twitch twitching twitchy spasmatic Servos - how to fix

Just in case anyone is having issues with twitching servos with repetier firmware, this fixed it. I was unable to find a solution, so I figured I would post it. naturally you will need to adjust the deploy/retract pulse value for your needs.

#define Z_PROBE_START_SCRIPT "M340 P0 S550\nG4 P1000\nM340 P0 S0"
#define Z_PROBE_FINISHED_SCRIPT "M340 P0 S2300\nG4 P1000\nM340 P0 S0"

that is deploy/retact pulse value--> dwell 1 second -> end servo pulse.

I have a second system I am trying to get my servo z-probe going on has an addition servo control issue. The above start/stop script stopped the twitching, but had what I would describe more as servo possession. I called a young tech and an old tech, and found that it only happens when the hot end is turned on, which is not needed duting probing, luckliy the HBP pwm doesn't seem to cause it any problems. I just turn the hot end off while probing on that system.

In case it matters, one system is RAMPS 1.4, the one with the PWM issue is a ultimaker 1.5.7 both using Repetier Firmware 0.92.4 dev.

more info:
in action:

you can see it get all twichy as the effector moves down, but then it pauses and no more twitch.


  • Interesting result. Sounds like crosstalk of heater cable modifies the signals to servo.
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