Design a PLC program to execute elevator system in a 2 floor apartment using Allen Bradley PLC programming.
Elevator PLC Logic
In the above picture, there are totally two floors.
There are two user panels. One is inside the lift and other is outside the lift.
Limit switches are used to locate and stop the lift at each floor.
Priority is given to the first input.
Elevator Logic Inputs and Outputs
Elevator PLC Logic
Elevator Logic Description
RUNG 0000
Latching rung to operate the system through Master Start and Stop PB.
RUNG 0001
Starting the Operation using start latch, Ground floor PB is pushed to turn on latch coil to store the output of status when ground limit switch is off.
RUNG 0002
First floor PB is pushed to turn on latch coil to store the output of status when 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 case ,if someone pressed ground floor PB/First floor PB , program will check where the lift is, if it is in second floor or first floor, Down Motor will turn ON to get the lift to 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 case, if someone pressed second floor PB/First floor Push buttons (PB), program will check where the lift is, if it is in ground floor or first floor, UP Motor will turn ON to get the lift to 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 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 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 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, Open door motor is turned ON with three interlocking like closed door motor, Timer enable, UP/DOWN motor.
RUNG 0017
When open door limit switch is turned to on, Open motor door should stop and timer need to turn on to give time delay of 5s to close door motor.
RUNG 0018
When timer done turned on, close door motor should ON until closed limit switch is turned ON.
RUNG 0019
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.
Program runs continuously until STOP PB is pressed
Note: We can reduce the number of memories used.
Conclusion:
The above explained elevator control using PLC is for example only. It may vary from real time. There are many concepts to program elevator, this program is one of the type.