This was my approach of automating the bed leveling of lulzbot taz 5.
I created a small probe holder and used a 12mm capacitive proximity sensor.
I’m using an OMRON E2K-X4ME1 Proximity Sensor, Capacitive, 12mm, NPN, NO it is more expensive than other sensors, but I’m getting super reliable measures and it is working great.
I did not test it using 5V, the rambo board inside TAZ have a spare +24v output, and there are plenty empty pins on the original z-axis cable to pass +24V to the sensor. I’m using an Opto-isolator to connect the sensor to the endstop. I made a small board with proper molex connectors and heatshrinked everything. I prefer using a proper 24V instead of running the sensor on a not “supported” condition, and using a small and cheap Opto-isolator is perfect to protect your printer.
The schematics of the circuit is pretty simple:
I’ll post more details and information tonight.