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Need some electrical help

I'm experimenting with putting a fan or two in my little grow chamber. I have a bunch of computer fans lying around, and I just picked up an old cheap computer power supply. Rather than spend more money on connectors I don't really need, I'm going to just cut the existing connectors off and wire things together directly. This will also give me as much length as I have speaker wire.

The power supply label says:
Red - +5V, 25.0A
Yellow - +12V, 10.0A
Black - GND

The fans have three wires, in those three colors. The fans are labelled DC 12V.

Many of the connectors I've seen online (4-pin to 3-pin) only use the black and yellow wires. I guess this makes sense since the numbers match.

So how should I go about this? Do I need to connect the red wire? Why is it even there?

And I assume there isn't any problem with wiring all five of my fans in the same place (i.e. twist all five yellows and the connecting yellow together and tape it up)?

I'm sure it's simple... I just want to make sure not to start any fires.
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Thanks for the input.
 
Hmm, looks like I have another problem. I didn't get a supply that was old enough. It gets switched on by the motherboard, so I have to figure out how to wire a switch to it to trick it. Good learning experience I guess.
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How much current do your fans draw? Your power supply only provides 10A at 12 volts.

The 5 volts is for the motherboard.
 
I'm an electrician, but I don't know much about computer wiring. I'll give you my opinion.

I think if you take two of the wires that go to the motherboard, and tie them together, it'll do the same as a switch. I don't know which two though.



Your fan is a 12v fan, so it needs to be wired to the 12v supply from the power supply. I would try to tie the yellow to yellow and the black to black first. If that don't work just experiment with which wire to use. It's only 12vs so it won't hurt if you tie the wrong wore together for a couple of seconds.

Sorry but that's about the best advice I can give with the info you gave. I hope it helps.
 
Figured out the switch.

I'm still curious what the red wire is for on the fans, but other than that I think I'm set.
 
Spoke too soon again... the fans aren't responding at all. Only a slight twitch if I connect the fan's red to the supply's yellow.

I can't figure out what's wrong and I'm not sure how to give help to someone who could diagnose.

I'm almost positive a power supply simply has to be running for devices to draw power from it. I don't see how the missing motherboard could have anything to do with it, since hard drives and CDROMs and such don't get their power routed through the motherboard in any way.

Hmm.
 
I wired a fan into a HDD or CDROM drive power connector, I could get you a photo if you wish.
 
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