What is PLC?: Meaning, Uses, Elements, & More

The global PLC market size was valued at approximately US $14.6 billion in 2022 and is expected to increase by US $3289.73 million between 2022-2027. This surge shows the increasing demand for PLCs across various industries worldwide. It also indicates a possible opportunity for engineers and technicians who wish to specialize in this field of automation technology. In order to understand what is PLC and how PLCs work, it’s important to have an understanding of their types and components. In this blog, we will discuss the same. So, let’s begin.

What is PLC: An Overview 

PLC is an industrial computer used to automate electromechanical processes in the manufacturing and production industries. It monitors input signals from sensors or switches and decides what action should be taken based on certain conditions programmed into it. Then, it controls outputs, such as actuators that turn devices off/on or move them up/down. Additionally, a PLC can be used for device monitoring and reporting purposes by transferring data between machines located at different sites. 

Now that we know what PLC meaning is, let’s take a look at some of its different kinds in detail.

Types of Programmable Logic Controllers

When it comes to PLCs, there are different types that empower industries with efficient automation and control solutions. 

1. PLC Types Based on Sizes 

PLCs come in various sizes, each with its own set of features and capabilities that make them suitable for different tasks. Smaller PLCs are ideal for controlling smaller machinery since they provide basic functionalities while not consuming too much memory or demanding numerous communication ports. Medium-sized PLCs feature more input/output devices, greater programmable data storage capacity as well as extended connectivity to larger systems, which allows them to be used efficiently when taking care of bigger machines. 

Lastly, large PLC units can handle very intricate machinery due to their extremely expansive characteristics, such as plentiful memories combined with advanced communication choices. This makes them a perfect fit anywhere complex automation is required.  

To learn more about PLC basics and their types, consider opting for a PLC programming course.

2. PLC Types Based on Hardware Setup

There are two main types of PLCs based on hardware setup: compact and modular. Compact PLCs feature microprocessors, built-in programming languages, user-friendly instructions, inputs/outputs (I/Os), power supplies, and connectors. They are designed for smaller automation tasks. 

Modular PLCs use programmable components instead of fixed controllers which enable them to provide greater flexibility than their compact counterparts. They also provide cost savings with installation and configuration as well as the ability to easily upgrade or replace parts, if necessary.

3. PLC Types Based on Power Supply

PLCs are separated into two kinds based on their power supply: those with built-in DC voltage and those without. PLCs that come with an inbuilt direct current (DC) like 24V or 48V do not require a separate energy source, such as batteries.

On the other hand, PLCs without built-in DC voltage are required to be connected to some kind of external provider to make sure they work properly. The internally equipped models tend to be more efficient as they take up less space than other types.

What is PLC Used For? 

PLCs are used in many industries to control and automate various types of machinery or process operations. They can be programmed to perform a variety of tasks, such as: 

For Power Supply

The power supply is a major advantage of PLC. It takes in alternating current (AC) electricity with varying frequencies ranging from 50 to 60 Hz and voltages between 110 V and 220 V. Through a step-down transformer, this AC voltage is converted into direct current (DC). This transformation ensures that industrial machines get the exact amount of energy needed for their smooth operation. Also, DC regulation by the power supply control unit produces stable outputs in case of fluctuations in input AC voltage. 

Processing 

Processing takes in data, compares it to stored information, and makes decisions based on that comparison. For example, if there is an excessive amount of pressure inside a tank, the controller might receive this reading and compare it with other pieces of saved data telling it to release some steam from the teapot as necessary.

Input 

The PLC is connected to a range of sensors and devices known as input modules. These input modules are designed to detect potential dangers within the system they’re monitoring, such as excessively high or low temperatures; water levels that fall outside acceptable parameters; and excessive pressure inside tanks. They provide an early warning if something goes wrong in order for corrective measures to be taken quickly before any major damage occurs.

Output 

A programmable logic device is capable of sending out signals that can be experienced by the external environment. Typical examples include a flashing light at an intersection to indicate when it’s safe for vehicles and pedestrians to cross, activating alarms such as burglar alarms or fire sirens to alert people about danger, controlling speed via motors in appliances like window blinds or automated doors, and temperature controls through thermostat systems.

Programming Device 

In order to troubleshoot, modify and program a PLC, several devices can be used. Such programming terminal components are PCs or handheld-based items that connect through cables to the PLC device itself. Handheld tools often have buttons that make it possible for you to dump, edit and enter code as well as display any instructions being coded at the time on a small LCD screen. The outputs and inputs of this type of system give information such as temperature regulation when running processes in addition to measures like productivity levels.

Also Read: PLC Programming For Beginners

Elements of PLC

A PLC has two main components: a CPU (Central Processing Unit) and an I/O (Input/Output) system. Let’s look at each of these components in detail.

Central Processing Unit (CPU)

CPU, often referred to as the “brain” of a PLC, retrieves and decodes information from its memory system before processing it further in accordance with instructions derived from an internal control program. It has three distinct components: 

• A processor for coding, decoding, and computing.
• An integrated memory that stores both the control program details and parameters related to connected equipment.
• A power supply unit which is responsible for providing electric current at necessary voltage levels.

Input/Output (I/O) System 

The I/O system of a PLC can be compared to its arms and legs since it carries out the instructions given by the CPU. The system is divided into two parts: an I/O rack with slots that hold modules and individual devices sorted as either inputs or outputs which have connection terminals for external instruments.

Inputs bring signals and information from outside sources, such as push buttons or switches while outputs await commands originating within the PLC to control activities like lighting, sounding horns, and activation of motors or valves. 

Conclusion

In this blog, we answered what is PLC or a Programmable Logic Controller. PLCs are widely used in manufacturing and production settings and play a vital role by providing automated solutions to power supply control, input monitoring, output regulation, and programming tasks. They come with powerful CPUs that can read instructions as well as I/O systems for connecting them with external devices of different sizes or setups.