PROGRAMMABLE LOGIC CONTROLLER

&

AUTOMATION SYSTEM

INDUSTRIAL TRAINING REPORT

Submitted to

RAJVI GANDHI PRAUYOGIKI VISHWAVIDYALAYA,

BHOPAL

Submitted in partial fulfillment of the

Requirement for the award of

Degree of Bachelor of Engineering in

Electronics & Communication Engineering

2014-2015

Submitted To: Submitted By:

Mr. Sourabh Dongre Sumit Patidar

Head of Department 0817EC111070

Dept. of Electronics & Communication Engineering

Rishiraj Institute of Technology, Indore

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DECLARATION

I hereby declare that the Industrial Training Report entitle “Programmable

Logical Controller & Automation System” is an authentic record of my own as

requirement of 25 days Industrial Training during from 06th June to 03rd July for award of

degree of Bachelor of Engineering Department of Electronics & Communication Engineering

RISHIRAJ INSTITUTE OF TECHNOLOGY under the guidance of Mr. Bhupendra Singh

Thakur.

Sumit Patidar

0817EC111070

Date:

Certified that the above statement made by the student is correct to the best of our knowledge

and belief.

Signatures

Examined by:

Mr. Sourabh Donger

(HOD, ECE Dept)

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Acknowledgements

First of all we would like to express our gratitude to the “Robotronix Engineering

Tech Pvt. Ltd”. For providing Opportunity to me to pursue the engineering training as a

partial fulfillment of the requirement for the degree of Bachelor of Engineering.

Throughout this training we are very fortune to be blessed with the guidance and

encouragement from our mentor, Mr. Bhupendra Singh Thakur He gave us good knowledge

about the plc working and it internal design of and how a plc works in industry.

In during the training period we learn about the PLC and Automation system,

programming of plc, different type of plc manufactures company, hardware and software of

plc.

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CONTENTS

1. Introduction……………………………………………………………………………….7

1.1 Programmable Logic Controller (PLCs)…………………………….………….7

1.2 What is PLC…………………………………………………………………….8

1.3 History of PLCs…………………………………………………………………10

2. Functional Descriptions………………………………………………………………....11

2.1 Input System…………………………………………………………………….11

2.2 Outputs………………………………………………………………………….13

2.3 Control Process or unit………………………………………………………….14

2.4 Memory unit…………………………………………………………………….15

2.5 Programmable unit………………………………………………………………15

3. General PLCs Architecture …………………………………………………………….16

3.1 Scan Cycle of PLCs…………………………………………………………......17

4. Type of PLCs…………………………………………………………………………….18

4.1 Based on size…………………………………………………………………….18

4.2 Classification according to its output working………………………………….19

5. Sensor……………………………………………………………………………………20

5.1 Need of Senor……………………………………………………………………20

5.2 Actuator………………………………………………………………………….20

5.3 Difference between Actuator and Sensor………………………………………..20

6. Data Types………………………………………………………………………………21

7. Memory Types…………………………………………………………………………..22

8. Concept of Relay Functioning………………………………………………………….23

8.1 What is relay? …………………………………………………………………...23

8.2 Why is relay used? ………………………………………………………………23

8.3 Relay Logic………………………………………………………………………23

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9. Sinking and Sourcing……………………………………………………………………24

9.1 Output Sinking and Sourcing device…………………………………………..24

9.2 Input Sinking and Sourcing device…………………………………………….26

9.3 Latching………………………………………………………………………..28

10. S7-200 CPU Description………………………………………………………………28

11. Programming Language & Technique………………………………………………30

11.1 Maintenance and Troubleshooting…………………………………………………30

11.2 Concept of an S7-200 Programming………………………………………...30

11.2.1 Concept of S7-200 programming Language & Editor…………………31

11.3 Statement list editor…………………………………………………………31

11.4 Ladder programming………………………………………………………...32

11.4.1 Ladder logic editor……………………………………………..............32

11.4 Functional Block diagram…………………………………………………...32

12. Some program make during training……………………………………………….33

13. Reference……………………………………………………………………………...35

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1. Introduction:

1.1 Programmable Logic Controllers (PLCs):

A Programmable Logic Controller (PLC) is a specialized computer like device like device

used to replace banks of electromagnetic relays in industrial process control. The PLC is also

knows as a programmable of controller (PC). The title “PLC” for programmable controller

could be confused in common usage with “PC” used to mean personal computer. To avoid

this confusion we shall refer to the programmable controller as a programmable logic

controller or PLC.

You can think of the programmable logic controller as a heavy-duty computer system

designed for machine control. Like a general-purpose computer, the plc is based on digital

logic and can be field-programmed .The programming language is a bit different because the

purpose of the PLC is to control machine. The PLC is used to time and sequence function that

might be required in to control machines. The PLC is used to time and sequence function that

might be required in assembly lines, robots, and chemical processing. It is designed to deal

with the harsh condition of the industrial environment. Some of the physical environment

problem could include vibration and shock, dirt, and vapors, and temperature extremes. Some

input device includes limit and pressure switches, temperature and optical sensor, and analog-

to-digital converts (ADCs). Some output device values, motors and cylinders, and Digital-to-

Analog convertors (DAC).

Before the advent of solid-state logic circuit systems were designed and build exclusive ly

around electronic mechanical relays. Relays are far from obsolete in modern design, but have

been replaced in many of their former roles as logics-level control device, relegated most

often to those applications demanding high current and or high voltage switching.

System and processes requiring “on/off” control abound in modern commerce and industry,

but such control system are rarely built from either electro mechanical relays or discrete

logics gates. Instead, digital computers fill the need, which may be programmed to do a

variety of logic functions.

In the late 1960’s an American company named Bedford Associate released a computing

device they called the MODICON Digital Controller, and later became the name of a

company division devoted to the design, manufacture, and sale of these special-purpose

control computes. Other engineering firms developed their own version of this device, and it

eventually came to be known in non-proprietary terms as a PLC, or Programmable Logic

Controller. The purpose of a PLC was to directly replace electro mechanical relays as logic

elements, substituting instead a solid–state digital computer with a stored program, able to

emulate the interconnection of many relays to perform certain logical task.

A PLC has many “input” terminals, through which it interprets “high” and “low” logical

states from sensor and switches. It also has many output terminals, through which it output

“high” and “low” signal to power light, solenoids, contactors, small motors, and other devices

leading themselves to on/off control. In an effort to make PLC easy to program, their

programming language was designed to resemble ladder logic diagrams. Thus, an industrial

electrician engineer accustomed to reading ladder logic schematics would feel comfortable

programming a PLC to perform the same control functions.

PLC are industrial computers, and as such their input and output signals are typically 120

volts AC, just like the electro mechanical control relays they were designed to replace.

Although some PLC has the ability to input and output low-level DC voltage signal of the

magnitude used in logic gate circuits, this the exception and not the rule.

1.2 What is a PLC?

A Programmable Logic Controller (PLC) is an industrial computer control system that

continuously monitors the state of input device and makes decision based upon a custom

program to control the state of output devices.

Almost any production line, machine function, or process can be greatly enhances using this

type of control system. However, the biggest benefit in using a PLC is the ability to change

and replicate the operation or process while collecting and communication vital information.

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Another advantage of PLC system is that it is modular. That is, you can mix and match the type of

Input and Output device to best suit your application

According to NEMA (National Electrical Manufacture Association)

”PLC is a digitally operated electronic system, designed specially for the use in industrial

environment, which use programmable memory for internal storage of user oriented instruction for

implementing specific function such as logic, sequencing, timing, counting & arithmetic to control,

though digital & analog input &output for various type of machines & processes.”

Both the PLC & its associated peripherals are designed so that they can be easily integrated into an

industrial control system & easily used in all intended functions.

Need for PLC

Hardwired panel were very time consuming to time and debug and change.

The following requirement for computer controller to replace hardware panel.

Solid state not mechanical

East to modify input and output device

Easy programmed and maintained by plant electrician

Be able to function in an industrial environment

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1.3 History of Programmable Logic Controller (PLCs):

1968: Design of PLCs developed for General Motors Corporation to eliminate costly

Scrapping or assembly line relays during model changeovers.

1969: First PLCs manufactured for automotive industry as electronic equivalent of relays.

1971: First application of PLCs outside the automotive industry.

1973: Introduction of “smart” PLCs for arithmetic operations, printer control move, Matrix

operations, CRT interface etc.

1974: Introduction of analog PID (Proportional, integral, derivative) control, which made

possible the accessing of thermocouples, pressure sensor etc.

1975: First use of PLCs in hierarchical configuration as part of an integrated Manufacturing

system.

1977: Introduction of very small PLCs based on microprocessor technology.

1978: PLCs gain wide acceptance, sales approach $ 80 million.

1979: Integration of plant operation through a PLC communication system.

1980: Introduction of intelligent input and output module to provide high speed, accurate

control in positioning applicants.

1981: Data highways enable user to interconnect many PLCs up to 15000 feet from Each

other. More 16-bit PLCs become available. Color graphic CRTs are available from several

suppliers.

1982: Larger PLCs with up to 8192 I/O become available.

1983: “Third party” peripherals, including graphic CRTs, operator’s interface, I/O networks,

panel displays, and documentation packages, become available from many sources.

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2. Functional Description

A programmable controller manufacture by any company has several common function parts.

Figure illustrates a generic PLC architecture.

The diagram shows Power Supply, I/O central processor, memory and programming and

peripheral device subsection. Each is discussed below.

2.1 Input

Input define as real-world signals giving the controller real-time status of process variable.

These signals can be analog or digital, low or high frequency, maintained or momentary.

Typically they are presented to the programmable controller as a varying voltage current or

resistance value. Signal from thermocouples (TCs) and resistance temperature dectors

(RTDs) are common examples of analog signals. Some flow meter and strain gauge provide

variable frequency signals, while pushbuttons, limit switches, or even electro mechanically

relays contacts are familiar example of digital, contact closuer type signals. One additional

type of input signal, the register input, reflect the computer nature of the programmable

controller.

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Inputs are device that supply a signal/data to a PLC. Typical examples of input are 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.”

A discrete input also referred to as a digital input, is that is either in an ON or OFF condition.

Pushbuttons, toggle switch, limit switches, proximity switches, and contact cloures are

examples of discrete sensor which are connected to the PLC discrete input may be referred to

as logic 1 or logic high. In the OFF condition a discrete input may be referred to as logic 0 or

a logic low.

An analog input is a continuous, variable signal. Typically analog inputs may vary from 0 to

20 milliamps, 4 to 20 milliamps, or 0 to 10 volts. In the following example, a level

transmitter monitors the level of liquid in a tank. Depending on the level transmitter, the

signal to the PLC can either increase or decrease as the level increases or decreases.

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2.2 Output

There are three common categories of outputs: Discrete, Register, and Analog. Discrete

output can be pilot light, solenoid valves, or enunciator Windows (lamp box). Register output

can be drive panel meters or displays; analog outputs can drive signals to variable speed drive

or to I/P converters and thus to control values.

Outputs are device that await a signal/data from the PLC to perform their control function

light, horns, motors, and values are all good examples of output devices. These device stay

put, minding their own business until the PLC says, “You need to turn on now” or “you’d

better open up your value a little more, “etc.

A discrete output is an output that is either in an ON or OFF condition. Solenoids, contactor

coils, and lamps are examples of actuator device connected to discrete outputs. Discrete

outputs may also be referred to as digital outputs. In the following example, a lamp can be

turned on or off by the PLC output it is connected to.

An analog output is a continuous, variable signal. The output may be as simple as a 0-10

VDC level that drives an analog meter. Examples of analog meter output are speed, weight,

and temperature. The output signal may also be used on more complex application such as a

current-to-pneumatic transducer that controls an air-operated flow-control value.

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The PLC program is executes as part of a repetitive process referred to as scan. A PLC scan

starts with the CPU reading the status of inputs. The application program is executed using

the status of the inputs. Once the program is completed, the CPU performs internal

diagnostics and communication tasks. The scan cycle ends by updating the outputs, and then

stars over. The cycle time depends on the size of the program, the number of I/Os, and the

amount of communication required.

2.3 Control Processor Unit (Real Time):

The central processor unit (CPU), or central control unit (CCU), perform the tasks necessary

to fulfill the PLC function. Amount these are scanning, I/O bus traffic control, program

execution device communication, special function or data handling execution (enhancement),

and self-diagnostics.

One common way of rating how a PLC perform these task is it scan time> Scan time is

roughly defined as the time it takes for the programmable controller to interrogate the input

device, execute the application program, and provide updated signals to the output devices.

Scan time can vary from 0.1 millisecond 1K (1024) word of logic to more than 50

millisecond per 1K of logic. Therefore, when selecting a programmable controller other

performance factor must be considered. The user should take into account the application as

well as the speed of the controller.

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2.4 Memory unit:

The memory unit of the PLC serves several functions. It is the library where the application

program is store. It is also where the PLC’s executive is stored. An executive program

functions as the operating system of the PLC. It is the program that interprets, manages, and

executes the user’s application program. Finally, the memory unit is the part of the

programmable controller where process data from tables. Typically, an image of these data

tables. Typically, images of these data tables are used by the CPU and, when appropriate,

send to the output modules.

Memory can be volatile or non-volatile. Volatile memory is erased if power is removed.

Obviously this undesirable, and most units with volatile memory provide battery back up to

ensure that there will be no loss of power outage. Non-volatile memory does not change state

on loss of power and is used in cases in which extended power outages or long transportation

time to job site (after program entry) are anticipated.

The basic programmable controller memory element is the word. A word is collection of 4, 8,

16, or 32 bits that is used to transfer data about the programmable controller. As word length

increase more information can be stored in a memory location.

2.5 Programmer Units:

The programmer unit provides an interface between the PLC and the user during program

development, start-up, and troubleshooting. The instruction to be performed during each scan

are coded and inserted into memory with the programmer.

Programmers vary from small hand-held units. These units the size of a large calculator to

desktop standalone intelligent CRT-based units. These units come complete with

documentation, reproducing, I/O status, and on-line and off-line programming ability. Many

PLC manufactures now offer controller model that can use a personal computer as the

programming tool.

Under these circumstance, the manufacture will sell a program for the personal computer that

usually allows the computer that module installed in programmable controller.

Programming units are the liaison between what the PLC understands (words) and what the

engineer desired to occur during the control sequence. Some programmers have the ability to

store programs on other media, including cassette tapes and floppy disks. Another desirable

feature is automatic documentation of the existing program. This is accomplished by a printer

attached to the programmer. With off-line programming the user can write a control program

on the programming unit, then take unit to the PLC in the field and load the memory with

new program, all without removing the PLC. Selection of these feature depends on user

requirement and budget. On-line programming allows caution modification of the program

while the PLC is controlling the process or the machine.

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3. General PLC Architecture:

PLC inputs must convert a variety of logic levels to the 5V dc logic level used on the data

bus. This can be done with circuit similar to those shown below. Basically the circuit

conditions the input to drive an up to coupler. This electrically isolates the external electrical

circuitry from the internal circuitry. Other circuit components are used to guard against

excess or reversed voltage polarity.

PLC output must convert the 5V dc logic levels on the PLC data bus to external voltage

levels. This can be done with circuits similar to those shown below. Basically the circuit uses

an opto coupler to switch external circuitry. This electrically isolated the external electrical

circuitry from the internal circuitry. Other circuit components are used to guard against

excess or reversed voltage polarity.

Advantage of PLC:

Small size

Faster response

Wiring reduced up to 80%

On-line changes

Low Maintenance Cost

Easy for Troubleshooting

Disadvantages of PLC:

Too much work required in connecting wires

Difficulty with change or replacement

Requiring skilful work force finding error

Fixed program application

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3.1 Scan Cycle of PLC

Reading the input: The S7-200 copies the state of the physical input to the process-image

input register.

Execution the control logic in the program: The S7-200 executes the instruction of the

program and stored the value in the various memory areas.

Processing any communication request: The S7-20 perform any task required for

communications.

Executing the control logic the program: The S7-200 ensures that the firmware, the

program memory, and any expansion module are working properly.

Writing to the outputs: The values stored in the process-image output register are written to

physical outputs.

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4. Types of PLC

Programming logic controller (PLCs) has several types: Based on the size of the module and

it can be classified according to is working.

4.1 Based on Size

Micro PLC or Small PLC: It is the simplest PLC with the Power Supply module,

CPU, I/O few modules and communication ports in a single chassis. This PLC types

are usually limited to a few I/O discrete and can be expanded. There are various micro

PLCs on the market today. The vast majority offer analog I/O with just about any

micro PLC, or for that matter PLC in general, when the application required the

monitoring of various analog signals, a separate module is required for each signal.

Examples of this type are CP1H Omron, Siemens S7-200, and Fuji Electric SPB.

Medium PLC or Mini: It is PLC which has CPU module, I/O or communication

ports are separately. Each module is connected by connector or backplane. It has the

capacity more than 2000 I/O. Example of this type are Omron CS1, Siemens S7-300.

Large PLC or Rack: This kind of PLC is nearly equal to the medium one but it has

large I/O capacity and more able to be connected with the higher control system.

Examples of this type are CVM1 Omron Siemens S7-400.

Medium PLC Micro PLC

Large PLC

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4.2 Classified according to its Output working:

Relay based: This type of PLC are used for general purpose application.

Transistor based: This type of PLC are used for High speed application.

SCR based: This type of plc are used for heavy load switching.

Different PLC Manufactures

Siemens

Fatek

Delta

Allen Bradley

Mitsubishi

Omron

ABB

Panasonic

GE Fanuc

LG

Criteria of Choosing PLC

Cost

No. of I/Os

Memory Capacity

Processing Speed of CPU

CPU Capabilities

No. of Timer, Counters

Interface Module

Networking & Communication Facility

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5. Sensor (connected to PLC Input)

A sensor is a device that measures a physical quantity and converts it into signal which can

be read by an observer or by an instrument. For example, a mercury- in-glass thermometer

converts the measured temperature into expansion and contraction of liquid which can be

read on a calibrated glass tube. A thermocouple convert temperature converts temperature to

an output voltage which can be read by a voltmeter. For accuracy, most sensor are calibrated

against know standard. Sensors are two types.

Digital Sensor: Digital sensor have two unique voltage associated them to represent

the two unique voltage associated them to represent the two unique digital states of 0

to 1. These voltages are commonly 0v to 24v but there are many also types.

Ex. IR sensor, Proximity sensor, Hall sensor, PIR sensor

Analog Sensor: Analog sensor are sensor that vary with respect to time.

Ex. Level sensor, Flow sensor, Temperature sensor, Speed sensor.

5.1 Need for Sensors

Sensors are omnipresent. They embedded in our bodies’ automobiles, airplane, cellular

telephone, radio, chemical plant, industrial plant and counter less other application.

5.2 Actuator (Connected to PLC Output)

An Actuator is a mechanical device for moving or controlling a mechanism or system. It is

operate by a source of energy, usually plant and counter less other application.

5.3 Difference between Actuator and Sensor

A sensor controls the variable for example temperature and pressure and transfer a signal to a

indicator or transmitter. The actuator is a machine which knocks a value or other machine in

accordance with control signal transferred to the transducer. The transducer generally

transforms the control signal to a relative air signal which works the actuator with a great

diaphragm opposite springs.

The mainly common actuator of electron-servo or an actuator can be utilized to pull and push

at a force and fixed length (stroke). This actuator of linear that transfer a piston rod to a place

force and fixed length. The can be utilized to transfer controls through variable geometry

example arcs used in conjunction with cranks and rods.

The actuator of hydraulic has an internal piston to the housing. The present is docked on one

end, which forces the rod to en large it. Reversing the pressure of hydraulic will caused the

rod to know back to origin position. The force that it existing is similar to the pressure of

hydraulic times the piston area.

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A senor or detector is tool that a measures a physical quantity and transforms it into a signal

which can be interpreted by a separator or by device. Sensors are utilized in every items for

example touch-sensitive buttons of elevator and lamps which brighten or dim by contacting

the base. There are also numerous application for sensor of which mainly people are not

aware. The appliances consist of machine, cars, aerospace, manufacture, robotics and

medicine.

6. Data Type

There are 4 kind of data type supported by most of PLCs, which are as follows:

Bit (0,1)

Byte (combinational of 8 bits)

Word (combinational of 16 bits)=2B

Double Word (combinational of 32 bits)=2W

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7. Memory Type

There are different memory locations, which is represented by memory type abbreviation.

In Siemens the memory types are:

Description International

Input I

Output Q

Variable Memory V

Internal Memory M

Analog Input AL

Analog Output AQ

Counter C

Special Memory SM

Accumulator AC

Timer T

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8. Concept of Relay Function

8.1 What is relay?

We know that most of the high end industrial application device have relay for their effective

working. Relay are simple switches which are operated both electrically and mechanically.

Relays consist of an electromagnet and also a set contact. The switching mechanism is

carried out with the help of the electromagnet. There is also other operating principle for its

working. But they are according to their applications. Most of the devices have the

application of relays.

8.2Why is a relay used?

The main operation of a relay comes in place where only a low-power signal can be used to

control a circuit. It is also used in place where only one signal can be used to control a lot of

circuit. The application of relay started during the invention of telephones. They were also

used in long distance telegraphy. They were used to switch the signal coming from one

source to another destination. After the invention of computer they were used to perform

Boolean and other logical operations. The high end application of relay required high power

to be driven by electric motor and so on. Such relay are called contactors.

8.3 Relay Logic

There are several kinds of logic that are made with the help of relay.

These smaller logics are the base of all kind of functioning performed in industries.

As we get command over this type of logic we can handle even complex functionally

of plant or process.

The panel made by the relay is known as relay logic panel.

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9. Sinking and Sourcing

One of the most often misunderstood notions in control engineering is the concept of the

sinking and sourcing relationship between I/O devices. This document is meant to give a

solid understanding of these concepts, and clear up the definition issues of Sinking (NPN)

and Sourcing (PNP), from both a technical and terminology perspective. “Sinking” and

“Sourcing” terms are very important in connecting a PLC correctly with external

environment. These terms are applied only for DC modules.

In general, Sinking (NPN) and Sourcing (PNP) are terms that define the control of direct

current flow in a load. They are only pertinent with DC component and should not be

associated with AC control structure. Device like relay output, reed, switches, etc, are

typically not affected since they are not current direction dependent.

9.1 Output Device:

Sinking (NPN) Output: Are output that “Sink” or “Pull” current through the load.

In case the common connection to the load is the 24 VDC (+DC) line.

Sinking output module require the load to be energized by a current, which flows from +24

VDC (+DC), through the load, through the NPN output switch device to the 0 VDC (-DC)

line.

25

Sourcing (PNP) Outputs: Are outputs that “Source” or “Push” current through the load.

This mean that the common connection to the load is the 0 VDC (-DC) line.

Sourcing output module required the load to be energized by a current that flow from +24

VDC (+DC), through the PNP output switch device, through the load to the 0 VDC (-DC)

line.

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9.2 Input Device:

Sinking (NPN) Input: Are input that require an external sensor device to “Sink” or “Pull”

current from the circuitry to 0 VDC (-DC). This means that the external sensor service

provide a current path the 0 VDC (-DC) common point. Below is a representation of the

circuit connection.

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Sourcing (PNP) Inputs: Are inputs that require an external sensor device to “Source” or

“Push” current from the 24 VDC (+DC) line to the input circuitry. This means that the

external sensor device provide a current path the 24 VDC (+DC) common point to the input

circuitry.

28

Latching: Latching is the process in which once output or coil is energized forever. Latching

is done by contact of output or coil which we want to switch ON Permanently.

I0.1=ON, Q0.1=ON,

I0.1=OFF, Q0.1=ON,

10. S7-200 CPU 222 description:

29

CPU: The CPU executes the program and stores the data for controlling the automation task

or process. Different types of CPU are available in S7-200 series.

CPU AC/DC/RELAY

CPU: This CPU no. for 8 digital input & outputs

AC/DC/Relay: AC means PLC CPU required supply is AC (+230v AC) and DC means PLC

input and output are working on DC (+24v DC) and relay means PLC based on relay.

Power Supply: The power supply provides electrical power for the base unit and for

any expansion module that is connected.

Input & Output: The input and outputs are the system control points: the inputs

monitor the signals from the field device and the outputs control pumps, motor, or

other devices in your process.

Communication Port: the communication port allows you to connect the CPU to a

programming device or to other devices.

Status LED’S:Status LED’S provide visual information about the CPU mode (RUN

and STOP), the current the state of the local I/O, and whether a system fault has been

detected, for example, the mode switch is set the mode switch is set to the run

position, the green run indicator is lit. When the mode switch is set to the stop

position, the yellow stop indicator is lit.

Cartridge: A plug-in serial EEPROM, cartridges provide a mean to store CPU

programs and transfer program from one CPU to another.

Mode Selector switch

Mode selector switch consist of 3 modes Run, Stop, Term.

Run Mode: When the mode switch is Run position the CPU is Run and

executing the program.

Stop Mode: When the mode switch is Stop position the CPU is Stop.

Term Mode: When the mode switch is in Term position the programming

device can select the operating mode.

Analog adjustment Pot 0: The analog adjustment is used to increase or decrease

values stored in special memory. These values can be used to update the value of

timer or counter, or can be used to set limits.

Expansion Modules socket: S7-200 PLCs are expandable. Expansion module

contains additional inputs and outputs. These are connected to the base unit using a

ribbon connector.

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11. Programming language and Techniques

PLC languages are designed to emulate the popular relay ladder diagram format. This is read

and understood worldwide by maintenance technicians as well as by engineers. Unlike

computer programming does not require extensive special training. Applications know-how

is much more important. Although certain special techniques are important to programming

efficiency, they are easily learned. The major goal is control program performance. Another

difference between computers and PLCs is the sequential operation of the PLC.

This is an extremely useful feature that allows easy programming of shift registers, ring

counters, drum timers, and other useful indexing techniques for real-time control

applications.

11.1.1 Maintenance and Troubleshooting:

As a plant floor controller, the PLC must be maintained by the plant electrician or the

instrument technician. It would be highly impractical to require computer-type maintenance

service. To this end, PLC manufactures build in self-diagnostics to allow for easy

troubleshooting and repair of problems. Most PLC component are modular and simple to

isolator; remove and replace diagnostic techniques are usually implemented.

11.2 Concept of an S7-200 Programming

Relating the program to Input and Outputs

The basic operation of the S7-200 CPU is very simple

The program that is stored in the CPU uses these inputs to evaluate the control logic.

As the program runs, the CPU updates the data.

The CPU writes the data to the outputs

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11.2.1 Concepts of the S7-200 Programming Language and Editors:

The S7-200 CPUs offer many types of instruction that allows you to solve a wide variety of

automation tasks. Therefore are two basic instruction sets available in the S7-200 CPU:

SIMATIC and IEC 1131-3. Also, our PC-based programming software, Step 7-MICRO/WIN

32, provides different editor choices that allow you to create control program with these

instruction. For example, you may prefer to create program in am or graphical environment,

while someone else in your company may prefer a text-based assembly- language style of

editor.

11.3 Statement List editor:

The STEP 7-MICRO/WIN 32 statement lists (STL) editor allows you to create control

program by entering the instruction mnemonics. In general, the STL editor also allows you to

create programs that you could not otherwise create with the ladder logic or function block

diagram editors. This is because you are programming in the native language of the CPU,

rather than in a graphical editor where some restriction must be applied in order to draw the

diagrams correctly.

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11.4 Ladder Programming:

Ladder logic is form of drawing electric logic schematics, and is a graphical language very

popular for programming of PLC. Ladder was original invented to describe logic made from

relay. The name is based on the observation that program in this language resemble ladders,

with two vertical “rails” and a series of horizontal “rungs” between them.

11.4.1 Ladder Logic Editor:

The STEP 7-MICRO/WIN 32 Ladder Logic (LAD) editor allows you to build program that

resemble the equivalent of an electrical wiring diagram. Ladder programming is probably

method of choice for many PLC programmers and maintenance personnel. Basically, the

ladder programs allow the CPU to emulate the flow of electric current from a power source,

through a series of logical input condition that in turn enable logical output condition. The

logic is usually separated into small, easy-to-understand piece that are often called “rungs” or

“networks”. The program is executed one network at a time, from left to right and then top or

bottom as dictated by the program. Once the CPU has reached the end of the program, it

starts over again at the top of the program.

11.5 Function Block Diagram:

The STEP 7-MICRO/WIN 32 function block diagram (FBD) editor allow you to view the

instructions as logic boxes that resemble common logic gate diagram. There are no contact

and coils as found in the LAD editor, but there are equivalent instructions that appear as box

instructions. The program logic is derived from the connections between these box

instructions. That is, the output from one instruction (such as an AND box) can be used to

enable another instructions. That is, the output from one instruction can be used to enable

another instruction to create the necessary control logic. This connection concept allows you

to solve a wide variety of logic problems.

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12. Some program have make during “Industrial Training”

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13. Reference

1. Internet Advertisement.

2. College Seminar.