[kolias]

Hey Al

On my last cnc I had a touch plate for auto-zero of the Z axis and worked really well

I like to install the same on my new cnc but I don’t remember what I did about this 10k resistor Chris (from cockrum.net) is talking about. Here is a part of his instructions:

“….The idea is to use the cutter itself and a soft conductive plate as a switch that triggers the probe input on Mach3. The touch plate is connected to a parallel port input pin that is pulled up to +5V with a 10k resistor and the ground is connected to an alligator clip. The ground is clipped onto the cutter bit and the touch plate is held on the work surface. Clicking the Auto Tool Zero button runs the Visual Basic code that lowers the cutter until it gets a signal from the probe input, sets the Z-axis readout to the thickness of the touch plate (.060" in my case) then raises the cutter to 1 inch above the surface”

I have reserved Input #4 on the G540 for this auto-zero plate. If I connect the Red wire from the touch plate to Input #4 and the Black wire from the alligator clip to ground, would it be ok?

BTW I may have more questions as I’m progressing with the start-up of my new cnc. Should I keep posting here or open a new thread for each subject?

[Al_The_Man]

Obviously this touch plate has to be insulated from ground or machine common/frame/table otherwise it will trip right away.
Where ever you input the plate wire, you need to install a 10k resistor from this point to the +5vdc.
I can move these two post to the Mach section if needed.
Al.

[kolias]

And where do I get the +5VDC ?

I attach the schematic from cockrum.net for info. Perhaps there is another way to do the same since my machine is all metal?

[Al_The_Man]

You can get the +5v from the PC itself, you either need to insulate the touch plate some how to get that to work, did they use a insulated sacrificial piece of some kind?
Al.

[kolias]

He used copper clad PCB and I used before a piece of Aluminum angle.

Your idea was good, lets put this subject to the Mach forum. These guys with their metal machines may have a better solution.