12v fans on 24v Duet wiring



  • Hi,

    I have my new Duet hooked up to a 24v PSU and I want to use 12v (silent) fans, specially for the e3d v6 hotend.
    I have read that you can connect a 12v step down to the fan v_in, but what is a good spot to connect ground?

    Sorry if this has already been answered elsewhere. I used the search function and all I could find was "connect step-down to fan v_in".



  • Common ground for 24v and 12v is fine.



  • oh there are topics on this, sure enough, search for "12V fan 24V".
    Here's one: https://www.duet3d.com/forum/thread.php?pid=30375#p30375



  • @whosrdaddy:

    oh there are topics on this, sure enough, search for "12V fan 24V".
    Here's one: https://www.duet3d.com/forum/thread.php?pid=30375#p30375

    Thanks, but non mention where to connect ground. Maybe because it's too obvious, it's just not that obvious to me.



  • @krzaku:

    Common ground for 24v and 12v is fine.

    Thanks, but where would that be for the output ground of the step-down? Any ground connection on the board?



  • If you have a free V- position on your PSU, you could connect it there…


  • administrators

    Normally the input and output grounds of the step-down converter are connected together internally. Use a multimeter to check. So you need only connect one of them.



  • Here is a link to what I used to run my 12 volt fans from my 24 volt duetwifi board.

    https://www.amazon.com/gp/product/B01GJ0SC2C/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

    I wired them straight to the fan connectors on the duet. (pos. to pos. and ground to ground.) They work great that way as long a you don't pull more than 1.5 amps, that is all the load the mosfets can take.



  • @dc42:

    Normally the input and output grounds of the step-down converter are connected together internally. Use a multimeter to check. So you need only connect one of them.

    @whosrdaddy:

    If you have a free V- position on your PSU, you could connect it there…

    Thanks!



  • @timcurtis67:

    Here is a link to what I used to run my 12 volt fans from my 24 volt duetwifi board.

    https://www.amazon.com/gp/product/B01GJ0SC2C/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

    I wired them straight to the fan connectors on the duet. (pos. to pos. and ground to ground.) They work great that way as long a you don't pull more than 1.5 amps, that is all the load the mosfets can take.

    Those are almost identical to the ones I have. However, if you wire them straight to the fan connectors, is it still possible to control fan speed?



  • At the risk of being redundant I want to clearly spell this out:

    The VIN+ of the regulator connects to your +24V supply.

    The VIN-/GND of the regulator connects to the GND of your +24V supply.

    VIN- and VOUT- of the regulator are the same voltage (GND) and already connected on the regulator, so you don't even need to run a wire to VOUT-.

    If all your fans are 12V, you should connect VOUT+ (the 12V from the regulator) to the middle pin (pin 2) of J3 (Fan Voltage Select) - DO NOT CONNECT ANYTHING to the other two pins (pins 1 and 3). Then connect your fans normally to the fan headers - they will all be 12V, whether switched or unswitched.

    If some fans are 24V and some are 12V, then there should be a jumper between pins 2 and 3 of J3. Connect your 24V fans normally using the fan headers.

    For the 12V fan(s), you need to connect the positive (red) fan lead to the +12V output of the regulator. This connection will not be made on the Duet - you can splice wires together or design a little adapter board if you want to keep the fan's plug intact. Connect the negative (black) fan lead to pin 2 (the "-" terminal) of the desired fan header. Nothing should be connected to pin 1.

    Hope this helps.



  • And yes you will be able to control the fan speed of any fan (12V and/or24V) connected to the FAN0, FAN1, or FAN2 headers.



  • Thanks, I think I am starting to understand


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