16 basic knowledge about PLC

Detail

A PLC is a ruggedized computer used for industrial automation. They control machinery on factory assembly lines, amusement rides, or even the lighting fixtures. Think of them as the orchestrators of the industrial symphony.

PLCs were invented in the late 1960s for General Motors. They needed a solution to replace the cumbersome relay-based control systems in their automotive plants. And voilà, the PLC was born!

A typical PLC comprises a power supply, a CPU (the brain), input/output (I/O) modules, and communication interfaces. These components work together smoothly to control complex processes.

The Central Processing Unit (CPU) is the heart of the PLC. It processes inputs, executes control programs stored in its memory, and sends commands to the outputs. It's like the conductor of an orchestra, ensuring everything plays in harmony.

PLCs use two primary types of memory: RAM (for temporary storage) and ROM (for permanent storage). RAM is like a whiteboard where data can be written and erased, while ROM is more like a stone tablet with permanent inscriptions.

PLCs are programmed using languages standardized under the IEC 61131-3 standard. Common languages include Ladder Logic, Structured Text, Function Block Diagram, Instruction List, and Sequential Function Charts. Think of these as the dialects that PLCs understand.

Ladder Logic is the most popular PLC programming language. It's graphical and resembles electrical relay logic diagrams, making it intuitive for electricians and engineers. Imagine drawing a flowchart to control a machine, and you’ve got the gist of it.