This is an open source Filament Runout Encoder which detects filament jams in addition to filament runout. You only need a few parts for this project most of which can be found in your shop already.

You can watch the video on how to assemble it here: https://youtu.be/v2mQ4X1J3cs

Bill of Materials 1 - 608 Skateboard Bearing : https://amzn.to/3oyXzEV 2 - M3 8MM Screws : https://amzn.to/3bgc8Jq 1 - M3 6mm Screw: https://amzn.to/3bgc8Jq 2 - M10 Press Fit Fittings: https://amzn.to/390PWQI 1 - Small Rubber Band 1 - Optical Filament Sensor: https://amzn.to/3nm6zf0 8 - 6mm x 3mm Magnets: https://amzn.to/2MFK4oK

Some short lengths of bowden depending on your build https://amzn.to/393qbzo

Links to Download models of the project.
https://a360.co/36g9PmD - Case back https://a360.co/39IIOc4 - Encoder Bearing https://a360.co/39Tvz8u - Case Cover https://a360.co/3p6UoUU - Case Cover Slanted