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

 

Post the actual schematic - don't make me work decoding your PCB.

 

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.

I may be reading this wrong, but it sounds like the two are compatible, both go to 0V when they touch something. Why is this wrong?

 

I do height mapping on my CNC3018 when milling copper laminate for making PCBs.
You just need to bridge the sense input to ground.

Since my spindle motor is mounted in a plastic bracket and insulated from ground, I connect a wire from the motor frame to the sense input. When the tip of the cutting tool touches a grounded copper laminate or a thin piece of grounded metal foil, zero height is sensed. This is only done during a mapping procedure or Z=0 probing where Z probing is done very slowly.

 

Sorry guys, hadn't confirmed my account so missed all this. Thanks so much for the replies.
I can't work out how to connect it probe.
I connected the probe to +and - 5v (PC's USB) and connected the probe output pin to the G540 input pin but no good. Maybe I need a common earth between the G540 machine and the 5v supply? I made the circuit board using the mosfet module to try and bridge the sense input to ground like Mr Chips suggests but despite it working great with my multimeter (continuity buzzer) the machine (G540) see's it as constantly earthed regardless of the probes state, as if the mosfet was leaking a small current.

I had used the 4011 in the circuit board to reverse the mosfets action to what I needed the pin to do, e.g. stay open with probe pin high and close (bridge to earth) with the probe pin low but I maybe got confused and over thought it. Anyway can you suggest a connection layout of how to bridge this G540 input pin to earth when the probe output pin goes low. Many thanks and sorry I missed the replys
Ross

 

Remove your circuit.
Do a Z-probe operation.
Touch the sense wire to ground.
The Z-axis should stop moving and back away.
Remove the sense wire from ground when this happens.

The Z-axis should attempt to move downwards again for the actual zero check.
Touch the sense wire to ground again.
The controller should complete the Z-probe operation.