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    Connecting and Operating a Servo Motor

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    • bastiundefined
      basti
      last edited by

      Hi Duet Users,

      I want to connect and operate a servo motor (MG945 Digital Servo, operating voltage: 4.8-7.2V) with my Duet Wifi; however it doesn't work...

      Application
      A servo motor should be implemented to grip (and then lift via z-stage) a dish; hence the application requires gripping (for example: 120 to 60 degrees) for 10 sec and then an opening motion (60 to 120 degrees).

      Setup
      Duet Wifi + Duex5 (12V, 29A), 7 stepper motors with 7 limit switches, 4 fans, 2 bed heater, 1 servo motor

      Wiring
      The servor motor has three wires/pinouts (PWM, VCC, GND). According to the documentation "Using servos and controlling unused IO pins", I can use heater pins to connect the servo motor. Since the heater connection has two pins, I was wondering how to connect the servo motor to the DuetWifi. Do you have any example for the wiring of a servo motor? Is the motor connected to ext 5V (with +5V and GND) and the PWM to the heater pin?

      Operating
      Using the heater pins, I disabled the heater via M307 H# A-1 C-1 D-1 in the config file. Currently, I am a bit confused if E0 is H0? Moreover, do I have to use the M42 command when using M280 servo control command? It would be great to see an example protocol for operating a servo motor.

      Thanks a lot for your feedback and support!

      Regards,
      Sebastian

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      • fmaundefined
        fma
        last edited by

        I myself use a servo for my filament mux. Here is my config (I use a Duet fan output, with fan power supply set to 5V; my real fans are all on the Duex5):

        M106 P0 I-1               ; disable Fan 0 (used as servo output)
        M280 P20 S2400 I1         ; select mux 1
        

        For electrical connection, you need to power up your servo from a dedicated power supply (so you can adjust the voltage, and have enough current): wire the + of this supply to the + of your servo, and connect all - together (main Duet supply, servo power supply and servo itself). Then, wire the fan pwm output to the servo pwm input.

        The servo power supply can be a buck converter connected to the Duet power supply. Don't use duet 5V, you may fry it, because a servo can drain a lot of current.

        Frédéric

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        • dc42undefined
          dc42 administrators
          last edited by

          The DueX5 has 5 three-pin connectors for 5V servos, one for each heater channel. Pick one of those for which you are not using the corresponding heater.

          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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          • fmaundefined
            fma
            last edited by

            I missed that! Thanks!

            Frédéric

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