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

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21 Jun 2016 08:59 #76334 by pippin88
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
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21 Jun 2016 19:06 #76364 by PCW
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
The following user(s) said Thank You: tripwire
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22 Jun 2016 02:08 - 22 Jun 2016 02:09 #76383 by pippin88
PCW, thanks for the reply.

Like so?:

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Last edit: 22 Jun 2016 02:09 by pippin88.
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22 Jun 2016 02:48 #76387 by PCW
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22 Jun 2016 11:19 #76411 by pippin88
Works great, thanks.
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15 Mar 2018 10:44 #107366 by draganius
Is this correct?


Thank you.
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15 Mar 2018 13:53 #107373 by andypugh
That should work.
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15 Mar 2018 14:31 #107374 by draganius
Thank you Andy, very much. :)
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18 Mar 2018 02:06 #107480 by JohnnyCNC
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
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18 Mar 2018 20:18 #107509 by draganius
Great work!
Maybe you can put magnet instead of alligator clip.
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