help making basic cicuit with cpu fans

Discussion in 'The Projects Forum' started by Bowerbird100, Nov 11, 2014.

  1. Bowerbird100

    Thread Starter New Member

    Nov 11, 2014
    My name is Cody and i am currently doing year 12 at school.
    as part of my course i need to create a practical "thing" from initial idea through research and protoyping to come out with a final product.

    I this endeavour and need to make a what i see as basic curcuit with very little prior knowledge of electronics.

    i have 6 fans and i am not sure which will be used in the final project:
    2x 120mm 12V DC 0.36A
    2x 12omm 12V DC 0.16A
    1x 120mm 12V DC 0.25A
    1x 140mm 12V DC 0.25A

    I require the circuit to run all fans from wallpower 240V AC ( no idea how to find the right power supply)
    they need to have an on and off switch (i think i can do myself)
    and a way to turn up and down the rpm of the fans ( i assume change the power going into them with a resistor???)

    If i can id also like to have the unit have a plug so that the powersupply isnt always connected to it and can be replaced for unplugged from it so some sort of plug.

    Would anyone be able to help?
  2. ScottWang


    Aug 23, 2012
    It sound likes you need a AC220V to 12Vdc adaptor, and a oscillator and a 12v pwm fan control, you can google about that, and after your research then talk about what you got.
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    It would help if you tell us a bit more about each fan. 2-wire or 3-wire? Maker's name? Model or ID code? How many fans will be running simultaneously?
    If all 6 fans were on at once they would draw a combined running current of ~1A. If they are the usual brushless type (BLDC) then start-up current would not be much more than that, so a 12VDC 2A supply should suffice.
  4. wayneh


    Sep 9, 2010
    I just did a project involving computer case fans. And they're not all the same. 4-wire fans are common and have PWM capability built in. They respond to a 0-5v control signal, allowing easy control by software in a computer application. I think this type would simplify your project since generating a 0-5v control signal will be easier than generating a PWM signal at 1A.
    But you can use 2 or 3-wire fans also. The 3-wire fans just add a wire for a tachometer signal, which can be left disconnected.