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Inductive Probe Issues


Well-known member
Issue: Z endstop will not trigger when a metal object is close.

I have an Omron TL-Q5MC2 2M inductive probe (stock part taken from my other Fysetc 2.4 build):

A 2 piece Hartk stealthburner head:

I've confirmed that the probe is getting 24V, ground is correct and the signal wire teases out to the mainboard via ohm meter.

Plugged into PA3 (Z endstop) on a Spider 2.3. (though I have not wired up a simple switch to see if that's working. The X and Y end stops work fine, so I don't think that's the problem).

The probe will turn the light off when a metal tool is close and the Signal >> Ground will flip states, but only by 0.6 volts.

The probe wiring is:

Brown >> 24V
Black >> Signal
Blue >> Ground

Printer is a Switchwire conversion.

relevant code section in printer.cfg

pin: ^PA3
x_offset: 0
y_offset: 25.0
z_offset: 0
speed: 10.0
samples: 3
samples_result: average
sample_retract_dist: 3.0
samples_tolerance: 0.006
samples_tolerance_retries: 3
Last edited:
Signal to gnd isn't a very useful measurement on that probe, since it pulls to gnd. Signal to v+ is more informative. However, it sounds like you probably have some other issue.

Misinstalling the v-/gnd wire is one common mistake with these toolhead boards: make sure that wire is going to the DC gnd (labelled v- on the meanwell psu) and make sure if you have a multi-psu system, that all v- are bridged together.
Traces the wires and my signal and ground where switched. Swapped the pins on the probe sensor and it’s all good.