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How to Wire an External MOSFET on a Mini 5 Plus

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Duet Hardware and wiring
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  • undefined
    random_task_1
    last edited by 13 Jun 2022, 11:08

    I purchase the mini 5 plus to replace a fried skr board in my printer. The heat bed is a MK2 PCB style 300x300 bed. The bed says it is a 400W/18A bed so the specs on the Mini 5 say it will not drive the bed direct from the board.

    I already have a mosfet installed in the printer with power wires directly from the PSU to the mosfet and power wires from the mosfet out to the bed.

    I am unclear where to plug in the signal cable (small gauge (20 or 22) 2 pin JST) from the mosfet and the proper wiring for the duet mini 5 plus.

    I am also open to other suggestions on the best way to wire up the bed.

    I am new to the duet community and I spent a good bit of time searching for this answer on this forum but did not find one, so if this is a repeat feel free to point me in the right direction

    Thanks

    undefined undefined 2 Replies Last reply 13 Jun 2022, 11:29 Reply Quote 0
    • undefined
      jay_s_uk @random_task_1
      last edited by 13 Jun 2022, 11:29

      @random_task_1 you could driver the bed mosfet from the bed heater outputs (don't forget to wire power to the bed inputs), the second heater output or a fan output

      Owns various duet boards and is the main wiki maintainer for the Teamgloomy LPC/STM32 port of RRF. Assume I'm running whatever the latest beta/stable build is

      undefined 1 Reply Last reply 13 Jun 2022, 18:05 Reply Quote 0
      • undefined
        random_task_1 @jay_s_uk
        last edited by 13 Jun 2022, 18:05

        @jay_s_uk
        Ok, thanks for the reply.
        Just to make sure I understand what you said there.
        I would put a + and - wire from my PSU to the Duet Mini 5 Power In terminals.
        Run a + and a - wire from the Duet Mini 5 BED OUT (OUT_0) to the + and - INPUT side of the MOSFET.
        Run a + and - from the MOSFET BED OUT to the normal input on the heated bed.
        Run the JST 2 wire connector from the Duet Mini 5 OUT 1 terminal to the MOSFET Signal connector.

        undefined 1 Reply Last reply 13 Jun 2022, 19:32 Reply Quote 0
        • undefined
          jay_s_uk @random_task_1
          last edited by 13 Jun 2022, 19:32

          @random_task_1 power in to duet mini for the bed power input.
          The 2 wire JST would go from bed out to the MOSFET.

          Owns various duet boards and is the main wiki maintainer for the Teamgloomy LPC/STM32 port of RRF. Assume I'm running whatever the latest beta/stable build is

          undefined 2 Replies Last reply 13 Jun 2022, 19:52 Reply Quote 0
          • undefined
            random_task_1 @jay_s_uk
            last edited by 13 Jun 2022, 19:52

            @jay_s_uk
            ok,
            I think I understand now thank you. will give that a try when I get back to the shop

            1 Reply Last reply Reply Quote 0
            • undefined
              random_task_1 @jay_s_uk
              last edited by 17 Jun 2022, 19:00

              @jay_s_uk
              just to make sure I understand correctly, you are saying it is fine to use the 20 or 22 gauge wire and run from the bed outputs on the duet to the signal input on my mosfet? I have it connected that way but want to make sure I'm not about to fry something.

              1 Reply Last reply Reply Quote 0
              • undefined
                fcwilt @random_task_1
                last edited by 17 Jun 2022, 19:08

                @random_task_1

                I suggest you purchase a suitably rated SSR (solid state relay) . They are designed for this sort of thing are are going to be safer than just a simple MOSFET.

                Frederick

                Printers: a small Utilmaker style, a small CoreXY and a E3D MS/TC setup. Various hotends. Using Duet 3 hardware running 3.4.6

                undefined 1 Reply Last reply 18 Jun 2022, 22:01 Reply Quote 0
                • undefined
                  random_task_1 @fcwilt
                  last edited by 18 Jun 2022, 22:01

                  @fcwilt I'm not opposed to getting an SSR, any suggestions on which one to get? the Duet documents list two options but none are available any longer.

                  undefined 1 Reply Last reply 18 Jun 2022, 22:14 Reply Quote 0
                  • undefined
                    jay_s_uk @random_task_1
                    last edited by 18 Jun 2022, 22:14

                    @random_task_1 large MOSFETs are fine.
                    Wire it like this
                    80d71cca-3a17-4490-a879-8b6e3d053063-image.png
                    Just use out0 in place of where it wires to the ramps board. Make sure you provide 24v power to the power inputs for out0

                    Owns various duet boards and is the main wiki maintainer for the Teamgloomy LPC/STM32 port of RRF. Assume I'm running whatever the latest beta/stable build is

                    undefined undefined 2 Replies Last reply 18 Jun 2022, 22:29 Reply Quote 0
                    • undefined
                      random_task_1 @jay_s_uk
                      last edited by 18 Jun 2022, 22:29

                      @jay_s_uk ok, thank you for that clarification.

                      1 Reply Last reply Reply Quote 0
                      • undefined
                        fcwilt @jay_s_uk
                        last edited by 18 Jun 2022, 22:40

                        @jay_s_uk

                        IF they are optically isolated.

                        I would still suggest a SSR as nothing is exposed.

                        Amazon has these in stock:

                        Crydom D2425 SSR, Panel Mount, 280Vac, 32Vdc, 25A

                        Frederick

                        Printers: a small Utilmaker style, a small CoreXY and a E3D MS/TC setup. Various hotends. Using Duet 3 hardware running 3.4.6

                        1 Reply Last reply Reply Quote 0
                        • undefined
                          Dad003
                          last edited by 18 Jun 2022, 23:53

                          just be aware that some of these mossfet get really hot , i went throw a few of these before , hard to get a quality one , now i just use fast switching SSR . and it solved my problem .

                          1 Reply Last reply Reply Quote 0
                          • undefined jumpedwithbothfeet referenced this topic 23 Sept 2022, 14:01
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