Daily Archives: February 20, 2019

A Beginner’s Guide on Simple PLC Controls for Dummies

We can all agree that entering the automation scene and understanding PLCs from the very beginning can be overwhelming especially if you do not know where to start.

Even though the beginning is the right way to start, the massive pile of information is only going to give you a headache. Therefore, you have to understand what is a programmable logic controller, or PLC.

We are talking about compact industrial computers that feature modular components that will help you deal with automate customized control processes.

PLCs are common in industrial plants and factories with the idea to control pumps, fans, lights, motors, circuit breakers, and other machinery.

If you wish to understand the purpose of programmable logic controllers, you should check out PLCs for dummies, while we will present you a brief history of it:

History of Programmable Logic Controllers

Everything started back in the middle of the 20th century when the automation industry entered the scene and wanted to improve the production processes. For instance, automation was usually finished by using complex electromechanical relay circuits.

The main problem was that amount of wires, relays, and space required to automate a simple process was overwhelming, so engineers wanted to implement a more convenient solution that will be less time-consuming and more efficient in overall.

When it comes to necessary levels, electromechanical relays function by magnetically closing and opening their electrical contact as soon as they notice that relay contains energy. They are convenient and useful devices that are still part of industrial automation, but not as before.

In 1968 everything changed because the first PLC entered the factories with the idea to replace expensive, complicated and time-consuming relay circuits. The primary purpose of its design is that plant technicians and engineers could use it without additional training and learning.

Since most of them were already familiar with control schematics and relay logic, the programming language used the same variables to make it more convenient and convenient than before.

From the very beginning, programmable logic controllers used ladder logic for communication between them and other machines in the specific industry. At the same time, ladder logic was made and designed to mimic completely control circuit schematics.

Have in mind that ladder diagrams tend to look exactly like control circuits in which power flows from left to right through closed contacts with the idea to energize a relay coil at the very end and return with valid information.

Ladder logic features simple control circuit schematics where input sources such as proximity sensors, push buttons and switches are on the left while output sources are on the right side.

You will be able to program complex automated process by using intuitive interface, which means that transition from relay logic to PLCs was much more convenient than in the past.

Of course, you can imagine that first programmable logic controllers had limitations when it comes to speed capabilities and memory, but as time went by, they improved themselves and became a prominent and essential part of the automated industry.

The presence and existence of PLCs helped simplify the implementation and design of industrial automation. The best way to learn more on programmable logic controllers is by clicking here.

How Do Programmable Logic Controllers Function?


The idea is to describe a PLC as small industrial computers that feature modular components that are specifically designed to control and maintain control processes. Have in mind that PLCs are controllers among all industrial automation that you can find nowadays.

Of course, you can find numerous components inside of it, but the idea is to divide its nature and operations into these three categories:

  • CPU (processor)
  • Inputs
  • Outputs

Since PLCs are robust and sophisticated computers, our primary goal is to help you understand its function by using simple terms and examples.

The idea is that the programmable logic controller takes inputs by performing logic on them and sending them toward CPU so that the processor could use the logic and turn on or off the output based on the programming.

  • The primary goal of CPU is to monitor the status of inputs such as proximity sensor off, switch on, valve open and many more.
  • At the same time, the CPU will take the information it gets from the inputs and performs logic on them so that function could be sent further.
  • After it uses the information and performs logic on inputs, it drives it toward outputs and uses the information to complete the cycle.

The idea is to use a familiar example, so imagine a dishwasher. Have in mind that most of them feature microprocessors inside that feature similar functions as programmable logic controllers.

Since dishwasher features inputs, outputs, and processor, we can use it as the best example. For instance, inputs on the dishwasher are buttons on the front, door switch as well as water sensors inside.

On the other hand, outputs are heat elements, pumps and water valves inside. The idea is to think through everything so that you can understand how it functions in overall.

  • The first step is to place it in the cycle mode and to push the start button as well as programs that will fit your preferences. These buttons are inputs that you are pressing with the idea to send signals or information toward CPU so that the microprocessor could use it and control outputs that will let the water inside and start with the procedure.
  • CPU will verify that doors are closed, and fill valve will open which means that dishwasher will start to supply itself with water, which says that CPU used the logic of input and moved it toward the output to perform the selected operation.

Check out this website: https://www.wikihow.com/Make-a-Light-Controller so that you can learn how to make a light controller by using ladder logic and PLC programming.

What about Inputs and Outputs?

Inputs and outputs can be discrete or digital signals. Have in mind that discrete signals are the ones that could only be turned on or off. These are the most common and simplest types of inputs.

Even though the dishwasher example did not use analog input and output, some machines today are still using them. By using analog signals, you will have the ability to measure input and output based on your preferences.