Problem Description
Different objects are moving on a conveyor belt. Let’s say, circular balls, square blocks and rectangular
blocks. All three types of objects are collected in the same sized box. As these types are different in size
and shapes as well, number of objects to be placed are different for each type. Set counter value
according to different sized objects’ detection. Implement automation of this in PLC using Ladder Diagram
programming language.
Problem Diagram
Diagram
showing
counting
process
of
different
objects
Problem Solution
Use three different proximity switches to detect all three different objects.
Mount these switches such that switches detect assigned object only. For example, mount Square detector
proximity such that it neither detects Rectangular blocks nor Balls.
Load counter values in registers for different objects. And load this value as soon as a particular type of
object is detected.
PLC Program
Here is PLC program to Change Preset Value of Counter According to Various Products, along with
program explanation and run time test cases.
List of Inputs and Outputs
I:1/14 = Start
(Input)
I:1/15 = Stop
(Input)
O:2/0
= Master Coil
(Output)
O:2/1
= Conveyor motor
(Output)
I:1/0
= Square block detector (Proximity)
(Input)
I:1/1
= Ball detector Proximity
(Input)
I:1/2
= Rectangle block detector Proximity
(Input)
MOV
= To move corresponding source value to counter preset
(Logical)
CTU
= Up Counter to count the number of objects
(Counter)
-(RES)- = To reset counter accumulator value
(Reset)
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