What is AUTOMATION?-Introduction

What is Automation?


  • Automation – A Control System which takes care of operation in automated way with minimum human Intervention.


What is Control System?


A control system is a combination of various devices that are integrated as a system used to sense, measure, indicate, and control the process variables, which in turn controls the process to achieve the desired results.


Classification of Automation can be given as,


What is Industrial Automation?


  • Industrial Automation is defined as the use of the control system such as PLC, PAC, HMI, SCADA & VFD to control the Plant or Machinery thereby reducing the need for human intervention


Classification of Industrial automation can be given as,


What is I/O?


  • The term I/O’S are referred as Inputs & Outputs which is connected to the controller.


List of Input devices


  • Sensors
  • Limit Switch
  • Push Button
  • Selector Switch
  • Pressure, Level, Temperature & Flow Switches
  • Toggle Switch ETC……


List of Output devices


  • Motors
  • Solenoid Valves
  • Pumps
  • Indications
  • Alarms etc..

What is PLC?-Introduction

What is PLC? (Programmable Logic Controller)


  • To build a perfect automation system we need a digital industrial computer which is known as PLC (Programmable Logic Controller).


Our PLC’s:


The pictures shown below are typical Selec make PLC’s,

We select Automation uses this PLC’s to give automation solutions for industries.


Architecture OF PLC’s;


The below picture is a general architecture of PLC’s,


For an introduction about PLC please click here PLC BASICS


What is PAC?-Introduction

What is PAC? (Programmable Automation Controller)


  • Programmable Automation Controller.
  • PAC is a compact controller which combines the features of Process control, Motion Control, Data Acquisition along with PLC.
  • Up to 2 Lakh I/O’s can be supported.
  • Replacement of DCS (Distributed Control System), which involves huge size & complexity.

What is HMI?-Introduction

What is HMI? (Human machine Interface)


·        Human Machine Interface, also Called as Man Machine Interface

·        It is graphical user interface, with text messages along with alarm indication

·        HMI can be easily interfaced with PLC, PAC & VFD


What is VFD?-Introduction

What is VFD? (Variable Frequency Drive)


  • Variable Frequency Drive
  • Speed of the motor & pump can be varied from a particular speed to the preset speed.
  • VFD consist of three types namely,
  • DC drives, AC drives & Servo drives

What is SCADA?-Introduction

What is SCADA? (Supervisory Control and Data Acquisition)


·        SCADArefers to an industrial control system.

·        A computer system monitoring and controlling a process.

·        The process can be industrial, infrastructure or facility-based electrical power,water treatment plants,oil and gas pipelines


What is networking in SCADA?

What is SCADA? (Supervisory Control and Data Acquisition)


·        Networking,that is connecting the SCADA (A PC system) with a number of PLC’s, I/O’s, micro plc’s using an ethernet with control level and device level control buses.


The below picture show a typical Network in a Automobile industries




  • LG

Applications and advantages of PLC and a MICROCONTROLLER

Applications & Advantages of PLC and MICROCONTROLLER:


A microcontroller design would be appropriate where end user need not alter the controls, rather only selecting controls(like timer).


Example: .A washing machine where user only selects different controls and need not alter the controls. Similarly in home automation also where there is no need of  altering the controls.


Also in mass production where development cost (design of power supplies, input/output hardware and necessary testing and certification) can be spread over many sales, and where the end-user would not need to alter the control.


Example: Automotive applications are an example; millions of units are built each year, and very few end-users alter the programming of these controllers.


PLC applications are highly customized systems so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design.


PLCs contain input and output devices compatible with industrial devices and controls; little electrical design is required, and the design problem centers on expressing the desired sequence of operations.


Very complex process control may high-performance PLCs.


Example: Programmable controllers are widely used in motion control, positioning control and torque control,chemical industries


Very high-speed or precision controls may also require customized solutions;


For example, aircraft flight controls.


Our PID controller & Introduction to PID controller

Introduction to PID controller


·       Many real world processes build up over time.Unlike digital which are 0’s and 1’s real time process are varying and constantly updating.


·       So we need to control real time applications using these non constant variables. For this purpose we need a PID controller.


Our PID controller:


The below shown pictures are our PID controllers.

Please visit our website for a list of other products at




PID500 (48x48) | Full Featured PID Controller


PID110 (48x96) / PID330 (96x96) | Full Featured PID Controller


PID528 (48x48) | Full Featured PID Controller


TC518/ 523 (48x48) | Single Set Point Low Cost PID Controller


PID513 (48x48) / PID213 (72x72) / PID313 (96x96) | Very Low Cost PID Controller


What is PID control with block diagram

What is PID controller?


·       A PID (Proportional - Integral - Derivative) is a control feedback mechanism widely used in industrial applications.

·       A PID controller corrects the error between a measured variable (like analog values measured for heat, pressure, flow rate, chemical composition, cruise control in automobiles, etc.,) and,

·       A desired set point by calculating and initiating a corrective action that can adjust the process accordingly and rapidly , to keep the error minimal.

The below diagram shows a simplified PID controller

Why pid control with example

Why PID Controller with an example?


To understand the process clearly we can take the following example of cruise (speed) control in a car,


·       Let’s see how we can control the speed of the car with some assumptions.

·       The speed of the car depends on how hard you press the accelerator.

·       For example say your car should have a automated control specifying that you should drive a speed between 40Kmph and 60 Kmph in a highway.

·       We can control this using a PID controller. Generally the input values are accelerator, your force on the accelerator and output is the speed control of a car.


But for the system the main inputs are P value, I value, D value, and set points and output to control the speed. Now watch carefully what happens

Continued on General working of PID controller……

General working of pid control with example

General working of PID controller


·       When you step on the accelerator of your car, it moves slowly, then faster, and faster still, until you let off the accelerator.

·       As you speed up, you will need to press the accelerator little less, then even less, until you reach the speed limit. As we have seen early unlike the digital world, where things are either “on” (1) or “off” (0), real processes have varying degrees of “on”.

·       In this driving example, how much the accelerator is turned “on” depends on the car's current speed and how different the car's speed is from the speed limit.

·       Controlling such a process with speed can be done with PID controllers.


Inside a PID Controller


What happens inside the PID controller ?


The below image is an schematic of the basic control


·       Speed control is one fine example of a PID control loop. To calculate the output, it needs three factors.

·       The first, (P), is the difference between the current speed and the desired speed (set points).

·       The second, (I), is the sum of the differences over time. (The various speed values of the car in a running time)

·       And, the third, (D), is the rate of change between sampled differences. (The time differences of each speed you reach)

·       Each factor is scaled by a gain constant; they are referred to as Kp, Ki, and Kd. The value of these gain constants determines how responsive the output will be.

·       If the Kp, Ki, and Kd values are too high, the output (car's speed) will exceed the set point (speed limit-60 Kmph).

·       If the Kp, Ki, and Kd values are too low, the output may never reach the set point (speed limit- 40Kmph).

·       So by controlling the P, I, D values we can control a range of output like 40-60Kmph.


This is just a theoretical example for the purpose of understanding the basics of PID controller. In real time for controlling action many factors and variables,parameters are calculated before controlling a particular process.

PLC Basics and Introduction - For BE BTECH ME MTECH Engineering students



We at Select Automation provide optimum facilities for our students to equip and excel themselves with highly sound professionals in Industrial Automation Education (PLC, PAC, SCADA, CONTROLLER’S, VFD’S, VLSI, DSP, HMI’S, Mechatronics Embedded & PLC Control Panels)



Industrial Automation is the present and future trend for the budding student community and working professionals.


It meets the requirements of several industries like:

·        Process Industry.

·        Automotive Industry.

·        Energy Monitoring and load Shedding.

·        Oil & Gas Industry.

·        Petro - Chemical Industry.

·        Water Treatment Plant Etc.


Today’s  Leading Software Mnc’s Provides engineering solutions for Industrial Automation in India & Abroad.


For Eg:

·        Mahindra Satyam


·        Infosys


·        TCS


·        Patni


·        Wipro etc


We are here to share our knowledge on PLC  with engineering students because, Automation is the present and future trend for the student community and working professionals.

Dear students please visit our blog regularly,as we are going update regularly,and if you have doubts post your comments we will reply you everyday.

Okay guys lets start now......

First What is PLC?



  • A plc is a digitally operated electronic system,designed for use in an industrial environment.


  • It uses programmable memory for internal storage for user oriented instructions for implementing specific functions such as logic,sequencing,timing,arithmetic and controlthrough digital or analog inputs of various machines or processes.


  • In simple terms PLC is a solid state,digital,industrial computer.


    The pictures below are the PLC's being used by us for automation solutions

    PLC MM3010 -With built in HMI

    PLC MM1010 - With built in HMI for Low price solution

    To know about our products please check out our websites products at


  • PLC Introduction:


  • A PLC is a device invented to replace sequential relay circuits for machine control.


  • The PLC works by looking at its inputs and depending upon their state turning ON/OFF its outputs.


  • The user enters a program via software ,that give desired results.


  • PLC used in many real world applications which involves machining,packaging,material handling,automated assembly.


  • PLC broadly consists of ,


  • I/O interface
  • Processor
  • Memory
  • Power supply
  • Programmable devices


We will see these categories broadly in another section……


PLC history and Why PLC?

PLC History:

  • In late 1960’s PLC’s were first introduced.The primary reason for designing PLC’s is to eliminate large cost involved in replacing complicated relay based machine.



The above picture is a complicated relay panel used in 1960’s


  • In 1968, the hydramatic division of the general motors(An US car Manufacturer) used MODICON-084.


The above picture is an typical PLC based control panel.


  • In 1960’s industries used electro-mechanical relays,timers,counters were used.
  • Control panel consists of electro-mechanical drives with lengthy wires.These Mechanical devices have a limited life time with high maintenance and involves more trouble shooting.
  • In mid 90’s communication abilities began to appear,
  • In 1980’s the size of the PLC’s are gradually reduced and software programmable through symbolic programming

Differences Between PLC and MicroController/Microprocessor

 Differences between PLC and Microcontroller:


  • A microcontroller design would be appropriate where end user need not alter the controls or using minimal controls.


  • PLC’s allow end user to configure and control the application which is more useful in industries.


  • Very complex controls and process like chemical industries requires more re-configurable controls.


  • PLC’s with I/O(Input/Output) devices require little electrical design and programming using simple ladder diagrams which are easy to understand, very simple and customized.


  • In case of mass production PLC’s are economical to build and maintenance.


  • Troubleshooting is also easier compared to microcontroller.


  • To know more details about the differences please give  your query in comments & we will post more,

PLC advantages and disadvantages

 PLC control Panel advantages:


  • Simplified control panel resulting in less maintenance than with relay logic systems.
  • Easier interconnection with plant monitoring and control systems.
  • Easy access to operating and control information.
  • Easy selection of control settings.

PLC Anvantages:

  • PLC’s controls a range of applications from machine automations to critical process applications.
  • Primary goal of PLC is to eliminate high costs with inflexible relay control systems.
  • Less troubleshooting and cost effective.
  • The main difference from other computers is that PLCs are armored for severe conditions (such as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements.These connect the PLC to sensors and actuators.
  • PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of complex positioning systems.
  • On the actuator side, PLCs operate electric motors, pneumatic or hydraulic cylinders, magnetic relays, solenoids, or analog outputs.
  • The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a computer network that plugs into the PLC.