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How do I power 12v computer fans?


New Member
Quiet, low power and surprizingly efficient, computer fans are an ideal cooling option for smaller cabinet grows. The only problem is that most computer fans are 12v and not 120v! How do I run a 12v fan on normal household power?

# Computer power supply
(A 145 watt computer power supply is over-kill for a 5-20w fan. Try for something small, like a 75watt or 100watt supply). You could drill holes and mount the power supply inside your cabinet. turn the power supply on and off with the power switch on the back.

# (Carpe-Nox) ... if you have any old cell phone chargers around, they use 12v, same that a pc fan uses, just splice the pc fan wires

# [Editor's note: 120v computer fans can be found. Add a pigtail to your fan and voila.]

Fan ideas
Computer Cables, Computer Parts, Computer Accessories, Computer Adapters, PC Components

ex.) 120mm, 90CFM fan for $11.95. it only uses 5.4 watts - a perfect exhaust fan.

ex.) 80mm computer fan that is thermally controlled. $5.95 - the hotter your cabinet is, the faster it spins.

(Jakestone) PCs frequently run their 12V fans at voltages below 12. 7 Volts is very common. Much below that, there can be an issue of having enough starting voltage to get the fan going. The volume of air being moved is reduced, but so is the noise.

(Jakestone) El cheapo $3 fans are often significantly louder than better fans (say 5+ db) and have a dirtier sound (less whoosh and more whine/ticking). High-end fans generally go for between $10 and $15. Computer power supplies are notoriously noisy (especially cheap ones).

(Jakestone) In general, a larger diameter fan moving a given amount of air will be quieter than a smaller diameter fan moving the same amount of air. So for example, one might buy a 120mm fan that moves more air than you need to move at 12V and run it at 7V instead of running a 80mm fan at 12V. The downside for cabinet growers might be the need to light-baffle a larger hole.

Author: usr, share, bong and JakeStone


420 Member
Here's a Fan controller specifically for pc fans. The controller has a power adapter that plugs in the wall and the 12v PC fans plug directly into the controller to get power. $26 Silenx IXAFCEX Four Channel External Fan Controller at TigerDirect.com


I recently purchased and installed this fan controller.
Unit plugs into wall.
Runs up to 4 fans all controlled individually.
PC fans plug directly into the unit.

Wires from fan controller are only about 2' long.
Blue indicator lights might cause problems in flowering cycle (I used black electrical tape over the LEDs)
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420 Member
Very good tip, I will probably purchase one of them plus 4 80mm fans for my new cabinet I am building.

After hooking these up, I was impressed with it.
2 things though -

1. there are blue l.e.d.s that need to be cut or covered if the unit is in the grow area.

2. I bought 80 mm fans, but I'm wishing I got the 120mm fans with more cfm.


New Member
I saw that they sell also the fan screen with a filter inside. I am wondering if I can replace it with a carbon filter and use these fans for exaust the odor as I am planning to grow with LED PPF 400 so I won't have the heating problem but it's really important for me the odor and the noise.
What about the noise of these fans? Are really noisy the 80mm?
Finally, do you keep them running 24h when you do the 12/12?

Stoned Redneck

Well-Known Member
a person could go to goodwill ect. and get a bag of plug in chargers,like from cell phones,radios.you know, small black things that plug in with a long plugin.anyway just check and be sure it has 12 volt OUTPUT and you should be fine.12 volt is easy to work with as it wont shock you like 120 volts.it will sure spark but won't bite. so check it out i have a sack full of them from old phones ,tool charger ect.i'm a pack rat as well.hope that made sence and helps. c u,todd doh!! sorry for the re-run .i need to slow down and Read the whole story before i add my 2 bits worth... sorry....
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420 Member
I saw that they sell also the fan screen with a filter inside. I am wondering if I can replace it with a carbon filter and use these fans for exaust the odor as I am planning to grow with LED PPF 400 so I won't have the heating problem but it's really important for me the odor and the noise.
What about the noise of these fans? Are really noisy the 80mm?
Finally, do you keep them running 24h when you do the 12/12?

The 80mm computer case fans are very quiet. The only sound is the air whooshing, and at 42cfm, they are quiet. I think it is recommended to keep the fans on 24/7.


New Member
I couldn't help chiming in here as I found a great site with fans, filter screens for them, the centrifugal fans (that's what I need), anti vibrations mounts...

All kinds of stuff we might need for a quiet running exhaust system. I'm going to use the centrifugal blower with a home made, chicken wire carbon filter in addition to a carbon filter behind the filter screen. Noise will be low and hopefully I'll be over compensated for smell..

Here is the link..

Computer Case PC Cooling Fans at SVC.com

I don't have any experience growing yet, just researching the box build. Thought this might be a great place to go.

C H I C A G O - how did you get around the 2' wires from the controller?


New Member
I replaced some 4" AC fans with the 120mm PC fans, much smoother sounding and quiet. I just used an old AC adapter and a single PC fan speed controller.

About the same flow IMO.


New Member

here's a cheap item that, could do the trick if used right.

Question: Once the furnace stops blowing, does this fan still keep going? If so, it would end up sucking in cold air (in the winter). Or is it designed to shutoff once the furnace stops blowing?

Answer: If it's set to the auto function, it will turn off when the furnace fan shuts-down. There is also a "Set Point" control that adjusts sensitivity.


New Member
A couple of notes on using muffin fans. Muffin fans work great if you get a good one. I actually have one on one of my older non air cooled hoods... it whisks air out of the light so the huge fan can take the heat out, and that means the canopy is a bit cooler!

POWERING: You can actually source muffin fans that plug right in to the wall- audiophiles have used them to cool their gear, but these are more expensive than getting 12v PC fans and using either a computer power supply or a 12v power supply (like I do- I have a less fancy version of the fan speed controller that ChicagoJoe posted in 2010).. I feel the old cell phone charger method is more prone to danger even though a 12v line won't fry you.

NOISE: Since we can opt for a cheapo PC fan, we have to be careful not to go TOO cheapo, since cheap fans use inferior ball bearings, making them noisy and prone to breakdown. A good, quiet, and not too expensive brand is "Noctua"

It is a bit counter-intuitive, but the larger the fan, the less noise it makes while moving more air! I ended up getting about a 4" model, since my old hydrofarm hood has a vent exactly that big, but a 92 or 120mm would be way quieter.

In the quest for quiet, you will want to install little rubber grommets that act as sound dampeners, or suspend the fan from rope or something. For a cabinet, use rubber insulation around the fan to reduce noise.


As was mentioned, make sure you get a light without the obnoxious useless LED- it's shocking that more fans nowadays seem to have LED's than don't.
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New Member
I found a model train/railroad power packs are great for powering 12VDC fans. they are basically DC variable voltage regulars output is around 0-18VDC. this allows you to control the speed too some like the one I use also have 12VDC and 18VAC hook ups for lights etc around the tracks that could be of use too.


New Member
The cell phone charger is never 12v. The output is almost always 5 volts. You might find a laptop charger around 12V.

Yup, cell phones are single cell lipos @4.2v, so 5v is plenty for charging.
Pretty much any 7.2v upwards wall wart will do the jobby, I keep em all as I left shoulder old electronics and appliances. Always useful one day.
Cheers n Peace


New Member
Anyone out there to help? I wanna run 4 pc fans, connected to a pc 4 channel fan speed controller, connected to one pc power supply, plugged into wall...
Am I missing something? Any reason why this won't work? Or is there some modification to the molex plugs or whatever to make this work without motherboard...
Wanna cut down on wall plugs, fan noise and fire risk(by not using phone chargers etc). Will post this elsewhere also as I can't find anything anywhere..
Cheers in advance.
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