Mendel I2 proximity sensor mount

Proximity sensor mount for Greg's X-Carriage. You can use this to mount the 18mm diameter 6-36V proximity sensors to enable auto bed leveling.

I used this specific sensor and it worked great: [Amazon Link](http://www.amazon.com/uxcell-1-10mm-Capacitance-Proximity-Sensor/dp/B00542U3M4)

You can see it in action on my printer here: https://youtu.be/zFym7SAqkQk

To get this sensor to work you need to hook it up to +12 and ground, and use a voltage divider to keep from blowing up the input on the z endstop.

Two versions. One that uses the center mount point and one that leaves space for a capscrew. I did not have a screw long enough so omitting the center screw allowed me to use the existing screw for the extruder and the two unused mounts to hold the sensor in place.