Touch probe woe's

[Smokie555]

Hi, I hope someone can help me,.. I was trying to setup a cheap touch probe with my 6040/Gecko 540 CNC.

I have a height touch plate connected and working great through a 2.1mm connector jack on the front of my control box so I wanted to use the same plug in connection to work with the touch probe.

Problem is the touch plate simply grounds the centre input pin when the cutter contacts an earthed metal surface, were as the touch probes output wire switches its high 5v signal down to 0v when it touches something.

I thought I had it sorted by building a circuit using a 4011 NAND gate to invert this action (low to high) and then switch a mosfet module like a fast relay to act like the touch plate by simply grounding the Gecko’s input pin across the 0V in and -V out on the mosfet module.

Worked great on the bench with a meter set to buzzer but unfortunately when I tried it on the machine the Gecko pin stays in the earthed state (mosfet relay connected) regardless of the touch probes state (high or low). Maybe a mosfet leaks a little? But I’m no expert on the electronics.

Can anyone suggest what's wrong or think of a better solution. Cheers Ross