How Does PLC Works

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Hello, welcome to another article. In this article, I will explain you How Does PLC Works but before starting my main topic you have to understand the basics first.

So, let’s begin.

What is PLC?

How Does PLC Works

PLC stands for Programmable Logic Controller

In a simple way, we can say the programmable logic controller is a digital computer which we can use in industries to control our manufacturing process.

Programmable Logic Controller is a controller which controls our manufacturing process by our provided logic in the face of a program which was feed in it.

After understanding the basics you should know how plc invent.

The Invention Of PLC

Programmable Logic Controller was developed in three stages.

Actually, PLC was born from automotive industry of USA.

Stage # 1

How Does PLC Works

When PLC not available at that time automobile industries use relays and closed-loop controllers to control their manufacturing process. But this stage is not sustainable because the process of updating is very time consuming and electrician needed to rewire those relays to change their process which was need so time.

We know that in manufacturing industries the time is essential because the whole chain of manufacturing depends on seconds.

So, that’s why they reject this and looks forward to another solution.

Stage # 2

How Does PLC Works

After some time when digital computers are available then they use the general-purpose programmable device to control their industrial processes.

But at this stage, these computers are required specialist programmers and also it faces the challenges of Environment as well because those computers need high cleanness and quality of power.

So, after these two stages, the stage of PLC was invented.

Stage # 3

How Does PLC Works

The stage of PLC. To meet these challenges the PLC was developed.

The PLC was developed with some key attributes.

  1. PLC can tolerate the environment of floors.
  2. PLC not required a year of training to use.
  3. PLC was highly reliable.

Now on these days, PLC use enough in different manufacturing industries.

How Does PLC Works

How Does PLC Works

Here we take an example of PLC based Mixer to understand How Does PLC Works.

As you can see in the above figure we have two pumps Liquid A Inlet & Liquid B Inlet which are being used to transfer two separate liquids into this tank.

Inside the tank, there are two levels of Sensors are installed in the lower Sensor S2 and in the upper Sensor S1 parts of the tank respectively.

Both sensors are digital which means they can only ever be in one of two states: “True” or “False”.

There is also an electrically powered mixer inside the tank which starts working for a defined period of time, mixing the two liquids together after the tank has filled.

We also have discharge valve in the bottom of the tank which controls the draining of the liquid from the tank.

Ok now let’s see what program we want to implement on this tank through PLC and How Does PLC Works?

In this mixer, we just want that the level of liquid in the take do not drop from the lower level of the tank where sensor 2 is available.

First, we have to create a program related to our requirement then burned that program into PLC to control that program and mixer as well.

So, how does Plc control that program?

The lower level of sensor S2 has an open contact inside it. When the level of the liquid drops to the level of the sensor’s position the contact closes, sending a 24-volt DC signal to the PLC input.

And we know we already burned the program in a PLC when the level of the liquid reaches this minimum, the pumps will be activated and are filling the tank with the liquids.

The Pumps continue filling the tank until the level reaches it’s maximum at the higher-level sensor.

When this happens the open contacts in the switch will be closed and another 24-volt signal will be sent to the PLC input telling us that the tank is full.

When this signal has been sent, first the pumps should shut down so that no more liquid enters the tank, and the mixer should be turned on.

So, the friend that’s how PLC does work.

“PLC takes input from the sensors which we implement on any tank and machine as well to take input signals and then PLC perform their operations as per provided program which was we feed in that PLC. PLC just work according to your provided program.”

That’s all!

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