Cheap Tool Length Sensor Options

[Andrewg]

Thanks John, nice solution for a real engineer. As a woodworker I need to buy or assemble from purchasable parts.

Coincidentally I noticed from another reply you are based in Cambridge UK, like me.

[AndyUK]

FWIW, My probing routine requires me to touch the plate to the tool to initiate the process. I touch it against the tool and then it pauses for a few seconds, then the machine proceeds to move downwards. This, hopefully checks that there is a working connection.

[m_c]

I'd always recommend testing the probe prior to any automated probing routines.
If you're manually changing a tool, then you're already at it, so for all the time it takes to trigger the probe/touch the plate against the tool, it ensures things are working, and eliminates the risk of a broken wire, or more likely, you've forgotten to plug it in

[Muzzer]

If you fit a "loop back" connection within the probe plug, you can detect if the probe is(n't) plugged in and inhibit probing moves. Requires an additional input but equally it reduces the risk of a crash. Some probes also have a secondary (overtravel) switch that you can wire into the e-stop circuit in case the probe connection doesn't work.