The following figure shows the actual circuit. When the button SB 1 is pressed, the coil of contactor KM 1 is energized, its main contact is closed, and the motor m is energized, driving the car to move forward from the origin. After reaching the finish line, the stop on the car touches the travel switch SQ 1, its normally closed contact is disconnected, the coil of KM 1 is powered off, the motor stops rotating, and the car stops. The normally open contact of SQ 1 is closed, and the coil of turn-on time relay KT 1 is delayed (to ensure that the car stops completely and avoid possible reverse braking of power supply). KT 1 Delay until its normally open contact is closed, the contactor KM2 coil is energized, the motor rotates reversely, and the car returns. After reaching the origin, the normally closed contact of the travel switch SQ2 is disconnected, the KM2 coil loses power, the motor stops running, and the car stops at the origin. SQ3 and SQ4 are set to prevent the trolley from losing control due to melting and sticking of the main contact of KM 1 KM2.

If the main contact may be melted and stuck, you can remove SQ3, SQ4 and KM. KT 1 can also be removed if the influence of the reverse power supply system is not considered. SQ 1 is a normally open contact (red circle contact in the figure) instead of KT 1 (another red circle).