Develop PLC Programming Example using Limit Switch according to the logic given below,
- The system is started by an operator each shift, and the item to be sorted are then fed onto the production line conveyor.
- Once the start is pressed conveyer should ON, the items proceed, operating limit switch 1, which counts all the items.
- Limit switch 2 counts only the larger items. Limit switch 3 counts only the larger items.
- As limit switch 2 is operated, a pneumatic ram 1 is activated and thus stores all the larger items in the bigger box.
- As limit switch 3 is operated, a pneumatic ram 1 is activated and thus stores all the larger items in the smaller box.
- At the end of 2 items, next bigger box output and smaller box output turns ON to shift new boxes.
- The counter automatically resets when the preset value meets the accumulator value.
- When operator press end of work, It waits for 10s to turn off conveyor motor in between any items crosses limit switch, it should count and send to respective boxes.
- The stop is pressed to stop the process at any time.
PLC Programming Limit Switch
Program Description:
Rung 0000:
Start/Stop PB latched with memory B3:0/0. Timer off delay is connected to stop conveyor motor after 10s once the end of work is pressed.
Rung 0001:
B3:0/0 enabled to turn on conveyer motor (O:0/0 ). Limit switch 1 (I:0/0) is connected to counter which counts all incoming items. Normally open contact of the timer is connected in series to stop the conveyor motor.
Rung 0002:
Limit switch 2 (I:0/1) is to count bigger items and enabling pneumatic ram 1 (O:0/1) to push bigger item to a bigger box.
Rung 0003:
Limit switch 3 (I: 0/2) is to count bigger items and enabling pneumatic ram 2 (O:0/2) to push bigger item to a bigger box.
Rung 0004:
Comparator block is used to compare counter (C5:1) with 2 to change the bigger box and to reset the counter to set to count from first.
Rung 0005:
Comparator block is used to compare counter (C5:2) with 2 to change the smaller box and to reset the counter to set to count from first.
Rung 0006:
Reset operation automatically happen, when Counter(C5:0 ) preset value reaches accumulator value,
Program Output:
When Start Pushbutton is pressed.
When Bigger product crossing limit switch 2
When smaller product crossing limit switch 3
When End of work button is pressed
Conclusion:
We can use this example to understand the programming logic in AB Programmable Logic Controllers (PLC).
Author: Hema Sundaresan
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