Z probe already triggered (with I0 and I1)

  • Dear Friends,
    i hope it is a small issue and anyone has a advice for me.
    I use a NPN Normally Open sensor but it always gives me the error:

    G28 Z
    Error: Z probe already triggered at start of probing move
    Error: Homing failed

    Hardware: Duet 2 Wifi
    Board: Duet 2 WiFi (2WiFi)
    Firmware: RepRapFirmware for Duet 2 WiFi/Ethernet 3.1.1 (2020-05-19b2)
    Duet WiFi Server Version: 1.23

    Probe: lj12a3-4-z/bx-5v

    connected as described in: https://duet3d.dozuki.com/Wiki/Connecting_a_Z_probe#Section_NPN_output_normally_open_inductive_or_capacitive_sensor

    No matter if I invert the probe via M558 or not. (If I start homing with a piece of metal below the sensor it starts)

    See my Tests and config:


    ; Z-Probe
    ;M558 P1 C"zprobe.in" H5 F120 T6000
    M558 P5 C"zprobe.in" H5 F120 T6000 I1         ; set Z probe type to unmodulated and the dive height + speed
    ;G31 P500 X0 Y0 Z2.5   
    G31 X0 Y0 Z2.5                           ; set Z probe trigger value, offset and trigger height
    M557 X15:215 Y15:195 S20                       ; define mesh grid


    ; homez.g
    ; called to home the Z axis
    ; generated by RepRapFirmware Configuration Tool v3.1.3 on Mon Jun 22 2020 09:53:01 GMT+0200 (Mitteleuropäische Sommerzeit)
    G91              ; relative positioning
    G1 H2 Z5 F6000   ; lift Z relative to current position
    G90              ; absolute positioning
    G1 X15 Y15 F6000 ; go to first probe point
    G30              ; home Z by probing the bed

    The web Ui confirmes that the probe is connected and reads the values.
    Default : ZPROBE 1000
    With piece of metal below: ZPROBE 0

    Results with I0/I1 when homing:

    G31 Readings with I0 and I1

  • From wiki - Invert the input by prefixing the input pin (C parameter) with ! character, when using an NPN output inductive or capacitive sensor or using an NO switch (not recommended, use a NC switch instead).

    I1 parameter does not work for firmware 3.x, so try M558 P5 C"!zprobe.in" H5 F120 T6000

  • Thank you, you are a wizard! It works perfectly!

  • You welcome, but for future reference the icon that looks like book on top of your screen (Duet3d documentation) makes you a wizard as well, if you read it. 🙂

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