Filament Monitor

this is a filament monitor using an opto-endstop and is based on the nema 17 exturder gear.

also used http://www.thingiverse.com/thing:156076 for the encoding wheel
video of it in action https://youtu.be/fIHs0a_tPr0

parts needed are:
2 x bearings 5mm id x 10mm od x 4mm thick
1 x 5mm round rod
1 x All Metal 3D Printer MK8 Extruder Aluminum Frame Block http://a.co/7xD3kMU
1 x optical Endstop Switch http://a.co/2EScCYD