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5channel fan controller with one control knob

Discussion in 'General Electronics Discussion' started by Dulus, Jul 15, 2014.

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  1. Dulus


    Jul 15, 2014
    Hello everyone,

    i will skip directly to what i need.
    I have 5 pieces of 12 volt 12cm FANs with 0.23A draw each. They are 3 pin fans. I need to have some sort of control for rpm of those fans. Starting voltage of those fans is 5V. the control should be 1 centralized for all 5 fans.

    I have found designs on web but they are either controls for one fan only or separate control for each fan.

    I am not that skilled in electronics design so i need some guidance. I solder frequently so that wont be a problem.

    Is there anyone who can point me to some , or make some design for me ?
    The whole thing should be as small and simple as possible. I need to feed power into it with 5 separate lines (each for one fan, plugged into MB with 3pin male fan connector) and the output should be 5 female 3pin fan connectors. I still need to feed back the rpm readings from fans to motherboard.

    if thats too much, what is the simplest way to decrease the voltage on each of those power lines to lets say 6 volts ?
    i know it can be done using just an inline cca 50 Ohm at least 2W resistor, but thats a little dirty solution to me.

    Thanks in advance.
    Last edited: Jul 15, 2014
  2. Gryd3


    Jun 25, 2014
    Computers will control fan RPM with PWM. This is essentially switching on and off the voltage incredibly quickly to average a lower voltage.

    There are software solutions you can implement to decrease the speed at which your fans run.
    If using a resistor inline with the fan is a dirty solution, the only other option aside from software that I can think of is building your own PWM fan controller. You would directly control fan RPM...
  3. Dulus


    Jul 15, 2014
    Ah, i should have mentioned that. This is not a solution for computers. I am deploying a few cisco routers , but they are located in rooms where people are living. so no bios/sw rpm regulation is possible. They just run at full speed on 12 volts. And they were very loud so i cut the top cover and made holes for those 12 cm fans there. But even at 1400 rpm the aerodynamic noise from those 12cm fans is audible. those routers have classic 3pin connectors so i guess no pwm.
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    PWM should work fine for them. Look for a circuit on the internet using a 555 and a mosfet. With an adequately specced mosfet this will be able to drive all the fans in parallel.

    Show us what you find and we can comment on the design.

    I'd suggest something better but I'm on a train without good internet access :)
  5. Dulus


    Jul 15, 2014
    I was trying to search something on internet, but all i found was a controls for one power line only...
    To better understand what i want to achive i have quickly put together this picture. The one potentiometer on the top should control the output voltage (and thus rpms) of all 5 fans. I have this in Dia , so i can share it with you.

  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    Your simplest option is a PWM circuit driving all five fans in parallel. Here's a diagram I found:


    This circuit will emit some interference. This can be minimised by inserting an inductor, e.g. 100 μH and rated for the maximum fan current, between the point where D3 and Q1's drain join together and the wiring that goes off to the fans. Also, using screened cables (with the screen connected to the +12V side) between the circuit and the fans should help.

    If you add your location to your profile, and tell us which component supplier(s) you prefer, we may be able to suggest some alternative components that are cheaper and/or more readily available.
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