Modern industrial automation systems are smarter and more advanced than ever before. But have you ever wondered how did they get this way? What gives them the power and capability? What drives them? The answer is the PLC.
So now the questions are ‘What does PLC stand for?’;‘What does a PLC do?’ Read on for a detailed introduction to PLCs.
First let’s learn the PLC full form. PLC stands for Programmable Logic Controller. According to Wikipedia, “A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity that requires high reliability, ease of programming, and process fault diagnosis.”
The PLC or Programmable Logic Controller is the heart and brain of industrial automation.It is a specialised computer control unit that continuously monitors the internal components and gets them to function together as a seamless, coordinated unit.
The PLC control system automatically controls the different processes, devices and components in an industrial system, and makes decisions based on a custom programme.
PLCs come in different sizes and shapes. Some can fit easily in your palm or pocket, some others need to be mounted on heavy-duty racks. They are used in a variety of applications and industries as they are fast, easy to operate and generally easy to programme.
The PLC design contains some basic hardware, with each adding its own function to the PLC. The components of PLC system are:
PLC Input and Output (I/O) section functions as the sensing organs. All field devices are connected to this section. PLC input devices receive incoming signals from external sensors such as pressure or proximity switches, converts them to low-voltage digital hints before sending them to the processor.
The output section receives the low-voltage digital signals from the processing unit and converts them into high-power hints. These high-voltage signals from the output section drive the industrial functions such as lighting, rotation, heating, movement, etc.
All PLCs operate as per the following steps:
There are different types of plc programming languages but the most common programming language for PLCs is Ladder Logic. A PLC program is usually written on a computer and then downloaded to the PLC control unit.
Ladder Logic mimics control circuit schematics with ‘rungs’ of logic read left to right. Each rung represents a specific action controlled by the PLC, starting with an input or series of inputs that result in an output (coil).
Logic programming software can be easier to implement than many other programming languages because of its visual nature. The intuitive interface of ladder logic made the transition from relay logic to PLC device much simpler for many in the industry.
‘C’ programming is a more recent innovation; some PLC manufacturers provide control programming software.
In terms of physical hardware, there are two types of PLC: Compact/Fixed PLC and Modular PLC.
In compact PLCs, the power supply, CPU and communication card are contained within a single case. Compact PLCs have a fixed numberof Input/Output modules.
Modular PLCs, as the name suggests, consist of various modules and easily expanded Input and Output modules which are fitted in the rack. That’s why,this type it is also known as‘rack mounted PLC’.
As industrial automation & control systems continue to advance, growing in function and sophistication, PLCs too will have to evolve to keep pace. To build a future-ready system with best-in-class PLCs and automation system components, contactMessung, pioneer and leading PLC manufacturer in India.
Messung was founded in 1981 when the founder began developing a prototype PLC in a humble garage. By 1984, India’s firstindigenous 1-bit processor-based PLC was launched – and went on to transform industry, replacing the traditional relay contactor logic.
Since then, it’s been one continuous journey of innovation and excellence in industrial automation.
Messung’s programmable controllers, Remote I/Os, HMIs and SCADA solutions have enabled industries, OEMs and automation system integrators achieve top-of-the-line performance and efficiencies. Messung’s rugged, IoT-enabled industrial controllers are gamechangers with their inbuilt I/O, integrated HMI panels and advanced features while Messung’s Process Automation, Servo & Motion Control Automation, and General Purpose Automation solutions have proven themselves across the gamut of industries with their flexibility, efficiency and long service life.
Messung Industrial Automation & Control division also offers PLC panels for remote control, SCADA applications, VFD drives and servo drives.