Hi Guys, thank you very much for this explanation! I am using a different controller from CNC3D but it uses GRBL. I’m connecting a NPN-NO touch probe to this PNP input controller (not ideal).
For anyone else who is confused like me, having a PNP probe input will only have two wires, +12V signal, and ground (these typically used for Z height zeroing.
It might be possible to connect a NPN “3D digitizing” touch probe with 3 wires, but you might need to connect the third wire to another +12V rail.
IMPORTANT: But I have been told that adding a second +12V to the already +12V Signal wire might blow the transistor, even though its only 24V.
Never knew about this circuit setup, but I will try getting a PNP-NPN converter just to be safe!! 