Help me cool a computer cabinet.

November 13, 2006 6:39 AM

There's a computer stashed inside a desk cabinet. It's too hot inside the cabinet. What to do?

My brother's computer is running too hot.
The computers fans are moving air...but since this is inside of a closed cabinet, the cabinet area is gets very hot (which means the computer's fans are only moving hot air).

Obviously, I want to try to cool down the cabinet.

The project I've started is adding some fans to the non visible side of the cabinet and some holes at the bottom of the opposite side.

The problem: how to power them. The fans are the standard computer fans with the 4 prong plastic power connectors meant to go to a power supply. As I plugged in an extra power supply (standard to a computer)...I realized that I need an on/off switch that would normally connect via the motherboard.

And at this point, I'm lost.

I know basic wiring/stripping/soldering. I don't know enough about capacitors and the like. Radio shack and a comp usa are nearby.

Hope me hive mind.

posted by filmgeek to computers & internet (18 answers total)

Hey Filmgeek. Well, first of all, if you already have a standard power supply running, good on ya. But you know what's better than a standard (ATX) power supply? An old AT power supply- they have a switch to operate them. So your best (meaning simplest) bet is an old 486 with a switched-with-a-normal-switch power supply.

Now, that's not your only option. It's not that hard to modify an ATX power supply with a SPST (single pole, single throw, available at Rat Shack) switch to turn it on and off. On the motherboard connector, there is a green wire, pin #16. Connecting this wire to the black wire (ground) will turn the power supply on.

There's a needlessly complicated tutorial here: ignore all the stuff about binding posts and LEDs, and just pay attention to how they wire the switch. That should get you up and running.
posted by fake at 7:04 AM on November 13, 2006

Another note, I'm sure you've already thought of this, but I've had really good luck just knocking out the back of such cabinets, usually they are that thin paperboard stuff, and the back really isn't important. Seems too obvious to be of any use, though.
posted by fake at 7:06 AM on November 13, 2006

What about just plugging your extra power supply into a power strip, along with the computer and monitor? That forces you to turn the fans on when you turn the computer on.
posted by backseatpilot at 7:44 AM on November 13, 2006

As long as your PC has power to spare (IE 350W or more), Why not look into getting an extension for one or two of your internal connectors.. a long one. say 18", and run it out of a hole in the back of your PC? Plug it into another extension connected to your fans, and you can just connect it when you load and unload the PC from its space.
Some of the less "consumer" stores have extensions like this for 24" cases and such where stock power cables can't reach.

This would let you shut down the other fans whenever the PC is off.
posted by upc_head at 7:55 AM on November 13, 2006

Or yet another possibility- get an ATX to AT adapter like this one.

Further still, you could simply use the computer's existing power, using a Y extension cable like this. Bonus that you don't have to worry about turning the fans on and off, they'll be automagic.
posted by fake at 7:58 AM on November 13, 2006

Or what UPC said.
posted by fake at 7:58 AM on November 13, 2006

If you find the noise from the additional fans to be a problem, you might consider this (unorthodox) method that I use: I got a couple of largish box fans that are meant to run at 220 volts and wired them up to a regular 110 volt plug, at this voltage they run slow and quiet but still move a reasonable amount of air because they are industrial fans that blow like crazy at the correct voltage.
posted by StickyCarpet at 8:22 AM on November 13, 2006

Pull the power from the USB ports.
posted by Good Brain at 8:28 AM on November 13, 2006

I had exactly the same problem. I bought one of these, mounted it on a hole cut into the back of the computer cavity (at the top, blowing out) and made another hole near the bottom. The cavity is now 12-14 degrees C cooler. Like Good Brain said, this fan runs off power from a spare USB port.
posted by AstroGuy at 8:41 AM on November 13, 2006

(I meant to say the computer is running 12-14 degrees cooler.)
posted by AstroGuy at 8:42 AM on November 13, 2006

You definitely want to use the computer's internal power supply. Powering up a whole AT/ATX supply just for a couple of fans is very wasteful; you'll be burning 50W when 10W would do.

I'm not sure about the USB port.. It is possible, but your typical 12V case fan isn't going to run off 5V very well (some people put case fans between the +5V and +12V line, to create 7V - a lot more than 5V). Also, the total output power of your USB ports is pretty limited, and you might want it for something else one day. Not such a big deal, but better not to create future hassles for yourself.

If you really don't want to use the computer's internal power, get an AC adapter. Most hubs and routers use 12V 1A adapters, an extra from an old/dead router should work perfectly.
posted by Chuckles at 8:58 AM on November 13, 2006

If you have a Fry's electronics nearby, they have those "universal" wall-warts that puts out up to 12V at 1A for like $7. If you don't have a Fry's nearby you could order one online but you can probably find similar at Best Buy or wherever. (Just make sure it's a full amp.)

The reason I suggest this is that the voltage is adjustable so you can turn down the fan speed. The 1A rating should be fine for a fan or three.

BTW, use the biggest fans you can; that way you can run them slower and still move plenty of air.
posted by kindall at 11:32 AM on November 13, 2006

Whoops, that link in my post goes to the 300 mA one you shouldn't buy. I know they have a 1A one at the store, though.
posted by kindall at 11:34 AM on November 13, 2006

A public library in the area had custom cabinets for the OPACs. They were having a lot of issues with hardware failure.

They took the doors off, and one of the staffer's husbands, who was in to woodworking, cut pretty patterns in the doors. It looked fancy, kept the computers away from gefingerpoken and kept the computers cooler.
posted by QIbHom at 12:52 PM on November 13, 2006

ISTM that just knocking out the back of the cabinet would be more than adequate, and certainly worth a try before you go hog-wild with fans.

If you don't want to knock out the whole back, just putting a big hole right behind the computer's case exhaust fan, another one behind the power supply fan, and another one through the floor of the cabinet underneath the computer should be OK.
posted by flabdablet at 2:51 PM on November 13, 2006

Thanks everyone. I went to rat shack, bought a smaller 12v power supply and set it up to power both fans. Good to bounce things off of you hive mind.
posted by filmgeek at 9:15 PM on November 13, 2006

P.S. the back already had large holes, they weren't working.
posted by filmgeek at 9:20 PM on November 13, 2006

If the roar of the new fans becomes troublesome, something else you could try is taping a couple of short ducts to the back of the system box, one behind the power supply fan and one behind the case exhaust fan, to lead the air from those fans straight out the holes in the back of the cabinet. The ducts don't need to be fancy - folded cardboard would work. Use short offcuts of PVC sewer pipe if you want something more deliberate-looking.

That way, the existing case fans will exhaust the warm air from the cabinet and force cool air to be drawn in to replace it, instead of letting the same stale warm air recirculate.
posted by flabdablet at 9:44 PM on November 13, 2006