Wiring CPU fans

tfraleigh(Ont)September 16, 2005

Everywhere I read about ventillating vivariums people talk about using CPU fans. This seems like an amazing idea, but i really would have no idea how to wire one up. Anyone have knowledge in this department? Im kinda non-electrically inclined lol, so your help is much appreciated.

They have them listed cheap on ebay, is somthing like this good?

Thanks for your help

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deadhamster(Z5 MI)

Thats actually a case fan, but good enough. It uses 12VDC and is easy enough to wire. I wouldn't bother though. For $20 at Radio Shack you can get a 120VAC fan, which will not need a power supply. If you go with a DC fan like the one you have pictured, you will need a 120VAC to 12VDC converter. Just use the 120VAC fan that radio shack sells. It's easier.


    Bookmark   September 17, 2005 at 1:37AM
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Yea, i saw the link someone posted about the radioshack fan, problem is i live in Toronto, and radioshack got taken over by circuit city here, so I dont think/know if they still carry it

    Bookmark   September 17, 2005 at 11:34AM
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nathanhurst(VIC Aust)

get one of those case fans, and buy a multi voltage wall wart that does voltages from 5 to 12. Connect the positive wires together and the negative wires together (best if you get some one to solder this, and they'll be able to work out which is positive and negative too). Then you can adjust the fan speed by changing the voltage. If you know someone who tends to collect computer junk they'll probably have a fan or two lying around for free (I certainly have a small box of them).

There is a slightly more complex circuit discussed earlier if you want to have temperature feedback control.

    Bookmark   September 18, 2005 at 2:54AM
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Where can you get a wall-wart that allows you to adjust the voltage? Plus, how do you know the proper mA rating for the wall wart? I have seen a couple wall warts, but they are not variable voltage and they are rated for either 500mA or 700mA. I am not an expert electrician, but am fairly competent. I have a 10 gallon terrarium, and need to create some air circulation because I am planning on adding orchids, so I would really like to try and set up a slow moving fan to turn on a couple of times a day.

    Bookmark   January 20, 2006 at 11:28PM
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dmarin(Z9 NorCal)

Well, I hesitate to use 120V fans in my terr. Instead I use cheap 12V fans. What I do instead of wasting money on variable voltage wall-warts is I g oto the box containing all of my older, unused electronics and select a wall-wart to something that I will never use again(we all have about a dozen of these!).

I then cut the plug end off, and connect it to the fan. It's a 12v motor, and won't complain about polarity being reversed most times-it will just spin backwards. If it's spinning backwards, just reverse the wires. Then I use crimp connectors and enough tape to protect the wires from the moisture.

If you want an adjustable wall-wart, go to the Rat-shack. They sell one that is variable voltage and has 2 pins on the end where the multiple adapters plug into it.


    Bookmark   February 4, 2006 at 1:27PM
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I got kinda lucky as the lighting system I bought came with two cooloing fans built in, I just re routed them into the positions I wanted them to be, one cools the lights and one circulates the humid air inside the tank =)

    Bookmark   February 4, 2006 at 2:05PM
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I have one of those multi voltage wall warts that does voltages from 5 to 12, its brand new "out of package" but has all the little adaptor thingys, if anyone has any smaller epi's to trade just let me know! I tried to contact you tfraleigh but you have no contact Info =)

    Bookmark   February 4, 2006 at 4:43PM
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gagnon98(SoCT z6)

Does anyone know how to supply power to this Radio Shack 120VAC fan? So I can just plug it into the wall? Like tfraleigh, I bought a case fan, looks good and all but haven't a clue how to power it up. Looks like it's a bit too involved for someone like me who has no electrical experience or box of spare computer equipment.

    Bookmark   March 7, 2006 at 2:11PM
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deadhamster(Z5 MI)

The radio shack fan can just be plugged into the wall. It doesn't come with a plug though, just a couple short bare wires. You will need to get wire and a plug seperate if you want to plug it into the wall.


    Bookmark   March 7, 2006 at 4:23PM
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deadhamster(Z5 MI)

Here are specific instructions for everyone, as requested by gagnon.

You will need:
Wire Cutters
2 Wire Nuts
1 Extension Cord
1 120VAC Fan
1 Roll Electrical Tape

All are available at radio shack.

Cut the receptacle end of the extension cord off (the end you plug stuff into). Strip off the cut ends of the extension cord with wire strippers or cutters leaving .5" of bare wire. Connect one wire on the fan to one wire on the cord, and then connect the remaining two. Do it by twisting them together a bit. I don't think the fan is sensitive to polarity, so you can connect either fan wire to either wire on the cord. Twist a wire nut over each spliced connection until it is tight, and tape the hell out of it.

If I am wrong and it is polarity sensitive, it will spin the wrong way or not at all. Just swap the wires. There are arrows on the fan that indicate the direction it spins and the direction of the air flow.


    Bookmark   March 8, 2006 at 12:00AM
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gagnon98(SoCT z6)

Thank you very much DH. Unfortunately, for some like me, it takes those step-by-step instructions to get the job done.

I appreciate the easy to follow directions!


    Bookmark   March 8, 2006 at 1:49PM
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This is my first time posting here, so 'Hello'.

I have a 25 gallon terrarium that I have had to redo 3 times due to mold and most recently mushrooms. It is my first terrarium (I always pick hard projects). Anyway, this forum has been so helpful for me, and the information about the fan was the most helpful.

I had planned to get a CPU fan and follow all the splicing directions, until I came across a small 12 volt fan at a website that I order stuff for my cats called Drs Foster and Smith (see link). It is an 'Aqualight Cooling Fan Kit' by Coralife. (They have a couple of other options, too.) It's a 3 1/8' fan, and it has a 12 ft. power cord. It's about $19.00. It doesn't have variable speed, but creates a gentle breeze and is very quiet. I just used wire to attach it to the screen cover I use.

I hope this info is helpful to someone.

P.S. You'll find the fan in the Reptile section under Habitat Accessories.

Here is a link that might be useful: Drs Foster and Smith

    Bookmark   July 14, 2007 at 7:32PM
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deadhamster(Z5 MI)

And the thread continues. I received an email today wanting to know how to use a spare computer power supply to power the 12vdc cpu fans. So here it is...

ATX power supplies don't power the 12v rail unless the motherboard tells them to turn on (power button) so you have to either jump the wires or connect a switch. If you are even reading this, you should be savvy enough to know how to do either. I'll just tell you where to do it. The 14th pin on the ATX connector is the POWERON pin, it is also the only green wire in the bunch. Jump it with pin 15 (common), its the black wire right next to it. This will tell the power supply to turn on. If you want to use a switch instead of a wire to jump it with, knock yourself out. I would reccomend a normally open momentary push button, the same kind of switch on the front of a modern computer. Hopefully this helps a few people.

Here is a pinout table.


    Bookmark   September 23, 2007 at 1:16PM
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