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

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.

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

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.

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.

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)

PCW wrote:

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.

blazini36 wrote:

PCW wrote:

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.