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    Pressured air cooling controlled with servo and ball valve

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    • MaxGyverundefined
      MaxGyver @MikeDC
      last edited by

      @mikedc

      Hey, thank you very much for sharing this. I will give it a try!

      -Max

      1 Reply Last reply Reply Quote 1
      • o_lampeundefined
        o_lampe @MikeDC
        last edited by o_lampe

        @mikedc
        Isn't it better to 'scale' the incoming PWM value to the required servo-angle?
        You need to know: min_in, max_in, min_out, max_out.

        [**pseudo** code]
        var scale_factor = {(max_out - min_out) / (max_in - min_in)}
        var servo_out = {scale_factor * (fans[0].actualValue - min_in) + min_out}
        

        There's a standard formula to scale variables, but I couldn't write it down from memory.. Have to google it..
        //edit This should work, just have to put it in clean gcode-meta

        MikeDCundefined 1 Reply Last reply Reply Quote 1
        • MikeDCundefined
          MikeDC @o_lampe
          last edited by

          @o_lampe maybe yes, but when i was trying this it was the only way i could get it working

          1 Reply Last reply Reply Quote 0
          • MaxGyverundefined
            MaxGyver
            last edited by MaxGyver

            @o_lampe

            So just to recap, these are my values:

            • min_in = 0 (M106 S0 ->Fan off)
            • max_in = 255 (M106 S255 -> Fan full on)
            • min_out = 0 (M280 P0 S0 -> Servo at 0° -> valve closed)
            • max_out =90 (M280 P0 S90 -> Servo at 90° -> valve fully open)

            So my code should look like this ?

            [**pseudo** code]
            var scale_factor = {(90 - 0) / (255 - 0)}
            var servo_out = {scale_factor * (fans[0].actualValue - 0) + 90}
            
            M280 P0 S{var.servo_out}
            

            I have not used G-Code meta commands before, so I would need a little help here to put this in clean meta code and make this work.

            -Max

            o_lampeundefined OwenDundefined 3 Replies Last reply Reply Quote 0
            • o_lampeundefined
              o_lampe @MaxGyver
              last edited by o_lampe

              @maxgyver
              I haven't written anything in Meta-code yet, but I read a little.
              E.g. the waved brackets {} are mandatory for the outmost math-expressions.
              If you want to test it, you can replace M280...with a harmless echo P"var.servo_out"

              I believe, there is a way to call daemon.g more often to get a faster response, maybe the experts can chime in here?

              For later editing it could be useful to put the min/max values in variables too, otherwise you can cut a few corners, where a value is zero.

              1 Reply Last reply Reply Quote 0
              • OwenDundefined
                OwenD @MaxGyver
                last edited by OwenD

                @maxgyver

                @maxgyver
                You would probably be better off declaring global variables in config.g then updating the value in your macro ( or daemon.g)
                If you're running in daemon.g it just seems counter productive to be declaring and freeing variables constantly.

                Config.g

                ; create variables - must be after servo is created 
                global scale_factor = {(90 - 0) / (1 - 0)} ; no need for the math in this instance but it makes it clear how you arrive at the value.
                global servo_out = 0 ; set to zero initially 
                 M280 P0 S{global.servo_out} ; start with valve closed
                

                Daemon.g

                set global.servo_out = {global.scale_factor * (fans[0].actualValue - 0) + 0} ; calculate position required 
                M280 P0 S{global.servo_out} ; adjust valve position. 
                

                You could optionally use an IF statement to only adjust when required, which I suppose would reduce the traffic and cpu time by a tiny amount.

                1 Reply Last reply Reply Quote 0
                • OwenDundefined
                  OwenD @MaxGyver
                  last edited by OwenD

                  @maxgyver said in Pressured air cooling controlled with servo and ball valve:

                  @o_lampe

                  So just to recap, these are my values:

                  • min_in = 0 (M106 S0 ->Fan off)
                  • max_in = 255 (M106 S255 -> Fan full on)
                  • min_out = 0 (M280 P0 S0 -> Servo at 0° -> valve closed)
                  • max_out =90 (M280 P0 S90 -> Servo at 90° -> valve fully open)

                  Actually , thinking about this, the value you get back from fans[0].actualValue will be in the range 0-1, not 0-255
                  You will need to change your code accordingly.

                  1 Reply Last reply Reply Quote 0
                  • OwenDundefined
                    OwenD
                    last edited by

                    It's a rainy day here, so for something to do I decided to fully test this.
                    Using a YM2763 13kg/cm hobby servo (externally powered so as to not risk damaging the duet).
                    This has an input range of 0-180 which corresponds to the angle.

                    Please refer to the notes for M280 as other servos may require different values

                    It's not really necessary to create variables for all settings, but it makes adjustment and readability easier.

                    in config.g

                    ;Valve Control
                    ; Set up scaling variables {(output_end - output_start) / (input_end - input_start)}
                    M950 S1 C"exp.heater4"  ; assign GPIO port 1 to heater4 on expansion connector, servo mode
                    global InputStart = 0 
                    global InputEnd = 1
                    global OutputStart = 0
                    global OutputEnd = 90
                    global ScaleFactor = (global.OutputEnd - global.OutputStart) / (global.InputEnd - global.InputStart) ; no need for the math in this instance but it makes it clear how you arrive at the value.
                    global ServoOut = floor(global.ScaleFactor * (fans[0].actualValue - global.InputStart) + 0.5) + global.OutputStart ; calculate position required on sevo - use floor() to apply rounding
                    M280 P1 S{global.servo_out} ; adjust valve position to reflect fan speed.
                    

                    in daemon.g or macro

                    set global.ServoOut = floor((global.ScaleFactor * (fans[0].actualValue - global.InputStart)) + 0.5) + global.OutputStart ; calculate position required - use floor() to apply rounding to nearest whole number
                    ;echo {global.ServoOut}
                    M280 P1 S{global.ServoOut} ; adjust valve attached to servo on P1 to reflect scaled fan speed. 
                    
                    o_lampeundefined MaxGyverundefined 2 Replies Last reply Reply Quote 2
                    • o_lampeundefined
                      o_lampe @OwenD
                      last edited by

                      @owend
                      Thank you for chiming in!
                      Can you confirm that in math formulas no waved brackets are necessary, but when I call eg. M280 the parameter has to be wrapped in {}?
                      How do I know, I have enough free memory to write longer meta-code? (AI for TicTacToe can get quite voluminous)

                      OwenDundefined 1 Reply Last reply Reply Quote 0
                      • OwenDundefined
                        OwenD @o_lampe
                        last edited by

                        @o_lampe said in Pressured air cooling controlled with servo and ball valve:

                        @owend
                        Thank you for chiming in!
                        Can you confirm that in math formulas no waved brackets are necessary, but when I call eg. M280 the parameter has to be wrapped in {}?

                        Correct on both counts

                        How do I know, I have enough free memory to write longer meta-code? (AI for TicTacToe can get quite voluminous)

                        You can use M122 to see how much of the heap is used.
                        See here

                        o_lampeundefined 1 Reply Last reply Reply Quote 0
                        • o_lampeundefined
                          o_lampe @OwenD
                          last edited by

                          @owend
                          I just found this thread, please see my reply there

                          1 Reply Last reply Reply Quote 0
                          • o_lampeundefined
                            o_lampe
                            last edited by o_lampe

                            @OwenD and @MaxGyver
                            Thinking further and having pity with the servo, it would be better to add a 'hysteresis' in the code, such as

                            [pseudo code]
                            If (abs(new_fan_value - old_fan_value) > hysteresis)
                               go on
                            else
                              break
                            
                            

                            That's not necessarily a problem with fan-values changing in big numbers, but a Servo also has a'deadband' which you have to keep in mind. (and for further reference, if someone wants to reuse the code for something else)

                            1 Reply Last reply Reply Quote 0
                            • MaxGyverundefined
                              MaxGyver @OwenD
                              last edited by

                              @owend

                              I am getting the following error after inserting your code in my config.g

                              "Error: Failed to read code from macro config.g: Failed to parse major G-code number (lobal) in line 85"

                              To me, it looks like the global variable are not recognized by the firmware:

                              I am using firmware version 3.3-b2.

                              screen.PNG

                              1 Reply Last reply Reply Quote 0
                              • o_lampeundefined
                                o_lampe
                                last edited by

                                You have written servoout and also servo_out.

                                MaxGyverundefined OwenDundefined 2 Replies Last reply Reply Quote 0
                                • MaxGyverundefined
                                  MaxGyver @o_lampe
                                  last edited by

                                  @o_lampe said in Pressured air cooling controlled with servo and ball valve:

                                  You have written servoout and also servo_out.

                                  Nope, this did not cause the error... 😕

                                  "Error: Failed to read code from macro config.g: Failed to parse major G-code number (lobal) in line 4"

                                  ;Valve Control
                                  ; Set up scaling variables {(output_end - output_start) / (input_end - input_start)}
                                  M950 S1 C"io4.out"  ; assign GPIO port 1 to heater4 on expansion connector, servo mode
                                  global InputStart = 0 
                                  global InputEnd = 1
                                  global OutputStart = 0
                                  global OutputEnd = 90
                                  global ScaleFactor = (global.OutputEnd - global.OutputStart) / (global.InputEnd - global.InputStart) ; no need for the math in this instance but it makes it clear how you arrive at the value.
                                  global ServoOut = floor(global.ScaleFactor * (fans[0].actualValue - global.InputStart) + 0.5) + global.OutputStart ; calculate position required on sevo - use floor() to apply rounding
                                  M280 P1 S{global.ServoOut} ; adjust valve position to reflect fan speed.
                                  
                                  OwenDundefined o_lampeundefined 2 Replies Last reply Reply Quote 0
                                  • OwenDundefined
                                    OwenD @MaxGyver
                                    last edited by

                                    @maxgyver
                                    @maxgyver
                                    I'm assuming you are running the correct versions on DWC, etc etc
                                    We are both running RRF3.3b2 and it works for me.
                                    I'm on a Duet 2 wifi.
                                    I don't have a duet 3, but I suspect it's actually coming from your M950 command on the previous line.
                                    Either that are it's one of this SBC specific issues.

                                    What happens when you run those commands individually from the console command line?

                                    MaxGyverundefined 1 Reply Last reply Reply Quote 0
                                    • OwenDundefined
                                      OwenD @o_lampe
                                      last edited by

                                      @o_lampe
                                      That was actually my error in the original.

                                      1 Reply Last reply Reply Quote 0
                                      • o_lampeundefined
                                        o_lampe @MaxGyver
                                        last edited by

                                        @maxgyver said in Pressured air cooling controlled with servo and ball valve:

                                        G-code number (lobal)

                                        Your parser believes global is the beginning of a move command and it can't parse "lobal" as number (0,1,2,3,4 expected)
                                        I'm with @OwenD it might be related to SBC issues.

                                        1 Reply Last reply Reply Quote 0
                                        • MaxGyverundefined
                                          MaxGyver @OwenD
                                          last edited by

                                          @owend said in Pressured air cooling controlled with servo and ball valve:

                                          (...)I suspect it's actually coming from your M950 command on the previous line.
                                          Either that are it's one of this SBC specific issues.

                                          It's not the M950 command (I have checked by commenting out this line)

                                          @owend said in Pressured air cooling controlled with servo and ball valve:

                                          What happens when you run those commands individually from the console command line?

                                          I get the same error message.

                                          -Max

                                          MaxGyverundefined 1 Reply Last reply Reply Quote 0
                                          • MaxGyverundefined
                                            MaxGyver @MaxGyver
                                            last edited by

                                            @maxgyver

                                            After upgrading to Beta3.3 the error message has changed to the following:

                                            Error.PNG

                                            the code in config.g:

                                            ;Valve Control
                                            ; Set up scaling variables {(output_end - output_start) / (input_end - input_start)}
                                            M950 S1 C"io4.out"  ; assign GPIO port 1 to heater4 on expansion connector, servo mode
                                            global InputStart = 0 
                                            global InputEnd = 1
                                            global OutputStart = 0
                                            global OutputEnd = 90
                                            global ScaleFactor = (global.OutputEnd - global.OutputStart) / (global.InputEnd - global.InputStart) ; no need for the math in this instance but it makes it clear how you arrive at the value.
                                            global ServoOut = floor(global.ScaleFactor * (fans[0].actualValue - global.InputStart) + 0.5) + global.OutputStart ; calculate position required on sevo - use floor() to apply rounding
                                            M280 P1 S{global.ServoOut} ; adjust valve position to reflect fan speed.
                                            

                                            and deamon.g

                                            set global.ServoOut = floor((global.ScaleFactor * (fans[0].actualValue - global.InputStart)) + 0.5) + global.OutputStart ; calculate position required - use floor() to apply rounding to nearest whole number
                                            ;echo {global.ServoOut}
                                            M280 P1 S{global.ServoOut} ; adjust valve attached to servo on P1 to reflect scaled fan speed. 
                                            

                                            -Max

                                            OwenDundefined 1 Reply Last reply Reply Quote 0
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