Filament sensor

Filament sensor with optical encoder.
Required parts:
- optocoupler KY-010;
- BMG roller with needle bearings;
- bearing 623;
- screw and nut M3;
- microswitch (suitable from computer mouse);
- spring (from the fountain pen);
- JST 2.54 4-pin connectors;
- screws.
Before printing an encoder ring from opaque filament (I used white), it is desirable to cover a segment of the filament (~ 10 cm) with a black marker.