Lecture1 Plc

BDA 2811 MECHANICAL ENGINEERING PRACTICE IV

PROGRAMMABLE LOGIC CONTROLLER (PLC) Prepared by: Saliana binti Sanusi DEPARTMENT OF MANUFACTURING & INDUSTRIAL ENGINEERING FACULTY OF MECHANICAL & MANUFACTURING ENGINEERING 08/09/09

FACULTY OF TECHNOLOGY MANAGEMENT - PGD 2008 UNIVERSITI TUN HUSSEIN ONN MALAYSIA

1

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

POWER SWITCH

PLC

PERIPHERAL PORT

INPUT/OUTPUT CARD

RS 232 CABLE

INPUT TERMINALS

EARTH TERMINAL

V+ TERMINAL

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 data PLC 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

Food & Beverages

Process Control

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.

Ladder Logic Structure 24 V+

RAIL

0V, COMMON

RUNG

BRANCH INPUT

OUTPUT

Ladder Logic Symbols & IO Address INPUT

OUTPUT

Normally Open Normally contact Close contact

Normally Open contact

Normally Close contact

IP address: 0.00 to 0.15

IP address: 1.00 to 1.15

Sensor

Cylinder

Limit Switch

Buzzer

Push button

Solenoid

Timer & Counter

Simple Application 0.04 Switch

Lamp 1

1.07 1.10

Lamp 2 1.15 Solenoid

The ladder logic program

In actual……

Lamp 1 DC supply

Lamp 2

Switch

AC supply

Relay

Solenoid

Hardwire Circuit 24+V Lamp 1

Lamp 2

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 0V, common

Solenoid

• 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 cxprogrammer) using printer in the lab.