Automatic Door Open Close System PLC Ladder Program - Example No 4

Automatic Door Open Close System PLC Ladder Program 

PLC Ladder Practice Problem:

• When someone enters the infrared sensing field, opening motor starts working to open the door automatically till the door touches the opening limit switch 
• If the door touches the opening limit switch for 7 sec and nobody enters the sensing field, the closing motor starts working to close the door automatically till the closing limit switch touched together.
• Stop the closing action immediately if someone enters the sensing field during the door closing process.

Number of PLC Inputs Required 

X0 - X0 = ON when someone enters the sensing field.

X1 - Closing limit switch. X1 = ON when 2 switches touched together.

X2 - Opening limit switch. X2 = ON when the door touched the switches. 

Number of PLC Outputs Required 

Y0 -Opening motor

Y1 - Closing motor  

Number of PLC Timers Required 

T0 - 7 sec timer. Time base: 100ms 

Number of PLC internal memory flag Required

M1013 - 1s clock 

PLC Ladder Programming:

PLC Ladder Programming Description: 

•  X0 = ON if someone enters the sensing field of the infrared sensor. Y0 will be ON and latched, and the door will be opened as long as the opening limit switches X2 = OFF. 
• When the door touches the opening limit switches, X2 = ON. The timer T0 will start to count for 7 sec if no one enters the sensing field (X0 = OFF). After 7 sec., Y1 will be ON and latched and the door will be closed.

• During the closing process, X0 = ON if someone enters the sensing field. The NC contact X0 will be activated to turn Y1 off. Because X0 = ON, X2 = OFF and Y1 = OFF, Y0 will be ON and the door will be opened once again.