Optical Filament Sensor v2.1 with Drive Gear - for 1.75mm filament

Comparision between versions

On the pictures you can see designed versions of sensor. All are printed in draft mode. From left V1.0, V2.0, V2.1

Bom

• 3x 619/5 bearings
• spring (I used one from a ballpen)
• end stop optical sensor
• MK8 drive gear
• M5x16 shaft - you could cut M5 bolt
• M3x40 - for idler tension
• M3x20 - for mounting idler to body
• M3x10 - for optical sensor mount
• M3 nut
• M5x35 (M5x30 should also fit)
• M5 nut

Assembly

Source

https://cad.onshape.com/documents/bc431172d582a5a54b3b58ac/w/c4ffc497b40e3855d881f07f/e/8e35b674b9538da00cfbcf5f?renderMode=0&uiState=61d3477ddf0e5e300b92c53c

Calibration.

General good information how to calibrate this sensor is here https://duet3d.dozuki.com/Wiki/Duet3dFilamentMonitor_RotatingMagnetVersion#Section_Calibration

Sensor is supported by:

RepRap firmware -  https://duet3d.dozuki.com/Wiki/Duet3dFilamentMonitor_RotatingMagnetVersion

smoothieware - http://smoothieware.org/filament-detector

Marlin - find in configuration.h FILAMENT_MOTION_SENSOR

Klipper https://www.klipper3d.org/Config_Reference.html?h=filament#filament_motion_sensor - note that klipper required filament change between two high states so calculation is  value = 21mm / (tooth_no) * 3 (mm per status change) - multiple by 3 to increase accuracy and lower mean error

Calculation of value.

To calculate use formula

value = 21mm / (tooth_no *2) (mm per status change)

Example for klipper:

[filament_motion_sensor filament_sensor]
detection_length: 1.43181818182
extruder: extruder
switch_pin: ^PD10
pause_on_runout: True

Example for RRF:

For my configuration with 44T wheel I used this command:
M591 D0 P7 C"e0stop" S1 R50:800 L0.239 E2.64 A1

Example output of checks:

M98 P"0:/macros/Extruder/Check filament sensor"
Pulse-type filament monitor on pin e0stop, enabled, sensitivity 0.528mm/pulse,
allowed movement 50% to 800%, check every 6.3mm, measured sensitivity 0.566mm/pulse,
measured minimum 89%, maximum 101% over 1259.5mm

Those values have some offset due to fast printing with a lot of retraction and enabled PA. 50% is a margin when hot end get clogging. Also could be increased to get it faster.