Would like to use Prusa I3 filament sensor

Hi. I would like to be able to use the I3 style "laser" filament sensor on my custom build using Due and RADDS.
Besides mounting the sensor, it seems likely it would need special firmware to operate properly, to detect filament speed in addition to running out of filament.
Does anyone know if its possible to do this, or if it's even worthwhile?
Thank you,


  • I think it only acts as a switch to detect run out filament. In the docs I haven't read about another function o fthe sensor. Why do you think it can do more? Any hints on that functionality?
  • Now that you mention it, I think you're right. The Prusa is supposed to detect filament slow downs and jams, but I think that is a function of the stepper motor drivers, not the filament sensor as I assumed...
  • Makes sense. Motors with TMC2130 have a stallguard so they could detect this and sensor just sees if any filament is loaded at all.
  • I just read their printing guide closely. It does state that the sensor detects motion in addition to outage. Would definitely like to be able to use it with Repetier!
  • Have you already found out how it is solved on the electronic side? If you can say how it works I can better say what you can use it for.
  • Perhaps a better use would be to send a notification via the informer app that the printer has run out of filament?
  • Seems like Prusa abadonned the sensor. In the latest update to MMU2S the sensor was replaced by a IR sensor triggered if filament is between the extruder drive wheels. Much safer as the old chip seems to have problems with translucent materials while the IR method moving a lever always works.
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