OptoTap filament motion sensor with BMG gear

Printed all parts out of PETG, usual Voron settings, no supports needed.

BOM: M3x25 bolt, two M3x8 bolts for OptoTap, two M2.5s for switch should you want to use it, one BMG gear (preferrably idler as the one with grub scew can be used for extruders and MMUs) with a pair of roller bearings, one or two M3 washers (depends of your printer calibration), 623ZZ bearing should you want to print with TPU (testing so far shows that bearing is not needed as long as filament is solid).

I intend to use it just with the rotary sensor for now. Whatever MMU I'll add, will get a separate sensor at the MMU or this is what I think.

WORK IN PROGRESS - as of 11.04.2025, I added MR115 version to the mix.

Quick prompt to AI gave me this configuration for Klipper:
[filament_motion_sensor filament_sensor]
detection_length: 7.0
extruder: extruder
pause_on_runout: True
switch_pin: PA0
runout_gcode:
M117 Filament Jam or Runout
PAUSE
insert_gcode:
M117 Filament Flow Restored

Code looks alright. PA0 pin is dummy pin - set your own according to your MCU manual.