Motors at 24V, everything else at 12V?



  • Is there a way to have the motors run at 24V and everything else (fans, hotend, etc.) run at 12V?

    Currently my Duet WiFi is connected to the 12V power supply, but my motors are 0.9 degree, and they run best at 24V. I also have a 24V power supply.

    If it is possible, then how do I connect both power supplies to the Duet?


  • Moderator

    The fans can easily be supplied with it's own 12V supply independent of the rest of the system using the V_Fan pin.

    The hotend, however, would be a problem as there is no advisable way of reducing the hot end heater voltage.

    I would suggest that the best course of action is to simply source a 24v compatible hotend heater cartridge. They only cost a few dollars.

    The bed heater if it is DC powered may be 24v compatible with some wiring changes. If it's an AC heat bed run through an SSR no changes are needed as long as the SSR is 24v compatible, and most used for 3D printers are.



  • I run 24v into my duet for the steppers but I power my fans and Hotend from a separate 12v rail off an atx supply. Common negative of course. I only connect the negative wires from the Hotend and fans to the duet pwm pins and have no dramas



  • @gavatron3000 said in Motors at 24V, everything else at 12V?:

    I run 24v into my duet for the steppers but I power my fans and Hotend from a separate 12v rail off an atx supply. Common negative of course. I only connect the negative wires from the Hotend and fans to the duet pwm pins and have no dramas

    I don't understand how you do that? where do you connect the 24V and where the 12V? do you have a diagram or picture?

    My heat bed is a 110V silicone heater, and I use a solid state relay.

    About the hotent... well I have 6 of them (so far):

    0_1550172039666_2018-12-07 20.04.34b.jpg


  • Moderator

    @cvmichael said in Motors at 24V, everything else at 12V?:

    I don't understand how you do that?

    The Duet switches PWM on the ground side, so the live side could be supplied independently.

    I guess if you have a lot of hotends to modify it will be a toss up between the complexity of wiring, or simply replacing the hotend.

    @gavatron3000 do you use a seperate inline fuse for the hotend?



  • Basically, you wire the Duet as normal for 24VDC wiring, but for the negative supply (ground) you wire the 12V supply to that, too.

    Anything that you want to run off of 12V (Hot end, heated bed, fans, whatever) you supply +12VDC from the other supply, and wire ONLY the negative ground to the Duet. Do not wire the negative side to your 12VDC power source, or else you will lose switching control.

    The Duet does not actually switch the + side of the connections, they are constantly connected to positive voltage (Usually V_in, or in the case of the fans, V_Fan which fan be V_in or +5VDC, depending on the position of the fan voltage jumper.

    That fan voltage jumper is another way that you can switch the fans to run off of 12V as well, if that's what you want. This makes connecting the fans a little easier, since most of those have a simple 2 pin Dupont connector on them, and I highly recommend connecting the +12V power supply to the V_Fan center pin. DO NOT UNDER ANY CIRCUMSTANCES let the +12V power touch the 5V side of that jumper connector.

    Hotends and heated beds generally have separated wires, so having a 12V "bus" alongside the Duet is simple enough for those accessories. It's a little more complicated for fans and the like, which is why I recommend the method above for those.

    Another method for running the hotend or heated bed on 12V is to use an external MOSFET. On my MBot clone printer, my 24V supply wasn't enough to run a heated bed, and I had a heated bed and power supply up to the task, so I used an external MOSFET to run that. (This s not running on a Duet. At least not yet. I have been considering it.)

    If re-wiring is possible, and your 24V power supply is up to it, I strongly recommend 24V for the heated build platform. It heats so much faster, the difference is astounding. Mains powered bed heaters with a SSR improve that yet again.



  • @phaedrux said in Motors at 24V, everything else at 12V?:

    @cvmichael said in Motors at 24V, everything else at 12V?:

    I don't understand how you do that?

    The Duet switches PWM on the ground side, so the live side could be supplied independently.

    I guess if you have a lot of hotends to modify it will be a toss up between the complexity of wiring, or simply replacing the hotend.

    @gavatron3000 do you use a seperate inline fuse for the hotend?

    Yes I have a seperate fuse on each rail voltage. I have 24v 12v and 5v on my machine for various things mainly because before I had a duet I used to run a ramps 12v setup from an ATX supply then when I upgraded to the duet I installed a DC to DC converter upto 24v so the stepper driver's were ran at what was recommended


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