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    Not able to PWM for berd air pump

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    • dc42undefined
      dc42 administrators
      last edited by

      When you connected the pump to the always-on fan connector and it ran, were the flyback diode and thermistor still in the circuit? If so then they can't be causing the problem.

      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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      • SM3Dundefined
        SM3D
        last edited by

        @dc42 I had fly back diode and thermistor connected all the time. The pump does not run at all when I connect to Pwm fan ports but ran fine with always on fan port. I am not sure what is the problem with Pwm control of this pump. Any suggestions would be helpful.

        Cheers,
        Vasan

        Good judgement comes from experience but experience comes from bad judgements

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        • dc42undefined
          dc42 administrators @SM3D
          last edited by

          @sm3d said in Not able to PWM for berd air pump:

          @dc42 I had fly back diode and thermistor connected all the time. The pump does not run at all when I connect to Pwm fan ports but ran fine with always on fan port. I am not sure what is the problem with Pwm control of this pump. Any suggestions would be helpful.

          Cheers,
          Vasan

          Does it work when you specify full PWM, i.e. S1 or S255 in the M106 command?

          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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          • SM3Dundefined
            SM3D
            last edited by

            @dc42 I was travelling and could not reply you faster. Here is the configuration for fan

            M106 P0 S255 I0 F25000 H-1

            I tried both S1.0 and S255 but nothing happened with PWM fans. As I mentioned, the pump works fine with always on fan ports.

            What is the difference between S factor mentioned in M106 and slider used in Duet web control? Do they perform the same function.

            While I am typing this my config.g got deleted automatically and I see config.g.bak. Any idea how to recover my config.g file

            Good judgement comes from experience but experience comes from bad judgements

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            • SM3Dundefined
              SM3D
              last edited by

              Took the SD card out, renamed the config.g.bak to config.g, the duet is back online but still I have this problem with the pump

              Cheers,
              Vasan

              Good judgement comes from experience but experience comes from bad judgements

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              • dc42undefined
                dc42 administrators @SM3D
                last edited by

                @sm3d said in Not able to PWM for berd air pump:

                @dc42 I was travelling and could not reply you faster. Here is the configuration for fan

                M106 P0 S255 I0 F25000 H-1

                I tried both S1.0 and S255 but nothing happened with PWM fans. As I mentioned, the pump works fine with always on fan ports.

                What is the difference between S factor mentioned in M106 and slider used in Duet web control? Do they perform the same function.

                While I am typing this my config.g got deleted automatically and I see config.g.bak. Any idea how to recover my config.g file

                Does it work if you short out the thermistor? I don't recommend running it like that for long, but I recall that someone else found that the thermistor stopped the motor from starting - indicating that a physically smaller thermistor is needed.

                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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                • SM3Dundefined
                  SM3D
                  last edited by

                  @dc42 I connected the positive from the pump directly without the resistor. I also tried by touching both the legs of transistor together effectively shorting them(hope I am correct) still no luck.

                  Good judgement comes from experience but experience comes from bad judgements

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                  • dc42undefined
                    dc42 administrators @SM3D
                    last edited by

                    @sm3d said in Not able to PWM for berd air pump:

                    @dc42 I connected the positive from the pump directly without the resistor. I also tried by touching both the legs of transistor together effectively shorting them(hope I am correct) still no luck.

                    That's odd, because with the FET shorted its Fan connector is in parallel with the always-on connectors, and you said that the pump works on those (even with the thermistor).

                    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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                    • SM3Dundefined
                      SM3D
                      last edited by

                      Yes I agree with you that its odd. I don't know what to do. Thanks @dc42 for your suggestions so far.

                      Cheers,
                      Vasan

                      Good judgement comes from experience but experience comes from bad judgements

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                      • dc42undefined
                        dc42 administrators
                        last edited by

                        You could use a multimeter to check for low resistance between the VFAN pins of the always-on and controlled fan connectors. Also to check for low resistance between the mosfet source pin and the ground pin of the always-on fan connector.

                        Then connect the pump/thermistor combo to a controlled fan output, set that fan to full PWM and not thermostatic control, switch your multimeter to Volts and measure between the VIN ground terminal and each of:

                        • FAN- output on the controlled fan connector
                        • VFAN output on the controlled fan connector
                        • Mosfet source pin

                        Take great care when measuring these voltages! Many users have shorted the fan output pins together when trying to take similar measurements, resulting in a blown mosfet. So plan how you are going to do it with no risk of shorting anything, and do a dummy run with power off first.

                        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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                        • SM3Dundefined
                          SM3D
                          last edited by SM3D

                          Hi David @dc42 ,
                          Thanks for your help and suggestions! My knowledge in electrical engineering is very limited so pardon my silly questions. I use duet v1.01, may I know where is the MOSFET source pin? I am trying to write the procedure in steps based on my understanding.

                          Step 1:

                          Check the resistance between V_FAN pin of FAN_0 and V_FAN pin of Always on Fan

                          Step 2:

                          Check the resistance between MOSFET source pin and ground pin of Always on Fan - Where is the MOSFET source pin in Duet wiring diagram

                          For Step 1 and 2 what are the typical resistance values?

                          Step3:

                          Connect the pump with thermistor to one of the PWM control fan pins then measure the voltage between:

                          (i) Negative pin of the PWM fan connector and VIN Ground terminal (-ve pin of the power input)

                          (ii) Positive pin of the PWM fan connector and VIN Ground terminal (-ve pin of the power input)

                          (iii) Mosfet source pin and VIN Ground terminal (-ve pin of the power input)

                          In the duet wiring diagram, if you can indicate where is the MOSFET source pin, it will be helpful.

                          If it involves a high probability of blowing up a MOSFET, I rather prefer not to do it because I do not have the skills to solder them back.

                          Thanks again for your help!

                          Cheers,
                          Vasan

                          Good judgement comes from experience but experience comes from bad judgements

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                          • Hergonowayundefined
                            Hergonoway
                            last edited by

                            Same issue there, thermistor doesn't close the circuit.

                            I've removed it for the moment, hope not for too long 🙂

                            @dc42 mentionned in a another post that it may be due to the motor not drawing enough current to heat up the thermistor (Posting this to merge backlog discussion in this dedicated topic)

                            Delta goes BrrrRRRRrrrrrRRRRrrr

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                            • SM3Dundefined
                              SM3D
                              last edited by

                              @dc42 @Hergonoway The problem is solved. I reduced the frequency F parameter to 10 to see what happens and voila, PWM worked. Then I raised it to 100, still worked. I am yet to check higher frequencies (will do in the evening).

                              Previously, I used F25000, F500 and F100 but it did not work. Now out of the blue it works. I haven't changed anything in my setup.

                              Cheers,
                              Vasan

                              Good judgement comes from experience but experience comes from bad judgements

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