Generic pin for PWM



  • Hello!

    Basically, I want to connect a PWM controlled pump to act as a fan. And if possible i would like to avoid using a PWM fan output as it is 12V (and yes, i know i can use a simple voltage divider). But i thought that there must be a more elegant way to do this.

    I found https://forum.duet3d.com/topic/3372/map-general-pwm-i-o-pins-on-extension-header-as-fan but am unable to figure out how to actually do this?

    Any pointers?


  • administrators

    The fan and heater outputs are open drain (i.e. the fan mosfets connect the FAN- pin to ground), so you can make them whatever voltage you want, by not using the VFAN pin.



  • Ah, yes. However, since i want 12V PWM to the other fans. That complicate things a bit for me. Well, unless i create a driver stage that handles all fans, but that seem overly complicated 🙂



  • @janjoh 12V on 24V power supply? Is that your problem?
    If yes you can simple remove the V_FAN jumper and supply 12V to the middle pin in this header. Then all you fans will be get 12V.
    And easiest way to get 12V from 24V is using a step-down module.


  • administrators

    @janjoh said in Generic pin for PWM:

    Ah, yes. However, since i want 12V PWM to the other fans. That complicate things a bit for me. Well, unless i create a driver stage that handles all fans, but that seem overly complicated 🙂

    If you want (say) a 5V PWM output, just connect a resistor (e.g. 1K) between the FAN- pin of your chosen fan connector and +5V. Do not connect anything to the V_FAN pin of that connector.



  • @dc42 said in Generic pin for PWM:

    If you want (say) a 5V PWM output, just connect a resistor (e.g. 1K) between the FAN- pin of your chosen fan connector and +5V. Do not connect anything to the V_FAN pin of that connector.

    Groaaaaaaaannnnnn... now i feel so.. INCREDIBLY stupid.... GAAAh..

    But thank you. 🙂


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