Instructables
This instructable should help you build a simple 3 speed fan controller for any 12v dc computer fan. I couldn't find a decent tutorial on fan controllers so i've made this simple one. This is my first Instructable so I hope it's alright :)
Please comment

I can't be held responsible if you break stuff, i have tried to describe things as thouroghly as possible but if stuff breaks it's your fault not mine . None of my stuff broke

The 3 speeds will be off, half speed and full speed
Being able to turn case fans off helps you keep your computer quiet when you don't require the extra cooling, the two fan speeds allow you to turn the fans up when necessary and dow to keep the system quiet while still cooling

You will need:

DC fans - I used 2 i bought on Ebay for about £1.50 each from China, they came with 2 wires for power(+/-) Not PWM 3 pin/wire type and a molex plug so they would run at 12v constantly (Loud)
I don't reccommend LED fans, mine were LED and the change in voltage from changing the speed makes them go dim, not a massive issue but you might not want that
An On/Off Switch
A SPDT switch (3 pins underneath on/on)
Some bits of wire
Soldering iron and solder
Electrical tape or Heat shrink
A computer or computer powersupply to give the fans power
Maybe a screwdriver to open your PC case
 
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Hey g199 I was wondering when you said solder the negatives to the on/off switch to which on/off switch do you mean? The computer on/off switch? Figured I had better ask before hand even if it is a stupid question. Thanks!

Nope I think he means the extra ON/OFF switch that you place between the
fan wires and the SPDT ON/OFF switch output wire and molex ground wires. If I'm not mistaken, you could use an SPDT ON\OFF\ON switch instead of adding the extra ON\OFF switch. Also I've read that certain fans will not start from 5V so this might not always work in which case the resistor method could be a valid alternative.

i-blaze2 years ago
Nice and easy instructable g199 :)

But i have 1 QUES g199,
since last few days i have browsed almost as many as possible various diy fan controller projects and most dem had some kind resistors and capacitors and heatsinks etc involved in their projects. Stating it to be useful to use it with diff.. variety fans

That is the reason i hesitate moving further referring those projects coz i was looking for some think simple and effective like u have shown.

SO, i wanted to know is it ok not to use all resistor and capacitor etc... for dis project?
g199 (author)  i-blaze2 years ago
If you're using 12v fans then there is no need for a resistor in this circuit :)
Because the amp draw of pc fans is pretty low you don't need to worry about using relays or anything for the switch
It's a simple idea and it works, so i don't really see the need to add more components because that adds more expense.
Adding a potentiometer is quite a good fan modification, then you can turn the fan speed up and down to any value with a dial type adjuster, but it's a bit more complicated and costs a bit more.
Hope this answered your question :)
i-blaze g1992 years ago
tnx G199 now i feel free to proceed with dis diy project tnx again for the reply :)
cool48752 years ago
nice work.... ive done something same but haven't used the 5 volt rails... just running the fans on 12 volt rails.. plus have mounted them on an acrylic sheet.. i also have added some leds... but am not able to power them up without blowing them :(
here is an image :D its kept upsite down though :P
g199 (author)  cool48752 years ago
If your LEDs are blowing use a rail with less voltage and/or use a resistor, i hope that sorts your problem :)
cool4875 g1992 years ago
ya i know i need to use resistors.. but idk what rating resistor to use for a particular led... i currently have 10 of each red, green, blue and white....
g199 (author)  cool48752 years ago
you can work it out quite easily, just google "led resistor calculator", you'll need to know the voltage rating of the LEDs you're using, if you don't know what they're rated to then assume it's 3V, if they're really dim with 3V try 5V, if 12V is blowing them then they probably aren't 12V or above
cool4875 g1992 years ago
hey i got the blue and white leds to work on the 5volt rails :D
2012-04-27_20-20-48_997.jpg
g199 (author)  cool48752 years ago
Looks good, nice work :)
cool4875 g1992 years ago
ty man will do that for sure... btw m using the 5 volt rail for the led :)
zazenergy3 years ago
Interesting. Thanks for sharing!