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    24V Pump - can I connect direct?

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    Duet Hardware and wiring
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    • benkayundefined
      benkay
      last edited by

      Hi,

      I've seen mixed reports on whether a 24V air pump can be wired directly to a Duet VIN Fan Header, or not.

      The specs ripped from the product description are :

      Rated voltage: 24V
      No load current: 400MA
      Recommended supply : 24V 2A (needs sourcing)

      Some confirmation would be good if I can wire direct, or if I need some sort of relay/power expander.

      Thanks, Ben

      Tevo Little monster with Duet Wifi and Smart Effector / magball arms upgrades.
      Original Prusa i3 Mk3

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      • dc42undefined
        dc42 administrators
        last edited by

        The main issue is likely to be the starting current. Measure the DC resistance of the pump several times, turning the rotor slightly between measurements, and take the lowest measured value. If it's less than 8 ohms than the starting current would exceed 3A, in which case you should connect a suitable thermistor in series with it to reduce the starting surge. Here's an example of a thermistor that may be suitable: http://uk.farnell.com/epcos/b57153s0330m000/thermistor-ntc-33r-1-3a/dp/1688797.

        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

        Hergonowayundefined 1 Reply Last reply Reply Quote 0
        • benkayundefined
          benkay
          last edited by

          OK, I've been recommended a reprap Power expander which I understand opto-isolates the Duet board.

          Presuming resistance is >8 ohms, or I put a thermistor in series, is there then no risk to the duet board? I'd prefer to wire it direct, simply to reduce the wiring mess needed for the power expander.

          Tevo Little monster with Duet Wifi and Smart Effector / magball arms upgrades.
          Original Prusa i3 Mk3

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          • kraegarundefined
            kraegar
            last edited by

            I recommend an opto-isolator based on my own experience and killing a fan port.

            Co-Creator of the RailcoreII CoreXY printer
            https://www.thingiverse.com/thing:2407174

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            • dc42undefined
              dc42 administrators
              last edited by

              The only risk I can see is that if the pump stalls for an extended period of time (e.g. because the pump mechanism seizes up) then the mosfet and the thermistor (f you have one) may overheat - but the motor will probably burn out too.

              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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              • Hergonowayundefined
                Hergonoway @dc42
                last edited by Hergonoway

                @dc42

                Based on your recommendations, is the schematic below the right one for connecting an air pump directly to the Duet ?

                alt text

                Delta goes BrrrRRRRrrrrrRRRRrrr

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                • dc42undefined
                  dc42 administrators
                  last edited by dc42

                  Yes it is. The flyback diode is optional if the Duet is revision 1.02 or later, but having one close to the motor will help to reduce any interference generated when you PWM the motor.

                  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

                  1 Reply Last reply Reply Quote 1
                  • SM3Dundefined
                    SM3D
                    last edited by SM3D

                    @dc42 and @benkay just wanted check with both of you my wiring before connecting to my duet 1.01. I followed the post and wired the pump accordingly. Here are the pictures:

                    0_1527328363356_20180526_113737.jpg

                    0_1527328376989_20180526_113747.jpg

                    Please let me know whether it is correct or not. I surely do not want to blow my Duet.

                    Cheers,
                    Vasan

                    Good judgement comes from experience but experience comes from bad judgements

                    Hergonowayundefined 1 Reply Last reply Reply Quote 0
                    • Hergonowayundefined
                      Hergonoway @SM3D
                      last edited by Hergonoway

                      @sm3d seems correctly set

                      Delta goes BrrrRRRRrrrrrRRRRrrr

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                      • SM3Dundefined
                        SM3D
                        last edited by

                        Thanks @Hergonoway will update whether berd air is effective or not

                        Cheers,
                        Vasan

                        Good judgement comes from experience but experience comes from bad judgements

                        Hergonowayundefined 1 Reply Last reply Reply Quote 0
                        • benkayundefined
                          benkay
                          last edited by

                          Looks correct to me...although I understand that the later boards have the diode in-built so not strictly necessary to add one there.

                          Tevo Little monster with Duet Wifi and Smart Effector / magball arms upgrades.
                          Original Prusa i3 Mk3

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                          • Hergonowayundefined
                            Hergonoway @SM3D
                            last edited by

                            @sm3d In my case, putting the thermistor didn't closed the circuit as it should, so for now and until @dc42 finish his tests regarding what should be used I don't use the thermistor. For info I'm running the air pump MAX in 24v sold by makerhive.

                            Delta goes BrrrRRRRrrrrrRRRRrrr

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                            • SM3Dundefined
                              SM3D
                              last edited by

                              @Hergonoway I have trouble running the pump with thermistor from PWM controlled fan ports but I could run them with always on fan ports. Here is my post about it:

                              https://forum.duet3d.com/topic/5449/not-able-to-pwm-for-berd-air-pump/10

                              I even shorted the legs of thermistor and tried from PWM fan ports but no luck. If you have any ideas please post it.

                              Cheers,
                              Vasan

                              Good judgement comes from experience but experience comes from bad judgements

                              1 Reply Last reply Reply Quote 0
                              • BenDieselundefined
                                BenDiesel
                                last edited by

                                So I have a 24v berdair hooked directly up. I usually run at 25 to 30% and have the Pam set to 255khz.
                                The motor get rather warm. Almost to hot to tuch. Should I be concerned?

                                1 Reply Last reply Reply Quote 1
                                • Hergonowayundefined
                                  Hergonoway
                                  last edited by Hergonoway

                                  255K is way to high try 25K (F25000). In my case the sound and the temp dropped a lot.

                                  Note that I've directly connected the 1/8" ID Tygon tube to the metal tube, it reduce pressured area and reduce heat from the pump mechanism (the white plastic part)

                                  Delta goes BrrrRRRRrrrrrRRRRrrr

                                  1 Reply Last reply Reply Quote 1
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