Mini height sensor Having Problems

  • I have Mini differential IR sensor by dc42
    FIrst Problem (Fixed)on power up is flashes 2 time not 4.
    I move Z Probe In to Z Probe_Mod and set M558 P1
    Got 4 flashes

    Does not matter if Z probe or Z Probe_mod is wired

    Now I
    M558 P1 and G31 P500 Z1.0
    and P2 and P3
    It only shows 468 no matter what the height is Z

    The Red Light goes on at the correct height

    My Bed is a Black aluminum Heat bed with Glass on top, using glue stick on top of that

  • administrators

    M558 P1 is correct. Can you post a photo showing the connections you have made at both ends of the cable?

  • Sensor Wiring
    Out GND VCC
    White Black Brown

    Wire to Wire Connector
    White Black Brown
    White Black Red

    To the Duet Wifi

    Z Probe IN GND Z_Probe_MOD +3.3V
    White Black Red

  • administrators

    Your connections look correct to me. Please check the displayed readings again. You should get a reading near zero when there is no surface near the sensor, about 465 when there is a surface close but the LED is not on, and a value around 535 when the red LED is on. If you are seeing 468 all the time, then either the web interface is not updating or there is a bad connection somewhere in the white wire.

  • Found 1 problem my Z Probe IN Wire that was reading several M OHM's (Replaced)

    The wire itself was the problem not the connector.


  • administrators

    You should get 4 flashes using M558 P1, or 2 flashes if you use M558 P5.

  • Ok I think I have this figured out
    I was trying the command by sending gcode through the web not in the config.g

    Once I put the commands in config.g
    On reboot I got 4 flashes and it looks like it is working.
    I will be testing more tomorrow after I remount and rewire it back in place

    This bring up a few question
    1. on boot up does the sensor output become a input to read the config from the duetwifi in the first 4 seconds?
    2. Is this only done at bootup or can this be triggered at any time?
    3. Does the sensor use all 6 Z probe modes?
    4. What does each flash mean 1,2,3,4,?
    5. Is there a place I can read these details


  • administrators

    1. Yes, it looks to see if there is a pullup resistor on that pin.
    2. Only at boot time
    3. It is intended for use in mode 1. You could use it in mode 5, then you should get 2 flashes.
    4. 2 flashes mean it's detected a pullup resistor and started in digital mode, 4 flashes means no pullup resistor detected and it is in analog mode. After that, rapid flashing means the phototransistor is saturated e.g. due to bright sunlight reflecting off the bed into the sensor.

  • Duet Wifi v1.0 with 1.81 firmware; T3P3 hot end printed part with brass inserts , version for All Metal effector.
    dc42 IR Sensor , new version with surface IR emitters and detector. 24V psu
    E3D V6 hot end with new heater block for cartridge thermister and silicone sock.
    T3P3 glass bed with black paper.

    Sensor flashes 4 times on power up , and reads 537 when white paper triggers red light.
    Using feeler gauges the height between bottom edge of IR sensor board and the hot end nozzle tip is about 2.4mm
    The problem is that with no white and in a darkened room, after calibrating G92 Z0 to cartridge paper thickness =-
    the Z probe reading stays at 465 and never triggers the sensor fully so nozzle end hits glass bed!
    Does this simply mean the trigger height is less then 2.4mm?
    With this hardware configuration I cannot see any easy way to reduce the distance between ir sensor and nozzle tip.
    Anyone any ideas?

  • I have a workaround.
    I took 0.8mm off the unthreaded end of the heat break.
    now the IR sensor fires at z=0.35mm, so before the nozzle hits the bed glass

  • administrators

    I'm glad you fixed it. The fitting instructions for the IR sensor suggest that you aim to have the bottom of the board 1.5mm higher than the tip of the nozzle.

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