3DTouch sensor problem (clone of BLTouch)

edited April 2020 in Extruder & Bed
Hi all forumites.

I have a problem with a 3DTouch sensor and I'm not sure if it's the firmware or a sensor problem. I've enabled auto bed levelling in Repetier 1.0.3 and setup the sensor like many explained on the web and this forum. 

My problem is sending the lower command "M340 P0 S700", the sensor doesn't always just dropdown. It sometimes "bounces".

See the video I have uploaded here: 

The command sent in the video was:
M340 P0 S1500
M340 P0 S700

And this was repeated 5 times. Has anybody had this problem before?

All the commands for the sensor works like expected except the dropdown command. For completeness, here's a list of all the commands:

M340 P0 S700 (Probe start script) <--- This bounces sometimes
M340 P0 S1500 (Probe finished script) <--- Always work correctly
M340 P0 S1800 (Self-test) <--- Always work correctly
M340 P0 S2200 (Alarm Release) <--- Always work correctly
M340 P0 S1200 (M119 Test Mode) <--- Always work correctly

Reference: https://www.reprap.me/media/support/BLTouch-Classic1122.pdf

Any help or suggestions would be appreciated.


  • With some further testing, I see the sensor does this as well when I use my finger to touch the dropped down probe. 

    I believe this is enough evidence to show a faulty probe unless someone on this forum has found a solution.
  • I have a bltouch and I have to use 670 instead of 700. I had to mess around with different numbers till I got the ones that worked.
  • I did play around with the values and even tried the ones on Anthony Jordan's blog here. He suggested the values are:

    Marlin Repetier Function
    M280 P0 S10 M340 P0 S648 Pin Down
    M280 P0 S90 M340 P0 S1472 Pin Up
    M280 P0 S120 M340 P0 S1782 Self Test: Pin Up/Down continuously until another command is received.
    M280 P0 S160 M340 P0 S2194 Release Alarm

      Although the values seem to work, it still had that problem
  • Have the BLTouch. It may be, that the pin does not go down fast (or far) enough and "thinks", the trigger position is reached again and the pin is pulled up again. The BLTouch pin is made of metal any is probably heavier.
    Also think, that the distance between release position and trigger position is very close, maybe too close.
  • I'm going to try and re-magnetise the top of the pin and check if it makes any difference. I will report back to this forum with the results.
Sign In or Register to comment.