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    Mixed voltage for 24V fans on toolboard.

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    • dintidundefined
      dintid @A Former User
      last edited by

      @bearer I'm not at all component savvy, so that's a no go for me.
      If you replace "diode", "inductive loads" and "cathode" with "blah blah blah" you'd get an idea of what I just understood from what you just said 🙂
      Thanks though for the suggestion.

      RepRapFirmware supported G-codes: https://duet3d.com/wiki/G-code

      A Former User? 1 Reply Last reply Reply Quote 0
      • A Former User?
        A Former User @dintid
        last edited by A Former User

        @dintid fair enough, I was open to that possibility - but also figure the information is here for the next guy as well.

        Diode is (usually) a small black chip with 2 terminals. Electronic check valve essentially. They're just behind the screw terminals and labeled D1 and D2 on the PCB.

        Inductive loads is in simpler terms "anything" that isn't a heater, brushless fan or LED. A pump or brushed fan being the prime example of what not to connect if the diode is simply removed; making the modification means this is not a concern.

        Cathode is the one of the two terminals on the Diode and is usually marked with a line on the body, and Duet people have also put a K on the PCB to show which way to mount it. (The other terminal is the Anode ref wikipedia)

        As only the schematic has been released so far (there is another thread for those who want to discuss that) and not he KiCad sources or gerber files I can't easily make a diagram, but from the picture it looks like simply cutting a trace will not suffice, soldering is needed, Custom wiring to get Vin to the fan, simplest looks to be to wire it along with the heater to Vin on Out0. 👇

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        • dc42undefined
          dc42 administrators
          last edited by dc42

          Here's the PCB for that part of the board (this is for the v1.0 board, but the v0.6 board is similar):

          7025aaba-3406-40b6-b02a-41ee6d8f2a97-image.png

          It looks to me that you can cut the trace on back copper (green in this image) that feeds 12V to the 12V pin on OUT1, and jumper that pin to VIN instead. The diode is rated at 40V so it will be OK with 24V. The mosfet is rated at 60V.

          PS - that +12V trace comes via OUT2, so if you want to convert both outputs to VIN, cut the back copper trace that feeds 12V to the centre pin of OUT2 instead.

          66e00597-acd8-4a11-9c96-7b0f3228a695-image.png

          Duet WiFi hardware designer and firmware engineer
          Please do not ask me for Duet support via PM or email, use the forum
          http://www.escher3d.com, https://miscsolutions.wordpress.com

          dintidundefined 1 Reply Last reply Reply Quote 0
          • dintidundefined
            dintid @dc42
            last edited by

            @dc42 if the pcb is multilayered id be afraid to cut too deeply.
            Maybe a physical jumper solution could be implemented in future versions.
            Main concern for me is the BLTouch not working for me. Hopefully I’ll have time to test it on main board tomorrow.

            RepRapFirmware supported G-codes: https://duet3d.com/wiki/G-code

            A Former User? 1 Reply Last reply Reply Quote 0
            • A Former User?
              A Former User @dintid
              last edited by

              @dintid said in Mixed voltage for 24V fans on toolboard.:

              if the pcb is multilayered id be afraid to cut too deeply.

              it is, but not a problem to cut just the bottom layer - in adittion there is plenty of space to cut the trace where there aren't any mid layer signals.

              if you were to try it, which output would you use with 24v? out1, out 2 or both?

              dintidundefined 1 Reply Last reply Reply Quote 0
              • dintidundefined
                dintid @A Former User
                last edited by

                @bearer I’m not going to cut anything, as it would introduce a new variable on my board, but if I were, I’d cut both.

                RepRapFirmware supported G-codes: https://duet3d.com/wiki/G-code

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                • baird1faundefined
                  baird1fa
                  last edited by

                  @dc42 hypothetically if you are not using the 12v for anything, what damage would be caused by feeding Vin to the 12v through the fly back diode?

                  dc42undefined 1 Reply Last reply Reply Quote 0
                  • dc42undefined
                    dc42 administrators @baird1fa
                    last edited by dc42

                    @baird1fa said in Mixed voltage for 24V fans on toolboard.:

                    @dc42 hypothetically if you are not using the 12v for anything, what damage would be caused by feeding Vin to the 12v through the fly back diode?

                    That's a good point! The 5V regulator is fed from +12V, however there is a protection diode between the external 12V output and the internal one. So it should be safe to connect the external 12V output to VIN. There is a 1uF capacitor C26 connected to the external 12V rail which we have specified as 16V, however the capacitor we actually use is rated at 50V. I've made a note to increase it to 50V officially.

                    Duet WiFi hardware designer and firmware engineer
                    Please do not ask me for Duet support via PM or email, use the forum
                    http://www.escher3d.com, https://miscsolutions.wordpress.com

                    baird1faundefined 1 Reply Last reply Reply Quote 0
                    • baird1faundefined
                      baird1fa @dc42
                      last edited by

                      @dc42 I’m not sure I follow all of that. So if 24V was applied to Vin and Vin was used to power a fan as the + terminal and the - was connected to the out1 PWM terminal. You would feed 24V into the 12V supply through the fly back diode. But this would only affect out1 and out2 and not the 5V supply because there is protection internally to the 5V supply?

                      So in conclusion it would only harm the 12V output terminals if anything at all?

                      dc42undefined 1 Reply Last reply Reply Quote 0
                      • dc42undefined
                        dc42 administrators @baird1fa
                        last edited by

                        @baird1fa said in Mixed voltage for 24V fans on toolboard.:

                        @dc42 I’m not sure I follow all of that. So if 24V was applied to Vin and Vin was used to power a fan as the + terminal and the - was connected to the out1 PWM terminal. You would feed 24V into the 12V supply through the fly back diode. But this would only affect out1 and out2 and not the 5V supply because there is protection internally to the 5V supply?

                        So in conclusion it would only harm the 12V output terminals if anything at all?

                        Correct. You could even connect +12V at the OUT1 or OUT2 connector to VIN. Note, I haven't tested this yet, I'll try to do this tomorrow.

                        Duet WiFi hardware designer and firmware engineer
                        Please do not ask me for Duet support via PM or email, use the forum
                        http://www.escher3d.com, https://miscsolutions.wordpress.com

                        becky9undefined ollissundefined 2 Replies Last reply Reply Quote 0
                        • becky9undefined
                          becky9 @dc42
                          last edited by

                          @dc42 Did you test this David? Is it safe to do? x

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                          • ollissundefined
                            olliss @dc42
                            last edited by

                            @dc42 Have you ever tested this? it would be nice to know if this works without problems or is it just better to disconnect the 12v trace.

                            dc42undefined 1 Reply Last reply Reply Quote 0
                            • dc42undefined
                              dc42 administrators @olliss
                              last edited by

                              @olliss it's safe to do. The next revision of the tool board will have a jumper to do exactly this.

                              Duet WiFi hardware designer and firmware engineer
                              Please do not ask me for Duet support via PM or email, use the forum
                              http://www.escher3d.com, https://miscsolutions.wordpress.com

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