PLC Based System..

What is a PLC?

PLC stands for “Programmable Logic Controller”. In the most basic terms, a programmable logic controller (PLC) is a computer with a microprocessor but has no keyboard, mouse, or monitor. It is essentially built to withstand very harsh industrial environments.

PLCs share many features of the personal computer you have at home. They both have a power supply, a CPU , inputs and outputs (I/O), memory, and operating software (although it’s a different operating software).

How Does a PLC work?

The working of a programmable logic controller can be easily understood as a cyclic scanning method known as the scan cycle.

A PLC Scan Process includes the following steps

• The operating system starts cycling and monitoring of time.
• The CPU starts reading the data from the input module and checks the status of all the inputs.
• The CPU starts executing the user or application program written in relay-ladder logic or any other PLC-programming language.
• Next, the CPU performs all the internal diagnosis and communication tasks.
• According to the program results, it writes the data into the output module so that all outputs are updated.
• This process continues as long as the PLC is in run mode.

Applications of Programmable Logic Controller (PLC)

The PLC can be used in industrial departments of all the developed countries in industries like chemical industry, automobile industry, steel industry and electricity industry. Based on the development of all these technologies, functionality and application, the scope of the PLC increases dramatically.

1. Application of PLC in Glass Industry:

From the year 1980 the Programmable-logic controllers are in use in the glass industry, and they are assembled bit by bit. PLCs are used mainly in every procedure and workshop for controlling the material ratio, processing of flat glasses, etc.

With the development of PLC and increasing demand in the real world, the control mode of the programmable-logic controller with an intelligent device is applied in the glass industry. In making of a float glass, PLC itself cannot finish some controlling tasks because of the complexity of the control system and processing of huge data. For the production of glass, we make use of bus technology to construct the control mode of a PLC with a distributed-control system. This control system deals with analog controlling and data recording; the PLC is also used for digital quality control and position control.

This type of control mode is a big advantage for PLC and DCS for improving reliability and flexibility of the control system.

2. Applications of PLC in Cement Industry:

Along with the best-quality raw materials, the accurate data regarding process variables, especially during mixing processes within the kiln, ensures that the output provided should be of the best possible quality. Nowadays a DCS with bus technology is used in the production and management industry. By using this existing DCS control system, the PLC is in user mode of SCADA. This mode comprises PLC and configuration software. This SCADA mode comprises the PLC and host computer. The host computer consists of slave and master station. The PLC is used for controlling the ball milling, shaft kiln and Kiln of coal.

To know more about these programmable-logic controllers’ function, you can go through the following project, which is given as a practical example used mostly for industrial automation.

Thus, this article has covered the principle of operation of programmable logic devices or controller and its applications in various industries like glass industry, steel industry and cement industry.

 Advantages of PLC :

1. A PLC performs only a single set or sequence of tasks, with greater reliability and performance, except when it is under real-time constraints

 

2. The PLC has several features that you don’t find in normal computers, such as protection from the open area conditions like heat, dust and cold.

 

3. It is low cost compared with other microcontroller systems. When you’re using a PLC in various applications, you only need to change the software component for each application.