What is PLC- Block Diagram of PLC, PLC Programming
What is PLC?
A Programmable Logic Controller is an industrial digital computer which has regulate, control the industrial operations such as assembly lines, robotic devices or any other industrial process. PLC has high reliability, high accuracy, process fault diagnosis.
First PLC were developed in the automobile manufacturing industry to provide flexible, rugged and easily programmable controllers to replace hard wired relay logic systems. Since then, they have been widely adopted as high reliability automation controllers.
PLC programming language focused on logic and switching operations. It was more user friendly than computers using Ladder Logic programming languages. PLC also permitted for its operation to be monitored.
Black Diagram of PLC
1. Central Processing Unit (CPU)
CPU interprets inputs and executes the control program stored in memory and sends output signals.
2. Power Supply
Power supply unit converts AC input voltage to DC output voltage required as per rated value.
3. Memory Unit
Memory unit storing data from inputs and program to be executed by the CPU.
4. Input and Out Interface Module
Input Device module receive the signal from various sensors in digital format and sent to CPU for action to be taken.
Output device module received the signal from CPU and sent to load for controlling the application.
5. Programming Device
Programming device used for to communicate and development the program with CPU.
Programming of PLC
A graphical programming language called Ladder diagram. The fundamental concepts of PLC programming are common to all manufacturers in I/O addressing, memory organization and instruction sets mean that PLC programs are never perfectly interchangeable between different makers.
PLC programs are typically written in programming device which can take the form of a desktop console, special software on a personal computer or a handheld programming device. Then the program is downloaded to the PLC directly or over a network.
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