Mini IR Probe configure issue



  • Hi,
    I have an issue with the initial configuration of the IR probe. I have installed a Duet 2 Wifi in a Ultimaker 2 and have installed the probe as per the instructions, the edge of the board is a fraction over 1 mm from the glass bed. The aluminium base under the glass bed is painted high temp matt black,
    When I test it using the prescribed M & G code procedures I get an analogue reading of 537 and a head z height of 4.84. Having looked at the various similar posts I tried playing around with z endstops and other parameters but get the same results every time.
    Config.g below, any suggestions, help appreciate.

    ; Configuration file for Duet WiFi (firmware version 1.20 or newer)
    ; executed by the firmware on start-up
    ;
    ; generated by RepRapFirmware Configuration Tool on Mon Feb 19 2018 09:02:43 GMT+0000 (GMT Standard Time)

    ; General preferences
    M111 S0 ; Debugging off
    G21 ; Work in millimetres
    G90 ; Send absolute coordinates…
    M83 ; ...but relative extruder moves
    M555 P2 ; Set firmware compatibility to look like Marlin
    ; Automatic saving after power loss is not enabled

    M208 X0 Y0 Z0 S1 ; Set axis minima
    M208 X230 Y210 Z200 S0 ; Set axis maxima

    ; Endstops
    M574 X1 Y1 S0
    M74 Z1 S2

    M558 P1
    G31 P500 ; Set Z probe trigger value, offset and trigger height

    ;M557 X15:215 Y15:195 S20 ; Define mesh grid

    ; Drives
    M569 P0 S0 ; Drive 0 goes backwards
    M569 P1 S0 ; Drive 1 goes backwards
    M569 P2 S0 ; Drive 2 goes forwards
    M569 P3 S1 ; Drive 3 goes forwards
    M350 X16 Y16 Z16 E16 I1 ; Configure microstepping with interpolation
    M92 X80 Y80 Z200 E282 ; Set steps per mm
    M566 X900 Y900 Z120 E120 ; Set maximum instantaneous speed changes (mm/min)
    M203 X6000 Y6000 Z1000 E1200 ; Set maximum speeds (mm/min)
    M201 X150 Y150 Z150 E200 ; Set accelerations (mm/s^2)
    M906 X800 Y800 Z800 E800 I30 ; Set motor currents (mA) and motor idle factor in per cent
    M84 S30 ; Set idle timeout

    ; Heaters
    M305 P0 X200 ; Set thermistor + ADC parameters for heater 0
    M143 H0 S120 ; Set temperature limit for heater 0 to 120C
    M305 P1 X201 ; Set thermistor + ADC parameters for heater 1
    M143 H1 S280 ; Set temperature limit for heater 1 to 280C

    ; Tools
    M563 P0 D0 H1 ; Define tool 0
    G10 P0 X0 Y0 Z0 ; Set tool 0 axis offsets
    G10 P0 R0 S0 ; Set initial tool 0 active and standby temperatures to 0C

    ; Network
    M550 PMy printer ; Set machine name
    M552 S1 ; Enable network
    ;*** Access point is configured manually via M587
    M586 P0 S1 ; Enable HTTP
    M586 P1 S0 ; Disable FTP
    M586 P2 S0 ; Disable Telnet

    ; Fans
    M106 P0 S0 F100 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off

    ; Custom settings are not configured


  • administrators

    Your command:

    G31 P500 ; Set Z probe trigger value, offset and trigger height

    sets the threshold but not the trigger height. So if the trigger height really is 4.84mm, add Z4.84 to that line. However, 4.84mm is abnormally high.



  • Yes I did try that and it triggers at 4.84, but then when I move to Z0 the nozzle is still 5.7 above the bed. I double checked that the Z was actually moving the correct distance and it is. I also checked the board mounting and it is at 90 degrees and the bottom edge is parallel with the bed.


  • administrators

    How are you homing the Z axis? Please post your homez.g and homeall.g files.



  • I haven't used the homeall.g yet. I have changed homez to travel to the bed centre, after homing x and y.

    ; homez.g
    ; called to home the Z axis
    ;
    ; generated by RepRapFirmware Configuration Tool on Sat Mar 10 2018 15:56:47 GMT+0000 (GMT Standard Time)
    G91 ; relative positioning
    G1 Z5 F6000 ; lift Z relative to current position
    G90 ; absolute positioning
    G1 X110 Y115 F6000 ; go to first probe point
    G30 ; home Z by probing the bed

    ; Uncomment the following lines to lift Z after probing
    ;G91 ; relative positioning
    ;G1 Z5 F100 ; lift Z relative to current position
    ;G90 ; absolute positioning

    ; homeall.g
    ; called to home all axes
    ;
    ; generated by RepRapFirmware Configuration Tool on Sat Mar 10 2018 15:56:47 GMT+0000 (GMT Standard Time)
    G91 ; relative positioning
    G1 Z5 F6000 ; lift Z relative to current position
    G1 S1 X-235 Y-215 F1800 ; move quickly to X and Y axis endstops and stop there (first pass)
    G1 X5 Y5 F6000 ; go back a few mm
    G1 S1 X-235 Y-215 F360 ; move slowly to X and Y axis endstops once more (second pass)
    G90 ; absolute positioning
    G1 X15 Y15 F6000 ; go to first bed probe point and home Z
    G30 ; home Z by probing the bed
    ;G1 Z5 F100 ; uncomment this line to lift the nozzle after homing


  • administrators

    Please measure your IR sensor trigger height again. Two things to watch out for:

    • If you have direct sunlight (no clouds in front of the sun) reflecting off the bed into the sensor, then it may be overloaded and trigger early. In this case, the LED will blink rapidly to indicate that there is a problem.

    • Very occasionally we find that an IR sensor triggers at two different heights: the normal one (which should be between 2.5 and 3.5mm, when using a 3mm thick glass target backed by black paper) and at another greater height.



  • Thanks for your patience. This is doing my head in.
    No sunlight issues, its located in windowless workshop lit with a 80 watt bulb. With thin paper on the glass touching the nozzle a 1mm thick ruler will just pass under the board.

    One thing I have noticed and forgot to mention earlier, is that the trigger led does not turn off until Z reaches 5.7mm. I have been taking it to 6mm when running the G30, but this shouldn't make any difference to the trigger height. It might however mean something, the analogue read out at this point is 465.

    I have tested for any multiple triggers, nonone noted. I have also placed matt black paper under the glass which marginally blacker than the paint, but still get the same result.



  • Just one other question. The readout is always one of 0, 465 or 537. Should their be intermediary readings as the z is moved?


  • administrators

    The output should alway be close to 0, 465 or 535; except in the case of direct bright sunlight, when it may reach 1000.

    The reading should be 0 when the sensor is a long way from the bed. When it is several mm from the bed, it should rise to 465 but the LED should remain off. The 465 reading warns the firmware that it is close to the bed, so that it can reduce the probing speed. At trigger height the reading should rise to about 535, the LED should come on, and probing should stop. If you then raise the nozzle a fraction of a mm then the reading should drop back to 465 and the LED should go off.

    The LED should only be on when the analog reading is about 535. It should be off if the reading is 465.


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