plc report

ANIL MAURYA 1

Electrical & Electronics Engineer

A

Report on

Practical Training

at

TRAINING ON ROCKWELL

AUTOMATION

BY

ANIL MAURYA

ELECTRICAL & ELECTRONICS ENGINEER

ANIL MAURYA 2


CONTENTS

Content

List of table

List of Figure

Chapter 1 Rockwell Automation Overview

1.1About Rockwell Automation 1

1.2 Company history 2

1.3 Products of PLC 2

Chapter 2 Introduction

2.1 What is Automation ? 4

2.2 Information of PLC 3

2.3 Programmable Control Systems

Chapter 3 Identifying Logix5000 System Components

3.1 Logix5000 Systems 6

3.2 Logix5000 Control Disciplines 6

3.3 Control Logix Platform and Components 6

3.4 ControlLogix Chassis 7

3.5 ControlLogix Backplane 7

3.6 ControlLogix Controller 7

3.7 ControlLogix I/O Modules 8

3.8 Project Components 8

3.9 Tasks 8

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3.10 Programs 8

Chapter 4 Basic Ladder Logic Instruction For an RSLogix 5000 Routine

4.1 Basic Instructions 11

4.2 Timer Instructions 12

4.3 COUNTER Data Type 13

4.4 TIMER Data Type 14

4.5 TON Instructions 15

4.6 TOF Instructions 15

4.7 Reset Instructions 16

4.8 RTO Instructions 16

4.9 BTD Instructions 16

4.10 Move Instructions 16

Chapter 5 Connecting a computer to A Communication Network

5.1 Communication Card 17

5.2 Driver 17

5.3 Serial Connection Overview 17

5.4 RSLinx Classic Software ` 18

5.5 Configuring Local Communication Driver 18

Chapter 6 Creating and Organizing

6.1 Project/ project file 19

6.2 Creating a New Project File 19

6.3 Coordinate System Time (CST) Master 20

6.4 Creating a Program 20

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6.5 Creating a Routine 20

6.6 Monitor Controller System Data 21

6.7 GSV/SSV Parameters 22

6.8 Force Functions 23

6.9 Rules for Forcing 24

6.10 ControlLogix Digital and Analog I/O Modules 25

Chapter 7 Identifying DeviceNet Network Components

7.1 DeviceNet Network 26

7.2 Components 26

7.3 EDS Files 26

7.4 Node Commissioning 27

7.5 Node Addresses 27

7.6 Scanner Module Communication with Devices 28

7.7 Scanner Module Communication with Controller 29

7.8 Mapping 29

Chapter 8 FactoryTalk View SE Programming

8.1 FactoryTalk Overview 30

8.2 Configuring the FactoryTalk Directory 30

8.3 FactoryTalk View Studio Software Components 31

8.5 OPC (Object Linking and Embedding for Process Control) 31

8.6 HMI Tag 31

8.11 Creating and Manipulating Graphic Objects 32

8.14 Global Objects in a FactoryTalk View 32

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8.16 Creating and Viewing a Data log Model 33

8.17 Creating and Configuring a Trend 33

List of Tables

Chapter 2

Table 2.1 using of PLC in industries 4

Table 2.2 Input/Output (I/O) systems 5

Chapter 3

Table 3.1 PLC’s switching position 9

Table 3.2 Data Types 9

Chapter 4

Table 4.1 Conditional Bit Input Instructions 11

Table 4.2 Conditional Bit Output Instructions 11

Table 4.3 One Shot Instructions 11

Table 4.4 Retentive Bit Output Instructions 12

Table 4.4 Counter Instructions 14

Table 4.5 Timer Instructions 15

Table 4.6 Math Instructions 16

Chapter 6

Table 6.1 Creating a New Task 19

Table 6.2 Communication Format 20

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Chapter 7

Table 7.1 Devices (nodes) 25

Table. 7.2 Scanner Modules 29

LIST OF FIGURES

Chapter 1

Fig 1.1 specific diagram of PLC 1

Chapter 2

Fig 2.1 processing of PLC 3

Fig 2.2 Network of PLC 5

Chapter 3

Fig.3.1 connection between computer and PLC 8

Chapter 5

Fig 5.1 communications network 17

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CHAPTER 1

ROCKWELL AUTOMATION: AN OVERVIEW

1.1 ABOUT ROCKWELL AUTOMATION:

Rockwell Automation is a global provider of industrial automation, power, control and

information solutions. Brands in industrial automation include Allen-Bradley and

Rockwell software.

Headquartered in Milwaukee, Wisconsin, Rockwell Automation is one of the largest

industrial automation companies in the world, employing about 21,000 people in more

than 80 countries. It is a Fortune 500 company, ranked number 411 on the list.

Rockwell Automation, the world's largest company dedicated to industrial to

automation, is known to make its customers more productive and the world more

sustainable. Through out the world, their flagship Allen-Bradley® and Rockwell

Software®product brands are recognized for innovation and excellence.

Fig 1.1:. Headquarters of Rockwell Automation, Milwaukee, Wisconsin

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1.2 COMPANY HISTORY:

Rockwell Automation was initially founded in 1903 as the Compression Rheostat

Company by Lynde Bradley and Stanton Allen with an initial investment of $1,000. In

1910 the company was renamed the Allen-Bradley Company. In 1952 they opened a

subsidiary in Galt, Ontario, Canada, that now employs over 1,000 people. In 1985 a new

company record was set as they ended the fiscal year with $1 billion in sales. On

February 20, 1985 Rockwell International (now Rockwell Automation) purchased Allen-

Bradley for $1.651 billion, which is the largest acquisition in Wisconsin's history.

Rockwell Automation spun off from Rockwell International in 2001. From there,

Rockwell Automation went through a series of acquisitions, particularly Propack

Data (now Rockwell Automation Solutions GmbH) in 2002, DataSweep in

2005, GEPA in 2006, ICS Triplex, ProsCon and Pavilion Technologies in 2007,

andIncuity in 2008 and Lektronix Ltd in 2011.

On January 31, 2007, Rockwell Automation sold off their PowerSystems Division which

consists of Dodge mechanical and Reliance Electric motors with headquarters

in Greenville, South Carolina, to Baldor Electric Company. In 2012 the company was

named by Ethisphere Institute One of World's Most Ethical Companies for the fourth

time.

1.3 PRODUCTS:

• Programmable Logic Controllers: ControlLogix, PICO, Micro 800, MicroLogix,

SLC500, PLC5 and Datasite RT.

• I/O : FlexIO, CompactIO, PointIO, etc.

• HMI : PanelView Standard, PanelView enhanced, PanelView Plus, Industrial

Computers & Monitors, etc.

• Industrial Safety Products: GuardLogix, SafetyIO, XM Vibration Monitors, etc.

• Servo Drives: Kinetix, Ultra

• Variable-Frequency Drive: PowerFlex Drives, Drive Systems.

• Rockwell Software Brand: RSLogix5000, RSNetWorx, RSLinx, PMX, FactoryTalk

etc.

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• Motor Controllers : MCCs (Allen-Bradley's CENTERLINE MCC with

IntelliCENTER Technology), industrial control (contactors, overloads, circuit

breakers etc.)

• Condition Monitoring/Vibrational Analysis : Entek

• Sensors (Photoelectric, Capacitive, Inductive, Ultrasonic):Rockwell

Automation/Allen-Bradley Sensor.

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CHAPTER 2

INTRODUCTION TO PLC TECHNOLOGY

2.1 WHAT IS AUTOMATION?

Automation is the use of machines, control systems and information technologies to

optimize productivity in the production of goods and delivery of services. The correct

incentive for applying automation is to increase productivity, and quality beyond that

possible with current human labour levels. Mechanization provides human operators

with machinery to assist them with the muscular requirements of work, while automation

greatly decreases the need for human sensory and mental requirements while increasing

load capacity, speed, and repeatability.

The term automation, inspired by the earlier word automatic (coming from automaton),

was not widely used before 1947, when General Motors established the automation

department. At that time automation technologies were electrical, mechanical, hydraulic

and pneumatic. Those days relay operated systems were extensively used for automation.

2.2 EVOLUTION OF PLC’S:

In the 1960's Programmable Logic Controllers were first developed to replace relays and

relay control systems. Relays, while very useful in some applications, also have some

problems. The main problem is the fact that they are mechanical. This means that they

wear down and have to be replaced every so often. Also, relays take up quite a bit of

space. These, along with other considerations, led to the development of PLCs. More

improvements to PLCs occurred in the 70's.

In 1973 the ability to communicate between PLCs was added. This also made it possible

to have the controlling circuit quite a ways away from the machine it was controlling.

However, at this time the lack of standardization in PLCs created other problems. This

was improved in the 1980's.The size of PLCs was also reduced then, thus using space

even more efficiently. The 90's increased the collection of ways in which a PLC could be

programmed (block diagrams, instruction list, C, etc.). They also saw PLCs being

replaced by PC's in some cases.

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2.3 WHAT IS A PLC?

A Programmable Logic Controller, or PLC for short, is simply a special computer device

used for industrial control systems. They are used in many industries such as oil

refineries, manufacturing lines, conveyor systems and so on, wherever there is a need to

control devices the PLC provides a flexible way to "soft wire" the components together.

The basic units have a CPU (a computer processor) that is dedicated to run one program

that monitors a series of different inputs and logically manipulates the outputs for the

desired control. They are meant to be very flexible in how they can be programmed

while also providing the advantages of high reliability (no program crashes or mechanical

failures), compact and economical over traditional control systems.

In simple words, Programmable Logic Controllers are relay control systems put in a very

small package. This means that one PLC acts basically like a bunch of relays, counters,

timers, places for data storage, and a few various other things, all in one small package.

2.4 INFORMATION FLOW IN PLC SYSTEMS:

Information flow in a programmable control system flows in the following order:

Fig2.1: An example for programmable control system

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1. The system monitors input information from a device (e.g., a start stop panel).

2. The controller evaluates the information using a given set of rules (e.g., if the start

button has been pressed then start the motor).

3. The output information is used to control a device (e.g., the motor is started).

2.5 APPLICATIONS OF PROGRAMMALE CONTROL SYSTEMS :

Programmable control systems can be used in a variety of applications from simple and

repetitive tasks to sophisticated manufacturing and process control. Some of them are

listed below:

INDUSTRY APPLICATION TASKS

Rubber and plastic Tyre manufacturing Sequencing of tyre press/cure

Alerting to malfunctions

Storing information

Chemical Chemical batching Setting mixtures ratios

Determining rates of discharge

Recording inventory

Power generation Plant power systems Regulating distribution

Monitoring usage

Warehousing Material handling Storing

Retrieving

Warehousing

Transporting(conveyors)

Entertainment Rides / Productions Monitoring safety of theme park rides

Controlling stage productions

Table 2.1: Some applications of programmable control systems

A programmable control system has replaced relay operated control systems in almost

every field. The functionality of the PLC has evolved over the years to include sequential

relay control, motion control, process control, distributed control systems and

networking. The data handling, storage, processing power and communication

capabilities of some modern PLCs are approximately equivalent to desktop computers.

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Therefore, the applications of plc are widespread in industries, and a lot more

applications can be developed in accordance to the demands of the process.

2.6 BASIC COMPONENTS OF PROGRAMMABLE CONTROL

SYSTEMS:

There are four main components of a programmable control system: 2.6.1 Controller:

A controller is the brain of a programmable control system. It is a solid state device,

similar to a computer, with user- programmable memory and a central processor.

Controllers perform the following functions:

1. I/O control

2. Logic

3. Timing

4. Report generation

5. Communications

6. Data manipulation

Fig 2.2: A control logix controller

2.6.2 Input/output system:

An I/O system consists of the following components:

Key switch

Locking tab

LEDs

Door

Battery label

Backplane Connector

Battery

Serial port

Labels

Locking tab

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1. I/O modules, which are part of the programmable control system (Modules are

interchangeable plug ins within a larger assembly).

2. I/O devices, which are a part of the process/machine.

Fig 2.3 : An I/O System of a control logix controller

An I/O system sends input and output information between a controller and process/

machine.

• Input device: A device, such as a pushbutton, that supplies signal to an input module

and controller.

• Output device: A device that is actuated or energized by a controller.

2.6.3 Programming System:

A programming system is used to program and monitor the operation of a controller. It is

composed of a programming device (personal computer or work station) and software.

2.6.4Communication network:

Fig 2.4: A control network

I/O Devices I/O Modules

I/O System

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A communications network is the physical connection between a series of components or

devices. This connection is used to transfer data between the components, such as a

computer and a controller, using a cable.

2.7 OPERATIONS IN PLC:

Operations in a plc controlled system are very diverse and varied. Here we are discussing

only a few important operations, namely, generation of input signal, generation of output

signal, and a brief understanding of operation of plc. The block diagram of plc is as

shown (Fig2.5).

Fig 2.5 : Block diagram of plc

2.7.1 Generation of input signal:

Fig 2.6: Diagram Showing Energized input terminal X1

Inside the PLC housing, connected between each input terminal and the Common

terminal, is an opto-isolator device (Light-Emitting Diode) that provides an electrically

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isolated "high" Logic signal to the computer's circuitry (a photo-transistor interprets the

LED's light) when there is 120 VAC power applied between the respective input terminal

and the Common terminal. An indicating LED on the front panel of the PLC gives visual

indication of an "energized" input.

2.7.2. Generation of output signal:

Fig 2.7: Diagram Showing Energized output terminal Y1

Output signals are generated by the PLC's computer circuitry activating a switching

device (transistor, TRIAC, or even an electromechanical relay), connecting the "Source"

terminal to any of the "Y-" labeled output terminals. The "Source" terminal,

correspondingly, is usually connected to the L1 side of the 120 VAC power source. As

with each input, an indicating LED on the front panel of the PLC gives visual indication

of an "energized" output. In this way, the PLC is able to interface with real-world devices

such as switches and solenoids. The actual logic of the control system is established

inside the PLC by means of a computer program. This program dictates which output

gets energized under which input conditions. Although the program itself appears to be a

ladder logic diagram, with switch and relay symbols, there are no actual switch contacts

or relay coils operating inside the PLC to create the logical relationships between input

and output. These are imaginary contacts and coils, if you will. The program is entered

and viewed via a personal computer connected to the PLC's programming port.

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2.7.3. Operation of PLC:

Consider the following circuit and PLC program:

-------[ ]--------------( )---

run motor

Fig 2.8: Operation of PLC (input is not actuated)

When the pushbutton switch is not actuated, no power is sent to the X1 input of the PLC.

Following the program, which shows a normally open X1 contact in series with a Y1

coil, no "power" will be sent to the Y1 coil. Thus, the PLC's Y1 output remains de-

energized, and the indicator lamp connected to it remains dark.

If the pushbutton switch is pressed, however, power will be sent to the PLC's X1 input.

Any and all X1 contacts appearing in the program will assume the actuated (non-normal)

state, as though they were relay contacts actuated by the energizing of a relay coil named

"X1". In this case, energizing the X1 input will cause the normally-open X1 contact will

"close," sending "power" to the Y1 coil. When the Y1coilof the program "energizes," the

real Y1 output will become energized, lighting up the lamp connected to it.

It must be understood that the X1 contact, Y1 coil, connecting wires, and "power"

appearing in the personal computer's display are all virtual. They do not exist as real

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electrical components. They exist as commands in a computer program - a piece of

software only -that just happens to resemble a real relay schematic diagram.

Fig 2.9: Operation of PLC (input is actuated)

Equally important to understand is that the personal computer used to display and edit the

PLC's program is not necessary for the PLC's continued operation. Once a program has

been loaded to the PLC from the personal computer, the personal computer may be

unplugged from the PLC, and the PLC will continue to follow the programmed

commands. I include the personal computer display in these illustrations for your sake

only, in aiding to understand the relationship between real-life conditions (switch closure

and lamp status) and the program's status ("power" through virtual contacts and virtual

coils). The true power and versatility of a PLC is revealed when we want to alter the

behavior of a control system. Since the PLC is a programmable device, we can alter its

behavior by changing the commands we give it, without having to reconfigure the

electrical components connected to it. For example, suppose we wanted to make this

switch-and-lamp circuit function in an inverted fashion: push the button to make the lamp

turn off, and release it to make it turn on. The "hardware" solution would require that a

normally closed pushbutton switch be substituted for the normally-open switch currently

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in place. The "software" solution is much easier: just alter the program so that contact X1

is normally-closed rather than normally-open.

The example here taken, is to briefly explain the operation of plc. Programming of plc

will dealt in detail in the chapter 4.

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CHAPTER 3

STARTING UP WITH LOGIX 5000 SYSTEM

3.1 LOGIX 5000 SYSTEM:

3.1.1 Logix Control Engine:

The operating system common to all Logix5000 controllers. It is available in several

platforms or physical formats:

• ControlLogix®: high performance, multi-controller system in a modular chassis

format.

• FlexLogix™: System for distributed control. Control platform is located close to the

machine.

• CompactLogix™: Small modular system from small stand-alone to medium-sized

connected systems.

• DriveLogix™: System for distributed drive control.

• SoftLogix™: System that combines control, information and visualization on an open

control system such as computer.

Fig 3.1: Various logix 5000 platforms,from left to right, DriveLogix, FlexLogix,

CompactLogix, ControLogix,SoftLogix

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3.2 LOGIX 5000 DISCIPLINES:

The Logix 5000 family of controller is capable of supporting the following control

disciplines:

• Sequential Control: e.g. conveyor systems

• Motion Control: e.g. labeling, packaging, picking and placing

• Drive Control: e.g. mixing, winding

• Process Control: e.g. batching, filling

• Safety Control: e.g. light curtains

Now, let us discuss control logix platform in detail:

3.3 CONTROL LOGIX PLATFORM AND COMPONENTS:

3.3.1 ControlLogix:

• A high performance, multi-controller system in a modular chassis format.

• Enable easy integration with existing systems like PLC-5®, SLC™.

• Is capable of high-speed communications and data transfers.

• Allow multiple controllers, I/O modules and communication modules in any order

and location within the chassis.

Chassis

I/O and Controllers Communication modules

Fig 3.2 ControlLogix System

3.3.2 ControlLogix Chassis:

• Chassis: A hardware assembly that houses devices such as controllers, I/O and

communication modules

Power Supply

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• Slots: Openings in a chassis that holds individual modules.

• ControlLogix Chassis Sizes: 4-slot, 7-slot, 10-slot, 13-slot, 17-slot.

• Slots are numbered from left to right starting with 0.

• 1756(ControlLogix) modules are slot-independent.

Fig 3.3 ControlLogix Chassis

3.3.3 ControlLogix Backplane:

• Also called ControlBus backplane, it is a printed circuit board at the back of chassis

that provides electrical interconnection between modules.

• The backplane allows data to be multicast, i.e., an input module sends data once that

is received by multiple controllers simultaneously.

Fig 3.4 ControlLogix Backplane

3.3.4 ControlLogix Controller:

• It is a 32-bit controller that combines logic and data in modular memory.

• All controllers have two main internal components:

chassis

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a.)Central Processing unit (CPU): The decision-making component that executes the

program stored in memory.

b.) Memory: A group of circuit elements where programs and data are stored.

• A battery will maintain controller memory when power is turned off.

• There are also controllers that support non-volatile memory.

3.3.5 ControlLogix I/O Modules:

• ControlLogix I/O Modules (1756-I/O) provide input and output capability to span

many applications, from high-speed sequential to process control.

• These I/O modules offer following capabilities:

a.) Easy configuration using a wizard.

b.) Electronic keying (module identification)

c.) Scaling of analog values

d.) Diagnostics (depending on modules)

• The wiring from the process/machine is connected to I/O modules through:

a.) RTB (Removable Terminal block): A field wiring connector for I/O modules.

Field wiring is connected to an RTB rather than directly to a module terminal block.

b.) IFM (Prewired Interface module): a field wiring arm that uses prewired/ factory-

wired cable to connect to an I/O module.

• RTBs and IFMs allow for easy replacement or interchanging of I/O modules without

rewiring them

.

3.4 CREATING AND MODIFYING AN RSLOGIX 5000 PROJECT:

A Project/Project file is an RSLogix 5000 software file that stores all programming an

configuration information for a Logix5000™ controller .RSLogix 5000 project files have

the extension .acd. Components used to organize a project and direct the execution are:

1. Task: A task triggers the execution of its scheduled programs

Task Type Usage Icon

Continuous A task that runs continuously but can

be interrupted by periodic or event

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tasks.

Periodic A task that executes regularly at a

user-specified rate.

Event A task is triggered only when a

specific event occurs.

Table 3.1 Task Types

2. Program: A set of related routines and tags.

• Scheduled program

• Unscheduled program

Fig3.5 Controller Organizer

3. Routines: A set or sequence of programming code executed as a block.

• MainRoutine

• Subroutine

• FaultRoutine

3.5 TRANSFERRING A PROJECT FILE TO LOGIX5000

CONTROLLER:

• Upload: Transfer a copy of project file from controller to computer over a network.

• Download: Transfer a copy of project file from computer to controller over a

network.

• Online: Viewing or editing a project file that is active in controller.

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• Offline: Viewing or editing a copy of project file that is in computer only.

3.5.1 RSLinx Classic Software:

It is a software and server used to create a dedicated path between PC and PLC. RSWho

is the network browser interface for RSLinx Classic software that shows all active

network connections. Communication can be initiated by WhoActive dialog box:

3.5.2 Selecting and changing a Controller’s Operating Mode:

Logix5000 controllers have 3 keyswitch positions labeled on front of controller :

• Run

• Program

• Remote

Fig 3.6 RSLinx Classic main window

Fig3.7 WhoActive dialog box

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The mode of plc con be changed manually using keyswitch, the LEDs on the controller

glow accordingly. The table given below explains various modes of operation of plc.

Keyswitch Position Available Controller Modes

Run Run Mode: Controller actively controls

process. Projects can’t be edited in Run

mode.

Program Program Mode: Programming language

is not executing, I/O not controlled and

editing operations are available.

Remote Remote Run Mode: similar to Run mode

except you can edit project online.

Remote Program Mode: similar to

Program mode.

Remote Test Mode: code is executing,

I/O is not controlled and limited editing

operations are available.

Table 3.2 Controller modes

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CHAPTER 4

PROGRAMMING OF PLC

Early PLCs, up to the mid-1980s, were programmed using proprietary programming

panels or special-purpose programming terminals, which often had dedicated function

keys representing the various logical elements of PLC programs. Programs were stored

on cassette tape cartridges. Facilities for printing and documentation were very minimal

due to lack of memory capacity. More recently, PLC programs are typically written in a

special application on a personal computer, and then downloaded by a direct-connection

cable or over a network to the PLC. The very oldest PLCs used non-volatile magnetic

core memory but now the program is stored in the PLC either in battery-backed-up RAM

or some other non-volatile flash memory. Early PLCs were designed to be used by

electricians who would learn PLC programming on the job. These PLCs were

programmed in "ladder logic", which strongly resembles a schematic diagram of relay log

Fig4.1: Few examples depicting programming of PLC

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IEC 61131-3 currently defines five programming languages for programmable control

systems: function block diagram (FBD), ladder diagram (LD), structured text (ST; similar

to the Pascal programming language), instruction list (IL; similar to assembly language)

and sequential function chart (SFC). These techniques emphasize logical organization of

operations. Now, let us discuss ladder diagram in detail.

4.1 LADDER DIAGRAM:

Ladder logic is a method of drawing electrical logic schematics. It is now a graphical

language very popular for programming Programmable Logic Controllers (PLCs). It was

originally invented to describe logic made from relays. The name is based on the

observation that programs in this language resemble ladders, with two vertical "rails "and

a series of horizontal "rungs" between them. A program in the ladder logic, also called

ladder diagram is similar to a schematic for a set of relay circuits.

An argument that aided the initial adoption of ladder logic was that a wide variety of

engineers and technicians would be able to understand and use it without much additional

training, because of the resemblance to familiar hardware systems. (This argument has

become less relevant given that most ladder logic programmers have a software

background in more conventional programming languages, and in practice

implementations of ladder logic have characteristics — such as sequential execution and

support for control flow features — that make the analogy to hardware somewhat

imprecise.)

Ladder logic is widely used to program PLCs, where sequential control of a process or

manufacturing operation is required. Ladder logic is useful for simple but critical control

systems, or for reworking old hardwired relay circuits. As programmable logic

controllers became more sophisticated it has also been used in very complex automation

systems.

Ladder logic can be thought of as a rule-based language, rather than a procedural

language. A "rung" in the ladder represents a rule. When implemented with relays and

other electromechanical devices, the various rules "execute" simultaneously and

immediately. When implemented in a programmable logic controller, the rules are

typically executed sequentially by software, in a loop. By executing the loop fast enough,

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typically many times per second, the effect of simultaneous and immediate execution is

obtained. In this way it is similar to other rule based languages, like spreadsheets or SQL.

However, proper use of programmable controllers requires understanding the limitations

of the execution order of rungs.

4.2 BASIC INSTRUCTIONS FOR LADDER LOGIC:

Few frequently used instructions in ladder logic are listed in table 4.1.

INSTRUCTION PURPOSE

MNEUMONIC LABEL NAME

XIC Examine if closed Examines a bit for an On

condition

XIO Examine if open Examines a bit for an Off

condition

OTE Output Energize Turns a bit On or Off.

OTL AND OTU Output Latch and

Output Unlatch

OTL turns a bit on when

the rung is executed, and

this bit retains its state

when the rung is not

executed or a power cycle

occurs. OTU turns a bit off

when the rung is executed,

and this bit retains its state

when the rung is not

executed or when power

cycle occurs.

OSR One Shot Rising Triggers a on time event.

TON

Timer On Counts time base intervals

when the instruction is

true.

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TOF Timer Off- Delay Counts time base

intervals when the

instruction is false.

RTO Retentive Timer Counts time base intervals

when the instruction is true

and retains the

accumulated value when

the instruction goes false

or when power cycle

occurs.

CTU Count Up Increments the

accumulated value at each

false-to true transition and

retains the accumulated

value when the instruction

goes false or when power

cycle occurs.

CTD Count Down Decrements the

accumulate value at each

false-to true transition and

retains the accumulated

value when the instruction

goes false or when power

cycle occurs.

RES Reset Resets the accumulated

value and status bits of a

timer or counter. Do not

use with TOF timers.

Table 4.1: Few commonly used instructions of ladder logic.

In the next chapter we will see some practical industry problems solved using ladder

logic.

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CHAPTER 5

WORKED OUT EXAMPLES

5.1 PROBLEM 1: OVERLOADING OF CONVEYOR:

Fig 5.1. Bottling plant conveyor

In a bottling industry, an alarm system is to be devised such that if the conveyor has more

than ten bottles, the alarm will glow up to indicate the overloaded conveyor. Here, there

are two sensors at the entry and exit of the conveyor. Thus, the number of bottles present

on the conveyor can be determined.

This problem is solved using ladder logic programming in the following pages.

SENSOR 2

SENSOR1

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CHAPTER 6

NETWORKING OF PLC

Network solutions allow connecting various automation products to each other and to the

rest of the enterprise. A proper interaction between devices, communication interfaces

physical media and connecting products is possible only if correct network is chosen for

communication.

The most commonly used network solutions are:

1. EtherNet/IP

2. ControlNet

3. DeviceNet

6.1 ETHERNET/IP:

The EtherNet/IP Network provides plant-wide network systems using open, industry-

standard networking technologies. It enables real-time control and information in

discrete, continuous process, batch, safety, drive, motion, and high availability

applications. The EtherNet/IP network connects devices such as motor starters and

sensors to controllers and HMI devices and on into the enterprise. It supports non-

industrial and industrial communications on a common network infrastructure.

Capability Description

Topology

• All traditional Ethernet options for star, tree, switch ring, and

other high-availability topologies

• Many automation devices include two physical Ethernet ports and

follow the ODVA DLR (Device Level Ring) standard to support

linear and ring topologies, without the need for external Ethernet

switches

Distance • 100 m between devices for copper twisted-pair wiring

• Fiber cabling permits longer distances (design dependent)

Capacity • Unlike older networks, no practical limits on capacity

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• Constrained only by communication limitations of devices on the

network

• For a quick estimate of capacity for your application, use

the EtherNet/IP Capacity Estimator tool

Performance

• I/O update rates of <1 ms

• Sub-millisecond precision motion control and time

synchronization

• Exceeds mechanical and device limitations for most precision

motion control applications

• Performance prioritization for motion control and real-time I/O

Segmentation

• Lets you divide a large network into smaller networks for security

or management efficiency via standard segmentation methods

such as subnets and VLANs

• Enables selective routing of real-time control and other traffic

across segments

Table 6.1: Capabilities of EtherNet/IP

6.2 CONTROLNET:

The ControlNet network is an open control network that meets the demands of real-time,

high-throughput applications. ControlNet supports controller to controller interlocking

and real-time control of I/O, drives and valves. It also provides control networking in

discrete and process applications including high-availability application


Topology

• Trunkline, dropline

• Star

• Tree

• Ring

Capacity • Each ControlNet network supports up to 99 nodes

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• Use repeaters to add more nodes

• Some Allen-Bradley® controllers support multiple ControlNet

networks

Connections

• Scheduled or unscheduled

• You indirectly determine the number of connections the controller

uses by configuring the controller to communicate with other

devices in the system

Distances

• Maximum distance depends on the number of nodes on the

network

• Use repeaters to gain more distance

Table 6.2: Capabilities of ControlNet

6.3 DEVICENET:

The DeviceNet Network provides open, device-level control and information networking

for simple industrial devices. It supports communication between sensors and actuators

and higher-level devices such as programmable controllers and computers. With power

and signal in a single cable, it offers simple and cost-effective wiring options.


Topology Trunkline, dropline

Capacity

Each DeviceNet network supports up to 64 nodes; 62 nodes are available for

devices

Most Rockwell Automation controllers support multiple DeviceNet

networks

Distances Daisy-chain or branch nodes along droplines up to a maximum of 6 m (20 ft)

from the trunk

Table 6.3: Capabilities of DeviceNet

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VARIABLE FREQUENCY DRIVE

A Variable Frequency

A.C motor by controlling the frequency of electric power supplied to the motor.

Induction motors have been used in the past mainly in applications requiring a constant

speed. Variable speed applications

Thyristors, Power Tra

induction motor drives. The main drawback of dc motors

commutator and brushes, which

I.Ms, particularly squirrel

efficient, require lower maintenance and can operate in dirty and explosive environments.

Variable speed induction motor drives are gene

cranes, conveyers etc.

Fig

7.1 OPERATING PRINCIP

Variable frequency drives operate under the principle that the synchronous speed of an

AC motor is determined by the frequency of the AC supply and the number of poles in

the stator winding, according to the relation:

Where,RPM = Revolutions per minute

f = AC power frequency (Hertz)

onics Engineer

CHAPTER 7


requency Drive (VFD) is a system for controlling the rational speed of an


nduction motors have been used in the past mainly in applications requiring a constant

Variable speed applications were dominated by dc drives. Availability of

Thyristors, Power Transistors, IGBT allowed the development of variable speed

induction motor drives. The main drawback of dc motors

commutator and brushes, which required frequent maintenance.

I.Ms, particularly squirrel-cage motors are rugged, inexpensive, lighter, smaller, more


Variable speed induction motor drives are generally used in number of applications like

cranes, conveyers etc.

Fig 7.1 Rockwell PowerFlex VFD Control Panel

.1 OPERATING PRINCIP LE OF VARIABLE FREQU


otor is determined by the frequency of the AC supply and the number of poles in

the stator winding, according to the relation:

Where,RPM = Revolutions per minute

f = AC power frequency (Hertz)

36


(VFD) is a system for controlling the rational speed of an


nduction motors have been used in the past mainly in applications requiring a constant

dominated by dc drives. Availability of

allowed the development of variable speed

induction motor drives. The main drawback of dc motors was the presence of

cage motors are rugged, inexpensive, lighter, smaller, more


rally used in number of applications like

Rockwell PowerFlex VFD Control Panel

LE OF VARIABLE FREQU ENCY DRIVE


otor is determined by the frequency of the AC supply and the number of poles in

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p = Number of poles (an even number)

Synchronous motors operate at the synchronous speed determined by the above equation.

The speed of an induction motor is slightly less than the synchronous speed.

7.2 VFD SYSTEM DESCRIPTION:

A VFD system consists of an AC motor, a controller and an operator interface as shown

in figure.

VFD Motor: VFD system consists of 3

are preferred than synchronous motor.

VFD Controller: It is a solid state electronic power conversion device which first

converts AC power in to DC intermediate by using bridge rectifier. This DC power is

then converted in to quasi

VFD Operator Interface:

to adjust the operating speed.

onics Engineer

p = Number of poles (an even number)



.2 VFD SYSTEM DESCRIPTION:

Fig 7.2 Basic Structure of VFD


VFD system consists of 3-Φ induction motor. Mostly, Induction motors

are preferred than synchronous motor.

It is a solid state electronic power conversion device which first


then converted in to quasi-sinusoidal AC power using an inverter circuit.

VFD Operator Interface:-An operator interface is used to start and stop the motor and

to adjust the operating speed.

37




induction motor. Mostly, Induction motors

It is a solid state electronic power conversion device which first


sinusoidal AC power using an inverter circuit.

erator interface is used to start and stop the motor and

ANIL MAURYA 38


LCD HIM: This VFD operating interface consists of an keypad, display, indication

lights and meters to provide information about the operation of the drive. Motor can be

controlled and monitored on computer by using an serial communication part on VFD

operator interface.

7.3 VFD OPERATION:

• When VFD starts, the applied frequency and voltage are increased at a controlled rate

or ramped up to accelerate the load without drawing excessive current.

• This starting method allows a motor to develop 150% of its rated torque while

drawing only 50% of its rated current.

• When a motor is switched ON at full voltage, initially it has at least 300% of its rated

current. While it produce less then 50% of its rated torque.

• As load accelerates, the available torque usually decrease very little and then

increases to a peak while the current remains very high until the motor get full speed.

• By using VFD system, the frequency & voltage applied to the motor are ramped

down at a controlled rate.

• When frequency becomes zero, the motor is shut-off. A small amount of breaking

torque is available to help decelerate the load.

• Thus the speed of AC motor can be controlled by varying frequency of power applied

to the motor.

Fig 7.3 – VFD System

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CHAPTER 8

SCADA

SCADA stands for “Supervisory Control And Data Acquisition”. SCADA refers to an

industrial control system: a computer system monitoring and controlling a process. The

process can be industrial, infrastructure or facility based as described below:

Industrial Process: It includes manufacturing, production, power generation, fabrication

and refining process which may be in continuous, batch, repetitive or discrete modes.

Infrastructure Process: It includes water treatment and distribution, wastewater collection

and treatment, oil and gas pipelines, electrical power transmission and distribution, and

large communication systems.

Facility Process: It occurs both in public facilities and private ones, including buildings,

airports, ships and space stations. They monitor and control HVAC, access and energy

consumption.

An SCADA System usually consists of the following subsystems:

1.) Human-Machine Interface (HMI): The apparatus which presents the data to a

human operator, and through this, the human operator monitors and controls the process.

2.) A supervisory (computer) system, gathering (acquiring) data on the process and

sending commands (control) to the process.

3.) Remote Terminal Units (RTU) connecting to sensors in the process, converting

sensor signals to digital data and sending digital data to the supervisory system.

4.) Programmable Logic Controllers (PLC) used as field devices because they are

more economical, versatile, flexible and configurable than special-purpose RTUs.

5.) Communication infrastructure connecting the supervisory system to the RTUs.

8.1 SYSTEM CONCEPTS:

• The term SCADA usually refers to centralized systems which monitor and control

entire sites, spread out over large areas.

• Most control actions are performed automatically by Remote Terminal Units (RTU)

or by Programmable Logic Controllers (PLCs).

ANIL MAURYA 40


• Host control functions are usually restricted to basic overriding or supervisory level

intervention.

• Ex: A PLC may control the flow of cooling water as part of an industrial process, but

the SCADA system may allow operators to change the set points for the flow, and

enable alarm conditions, such as loss of flow and high temperature, to be displayed

and recorded. The feedback control loop passes through the RTU or PLC, while the

SCADA system monitors the overall performance of the loop

• Data Acquisition begins at the RTU or PLC level and includes meter readings and

equipment status reports that are communicated to SCADA as required.

• Data is then compiled and formatted in such a way that a control room operator using

the HMI can make supervisory decisions to adjust or override normal RTU (PLC)

controls.

Fig 8.1 – SCADA Concepts

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8.2 ALARM:

• An important part of most SCADA implementation is alarm handling.

• The system monitors whether certain alarm conditions are satisfied to determine

when an alarm event has occurred.

• Once an alarm event has been detected, one or more actions are taken such as the

activation of one or more alarm indicators, and perhaps the generation of email or text

messages so that management or remote SCADA operators are informed.

• In many cases, a SCADA operator may have to acknowledge the alarm event.

• Alarm conditions can be:

� Explicit - for example, an alarm point is a digital status point that has either the

value NORMAL or ALARM that is calculated by a formula based on the values

in other analog and digital points.

� Implicit: the SCADA system might automatically monitor whether the value in

an analog point lays outside high and low limit values associated with that point.

• Examples of alarm indicators include a siren, a pop-up box on a screen, or a colored

or flashing area on a screen. In each case, the role of the alarm indicator is to draw

the operator's attention to the part of the system 'in alarm' so that appropriate action

can be taken.

• In designing SCADA systems, care is needed in coping with a cascade of alarm

events occurring in a short time, otherwise the underlying cause (which might not be

the earliest event detected) may get lost in the noise.

ANIL MAURYA 42


CONCLUSION

• Any control system goes through four stages from conception to a working plant. A

PLC system brings advantages at each stage. The first stage is design; the required

plant is studied and the control strategies decided. With conventional systems design

must be complete before construction can start. With a PLC system all that is needed

is a possibly vague idea of the size of the machine and the I/O requirements (how

many inputs and outputs). The input and output cards are cheap at this stage, so a

healthy spare capacity can be built in to allow for the inevitable omissions and future

developments.

• Next comes construction. With conventional schemes, every job is a one-off with

inevitable delays and costs. A PLC system is simply bolted together from standard

parts. During this time the writing of the PLC program is started (or at least the

detailed program specification is written).

• The next stage is installation, a tedious and expensive business as sensors, actuators,

limit switches and operator controls are cabled. A distributed PLC system using serial

links and pre-built and tested desks can simplify installation and bring huge cost

benefits. The majority of the PLC program is written at this stage.

• Finally comes commissioning, and this is where the real advantages are found. No

plant ever works first time. Human nature being what it is, there will be some

oversights. Changes to conventional systems are time consuming and expensive.

Provided the designer of the PLC system has built in spare memory capacity, spare

I/O and a few spare cores in multi core cables, most changes can be made quickly and

relatively cheaply. An added bonus is that all changes are recorded in the PLC

program and commissioning modifications do not go unrecorded, as is often the case

in conventional systems.

• There is an additional fifth stage, maintenance, which starts once the plant is working

and is handed over to production. All plants have faults, and most tend to spend the

majority of their time in some form of failure mode. A PLC system provides a very

powerful tool for assisting with fault diagnosis. A plant is also subject to many

changes during its life to speed production, to ease breakdowns or because of changes

ANIL MAURYA 43


in its requirements .A PLC system can be changed so easily that modifications are

simple and the PLC program will automatically document the changes that have been

made.

• SCADA system for controls ensures a common framework not only for the

development of the specific applications but also for operating the detectors.

Operators experience the same "look and feel" whatever part of the experiment they

control. However, this aspect also depends to a significant extent on proper

engineering.

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REFERENCES

1) www.rockwellautomation.com

2) E. A. Parr, Industrial Control Handbook, Industrial Press Inc., 1999 ISBN 0-8311-

3085-7.

3) "The father of invention: Dick Morley looks back on the 40th anniversary of the

PLC". Manufacturing Automation. 12 September 2008.

4) W. Bolton, Programmable Logic Controllers, Fifth Edition, Newnes, 2009 ISBN

978-1-85617-751-1, Chapter 1.

5) Gregory K. McMillan, Douglas M. Considine (ed), Process/Industrial Instruments

and Controls Handbook Fifth Edition, McGraw-Hill, 1999 ISBN 0-07-012582-1

Section 3 Controllers.

6) Novak, Peter. "The Basics of Variable-Frequency Drives". EC&M. Retrieved

Apr. 18, 2012.

7) Boyes, Walt (18 August 2009). "Back to Basics: SCADA". Automation TV:

Control Global - Control Design.

8) Boyer, Stuart A. (2010). SCADA Supervisory Control and Data Acquisition.

USA: ISA - International Society of Automation. p. 179. ISBN 978-1-936007-09-

7.

9) "External SCADA Monitoring". Epiphan Case Studies. Epiphan Systems Inc.

Retrieved 2 May 2012.

10) "Industrial Security Best Practices". Rockwell Automation. Retrieved 26 Mar

2013.

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