This is the JamSentry. A way of detecting and alerting the user to printer Jams and Filament runout conditions. It does not require changes to the printer Firmware. With slight modifications to the G-Code sender it can automatically pause the print when a Jam or Filament runout is detected. It can also emulate a filament runout sensor and trigger the printer to stop via a control signal.
It should work on just about any type of FDM printer and extruder mechanism including dual extruder devices. Due to slightly different tolerances, there are versions for 1.75mm and 3mm filament.
Information on how it works and how to make one can be found at https://robogardens.com/?p=2220
See xxx for more instructions on how to build the unit