Assignment Dr Tee.doc

8/11/2019 Assignment Dr Tee.doc

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1.0 INTRODUCTION

Programmable logic controllers (shown in Figure 1) are now the most

widely used industrial process control technology. A programmable logic

controller (PLC) is an industrial grade computer that is capable of beingprogrammed to perform control functions.

The programmable logic controller is designed for multiple input and

output arrangements e!tended temperature ranges immunity to electrical

noise and resistance to "ibration and impact.

A PLC is an e!ample of a real#time system since the output of the

system controlled by the PLC depends on the input conditions. The

programmable logic controller is then basically a digital computer designedfor use in machine control. $nli%e a personal computer it has been

designed to operate in the industrial en"ironment and is e&uipped with

special input'output interfaces and a control programming language.

n a traditional industrial control system all control de"ices are wired

directly to each other according to how the system is supposed to operate.

n a PLC system howe"er the PLC replaces the wiring between the de"ices.

Thus instead of being wired directly to each other all e&uipment is wired to

the PLC. Then the control program inside the PLC pro"ides the wiring*

connection between the de"ices. The control program is the computer

program stored in the PLC+s memory that tells the PLC what+s supposed to

be going on in the system. The use of a PLC to pro"ide the wiring

connections between system de"ices is called softwiring.

The softwiring ad"antage pro"ided by programmable controllers is

tremendous. n fact it is one of the most important features of PLCs.

,oftwiring ma%es changes in the control system easy and cheap. f you want

a de"ice in a PLC system to beha"e di-erently or to control a di-erent

process element all you ha"e to do is change the control program. n a

traditional system ma%ing this type of change would in"ol"e physically

changing the wiring between the de"ices a costly and time#consuming

endea"or.

PLCs o-er other ad"antages o"er traditional control systems. These

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ad"antages include Increased Reliability . /nce a program has been written and

tested it can be easily downloaded to other PLCs. The program

ta%es the place of much of the e!ternal wiring that would

normally be re&uired for control of a process. 0ardwiringre&uired to connect eld de"ices is less intensi"e. PLCs also

o-er the reliability associated with solid#state components. More Flexibility . t is easier to create and change a program in

a PLC than to wire and rewire a circuit. 2ith a PLC the

relationships between the inputs and outputs are determined by

the user program.

Lower Cost . PLCs were originally designed to replace relaycontrol logic and the cost sa"ings ha"e been so signi cant that

relay control is becoming obsolete e!cept for power

applications. 3enerally if an application has more than about a

half#do4en control relays it will probably be less e!pensi"e to

install a PLC. Comm nications Ca!ability . A PLC can communicate with

other controllers or computer e&uipment to perform suchfunctions as super"isory control data gathering monitoring

de"ices and process parameters and download and upload of

programs. Faster Res!onse Time . PLCs are designed for high#speed and

real#time applications. The programmable controller operates in

real time which means that an e"ent ta%ing place in the eld

will result in the e!ecution of an operation or output. 5achinesthat process thousands of items per second and ob6ects that

spend only a fraction of a second in front of a sensor re&uire the

PLC+s &uic%#response capability. "asier to Tro bles#oot . PLCs ha"e diagnostics and o"erride

functions that allow users to easily trace and correct software

and hardware problems. To nd and ! problems users can

display the control program on a monitor and watch it in real7


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time as it e!ecutes.

A typical PLC can be di"ided into parts as illustrated in Figure 1 below

which are

Central Processing $nit (CP$) nput'output ( '/)

Power ,upply

Programming 8e"ice

Figure 1 Typical parts of PLC.

Central Processing Unit (CPU)

The processor (CP$) is the brain* of the PLC. A typical processorusually consists of a

microprocessor for implementing the logic and controlling the

communications among the

modules. The processor re&uires memory for storing the results of the

logical operations

performed by the microprocessor. 5emory is also re&uired for the program

9P:/5 or 99P:/5 plus :A5. The CP$ controls all PLC acti"ity and is;


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designed so that the user can enter the desired program in relay ladder

logic.

The PLC program is e!ecuted as part of a repetiti"e process referred

to as a scan (Figure 7). A typical PLC scan starts with the CP$ reading the

internal state of the CP$. Then the CP$ reads the reading the status ofinputs. 2hate"er program logic has been stored is e!ecuted based on the

status of the inputs. /nce the program e!ecution is completed the status of

all outputs is updated. This process is repeated continuously as long as the

PLC is in the run mode.

Figure 7 PLC scan cycle.

Input/Output (I/O)

The '/ system forms the interface by which eld de"ices are

connected to the controller. The purpose of this interface is to condition the


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"arious signals recei"ed from or sent to e!ternal eld de"ices. nput de"ices

such as pushbuttons limit switches and sensors are hardwired to the input

terminals. /utput de"ices such as small motors motor starters solenoid

"al"es and indicator lights are hardwired to the output terminals. To

electrically isolate the internal components from the input and outputterminals PLCs commonly employ an optical isolator which uses light to

couple the circuits together.

Power Supply

The power supply supplies 8C power to the internal circuitry of CP$

and other modules that plug into the rac%. For large PLC systems this power

supply does not normally supply power to the eld de"ices. 2ith largersystems power to eld de"ices is pro"ided by e!ternal alternating current

(AC) or direct current (8C) supplies.

Programming Device

A programming de"ice is used to enter the desired pro#gram into the

memory of the processor. The program can be entered using relay ladder

logic which is one of the most popular programming languages. nstead of

words ladder logic programming language uses graphic symbols that show

their intended outcome.

A personal computer (PC) is the most commonly used programming

de"ice. 5ost brands of PLCs ha"e software a"ailable so that a PC can be

used as the programming de"ice. This software allows users to create edit

document store and troubleshoot ladder logic programs. The PC

communicates with the PLC processor "ia a serial or parallel data

communications lin%.

PLC vs PC

A PLC can be regarded as a process control computer system whereas

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PC is a data#processing computer system (Figure ;). The architecture of a

PLC is basically the same as that of a personal computer. 0owe"er some

important characteristics distinguish PLCs from personal computers.

First unli%e PCs the PLC is designed to operate in the industrial

en"ironment with wide ranges of ambient temperature and humidity. A well#designed industrial PLC installation is not usually a-ected by the electrical

noise inherent in most industrial locations.

$nli%e the personal computer the PLC is programmed in relay ladder

logic or other easily learned languages. The PLC comes with its program

language built into its memory and has no permanently attached input and

output console.

Computers are comple! computing machines capable of e!ecutingse"eral programs or tas%s simultaneously. 5ost PLCs on the other hand

e!ecute a single program in an orderly and se&uential fashion.

PLC control systems ha"e been designed to be easily installed and

maintained. Troubleshooting is simpli ed by the use of fault indicators and

messaging displayed on the programmer screen. nput'output modules for

connecting the eld de"ices are easily connected and replaced.

>


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Figure ; PLC "s PC

$.0 %U"&TION 1

?our company has recently recei"ed a pro6ect on building a new traffic

light system for a cross#6unction. ?ou are an electrical engineer and a PLC

programmer. ?ou are responsible for the electrical tas%s. The design must

include

i. ,ystem layout and input#output assignments

ii. Circuitry schematic circuit protectors fuse power supply lamps

(colours) induction sensors to detect a car PLC and / control relay

and safety protection circuit

iii. A mar%et part list and costing (with proof of prices such as &uotations)

i". 8raw a timing diagram for the traf c lights

". Program se&uential design or at least

se&uences "i. The ladder diagram (use C@#


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program if possible)

The time for each colour lights are briefly

assigned as below :ed depending on the other

colours and 6unctions

3reen 1=seconds

?ellow 7

seconds

:ed #B 3reen wait for 1

second


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$.1 'N&("R 1

i. ,ystem layout and input#output assignments.

Figure 1.1 Four 6unction traDc light system layout.

A four 6unction traDc light as shown in Figure 1.1 consist of < traDc

light tower which is connected directly to a controller cabinet. 9ach traDc

light tower will ha"e ; colors of lamp or L98 set :ed ?ellow and 3reen. The

controller cabinet consist of the Programmable Logic Controller (PLC) which

act as the main controller power supply safety de"ices and etc. For e"ery

di-erent lamp colors will be assigned with di-erent output address. This

means that for < 6unction traDc light which consist of < traDc light tower

will ha"e 17 di-erent output address which each lamp output address are

set and listed as in Table 1.1 below.

As for the operation layout there will ha"e 17 state and 17 transition

in e"ery cycle. 8etails of the state and transition will be discussed later.

3enerally at one time there will be only 1 6unction with green light while

E


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the rest will be red light.

Table 1.1 nput#/utput assignments.

IN)UTNo. Name 'ddress Descri!tion

1 ,TA:T 7. ,TA:T P$,0 G$TT/H

# To ,TA:T the system operation7 ,T/P 7. 1 ,T/P P$,0 G$TT/H

# To ,T/P the system immediately in

case of emergency

OUT)UTNo. Name 'ddress Descri!tion

1 HI:98 . Horth Junction K :98 Light7 HI?9LL/2 . 1 Horth Junction K ?9LL/2 Light; HI3:99H . 7 Horth Junction K 3:99H Light< ,I:98 . ; ,outh Junction K :98 Light= ,I?9LL/2 . < ,outh Junction K ?9LL/2 Light> ,I3:99H . = ,outh Junction K 3:99H Light

9I:98 . > 9ast Junction K :98 Light9I?9LL/2 . 9ast Junction K ?9LL/2 Light

E 9I3:99H . 9ast Junction K 3:99H Light1 2I:98 . E 2est Junction K :98 Light

11 2I?9LL/2 .1 2est Junction K ?9LL/2 Light17 2I3:99H .11 2est Junction K 3:99H Light

ii. Circuitry schematic.

1


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Figure 1.7 Circuitry schematic for the whole system

As shown in Figure 1.7 the four 6unction traDc light consist of se"eral

electrical components which are

1. 9lectrical Lea%age Circuit Grea%er (9LCG) and 5iniature Circuit Grea%er

(5CG)

o Act as the rst le"el of circuit protector. 2ill immediately brea%

the current ow in the circuit if there is any current lea%age.

7. Fuse

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o Act as the second le"el of circuit protector.

;. 8C power supply

o ,upply 8C "oltage to 8C component such as inducti"e sensor

and === timer.

. ; Colors TraDc Light

o :ed ?ellow and 3reen.

. nducti"e sensoro 8etect the present of "ehi"le at the speci ed 6unction.

. === C Timer

o Act as the safety purpose if the PLC fail. The timer will ta%e o"er

the 6ob by switching /H and blin%ing the ?9LL/2 light at all

6unction. This is standard condition to determine that the traDc

light system is down. The use of === C timer because it is a

standalone component which do not need any signal from thePLC to operate. This is useful when the PLC fail or faulty.

Figure 1.; and 1.< shows the wiring diagram at the PLC input and

output port

respecti"ely. The wiring is depend on the address assigned to each light as

shown before in Table 1.1

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i". Timing diagram.

The four 6unction traDc light operation timing diagram is shown in

Figure 1.= below.

Figure 1.= Four 6unction traDc light operation timing diagram.

1=


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". Program se&uential design.

Figure 1.> Program se&uential design (3:AFC9T)

Gased on the Figure 1.> we can assume that there are 1; transition

which will act as the input for 1; state including the H T AL+. The state act

as the output for the program and the program will e!ecute state by state

from 1 to 1; continuously. After ,tate 1;+ a transition with the input of

T 59: 17+ the program will re+e!ecute+ bac% from ,tate 7+. And the

program will e!ecute continuously until ,T/P button is pressed.

1>


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"i. Ladder diagram.

1


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1


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1E


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7


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71


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77


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2.0 %U"&TION $

?our company has recently recei"ed a pro6ect on building a new ,#type

two le"el cargo lift for a warehouse. ?ou are an electrical engineer and a

PLC programmer. ?ou are responsible for the electrical tas%s. The design

must include

7;


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i. ,ystem layout and input#output assignments

ii. Circuitry schematic circuit protectors fuse power supply lamps

(colours) sensors bra%es PLC and / control relay an AC motor

in"erter bu44er lamps and safety protection circuitry

iii. A mar%et part list and costing (with proof of prices such as &uotations)i". 8raw a timing diagram

". Program se&uential design

"i. Ladder diagram (use C@#Programmer if possible)

The lifter door is manually closed by the operator. Ho operator or wor%er

should be inside the lifter during normal operation. The operation of the

lifter is briefly described as followed

1. 2hen the door is closed properly the lifter could lift up or down.

7. 2hen the door is opened during the lifting the system goes into an

emergency halt.

Alert the operator using a bu44er and an indicator.

;. At the moment of lifting the lifter+s speed is slow and then switched to

normal speed.

Gefore reaching to the target the speed is slow again until stopping.


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2.1 'N&("R $

i. ,ystem layout and input#output assignments.

Figure 7.1 Lifter system layout.

Figure 7.1 shows the location of some "ery crucial sensor for the ,#

type cargo lift. For the lift to function as the &uestion intended it has to

ha"e se"eral photoelectric sensors placed at %ey locations. GottomILimit is

placed at the bottom so that it will detect when the lift has reached the

bottom oor. TopILimit is there for the same reason e!cept that it detects

when the lift reaches the top oor. ,peedI1 and ,peedI7 used to informing

the lift that it+s reaching the bottom or the top of the oor and it should

slow down. /pen'Close sensors are used at 8oorI1 and 8oorI7 so that the

system will %now when the doors are open or closed. ,hould the doors open

when the lift is mo"ing the entire system will stopQ a bu44er and indicator

will be acti"ated.

7=


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Figure 7.7 Photoelectric ,ensor

A photoelectric sensor is a de"ice used to detect the distance

absence or presence of an ob6ect by using a light transmitter

often infrared and a photoelectric recei"er. They are used e!tensi"ely in

industrial manufacturing. n this case the sensor will detect the location of

the lift by detecting the presence'absence of a reference point on the lift. This way it is possible to %now the lifts current location and whether it

should slow down and prepare to stop. 2ithout these sensors the lift could

possibly o"ershoot its target since its speed is too fast.

7>


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Table 7.1 nput#/utput assignments.


1 3o 8/2H 7. 3o 8/2H P$,0 G$TT/H

# Lifter go down

7 3o $P 7. 1 3o $P P$,0 G$TT/H# Lifter go up

; TopILimit 7. 7 Photoelectric ,ensor

# Photoelectric sensor located at the

top of the lifter< GottomILimit 7. ; Photoelectric ,ensor

# Photoelectric sensor located at the

bottom of the lifter.

= 8oor 1 7. < :oller P$,0 G$TT/H# To detect wether the door is

open'close> 8oor 7 7. = :oller P$,0 G$TT/H

# To detect wether the door is

open'close

OUT)UT

No. Name 'ddress Descri!tion1 8own ,L/2 . 1 The lifter go down at slow speed7 8own

H/:5AL

. 7 The lifter go down at normal speed

; $p ,L/2 . ; The lifter go up at slow speed< $p H/:5AL . < The lifter go up at normal speed


7


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Figure 7.; Circuitry schematic for the whole system

7


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Figure 7.< PLC nput wiring diagram.

Figure 7.= PLC /utput wiring diagram.

iii. A mar%et part list and costing.

No. Item *rand

%ty RM , Unit Total &o rce

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s#online.com'web'

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i". Timing diagram.

Figure 7.> Lifter operation timing diagram.

". Program se&uential design.

;1


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Figure 7. Program se&uential design (3:AFC9T)

"i. Ladder diagram.

;7


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;;


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4.0 %U"&TION 2

A ba%ery factory is producing cupca%es in large &uantities. As seen from

the gure below cupca%es are &ueuing in row on a con"eyor. The

;


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cupca%es are to be pac%ed into a customi4ed ba%ery bo!. These cupca%es

must be arranged in the format of ; rows and ; columns.

?ou are an electrical engineer and a PLC programmer. ?ou are responsible

for the electrical tas%s. The design must include

i. ,ystem layout and input#output assignmentsii. Circuitry schematic. ,uggest your circuitry including the protection.

iii. A mar%et part list and costing (with proof of prices such as

&uotations)

i". 8raw a timing diagram. ,uggest the se&uences.

". Program se&uential design K or at least list down the se&uences

"i. The ladder diagram (use C@#Programmer if possible)

i. ,ystem layout and nput#/utput assignments

;=


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Figure ;.1 Pneumatic pusher system layout.

Figure ;.1 shows the basic system layout for the Pneumatic

Pusher system. Gasically the system consists of 7 motori4ed belt

con"eyor a set of through beam sensor for detecting the present of

cupca%e a photoelctric sensor to detect bo! 7 position sensor to

detect the location of the cylinder rod and a double acting cylinder

ast as the pusher in the system. All the sensors and actuators are

connected to a PLC which act as the main controller.

Table ;.1 nput#/utput assignments.


1 ,TA:T 7. ,TA:T P$,0 G$TT/H;>


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# To ,TA:T the system operation7 ,T/P 7. 1 ,T/P P$,0 G$TT/H

# To ,T/P the system immediately in

case of emergency; ,ensor

(Con"eyor A)

7. 7 Through Geam ,ensor

# Through Geam sensor located at

Con"eyor A to detect cupca%e

present.< ,ensor

(Con"eyor G)

7. ; Photoelectric ,ensor

# Photoelectric sensor located at

Con"eyor G to detect bo! present

OUT)UTNo. Name 'ddress Descri!tion

1 Con"eyor A . Con"eyor A /H7 Con"eyor G . 1 Con"eyor G /H; Pusher

9!tract

. 7 8ouble acting cylinder e!tract

< Pusher

:etract

. ; 8ouble acting cylinder retract


;


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Figure ;.7 Circuitry schematic for the whole system

;


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Figure ;.; PLC nput wiring diagram.

Figure ;.< PLC /utput wiring diagram.

iii. A mar%et part list and costing.

NO. IT"M *R'ND

%T +

RM ,UNIT TOT'L &OURC"

1 5otori4ed GeltCon"eyor Anhui 7:5>> . :51 ;7 . www.alibaba.co

m

7 CJ15#CP$11 PLC /mron 1 :51E1 .1 /mron 1 :51 >.=>:51 >.=

>www.plcCenter.c

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http://www.alibaba.com/http://www.alibaba.com/http://malaysia.rs-online.com/web/http://malaysia.rs-online.com/web/http://malaysia.rs-online.com/web/http://www.plccenter.com/http://www.plccenter.com/http://www.alibaba.com/http://www.alibaba.com/http://malaysia.rs-online.com/web/http://malaysia.rs-online.com/web/http://malaysia.rs-online.com/web/http://www.plccenter.com/http://www.plccenter.com/


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< CJ12# 8711 /mron 1 :57 =.7 :57 =. 7 www.ebay.com

= Power ,upply 7 7.7 :5> 7.7

http ''malaysia.rs#

online.com'web'

5ain Circuit Grea%er

PH1#15oeller 1 :5> 0#8C

,chneider9lectric 1

:5


41/46


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Figure ;.> Program se&uential design (3:AFC9T)

"i. Ladder 8iagram


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.0 R"F"R"NC"&

1. Petru4ella F. 8. Programmable Logic Controllers 5c3raw 0ill 7 =.

7. Johnson C. 8. Process Control nstrumentation Technology Prentice

0all 7 >.

;. Anderson J. C. 8esign a e!ible industrial controls lab module*


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;7nd Annual Frontiers in 9ducation Nol. 1 pp. 1 K 77 Ho" 7 7.


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Assignment Dr Tee.doc