Introduction to Plc (Programmable logic controllers), Working, Types & Applications

Hello friends, I hope all of you are doing great. In today’s tutorial, we are going to have a look at the introduction to PLCs (programmable logic controllers). Programmable logic controllers (PLCs) are a new invention for our industries.  After its creation, our working in industries and controlling different devices has become very easy. It replaced the wired relay system, which was very complicated and difficult to handle. There are many controlling systems that exist, but PLC importance can’t be denied. For different automation procedures, a PLC is the best choice of controller. Nowadays it integrates minor circuitry, faster CPUs, network systems, and numerous pieces of Internet equipment.

PLCs have become the most popular instrument for industries to control different processes that are performed in the industry. It is an industrial-type computer that is programmable for controlling functions. Due to its programmable capability, the wiring control system has been removed from industries like relay control. The main advantage is its programming language is very simple; there is no need to use specific tools like other computer languages such as C, C++, etc. In the coming tutorial, we also learn about its programming language and its working. So let’s get started with an introduction to PLCs.

Introduction to PLCs (Programmable Logic Controllers)

• Programmable logic controllers (PLCs) are a new development for our industries. After its creation, our working in industries and controlling different devices has become very easy.

• It was intended for numerous input and output arrangements, higher temperature ranges, resistance to electrical sound, and opposition to pulsation and its effect.

• Programs for the controller and process of industrial apparatus and equipment are typically stored in battery-supported or non-volatile storage.

• A PLC is like an actual system because the output of any process that is under control of a PLC depends on the inputs.

• From this, we can say that a PLC is generally a digital computer that is built for controlling the machine.

• Different from our personal computer, it is prepared according to industry working situations, and it consists of special inputs and outputs and its special programming language.

• At its creation time, it was considered the replacement of a relay, but due to many functional capabilities, it started working in numerous complicated industrial submissions.

• As its construction is the same as that of a computer, it has the ability to work not only for relays switching but also to perform many applications, like time calculation, counting, comparison, and processing of different analog signals.

• PLCs have numerous benefits over a conservative relay using control. A relay uses much wiring, but a PLC avoids a wiring system, and a relay can be used only for a single or specific function, but a PLC performs many functions.

• In case of a relay in automobile industries, we have to change all wiring of the control process, which makes its use expensive, but a PLC has removed these wiring systems.

• It is small and cheap compared to corresponding relay-centered procedure controller schemes.

Benefits of PLC

Reliability of PLC:

• When one program is typed and implemented by a PLC, it can easily be used for other PLC devices. Because this program has been easily saved in PLC memory.

• All the logic programs are stored in the memory storage of the PLC, so there is a minor chance to damage this program.

• The program has taken the place of abundant exterior cabling that would usually be obligatory for a controller of different processes in industries.

• PLCs also offer reliability related to solid-state elements like electronic components.

Flexibility of PLC

• It is very easy to make any program and change it in a PLC, while in a relay system it’s very difficult to connect a wire and disconnect it.

• The working of inputs and outputs is defined by the program, not their connection defining their working.

• If there is a need to update the system, just change our program, which is updated, not all connections of our system

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Lower-Cost PLC

• PLCs were initially manufactured to substitute relays, and the lower price has been so important that relay controllers are becoming outdated except for power applications.

• Normally, if any system has more than around a half-dozen relays in circuits, it will maybe be less costly to use a PLC.

• From the figure, we can see that there is a lot of wire in relay circuits, but in PLCs, few are used, which makes them cost-effective.

Communications Capability of PLC

• The PLC has the ability to communicate with other plc controllers or computer devices to work as a supervisory component, to get data, to monitor other controllers and for sending and receiving of different programs.
• In the given diagram plc communication module is shown.

Faster Response Time of PLC

• PLCs can work with circuitry that requires high-speed operation.
• The programmable controller works in real time, which means that any operation will show its output at a given time.
• Types of machinery that work on thousands of substances per second and matters that apply only a portion of a second in obverse of an instrument need the PLC’s rapid response capability.

Easier to Troubleshoot PLC

• A PLC consists of a function that permits the user to detect and resolve problems in the program or any circuit.

• After solving problems and finding them, we can easily show it on a monitor. The given diagram shows this process.

PLC Size

• The standards used for categorizing the PLC are its function, how many inputs and outputs it has, its price, and the main thing is its structure size.

• One of the most important factors, which is countable, is its input and outputs.

• Its smallest module, which is known as “Nano,” consists of 15 input and output points.

• Larger than this, the Nano is a micro-size that has 15 to 128 input and output pinouts.

• Greater than micro-size, there is a medium-size PLC available, which is known as 128 to 512 input and output pinouts.

• The larger size in which it exists consists of more than 512 input and output pinouts.

• Different sizes of PLCs are shown in the given diagram.

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Applications of PLC

• There are a lot of applications of PLCs, but three important applications are described below.

  • Single-ended

  • Multitask

  • Control management.

Let’s discuss them one by one with a detailed description.

Single-Ended PLC Application   

• A single-ended PLC submission contains one PLC controller to control and monitor a single process.

• It will be a single unit and cannot be used for communication with other processors or PLCs.

• The dimension and complexity of the procedure, which is measured, are noticeable aspects in determining which PLC to choose.

• The applications can ask for a bulky CPU, but generally, this class needs a smaller PLC.

• The diagram shows the single-ended applications of plc.

Multitask PLC Application

• In multitasking applications of a PLC, one PLC controller monitors many procedures at the same time.

• Acceptable input and output capability are important aspects in this category of applications.

• If the PLC is a subsystem of a bigger procedure or process and will have to connect with a central PLC or processor, then there will be a need for a large system of communication.

Control Management PLC Applications

• We discussed in multitasking applications that one plc controls many processes. But in the case of Control Management Plc., one PLC controls many other PLC devices.

• This type of system needs a larger PLC CPU manufactured to connect with other PLC controllers and possibly with a processor.

• The control management PLC administers numerous PLC processors by taking (downloading) programs that give instructions to other PLC processors on what they will have to do.

• It should have the ability to make connections with other processors so that, by appropriate instructions, it can connect with anyone it desires to.

Memory of PLC

• Memory is the portion of a programmable logic controller that gathers statistics, commands, and controlling programs.

• The space or size of storage of a PLC is normally denoted as “K,” like “1k,” “2k,” etc.

• The (K) is an abbreviation of “kilo”; usually it denotes 1000 units.

• But in the case of computers and programmable logic controllers, one (k) is equal to 1024, since these calculations are based on the binary numeral system.

• According to the memory category, one (K) can be denoted as (1024 bits), (1024 bytes), or (1024 words).

• While it is general for us to calculate the storage capability of a PLC in words, we are required to see the number of bits in every word before the storage dimension can be precisely related.

• The volume of memory needs to be designed according to the applications.

• Before the plc installation, some factors that should be in the notice are explained here.

  • Quantity of input and output connections.

  • The magnitude of the program controller.

  • Statistics gathering necessities

  • Controlling functions requisite

  • Future developments

Read also

• What is PLCC Packages | SMD Plastic Leaded Chip Carrier – How Do We Use Them?
• Difference Between Computer and PLC
• What are the Features of PLC Inputs and Outputs
• PLC Special Inputs and Outputs

 I have mentioned each and everything related to PLC if you have any questions, ask in comments. See you in the next tutorial, parts of PLC.