12V Fan connections from 24V PSU



  • Hi All,
    Based on what I read from the threads, I think this is how I will connect 12V fans from 24V PSU using buck converter. Please have a look at the picture and let me know whether it is correct. I do not want to blow up anything.

    I will connect the positive and negative from 24V PSU to the respective terminals of buck converter input side. I connect the positive terminal from output side of buck converter to the positive terminal of the fan. I will connect the negative terminal from the output side of buck converter to the negative terminal (GND) of Duet Wifi Power input.

    I will then connect the negative terminal from the fan to the negative pin of the "FAN 0" terminal for PWM control. I hope I have understood correctly from the threads and correct me if I am wrong.

    Best Regards,
    Vasan


  • administrators

    Yes, that will work. Alternatively, if all your fans are 12V, then you can remove the V_FAN voltage selection jumper, connect the +12V output of the buck converter to the centre pin of the V_FAN voltage selection block, and connect the fans as normal.



  • Thanks David for your reply! I have mixed fans. I will try to make them all 12V soon and use V_FAN.

    Best Regards,
    Vasan



  • Can you not connect a buck converter directly to the 24v fan terminal? Positive-positive, negative to negative? I want to run a 12v fan for the hot end heat sink (noctua don't do standard 24v fans).



  • @Syko_Symatic:

    Can you not connect a buck converter directly to the 24v fan terminal? Positive-positive, negative to negative? I want to run a 12v fan for the hot end heat sink (noctua don't do standard 24v fans).

    You can, but then you won't be able to use the PWM speed regulation. Duet (like most of the 3d printing controller boards) switches the low side on the fan outputs, so you can use any voltage tolerated by the MOSFETs for the fans as long as you connect the grounds.



  • Hmm… I should be able to mount one onto my PSU as currently I am running 2 x 24v 400w supplies, however, I have bought a 24v 600w supply to replace the 2. I have a 15a heated bed, hence the ridiculous supply! I should have a free terminal on the new PSU as I should now be able to run the bed through the board again (which I believe is 18a max at the bed terminals?).



  • On my little fan I put a resistor of 100 Ohm)))



  • When +12V is connected to centre pin of V_FAN voltage selection block - does it bypass mosfets? Also do I need to connect negative from buck converter to negative of duet wifi? Looks like negative from buck converter output is common on both sides so it's common with negative on PSU as well.


  • administrators

    No it doesn't bypass the MOSFETs; and yes, if the negative input and output terminals of the buck converter are common then you need only connect the input to VIN-.


 

Looks like your connection to Duet3D was lost, please wait while we try to reconnect.