Hi,
I've scoured the net to try and find a solution to this but alas I'm all out of ideas.
I'm in the process of adding auto bed leveling to my Velleman K8200.
Most of it is working very well but one very major and mysterious issue remain. Hopefully someone can help me solve it.
My current status is that I'm using the very latest Marlin version taken from the K8200 github branch to avoid having to do all the configuration manually. All servo angles, offset and everything is configured and seems to be alright. M401 and M402 works perfectly and I don't have any jitter, although I had to increase the PROBE_SERVO_DEACTIVATION_DELAY to 600 because I used a fairly slow servo.
The problem occurs when the servo is extended and I move the z axis or when running G28 or G30.
As previously noted the M401 command extends the servo perfectly. G28 is homing X and Y perfectly and then moves the Z axis up by the defined amount (25mm) and moves the bed to the safe probe point, it then lowers the servo. G30 obviously takes is as red that a safe point is already arrived at and lifts the Z axis and then lowers the servo. After this if i either lift or lower the Z axis manually or when either G28 or G30 lowers the Z axis to probe the servo is retracted past the retraction angle until I press the button to fool it that it has triggered after which it returns the servo to the correct retraction angle.
If i disable PROBE_SERVO_DEACTIVATION_DELAY completely this doesn't occur and the probe works perfectly, except that the servo jitters so much that a blind carpenter with alzeimers could level the bed manually with better result.
Also, if I define PROBE_SERVO_DEACTIVATION_DELAY to something ridiculously high, like 10000, it actually lowers the probe, waits for the delay and then retracts it and starts lowering the Z axis (or possibly the other way around).
At this point the only two things I can think of is that there's some bug in Marlin or that whoever made the K8200 branch made a terrible mistake somewhere. As both these are really cumbersome to try out I figured I could try here first and hope for the best.
Cheers