04/08/23 FACULTY OF TECHNOLOGY MANAGEMENT - PGD 2008

1UNIVERSITI TUN HUSSEIN ONN MALAYSIAUNIVERSITI TUN HUSSEIN ONN MALAYSIAUNIVERSITI TUN HUSSEIN ONN MALAYSIA

BDA 2811MECHANICAL ENGINEERING PRACTICE IV

PROGRAMMABLE LOGIC CONTROLLER (PLC)

Prepared by: Saliana binti Sanusi

DEPARTMENT OF MANUFACTURING & INDUSTRIAL ENGINEERINGFACULTY OF MECHANICAL & MANUFACTURING ENGINEERING

Learning Outcome

After finish this task, students are able to:• Write PLC definition

• List PLC language and program

• Identify input/output address and device classification

• Draw PLC configuration & structure

• Design simple program & assemble input/output devices with single output

What is PLC?

• Definition:

A programmable logic controller (PLC) is a

specialized computer used to control

machines and process

• It uses a programmable memory to store instructions and specific functions that include on/off control, timing, counting, sequencing, arithmetic and data handling.

How does PLC look like?

PLC system

PLC configuration (training kit)

OUTPUT TERMINALS

INPUT/OUTPUT CARD

INPUT TERMINALS V+ TERMINALEARTH TERMINAL

PERIPHERAL PORT

RS 232 CABLE

PLC

POWER SWITCH

Courtesy from OMRON PLC

Processor (CPU)

• Is a ‘brain’ of the PLC• Consists of microprocessor for

implementing the logic and controlling the communications among the modules

• Designed so the desired circuit can be entered in relay ladder logic form

• The processors accepts input data from various sensing devices, executes the stored user program and send appropriate output commands to control devices

Memory System

• The memory system stores both the control and data from the equipment connected to the PLC.

• For storage of programs, present PLC use semiconductor memory devices such as RAM or a programmable read-only memory (ROM)

PLC can process dataPLC can memory

But how we communicate with PLC?

Can PLC talks to us?

How can we tell PLC what we want?

PLC Language

• It is a medium where we can write program• To program means set command or to instruct

the PLC what to do• There are several programming methods, such

as ‘Ladder Diagram’, ‘Statement List’, ‘Mnemonic Code’, ‘Functional Block’ and ‘Block Diagram’

• Several software available in markets are such as OMRON with CX-programmer, SIEMENS with TISOFT, FESTO with FST and Allen-Bradley with RSLogix

Input/Output (I/O) Units• I/O units form the interface between the PLC and

outside devices. • This unit received any input signal, converts it

into low voltage signal and sent it to the processor.

• The processor determines and interprets the data due to the program.

• Then the processor sent the data to the output unit.

• The output unit produce out the output signal and sent it to the output device

• For easy assessment, every input/output has their own adddress.

PLC applications

Automatic Storage Process Control

Food & Beverages Wrapping & Packaging

Quality Control

Machine System

Automotive Assembly

Parking System

Automated Material Handling

Advantages of PLC control system

• Eliminates much of the hard wiring that was associated with conventional relay control circuit

• More flexibility• Increased reliability• Communications capability• Faster response time• Easier to troubleshoot• Lower costs

Limitation

• PLC is not suitable for analogue application

PLC Language

• Concentrate on ‘ladder logic diagram’

• A ladder diagram is a means of graphically representing the logic required in a relay logic system.

0V, COMMON24 V+

RUNG

BRANCH

INPUT OUTPUT

Ladder Logic Structure

RAIL

Ladder Logic Symbols & IO Address

INPUT OUTPUT

Normally Open contact

Normally Close contact

Normally Open contact

Normally Close contact

Timer & Counter

IP address: 0.00 to 0.15 IP address: 1.00 to 1.15

Sensor Cylinder

Limit Switch Buzzer

Push button Solenoid

Simple Application

SwitchLamp 1

Lamp 2

Solenoid

The ladder logic program

0.04

1.07

1.10

1.15

In actual……

DC supply

Relay

Lamp 2Lamp 1

AC supply

Solenoid

Switch

Hardwire Circuit

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

CPU

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Switch

Lamp 1 Lamp 2 Solenoid

24+V

0V, common

• Assignment 1 & lab report submit on/before 14 AUGUST 2009 to En Omar.

TIPS: assignment 1

• Host having reset button

• Using latching for each group of contestants

• Just a simple circuit

You may access the lab on any time (refer to the schedule outside the room)

Print out your program (drawing using cx-programmer) using printer in the lab.