Seminar on Programmable Logic Controller (PLC)

8/14/2019 Seminar on Programmable Logic Controller (PLC)

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ProgrammableLogicControllerProgrammableLogicControllerProgrammableLogicControllerProgrammableLogicControllerProgrammableLogicControllerProgrammableLogicControllerProgrammableLogicControllerProgrammableLogicController

(PLC)(PLC)(PLC)(PLC)(PLC)(PLC)(PLC)(PLC)Presented By :

SeminaronSeminaronSeminaronSeminaronSeminaronSeminaronSeminaronSeminaron

Mahesh J. Vadhavaniya (122511)M. E. Regular, 212 1!

"#$$$R, %handigarh&u'et *aulty :

Pr+. Ra- Murat &ingh


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Objectives :

At the end of the Session we will be able to:

Describe the major components of a common PLC.

Interpret PLC specifications.

Apply trobleshootin! techni"es.

Convert conventional relay lo!ic to a PLC lan!a!e. Operate and pro!ram a PLC for a !iven application.


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Contents :

#istory of Pro!rammable Controllers

$elay Ladder Lo!ic

Central Processin! %nit

Inpt&Otpt System

Pro!rammin! and Peripheral Devices

Pro!rammin! ConceptsApplications

'robleshootin! and (aintenance


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ProcessProcessProcessProcessProcessProcessProcessProcessControlControlControlControlControlControlControlControl&Automation&Automation&Automation&Automation&Automation&Automation&Automation&AutomationProcesscontrolProcesscontrolProcesscontrolProcesscontrol

Recognizing Process the Actuate the

Rules &

guidelines


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WhyAutomation?WhyAutomation?WhyAutomation?WhyAutomation?WhyAutomation?WhyAutomation?WhyAutomation?WhyAutomation?#i!her prodctivity

Sperior "ality of end prodct

)fficient sa!e of ener!y and raw materials

Improved safety in wor*in! condition

etc+


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HistoryofHistoryofHistoryofHistoryofHistoryofHistoryofHistoryofHistoryofProcessControlProcessControlProcessControlProcessControlProcessControlProcessControlProcessControlProcessControl&&&&&&&&AutomationAutomationAutomationAutomationAutomationAutomationAutomationAutomation

Electronics Control

PLC Control

Manual Control

Hard-Wire Control


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1.PLC1.PLC1.PLC1.PLC1.PLC1.PLC1.PLC1.PLC !ntro"uction!ntro"uction!ntro"uction!ntro"uction!ntro"uction!ntro"uction!ntro"uction!ntro"uction

WhatWhatWhatWhat "oes"oes"oes"oes PLCPLCPLCPLC stan"stan"stan"stan" for?for?for?for?

PLC , Pro!rammable Lo!ic Controller

PLC implements lo!ic control fnctions by means of a

pro!ram


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Programmable Logic Controllers( Definition according to NEMA standard ICS3-1978)

A di!itally operatin! electronicapparats which ses a pro!rammin!

instrctions for implementin! specificfnctions sch as lo!ic- se"encin!-timin!- contin! and arithmetic to controlthro!h di!ital or analo! modles-varios types of machines or process.


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Ho#Ho#Ho#Ho# "oes"oes"oes"oes aaaa PLCPLCPLCPLC "iffer"iffer"iffer"iffer fromfromfromfrom aaaa com$uter?com$uter?com$uter?com$uter?

A compter is optimied for calclation and display tas*s

A compter is pro!rammed by specialists

A PLC is desi!ned for /lo!ic0 control and re!lation tas*s

A PLC is pro!rammed by non,specialists

A PLC is well adapted to indstrial environment


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PLC OriginPLC Origin

Developed to replace relays in the late 1234s

Costs roppe an ecame pop ar y 1254s

6ow sed in many indstrial desi!ns


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Historical BackgroundHistorical Background

'he #ydramatic Division of the 7eneral (otors

Corporation specified the desi!n criteria for the first

pro!rammable controller in 1235

'heir primary !oal :

'o eliminate the hi!h costs associated with infle8ible-relay,controlled systems.


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Programmable Controller DevelopmentProgrammable Controller Development

1235 Pro!rammable concept developed

1232 #ardware CP% controller- with lo!ic

instrctions- 1 9 of memory and 15 I&O

points

12;<

%se o severa m t processors w t n aPLC , timers and conters= arithmetic

operations= 1 9 of memory and 14< I&O

points

12;3 $emote inpt&otpt systems introdced

12;;

(icroprocessors , based PLC introdced


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1254 Intelli!ent I&O modles developed

)nhanced commnications facilities

)nhanced software featres

Programmable Controller DevelopmentProgrammable Controller Development

/e.!. docmentation0 %se of personalmicrocompters as pro!rammin! aids

125> Low , cost small PLC?s introdced

125@ 6etwor*in! of all levels of PLC- compter

and machine sin! SCADA software.onwards


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INTRODUCTION TO PLCSINTRODUCTION TO PLCS

Advanta!es of PLCs :

Less wirin!.

irin! between devices and relay contacts are done

in the PLC pro!ram.

)asier and faster to ma*e chan!es.

'roble shootin! aids ma*e pro!rammin! easier

and redce downtime.

$eliable components ma*e these li*ely to operate for

years before failre.


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INTRODUCTION TO PLCSINTRODUCTION TO PLCS

Advanta!es of PLCs :

'hey are cost,effective

'hey are fle8ible- reliable and compact

'he have si ni icant advanta es over traditional

control systems based on relay or pnematics


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hat tas*s do PLC perform B

'he lo!ic control tas*s sch as interloc*in!-

se encin timin and contin reviosl

nderta*en with relays or pnematics0

In addition- PLCs can perform a variety ofcalclation- commnication and monitorin! tas*s


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Leading Brands Of PLCLeading Brands Of PLC

A()$ICA6: 1. Allen radley

. 7old (odicon

>. 'e8as Instrments


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FAPA6)S): 1. 'oshiba

. Omron

Leading Brands Of PLCLeading Brands Of PLC

>. anc


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Areas of Application :Areas of Application :

(anfactrin! & (achinin!

Eood & evera!e

Power

(inin!

Petrochemical & Chemical


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PLC Size :PLC Size :

Small: It covers nits with p to 15 I&O?s and memories

p to 9bytes.

'hese PLC?s are capable of providin! simple to

advance levels or machine controls.

(edim: #ave p to 4

9bytes.

Lar!e: 'he most sophisticated nits of the PLC family.

'hey have p to 512 I&O?s and memories p to ;@49bytes.

Can control individal prodction processes or

entire plant.


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Major Components of a Common PLCMajor Components of a Common PLC

POWER

SUPPLY

I MN OP D

O MU OT D

PROCESSOR

U UT L

E

P UU LT E

PROGRAMMINGDEVICE

FromSENSORS

Pushbuttons,contacts,

limit switches,etc.

ToOUTPUT

Solenoids,contactors,

alarms.Motors

etc.


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Power Spply:

Provides the volta!e needed to rn the primary PLC

components

I&O (odles:

Provides si!nal conversion and isolation between the

internal lo!ic, level si!nals inside the PLC and the field?s

hi!h level si!nal.


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Processor :

Provides intelli!ence to command and !overn the activities

o the entire PLC s stems.


Pro!rammin! Device :

%sed to enter the desired pro!ram that will determine the

se"ence of operation and control of process e"ipment or

driven machine.


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I/O ModuleI/O Module

'he I&O interface section of a PLC connects it to e8ternal field

devices.

'he main prpose of the I&O interface is to condition the

varios si!nals received from or sent to the e8ternal inpt

and otpt devices.

Inpt modles converts si!nals from discrete or analo! inpt

devices to lo!ic levels acceptable to PLC?s processor.

Otpt modles converts si!nal from the processor to levels

capable of drivin! the connected discrete or analo! otpt

devices.


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IS NEEDED TO:

Prevent voltage

transients fromdamaging theprocessor.

Helps reduce theeffects of electrical

USE TO

DROP THEVOLTAGETO LOGICLEVEL


DC Inpt (odle

OPTOISOLAT

OR

noise

Current

LimitingResistor

FROMINPUTDEVICE

Buffer,

Filter,hysteresis Circuits

TOPROCESSOR


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IS NEEDED TO:

Prevent voltagetransients fromdamaging theprocessor.

Helps reduce the

CONVERTS THE

AC INPUT TO DCAND DROPS THEVOLTAGE TO


AC Inpt (odle

OPTOISOLAT

OR

effects of electrical

noise

Rectifier,

ResistorNetwork

FROMINPUT

DEVICE

Buffer,

Filter,HysteresisCircuits

TOPROCESSOR


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%


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IS NEEDED TO:

Prevent voltagetransients fromdamaging the

processor.

Helps reduce theeffects of electricalnoise


DC&AC Otpt (odle

OPTOISOLA

TOR

FROMPROCESSOR

TTLCircuits

AmplifierRELAYTRIAC

XSISTOR

TOOUTPUT

DEVICE


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I/OI/O CircuitsCircuits

DIEE)$)6' 'GP)S OE I&O CI$C%I'S

1. Pilot Dty Otpts :

Otpts of this type typically are sed to drive hi!h,crrent

electroma!netic loads sch as solenoids- relays- valves- and

motor starters.

'hese loads are hi!hly indctive and e8hibit a lar!e inrsh

crrent.

Pilot dty otpts shold be capable of withstandin! an

inrsh crrent of 14 times the rated load for a short period of

time withot failre.


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. 7eneral Prpose Otpts :

'hese are sally low, volta!e and low,crrent and are sed

to drive indicatin! li!hts and other non,indctive loads. 6oise

sppression may or may not be inclded on this types of

modles.

>. Discrete Inpts :

Circits of this type are sed to sense the stats of limitswitches- psh bttons- and other discrete sensors. 6oise

sppression is of !reat importance in preventin! false

indication of inpts trnin! on or off becase of noise.


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@. Special Prpose I&O :

Circits of this type are sed to interface PLCs to very specific

types of circits sch as servomotors- steppin! motors PID

/proportional pls inte!ral pls derivative0 loops- hi!h,speed

plse contin!- resolver and decoder inpts- mltiple8ed

displays- and *eyboards.

'his modle allows for limited access to timer and conter

presets and other PLC variables withot re"irin! a pro!ram

loader.


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INPUTS

OUTPUTS

MOTOR

PLC

LAMP

PUSH BUTTONS


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INPUT DEVICES:

LimitS#itch

Pushutton

LeelSW

*lo#SW


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Motor

Solenoid

OUTPUT DEVICES:

Heater Coil

Lamp


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L1 L%

P.SW!'CH

!+%

,

!-!n$ut

o"uleslot/inrac0

o"ule

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!4P5'675L8

W!9!4:7!A:9A

LA7789P96:9A

ermna

A""ressA""ressA""ressA""ress!+%.,;,!+%.,;,!+%.,;,!+%.,;,


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4.

6

C

L%

L1

L1L%

6'69

C64'AC'69

*!8L7W!9!4:

S6L846!7


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Discrete Input

A discrete input also referred as digital input is an input that is eitherON or OFF are connected to the PLC digital input. In the ON conditionit is referred to as logic 1 or a logic high and in the OFF conditionmaybe referred to as logic o or logic low.

4ormally6$enPushbutton

4ormally6$ens#itch

4ormallyClose"s#itch

4ormally6$encontact

4ormallyclose"contact


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OFFLogic 0

IN

PLC

Input

Module

24 V dc

OFFLogic 1

IN

PLC

InputModule

24 V dc


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An analog input is an input signal that has a continuoussignal. Typical inputs may vary from 0 to 20mA, 4 to 20mAor 0 to10V. Below, a level transmitter monitors the level ofliquid in the tank. Depending on the level Tx, the signal to thePLC can either increase or decrease as the level increasesor decreases.

Analog Input

IN

PLC

AnalogInputModule

Tank

Level Transmitter


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A discrete output is either in an ON or OFF condition. Solenoids,contactors coils, lamps are example of devices connected to theDiscrete or digital outputs. Below, the lamp can be turned ON or OFF bythe PLC output it is connected to.

Digital Output

PLC

DigitalOutputModule

Lamp


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An analog output is an output signal that has a continuoussignal. Typical outputs may vary from 0 to 20mA, 4 to 20mAor 0 to10V.

Analog Output

Electric to pneumatic transducer

PLC

AnalogOutputModule

E

P

Pneumatic control valve

Supply air0 to 10V


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ProcessorThe processor module contains the PLCs microprocessor, its supportingcircuitry, and its memory system.

The main function of the microprocessor is to analyze data coming fromfield sensors through input modules, make decisions based on the usersdefined control program and return signal back through output modules tothe field devices. Field sensors: switches, flow, level, pressure, temp.

, . , , , ,

audible devices.

The memory system in the processor module has two parts: a system

memoryand an application memory.


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Memory Map Organization

SYSTEM

System memory includes an area called the EXECUTIVE,composed of permanently-stored programs that direct allsystem activities, such as execution of the users controlprogram, communication with peripheral devices, and othersystem activities.The system memory also contains the routines that

implement the PLCs instruction set, which is composed ofspecific control functions such as logic, sequencing, timing,counting, and arithmetic.System memory is generally built from read-only memorydevices.

APPLICATION

The application memory is divided into the data table areaand user program area.The data table stores any data associated with the userscontrol program, such as system input and output status data,and any stored constants, variables, or preset values. Thedata table is where data is monitored, manipulated, andchanged for control purposes.The user program area is where the programmedinstructions entered by the user are stored as an applicationcontrol program.

Data TableUser Program


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Memory DesignsVOLATILE.A volatile memory is one that loses its stored information when power isremoved.

Even momentary losses of power will erase any information stored orprogrammed on a volatile memory chip.

Common Type of Volatile Memory

RAM. Random Access Memory(Read/Write)Read/write indicates that the information stored in the memory can beretrieved or read, while write indicates that the user can program or writeinformation into the memory.


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Memory DesignsThe words random access refer to the ability of any location (address) inthe memory to be accessed or used. Ram memory is used for both theuser memory (ladder diagrams) and storage memory in many PLCs.

RAM memory must have battery backup to retain or protect the storedprogram.


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Memory Designs

Several Types of RAM Memory:

1.MOS2.HMOS

3.CMOS

The CMOS-RAM (Complimentary Metal Oxide Semiconductor) is probablyone of the most popular. CMOS-RAM is popular because it has a very lowcurrent drain when not being accessed (15microamps.), and the information

stored in memory can be retained by as little as 2Vdc.


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Memory Designs

NON-VOLATILEHas the ability to retain stored information when power is removed,accidentally or intentionally. These memories do not require battery back-up.

Common Type of Non-Volatile Memory

ROM, Read Only MemoryRead only indicates that the information stored in memory can be read only

and cannot be changed. Information in ROM is placed there by the

manufacturer for the internal use and operation of the PLC.


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Memory DesignsOther Types of Non-Volatile Memory

PROM, Programmable Read Only MemoryAllows initial and/or additional information to be written into the chip.

PROM may be written into only once after being received from the PLCmanufacturer; programming is accomplish by pulses of current.

e curren me s e us e n s n e ev ce, preven ng rom e ng

reprogrammed. This type of memory is used to prevent unauthorizedprogram changes.


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Memory DesignsEEPROM, Electrically Erasable Programmable Read OnlyMemory

Also referred to as E2PROM, is a chip that can be programmed using astandard programming device and can be erased by the proper signal beingapplied to the erase pin.

EEPROM is used primarily as a non-volatile backup for the normal RAM

memory. If the program in RAM is lost or erased, a copy of the programstored on an EEPROM chip can be down loaded into the RAM.

Programmable Logic ControllerProgrammable Logic ControllerProgrammable Logic ControllerProgrammable Logic ControllerProgrammable Logic ControllerProgrammable Logic ControllerProgrammable Logic ControllerProgrammable Logic Controller


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ProgrammableLogicControllerProgrammableLogicControllerProgrammableLogicControllerProgrammableLogicControllerProgrammableLogicControllerProgrammableLogicControllerProgrammableLogicControllerProgrammableLogicController

Power

supply

Input

module

CPU

Program memory

Output

module

Field ControlInput

Elements

Process / Machine

PLC 6$erating Princi$lePLC 6$erating Princi$lePLC 6$erating Princi$lePLC 6$erating Princi$lePLC 6$erating Princi$lePLC 6$erating Princi$lePLC 6$erating Princi$lePLC 6$erating Princi$le


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PLC6$eratingPrinci$lePLC6$eratingPrinci$lePLC6$eratingPrinci$lePLC6$eratingPrinci$lePLC6$eratingPrinci$lePLC6$eratingPrinci$lePLC6$eratingPrinci$lePLC6$eratingPrinci$le

!n!n!n!n$utscan$utscan$utscan$utscan

StartStartStartStart

6ut6ut6ut6ut$utscan$utscan$utscan$utscan

CommunicationCommunicationCommunicationCommunication


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PLC OperationBasic Function of a Typical PLC

Read all field input devices via the input interfaces, execute the userprogram stored in application memory, then, based on whatever control

scheme has been programmed by the user, turn the field output devices onor off, or perform whatever control is necessary for the process application.

,memory, and updating the outputs is known as scanning.

C


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While the PLC is running, the scanning process includes the following four

phases, which are repeated continuously as individual cycles of operation:

PHASE 2

PHASE 1

Read InputsScan

rogram

ExecutionPHASE 3

Diagnostics/Comm

PHASE 4OutputScan


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PHASE 1 Input Status scan

A PLC scan cycle begins with the CPU reading the status of its inputs.

PHASE 2 Logic Solve/Program Execution

e app cat on program s execute us ng t e status o t e nputs

PHASE 3 Logic Solve/Program Execution

Once the program is executed, the CPU performs diagnostics andcommunication tasks


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PHASE 4 - Output Status ScanAn output status scan is then performed, whereby the stored outputvalues are sent to actuators and other field output devices. The cycleends by updating the outputs.


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PLC CommunicationsCommon Uses of PLC Communications Ports

Changing resident PLC programs - uploading/downloading from asupervisory controller (Laptop or desktop computer).

Forcing I/O points and memory elements from a remote terminal.

and computer.

Monitoring data and alarms, etc. via printers or Operator Interface Units(OIUs).


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PLC CommunicationsSerial Communications

PLC communications facilities normally provides serial transmission ofinformation.

Common Standards

Used in short-distance computer communications, with the majority ofcomputer hardware and peripherals. Has a maximum effective distance of approx. 30 m at 9600 baud.

PLC Communications


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PLC CommunicationsLocal Area Network (LAN)

Local Area Network provides a physical link between all devices plus

providing overall data exchange management or protocol, ensuring that each

device can talk to other machines and understand data received from them.

LANs provide the common, high-speed data communications bus whichinterconnects any or all devices within the local area.

LANs are commonly used in business applications to allow several users toshare costly software packages and peripheral equipment such as printersand hard disk storage.


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PLC CommunicationsRS 422 / RS 485

Used for longer-distance links, often between several PCs in adistributed system. RS 485 can have a maximum distance of about 1000

meters.


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PLC CommunicationsProgrammable Controllers and Networks

Dedicated Network System of Different Manufacturers

Manufacturer Network

-

Gould Modicon Modbus

General Electric GE Net Factory LAN

Mitsubishi Melsec-NET

Square D SY/NET

Texas Instruments TIWAY


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SpecificationsSeveral factors are used for evaluating the quality and performance ofprogrammable controllers when selecting a unit for a particular application.These are listed below.

NUMBER OF I /O PORTS

This specifies the number of I/O devices that can be connected to the.

with enough spares to provide for moderate future expansion.


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PLCProgrammingPLCProgrammingPLCProgrammingPLCProgrammingPLCProgrammingPLCProgrammingPLCProgrammingPLCProgramming


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PLC is software driven e"ipment li*e compter

or*in! of PLC /process0 is decided by ser thro!h pro!ram.

Dependin! on process re"irement pro!ram /set of instrction0 is

prepared.

CP% se"entially read these instrction and operates control

elements based on inpt si!nals and pro!ram instrction.

Pro!rammin! can be done On,line or Off,line.

6ormally pro!rammin! & chan!e in pro!ram is done in memory of

pro!rammin! nit and then simply this chan!e is loaded in CP%

memory of PLC

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,

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PROGRAMMING

Normally Open

(NO)

Normally Closed

(NC)

Power flows through these contacts when they are closed. The

normally open (NO) is true when the input or output status bitcontrolling the contact is 1. The normally closed (NC) is true

when the input or output status bit controlling the contact is 0.


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Coils

Coils represent relays that are energized when power flows tothem. When a coil is energized it causes a corresponding

out ut to turn on b chan in the state of the status bit controllinthe output to 1. That same output status bit maybe used to control

normally open or normally closed contact anywhere in the program.


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Boxes

Boxes represent various instructions or functions that areExecuted when power flows to the box. Some of theseFunctions are timers, counters and math operations.

AND OPERATION


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Each rung or network on a ladder program represents

Rung

A C

must be true (1) in order for the output C to be true (1).

OR OPERATION


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Rung

A

C

In the rung above, it can be seen that either input A or B

is be true (1), or both are true, then the output C is true (1).

NOT OPERATION


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Rung

A C

In the rung above, it can be seen that if input A is be true (1),

then the output C is true (0) or when A is (0), output C is 1.

WritingProgramWritingProgramWritingProgramWritingProgramWritingProgramWritingProgramWritingProgramWritingProgram


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Ladder logic (1)'hela""erlogicistheol"est$rogramminglanguageforPLC

itbases"irectlyontherelayintuitionoftheelectricians.itis#i"elyinuseoutsi"e8uro$e.

(Kontaktplansprache, langage contacts)

.

Ladder Logic (2)


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,1,%

,> ,

relaycoil(bobine)

brea0contact

ma0econtact(contacttraail)origin+

electrical

circuit

,1 ,%

,,>

(contactre$os)

corres$on"ingla""er"iagram

, ,

22

rungrungrungrung

DcoilD,isuse"tomoeothercontact(s)


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Ladder logic (4)Binar combinations are e pressed b series and parallel rela contact


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Binary combinations are expressed by series and parallel relay contact:

+ 01 02

50

Coil 50 is active (current flows) when 01 is active and 02 is not.

01

02 50

Series

ladder logic representation logic" equivalent

+ 01

40

02

Coil 40 is active (current flows) when 01 is active or 02 is not.

Parallel01

0240

Ladder logic (5)The ladder logic is more intuitive for complex binary expressions than literal language


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50

1 2 3 4

5 6

!N 1 & 2 STR 3 & N 4 STR N 5& 6 / STR & STR = 50

textual expression

50

0 1 4 5

6 72 3

10 11

12

!0 & 1 STR 2 & 3 / STR STR 4& 5 STR N 6 & 7

/ STR & STR STR 10& 11 / STR & 12 = 50

Ladder logic (6)Ladder logic stems from the time of the relay technology.


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As PLCs replaced relays, their new possibilities could not be expressed anymore in relay terms.

The contact plan language was extended to express functions:

literal expression:

=200FUN 02

0100

The intuition of contacts and coil gets lost.

The introduction of functions that influence the control flow itself, is problematic.

The contact plan is - mathematically - a functional representation.

The introduction of a more or less hidden control of the flow destroys thefreedom of side effects and makes programs difficult to read.

Ladder logic (7)


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Ladder logic provides neither: sub-programs (blocks), nor

data encapsulation nor

structured data types.

It is not suited to make reusable modules.

IEC 61131 does not prescribe the minimum requirements for a compiler /

interpreter such as number of rungs per page nor does it specifies the minimumsubset to be implemented.

Therefore, it should not be used for large programs made by different persons

It is very limited when considering analog values (it has only counters)

used in manufacturing, not process control


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CriteriaforselectingaPLCCriteriaforselectingaPLCCriteriaforselectingaPLCCriteriaforselectingaPLCCriteriaforselectingaPLCCriteriaforselectingaPLCCriteriaforselectingaPLCCriteriaforselectingaPLC@ Ho#Ho#Ho#Ho# manymanymanymany controlcontrolcontrolcontrol in$utsin$utsin$utsin$uts totototo bebebebe $rocesse"$rocesse"$rocesse"$rocesse" 4os4os4os4os ofofofof !n$ut!n$ut!n$ut!n$ut


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@ Ho#Ho#Ho#Ho# manymanymanymany controlcontrolcontrolcontrol in$utsin$utsin$utsin$uts totototo bebebebe $rocesse"$rocesse"$rocesse"$rocesse" 4os4os4os4os.... ofofofof !n$ut!n$ut!n$ut!n$ut@ Ho#Ho#Ho#Ho# manymanymanymany out$utout$utout$utout$ut "eices"eices"eices"eices orororor controllingcontrollingcontrollingcontrolling elementselementselementselements areareareare

controlle"controlle"controlle"controlle" 4os4os4os4os.... ofofofof 6ut$ut6ut$ut6ut$ut6ut$ut....

@ WhatWhatWhatWhat memorymemorymemorymemory ca$acityca$acityca$acityca$acity isisisis nee"e"nee"e"nee"e"nee"e" totototo storestorestorestore thethethethe FuserFuserFuserFuser$rogramG$rogramG$rogramG$rogramG ????

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@ WhatWhatWhatWhat areareareare thethethethe communicationcommunicationcommunicationcommunication reuirementsreuirementsreuirementsreuirements ????@ AreAreAreAre theretheretherethere anyanyanyany s$ecials$ecials$ecials$ecial orororor s$ecifics$ecifics$ecifics$ecific reuirementsreuirementsreuirementsreuirements inclu"inginclu"inginclu"inginclu"ing

thatthatthatthat ofofofof safetyIsafetyIsafetyIsafetyI reliabilityIreliabilityIreliabilityIreliabilityI eE$an"abilityeE$an"abilityeE$an"abilityeE$an"ability etcetcetcetc....

@ SystemSystemSystemSystem oltageoltageoltageoltage aailableaailableaailableaailable forforforfor auEiliaryauEiliaryauEiliaryauEiliary su$$lysu$$lysu$$lysu$$ly ofofofof PLCPLCPLCPLC....

6n6n6n6n gettinggettinggettinggetting thisthisthisthis informationinformationinformationinformation chec0chec0chec0chec0 forforforfor thethethethe s$ecifications$ecifications$ecifications$ecification ofofofofthethethethe aailableaailableaailableaailable PLCsPLCsPLCsPLCs....

Selecting a PLC


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Criteria

Number of logical inputs and outputs.

Memory Number of special I/O modules Scan Time Communications Software

A Detailed Design Process


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1. Understand the process

2. Hardware/software selection

3. Develop ladder logic

4. Determine scan times and memory requirements

Specifications


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Several factors are used for evaluating the quality and performance ofprogrammable controllers when selecting a unit for a particular application.These are listed below.

NUMBER OF I /O PORTS

This specifies the number of I/O devices that can be connected to the.

with enough spares to provide for moderate future expansion.

Specifications

OUTPUT PORT POWER RATINGS


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OUTPUT-PORT POWER RATINGS

Each output port should be capable of supplying sufficient voltage andcurrent to drive the output peripheral connected to it.

SCAN TIME

-program. This variable is usually specified as the scan time per 1000 logic

nodes and typically ranges from 1 to 200 milliseconds.

Specifications


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MEMORY CAPACITY

The amount of memory required for a particular application is related to the

length of the program and the complexity of the control system. Simple

applications having just a few relays do not require significant amount ofmemory. Program length tend to expand after the system have been usedfor a while. It is advantageous to a acquire a controller that has morememory an s presen y nee e .

PLC Status Indicators

Power On


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Power On

Run Mode

Programming Mode

Fault

Troubleshooting

1 Look at the process


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1. Look at the process2. PLC status lights

HALT - something has stopped the CPURUN - the PLC thinks it is OK (and probably is)

ERROR - a physical problem has occurred with the PLC3. Indicator lights on I/O cards and sensors4. Consult the manuals, or use software if available.

. .

List of items required when working with PLCs:

1 Programming Terminal - laptop or desktop PC


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1. Programming Terminal - laptop or desktop PC.2. PLC Software. PLC manufacturers have

their own specific software and license key.3. Communication cable for connection from Laptop

to PLC.4. Backup copy of the ladder program (on diskette, CDROM,

hard disk, flash memory). If none, upload it from the PLC.

-. , , ,ladder program printout, and Seq. of Operations manual.)

Examples of PLC Programming Software:

1 Allen-Bradley Rockwell Software RSLogix500


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1. Allen Bradley Rockwell Software RSLogix5002. Modicon - Modsoft3. Omron - Syswin4. GE-Fanuc Series 6 LogicMaster6

5. Square D- PowerLogic6. Texas Instruments Simatic6. Telemecanique Modicon TSX Micro


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Documents

Seminar on Programmable Logic Controller (PLC)