What Is a Programmable Logic Controller (PLC)? PLC Projects


If you are thinking of using PLCs in a project or have heard the term before but isn’t sure of what they are, then you are at the right place! PLCs are being seen as the next big thing in control engineering and is viewed as a mature technology with a tremendous scope with regards to the application. While they have been around for over 50 years, advancements in the field of science have led to several improvements in their functioning and design. As with everything else in the field of consumer electronics, things are constantly changing in this sphere and hence significant improvements are being made to make such chips faster, smaller, and more cost-effective. Still unsure about what PLCs are and how they make life easier for us? Read on to find out more about PLCs, their importance, how to program them and why working on PLC projects is so important.

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1. Automation using PLC

Need for PLCs

PLCs were born over 50 years ago because people wanted programmable chips to help with the automation of systems. Fifty years later, the main problem remains the same. Competition and an exaggerated need for goods are pushing companies into automating their assembly lines and also pressuring them into making their production lines as efficient as possible. In the beginning, PLCs replaced hundreds of electrical components such as relays and timers, by mashing all their functionality into one chip. Now decades later, manufacturers are still trying to decrease the size and weight of automation systems and hence smaller rack-based PLCs are now popular choices within the industry. When it comes to the software side of things, ladder logic programming has found ready success in the field of automation and continues to be the most widely accepted form of PLC programming.

In the future, PLCs will evolve to become more flexible and capable of adapting to changes in hardware and software. Merging of PLCs with programmable automation controllers, better known as PACs will help in greatly improving their functionality. The size of circuit boards and processors are on a steady decline and the electronics industry is on the constant lookout for smaller, faster and more efficient components. PLCs, therefore, need to improve their stability, reliability, and cycle time.

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What is PLC and its application?

PLC stands for Programmable Logic Controller and is basically an industrial computer that works as a standalone unit. They work together as a network in conjecture with other PLCs to help with the automation of control processes and may be used to carry out specific functions. They are connected to a multitude of sensors to make it possible for them to receive and gather information related to the external environment in which they are being used. Hence, these sensors help PLCs gauge everything from the temperature outside to the speed of a rotating shaft. The analog signals from the sensors are converted into digital signals and are then fed into the PLCs. The PLC then uses this real-world information to recalibrate the system and complete a particular pre-programmed task. They are mainly designed for applications that involve multiple inputs and output requirements and also in situations wherein the system needs to withstand severe weather conditions. Unlike PCs that perform a plethora of tasks, PLCs are designed to primarily handle a single set of tasks.

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Scope of plc programming

PLCs are continuously growing and are now considered as the best option for several industrial automation applications. Therefore, the scope of plc programming is rapidly increasing due to the programming flexibility they provide and also due to the ease of programming it ensures. PLCs are easily scalable and work at high speeds thanks to Ethernet connectivity, making them viable options for most of today’s automation requirements. They have also benefited from the growing use of USB technology as this makes it easier to transfer information to and fro PLCs.

With time, PLC programming will evolve even further, and the widespread availability of mini USB connectors will make them an even more popular choice in the future.

Latest PLC technology

  1. Monitoring and control is distributed to several servers
  2. Ability to use them for multi-user applications
  3. Easier maintenance
  4. Availability of more reliable and robust functionalities
  5. Better visualization and mobility
  6. Better resistance against harsh working conditions
  7. Extensive input/output arrangements

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What can I do with a PLC?

  • Turn the power on and off without switches
  • Make simple decisions for the proper functioning of logical control
  • Gather data from the external environment
  • Automate production lines and assembly lines
  • Determine the sequence of operations and time them appropriately

Advantages of PLC

  • Cost-effective
  • Flexible and adaptable to several different working conditions and constraints
  • It allows for more sophisticated control.
  • Easier to troubleshoot, making them easier to program and debug
  • Reliable and robust
  • Requires less manpower for design and maintenance
  • Downsizing and helps with the reduction of weight and size
  • Has become an industry standard
  • Improved maintainability and communication

Internal Architecture of PLC

  1. An arithmetic and logic unit to carry out data manipulation and simple arithmetic operations like addition, subtraction, AND, OR and Negation.
  2. Registers to help with the storage of data
  3. A control unit to time the operations and determine the sequence of functions
  4. Buses that serve as paths for communication within the PLC.
  5. Input and output units to act as the interface between the chip and the external environment

How do you create a PLC program?

  1. Personal Computers are used to program PLCs along with the manufacturers’ and clients’ preferred software. These programs may be run both online and offline, and may also be edited, monitored and debugged as and when required.
  2. Among the available programming languages, a ladder logic diagram is the most preferred one as it is basic and easy to understand.
  3. The first step in programming the PLC is to understand the problem at hand and understand what sort of program is required.
  4. Next, list the end conditions and design a flowchart that best describes the problem at hand and the proposed solution. Make sure you list all the variables required to run the program.
  5. Now, install and configure the programming software you need for your particular PLC hardware. Configure the right PLC hardware model with appropriate I/O modules.
  6. Select a suitable ladder language and name the program.
  7. Add the rungs required based on the logic your program requires and then address each input and output.
  8. Once the basic framework of the program is done, check for errors and make the required changes.
  9. Test run the program to see if there are any bugs you need to remove. Stimulate the program by running it online.
  10. If everything works out fine, download the program and then move it through a cable to the machine you need it to control.

How to make a simple PLC project?

A programmable logic controller is used mainly to control manufacturing processes and automate assembly lines and robotic devices.

Automation using PLC: In this PLC project, you will make a system using PLC that contains a pick and place robot and a conveyor belt. The robot picks and place components and work in sync with the conveyor belt.

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Here is a list of a few simple projects you can try out by using PLCs.

  • Power Plant Coal Level Sensing
  • Remote Access Laboratory Using SCADA.
  • Protection Of Induction Motors
  • Industrial Timer Controller
  • Automatic Industrial Drainage Timer
  • Temperature and Pressure Controller
  • Automatic Bottle Filling System
  • Automatic Car Washing System

Hope you got an idea about how to develop a PLC project from this article. If you have any better ideas or suggestion let us know in the comments.

Thank you.

What Is a Programmable Logic Controller (PLC)? PLC Projects
Skyfi Labs Last Updated: 2022-05-14

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