IR Probe 539 or 950?



  • I'm following the calibration guide in CaliBration Duet RepRapPro. Have homed and set my nozzle close to the bed and
    set G92 Z0. Now i send a G31 and it says I shouls have around 950 as my value.
    "Duet controller, which converts the voltage into a number. The biggest possible voltage is 3.3 volts, which the Duet would convert to 1023 = 210 – 1. So the 950 means “pretty close”.)"

    But I get 538/539 always.
    On aluminum very close it will go to zero while 2mm distance it was 539 so I covered the aluminum with blue tape now with the nozzle almost touching the bed I have 539.

    Now the guide says to move Z up but the sending G31n untill I you around 600. But if I go from 539 to 434 I'm at 3m while at 2m I have 539 again.

    Question is my IR Probe not working? seeing I do not have the values as in the guide?

    Also what would be an average distance for G31 Zxx PXX which would be about G31 Z2 P539 or would G31 Z2.3 P539 because at Z2.4 I have 464?


  • administrators

    Use the guide specific to the IR sensor, at https://miscsolutions.wordpress.com/mini-height-sensor-board/. The RepRapPro instructions are for a more primitive type of IR probe.



  • Thanks for the link 🙂



  • @dc42:

    Use the guide specific to the IR sensor, at https://miscsolutions.wordpress.com/mini-height-sensor-board/. The RepRapPro instructions are for a more primitive type of IR probe.

    Hi I followed the link and did the setup I just have a question, in the guide it says to always use P500 in the G31 and that the
    final G30 S-1 should be in the range 0.5 to 2.5mm. Now When I use P500 G30 S-1 gives me a reading of 3.009.

    So just to see what would happen I used P539 (whiich is the reading when the nozzle is cloes to the bed.
    In this cas G30 S-1 would give me a reading of 2.516 which is closer to the range in the guide.

    So which should I use P500 like it say even if I have a higher range or P539? I have my bed coverd with blue tape just for info.

    the G30 S-1 command is consistant max diviation on serval trys waht 0.001


  • administrators

    The trigger height will be greater when the target is blue tape than it is with a target of glass, which is how the sensors are tested.

    You will not get a reliable trigger height if you use P539. Use P500, but also check that you get a reading of about 465 just before the red LED turns on, and about 535 after it turns on.



  • Ok great I used P500 even if it was 3.001

    Will try to use maybe white paper?? and see if it changes.

    I get 0 at about 5MM then 464 and the 539.



  • I did the procedure again and I noticed something strange, after lower the head to make it touch the paper
    I sent the G92 Z0 to set Z at 0.

    Then doing the G30 S-1
    Stopped at height 2.913 mm While in the interface I have 2.53
    which is the value rounded of
    4
    M114
    X:219.000 Y:170.000 Z:2.526 E0:0.0 E1:0.0 E2:0.0 E3:0.0 E4:0.0 E5:0.0 E6:0.0 E7:0.0 E8:0.0 Count 62240 7840 12428 User 219.0 170.0 2.5

    Why is there a difference and which one do I have to use in my G31 ZXXX P500 the 2.913 or 2.53?


  • administrators

    The value reported by G30 S-1 is the actual stop height above the bed. The value displayed by M114 has bed compensation applied. If you clear bed compensation first by sending M561 and then do G30 followed by G30 S-1, then the two values should be the same.



  • @dc42:

    The value reported by G30 S-1 is the actual stop height above the bed. The value displayed by M114 has bed compensation applied. If you clear bed compensation first by sending M561 and then do G30 followed by G30 S-1, then the two values should be the same.

    Worked like a charm, I tried again G32 but still amess. So I sent M561 to zero bed compensatopn
    doing G29 I noticed that during probing the Z_Probe value starts around 464 when it moves up it goes to 0 then when the probe is triggered
    it will show 464 again but never 535. Is theis normal?

    Also what makes me wonder is after doing the procedure and clipping the paper to the bed on the far coner I have a reading of 0.03 if I move the carrage to
    the other diagonal coner I clip the paper at the same hieght . So why is G32 or G29 so off?


  • administrators

    If you have the trigger value set to 500 in G31 then the probe will briefly produce a reading of 535 but then it will stop and return to the dive height. So the 535 reading doesn't last !omg enough to see.

    The small difference in nozzle height at the two corners after bed compensation could be caused by any of several factors. For example, any slight variation in the tilt of the print head between the two corners will change the relative heights of the sensor and the nozzle.


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