Tevo Tornado optical filament sensor holder

Holder for the optical filament runout sensor, e.g. https://de.aliexpress.com/item/CHANGTA-3D-printer-parts-Optical-Endstop-Light-Control-Limit-Optical-Switch-for-3D-Printers-RAMPS-1/32719651743.html

It is connected to top of the extruder and won't get in the way of other add-ons.
You need one slightly longer screw M3 x 30. The PCB sticks out, in order for you the see the LED.

Added design with a small slit. you can now use a strip of paper to make it work with transparent filament. The f