7i76 and Z axis touch plate (short to ground)

Hi,

I've got a 7i43 and 7i76.

I want to implement a Z axis touch plate - for tool / workpiece touch off. I've previously done this successfully with a G540 ( 7xcnc.com/software/probing/z-touch-plate/ ). I just use a piece of copper PCB with a wire soldered to it. Then I have another wire with a clip on the end, clipped to the tool/spindle. The tool probes down and when it touches the PCB, closes the circuit / triggers the input.

The problem I'm having is the 7i76 has sinking inputs. I'm using 12V field power. My tool is grounded through the spindle back to the VFD. In the current state that means 12V gets shorted to ground.

Can I use a circuit from ground to an input pin and have it trigger?
How should I wire this up?

Thanks,
Nick

One way is to add a say 2K pullup resistor on the 7I76 sense input to 12V
so the 7I76 input will read high until shorted to ground

PCW, thanks for the reply.

Like so?:

Yep

Works great, thanks.

Is this correct?


Thank you.

That should work.

Thank you Andy, very much.

Hi Guys,

Thanks for the inspiration. I built a touch plate today and got it working. Version 2 of the touch plate is going to have a button right on the touch plate to start the probe sequence.



Thanks
John

Great work!
Maybe you can put magnet instead of alligator clip.