5v PWM fan with tacho and diode



  • Hi,

    I've been reading up on connecting fans to the Duet 2 Wifi, and I'm trying to figure something out. I'm planning to connect a 5V PWM Noctua fan that has a 4-pin connector - which means that it has tacho feedback. According to the wiki this could be connected to PB6 if a suitable diode is used "between" the PB6 pin and the tacho wire. I found a post explaining that this is to avoid getting 24v or 12v into PB6 and protect the Duet in case the ground wire of the fan should become disconnected. But if I'm using a 5V fan - I'm guessing that the voltage that could get dumped into PB6 would be 5V? Does that mean that a diode is not needed for a 5V fan, or should I use one anyway?


  • administrators

    You should still use a diode because the maximum input voltage on PB6 is +3.3V. However, in practice a 10K resistor should work too.



  • Ah - I understand 🙂 But a diode would be the safer choice?


  • administrators

    @johgis said in 5v PWM fan with tacho and diode:

    Ah - I understand 🙂 But a diode would be the safer choice?

    In theory yes, as long as you connect it the right way round.



  • Got it. Thanks!


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