Create Ladder Diagram from Boolean Logic

Here you will learn how to create ladder diagram from Boolean logic and understand the basics of PLC.

Note: The PLC example shown here is for educational use only for students to understand PLC ladder diagrams.

Create Ladder Diagram

Problem Statement

Design a PLC ladder logic for the following Boolean Expression.

We are using toggle Inputs to control the output.

Find out the equivalent ladder logic for the given boolean logic.

 Y= AB+CD

Video

This video tutorial helps you to learn the creation of ladder diagram based on the given boolean expression.

Digital Inputs

The inputs listed below.

A: I0.0

B: I0.1

C: I0.2

D:I0.3

Digital Outputs

The outputs listed below.

Y: Q0.0

Boolean Logic Ladder Diagram

Program Description

• We used Schneider Electric EcoStruxure Machine Expert Basic software.
• In the above program, Normally Open Contacts are used for input A, input B, input C and input D.
• Input A and Input B are connected in series, thus implementing AND Logic Gate.
• There is again the implementation of AND Logic Gate as Input C and Input D are connected in series.
• There is also implementation of OR Logic Gate as AB and CD are connected in parallel.
• For the output Y (Q0.0) to be ON, Input A and Input B should be ON.
• Turning ON only one input i.e., either input A or input B will not turn ON the output Y (Q0.0).
• Turning ON Input C and Input D will also turn ON the output Y (Q0.0).
• If only one input i.e., either input C or input D is turned ON, then the output Y (Q0.0) will remain OFF.

Logic Result

Check the below logic output result with simulation.

When both Input A and Input B are ON

The signal will pass through Input A and Input B when turned ON. If only one input i.e., Input A or Input B is turned ON, the output Y (Q0.0) will not turn ON.

The inputs A and B are in series and are used as Normally Open Contacts. So, for the output Y (Q0.0) both the inputs i.e., input A and input B should be ON.

When both Input C and Input D are ON

When Input C and Input D are turned ON, the output Y(Q0.0) will turn ON. Input C and Input D implement AND Logic Gate as these are connected in series and are taken as Normally open Conatacts.

When both the inputs i.e., input C and input D are turned ON, then only the output Y (Q0.0) will turn ON, If only one input is turned ON i.e., only input C or input D is turned ON, the the output Y (Q0.0) will not turn ON.

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