dr. habeeb hattab habeeb dr. habeeb hattab habeeb office: bn-block, level-3, room-088 email:...

Dr. HABEEB HATTAB HABEEB

Office: BN-Block, Level-3, Room-088

Email: [email protected]. No.: 7292

UNITEN

University TENAGA Nasional Lecturer: Habeeb Al-Ani Lecturer: Dr. HABEEB ALANI University TENAGA Nasional

mailto:[email protected]

http://www.dewittindustries.com/cgibin/ibrowse/images/of_12/animations/mechanical/gear/gear

http://www.dewittindustries.com/cgibin/ibrowse/images/of_12/animations/mechanical/gear/gear

University TENAGA National

College Of EngineeringMechanical Department

Academic Year – 2008-2009Lecture NoteLecture Note

UNITEN


CAMUniversity TENAGA Nasional Lecturer: Habeeb Al-Ani

Computer Aided Manufacturing

UNITEN

Lecturer: Dr. HABEEB ALANI University TENAGA Nasional

4

PLC:

Programmable Logical Controller

1. What is PLC

2. Relay-Device

3. PLC Architecture

4. Programming a PLC


5

What does PLC stand for?

PLC - programmable logic controller

PLC implements logic control functions by means

of a program


6


• Programmable Logic Controller (PLC) is a microprocessor based

system that uses programmable memory to store instructions and

implement functions such as logic, sequencing, timing, counting and

arithmetic in order to control machines and processes.

• The first PLC was developed in 1969 by General Motors.

Microprocessor-based PLC was introduced in 1977 by Allen Bradley.

Definition of PLC


7


• PLC is viewed as a solid-state:

- Digital

- Industrial computer

• PLC is made to fit an industrial environment and for exposure to

hostile conditions, such as:

- Heat

- Humidity,

- Unreliable power

- Mechanical shocks and vibrations.


8

• Unlike Personal Computer, PLC does not contain, such as display or

keyboard, that allow user to directly interact with PLC. In order to

facilitate interaction, separate computer is provided, normally taking

form of a standard PC. Through this external computer, operator can

re-program PLC, provide set-points and view trends of process

variables that are controlled and manipulated by PLC.

PLC Actuator Process

Sensor

ExternalComputer



Before the invention of the Programmable Logic Controller (PLC), most

industrial control was done using relay control panels.

Switches and relays can be arranged in circuits to make logical decisions.

Output from Relay can be used with the following components:

1. Drive “loads” such as motors

2. Heaters, or electromagnetic coils.

A relay control panel is comprised of a single to thousands of these

circuits.

Relay-Devise


• Input relays: These are connected to the outside world. They physically

exist and receive signals from switches, sensors,etc.

- Internal Utility Relays: They are simulated relays that are dedicated

to performing only one task.. Some are on only during power on and

typically used for initializing data that was stored.

• Output Relays: These are connected to the outside world. They

physically exist and send on/off signals to solenoids, lights,etc. They can

be transistors, relays etc.

Relays types


no rm a llyo p e n

no rm a llyc lo se d

inp ut c o il

O R

O R

Relays and Schematic Symbols

12

PLC consists of the following components:

1. Microprocessor – This is the brain of PLC. It reads input signals, executes control program and communicates results (decisions) of control program as action signals to the outputs.

2. Memory – It stores control program that is to be executed at a prescribed rate.

3. Power Supply – This component is used to convert the mains AC voltage to the low DC voltage (e.g. from 240V AC to 5V DC).

Programmable Logic Controller Architecture


13

PLC consists ........Con...

4. Input Module – This component receives information from external devices (sensors). It contains circuitry that provides electrical isolation and signal conditioning functionalities. Input module can be analogue input (AI) or discrete input (DI) module.

5. Output Module – This module communicates control actions to external devices (actuators). It contains circuitry required to interface PLC with actuators (e.g. digital-to-analogue converter and power amplifier).

6. Communication Module – This component allows PLC to communicate with external devices using sophisticated multiple-bit digital communication protocols (e.g. Ethernet).


Power Supply

Communication Module

Microprocessor + Memory

Analogue Input (AI) Module

Discrete Output (DO) Module

Discrete Input (DI) Module

Analogue Output (AO) Module

Analogue Sensor

Discrete Sensor

Analogue Actuator

Discrete Actuator

Operator Workstation

Programmable Logic Controller Architecture

PLC


(PLC) Samples


16Inputs

Outputs & Power Supply

Com

mun

icat

ion

Por

ts (

RS

-485

)


17

Where are PLCs used?

In every industry where automation is involved, from

individual machines to whole processes


18

PLC Applications


19

PLC - IntroductionAn application example 1: Gate Control

PLC can sense a vehicle at the entrance or exit, and

open and close the gate automatically

The current vehicle count is easily determined by

programming a simple counter


20

An application example 2: Conveyor System

PLC can be used to start/stop latching logic for motor

control

Counters can be used for monitoring product amounts


21

Why? PLC differ from a computer?

A computer is optimized for calculation and display tasks

A computer is programmed by specialists

A PLC is designed for (logic) control and regulation tasks

A PLC is programmed by non-specialists

A PLC is well adapted to industrial environment


22

Why are PLCs so common?

They are cost-effective

They are flexible, reliable and compact

They have significant advantages over traditional

control systems based on relay or pneumatics


23

What tasks do PLCs perform?

The logic control tasks such as interlocking,

sequencing, timing and counting (previously

undertaken with relays or pneumatics)

In addition, PLCs can perform a variety of calculation,

communication and monitoring tasks


24

The PLC processor


25

PLC Input/Output Devices


26

PLC Input Devices

Push buttons

Switches (limit switches, level switches, etc.)

Sensors

...


27

PLC Output Devices

Relay contacts

Solenoid valves

Signal devices (such as lamps, alarms, etc.)

Motors

...


28

Programming terminal


29

Programming is done through programming terminal

Programming terminal translates engineering

language (logic control) to machine language (binary

code)


30

Programming through standard computer

Most PLC manufacturers offer software packages that

allow a standard computer to be used as a

programming terminal


31

Programming through standard computer


32

Program steps- to inputs and outputs

The CPU reads the data from the inputs

The program in the CPU uses the inputs to

evaluate the control logic. As the program

runs, the CPU updates the data

The CPU writes the data to the output


33

Data Flow in the PLC


34

One of the advantages of PLC is that it can be

programmed by non-specialists

Program can be written either in the form of a

statement list: a set of mnemonic instructions

representing a function of the CPU

or

a ladder diagram: a graphical language

resembling the electrical relay diagrams

Advantages of PLC


35

PLC Forms:

1. Rack

2. Mini

3. Shoebox

4. Micro

5. Software


THANK YOU


dr. habeeb hattab habeeb dr. habeeb hattab habeeb office: bn-block, level-3, room-088 email:...

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