Filament runout sensor

To use this you need:

1 x mechanical endstop like in the picture.
I used this:
https://pl.aliexpress.com/item/1pcs-lot-High-Quality-Mechanical-Endstop-For-Reprap-ramps-1-4-3D-printer-With-independent-packing/32622912889.html?spm=a2g0s.9042311.0.0.OzYORn
2 x m3 screws

The sensor is connected to the X+ endstop. You need to enable the filament ronout sensor option in your firmware and select the right pin for it.