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Linking power-on switch to external fans...

PostPosted: Thu Jun 12, 2008 10:09 am
by Thrustwyn
Hi all -

Here's a bit of a different question, I think...

I want to place a small form factor PC inside a small wooden cabinet that I expect will not have very good ventilation.

My idea is to cut some 80 or 120 cm holes in the sides of the cabinet to install some PC fans to move air through the cabinet (point to emphasize: I am talking about the wooden cabinet in which the PC will sit, not the PC case itself). :?

Is there a recommended way to power these fans through the PC, and link them to the power button, even though they would be external to the PC case? Roughly, I picture running molexes through a hole in the case (seems crude), in which case I guess they would power on automatically with the PC. :?

Or, is there a way to power these PC fans without connecting them to the computer (i.e. is there a power adapter available that one can power from a regular outlet, and runs these fans?). That way, I could ventilate the same cabinet without turning on the computer, in case I put my PS3 or something in there...

All ideas welcomed!

PostPosted: Thu Jun 12, 2008 10:46 am
by thomas_w_bowman
If you are using a UPS (Battery backup), many have non-backed up plugs that switch on when the main power is turned on, you'll then want 120v AC fan(s) <assuming USA, for much of Europe you may want 220-240v AC>. I do this for my sound amp (about 300w/ch) by using a switched output on my preamp because the wife wanted it in a very tight cabinet and it was heating to well over 140F - now it stays about +3 to +5 over room temp (typically 72F).

A multitap surge suppressor would serve the same, and either would allow for any device inside the box to be cooled (like a PS2), but I personally value a nice 1200VA or larger UPS because brownout during a HD write can make quite a mess, as can even a short power outage. As long as you avoid using the PC and PS2 at the same time a smaller (like 1200VA) UPS could back up either one - to run both at once I'd look at perhaps 1800VA or larger...I back up the monitor (how can I shut down gracefully when blind ?), but not a laser printer or external lighting, or even scanners - surge suppressor yes, but not UPS - UPS is used only for 'mission critical' stuff (like my wife's Gammill Long-Arm Quilting machine with computer regulated stitching - it's only 350W).

Another possibility is to run a connector from the Power Supply (the +12v, naturally then needing a 12V DC fan) perhaps using an extension for power supply cable, or perhaps simply soldering wires to +12v and GND. I'd look at 'sneaking' the wire out the back panel making sure to avoid sharp edges that may fray insulation - or you could always just drill a hole. I'd also be tempted to run the 12v to either a 'cigarette lighter' adapter (as used in cars) or a smaller set of plugs such as are often used in motorcycles - then when unused there would be minimum danger of wires crossing (short), and it would allow the PC to easily be removed from the cabinet (but might not work so well got PS2).

PostPosted: Thu Jun 12, 2008 12:56 pm
by Thrustwyn
thomas_w_bowman wrote:Another possibility is to run a connector from the Power Supply (the +12v, naturally then needing a 12V DC fan) perhaps using an extension for power supply cable, or perhaps simply soldering wires to +12v and GND. I'd look at 'sneaking' the wire out the back panel making sure to avoid sharp edges that may fray insulation - or you could always just drill a hole. I'd also be tempted to run the 12v to either a 'cigarette lighter' adapter (as used in cars) or a smaller set of plugs such as are often used in motorcycles - then when unused there would be minimum danger of wires crossing (short), and it would allow the PC to easily be removed from the cabinet (but might not work so well got PS2).

I think this part holds the answer... so if I read you right (and make sure to tell me if I am not), I could use, say, a cigarette lighter adapter (12V DC), then take the wires from the fan that would normally connect to the molex, and solder those on to the wires from the cigarette lighter adapter...? I do prefer that kind of idea, since then it gives me independence from the computer, and whether it's on or not...

Can you let me know if I have the right of this?

PostPosted: Thu Jun 12, 2008 3:17 pm
by whiteboy
If you might add more then the computer, maybe consider a adjustable transfomer from radio shack or another store. plug it in a standard wall outlet select DC output ( i think they go from 2.5v up to 18v) all you need to do is strip the end off and wire the fan(s) up to it or you can find a matching plug and wire the fans up that way. being adjustable you can change the speed of the fans and hence change the sound level if needed. you can always plug the transfomer into a switched outlet on strip or a power command center so you can turn it on when you need it.

just my 2 cents

Re: Linking power-on switch to external fans...

PostPosted: Sun Jun 29, 2008 3:59 pm
by MrCraigCraig
Thrustwyn wrote:Hi all -

Here's a bit of a different question, I think...

I want to place a small form factor PC inside a small wooden cabinet that I expect will not have very good ventilation.

My idea is to cut some 80 or 120 cm holes in the sides of the cabinet to install some PC fans to move air through the cabinet (point to emphasize: I am talking about the wooden cabinet in which the PC will sit, not the PC case itself). :?

Is there a recommended way to power these fans through the PC, and link them to the power button, even though they would be external to the PC case? Roughly, I picture running molexes through a hole in the case (seems crude), in which case I guess they would power on automatically with the PC. :?

Or, is there a way to power these PC fans without connecting them to the computer (i.e. is there a power adapter available that one can power from a regular outlet, and runs these fans?). That way, I could ventilate the same cabinet without turning on the computer, in case I put my PS3 or something in there...

All ideas welcomed!


In the wooden cabinet install small fans from a hardware store (the type used for venting bathrooms, some of these can be quiet too).
Power the fans with A/C current.
Use a surge-protector as your 'master switch'. When you turn the surge-protector power-switch to the "ON" position, it will supply power to the fans and to the Personal Computer simultaneously.
Alternatively, you could wire it into a household light-switch mounted on the desk or in a wall.

For something quick & easy, try this Heating and Air Conditioning Duct Booster Fan.
http://www.improvementscatalog.com/product/code/49254.do?cm_mmc=Shopping-_-Furnace/Registers-_-2008-_-49254&code-macs=MP8DL08&code=MP8DL08

More food for thought...
http://www.continentalfan.com/resid.htm