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    Unsolved Using stepper currrent to detect a tool is loaded

    Using Duet Controllers
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    • GeneRisi
      GeneRisi last edited by

      Is there any way to ask the stepper controller on the Duet2 how much current was last used to move the stepper? I am wondering whether I can use it as a way to compare free rotation (no tool loaded on the e3d tool changer) vs rotation with friction (tool loaded)?
      Thanks!

      zapta 1 Reply Last reply Reply Quote 0
      • zapta
        zapta @GeneRisi last edited by

        @generisi, I believe that the current is the same regardless of the mechanical load.

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

          @zapta said in Using stepper currrent to detect a tool is loaded:

          @generisi, I believe that the current is the same regardless of the mechanical load.

          Correct, the drivers are constant current. However, the drivers do contain a means to measure load. The M122 report includes the load measurement, it's the SG values in the driver reports. The SG values get reset each time M122 is run.

          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

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

            @dc42 Are the SG values available in the object model ( if that's the right terminology )? I am running RRF 3.3b3 right now.

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

              @generisi said in Using stepper currrent to detect a tool is loaded:

              @dc42 Are the SG values available in the object model ( if that's the right terminology )? I am running RRF 3.3b3 right now.

              No they are not.

              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

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

                @dc42 CNC user here. Is it possible to add. I'm using two free drivers for a motorised vise. Would be super to have a mean of applying same force on each part I'm machining.

                dc42 fma 2 Replies Last reply Reply Quote 0
                • dc42
                  dc42 administrators @rzi last edited by dc42

                  @rzi I suggest you check whether the stallGuard values (as reported by M122) are useful first. I doubt that the instantaneous values would be useful. The values reported by M122 are the min and max values since M122 was last run. If we did add them to the OM then we would need to decide what period of time to sample them over, and whether to report an average or the min/max values over that period.

                  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

                  GeneRisi 1 Reply Last reply Reply Quote 1
                  • fma
                    fma @rzi last edited by

                    @rzi said in Using stepper currrent to detect a tool is loaded:

                    @dc42 CNC user here. Is it possible to add. I'm using two free drivers for a motorised vise. Would be super to have a mean of applying same force on each part I'm machining.

                    You could set the current of the vise motor to set the wanted force (torque). Then, just turn the motor until it stalls (using stallGuard feature, through a homing procedure, for example), and you should get roughly the same force each time.

                    Frédéric

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

                      @dc42 In my case the SG values are useful (for the E3D tool changer coupler stepper). If I had a gcode command that would clear any min and max values in the object model and begin sampling and another gcode command would set the min and max values in the object model, then I could do whatever I want to measure between the two gcode commands. This behavior is almost identical to the M122 behavior. It might also be useful to include a "start sampling" time stamp and an "end sampling" time stamp.

                      What do you think ?

                      1 Reply Last reply Reply Quote 0
                      • rzi
                        rzi @fma last edited by

                        @fma said in Using stepper currrent to detect a tool is loaded:

                        @rzi said in Using stepper currrent to detect a tool is loaded:

                        @dc42 CNC user here. Is it possible to add. I'm using two free drivers for a motorised vise. Would be super to have a mean of applying same force on each part I'm machining.

                        You could set the current of the vise motor to set the wanted force (torque). Then, just turn the motor until it stalls (using stallGuard feature, through a homing procedure, for example), and you should get roughly the same force each time.

                        Ah yes, going to test that. A much more straight forward approach. Thanx

                        1 Reply Last reply Reply Quote 0
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