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 leveling in Action: https://www.youtube.com/watch?v=P-rwXnoDe2o Edit 30.09.2014