PLC - Programmable Logic controller

PLC - Programmable logic controller Basics | Instrumentation blog

Chemical, Pharmaceutical industries, Petrochemical industries, and every small to big scale company has automation now a days.

PLC means Programmable logic controller. It is registered trademark of Rockwell automation and Allen Bradley Hardware company

PLC is used in small batch process plants. Its reason because it has small memory and high speed.

DCS is used in large continuous process plant. Its reason it has Good memory and can handle larger numbers of Instruments simultaneously.

This blog contains questions

1. Why PLC [Programmable logic controller]

2. Component of PLC.

3. Flowchart of PLC.

Interview Questions

1. DCS [Distributed Control system] is available now a days then why PLC is still used in Industries?

2. What is component of PLC?

3. What is working flowchart of PLC?

1. Why PLC [Programmable logic controller] in small batch process plant?

1. PLC is Economic and user-friendly operation.

2. PLC is not need hard wired relay logic.

3. Fast operation in small scale batch operation

2. Component of PLC.

Basic Components of PLC [& DCS]

1. IO Module, Cards
2. CPU
3. Programming Device for operation
4. Memory
5. Power supply

1. IO Module, Cards

IO module means Input Output module.

• Inputs are Pressure, Temperature, Flow, pH, Level Transmitters
• Outputs are Motor, Solenoid, Heaters, Lamp or any others Which controls Valves, Motors, Lighting accessories. 

2. CPU -Central Processing Unit.

This is brain of Automation. It contains Input signals which control output signal based on Controlling programs.

3. Programming Device for operation

This is a device which used for plant or machine operation. This is Computer or Panel screen. Sometimes Laptops or Tablets also used.

4. Memory

Memory divided in two categories. We will see example of Android mobile.

1. Data memory

• In android phone You get 64GB, 128GB, etc this is Data memory

2. Program memory

• In 64GB Phone you get 50GB memory. Your 14GB is android Program Memory.

5. Power supply

For Operation of PLC panel or Computer and IO Card it requires various rating power.

3. Flowchart of PLC

• Input devices like PT FT LT send Electricity [4mA -20mA] to IO Module which convert AI [Analog input] to Digital DI [Digital Input].

• IO Module sending digital data to CPU which interfered by Operational person.

• CPU sending data to according to Parameter adjusted set point by Operational person.

• Again, IO Module convert DO [Digital output] To AO [Analog output] to Field Input devices

PLC - Programmable logic controller Advanced | Instrumentation blog

Thanks for reading - PLC - Programmable logic controller Basics | Instrumentation blog