K8200 / 3drag Auto Bed Leveling with Capacitive Proximity Switch

You need:
1 x LJC18A3-H-Z/BY (PNP Capacitive Proximity Switch)
1 x BC107 or BC547
1 x 100k Resistor
Some shrinktube
All together ~10EUR depending on Sensor availability (Ebay, Amazon, Aliexpress...)
Inspired from http://www.thingiverse.com/thing:434665 I made an own solution. The wiring you see on the picture. I use it with actual Marlin from GIThub. The Z-Switch have to be inverted in configuration and the Leveling must be activated. Here yo see a small Video of my printer with leve