Ender 3 Auto stop

A simple auto stop.
A simple transmitter and receiver are all that is needed.
The transmitter is Affected by the extruder in the X max position.
And you also need somthing like this in your printer settings end gcode..
G1 F100 X220; slowly towards the transmitter.
The value F100 is the speed, it is set so that the extruder has time to cool off.

G1 F1000 Z250; goto maximum height
G1 F1000 X0; x to max home
G1 F100 X220; slowly towards the transmitter.
G1 F300 X218; reverse a bit.