What PLC Can Do

Relay Sequences Control

Though the word “sequence control” may generally be unfamiliar to us, it is used very often around us, and everyone is likely to have seen or have had contact with something that is controlled by sequence control. of sequence control

1. When the operation switch is closed, the float switch limit switch 1 closes if the tank is empty, and the magnet switch MC is operated to drive the transfer pump motor. Relay MC is designed to hold its own state even if the water level is at the mid position.
2. When the tank becomes full, float switch limit switch 2 opens, hold operation of the relay MC is canceled, and the transfer pump motor stops.
3. When the water level reaches the empty level, the motor starts to operate automatically again.

With motor operation in this control example, the motor starts to operate at the mid position after an empty tank is detected. Motor operation stops at the mid position after a full tank is detected, and the motor operating state differs even at the mid position.