Capacitive Sensor Schematic for Anet A8

The Anet z limit switch is normally 5v and is triggered when the mechanical switch is pushed, grounding the 5v sensing pin to ground. The Capacitive Sensor works by going to ground when it senses a surface. Basically using two rectifier diodes, the Anet board is protected from the higher voltage of the 12 volt sensor, but allows the 5v z limit switch pin to pull to ground when the capacitve sensor senses a surface.

I'm using this setup on two Anet A8 printers and they work great and repeatab