Advantages and Disadvantages of Programmable Logic Controllers

Overview

The programmable logic controller (PLC) is a small electronics computer which is used in the industry and factory for the purpose of controlling machine. The operation principle of this programmable logic controller is, it is mainly checked and monitors the input device and makes decisions and produces output based on a custom program. That custom program actually programmed by the user. In use, there are some advantages and disadvantages of programmable logic controllers too. We are going to discuss and want to know the advantages and disadvantages of a programmable logic controller in this article.

What is PLC?

PLC is one kind of electronic device, which is mostly used in the industry and factory for the purpose of controlling the machine. It is an industrial solid-state computer that checks inputs and outputs device, and make decisions based on logics for automated processes or machines.

PLCs are powerful and can endure cruel conditions including serious warmth, cold, residue, and extraordinary dampness. Their programming language is effortlessly seen, so they can be modified absent a lot of trouble. PLCs are particular so they can be connected to different setups. Relays exchanging under burden can cause undesired arcing between contacts. Arcing creates high temperatures that weld contacts shut and cause corruption of the contacts in the relays, bringing about device disappointment. Supplanting relays with PLCs forestalls overheating of contacts.PLCs were initiated in the later 1960s by Richard Morley to provide the same functions as relay logic systems. Relay systems at the time would, in general, come up short and make delays. Experts at that point needed to investigate a whole mass of relays to fix the issue.

Basic Components of a PLC

A programmable logic controller is made out of a couple of fundamental parts. These include a power supply; a focal handling unit, or CPU; input/output cards; and a backplane, bearer, or rack that these parts are set into. The backplane makes an electrical connection include between the entireties of the different parts, giving the PLC its particular plan. This electrical connection includes both power and correspondence signals. Numerous PLC products utilize exclusive correspondence conventions on the backplane with the goal that I/O can safely converse with the CPU.

The Power Supply

The power supply gives either 125V AC or 24V DC relying upon the application and the conditions of the establishment. As referenced over, this voltage is transported down the backplane giving power to the CPU and I / O modules, which come as “cards”. These cards can rapidly be included or expelled from their space in the transporter.

The Programming Device and Human-Machine Interface

Outside of the PLC itself are two significant parts: The programming devices and the human-machine interface (HMI). The programming device can be a personal computer, PC, or hand-held instrument from a similar producer. There are also fixed I/O PLCs with worked in showcases and catches that permit projects to be composed straightforwardly on the PLC.

While the programming device permits the client to see and modify the code running on the PLC, the HMI gives a more significant level of deliberation, displaying the control framework in general. A coordinated touch screen that, it can be utilized in the control room or out in the field closer to the procedure. These sorts of intuitive presentations are normal and will frequently be mounted legitimately on the PLC fenced-in area of closer by for administrator use.

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How Does a PLC Operate?

In the operation of all PLCs, there are four basic steps. Input Scan, Program Scan, Output Scan, and Housekeeping. These steps continuously take place until the user interferes with them.

Input Scan: it assists in the programmable logic controller to detect all input devices. All these input devices are connected to the PLC.

Program Scan: This program scan just executes the program logic which is created by the user.

Output Scan: Energizes or de-energizes to all output devices that are connected to the programmable logic controller.

Housekeeping: This step adds communication with programming terminals.

Programming Language of a PLC

Though the ladder programming language is mostly used in the programmable logic controller, still there are remaining a lot of programming languages that are used in the programmable logic controller.

There are mainly 5 types of programming languages. These are:

Ladder Diagram

Function Block Diagram

Structured Text

Instruction List

Sequential Function Chart.

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Ladder Diagram (LD)

Traditional ladder logic is a graphical programming language. At first, programmed with straightforward contacts that reenacted the opening and shutting of transfers, Ladder Logic programming has been extended to incorporate such functions as counters, clocks, move registers, and math activities.

Function Block Diagram (FBD)

A graphical language for portraying sign and information courses through re-usable function squares. FBD is extremely helpful for communicating the interconnection of control framework calculations and logic.

Structured Text (ST)

A significant level of book language that energizes organized programming. It has a language structure (sentence structure) that firmly looks like PASCAL and supports a wide scope of standard functions and administrators.

Instruction List (IL):

A low level "constructing agent like" language that depends on comparable directions list languages found in a wide scope of the present PLCs.

Sequential Function Chart (SFC)

A technique for programming logic control frameworks at an all the more exceptionally organized level. An SFC program is a diagram of the control framework, where the essential structure squares are whole program records. Each program document is made utilizing one of the different sorts of programming languages. The SFC approach arranges enormous, confounded programming errands into littler, progressively sensible undertakings.

Advantages & Disadvantages of Programmable Logic Controller

Using a programmable logic controller, there is a lot of advantages and also a few drawbacks.

Some of the advantages are mentioned as bellows,

Reduced Space

PLCs are kind of complete solid-state devices that is why they are small in size. Because of the small size of the programmable logic controller, there is a need for less space.

Higher Life and Reliability

These electronic devices are heavy in the sense of the long term used. It is extremely rugged. There are 05% chances of defect/damage. It means that it is much possible to lasting this programmable logic controller.

Economical

As there is no chance of defecting, that’s why it requires less maintenance. For less maintenance, there is not also need any cost. People can think that installing a programmable logic controller is one kind of investment. That’s why you can easily consider that PLC is the most economical system. The cost of installing a PLC is recovering within a very short time.

Energy Saving

By an equivalent relay-based control, average power consumption is just1/10th of power consumed.

Good Flexibility

There is not requiring any rewiring if there is require any change is required to be implemented. The programmable logic controller contains the very first scan time. Because of the faster scan time, it requires less operating time, increases the production rate.

The programmable logic controller required shorter training time. It has also a wide range of control applications. There is possible to program easily and it can understand programming language too, it should be a ladder diagram. Though ladder diagram use mostly but, another programming language also used.

Disadvantages of Using Programmable Logic Controller

Using the programmable logic controller, there are also some disadvantages besides advantages. Some of the disadvantages are mentioned as bellows:

There are some difficulties if you want to change the

If there is a rise in a problem, the programmable logic controller can hold up the running an operation for a long time. The hold-up time is indefinite, usually long.

When you prefer for using a programmable logic controller you have to consider the temperature, vibration, etc. actually there are some limitations of working PLCs under high temperature, vibration conditions, and a lot more.

A lot of PLCs start when the power is restored. That time there are little chances to happen in any kind of accident. It is also a difficult task of finding any errors; it also requires a skillful workforce.