[Electronics] voltage adjusting

Discussion in 'Chit Chat' started by sorex, Jun 22, 2019.

  1. sorex

    sorex Expert Licensed User


    A few days ago I digged into an old server in our server room.

    I recuperated a nice 210+CFM / 6500RPM / 65db / 35W 12x12x3.8cm fan out of it.

    While this beast blows everything from my desk when feeding 12V to it I was wondering how I could adjust the voltage of this so that it operates about at half the speed/noise.

    I know the oldskool potentio or fixed resistor method but then I don't know how to calculate which max K resistance value I need.

    Are there electronic methods as mini boards aswell that can act as a stepper voltage relay kind of thing that can be triggered by a raspberry pi?

    I tried to use one of the 2 USB ports on the solar controller but the limited amperage doesn't seem enough to let the fan spin at 5V.

    Alternatively I could look for another fan aswell that does 120CFM or so at 30db
  2. sorex

    sorex Expert Licensed User

    forgot to mention that the fan had a 4 wire connector so it's PWM based. that could be the reason why 5V fails since it needs 12V pulses to control the speed.

    so I need a PWM controller board to get this working?
    Last edited: Jun 22, 2019
  3. Johan Hormaza

    Johan Hormaza Active Member Licensed User

    You can use this circuit

    Attached Files:

    Johan Schoeman likes this.
  4. Cableguy

    Cableguy Expert Licensed User

    PWM is a bit over kill... A simple 3 component circuit using a 7806 should do the trick

    I didn't see the 4wire post... So athe proposed circuit should do the job
    Last edited: Jun 22, 2019
  5. sorex

    sorex Expert Licensed User

    I'm not good with electronics so something ready made would be the best I guess. :)

    There are PWM boards on aliexpress for 1 to 5 euros but most of them have 2 leads going to the 'motor'.
    Not sure if that is enough for this PWM fan tho. one extra pin is for the tacho/rpm and one for PWM.
    not sure what the PWM on is needed for tho if you could do it on the main 2 pins aswell.
    Johan Hormaza likes this.
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