Presentation

on

“Study of PLC”

at

“Pyrotech Electronics Pvt. Ltd.”

(2011-2012)

Submitted to:

Dr.Navneet Agrawal

Asstt.professor&

Training Incharge

Electronics and Communication Department

C.T.A.E. Udaipur

NARENDRA MEENA

JAILAL MEENA

AMIT VERMA

Submitted by:

   

Pyrotech Electronics Unit-II Today, it is one of the India’s leading manufacturer of

automation and control equipment.Pyrotech has an exceptional multi disciplinary array of

products like-Mosaic panel & desksControl panelsAutomation Panels Mimic PanelsTransducer Panels PLC & I/O PanelsRelays Panels

Storage

CNC Lab

Fabrication

7 Tank

Powder Coating & Painting

Assembly

Wiring

Packing & Dispatch

Main Process

PLC : Programmable Logic Controller

Programmable:The device which is user friendly and can be programmed according to the Requirement.

Logic:Can take reasoning decision.

Controller:control device.

Introduction 

PlCs were first introduced in the 1960’s. the primary reason for designing such a device was eliminating the large cost involved in replacing the complicated relay based machine control systems.

Definition: A programmable controller is a solid state user

programmable control system with functions to control logic, sequencing, timing, arithmetic data manipulation and counting capabilities.

Hardwired Relay ComparisonRelays PLC controller

•Large amount of work required in connecting wires.•Difficulty with changes or replacements.•Difficulty in finding errors.•It is costly.•Relays are less reliable.

•Occupy more space.

•Lifetime of relay contacts are limited.

•Wires needed for connections are reduced.•Changes can be easily done by replacing a program.•Fast & easy error detection.•It is much cheaper.•More reliable because of less moving parts.•Compact & occupy less space.•It has long lifetime.

Overview of PLC

What Exactly is PLC A PLC basically consists of two elements:

1. The central processing unit

2.The input/ output system

1.Central Processing Unit The central processing unit (CPU) is the part of a

programmable contoller that retrieves, decodes, stores, and processes information.It also executes the control program stored in the PLCs memory.

PROCESSORMEMORY SYSTEM

POWER SUPPLY

CPU

1. Processor: The processor is the section of the CPU that codes,

decodes, and computes data.

2. Memory: The memory system is the section of the CPU that

stores both control program and data from the equipment connected to the PLC.

3. Power Supply: The power supply is the section that provides the

PLC with the voltage and current it needs to operate.

CPU PARTS

I/O System

I/O system is the section of a PLC to which all of the field devices are connected.

The I/O system consists of two main parts:

1. the rack2. I/O modules

1. Rack: The rack is an enclosure with slots in it that is

connected to the CPU.

2. I/O Modules:I/O modules are devices with connection terminals to which the field devices are wired.

Together, the rack and the I/O modules form the interface between the field devices and the PLC.

This creates the physical connection between the field

equipment and the PLC.

In some small PLCs, the rack and the I/O modules come prepackaged as one unit.

Field Devices

All of the field devices connected to a PLC can be classified in one of two categories:

1. Inputs2. Outputs

1. Inputs are devices that supply a signal/data to a PLC. examples : push buttons, switches, and measurement

devices.

Basically, an input device tells the PLC, “Hey, something’s happening out here…you need to check this out to see how it affects the control program.”

Outputs : are devices that await a signal/data from the

PLC to perform their control functions. Example: Lights, horns, motors, and valves. These devices stay put, minding their own

business, until the PLC says, “You need to turn on now” or “ You’d better open up your valve a little more,”etc

There are two basic types of input and output devices:

1. Discrete2. Analog

1. Discrete devices: are inputs and outputs that have only two states: on and off. 1s and 0s. A 1 means that the device is on and a 0 means the device is off.

2. Analog devices: are inputs and outputs that can have an infinite number of states.

PLC operation

A PLC works by continually scanning a program.

We can think of this scan cycle as consisting of 3 important

steps: Check the Input Status Execute Program Update Output Status

1. Check the Input Status: First the PLC takes a look at each input to determine if it is on or off. In other words, is the sensor connected to the first input on? It records this data into its memory to be used during the next step.

2. Execute Program: Next the PLC executes program[one instruction at a time].It

will store the execution results for use later during the next step.

3. Update Output Status: Finally the PLC updates the status of the outputs based on

which inputs were on during the first step and the results of executing program during the second step.

Basic InstructionThere are two basic types of instruction:

1. Contacts

2. Coils

1. Contacts:

Contacts are instructions that refer to the input conditions to the control program that is, to the information supplied by the input field devices.

2. Coils:

Coils are instructions that refer to the outputs of the control program that is, to what each particular output device is supposed to do in the system.

Example of PLC

29

Tank Used to Mix Two Liquids

A

B

C

FS

MOTOR

TIMER

FLOAT SWITCH

SOLENOIDS

SOLENOID

1 -MINUTE

Example:

Advantages of PLCReduced space.Energy saving.Ease of maintenance.Economical.Greater life and reliability.Tremendous flexibility.Shorter project time.Easier storage, archiving and documentation.Withstand harsh environments.Expandability.Facility for extensive I/O arrangements.

Applications of PLC system

PLCs are used for control and automation purposes machines.

Used in industries like:Tyre industries.Blender industries.Steel plants.Dairy automation.Printing industries.Pulp factory.

They are used in Robotics also.

Conclusion PLCs are designed to provide flexibility

in control based programming and executing logic instruction. PLCs allowed for shorter installation time & faster commissioning through programming rather than wiring.

The PLC have in recent years experienced an unpreceded growth as universal element in industeial automation.