logic control with plc

8/10/2019 logic control with plc

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FAKULTAS TEKNOLOGI INDUSTRI

ITSSURABAYA

201423/05/2014 1Instrument 2


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MATERI :

Konsep dasar Programmable Logic Control

Sequential Process

Safety Instrument System (SIS)

SCADA

23/05/2014 2Instrument 2


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Konsep dasar PLC

Invented in 1968

as a substitute for hardwired relay panels.

"A digitally operating electronic apparatus which uses a programmable

memory for the internal storage of instructions by implementing specific

functions such as logic sequencing, timing, counting, and arithmetic to

control, through digital or analog input/output modules, various types ofmachines or processes. The digital computer which is used to perform the

functions of a programmable controller is considered to be within this

scope. Excluded are drum and other similar mechanical sequencing

controllers."

National Electrical Manufacturing Association (NEMA)23/05/2014 3Instrument 2


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CPU

System

User LadderDiagram

Workingmemoryregisters

Input

Flag

Output

InputModule

OutputModule

Komponen PLC



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The main module measures

19 x 20 x 14.5.

have up to 10,000 I/O points

supports all functions

expansion slots toaccommodate PC and other

communication devices.

A large size PLC

Allan-Bradley PLC-3

A small size PLC

Measures 4.72x 3.15 x 1.57.

32 I/O points

Standard RS 232 serialcommunication port

Allan-Bradley Micrologic-100023/05/2014 5Instrument 2


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DPSTSPDT

N o n -lo c k in g Lo c k in g

No r m a lly O p e n No r m a lly C lo

s e d

Mu ltip le Th r o w

P 1

P 2

Mu ltip le P o l

e

Br e a k - b e fo r e - m a k

e Ma ke -b e fo re -b r

e a k

SWITCHES



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Throw - number of states

Pole - number of connecting moving parts (number of individual

circuits).

SPDT

DPST

A serial switch box (A-B box) hastwo 25 pin serial ports to switch from.

Input

Output

A B

Knob

How is this switch classified?

TERMS



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Selector switches

Pushbutton switches

Photoelectricswitches

Limit Switches

Proximity switches

Level switches Thumbwheel

switches

Slide switches

RATING:

24 Volts AC/DC48 Volts AC/DC120 Volts AC/DC

230 Volts AC/DCTTL level(Transistor-to-transistor5V)

Isolated Input

TYPES OF SWITCHES



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A switch whose operation is activated by an electromagnet is called a "relay"

contact

coil

input

Relay coil

R1

R1Output contact

RELAYS



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Digital counters output in the form of a relay contact when a preassigned count value is

reached.

Register

Accumulator

contact

input

reset

outpu

Input

Reset

Output

Count 0 1 2 3 4 5 0 1

5

COUNTER



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A timer consists of an internal clock, a count value register, and an accumulator. It is

used for or some timing purpose.

Clock

Accumulator

contact

reset

outpu

Register

Contact

Time 5 seconds.

Clock

Reset

Output

Count 1 2 3 40 5

TIMER



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L1

LS1 PB1 LS2 R1

R1

R1TIMER

R2

PR=5

For a process control, it is desired to have the process start (by turning on a motor)five seconds after a part touched a limit switch. The process is terminatedautomatically when the finished part touches a second limit switch. An emergencyswitch will stop the process any time when it is pushed.

LS1

PB1LS2

R1

TIMER

5Motor

R2

AN EXAMPLE OF RELAY LOGIC



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Programmable controllers replace most of the relay panel wiring by software programming.

Processor I/O

Modules

MemoryPower

Supply

Program

Loader

Printer

CassetteLoader

EPROM

Loader

Switches

Machines

Peripherals Exter nal Device

PC

A typical PLC

PLC ARCHITECTURE



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1. Processor Microprocessor based, may allow arithmetic

operations, logic operators, block memory moves,computer interface, local area network, functions, etc.

2. Memory Measured in words.

ROM (Read Only Memory),

RAM (Random Access Memory),PROM (Programmable Read Only Memory),

EEPROM (Electric Erasable Programmable ROM),

EPROM (Erasable Programmable Read Only Memory),

EAPROM (Electronically Alterable Programmable

Read Only Memory), and

Bubble Memory.

PLC COMPONENTS



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3. I/O Modular plug-in periphery

AC voltage input and output,

DC voltage input and output,

Low level analog input,

High level analog input and output,

Special purpose modules, e.g., high speed timers,

Stepping motor controllers, etc. PID, Motion

4. Power supply AC power

5. Peripheral hand-held programmer (HHP)

CRT programmer

operator console

printer

simulator

EPROM loader

graphics processor

network communication interface

modular PC

PLC COMPONENTS



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AC Voltage I/O DC Voltage I/O

numerical input and output

special-purpose modules, for example,high-speed timers, and stepping motorcontrollers

Discrete I/O



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Analog inputs: Flow sensors Humidity sensors Potentiometers Pressure sensors

Temperature sensors

Analog outputs: Analog meters Analog valves and actuators DC and AC motor drives

Analog I/O



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Thermocouple input

Low level analog signal, filtered, amplified, and digitizedbefore sending to the processor through I/O bus. Fast input

50 to 100 microsecond pulse signal detection. ASCII I/O

Communicates with ASCII devices. Stepper motor output

Provide directly control of a stepper motor. Servo interface

Control DC servo motor for point-to-point control and

axis positioning. PID control

The Proportional Integral Derivative is used for closedloop process control.

Network module

Some special I/O



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n Allen-Bradley hand-held programmer for MicroLogix 1000

A Hand Held Programmer



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A ladder diagram (also called contact symbology) is a means of graphically

representing the logic required in a relay logic system.

A

R1

PB1 PB2

R1

R1

start emergency stop

Rail

Rung

Ladder diagram



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Externalswitches

Stored program

01 02 20

20

2011

01

02

03

11

12

C

PLCInput OutputA

B

PLC WIRING DIAGRAM



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AC DC TTL

Input Connections



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AC DC TTL

Output Connections



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A PLC resolves the logic of a ladder diagram (program) rung by rung, from the top to

the bottom. Usually, all the outputs are updated based on the status of the internalregisters. Then the input states are checked and the corresponding input registers are

updated. Only after the I/Os have been resolved, is the program then executed. This

process is run in a endless cycle. The time it takes to finish one cycle is called the

scan time. In some controllers the idle state is eliminated. In this case, the scan time

varies depends on the program length.

begin

Input

Output

Resolvelogic

Idle

Scan cycle

SCAN



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Ladder Diagram - most common

Structure Text Programming (ST)

Functional Block Programming (FB)

Instruction List (IL)

Sequential Function Chart (SFC)

PLC Programming



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1) Relay,

2) Timer and counter,

3) Program control,

4) Arithmetic,

5) Data manipulation,

6) Data transfer, and

7) Others, such as sequencers.

PLC Ladder Diagram INSTRUCTIONS



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ON : TRUE, contact closure, energize, etc.

OFF: FALSE, contact open , de-energize, etc.

(In the notes we use the symbol "~" to represent negation. AND

and OR are logic operators. )

Do not confuse the internal relay and program with the externalswitch and relay. Internal symbols are used for programming.External devices provide actual interface.

LOGIC STATES



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PB1 R1PB2

R2

R1 = PB1.AND.PB2

R2 = PB2.AND.~PB4

PB3 PB4

PB1 R1

PB2

R1 = PB1 .OR. PB2

AND

OR

AND and OR LOGIC



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

PB1 R1

PB2 pb3

COMBINED AND & OR



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Coil:

e. Retentive memory Coil -(M)-

f. Set retentive memory Coil -(SM)-

g. Reset retentive memory Coil -(RM)-

h. Positive Transition-sensing Coil -(P)-

h. Negative Transition-sensing Coil -(N)-

(set coil latches the state, reset coil deenergize the set coil. retentive

coil retain the state after power failure.)

Relay (continue)



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Timers:

a. Retentive on delay -(RTO)-

b. Retentive off delay -(RTF)-

c. Reset -(RST)-

Counter:

a. Counter up -(CTU)-

b. Counter down -(CTD)-c. Counter reset -(CTR)-

RTO counting stop countingresume

RTF stop counting stop

True False True

Input

RTO reach PR value, output ONRTF reach PR value, output OFF

PR value in 0.1 second

TIMERS AND COUNTERS



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Sequencers are used with machines or processes involving repeating

operating cycles which can be segmented into steps.

Output

Step A B C Dwell time

1 ON OFF OFF 5 sec.

2 ON ON OFF 10 sec.

3 OFF OFF ON 3 sec.

4 OFF ON OFF 9 sec.

SEQUENCER



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I/O points are numbered, they correspond to the I/O slot on the PLC.

For A-B controller used in our lab

I/O uses 1-32

Internal relays use 033 - 098

Internal timers/counters/sequencers use 901-932

Status 951-982

A-B PLC



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Part

microswitch

Bar code reader

Stopper

Conveyor

MachineRobot

id description state explanation

MSI microswitch 1 part arrive

R1 output to bar code reader 1 scan the part

C1 input from bar code reader 1 right part

R2 output robot 1 loading cycle

R3 output robot 1 unloading cycle

C2 input from robot 1 robot busy

R4 output to stopper 1 stopper up

C3 input from machine 1 machine busy

C4 input from machine 1 task complete

PROGRAMMING EXAMPLE 1



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0102

03

04

05

1112

13

14

15

InputOutput

ProgrammableControllerPLC

MS1

C1

C2

C3

C4

R1R2

R3

R4

01 14 11

02

14 04 03

14

12

1305 03

Rung 1. If part arrives and no part

is stopped, trigger the bar codereader.

Rung 2. If it is a right part, activatethe stopper.

Rung 3. If the stopper is up, themachine is not busy and therobot is not busy, load the partonto the machine.

Rung 4. If the task is completed andthe robot is not busy, unload themachine.

SOLUTION



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logic control with plc