“Introduction to PLC-SCADA & Its Industrial � Applications”

Prof. J.R.Prajapati

M.Tech(VLSI & Embedded Systems)

Electrical Engg. Dept.

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R.N.G.Patel Institute of Technology(RNGPIT) Tajpore, Bardoli

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CONTENTS:

1. PLC Introduction

2. Architecture

3. PLC System

4. PLC Programming(Ladder Diagram)

5. Applications

6. Input/Output

7. SCADA

8. Conclusion

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PLC - Introduction

What does PLC stand for?

PLC - Programmable Logic Controller

• PLC implements logic control functions by means of a program
• User defined Program Control whole Process.

How does a PLC differ from a computer?

• A computer is optimized for calculation and display tasks
• A computer is programmed by specialists
• A PLC is designed for (logic) control and regulation tasks
• A PLC is programmed by non-specialists
• A PLC is well adapted to industrial environment

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PLC - Introduction

Where are PLCs used?

• In every industry where automation is involved, from individual machines to whole processes

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What tasks do PLCs perform?

• The logic control tasks such as interlocking, sequencing, timing and counting (previously undertaken with relays or pneumatics)
• In addition, PLCs can perform a variety of calculation, communication and monitoring tasks

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PLC - Introduction

Why are PLCs so common?

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• They are cost-effective
• They are flexible, reliable and compact
• They have significant advantages over traditional control systems based on relay or pneumatics

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• A PLC contains a basic operating system that allows for:

– Downloading and executing user (ladder logic) programs

• – Communicating with devices

• I/O modules

• Other PLCs on a network

• – Holding configuration data such as
• • Number and type of I/O modules present in the PLC

system

• • Status information

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PLC - Introduction

PLC - Introduction

Features

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Architecture

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PLC System

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Programming of PLC

• Different Techniques to Program
• Ladder Diagram (LD)
• Sequential Function Charts (SFC)
• Function Block Diagram (FBD)
• Structured Text (ST)
• Instruction List (IL)

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Among this languages Ladder Diagram is very Popular

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Why ladder?

• A ladder diagram features an excellent graphical representation based on well-understood circuit design concepts.

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• Excellent debugging tools. Modern online debugging tools available in a ladder diagram provide an animation showing live “power flow

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• Efficient representation for discrete logic. Because a ladder diagram is designed to mirror electrical circuits, it naturally is a good way to represent discrete logic.

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Ladder Basics

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Input

Instructions

Output

Instructions

A program is a series of instructions that directs the PLC to execute actions.

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Relay ladder logic, the standard programming language, is based on

electromagnetic relay control

Simple Concept of Electrical

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State Diagram of Motor On-Off

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Ladder Diagram

State Diagram

https://instrumentationtools.com/relay-schematic-working-animation/

How Ladder Works

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How Ladder Works

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How Ladder Works

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How Ladder Works

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Overview of Ladder…

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Interfacing with Relay

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Different Logics in Ladder

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Applications of PLC

Gate Control

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• PLC can sense a vehicle at the entrance or exit, and open and close the gate automatically
• The current vehicle count is easily determined by programming a simple counter

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Applications of PLC

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Applications of PLC

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Applications of PLC

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Inputs

Outputs & Power Supply

Communication

Ports (RS-485)

How PLC Looks..

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Structure of a PLC

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The PLC processor

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PLC Input / Output Devices

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• Push buttons
• Switches (limit switches, level switches, etc.)
• Sensors(Proximity, Temperature etc..)

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PLC Input Devices

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• Relay contacts
• Solenoid valves
• Signal devices (such as lamps, alarms, etc.)
• Motors

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PLC Output Devices

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Programming terminal

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• Programming is done through programming terminal
• Programming terminal translates engineering language (logic control) to machine language (binary code)
• Most PLC manufacturers offer software packages that allow a standard computer to be used as a programming terminal

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Programming through standard computer�

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• The CPU reads the data from the inputs
• The program in the CPU uses the inputs to evaluate the control logic. As the program runs, the CPU updates the data
• The CPU writes the data to the output

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Relating the program to inputs & outputs

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lecture note 9 PLC

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Relating the program to inputs & outputs

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SCADA

• Supervisory control and data acquisition (SCADA) is a control system architecture comprising computers, networked data communications and graphical user interfaces (GUI) for high-level process supervisory management

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Automation in Industry- At Different levels…

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DCS- In Plant

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DCS- In Plant

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DCS- In Plant

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DCS- In Control Room

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Conclusion:

• PLC is heart of Automation.
• Today almost every Industry has automation.
• As Engineer we should have knowledge of PLC, DCS & Its Programming.
• Bright future in the Field of Automation.

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References:

• https://www.controleng.com/articles/ladder-logic-strengths-weaknesses/
• https://en.wikipedia.org/wiki/Distributed_control_system
• https://www.emerson.com/en-us/automation/
• https://unitronicsplc.com/what-is-plc-programmable-logic-controller/
• https://www.electrical4u.com/programmable-logic-controllers/

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Thank You….

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