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LED fans are an easy way to add color to your rig, but they are missing something crucial, a light switch. I've got four 120mm blue light up fans and they move some serious air. Their LEDs are pretty bright and have no problem illuminating my room a fair amount. Putting a small light switch on the LED's lets me turn the lights off so I can sleep and keep the fans running for my hard drives. Real easy mod, and real cheap

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The real motivation for this project comes from a previous project, my new projector. To maximize quality you need an absolutely dark room. I know the lights from the fans are so small and they really don’t make a difference, but when watching the screen they are right in your line of sight, I wanted to turn the lights off while keeping the fans on.


I wanted a way to turn off the LEDs in my Aspire 120mm blue fans without cutting the power to the fans. If you have soldering and wiring experience this will be simple. It does require some soldering in tight corners but very doable nonetheless. Before attempting this please go over the schematic for your particular fan model, I doubt all fans have the same design and circuitry. That being said the basic circuit with my switch in it looks like this:


*Correction* I received a few comments about back power. Back power can cause unnecessary power consumption and circuit damage. I should have put the switch on the 12+ side before the LEDs this would have fixed that. Thanks to all for the comments, the only way you’re going learn is through mistakes.

You can see that the LEDs and Fan motor are run in parallel, which makes things very easy. The LEDs are also in parallel, which is a bit of a pain, but that is the most effective design so it makes sense. You need to put a switch in to cut power to the left half of the circuit. This is not as easy as I’ve shown here, however. The ground connections for the LEDs do not link to one central point and therefore must be connected for simplicity.

What you'll need

Part Cost/Unit QTY Total Link
Aspire 120mm LED fan $10 4 $40 --
Small 2 position switch $0.75 4 $ 3 --
Small gauge Wire (22gauge maximum) -- -- -- --
Epoxy -- -- -- --
Soldering iron -- -- -- --
Solder -- -- -- --
1/4" work cloth -- -- -- --
Wire cutters -- -- -- --
Total -- -- $10* --
  • assuming you have a soldering iron, fans, epoxy, wire cutters. Work cloth optional

Check out amazon.com for soldering irons and other parts you might need


1. Remove the Sticker – first things first, remove the sticker on the back that has the main power wires running in. You should see a circular circuit board with four connections on the outer edge for the LEDs.

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2. Methodology – There are two different methods to wiring this up; a clean way and a messy way. I chose the clean way, which is a bit more difficult, so that’s what I will explain here (the messy way is pretty obvious).

You should notice that there is a plastic backing that covers most of the circuit. What we want to do is feed all the wires under this plastic backing to hide as much of the wiring as we can, to produce a finished product that looks manufactured, or at least not ugly.

3. Feeding and soldering wire # 1– You first want to cut two long lengths of wire of different colors, preferably small gauge wire. I initially used a solid 22 gauge but that proved un manageable so I went with a smaller gauge that was stranded ( I don’t know exactly what size it was because it was given to me for free from a friends garage). Strip the ends, not a lot, just enough where you feel comfortable soldering

Focus on one LED at a time. Thread one wire under the plastic and position the bare wire tip over the ground connection point for one of the LEDs on the circuit (it will have a wire running to the LED and the one next to it should be labeled as “+”). Make sure you are not going to join any other connections or touch any other wires, and then solder it in place. Take out as much slack in the wire as you can, running the wire down the main spline that the main power wires are located to the outer edge of the casing. Leave at least an inch or two of wire on the end and cut the remaining wire for the next LED.

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Fan_light_010_00.jpg 4. Feeding and soldering wire # 2 – Using a different color of wire, thread a strand under the plastic and go all the way down the spline closest to the LED you are working on. You should first cut the ground wire for the LED that runs along the spline and make a note of which lead that connects to on the LED. Run the threaded wire up to the LED itself and solder it to the ground lead. You should now have two wires in place of the one ground wire for the LED. You should test your connection right now to make sure all solder joints are compatible. When you turn the fan on that LED should be off, by crossing the wires you just soldered up, it will turn on.

5. Repeat 3 and 4 for the remaining LEDs

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6. The switch – This part should be self-explanatory. Solder all the wires of the same color together (the same color wires should be going to the same locations for each LED for simplicity). You might want to test these connections as well before adding a switch, I had mixed up a few of my colors and got a bad connection once. Solder a single strand to each bundle to make an easy connection to you’re switch. (see step 7 for further design options and considerations). Now solder the two leads to the switch (this will depend on the switch you buy)

(for these pictures i didn't use my color technique, i should have though)

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7. Further ideas – you may consider putting a long length between the bundled wires and the switch so you can put the switch wherever you like around your desk.

Here i used 3 conductor insulated wire (it was cheap and easy at the time) and extened the switches. I duct taped a bundle of fours switches and put them under the leaf of my desk (very classy)

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Here you can see the four fans i've bunddled together. My four hard drives won't fit in my small case so i moved them outside and put four huge fans blowing across them....overkill…of course. The noise isn't too bad, I'm used to it.

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I made a small box out of ABS plastic and mounted the switches in it

Here are some pictures of the project

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Here are some completed shots. I used 2 Velcro strips to attach the box to my desk. It holds pretty well and can be removed if i need to.

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You might have noticed that I was too cheap to buy real fan grills so I used work cloth (wire mesh) squares wired to the backside. They work great, and are real easy, especially if you have some extra mesh and wire lying around.

Sources and inspiration

I’m sure there are plenty of people out there who have done this before. I bet its a lot easier to do for different fans, and I’m sure some fans are installed with them already. But if you are stuck with the fans you got, make them into something better.

Further Ideas

sweet cold cathode fans

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I think these fans are would be pretty sweet, so i think i might get some and play around, see what i can do...I’ve never worked with cold cathode before so it should be fun..

Check out this page on digg.com

or post it on del.ico.us