Types of programming languages in PLC

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There are 5 programming languages associated with PLC, ladder diagram, functional block diagram, sequential function chart, instruction list and structured test.

Ladder diagram:

A graphical depiction of a process with rungs of logic, similar to the relay ladder logic schemes that were replaced by PLCs.

Ladder diagram language is the most commonly used PLC language and is designed to mimic relay logic

The ladder diagram closely resembles hardware relay circuits.

A sample program is shown above and it’s description as well.

Functional block diagram

A graphical depiction of a process flow using simple and complex1 interconnecting blocks.

Functional block diagram programming uses instructions that are programmed as blocks wired together on screen to accomplish certain functions.

The functional block diagram is similar in layout to the electrical block diagram.

A simple AND logic is shown in the above diagram

Sequential function chart

Sequential function chart programming language is similar to a flowchart of the process.

SFC programming is designed to accommodate the programming of more advanced processes.Structured text uses statements to define what to execute

The above shown is a sequential function chart of which ladder diagram is shown below.


Comparison between PLC and PC (Personal computer)
What are the applications of PLC?