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I am trying to add a 2nd touch down probe to UCCNC. My problem right out of the gate is that as soon as I assign a PIN and Port number to the second probe settings the first probe stops working. I don't even having anything hooked up to the CNC4PC C76/C78 control card. So initially at least this is a UCCNC settings issue.

Probe #1 works just fine with my touch down probe which is a 3-point plate unit for straight down or side hit probing. It has it's own control board with a RJ45 connector cable from it back to the C78. You can see my settings in the attached image.

But as soon as I add Pin 7 / Port 2 as the 2nd probe address in the I/O settings page of UCCNC I get a PROBE IS BUSY error message when I try to use Probe 1.

Any suggestions on what I've got set wrong?

Thanks,
BH

Is one NO, and the other NC? If so, you may need to change the Active Low setting for the second one.

Gerry,

Thanks for the help.

Changing the ACTIVE to LOW vs HIGH made no difference.

HOWEVER, after more experimentation I found that any PIN on PORT 2 would yield the same result of making PROBE 1 be seen as busy. So I tried the inputs on Port 3 and those pin/port input options did not interfere with Probe 1. So I've set Probe 2 to Pin 2 / Port 3 and now Probe 1 is working as it should.

Now, moving forward, Probe 2 is the type that completes the circuit to ground. In effect I'll attach an alligator clip to the collet nut and when the bit touches the probe the circuit to ground will be completed. Very standard arrangement I believe.

My next question is what to do with the Port 3 / Pin 2 input. I'll have 2 wires from the probe coming back to the control........one will be taking ground out to the probe and one bringing it back once the bit touches the probe and completes the circuit.

What I don't understand, and haven't been able to find anywhere is what to do with the two wire ends. It would seem one would go to ground and the other to the Port 3 / Pin 2 input. But that is just grounding the input and I don't know if that is what I need to do. I'd think I'd want a 5v positive signal going to the input.

I apologize if this is all really basic stuff that I just don't have a handle on. I haven't done much with add on devices using the C76 inputs so am a bit lost.

Thanks again,
BH

I think I found the answer. Ground terminal out to the probe and then back to the input pin.