Fan with multiple voltages



  • Hi !

    First of all, thanks a lot to everyone in Duet for the wonderful work ! I love this board.

    I'm just facing a simple problem about connecting fans. Here is a description.

    I run my duet with a 24V PSU.
    I also have a 12V/5V dual PSU for other things.
    The two V- of the PSUs are connected.

    Then I have multiple fans :

    • An always on fan to cool the duet (12V)
    • A temperature controlled fan for the hotend (12V)
    • A part cooling fan for printing PLA (24V)

    Since I have one fan which is 24V and the two others that are 12V, I decided I will wire the V_fan pins for the fans to the 12V from my PSU.

    So I attached the 12V to the V_fan and I connected my two fans to two available slots (FAN1- and AlwaysOn). They are working fine (the always on is always on and the other one starts when I heat the hotend).

    Now I have the 24V part cooling fan left to connect and I want to control it.
    So what I did is I connected the black cable of the fan to the FAN0- pin and the red cable directly to the V_in pin that is nearby.

    The problem in the end is :
    When I set the part cooling fan (24V) to 100%, it works. But when I set it to 0%, the fan still spins a bit and my PSU does a wierd noise that I don't like.

    What I have tried :

    • Connect my 24V fans to the 12V like the others : it works and is controled, but I only have half the power on this fan
    • Connect the red cable of the 24V fan directly to the PSU : same problem as above : wierd noise and it runs even at 0%.

    I read this post : https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_fans#Section_Using_12V_fans_when_VIN_is_24V
    and realised you suggest doing the opposite (option 3 : connect the 24V to the V_fan using a jumper between V_IN and V_Fan and connect the two other fans to the 12V PSU)

    I don't understand what this would work better than what I did.

    Thanks a lot.



  • On this old post I found :
    https://forum.duet3d.com/topic/1281/24v-cooling-fans-and-5v-always-on-fan/6

    @dc42 which is the god of this forum apparently says :
    "One thing I should mention for the benefit of future users. When the new Duet WiFi 1.02 boards arrive, they will have flyback diodes to V_FAN included. Then you will need to ensure that V_FAN is the highest voltage that any fan will be connected to. So your scheme of setting the V_FAN jumper to VIN connecting a fan between +5V and a PWM FAN- output would still work. But the reverse scheme of setting V_FAN to 5V and connecting a fan between +12V or +24V and a PWM FAN- output would not."

    So I guess this is the reason for my problem. Can anyone confirm ?
    Do you think I did some damages to my board or my PSU running this wrongly ?


  • administrators

    @fbunel said in Fan with multiple voltages:

    So I guess this is the reason for my problem. Can anyone confirm ?

    Yes, I can.

    Do you think I did some damages to my board or my PSU running this wrongly ?

    No.


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