To ensure the power supply comes on when it gets plugged in, connect the green wire (power on) to ground (black wire). You can install a switch in there but I don't. The power supply has a switch under the AC plug in the back already. I just use that.

To get the power supply to give you constant voltage and not power down due to improper load, you install a 10 watt 10 ohm sandbar/wirewound resistor between +5 (red wire) and a ground. You will want to heatsink this resistor because it will get hot. I suggest zip-tying the resistor to the fan holes in the back of the power supply. This way the fan cools it off and it dissipates heat quickly.

To get the +12 volts, you use a yellow wire (if I remember correctly, check with a volt meter) and a ground. To get +5 volts, use a red wire and a ground. I suggest using a different ground for each of these steps as there are many available and it keeps things cleaner.

In my HydroCade thread on the project announcements forum, I post a link to a site that shows how to do all this. In the end, this technique has worked remarkably well for me. I'm really pleased with the results.

JCL:
Just wanted to note that webgeeks power resistor is only needed if you are not using the PS for a computer. The motherboard provided a good load if you just want a PC that can be powered up with a powerstrip.

Good writeup wg!

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