osp07 programmable logic controller

D e pa r t e m e n Te k nik I ndust r i FTI - I TB

TI -3222: Otomasi Sistem Produksi
Pr ogr a m m a ble Logic Con t r olle r

Laborat orium Sist em Produksi
www.lspit b.org
©2004

D e pa r t e m e n Te k nik I ndust r i FTI - I TB

Hasil Pembelajaran


Um um



Khusus

ƒ Mahasiwa m am pu unt uk m elakukan proses perancangan

sist em ot om asi, sist em m esin NC, sert a m erancang dan
m engim plem ent asikan sist em kont rol logika.

ƒ Mem aham i fungsi PLC sert a kom ponen- kom ponen PLC

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PURPOSE OF Programmable
Logic Controllers (PLCs)


I nit ially designed t o replace relay logic boards





Accept s input from a series of swit ches
Sends out put t o devices or relays

ƒ Sequence device act uat ion
ƒ Coordinat e act ivit ies

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PURPOSE OF Programmable
Logic Controllers (PLCs)


I nit ially designed t o replace relay logic boards





Accept s input from a series of swit ches
Sends out put t o devices or relays

ƒ Sequence device act uat ion
ƒ Coordinat e act ivit ies

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FUNCTI ONS OF CONTROLLERS







1) on- off cont rol,
2) sequent ial cont rol,
3) feedback cont rol, and
4) m ot ion cont rol.

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CONTROL DEVI CES
1) m echanical cont rol - cam , governor, et c.,
2) pneum at ic cont rol - com pressed air, valves,
et c.
3) elect rom echanical cont rol - swit ches, relays,

a t im er, count ers, et c,
4) elect ronics cont rol - sim ilar t o
elect rom echanical cont rol, except uses
elect ronic swit ches.
5) com put er cont rol.

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PROGRAMMABLE LOGI C
CONTROLLER
Invented in 1968 as a substitute for hardwired relay panels.
" A digit ally operat ing elect ronic apparat us which uses a
program m able m em ory for t he int ernal st orage of
inst ruct ions by im plem ent ing specific funct ions such as logic

sequencing, t im ing, count ing, and arit hm et ic t o cont rol,
t hrough digit al or analog input / out put m odules, various
t ypes of m achines or processes. The digit al com put er which
is used t o perform t he funct ions of a program m able
cont roller is considered t o be wit hin t his scope. Excluded
are drum and ot her sim ilar m echanical sequencing
cont rollers."
National Electrical Manufacturing Association (NEMA)

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VENDORS









Rockwell
GE/ Fanuc
Schnieder
MODI COM - GOULD
ALLEN- BRADLEY
Honeywell
SQUARE- D

et c.

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PLC
Input

CPU

Input
Module

Flag
System
Output

Output
Module

User Ladder
Diagram


Working
memory
registers

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PLC Configuration

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What devices does a PLC interact with?






I NPUT RELAYS- ( cont act s) These are connect ed t o t he out side
world. They physically exist and receive signals from swit ches,
sensors, et c. Typically t hey are not relays but rat her t hey are
t ransist ors.
I NTERNAL UTI LI TY RELAYS- ( cont act s) These do not receive
signals from t he out side w orld nor do t hey physically exist .
They are sim ulat ed relays and are what enables a PLC t o
elim inat e ext ernal relays. There are also som e special relays
t hat are dedicat ed t o perform ing only one t ask. Som e are
always on while som e are always off. Som e are on only once
during pow er- on and are t ypically used for init ializing dat a
t hat was st ored.
COUNTERS- These again do not physically exist . They are

sim ulat ed count ers and t hey can be pr ogram m ed t o count
pulses. Typically t hese count ers can count up, down or bot h
up and down. Since t hey are sim ulat ed t hey are lim it ed in
t heir count ing speed. Som e m anufact urers also include highspeed count ers t hat are hardware based. We can t hink of
t hese as physically exist ing. Most t im es t hese count ers can
count up, down or up and down.
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What devices does a PLC interact with?
Continued






TI MERS- These also do not physically exist . They com e in m any
variet ies and increm ent s. The m ost com m on t ype is an on- delay
t ype. Ot hers include off- delay and bot h ret ent ive and nonret ent ive t ypes. I ncrem ent s vary from 1m s t hrough 1s.
OUTPUT RELAYS- ( coils) These are connect ed t o t he out side world.
They physically exist and send on/ off signals t o solenoids, light s,
et c. They can be t ransist ors, relays, or t riacs depending upon t he
m odel chosen.
DATA STORAGE- Typically t here are regist ers assigned t o sim ply
st ore dat a. They are usually used as t em porary st orage for m at h
or dat a m anipulat ion. They can also t ypically be used t o st ore
dat a when power is rem oved from t he PLC. Upon power- up t hey
will st ill have t he sam e cont ent s as before power was rem oved.
Very convenient and necessary! !

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SWI TCHES

Non-locking

Locking

Normally Open

Normally Closed

P1

SPDT

DPST

P2
Multiple Throw

Multiple Pole

Break-before-make

Make-before-break

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TERMS
Th r ow - n u m be r of st a t e s
Pole
- n u m be r of con n e ct in g m ovin g pa r t s ( n u m be r of
in dividu a l cir cu it s) .
A serial switch box (A-B box) has
two 25 pin serial ports to switch from.
SPDT
A

B
Output

Input

DPST

Knob
How is this switch classified?
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TYPES OF SWI TCHES
1. Basic swit ch, operat ed by a m echanical level,
2. Push- but t on swit ch,
3. Slide swit ch,
4. Thum bwheel swit ch,
5. Lim it swit ch,
6. Proxim it y swit ch, and
7. Phot oelect ric swit ch.

RATING: voltage, current
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RELAYS
A switch whose operation is activated by an electromagnet is called a "relay"

contact

coil

input

Relay coil

Output contact

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COUNTER
Digit al count ers out put in t he form of a relay cont act when a
preassigned count value is reached.
input

5

Register

Accumulator
reset
contact
output

Input
Reset
Output
Count

0

12

3

0

5

4

1

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TI MER
A t im er consist s of an int ernal clock, a count value regist er, and an
accum ulat or. I t is used for or som e t im ing purpose.

Clock

Accumulator
reset
Register
Clock

contact
Contact
output

Reset
Output
Count

0

1

2

3

4

Time 5 seconds.
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AN EXAMPLE OF RELAY LOGI C
For process cont rol, it is desir ed t o have t he process st art ( by t urning on a
m ot or) five seconds aft er a part t ouches a lim it swit ch. The process is
t er m inat ed aut om at ically when t he finished part t ouches a second lim it
sw it ch. An em ergency sw it ch will st op t he process any t im e when it is
pushed.
L1
LS1

PB1

LS2

R1

R1

R1

TIMER

R2

PB1
LS1

LS2

PR=5

TIMER
5

R1

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Motor
R2

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PLC ARCHI TECTURE
Program m able cont rollers replace m ost of t he relay panel wiring by
soft ware program m ing.

Program
Loader

PC
Switches

Printer
Processor

I/O
Modules

Memory

Power
Supply

Machines

Cassette
Loader
EPROM
Loader

External Devices

Peripherals

A typical PLC

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PLC COMPONENTS
1. Processor

Microprocessor based, m ay allow ar it hm et ic
operat ions, logic operat or s, block m em ory m oves,
com put er int er face, local area net wor k , funct ions, et c.

2. Mem ory

Measured in w ords.
ROM ( Read Only Mem ory) ,
RAM ( Random Access Mem or y) ,
PROM ( Pr ogram m able Read Only Mem or y) ,
EEPROM ( Elect ronically Erasable Pr ogram m able
ROM) ,
EPROM ( Erasable Pr ogram m able Read Only Mem ory ) ,
EAPROM ( Elect ronically Alt erable Pr ogram m able
Read Only Mem or y) , and
Bubble Mem or y.

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PLC COMPONENTS
3. I / O

Modular plug- in periphery
AC volt age input and out put ,
DC volt age input and out put ,
Low level analog input ,
High level analog input and out put ,
Special purpose m odules, e.g.., high speed t im ers,
St epping m ot or cont rollers, et c. PI D, Mot ion

4. Power supply AC power
5. Peripheral

Hand held program m er ( loader) ,
CRT program m er,
Operat or console,
Print er,
Sim ulat or,
EPROM loader,
Casset t e loader,
Graphics processor, and
Net work com m unicat ion int erface. MAP, LAN
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LADDER DI AGRAM
A ladder diagram ( also called cont act sym bology) is a m eans of
graphically represent ing t he logic required in a relay logic
syst em .

Rail
start
PB1

emergency stop
PB2
R1

Rung

R1

R1
A

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Ladder Representation

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PLC WI RI NG DI AGRAM

Input
01
02

Output

PLC
01

02

20

11

A

12
20

03
11

20

External
switches

Stored program

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SCAN
A PLC resolv es t he logic of a ladder diagram ( program ) rung by rung, from
t he t op t o t he bot t om . Usually , all t he out put s are updat ed based on t he
st at us of t he int ernal regist er s. Then t he input st at es are check ed and t he
cor responding input regist er s are updat ed. Only aft er t he I / Os have been
resolved, is t he program t hen execut ed. This process is run in a endless
cy cle. The t im e it t akes t o finish one cy cle is called t he scan t im e.

Output
Input
begin
Idle
Scan cycle

Resolve
logic
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PLC I NSTRUCTI ONS
1) Relay,
2) Tim er and count er,
3) Program cont rol,
4) Arit hm et ic,
5) Dat a m anipulat ion,
6) Dat a t ransfer, and
7) Ot hers, such as sequencers.

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LOGI C STATES
ON : TRUE, cont act closure, energize, et c.
OFF: FALSE, cont act open , de- energize, et c.

Do not confuse the internal relay and program with the external
switch and relay. Internal symbols are used for programming.
External devices provide actual interface.
(In the notes we use the symbol "~" to represent
negation. AND and OR are logic operators. )

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AND and OR LOGI C
PB2

PB1

R1
R1 = PB1.AND.PB2

AND

PB4

PB3

R2
R2 = PB2.AND.~PB4

R1

PB1

R1 = PB1 .OR. PB2

OR

PB2

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COMBI NED AND & OR

R1 = PB1 .OR. (PB2 .AND. PB3)

R1

PB1

PB2

pb3

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Relay diagram symbols

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Relay diagram symbols

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RELAY
A Relay consists of two parts, the coil and the contact(s).
Cont act s:
a. Norm ally open

-| | -

b. Norm ally closed

-| / | -

c. Off- on t ransit ional

-| ↓ | -

d. On- off t ransit ional

- | ↑| -

Coil:
a. Energize Coil

-( )-

b. De- energize

-(/ )-

c. Lat ch

- ( L) -

d. Unlat ch

- ( U) -

()

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TI MERS AND COUNTERS
I n pu t
Tim ers:
a. Ret ent ive on delay
b. Ret ent ive off delay
c. Reset

- ( RTO) - ( RTF) - ( RST) -

Tr u e

Fa lse

Tr u e

RTO

count ing

st op

count ing
r e su m e

RTF

st op

count ing

st op

RTO r e a ch PR va lu e , ou t pu t ON
RTF r e a ch PR va lu e , ou t pu t OFF

Count er:

PR value in 0.1 second
a. Count er up
b. Count er down
c. Count er reset

- ( CTU) - ( CTD) - ( CTR) -

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SEQUENCER
Sequencers are used with machines or processes involving
repeating operating cycles which can be segmented into
steps.

Ou t pu t
St ep

A

B

C

Dw ell t im e

1

ON

OFF

OFF

5 sec

2

ON

ON

OFF

10 sec

3

OFF

OFF

ON

3 sec

4

OFF

ON

OFF

9 sec

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A-B PLC
I / O point s are num ber ed, t hey correspond t o t he I / O slot on
t he PLC.

For A- B cont roller used in our lab
I/O

uses 1- 32

I nt ernal relays use 033 - 098
I nt ernal t im ers/ count ers/ sequencers use 901- 932
St at us 951- 982

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Programming a PLC

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Ladder Logic for Tank

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Logic for Ladder Solution

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How does it work?

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PROGRAMMI NG EXAMPLE 1
Bar code reader
microswitch

Stopper
Conveyor

Part

Robot

id

Machine

D e scr ipt ion

St a t e

Ex pla na t ion

MSI

m icro swit ch

1

part arrive

R1

out put t o bar code reader

1

scan t he part

C1

input from bar code reader

1

right part

R2

out put robot

1

loading cycle

R3

out put robot

1

unloading cycle

C2

input from robot

1

robot busy

R4

out put t o st opper

1

st opper up

C3

input from m achine

1

m achine busy

C4

input from m achine

1

t ask com plet e

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SOLUTI ON

Input
MS1
C1
C2
C3
C4

Output

01
02

11
12

03
04

13
14

Programmable
Controller
PLC

05

15

R1
R2
R3



R4




01

11

14

14

02

14

04

05

03

03

12


13

Ru n g 1 . I f part
arrives and no part is
st opped, t rigger t he
bar code reader.
Ru n g 2 . I f it is a
right part , act ivat e t he
st opper.
Ru n g 3 . I f t he
st opper is up, t he
m achine is not busy
and t he robot is not
busy, load t he part
ont o t he m achine.
Ru n g 4 . I f t he t ask is
com plet ed and t he
robot is not busy,
unload t he m achine.

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Jefferson street

EXAMPLE 2 TRAFFI C LI GHTS
Main street

Cycle t im e
St reet

Red

Yellow

Green

Main

3

1

4

Jefferson

5

1

2

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WI RI NG DI AGRAM
input

output
64

Programmable
Controller

Jefferson Red

65

Jefferson Yellow

66

Jefferson Green

67

Main Red

70

Main Yellow

71

Main Green

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PROGRAM (1)
901
RTO

RUNG1
901

RUNG2
901

901
902

67

RUNG3

RTO
901

RUNG5
901

RUNG6

902
903

66

J. Green
903

RTO
901

RUNG8
902

903

20

RST

904

M. Green

71

RUNG9

904

71

RUNG10

30

RST

66

RUNG7

M. Red
902

67

RUNG4

80

RST

RTO
901

RUNG11
904

904

40

RST

905

70

RUNG12

M. Yellow

45

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PROGRAM (2)
RUNG13

905

70

RTO
901

RUNG14
903

905
906

65

RUNG15

RUNG16

RUNG18

RUNG19
RUNG 20

J. Yellow

906

65
901

RUNG17

10

RST

RTO

906

10

RST
902

907

64
907
RTO

64
901

907

J. Red

50

RST

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