12V fan pwm control (external PSU)

  • Hi,
    I have a duet+duex5 setup, with a 24V psu for steppers and print/hotend fans, a 5V psu for the boards, relays etc, and a 12V psu to power the board's cooling fans (which are basically PC 4-wires fans).

    I just noticed yesterday the virtual heaters feature, and was wondering if i can control the 12V fan's pwm from the duet ? I "feel" like there is a problem somewhere to connect just the pwm wire of the fan to the board if there is no common ground between the board and the 12V psu, but i'm really not sure !

    Can someone tell me if there's a way to do it ? or it's a clear "nope, don't do that" ? 🙂

    In the end it'll help a lot to decide between 2 fans for board cooling :

    • one is a very powerful Sunon blower that is so noisy that it absolutely needs pwm control (but a lot of cooling capacity if needed)
    • the others are two PC artic 80mm fans that i can leave 100% all the time if pwm control from an externally powered fan is not possible.

    Thanks 🙂

  • @tpra Yes that's kind of what I do. In my case I have a 24v power supply and use a 24DC to 12V DC converter, rather than a separate PSU. I connect the fan positive to 12v and the fan negative goes to the negative side of the Duet/Duex. I've actually attached a thermistor to the top of one of the driver chips then have the fan set to run in thermostatic mode by use PWM to ramp the fan speed depending on temmperaure.

  • Thanks 🙂
    in your case isn't the 12V ground "linked" to the 24V ground and board's ground because of the converter ? that's what worries me on a separate psu.

    I can read a user manual, but i'm really not an electronics specialist at all, so i'm completely lost when it comes to such things 😕

  • administrators

    Yes you would need a common ground between the 24V and 12V PSUs. You can add a ground wire between them is there isn't one already.

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