Wiring touch probe to 7i77 (Explain like I'm five)

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27 Aug 2014 21:31 #50344 by FOTC
I'm trying to help a friend wire a touch probe and neither of us is very strong when it comes to physical wiring.

The 7i77 has 24V on TB2 Field power. I've wired from that, through the probe to an input on TB8. I've configured HAL so I see the probe signal in Halshow. So far, so good.

I was going to use an 1/8" mono plug on the probe and a panel mount jack on the front of the cabinet to make it easy to disconnect. But when the jack touches the cabinet, bad things happen.

Clearly I don't know what I'm doing. Can someone clarify the right way to wire this or the right kind of connector to use?

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27 Aug 2014 21:45 #50345 by cncbasher
use an isolated mount socket
so the outer of the 1/8th jack is isolated from the chassis

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27 Aug 2014 21:55 #50346 by PCW
I would not have raw 24V power routed to the touch probe

Heres what I would do:

Connect a 4.7K 1/2 W resistor from 24V to the 7I77 input used for the probe
now connect the probe to this input and field voltage GND

Now any shorts while connecting/unconnecting are harmless

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28 Aug 2014 03:53 #50368 by FOTC
cncbasher: Thanks for the right google-ons. (If the local radioshack doesn't carry it, I'm at a loss what to look for.) I found and ordered a suitable isolated jack.

PCW: Thanks. I think I can do that. Any pictures of how people set this up physically to keep the wiring tidy and clear?

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29 Aug 2014 18:41 #50456 by andypugh

Any pictures of how people set this up physically to keep the wiring tidy and clear?


To answer a different question to the one you asked.
I made a magnetic connector for the probe wire as I didn't trust myself not to turn on the spindle with the probe in.

picasaweb.google.com/lh/photo/fdxSMRKCtP...pFm0?feat=directlink
picasaweb.google.com/lh/photo/Dm_lritIjp...pFm0?feat=directlink

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