control PWM fan

Discussion in 'The Projects Forum' started by boschi66, Jul 21, 2011.

  1. boschi66

    Thread Starter New Member

    Jul 21, 2011
    I have a 4 wire PWM fan and I am trying to control the speed and on/off with a control signal which outputs 0-10V dc. Could anyone give me some pointers?
    I have been all over google and the things that come up aren't much help ...

    Thanks in Advance.
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    If it's the fan I am thinking of the control signal has to be PWM of a certain frequency (example 25kHz, but see datasheet of the fan) and speed is being controlled by the duty cycle of this PWM frequency.

    have a look at this link:\specs\REV1_2_Public.pdf

    What's the model of the fan?
  3. boschi66

    Thread Starter New Member

    Jul 21, 2011

    I dont have the model of the fan. But, I think it is the same as those cpu cooler fans. Do you know any converter that would convert 0-10 voltage input to the control signal?

    I have been looking, but, it seems the only way to convert 0-10 dc to PWM signal is to build a converter on my own.
    Let me know if you know any product that can be bought..

    Last edited: Jul 22, 2011
  4. SgtWookie


    Jul 17, 2007
    Here's an easy way to convert that 0v-10v input signal to 0%-100% duty cycle PWM using one IC, 5 resistors and 1 capacitor.

    See the attached.
    The red V(out) plot shows that the duty cycle starts at 0% (off continuously) with 0v in, winding up with 100% duty cycle (ON continuously). I set the simulation for too much time to show the waveform while it's outputting PWM, but you can see with the FFT (green trace, lower left) that the frequency is 25kHz.

    Digikey stocks the LTC6992CS6-1 IC's for $3.81 each.
    kuku427, boschi66 and praondevou like this.
  5. stp715a

    New Member

    May 2, 2011
    Thanks for the circuit. Can you please let me know if the fan speed is variable based on Vin or is it either on or off with any Vin from 1-10V. If the answer is yes (on at any Vin) then how should the LTC6992 be configured to drive the fan at 100% RPM with any voltage between 1-10V?

    Thank you