Filament Runout Sensor

thingiverse

I've created this filament run-out sensor using your choice of filament and just two strips of aluminum can. I haven't tested it yet, but it should work as long as the aluminum is free of any paint or plastic coating. Two strips of roughly 3.25mm wide aluminum can will fit perfectly in the slits on the inside of the part. These strips will converge to form a switch that is "off" when there's filament in the part. When the filament is removed, these aluminum strips will touch again, creating a closed circuit. As you insert the angled strip of filament, I suggest bending the tip (roughly the first 3mm of aluminum) upward so it won't get caught on your filament as you remove it. Then, bend the end section (maybe 10mm of aluminum) downward to ensure a good connection with the other flat strip of aluminum.