BLTouch Strange behaviour



  • Hey,

    I hope anybody has an idea.

    I have installed BLTouch and it was working fine.
    It still does work fine when using G30 during homing.

    But with G29 an error pops up:
    Error: Z probe already triggered before probing move started

    Even though the probe isn't touching the bed...

    While using the different commands (deploy, retract, Reset, Test) I noticed that in Due/DWC the status of the probe sometimes doesn't change. Also tested the cabling and it looks good. Unplugging the BLTouch triggers P1000, but it is showing P0 even when the LED is on...

    Due, DWC and Duet2 Ethernet are running on latest FW.

    Has anybody seen such a behaviour before?



  • It would help to see your configuration.

    Take a look at this: https://duet3d.dozuki.com/Wiki/BLTouch_Troubleshooting



  • Hi

    ; Drives
    M569 P0 S0 ; Drive 0 goes backwards
    M569 P1 S0 ; Drive 1 goes backwards
    M569 P2 S0 ; Drive 2 goes backwards
    M569 P3 S0 ; Drive 3 goes backwards
    M350 X32 Y32 Z32 E32 I0 ; Configure microstepping without interpolation
    M92 X160.00 Y160.00 Z8000.00 E210.02 ; Set steps per mm
    M566 X900.00 Y900.00 Z12.00 E120.00 ; Set maximum instantaneous speed changes (mm/min)
    M203 X10020.00 Y10020.00 Z198.00 E10020.00 ; Set maximum speeds (mm/min)
    M201 X1000.00 Y1000.00 Z100.00 E3000.00 ; Set accelerations (mm/s^2)
    M906 X1500.00 Y1500.00 Z1500.00 E1200.00 I0.3; Set motor currents (mA) and motor idle factor in per cent
    M84 S20 ; Set idle timeout

    ; Axis Limits
    M208 X0 Y0 Z0 S1 ; Set axis minima
    M208 X210 Y297 Z220 S0 ; Set axis maxima

    ; Endstops
    M574 X1 Y1 S0 ; Set active low and disabled endstops
    M574 Z1 S2

    ; Z-Probe Inductive
    ;M558 P5 H5 F120 T6000 ; Set Z probe type to switch and the dive height + speeds
    ;G31 P500 X0 Y0 Z0.52 ; Set Z probe trigger value, offset and trigger height
    ;M557 X5:170 Y5:275 S40 ; Define mesh grid

    ; BLTouch
    M307 H3 A-1 C-1 D-1
    M558 P9 F100 H6 R0.3 T7000 A3 B0 ; Set Z probe type to switch and the dive height + speeds
    G31 P25 X-35 Y-35 Z0.58 ; Set Z probe trigger value, offset and trigger height
    M557 X5:170 Y5:275 S40 ; Define mesh grid

    ; Heaters
    M305 P0 T100000 B4138 R4700 ; Set thermistor + ADC parameters for heater 0
    M143 H0 S120 ; Set temperature limit for heater 0 to 120C
    M305 P1 T100000 B4138 R4700 ; Set thermistor + ADC parameters for heater 1
    M143 H1 S280 ; Set temperature limit for heater 1 to 280C



  • Config looks ok, but take a look through that troubleshooting link and see if anything in there helps.



  • @Phaedrux

    I read thru the troubleshooting, but nothing there.
    What if:
    By disconnecting the black and white cable the P0 changes to P1000.
    So if the signal would stay at P1000 a cable brake or bad connection could be the cause.

    In my case the signal stays at P0 when probe is retracted. Could this indicate a problem with the Sensor itself?


  • administrators

    @hornetrider said in BLTouch Strange behaviour:

    In my case the signal stays at P0 when probe is retracted. Could this indicate a problem with the Sensor itself?

    Yes, or there could be a short in the wiring between the white wire and one of the ground wires.



  • @dc42

    Thanks for the hint.
    I have checked with a spare BLTouch (older one with metal pin) and found that something with the cables was not good.
    Re-Cabled the signal line (white/black) with a brand new cable et voila, it's working again.

    I think I will have to re-do all the cabling to assure functionality....but for now it's working.

    Thanks for the support.


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