Comprehensive Guide to PLCs: Understanding Programmable Logic Controllers

September 3, 2019

Comprehensive Guide to PLCs: Understanding Programmable Logic Controllers

What is a PLC – How does it work – Main PLC components – Top 3 PLC programming software,…All you need to know about PLC will have in this article.

The evolution of the human race has not been without quite a number of inventions. Whether to make life simpler, work easier or get results faster, several machines, devices and gadgets have been invented over time.

The thing with inventions is this, so many devices (micro and macro) are usually utilized. One central to almost every machine, gadget being used today is the programmable logic controller (PLC)

Despite how widely used it is across different industries, there’s still a mystery about PLC and PLC programming. If you have been wondering, this article will help you to understand PLC and PLC programming.

What is PLC in electrical terms?

PLC (full form: Programmable Logic Controllers) in electrical terms can be described in a number of words. Some say it’s a device that modifies the operation of a control system. It has also been described as a digital computer which is designed to perform control functions.

All the above definitions are right. PLC is a system which constantly monitors input devices in order to make decisions based on a customized PLC programming in order to control the state of output devices of a machinery.

What are the 5 main components of a PLC?

As a micro-computer, a PLC can only fully operate when all its components are in place. For the PLC programming to operate effectively, a basic PLC system must have the following:

Processor
Rack/Mounting
Input Assembly
Output Assembly
Power Supply
Programming Device/Unit

Learn more about the components of PLC

How does PLC programming work?

The PLC programming is the control logic or technique with which the PLC operates.

For any machinery, their input devices accept signals which are sent to the PLC through the connector rails. These signals are then stored in locations known as bits in the PLC memory.

The PLC programming device is the one on which program is written. The CPU then takes the instructions from the memory and processes, an operation which is used to control the output devices.

What is PLC programming used for?

Referred to as special computers, PLCs operate with the aid of PLC programming and are often used to control sensors and monitors. Thanks is just one of their uses. Others include

They are used in industries that utilize control-systems since they can operate on their own once programmed
They are used to build systems in some industries
You can also find them being used in your washing machines and also for traffic lights
What are the 5 main PLC programming languages?

The PLC is a complex device which major industries depend on for the smooth running of their plants, factories, etc. This is because of its controlling capabilities that are very reliable and its easy-to-use hardware.

That said, no PLC can function effectively without PLC programming. And no PLC programming can be effective without PLC programming languages. Let’s quickly take a look at the 4 main PLC programming languages in use today:

Sequential Flow Chart: This type of programming involves the use of symbols to represent instructions. It has been referred to as the simplest form of programming which uses only logic decisions. When it comes to this type of PLC programming language, a number of symbols can mean various things like terminator, connector, input/output etc.
Ladder Logic: This is the most important part of PLC programming. Because of its importance, it includes a number of terminologies which needs to be known in order to know how it operates. One of those terminologies is ‘Rung.’ It is the basic statement in this PLC programming language. Others include: Y- Normal Output signals, M – Motor symbol, T – Timer, and C – Counter. This is the most commonly used language across all PLCs
Structured Text: In this PLC programming (also referred to as ST or STX), the set out instructions are in a statement lists. This type of programming is only available on few brands of PLCs. What’s more? This type of programming is the most flexible for any user. However, they are not as easy to follow as ladder diagrams or logic symbols. The latest programming style is called in-lone structure text which is a hybrid between ladder and structured text
Mnemonics (Instruction Lists): These are instructions written in symbolic form. It takes up less memory than the other PLC programming languages. They are also referred to as Opcode and they are used in handheld programming devices. Just like other programming languages, different symbols are used, some of which are:For Omron, Input = I, Output = Q, Internal relay = W, Timer = T, Counter = C.
Function Block: This programming language uses a graphical language for PLC. It is also very popular because it is an easy way to write programs like Ladder Diagram. They can be easily identified by boxes which consists of a number of lines of code

We understand that this may be a bit difficult to grasp, especially if you’re new to PLCs. Not to worry. Click here to find out more about PLC, PLC programming and much more. You’ll also find engineers who will help you with all the technical aspects of PLC.

Top 3 PLC programming software

There are a number of softwares that are used for PLC programming in the world today. This article will touch on two of them.

Sysmac: This software combines configuration, programming, simulation, and monitoring in what has been described as a simple interface. Sysmac is very popular and widely regarded because it enables users and engineers to manage all necessities for a machinery, including safety and control in a system
CX Programmer: This type of PLC programming software is one that works well with most Place around today. It comes completely integrated in what is known as the CX-One software suite. For users who want speedy PLC development, this is the software to use