For managing the manufacturing process there was the use of relays by the industries. It is said that there should be regular replacement of the relay control panels as there is excessive consumption of power and it is difficult to identify problems associated with it.

Define PLC?

For the automation of various electro-mechanical processes in industries, a digital computer like Programmable Logic Controller (PLC) is used. For dealing through tough times it has been designed in such a way shielded from cold, heat, dust, and moisture etc. It is programed using the computer language and is made up of micro-processor.

The program is downloaded to the PLC with the help of a cable and the code is written in the computer system. If you consider the non-volatile memory of the PLC you will find all the loaded programs stored over here.

PLC Hardware

The physical elements or the hardware of a PLC system are CPU, Memory, Input/Output, Power supply unit, and development system.


1. CPU – For avoiding errors, one should always keep checking the PLC controller. They can operate functions like the logic operations, computer interface, arithmetic operations, etc.

2. Memory – CPU uses fixed data. Operating System gets the permanently stored data by the System (ROM). RAM is used for storing information of the status of input and outcome devices, and internal devices, timers, and counters.

3. I/O area – For getting to know about the receptors input devices are used.

4. O/P Section – For devices such as motors, pumps, lights and solenoids, output devices has the control. The I/O slots are based on Reduced Instruction Set Computer (RISC).

5. Power supply – There are some PLCs working at 220VAC or 24VDC whereas certain PLCs have an isolated power supply.

6. Programming system – For feeding the program into the memory of the processor this programing system is used. It is initially fed to the programming device and later transmitted to the PLC’ s memory.

7. System Buses – Most of the internal signal flows through the buses in PLC.

· CPU uses it tor transfer data for different purposes.

· For controlling certain actions internally, control buses are used for           transferring signals

· For transferring the location’s address, address bus is used.

· I/O port and I/O unit communicates with each other with the help of           system bus.

For more information join the electrical design course in Pune to make your profession as electrical engineers in this field.

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