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    BLTouch working

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    Duet Hardware and wiring
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    • W3DRKundefined
      W3DRK
      last edited by

      I finally had a chance to get everything mounted and connected for a first test. This machine is fitted with a Duet 0.8.5 and BLTouch…

      https://youtu.be/rX8L5HIXgO8

      https://youtu.be/o2YIRTsjx7w

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      • T3P3Tonyundefined
        T3P3Tony administrators
        last edited by

        Nice! Did you need to do anything not covered in the documentation to get it working (I realise you needed the latest firmware version)? If so can you let me know so I can update it. Also is it ok for me to link the first video as an example?

        www.duet3d.com

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        • W3DRKundefined
          W3DRK
          last edited by

          Sure feel free to use the video. I should have tidied up my workbench! I haven't seen any documentation related to using a BLTouch with RepRapFirmware, but it's pretty straight forward to get going…

          • BLTouch 5V leads are connected to expansion header pins 1-2, and the servo lead is connected to pin 21 (PWM for heater 3)

          • BLTouch endstop leads are paralleled with a 240ohm resistor as documented by Antclabs to make it safe for 3.3v logic and connected to E0 endstop header

          • [c]M307 H3 A-1 C-1 D-1[/c] is added to config.g to reserve pin 21 for M42 or servo use

          • M558 is set to probe type 4 and G31 is set for a very low trigger value since the BLTouch only triggers the endstop for 5ms

          • Deployprobe.g macro contains the line [c]M280 P3 S10 I1[/c] to deploy the BLTouch probe

          • Retractprobe.g macro contains the line [c]M280 P3 S90 I1[/c] to retract the BLTouch probe

          • Deploy and Retract macros are added to bed.g and homing macros

          And I think that's about it…

          The only issue I've run into so far is the very first probe deployment can take a few seconds before the BLTouch responds and actually pushes the probe down. I'm not sure if it's because the Duet take a little while to setup the PWM or maybe the BLTouch isn't truly 3.3v tolerant and requires a buffer after all, but I need to examine it further. After the first probe deployment it continues to respond quickly like I'd expect, so as a workaround I just deploy the probe at the very top of my homeall.g macro and by the time it gets around to homing Z, the probe has been deployed and everything works fine.

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          • dc42undefined
            dc42 administrators
            last edited by

            There appears to be a bug along the lines you describe when using heater 3 as a servo. It's on my list to fix in 1.17. The other expansion heater channels don't have the problem.

            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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            • W3DRKundefined
              W3DRK
              last edited by

              Ok thanks for mentioning that! Certainly saves me some troubleshooting…

              @dc42:

              There appears to be a bug along the lines you describe when using heater 3 as a servo. It's on my list to fix in 1.17. The other expansion heater channels don't have the problem.

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              • dc42undefined
                dc42 administrators
                last edited by

                This bug is fixed in the 1.17dev4 build. It turned out to be an undocumented chip-level bug in the PWM subsystem and it took me hours to find a workaround.

                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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                • W3DRKundefined
                  W3DRK
                  last edited by

                  David, I can't thank you enough for all the hard work and dedication you contribute to this firmware! I'll install your 1.17 dev build this weekend and let you know how it works out.

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                  • Alex9779undefined
                    Alex9779
                    last edited by

                    I was curious so I ordered one too.
                    I set all up so far for testing and but stumbled over something.
                    The BLTouch is 5V powered from the servo input so its output signal is also 5V.
                    I know, and it is described, the resistor is also provided, that I can use the 240ohms resistor between the output and ground to reduce the voltage.
                    But I am a proud beta tester of the Duex2 and it provides endstop ports where I can select the operating voltage…
                    All I need now would be a remapping possibility that a probe of type 4 (M558 P4) would not use E0 endstop but E2 or E3.
                    @dc42 would that be possible or is this outa reach? I just wanna be safe and a resistor crimped into the plug or soldered in somehow might break and then I have a problem. With the Duex now allowing 5V endstops I could omit the resistor and just use one of those native ports.

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                    • dc42undefined
                      dc42 administrators
                      last edited by

                      That could be done, but it is not likely to happen soon because my priority is to finish the grid bed compensation code.

                      I think it is very unlikely that that 5V applied to an endstop input on the Duet WiFi would damage the microcontroller, because the endstop input includes a series resistor. The Z probe input is even better protected. So I suggest you use the resistor, connect it to the Z probe input, and select probe type 4.

                      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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                      • Alex9779undefined
                        Alex9779
                        last edited by

                        Hmmm but the manual states that type 4 uses E0, so how can I connect it to Z probe input?
                        Or are they the same?

                        Edit: reading between the lines of the documentation I assume yes… But I found no definite statement....

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                        • dc42undefined
                          dc42 administrators
                          last edited by

                          Sorry, I meant type 5.

                          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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                          • W3DRKundefined
                            W3DRK
                            last edited by

                            David, I forgot to update that 1.17 dev4 does indeed fix the delay with heater 3 as a servo on a wired Duet. Everything is working absolutely perfectly and I'm extremely pleased with how well the BLTouch works. Thanks!

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                            • W3DRKundefined
                              W3DRK
                              last edited by

                              @Alex9779:

                              I just wanna be safe and a resistor crimped into the plug or soldered in somehow might break and then I have a problem. With the Duex now allowing 5V endstops I could omit the resistor and just use one of those native ports.

                              For what it's worth I soldered and crimped the resistor in my end-stop connector just to make absolutely sure it's well connected.

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                              • deckingmanundefined
                                deckingman
                                last edited by

                                Just curious as to how accurate this BL touch thing is for homing. I currently use DC42s excellent probe which works fine but the slight issue I have is that I have 3 pieces of glass with different surface coatings that I swap between. So if I go from say, plain glass with 3DLAC to glass with blue tape, I have to edit my config.g to change the Z offset for that particular surface. It occurs to me that the BL touch might negate the need to do that. Is that reasonably assumption?

                                BTW, I've managed to build my machine such that the bed is both flat and level and stays that way, so I have no need to compensate for level or flatness (although it is nice to use the probe to check from time to time). It's just Z homing with different surface materials that I'm interested in.

                                Ian
                                https://somei3deas.wordpress.com/
                                https://www.youtube.com/@deckingman

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                                • T3P3Tonyundefined
                                  T3P3Tony administrators
                                  last edited by

                                  Ian

                                  How about a black sticker at the corner of each bed plate - be out of the way for nearly every print and should give the same result?

                                  (sorry to hijack the bl touch thread!)

                                  www.duet3d.com

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                                  • deckingmanundefined
                                    deckingman
                                    last edited by

                                    @T3P3Tony:

                                    Ian

                                    How about a black sticker at the corner of each bed plate - be out of the way for nearly every print and should give the same result?

                                    (sorry to hijack the bl touch thread!)

                                    Tony - that's a damned good idea - so simple! My initial reaction was that it wouldn't work with blue tape due to the thickness of the tape itself, but as long as the black sticker is on top of the tape (or any other material) then of course it will work. Brilliant! Thanks

                                    Ian
                                    https://somei3deas.wordpress.com/
                                    https://www.youtube.com/@deckingman

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                                    • W3DRKundefined
                                      W3DRK
                                      last edited by

                                      @deckingman:

                                      Just curious as to how accurate this BL touch thing is for homing.

                                      Antclabs claims a standard deviation of at least 0.01mm–apparently dependent on the probing speed due to the way hall-effect sensors work. I haven't had time to do more than about a dozen prints on this machine since fitting it with the BLTouch, but so far it's been working great and I haven't needed to adjust the Z offset since the initial setup. Perfect first layers every time.

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                                      • StephenRCundefined
                                        StephenRC
                                        last edited by

                                        @deckingman:

                                        I currently use DC42s excellent probe which works fine but the slight issue I have is that I have 3 pieces of glass with different surface coatings that I swap between. So if I go from say, plain glass with 3DLAC to glass with blue tape, I have to edit my config.g to change the Z offset for that particular surface.

                                        Use a macro to set the z offset. I have one for pla and another for petg. The two different filaments need a different z0 setting to get it to stick properly.

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                                        • Treitoundefined
                                          Treito
                                          last edited by

                                          Did you directly connect the Servo to Pin21? Does this PIN provide 5 volts or would I need some sort of diode?

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                                          • Jdn-zaundefined
                                            Jdn-za
                                            last edited by

                                            Just ordered myself a bltouch and will be adding it to my duet 0.8.5, thanks for documenting the install mate

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