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    PWM Convertion

    Duet Hardware and wiring
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    • DDD
      DDD last edited by

      How can I convert Duet's ground-switched PWM signal to a VIN-switched PWM?
      I'm trying to control a PLC via a PWM converter, but when the PWM out from the Duet is connected to the converter nothing happens because expects a VIN-switched PWM signal.

      I connect a PWM signal generated via Arduino and it works.

      T3P3Tony 1 Reply Last reply Reply Quote 0
      • T3P3Tony
        T3P3Tony administrators @DDD last edited by

        @DDD how much current does the PLC input take and at what voltage?

        www.duet3d.com

        DDD 1 Reply Last reply Reply Quote 0
        • DDD
          DDD @T3P3Tony last edited by

          @T3P3Tony the PLC works form 0 - 10 V. The converter translate pwm duty cycle into voltage with 4 A max, more than enough for the low current input for the PLC

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

            The PWM to 0-10V converters I have seen have optically isolated inputs, so they don't mind whether the input is ground referenced or not. Can you send a link to the data for the one you have?

            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

            DDD 2 Replies Last reply Reply Quote 0
            • DDD
              DDD @dc42 last edited by

              @dc42 for this input ground is grounded and if the optocopler is isolated the converter doesn't go bellow 1V

              https://www.icstation.com/mobile/voltage-converter-module-adjustable-converter-power-module-digital-analog-signal-p-12498.html

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              • DDD
                DDD @dc42 last edited by DDD

                @dc42 could a pull-up resistor work?

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                • dc42
                  dc42 administrators last edited by

                  It looks to me that the PWM converter you linked to does have an optically isolated input, although the input terminals are confusingly labelled PWM and GND. I suggest you check using a multimeter whether there is any continuity between that GND terminal and the other two. If there is none, then treat that terminal as PWM- in and connect it to your chosen FAN- output. Treat the terminal labelled PWM as PWM+ and connect it to the corresponding positive pin of the fan output. Make sure you have the jumper on that converter in the 12V position not the 5V position.

                  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

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

                    @dc42 The input is not PWM- it's grounded with the rest of the circuit. I added a 10 Kohm pull-up resistor and was able to drive the converter, altho, doesn't go under 1V.

                    The same setup but with a PWM generated with an Arduino, the converter goes under 1V without a problem.

                    After measuring Duet's PWM signal by an Arduino, the duty cycle doesn't go under 10%. I don't have an oscilloscope.

                    How can I make the Duet output a PWM duty cycle under 10%?

                    Duet 6HC 3.1.1
                    M950 F2 C"0.out4" Q1000

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                    • dc42
                      dc42 administrators last edited by dc42

                      You are controlling the laser as if it is a fan (which is not the best way to do it). The M106 L parameter sets the minimum allowed PWM.

                      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 0
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