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Thermostatic controlled fans not working

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Duet Hardware and wiring
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  • undefined
    fcwilt @p8blr
    last edited by 3 Mar 2025, 16:08

    @p8blr

    Well the extruder fans are there to keep the cold end of the extruder "cold".

    You wouldn't want a fan to "cool" the bed or chamber, so perhaps thermostatic control is simply disabled for bed and chamber heaters.

    The code for the firmware is available if you want to look at it.

    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 3 Mar 2025, 17:34 Reply Quote 0
    • undefined
      Phaedrux Moderator @fcwilt
      last edited by 3 Mar 2025, 17:34

      @fcwilt said in Thermostatic controlled fans not working:

      so perhaps thermostatic control is simply disabled for bed and chamber heaters.

      I don't think so. For instance, it's common to use the bed heater as a proxy to control a case cooling fan, with the assumption being that if the bed heater is on, you're probably running a print and want the Duet to be actively cooled.

      @p8blr Are the fans on a different can board than those heaters? I think this may be the reason.

      Z-Bot CoreXY Build | Thingiverse Profile

      undefined undefined 2 Replies Last reply 3 Mar 2025, 18:07 Reply Quote 0
      • undefined
        fcwilt @Phaedrux
        last edited by 3 Mar 2025, 18:07

        @Phaedrux said in Thermostatic controlled fans not working:

        I don't think so. For instance, it's common to use the bed heater as a proxy to control a case cooling fan, with the assumption being that if the bed heater is on, you're probably running a print and want the Duet to be actively cooled.

        You mean cool the Duet electronics?

        I've just monitored the MCU temperature to decide when to run fans to cool the electronics.

        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 3 Mar 2025, 23:30 Reply Quote 0
        • undefined
          infiniteloop @fcwilt
          last edited by 3 Mar 2025, 23:30

          @fcwilt

          I've just monitored the MCU temperature to decide when to run fans to cool the electronics.

          That’s the proper way to compensate for high ambient temperatures. However, the boards not only suffer from external heat, they can generate a lot of ’steam’ themselves, especially the stepper drivers need to dissipate several hundreds of Watts. Since there is no direct means to monitor these chips, the bed heating may be a suitable indicator of the need for active cooling. Both approaches have their merits, but they use indirect measurements anyway, so the idea of providing some ventilation in general (especially on the back of the Duet) might be good compromise.

          undefined 1 Reply Last reply 4 Mar 2025, 01:36 Reply Quote 0
          • undefined
            fcwilt @infiniteloop
            last edited by 4 Mar 2025, 01:36

            @infiniteloop

            Based on the Duet documentation the chips do have a temperature sensor that can be referenced in code as a temp sensor.

            duet chip sensor.jpg

            I've been doing that and the fans do seem to be working as expected.

            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 4 Mar 2025, 01:47 Reply Quote 0
            • undefined
              infiniteloop @fcwilt
              last edited by 4 Mar 2025, 01:47

              @fcwilt

              the chips do have a temperature sensor that can be referenced in code as a temp sensor.

              Thermostatic control only works with the MCU sensor (that's what you do). The stepper drivers just provide a flag to signal overheating (when it's too late to start a fan).

              undefined 1 Reply Last reply 4 Mar 2025, 01:52 Reply Quote 0
              • undefined
                fcwilt @infiniteloop
                last edited by 4 Mar 2025, 01:52

                @infiniteloop

                True but it is still useful.

                duet chip sensor.jpg

                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 4 Mar 2025, 02:15 Reply Quote 0
                • undefined
                  infiniteloop @fcwilt
                  last edited by 4 Mar 2025, 02:15

                  @fcwilt

                  True but it is still useful.

                  Sure it is, depending on the circumstances - which brings me back to the start of our conversation: under specific conditions, the idea to use a proxy (as per @Phaedrux' post) makes sense. BTW: in my printer, I just engage a static fan for this purpose - poor thing, it is heavily undervolted 😥

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                  • undefined
                    p8blr @Phaedrux
                    last edited by p8blr 3 Apr 2025, 19:02 4 Mar 2025, 19:01

                    @Phaedrux Yes, on different boards. The reason I am trying to do this, is when I heat the chamber, I want to make sure that the electronics on the head are sufficiently cooled, more than just the Duet electronics, I also have a webcam on the head. I may try adding an if statement to the daemon.g to turn this fan on/off depending on the chamber temp if the thermostatic control is not an option.

                    1 Reply Last reply Reply Quote 0
                    • undefined
                      Phaedrux Moderator
                      last edited by 4 Mar 2025, 19:12

                      What firmware version are you using?

                      https://docs.duet3d.com/en/User_manual/RepRapFirmware/CAN_limitations

                      A thermostatically-controlled fan on an expansion board can only be controlled by a temperature sensor on the same expansion board.

                      But that should be resolved in firmware after 3.3

                      Z-Bot CoreXY Build | Thingiverse Profile

                      undefined 1 Reply Last reply 4 Mar 2025, 19:13 Reply Quote 0
                      • undefined
                        p8blr @Phaedrux
                        last edited by 4 Mar 2025, 19:13

                        @Phaedrux 3.5.4

                        1 Reply Last reply Reply Quote 0
                        • undefined
                          Phaedrux Moderator
                          last edited by Phaedrux 3 Apr 2025, 19:17 4 Mar 2025, 19:15

                          Can you test if a fan on the mainboard will work thermostatically with those heaters?

                          You may also want to test with 3.6 RC1 as it is nearing release.

                          https://forum.duet3d.com/topic/37591/firmware-bundle-3-6-0-release-candidate-1-available

                          Z-Bot CoreXY Build | Thingiverse Profile

                          undefined 1 Reply Last reply 4 Mar 2025, 19:17 Reply Quote 0
                          • undefined
                            p8blr @Phaedrux
                            last edited by p8blr 3 Apr 2025, 19:36 4 Mar 2025, 19:17

                            @Phaedrux Not easily, it's in a deployed system. The fact that it only doesn't work (runs all the time regardless of temp) when I assign it to the bed or chamber sensors seems telling though.

                            Edit: I did get it to work with daemon.g with an if statement, but it'd be cool if I didn't have to do that.

                            undefined 1 Reply Last reply 10 Mar 2025, 16:02 Reply Quote 0
                            • undefined Phaedrux marked this topic as a question 4 Mar 2025, 19:26
                            • undefined
                              p8blr @p8blr
                              last edited by 10 Mar 2025, 16:02

                              @dc42 Are you aware of any issues using chamber or bed associated sensors for thermostatically controlled fans in the latest firmware?

                              Thanks

                              undefined 1 Reply Last reply 10 Mar 2025, 16:49 Reply Quote 0
                              • undefined
                                dc42 administrators @p8blr
                                last edited by 10 Mar 2025, 16:49

                                @p8blr I am not aware of any such issues. However, I note that you are trying to control a fan connected to an expansion board using a sensor on the main board. Perhaps that combination doesn't work. Can you do some more tests to find out, e.g. try moving the sensor to an expansion board?

                                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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