IR-Sensor , read out value ranges change unforseable from time to time

  • Hi all,

    I got some new strange behavior from my IR-probe. Does anyone had something similar ?

    My configuration :

    David adapted my IR-probe for high reflecting materials (to be less sensitive).
    I currently have a natural color FR4 plate on my print bed where I had roughened the surface with sandpaper.
    I had also to adjust the angle of the IR LEDs mechanically, because roughened with sandpaper influenced the read out values.
    This was working fine for many weeks.
    Suddenly when the printer calibrates axis for a new print, the nozzle was going into the bed.

    It shows the read out values from the probe starts vor greater high with 0 and jumps than when moving the sensor to the bed to a value ~ 396 - 450 (but defenitely below 500).
    Moving the sensor nearer to the bed, at some distance the value increases a bit, but still below 500 . Moving further downwards, the value decreases and at some point it is 0 again.

    I put a white piece of paper on the surface, but still the value is below 500.

    I had the printer powered off over night and next day, all was working again fine. Until some days later I had the same issue, with even lower values.
    In detail, I calibrated all axis manually and start than the print process, I heated at the beginning the hotend and bed up
    and than the print start with calibration of all axis again. This time z-axis run into the bed again.

    I did the z-probe readout with a piece of white paper again and it showed the z-probe value is even below 400 (as the highest read out value).
    One run of the read out values as example :

    probe Value
    height readout
    7.28 = 0
    7.27 ~ 400
    6.87 ~ 420 (LED turns on)
    4.71 ~ 420
    4.70 ~ 220 - 250
    4.68 ~ 30 - 60 (LED turns off)
    4.50 = 0

    The key point I noticed, the value is always below 500 and this makes the calibration with a trigger value of 500 not working.

    What can be done to avoid this situation ?

    *update -1- *
    I moved the x coordinate about 5 mm and currently I get again read out values > 500 and more stable. This may be a workaround, or just the probe works as should for some time again.


  • Maybe something got on the ir leds, e.g. If you are using hairspray to improve surface adhesion, you may have ovetrspray‚Ķ

  • administrators

    Most likely you have a bad connection between the IR sensor and the Duet.

  • Damn stuff with periodic errors, currently it is working as expected and I can not troubleshoot.

    Keep you posted.

    @Qdeathstar : I use no haispray or other adhesives for the first layer.

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