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

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19 Mar 2018 14:07 #107545 by andypugh
Nickel-plated magnets are conductive, I am not sure if the uncoated ones are.

I used a couple of ring magnets to make my own "Magsafe" connector for my touch probe as I was paranoid about starting the spindle with the probe mounted.

Carbide tools are conductive, but I don't know how magnetic they are (It might depend on how much Cobalt they have in them)

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19 Mar 2018 21:19 #107567 by draganius
Why start spindle when probe mounted?
I saw solution somewhere (magnet instead alligator clip when spindle off).
I will post here when make probe with magnet.

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19 Mar 2018 22:38 #107574 by JohnnyCNC
I thought about using a magnet but didn't like the idea of magnetizing my drill bits. I also thought about a wiper that would stick up and I could push it against the bit while it moves down and makes contact. My only fear would be that the sliding contact might cause and inaccurate detection if the connection is broken just at the split second the tool touches down. I do want to put a button on the touch plate to start the probing process.

John

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20 Mar 2018 00:36 #107576 by DanMN
I've been playing with the idea of using a headphone jack that sends a signal to disable the spindle while it is inserted - the way speakers cut-out when you insert the headphone plug into an audio device.
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21 Mar 2018 02:22 #107650 by JohnnyCNC
Here is version 2.0. I added a button to start the probe process. The body is made of Delrin. That is really nice stuff to work with.
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21 Mar 2018 10:38 #107653 by pippin88
Nice work JohnnyCNC.

My plan is to have a few buttons at the top of the Z axis:
Jog down (medium)
Probe down
Z up to top (fast)

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25 Jun 2018 07:49 #112835 by blazini36

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


It's worth mentioning that since the pin is driven high waiting to go low you have to use the "input-xx-not" pin in hal. Not a big deal but if you make a probe that is unplugable you have to keep the resistor close to the card to that it is not unplugged with the probe. Just dawned on me that maybe somebody would want to put the resistor in the body of the probe itself.
The following user(s) said Thank You: tommylight

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29 Jun 2018 21:48 #113110 by pippin88

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


It's worth mentioning that since the pin is driven high waiting to go low you have to use the "input-xx-not" pin in hal. Not a big deal but if you make a probe that is unplugable you have to keep the resistor close to the card to that it is not unplugged with the probe. Just dawned on me that maybe somebody would want to put the resistor in the body of the probe itself.


Good point.

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