Siemens S7-200 PLC's Belt conveyor Control Programming Example

Three conveyor belts, respectively, by the motor M1, M2, M3 driven.

Requirements: After pressing the start button SB1, a startup sequence for M1, M2, M3, interval of 3s.
After the stop button SB2, Sequential stopping for M3, M2, M1, interval of 3s.
Three motors M1, M2, M3, respectively, through the contactor KM1, KM2, KM3 three-phase AC power supply is turned on, PLC control coil contactor