Problems with BLTouch V3.1



  • Hello,
    I have a Duet 2 Wifi Bord running firmware version V2.04RC4. Attached to that board there was a BLTouch V1.0, which worked perfectly.
    Due to a mechanical defect on this sensor, I had to replace it.

    Now I have a BLTouch V3.1 Sensor, but it doesn’t work correctly any more. On power on, the sensor makes the self-test and I am able to deploy and retract the probe correctly.
    But when I try to home, the pin touches the bed , but the board doesn’t recognise it. So that the nozzle crashes into the bed. There appears no blue light…

    What do I have to change to get this V3.1 sensor to run?

    Here is my setup:
    config.g:
    ; Endstops
    M574 X1 Y1 S1 ; set active high endstops
    M574 Z1 S2 ; set endstops controlled by probe

    ; Z-Probe
    M307 H7 A-1 C-1 D-1 ; disable heater on PWM channel for BLTouch
    M558 P9 H5 F120 T6000 ; set Z probe type to bltouch and the dive height + speeds
    G31 P600 X49 Y0 Z2.5 ; set Z probe trigger value, offset and trigger height
    M557 X50:450 Y50:450 S200 ; define mesh grid

    deployprobe.g:
    M280 P7 S10 I1; deploy BLTouch
    G4 P100 ; Pause 100ms
    M280 P7 S60 I1; Touch SW Mode
    G4 P100 ; Pause 100ms

    retractprobe.g:
    M280 P7 S90 I1; retract BLTouch

    homez.g:
    G91 ; relative positioning
    G1 H2 Z5 F6000 ; lift Z relative to current position
    G90 ; absolute positioning
    G1 H2 X210 Y250 F6000 ; go to first probe point
    G30 ; home Z by probing the bed
    G91 ; relative positioning
    G1 H2 Z5 F100 ; lift Z relative to current position
    G90 ; absolute positioning

    Thank you for your help.



  • Hi,

    Just FYI you can always safely test this sort of thing by, in this case, moving the nozzle well away from the bed, triggering the test and using your finger to lift the pin. This way you have time to shut things down rather than have a bed crash.

    In any case you need two files: deployprobe.g and retractprobe.g and they each should only have one M280 command that performs the associated action.

    Unless something has changed "Touch SW Mode" is not used. At least my BLTouch 3.0 works fine without it.

    Frederick



  • Hi fcwilt. thanks for your reply. After I had the first crash, I of course tested it the save way. Can you post your config and probe files?
    I also tested it without the Touch SW Mode - same negative result.
    Becomes your sensor blue if it triggers? Mine is only red...



  • tripple check the wiring.



  • @btmerz My sensor is blue when the pin is down and solid red when the pin retracts. It does blink red when the pin is up and the alarm mode is triggered.



  • So then it could be, that I have a defective sensor? When I deploy the probe with M401 it is dark (red switches off, no blue).



  • @btmerz said in Problems with BLTouch V3.1:

    So then it could be, that I have a defective sensor? When I deploy the probe with M401 it is dark (red switches off, no blue).

    do you use M501 and config-overwrite.g?



  • No,
    sorry, but what's that for?
    Doest it read the whole config at power on?
    What should be inside the config-overwrite.g file?



  • it could overwrite your settings. please post the entire config.g



  • @btmerz said in Problems with BLTouch V3.1:

    I also tested it without the Touch SW Mode - same negative result.

    So you created the two files I mentioned and entered in the correct M280 commands?

    Did you verify operation using M401 and M402?

    Frederick



  • @fcwilt yes. M401 and M402 are working as expected. Deploying and retracting the pin.



  • @delvis said in Problems with BLTouch V3.1:

    @fcwilt yes. M401 and M402 are working as expected. Deploying and retracting the pin.

    Well then it should work in all instances that rely on M401 and M402.

    Try changing the P parameter in the G31 command to 20.

    SInce M401 and M402 work we know that the wiring that controls the BLTouch is working.

    What we don't know yet is if the wiring which sends the signal to the Duet is working. If something is wrong there that could explain the problem you are seeing.

    Double check that wiring.

    Frederick



  • Check the white wire especially. I believe that is the signal wire.


  • administrators

    It sounds as though either the BLTouch isn't triggering, or there is a short circuit between the signal output and ground, or the internal pullup resistor in the Duet MCU isn't working. Suggestions:

    1. Send M558 without parameters and check that it reports probe type 9.

    2. Disconnect the white wire from BLTouch to the Duet (and the black wire at the same time if it's easiest, it doesn't matter). The Z probe reading in DWC should jump to 1000. If it does, that implies that the BLTouch isn't triggering, or that its output has a large leakage current, or there is a stray strand of wire shorting the white and black wires together.


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