First design using a Bourns EMS22AFS incremental sensor.
Flowrate sensor is mounted at the egress of a UM2 feeder, ugly print with bad pillowing (not enough top layers).
PMW3360 optical sensor from tindie. Flowrate sensor is mounted at the egress of the feeder. The sensor tracks a spring-loaded knurled wheel that is moved by the filament.
Theese designs are tracking the idler ball bearing wheel of a cut open UM2 feeder.
They are working ok, but there is one drawback compared to the egress mounted sensors: Clogs between the knurled wheel and the entry into the bowden tube can't be detected/prevented. This is the reason for the egress mounted sensor designs.
Sensor device is a optical ADNS 9800 or PMW3360 mouse sensor board from tindie. The optical sensor is connected to the SPI bus of the printer electronics.
The PMW3360 gave better results than the ADNS 9800, it seems that the ADNS firmware is using mouse acceleration...
Round ADNS 9800 optical sensor:
Pictures of the cut open feeder, optical sensor looking from behind at the idler wheel:
To track the idler ball bearing with a optical sensor, it has to have a trackable pattern, this is millimeterpapier: