I recently did t dual z-axis with z braces upgradeby proper printing (https://www.thingiverse.com/thing:3719799) and wanted to use a filament runout sensor

Since almost every sensor is mounted to the extruder and would limit the movement in z I decided to design my own and mount it out of the way on the z brace

I bought endstops from amazon (shorturl.at/loJP4) and designed the case around it

Additional hardware used:
4x M3x10
4x M3x12
8x M3 Nuts
Some Wire
Solder
Dupont Connectors
Shrink Wrap
PTFE Tubing

Creality

Ender 3

Doesn't Matter

Yes

0.16

25%