PLC program to execute an elevator system in a two-floor apartment using Allen Bradley PLC ladder logic programming.

In the picture given, there are totally two floors.

• There are two user panels. One is inside the lift and the other is outside the lift.
• Limit switches are used to locate and stop the lift on each floor.
• Priority is given to the first input.

Write the PLC ladder logic for the above-example.

In the picture given, there are totally two floors.

• There are two user panels. One is inside the lift and the other is outside the lift.
• Limit switches are used to locate and stop the lift on each floor.
• Priority is given to the first input.

Inputs and Outputs

Elevator PLC Program

PLC Program Description

RUNG 000

Latching rung to operate the system through Master Start and Stop PB.

RUNG 001

Starting the Operation using start latch, Ground floor PB is pushed to turn on the latch coil to store the output of status when the ground limit switch is off.

RUNG 0002

First floor PB is pushed to turn on the latch coil to store the output of status when the First limit switch is off.

Rung 0003

Second floor PB is pushed to turn on latch coil to store the output of status when Second limit switch is off.

Rung 0004-0005-0006

In some cases, if someone pressed ground floor PB/First floor PB, the program will check where the lift is if it is in the second floor or the first floor, Down Motor will turn ON to get the lift to the respective floor.

For interlocking, normally closed switch of ground limit switch and first-floor switch is used in Rung 0006

Rung 0007-0008-0009

In some cases, if someone pressed the second floor PB/First floor PB, the program will check where the lift is if it is on the ground floor or the first floor, UP Motor will turn ON to get the lift to the respective floor.

For interlocking, normally closed switch of second-floor limit switch and first-floor switch is used in Rung 0009.

RUNG 0010-0011

To open the lift door when it reaching the floor, Binary bits are used to store the status of ground floor PB and ground Limit switch.

RUNG 0012-0013

To open the lift door when it reaching the floor, Binary bits are used to store the status of First floor PB and First Limit switch.

RUNG 0014-0015

To open the lift door when it reaching the floor, Binary bits are used to store the status of Third floor PB and third-floor Limit switch

RUNG 0016

From the previous rungs memories, the Open door motor is turned ON with three interlockings like closed-door motor, Timer enables, UP/DOWN motor.

RUNG 17

When the open door limit switch is turned to on, the Open motor door should stop and timer needs to turn on to give time delay of 5s to close door motor.

RUNG 18

When timer done turned on, close door motor should ON until closed limit switch is turned ON.

RUNG 19

If no PB is turned on after getting into lift takes 10secs delay to open lift door again. If any PB is pressed, it will perform the respective operations.

The program runs continuously until STOP PB is pressed Note: We can reduce the number of memories used.

Author: Hema

Training Course: Allen Bradley PLC Course