Add information about wiring and LinuxCNC configuration.
Cool method to get the tool close in Z quickly, until breaking a fiber optic transmitted lightbeam, and then repeat with precision using a touchoff plate.
https://www.youtube.com/watch?v=v-S4RXMdlrY
https://sourceforge.net/p/emc/mailman/message/28768489/
https://lab.whitequark.org/notes/2014-07-06/g38-probing-workpieces-in-linuxcnc/
Best to use a reference tool that has a small impact, vs. the spindle nose that's broad?
Show probe trip during move. Shows need for longer debounce to avoid false trips. May be best to disconnect? Though that could cause trouble if you forget to reconnect and crash into the probe.
An automatic tool length probe is a quick way to measure tool length. No manual measurement and no manual touch off if the tool holder lacks repeatably.
I considered a couple ways to mount the tool probe. The first included a boss feature that would center the probe. This might be nice when routing the cable and tubing. Also the auto-centering would help return the probe to the same spot if frequently removed.
In the end, I picked the easier method of making a couple t-nuts and mounting the probe in a t-slot.
When mounting the probe, check that there is sufficient clearance to sweep and center the probe beneath the spindle. Also that there are no pinch or collision points.