Create PLC Program based on Logic Circuit

Learn how to create PLC program based on logic circuit to enhance your automation skills with our tutorials and videos.

Important: This PLC logic is solely for educational purposes and helps students and technicians grasp PLC fundamental concepts.

Create PLC Program

Problem Statement:

Design a PLC ladder logic for the following Logic Circuit.

We are using toggle Inputs to control the output.

PLC Tutorial Video

Watch the video to understand the PLC concepts for a beginner level.

Inputs

The list of DI signals is listed below.

A: I0.0

B: I0.1

C: I0.2

D: I0.3

Outputs

The list of DO signals is listed below.

Y: Q0.0

Ladder Diagram

PLC Program Explanation

• Here we used Schneider Electric PLC programming software. You can try any other PLC software too.
• In this PLC program, Normally Open Contacts are used for input A, input B, input  C, and input D.
• Input A and Input B are connected in parallel, thus implementing OR Logic Gate.
• There is again the implementation of OR Logic Gate as Input C and Input D are connected in parallel.
• AND Logic Gate is also implemented as  A + B is connected in series with C + D.
• For the output Y (Q0.0) to be ON, Input A or Input B and Input C or Input D should be ON.

PLC Test Results

The PLC program test results with different inputs are shown below.

When Input A and Input C are ON

The signal will flow through Input A and Input C when these Inputs are turned ON as Normally Open Contact is used. As a result, the output Y (Q0.0) will turn ON.

When Input A and Input D are ON

When  Input A and Input D are ON, Y(Q0.0) will turn ON as Normally Open Contacts used for these Inputs are in True state.

Instead of using input C, we can also use input D to turn ON the output Y (Q0.0).

When Input B and Input C are ON

The output Y (Q0.0) will turn ON when Normally Open Contacts used for Input B and Input C are in True state and will pass signal to flow.

Here, instead of using input B, we can also use input B to turn ON the output Y (Q0.0).

When Input B and Input D are ON

Turning On Input B and Input D will turn ON Y(Q0.0), as the signal will flow through Input B and Input D and will turn ON (YQ0.0).

Therefore, we can also use input B and input D to turn ON the output Y (Q0.0).

When three inputs are ON

When three inputs i.e., either input A, input B, and input C or input A, input B, and input D or input B, input C, and input D are turned ON, then the output Y (Q0.0) will turn ON.

For output Y (Q0.0) to be ON, two inputs i.e., input A and input C or input D or input B and input C or input B and input D should be ON.

Turning ON the third input will not turn OFF the output Y (Q0.0). Therefore, if any three inputs are turned ON, the output will be ON.

When all Inputs are ON

When Input A, Input B Input C, and Input D, all are turned ON, the output Y (Q0.0) will be ON. Turning ON all the inputs will not turn OFF the output Y (Q0.0).

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