Filament Flow / Jam (runout) with microswitch

thingiverse

Here's a simple and effective microswitch-based filament sensor that detects whether filament is flowing, ideal for any 1.75mm filament. I've connected it to an Arduino Nano. The basic logic revolves around a counter that resets on a "CHANGE" interrupt from the microswitch. If the counter reaches a predetermined threshold value, an output is pulled high - in my case, a buzzer is activated. However, if the printer has some sort of pause method (the UP BOX door sensor can be triggered with a relay), it will automatically pause printing. Check out this video to see the sensor in action: https://www.youtube.com/watch?v=68XpV7J-bkA (sorry about the vertical video).