GSM Based Remote Appliance Control System

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SSGBCOET,BHUSAWAL.

2012

GSM BASED

REMOTE APPLIANCE

CONTROL SYSTEM

Hardik Jasani

N O R T H M A H A R A S H T R A U N I V E R S I T Y


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Project Report

On

GSM BASED REMOTE APPLIANCE CONTROL

SYSTEM

Submitted by

JASANI HARDIK CHHAGANBHAI

YADAV AKHILESH BAHADUR

VIJAY KUMAR

In partial fulfilment of the award of

Bachelor of Engineering

(Electronics & Communication Engineering)

NORTH MAHARASHTRA UNIVERSITY, JALGAON

Department of Electronics & Communication Engineering

SHRI SANT GADGE BABA

COLLEGE OF ENGINEERING & TECHNOLOGY,

BHUSAWAL

(2011 - 2012)


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CERTIFICATE

This is to certify that the project entitled GSM BASED REMOTE

APPLIANCE CONTROL SYSTEM which is being submitted herewith for the award

of the Degree of Bachelor of Engineering in Electronics & Communication

Engineering of North Maharashtra University, Jalgaon. This is the result of the original

research work and contribution by Jasani Hardik Chhaganbhai, Yadav Akhilesh

Bahadur and Vijay Kumar under my supervision and guidance. The work embodied in

this report has not formed earlier for the basis of the award of any degree of compatible

certificate or similar title of this for any other examining body of university to the best of

knowledge and belief.

Place:

Date:

Prof. S. D. Deshmukh Prof. G. A. Kulkarni

Guide Head of the Department

Dr. R. P. Singh

Principal


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TABLE OF CONTENTS

CHAPTER Page No.

I. List of Abbreviations i

II. List of Figures ii

III. List of Tables iii

1. INTRODUCTION

1.1 Introduction 1

1.2 Necessity 2

1.3 Objectives 2

1.4 Theme 2

1.5 Organization 3

2. LITERATURE SURVEY2.1 Home Automation 4

2.2 Mobile Communication 10

2.3 GSM Architecture 12

3. SYSTEM DEVELOPMENT

3.1 Design of Power Section 18

3.2 Design of Relay Section 19

3.3 Design of Main Controller Board 21

3.4 Circuit Layouts 35

3.5 PCB Layouts 363.6 System Software Design 39

4. PERFORMANCE ANALYSIS

4.1 First Installation 46

4.2 Routine Operation 47

4.3 Control Words 47

4.4 Results 48

4.5 Timing States 49

5. CONCLUSION

5.1 Conclusions 505.2 Future Scope 50

5.3 Applications 51

5.4 Advantages 51

5.5 Limitations 52

REFERENCE 54

APPENDICES A-1

ACKNOWLEDGEMET


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i

LIST OF ABBREVIATIONS

AC Air Conditioner

AMPS Advanced Mobile Phone System

CAD Computer Aided Designing

CCTV Closed Circuit Television

CDMA Code Division Multiple Access

CMOS Complementary Metal Oxide Semiconductor Devices

CPU Central Processing Unit

DIY Do-It-Yourself

DSP Digital Signal Processors

EEPROM Electrically Erasable Programmable Read Only Memory

EDGE Enhanced Data rate for GSM Evolution

ETSI European Telecommunications Standards Institute

EV-DO EvolutionDigital Only

FPGA Field Programmable Gate Array

GMSK Gaussian Minimum Shift Keying

GPRS General Pocket Radio Service

GPS Global Positioning System

GSM Global System for Mobile Communication

HA Home Automation

IDE Integrated Development Environment

ISP InSystem Programming

LAN Local Area Network

LED Light Emitting Diode

LPC Linear Predictive Coding

PCB Printed Circuit Board

PDA Personal Digital Assistant

PEROM Programmable and Erasable Read Only Memory

RAM Random Access Memory

ROM Read Only MemorySIM Subscribers Identity Module

SMS Short Messaging Service

SMSC SMS Center

TCP Transmission Control Protocol

TDMA Time Division Multiple Access

TTL Transistor-Transistor Logic

UART Universal Asynchronous Receiver Transmitter

USIM Universal Subscriber Identity Module


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LIST OF FIGURES

Figure No. Figure Name Page No.

1.1 Basic project organization 3

2.1 Sonos Wireless Music Centre Components 6

2.2 GSM Architecture 14

2.3 SIM card 16

3.1 Circuit diagram of power supply section 19

3.2 ULN 2803 pin configuration 19

3.3 HKE make JQC-3FC/T73 12VDC 20

3.4 Atmel AT89C52 22

3.5 89S52 Block Diagram 243.6 Clock generation circuitry 32

3.7 Pull-up network 32

3.8 Reset circuitry 33

3.9 Pin diagram of MAX232 34

3.10 Main controller board circuit 35

3.11 Relay board circuit 36

3.12 Power supply circuit 36

3.13 PCB layout of main controller board 37

3.14 PCB layout of Relay board 38

3.15 PCB layout of power supply board 38

3.16 Keil Vision IDE 40

3.17 Flowchart of system code 41


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LIST OF TABLES

Table No. Table Name Page No.

3.1 Relay characteristics 20

3.2 Comparison of 89C52 with 89C51 21

3.3 89C52 pin functions 25

3.4 Port 1 alternate functions 26

3.5 Port 3 pin alternate functions 27

3.6 Timer 2 operating modes 30

3.7 Interrupt Sources 31

3.8 Interrupt Enable (IE) Register 32

4.1 Control words 47

4.2 Results 48

4.3 Timing states in the system 49


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1. INTRODUCTION

1.1 INTRODUCTION

With increasing penetration of technology in day to day life, the number of

electronic appliances, general to the most households, is increasing. Humans stride to

achieve automation and desire to reduce efforts made to control these appliances led to

various ways of controlling a large chunk of appliances with remote controls and remote

control methods. Television sets were first to be controlled with a remote control, that

made control of various functions such as channel selection, tuning and many more

functions a lot more fast and convenient. Since then, remote control has expanded its

spectrum by finding ways to ACs, CD/DVD players, microwave ovens, refrigerators, fans

and many more home appliances. These remote control methods generally make use of

infrared sensors and LEDs for communication between control unit and remote controller.

More complex remote controllers that can control more than one appliance are in use too.

Such remote controllers are frequently termed as Universal remote controller or simply

Universal remotes.

With the advent of home automation systems, switching control of some or all of

commonly used appliances, such as light bulbs, fans, water pump, ACs and geyser is also

explored. Such systems are capable of turning any appliance ON or OFF a particular

appliance by controlling the power supplied to it from supply board. The control is

actuated by sending control words with identification of particular appliances.

The control signals can be sent by infrared remote controls or by other methods

of signalling such as telephone call or through internet access. These systems can be

designed to control more functions of each appliance than just controlling its power

supply such as temperature of AC or speed of fan can be directly controlled by user.

These control parameters are sent with control words. But these remote controllers areoperational from within a limited radius of typically 10m. Also, it is not fully flexible,

that is, once the system is programmed for a particular need of home, it cant be modified

later.

Our attempt to solve the above discussed problem is by using noble features of

GSM cellular system for transporting control words to the control unit. This system

exploits Short Messaging Service (SMS) feature of GSM, which is very simple to use and

economic. GSM is ubiquitous and there are millions of mobile phone owners in India

hence the system is more likely to see real life implementations in masses in near future.


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1.2 NECESSITY

Necessity of GSM based remote appliance control system stems from the fact

that currently available methods of providing such services are too good to see any real

life implementation.

Internet based home automation system proves to be too much costly by

considering the cost of broadband connection and the efficiency related with it. So called

universal home remote controllers are sometimes too complex to configure and use. Also,

they require a line-of-sight between infrared source and sensors. This limits its range

between controller and appliance.

While this system solves above mentioned problems, it also offers widespread

operation range, practically wherever the GSM network has its reach. It is also very

economic considering the costs of SMS services and GSM connection charges.

1.3 OBJECTIVES

A task or project without a precise and well-defined objective has a least chance

of success. It is of very importance that objectives of the project be outlined well in

advance before considering solution to the problem.

The objective of this project can be listed as follows:

To study and implement the GSM techniques;

To study the embedded systems;

To study and implement microcontroller based systems;

To study the assembly program development;

To study the circuit design methods;

To prepare a comprehensive project report.

A modest effort has been made to complete the project according to the before

mentioned objectives. However, there may be some gray areas due to unintentional errors

on part of us.

1.4 THEME

The basic theme of the project is to develop a simple remote appliance control

system that fulfills the above objectives in cost-effective manner. The idea to use GSM in

the remote appliance control method is originated by the combined objective of studying

both of the fields of electronicssystem software development and hardware designing.

Home automation products represent an important class of embedded systems

that finds direct public uses. Home automation systems have made life easier for us,


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thanks to the microprocessors and microcontrollers which are widely used in embedded

system products. An embedded product uses a microprocessor or microcontroller to do

one and only one task.

Our project is an embedded system application wherein there is an extensive

interfacing of various relays and GSM module, which is an important part of the system.

Usage of relays, relay drivers, voltage converter ICs and serial communication devices

provide knowledge of interfacing these components. Basic wire wrapping knowledge

together with familiarity of resistors, capacitors and other basic circuit is also gained.

1.5 ORGANIZATION

The projects organization is based on the extensive interfacing of the GSM

modem and relay drivers with the 8051 based AT89C52 microcontroller. The specifically

selected version of microcontroller IC provides ample amount of ROM for program

memory and RAM for basic decoding of control messages. The microcontroller

communicates with GSM modem through serial communication by DB-9 connector with

the aid of RS-232 voltage converter. The strong driving currents for relays are provided

by ULN2803 relay driver IC. There are four relays; each being of solid state 1- relays.

The necessary DC voltages of 5V and 12V are derived from 230V AC mains supply by

bridge rectifier and fixed voltage regulator IC 7805. The organization in its simplest form

can be modeled as below.

Fig. 1.1 Basic project organization

89C52

Relay

Relay

Relay

Relay

Level

Converter

SMS

Relay

Driver


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2. LITERATURE SURVEY

Aim of this report is to choose the appropriate technologies and methods when

implementing a GSM based Home Automation System. To do this we will look at current

Home Automation implementations and the technologies that are currently available for

creating wireless remote switching systems. We should also look at other technologies

that may be appropriate for our project that has potential to improve the existing available

systems.

2.1 HOME AUTOMATION

Home Automation is a concept that has been developing reasonably slowly when

compared with the other technology such as televisions and computers. Whereas other

technologies such as high-definition televisions have developed and become much

cheaper, home automation is still generally quite an expensive and exclusive concept

for most people. We have tried here to look into what Home Automation is and what

current technologies exist. We shall look at how technologies were implemented in early

years and its situation in present era and the groups of people that will use the

technologies. We will look at the use of automation as a disability aid as well as it just

being a luxury within a home.

Home Automation (also referred to as Domotics) is the use of one or morecomputers to control basic home functions and features automatically and sometimes

remotely, an automated home is sometimes called a smart home. Home Automation

can be used for a wide variety of purposes; from turning lights on and off to

programming appliances within a home and the programming of timers for these

various devices. Home Automation is often used as a luxury convenience system

within a home and often it is expensive to have installed due to their relative

exclusivity in the current market. As Home Media devices become cheaper, Home

Automation is a technology that more people will be looking into to install in their house.

Home Automation (HA) is quite a broad area and therefore has a variety

of uses. Some areas are very important and can greatly improve the quality of life for

individuals, whilst other aspects of home automation are used for convenience rather than

an essential item. Starting off with the more essential aspect of home automation are

security aspects. Cameras and sensors can be connected to a home automation system.

These can be used to monitor and record activity around a building/house and can

make remote monitoring much easier. This can then make the technology of burglar


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alarms much more complex as they not only recognize movement with sensors but they

can also store and relay video images for the owner to then show the police if necessary.

Another use for home automation is with the elderly and people with impaired

physical mobility. Tasks that are simple for some people are much harder if you are

less mobile can be made much easier using an automated system.

Automated systems can be linked to motors and switches to perform tasks

controlled on a simple control panel. For example the opening and closing of curtains

in a room could be controlled by a remote control. The most dominant uses of home

automation are with home lighting, multimedia and smart home appliance control. This

tends to be the more exclusive market and often quite expensive.

Home Automation will only be adopted if it is at least as easy to use as the

original task in which it is replicating. For example if switching on a light via a home

automation system is more complicated than pressing a button on a wall then there is

arguably no advantage to having the device automated and it might just promote

user aggravation.

Home automation software in Australia is being used to shut down lighting and

devices in homes from their computers and mobile phones. A pilot study from the

company who produced the software showed that an office building was able to cut its

energy consumption by 25 percent. With the constant strive to create a greener planet;

Home automation could certainly help us in doing so.

2.1.1 Current Home Automation Systems

In the past many distributed audio systems within a house have consisted with a

large number of wired remote controls around a house which controls a central CD player

or Radio. The problem with these systems is that there is one audio source for many

rooms and each room cannot listen to a different CD concurrently. For this reason many

of the more modern systems are computer based systems. Most of the HA solutions

that are currently on sale use specialist hardware both to store the media and to

distribute it. An example is the Sonos Wireless Music Centre. The Sonos system uses

your current home computer, Sonos ZonePlayers in each of the rooms you require music

which then have speakers attached and a graphical remote control for each device.


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Fig 2.1 Sonos Wireless Music Centre Components

This system is designed so that it takes only basic computer skills to set up and

therefore saves the user money in not having to pay for a professional installation of

the product. It uses wireless technology for the ZonePlayers, Controllers and the

Computer to communicate and therefore doesnt require the inconvenience of installation

of network cabling to the building. The drawbacks with the Sonos system is that it only

covers music streaming within a home and does not control lighting and other

appliances. The other disadvantage is the system costs too much money for the smallest

room package and that doesnt include the cost of the computer that acts as a server if you

dont already have one. Another similar solution to the Sonos system is the

Cambridge Audio incognito system. This uses more dedicated hardware and has

more wired components compared to the Sonos system. More of the componentsare integrated into walls which makes a cleaner finish but are harder to setup and

move to a different room or house. The Cambridge Audio has optional modules to

allow video to be streamed as well as music. Neither of these system offer remote web

access to the system and they cannot control lighting or other appliances. The next few

products I will look at offer increases functionality beyond the scope of music and video.

One such company is Cyber Homes in UK. They offer tailored HA solutions

for individuals and families. They consult with the client and discover their needs then

come up with a selection of proposed solution and prices. They offer automation is Multi-

room Audio and Visual, Automated Lighting, CCTV and Security, Heating and Air-

conditioning and Occupancy Simulation. Occupancy Simulation is achieved by using the

other methods of HA they offer to achieve a realistic simulation that a house is being

lived in, aiming to achieve a house that appears to be occupied, and therefore less of a

target to burglary.

The advantages with companies such as Cyber Homes, is that they can offer

solution that are tailored to user need rather than having to adjust user home to work with


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the technology. The problem is that using tailored solution gains considerable extra cost.

A large proportion of this is paying for the design consultancy for designing your

system and also the installation costs that user will incur. Although the bespoke systems

are an expensive option, there is very little input required from the client apart from their

wishes on what they want the system to do, not how they are going to do it. This is why

very little technological experience is required for this option.

At the other end of the spectrum, there is DIY (Do-it-yourself) Home

Automation. This option is quite different to the tailored systems that companies such as

Cyber Homes have to offer. These can still offer a vast range of control within the

home, the difference being that this method is often very limited by a fixed

amount of available funds to equip the home. It is also necessary to be

technologically minded as the research into components needed and their

installation and maintenance all has to be carried out by the home owner

themselves. Websites such as DIY Home Automation offer consumer advice to people

trying to set up a system themselves. Sites like these are generally written to give friendly

advice, rather than a business, so may not necessarily contain the most up to date

information, or even the best practices in which to design a system.

The authors of the sites are usually enthusiasts rather than experts in the field.

This is why it is necessary for the home owner to have a fair amount of technical

knowledge or be technically minded, to help them siphon out the best information to

allow them to create a system that meets their needs.

The type of HA that is usually referred to in DIY HA is usually

controlled by a computer (usually an existing computer within the home) and signals

are usually sent through both wired or wireless Local Area Networks (LANs).

2.1.2 Problems With The Current Systems

The systems discussed above in the Current Home Automation Systems

section all have their own advantages and disadvantages, but we mainly concentrated

on their disadvantages. The purpose of this section is to outline some of the major

downfalls to the systems and mark out key points that make a system efficient and useful

and summarize these so as we can best address these issues when we come to develop our

own Home Automation System.

The first issue to look at is the ease of installation. Systems like the Sonos Media

system are relatively straight forward to install. They dont require much (if any)

additional wiring to be put in the house and this therefore limits disruption to the home


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with installation. It also means that the system is not tied down to having to stay in the

rooms in which it was initially installed as the components are relatively easy to relocate.

Other systems such as the tailored systems on offer by companies such as Cyber Homes

hardwire components and require cabling routed throughout a house. Often control panels

are sunken into the walls to give a nice sleek finish.

This does however limit the ease of relocating components significantly. DIY

Home Automation usually consists of message receiver modules.

The second clear disadvantages to some of the systems are cost. If a product is to

become successful it needs to be financial accessible to the mass market. Tailored

HA systems are not an option for a lot of people, therefore affordable plug and

play and easily configurable solutions need developing, even if they do have slightly

less functionality than the tailored systems. According to Kirchhoff and Linz they say that

forHA to be successful home automation cannot require technicians come to the users

home to integrate any kind of devices to home networks.

The problem with current HA systems is that the HA standards are extremely

fragmented. The problem with this is there is no universal standard, and lots of protocols

and devices are proprietary and this makes it harder for new systems to be developed as

quickly as one would like it to be. When we design our system we will either have to

create something that encompasses all existing technologies or we need to create

a system that can be integrated with existing technologies and standards.

Being a project one of its kind, one more topic that needs to be discussed in this

project is the evolution of the embedded system. An embedded system is a computer

system designed for specific control functions within a larger system, often with real-time

computing constraints. It is embedded as part of a complete device often including

hardware and mechanical parts. By contrast, a general-purpose computer, such as a

personal computer (PC), is designed to be flexible and to meet a wide range of end-user

needs. Embedded systems control many devices in common use today.

Embedded systems contain processing cores that are typically either

microcontrollers or digital signal processors (DSP). The key characteristic, however, is

being dedicated to handle a particular task. Since the embedded system is dedicated to

specific tasks, design engineers can optimize it to reduce the size and cost of the product

and increase the reliability and performance. Some embedded systems are mass-

produced, benefiting from economies of scale.


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Physically, embedded systems range from portable devices such as digital

watches and MP3 players, to large stationary installations like traffic lights, factory

controllers and the systems controlling nuclear power plants. Complexity varies from

low, with a single microcontroller chip, to very high with multiple units, peripherals and

networks mounted inside a large chassis or enclosure.

An embedded system is a computer system designed for specific control

functions within a larger system, often with real-time computing constraints. It is

embedded as part of a complete device often including hardware and mechanical parts.

By contrast, a general-purpose computer, such as a personal computer (PC), is designed

to be flexible and to meet a wide range of end-user needs. Embedded systems control

many devices in common use today.

Embedded systems span all aspects of modern life and there are many examples

of their use.

Telecommunications systems employ numerous embedded systems from

telephone switches for the network to mobile phones at the end-user. Computer

networking uses dedicated routers and network bridges to route data.

Consumer electronics include personal digital assistants (PDAs), MP3 players,

mobile phones, videogame consoles, digital cameras, DVD players, GPS receivers, and

printers. Many household appliances, such as microwave ovens, washing machines and

dishwashers, are including embedded systems to provide flexibility, efficiency and

features. Advanced HVAC systems use networked thermostats to more accurately and

efficiently control temperature that can change by time of day and season. Home

automation uses wired- and wireless-networking that can be used to control lights,

climate, security, audio/visual, surveillance, etc., all of which use embedded devices for

sensing and controlling.

Transportation systems from flight to automobiles increasingly use embedded

systems. New airplanes contain advanced avionics such as inertial guidance systems and

GPS receivers that also have considerable safety requirements. Various electric motors

brushless DC motors, induction motors and DC motors are using electric/electronic

motor controllers. Automobiles, electric vehicles, and hybrid vehicles are increasingly

using embedded systems to maximize efficiency and reduce pollution. Other automotive

safety systems include anti-lock braking system (ABS), Electronic Stability Control

(ESC/ESP), traction control (TCS) and automatic four-wheel drive.


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Medical equipment is continuing to advance with more embedded systems for

vital signs monitoring, electronic stethoscopes for amplifying sounds, and various

medical imaging (PET, SPECT, CT, MRI) for non-invasive internal inspections.

Embedded systems are especially suited for use in transportation, fire safety,

safety and security, medical applications and life critical systems as these systems can be

isolated from hacking and thus be more reliable. For fire safety, the systems can be

designed to have greater ability to handle higher temperatures and continue to operate. In

dealing with security, the embedded systems can be self-sufficient and be able to deal

with cut electrical and communication systems.

In addition to commonly described embedded systems based on small

computers, a new class of miniature wireless devices called motes is quickly gaining

popularity as the field of wireless sensor networking rises. Wireless sensor networking,

WSN, makes use of miniaturization made possible by advanced IC design to couple full

wireless subsystems to sophisticated sensors, enabling people and companies to measure

a myriad of things in the physical world and act on this information through IT

monitoring and control systems. These motes are completely self contained, and will

typically run off a battery source for many years before the batteries need to be changed

or charged.

2.2 MOBILE COMMUNICATION

Mobile telecommunication technologies have developed in successive

generations. The first generation (1G) appeared in the 1950s. The second generation

(2G) or GSM technology is used massively, but challenged globally by the next (third)

generation (3G) technologies. This sequence of generations is characterised by increasing

capacity (higher transmission speeds) and richer content of the message. Further

penetration of 3G depends critically on the integration of telecommunication services and

multimedia services, which turned out to be more complicated than most experts

predicted. Four obstacles on this expansion path can be distinguished: Firstly, after the

weakened financial position of mobile network operators, it became more difficult to

finance and construct the networks because the capital markets questioned the

profitability of these investments. This resulted in regulatory measures to facilitate the

financial viability of UMTS networks by allowing operators to share networks and

delay implementation. Secondly, many of the futuristic product and service designs

(for example computerised homes and mobile telephones functioning as credit cards or

parking tickets) of the new economy turned out to be more difficult and costly to develop


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and to market. Thirdly, many operators were drawn into costly license auctions

and mergers that slowed down and scaled down their investments in the latest

technology and new services. Fourthly, the operators underestimated the difficulties to

develop new business models for voice and data in 3G compared with mainly voice in

2G. Despite these obstacles the markets for mobile data and mobile Internet has

demonstrated a high and sustainable growth rate during last decade in India. Most

noteworthy are the immense and surprising successes of private SMS or short messaging

services, EMS or enhanced messaging services and the rapid growth of MMS or

multimedia messaging services. Less spectacular have been the popularity of sports, news

and weather information on the go. These markets leave ample space for a myriad of

multimedia applications. So far, technology itself seems not to be an obstacle.

Mobile phones send and receive radio signals with any number of cell site base

stations fitted with microwave antennas. These sites are usually mounted on a tower, pole

or building, located throughout populated areas, then connected to a cabled

communication network and switching system. The phones have a low-power transceiver

that transmits voice and data to the nearest cell sites, normally not more than 8 to 13 km

(approximately 5 to 8 miles) away.

When the mobile phone or data device is turned on, it registers with the mobile

telephone exchange, or switch, with its unique identifiers, and can then be alerted by the

mobile switch when there is an incoming telephone call. The handset constantly listens

for the strongest signal being received from the surrounding base stations, and is able to

switch seamlessly between sites. As the user moves around the network, the "handoffs"

are performed to allow the device to switch sites without interrupting the call.

Cell sites have relatively low-power (often only one or two watts) radio

transmitters which broadcast their presence and relay communications between the

mobile handsets and the switch. The switch in turn connects the call to another subscriber

of the same wireless service provider or to the public telephone network, which includes

the networks of other wireless carriers. Many of these sites are camouflaged to blend with

existing environments, particularly in scenic areas.

The dialogue between the handset and the cell site is a stream of digital data that

includes digitized audio (except for the first generation analog networks). The technology

that achieves this depends on the system which the mobile phone operator has adopted.

The technologies are grouped by generation. The first-generation systems started in 1979


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with Japan, are all analog and include AMPS and NMT. Second-generation systems,

started in 1991 in Finland, are all digital and include GSM, CDMA and TDMA.

The nature of cellular technology renders many phones vulnerable to 'cloning':

anytime a cell phone moves out of coverage (for example, in a road tunnel), when the

signal is re-established, the phone sends out a 're-connect' signal to the nearest cell-tower,

identifying itself and signaling that it is again ready to transmit. With the proper

equipment, it's possible to intercept the re-connect signal and encode the data it contains

into a 'blank' phone -- in all respects, the 'blank' is then an exact duplicate of the real

phone and any calls made on the 'clone' will be charged to the original account.

Third-generation (3G) networks, which are still being deployed, began in 2001.

They are all digital, and offer high-speed data access in addition to voice services and

include W-CDMA (known also as UMTS), and CDMA2000 EV-DO. China will launch a

third generation technology on the TD-SCDMA standard. Operators use a mix of

predesignated frequency bands determined by the network requirements and local

regulations.

In an effort to limit the potential harm from having a transmitter close to the

user's body, the first fixed/mobile cellular phones that had a separate transmitter, vehicle-

mounted antenna, and handset (known as car phones and bag phones) were limited to a

maximum 3 watts Effective Radiated Power. Modern handheld cell phones which must

have the transmission antenna held inches from the user's skull are limited to a maximum

transmission power of 0.6 watts ERP. Regardless of the potential biological effects, the

reduced transmission range of modern handheld phones limits their usefulness in rural

locations as compared to car/bag phones, and handhelds require that cell towers be spaced

much closer together to compensate for their lack of transmission power.

Some handhelds include an optional auxiliary antenna port on the back of the

phone, which allows it to be connected to a large external antenna and a 3 watt cellular

booster. Alternately in fringe-reception areas, a cellular repeater may be used, which uses

a long distance high-gain dish antenna or yagi antenna to communicate with a cell tower

far outside of normal range, and a repeater to rebroadcast on a small short-range local

antenna that allows any cell phone within a few meters to function properly.

2.3 GSM ARCHITECTURE

Global System for Mobile Communications, or GSM (originally from Groupe

Spcial Mobile), is the world's most popular standard for mobile telephone systems. The

GSM Association estimates that 80% of the global mobile market uses the standard.


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GSM is used by over 1.5 billion people across more than 212 countries and territories.

This ubiquity means that subscribers can use their phones throughout the world, enabled

by international roaming arrangements between mobile network operators. GSM differs

from its predecessor technologies in that both signaling and speech channels are digital,

and thus GSM is considered a second generation (2G) mobile phone system. This also

facilitates the wide-spread implementation of data communication applications into the

system.

The GSM standard has been an advantage to both consumers, who may benefit

from the ability to roam and switch carriers without replacing phones, and also to network

operators, who can choose equipment from many GSM equipment vendors. GSM also

pioneered low-cost implementation of the short message service (SMS), also called text

messaging, which has since been supported on other mobile phone standards as well. The

standard includes a worldwide emergency telephone number feature.

Newer versions of the standard were backward-compatible with the original

GSM system. For example, Release '97 of the standard added packet data capabilities by

means of General Packet Radio Service (GPRS). Release '99 introduced higher speed data

transmission using Enhanced Data Rates for GSM Evolution (EDGE).

2.3.1History

In 1982, the European Conference of Postal and Telecommunications

Administrations (CEPT) created the Groupe Spcial Mobile (GSM) to develop a standard

for a mobile telephone system that could be used across Europe. In 1987, a memorandum

of understanding was signed by 13 countries to develop a common cellular telephone

system across Europe. In 1989, GSM responsibility was transferred to the European

Telecommunications Standards Institute (ETSI) and phase-I of the GSM specifications

were published in 1990. The first GSM network was launched in 1991 by Radiolinja in

Finland with joint technical infrastructure maintenance from Ericsson. By the end of

1993, over a million subscribers were using GSM phone networks being operated by 70

carriers across 48 countries.

2.3.2 Technical details

GSM is a cellular network, which means that mobile phones connect to it by

searching for cells in the immediate vicinity. There are five different cell sizes in a GSM

networkmacro, micro, pico, femto and umbrella cells. The coverage area of each cell

varies according to the implementation environment. Macro cells can be regarded as cells

where the base station antenna is installed on a mast or a building above average roof top


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level. Micro cells are cells whose antenna height is under average roof top level; they are

typically used in urban areas. Picocells are small cells whose coverage diameter is a few

dozen metres; they are mainly used indoors. Femtocells are cells designed for use in

residential or small business environments and connect to the service providers network

via a broadband internet connection. Umbrella cells are used to cover shadowed regions

of smaller cells and fill in gaps in coverage between those cells.

Cell horizontal radius varies depending on antenna height, antenna gain and

propagation conditions from a couple of hundred meters to several tens of kilometers. The

longest distance the GSM specification supports in practical use is 35 kilometers. There

are also several implementations of the concept of an extended cell, where the cell radius

could be double or even more, depending on the antenna system, the type of terrain and

the timing advance.

Fig 2.2 GSM Architecture

Indoor coverage is also supported by GSM and may be achieved by using an

indoor picocell base station, or an indoor repeater with distributed indoor antennas fed

through power splitters, to deliver the radio signals from an antenna outdoors to the

separate indoor distributed antenna system. These are typically deployed when a lot of

call capacity is needed indoors; for example, in shopping centers or airports. However,

this is not a prerequisite, since indoor coverage is also provided by in-building penetration

of the radio signals from any nearby cell.


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The modulation used in GSM is Gaussian minimum-shift keying (GMSK), a

kind of continuous-phase frequency shift keying. In GMSK, the signal to be modulated

onto the carrier is first smoothed with a Gaussian low-pass filter prior to being fed to a

frequency modulator, which greatly reduces the interference to neighboring channels

(adjacent-channel interference).

2.3.3 GSM carrier frequencies

GSM networks operate in a number of different carrier frequency ranges

(separated into GSM frequency ranges for 2G and UMTS frequency bands for 3G), with

most 2G GSM networks operating in the 900 MHz or 1800 MHz bands. Where these

bands were already allocated, the 850 MHz and 1900 MHz bands were used instead (for

example in Canada and the United States). In rare cases the 400 and 450 MHz frequency

bands are assigned in some countries because they were previously used for first-

generation systems.

Regardless of the frequency selected by an operator, it is divided into timeslots

for individual phones to use. This allows eight full-rate or sixteen half-rate speech

channels per radio frequency. These eight radio timeslots (or eight burst periods) are

grouped into a TDMA frame. Half rate channels use alternate frames in the same timeslot.

The channel data rate for all channels is 270.83 kbit/s and the frame duration is 4.615 ms.

The transmission power in the handset is limited to a maximum of 2 watts in

GSM850/900 and 1 watt in GSM1800/1900.

2.3.4 Network structure

The network is structured into a number of discrete sections:

The Base Station Subsystem (the base stations and their controllers).

The Network and Switching Subsystem (the part of the network most similar

to a fixed network). This is sometimes also just called the core network.

The GPRS Core Network (the optional part which allows packet based

Internet connections).

The Operations support system (OSS) for maintenance of the network.

2.3.5 Subscriber Identity Module (SIM)

One of the key features of GSM is the Subscriber Identity Module, commonly

known as a SIM card. The SIM is a detachable smart card containing the user's

subscription information and phone book. This allows the user to retain his or her

information after switching handsets. Alternatively, the user can also change operators


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while retaining the handset simply by changing the SIM. Some operators will block this

by allowing the phone to use only a single SIM, or only a SIM issued by them; this

practice is known as SIM locking.

Fig. 2.3 SIM card

2.3.6 GSM service security

GSM was designed with a moderate level of service security. The system was

designed to authenticate the subscriber using a pre-shared key and challenge-response.

Communications between the subscriber and the base station can be encrypted. The

development of UMTS introduces an optional Universal Subscriber Identity Module

(USIM), that uses a longer authentication key to give greater security, as well as mutually

authenticating the network and the user - whereas GSM only authenticates the user to the

network (and not vice versa). The security model therefore offers confidentiality and

authentication, but limited authorization capabilities, and no non-repudiation.

GSM uses several cryptographic algorithms for security. The A5/1 and A5/2

stream ciphers are used for ensuring over-the-air voice privacy. A5/1 was developed first

and is a stronger algorithm used within Europe and the United States; A5/2 is weaker and

used in other countries. Serious weaknesses have been found in both algorithms: it is

possible to break A5/2 in real-time with a ciphertext-only attack, and in February 2008,

Pico Computing, Inc revealed its ability and plans to commercialize FPGAs that allow

A5/1 to be broken with a rainbow table attack. The system supports multiple algorithms

so operators may replace that cipher with a stronger one.

On 28 December 2009 German computer engineer Karsten Nohl announced that

he had cracked the A5/1 cipher. According to Nohl, he developed a number of rainbow

tables (static values which reduce the time needed to carry out an attack) and have found

new sources for known plaintext attacks. He also said that it is possible to build "a full


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GSM interceptor from open source components" but that they had not done so because of

legal concerns.

Although security issues remain for GSM newer standards and algorithms may

address this. New attacks are growing in the wild which take advantage of poor security

implementations, architecture and development for smart phone applications. Some

wiretapping and eavesdropping techniques hijack the audio input and output providing an

opportunity for a 3rd party to listen in to the conversation. Although this threat is

mitigated by the fact the attack has to come in the form of a Trojan, malware or a virus

and might be detected by security software.

2.3.7 GSMs strength

GSM is the first to apply the TDMA scheme developed for mobile radio

systems. It has several distinguishing features:

1. Roaming in European countries

2. Connection to ISDN through RA box

3. Use of SIM cards

4. Control of transmission power

5. Frequency hopping

6. Discontinuous transmission

7. Mobile-assisted handover


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3. SYSTEM DEVELOPMENT

System development can be divided into sections as below:

(1)Design of power section

(2)Design of relay circuit

(3)Design of main controller board

(4)Circuit diagrams

(5)PCB layouts

(6)System software development.

3.1 DESIGN OF POWER SECTION

The project requires DC voltage supply of +5V and +12V and a common ground

which is derived from AC supply of 230V mains.

1) Selection of transformer

We use bridge rectifier configuration because it has half PIV and higher

rectification efficiency than other configurations.

We need to select a transformer with a center-tapping on secondary.

We need Vdc = 12V and 5V.

So we select a transformer with secondary of 12-0-12.

2) Selection of diode

Possible PIV across each diode is Vdc = 12V.

So we have to select four diodes with PIV more than 12V.

We select 1N4007 silicon diodes as D1 to D4 considering worst case scenario.

3) Selection of regulator IC

To get 5V regulated supply out of 12V, we use fixed voltage monolithic regulator

IC LM7805.

It utilizes common ground for input and output.

A capacitor C3 of 0.1uF is connected at output of LM7805 to improve the

transient response.

4) Selection of filter capacitor

To filter the ripple out, we use an electrolyte capacitor of value C1 = 1000uF.

5) Selection of indication circuit components

To indicate power status of circuit, we have simply formed an LED indicator

circuit.R1 = (Vdc - Vdrop) / Imax


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= (5-0.7)/10mA = 430

We select a standard resistance value of 470 .

An LED with drop 0.7V in series with R1 is connected across Vdc and GND.

Lit LED indicates power ON condition.6) Selection of heat sink

IC LM7805 generates a large amount of heat, to dissipate that heat we have

mounted heat sink.

Fig. 3.1 Circuit diagram of power supply section

3.2 DESIGN OF RELAY CIRCUIT

1) Selection of relay driver

Select ULN2803APG from TOSHIBA as it serves our purpose well here.

The ULN2803APG Series are highvoltage, highcurrent darlington drivers

comprised of eight NPN darlington pairs. All units feature integral clamp diodes

for switching inductive loads.

Applications include relay, hammer, lamp and display (LED) drivers.

Fig. 3.2 ULN 2803 pin configuration


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2) Selection of relays

Relays are very important part of this project. It acts as a switch to turn a home

appliance on or off. Usually the home appliances operate on AC mains which is

230V at 50Hz in India. So we have to choose relays with minimum switching

voltage capacity of 240V AC and minimum switching current of 5A.

We select HK make JQC-3FC/T73 model PCB mounted Sugar Cube relay. It has

maximum voltage switching capacity of 250V AC and maximum current

switching capacity of 7A.

About relay:

Fig. 3.3 HKE make JQC-3FC/T73 12VDC

Characteristics of relay:

Max. Switching current 7A, 10A

Max. switching voltage 28V DC/ 250V AC

Dielectric strength Vrms

Between open contacts

Between coil and contacts

Between contacts form

750VAC

1000VAC

1000VACAmbient temperature -40 - +85oC

Operation/Release time 10/8 ms

Contact Capacity 10A 240VAC, 6.3A 28VDC

Table 3.1 Relay characteristics

3) Selection of indication circuit components

To indicate the status of the relay, an LED is connected to relay input.

It acts similar to the indication circuit in the power supply section.

R1 = (V - Vdrop) / Imax

Bigger dot in this Small dot in

this corner upper corner

Rectangular cut in

middle top side of this

face


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= (5 - 0.7)/10mA = 430

We select a standard resistance value of 470 .

An LED with drop 0.7V in series with R1 is connected across Vdc and GND.

Lit LED indicates power ON condition.3.3 DESIGN OF MAIN CONTROLLER BOARD

1) Selection of microcontroller

Selection criteria:

1.The first and foremost criterion for selecting a microcontroller is that it must

meet the task at hand efficiently and cost effectively. In analyzing the need of a

microcontroller based project we must see whether an 8 bit, 16 bit or 32 bit

microcontroller can best handle the computing need of the task most efficiently.

Among other consideration in this category are speed, power consumption,

amount of on chip RAM and ROM, the number of I/O pin, and cost per unit.

2.Second is how easy is to develop product around it. Key considerations are the

availability of an assembler, debugger, emulator, technical support.

3.Its readily availability in needed quantity, both now and in future.

Though very slight difference between the features of AT89C51 and AT89C52,

they are very similar in their pin configurations and operations. The differences between

AT89C51 and AT89C52 have been tabulated below.

Microcontroller AT89C52 AT89C51

RAM 256 Bytes 128 Bytes

Flash 8 KB 4 KB

Number of Timers/Counters 3 (16-bit each) 2 (16-bit each)

Number of Interrupt Sources 8 6

Table 3.2 Comparison of 89C52 with 89C51

Taking all the above considerations we have chosen ATMEL 89C52

microcontroller because it meets selection most appropriately.

3.3.1 Brief History of Microcontrollers:

In 1981, Intel Corporation introduced an 8-bit microcontroller called the 8051,

this microcontroller had 128 bytes of RAM, 4 bytes of on chip ROM, two timers, one

serial port, and four ports (each 8-bit wide) all on a single chip. At this time it was

referred to as a system on chip. The 8052 is an 8-bit processor, meaning that the CPU

can work on only 8 bit at a time. Data larger than 8 bit have to be broken up into 8 bit


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pieces to be processed by the CPU. The 8051 now has a total of four I/O ports, each 8 bit

wide.

The 8051 became widely popular after Intel allowed other manufacturers to

make and market any flavor of the 8051 with the condition that they remain code

compatible with 8051. This had lead to many versions of 8051 with a different speed and

amount of on chip ROM marketed by more than half a dozen manufacturers. There are

two other members of the 8051 family, they are 8051 and 8031. 8052 is a version of 8051

with higher RAM and ROM.

Features of microcontroller Atmel 89S52:

Compatible with MCS-51 Products

8K Bytes of In-System Reprogrammable Flash Memory

Endurance: 1,000 Write/Erase Cycles

Fully Static Operation: 0 Hz to 24 MHz

Three-level Program Memory Lock

256 x 8-bit Internal RAM

32 Programmable I/O Lines

Three 16-bit Timer/Counters

Eight Interrupt Sources

Programmable Serial Channel

3.3.2 Description

The AT89S52 is a low-power, high-performance CMOS 8-bit microcomputer

with 8K bytes of Flash programmable and erasable read only memory (PEROM). The

device is manufactured using Atmels high-density nonvolatile memory technology and is

compatible with the industry-standard 80C51 and 80C52 instruction set and pinout.

Fig. 3.4 Atmel AT89C52


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The on-chip Flash allows the program memory to be reprogrammed in-system or

by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU

with in-system programmable Flash on a monolithic chip, the Atmel AT89S52 is a

powerful microcontroller, which provides a highly flexible and cost-effective solution to

many, embedded control applications.

The AT89S52 provides the following standard features: 8K bytes of Flash, 256

bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit

timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-

chip oscillator, and clock circuitry. In addition, the AT89S52 is designed with static logic

for operation down to zero frequency and supports two software selectable power saving

modes.

The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial

port, and interrupt system to continue functioning. The Power-down mode saves the

RAM con-tents but freezes the oscillator, disabling all other chip functions until the next

interrupt occurs.

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller

with 8K bytes of in-system programmable Flash memory. The device is manufactured

using Atmels high-density nonvolatile memory technology and is compatible with the

industry-standard 80C51 instruction set and pinout.


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Fig. 3.5 89S52 Block Diagram


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Pin No Function Name

1 External count input to Timer/Counter 2, clockout T2 P1.0

2Timer/Counter 2 capture/reload trigger and

direction controlT2 EX P1.1

3

8 bit input/output port (P1) pins

P1.2

4 P1.3

5 P1.4

6 P1.5

7 P1.6

8 P1.7

9 Reset pin; Active high Reset

10Input (receiver) for serial

communicationRxD

8 bitinput/output

port (P3) pins

P3.0

11Output (transmitter) for serial

communicationTxD P3.1

12 External interrupt 1 Int0 P3.213 External interrupt 2 Int1 P3.3

14 Timer1 external input T0 P3.4

15 Timer2 external input T1 P3.5

16 Write to external data memory Write P3.6

17 Read from external data memory Read P3.7

18Quartz crystal oscillator (up to 24 MHz)

Crystal 2

19 Crystal 1

20 Ground (0V) Ground

21


/

High-order address bits when interfacing with external

memory

P2.0/ A8

22 P2.1/ A9

23 P2.2/ A10

24 P2.3/ A11

25 P2.4/ A12

26 P2.5/ A13

27 P2.6/ A14

28 P2.7/ A15

29 Program store enable; Read from external program memory PSEN

30Address Latch Enable ALE

Program pulse input during Flash programming Prog

31External Access Enable; Vcc for internal program executions EA

Programming enable voltage; 12V (Flash programming) Vpp

32


Low-order address bits when interfacing with external

memory

P0.7/ AD7

33 P0.6/ AD6

34 P0.5/ AD5

35 P0.4/ AD4

36 P0.3/ AD3

37 P0.2/ AD2

38 P0.1/ AD1

39 P0.0/ AD0

40 Supply voltage; 5V (up to 6.6V) Vcc

Table 3.3 89C52 pin functions


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3.3.3 Pin Description

(1)VCC

Supply voltage of 5V (or 12V for VPP) in programming mode.

(2)GND

This pin serves for ground connection of 0 volts.

(3)Port 0

Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin

can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as

high- impedance inputs. Port 0 can also be configured to be the multiplexed low-order

address/data bus during accesses to external program and data memory. In this mode, P0

has internal pullups.

Port 0 also receives the code bytes during Flash programming and outputs the

code bytes during program verification. External pullups are required during program

verification.

(4)Port 1

Port 1 is an 8-bit bi-directional I/O port with internal pullups. The Port 1 output

buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are

pulled high by the internal pullups and can be used as inputs. As inputs, Port 1 pins that

are externally being pulled low will source current (I IL) because of the internal pullups.

In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external

count input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively, as

shown in the following table.

Port 1 also receives the low-order address bytes during Flash programming and

verification.

Existing Alternate Function

P1.0 T2 Timer/counter 2 External Count input, clock out

P1.1 T2 EX Timer/counter 2 Trigger input

Table 3.4 Port 1 alternate functions

(5)Port 2




are externally being pulled low will source current (I IL) because of the internal pullups.


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Port 2 emits the high-order address byte during fetches from external program

memory and during accesses to external data memory that use 16-bit addresses (MOVX

@DPTR). In this application, Port 2 uses strong internal pullups when emitting 1s.

During access to external data memory that uses 8-bit addresses (MOVX @RI), Port 2

emits the contents of the P2 Special Function Register.

Port 2 also receives the high-order address bits and some control signals during

Flash programming and verification.

(6)Port 3




are externally being pulled low will source current (I IL) because of the pullups.

Port 3 also serves the functions of various special features of the AT89C52, as

shown in the following table. Port 3 also receives some control signals for Flash

programming and verification.

Port Pin Alternate Functions

P3.0 RXD (serial input port)

P3.1 TXD (serial output port)

P3.2 INT0 (external interrupt 0)

P3.3 INT1 (external interrupt 1)

P3.4 T0 (timer 0 external input)

P3.5 T1 (timer 1 external input)

P3.6 WR (external data memory write strobe)

P3.7 RD (external data memory read strobe)

Table 3.5 Port 3 pin alternate functions

(7)RST

Reset input. A high on this pin for two machine cycles while the oscillator is

running resets the device.

(8)ALE/PROG

Address Latch Enable is an output pulse for latching the low byte of the address

during accesses to external memory. This pin is also the program pulse input (PROG)

during Flash programming.


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In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator

frequency and may be used for external timing or clocking purposes. Note, however, that

one ALE pulse is skipped during each access to external data memory.

If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH.

With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise,

the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the

microcontroller is in external execution mode.

(9)PSEN

Program Store Enable is the read strobe to external program memory. When the

AT89C52 is executing code from external program memory, PSEN is activated twice

each machine cycle, except that two PSEN activations are skipped during each access to

external data memory.

(10)EA/VPP

External Access Enable. EA must be strapped to GND in order to enable the

device to fetch code from external program memory locations starting at 0000H up to

FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on

reset. EA should be strapped to VCC for internal program executions. This pin also

receives the 12-volt programming enable voltage (VPP) during Flash programming when

12-volt programming is selected.

(11)XTAL1

Input to the inverting oscillator amplifier and input to the internal clock

operating circuit.

(12)XTAL2

Output from the inverting oscillator amplifier. A crystal of frequency 4 to 24

MHz is connected between pins XTAL1 and XTAL2.

Special Function Registers (SFRs)

A map of the on-chip memory area called the Special Function Register (SFR)

space is shown in Table 1. Note that not all of the addresses are occupied, and unoccupied

addresses may not be implemented on the chip.Read accesses to these addresses will in

general return random data, and write accesses will have an indeterminate effect.

Timer 2 Registers Control and status bits are contained in registers T2CON

(shown in Table 2) and T2MOD for Timer 2. The register pair (RCAP2H, RCAP2L) are

the Capture/Reload registers for Timer 2 in 16-bit capture mode or 16-bit auto-reload

mode.


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Interrupt Registers The individual interrupt enable bits are in the IE register.

Two priorities can be set for each of the six interrupt sources in the IP register.

Data Memory

The AT89C52 implements 256 bytes of on-chip RAM. The upper 128 bytes

occupy a parallel address space to the Special Function Registers. That means the upper

128 bytes have the same addresses as the SFR space but are physically separate from SFR

space. When an instruction accesses an internal location above address 7FH, the address

mode used in the instruction specifies whether the CPU accesses the upper 128 bytes of

RAM or the SFR space. Instructions that use direct addressing access SFR space.

For example, the following direct addressing instruction accesses the SFR at

location 0A0H (which is P2).

MOV 0A0H, #data

Instructions that use indirect addressing access the upper 128 bytes of RAM. For

example, the following indirect addressing instruction, where R0 contains 0A0H,

accesses the data byte at address 0A0H, rather than P2 (whose address is 0A0H).

MOV @R0, #data

Note that stack operations are examples of indirect addressing, so the upper 128

bytes of data RAM are available as stack space.

Timer 0 and 1

Timer 0 and Timer 1 in the AT89C52 operate the same way as Timer 0 and

Timer 1 in the AT89C51.

Timer 2

Timer 2 is a 16-bit Timer/Counter that can operate as either a timer or an event

counter. The type of operation is selected by bit C/T2 in the SFR T2CON (shown in

Table 2).

Timer 2 has three operating modes: capture, auto-reload (up or down counting),

and baud rate generator. The modes are selected by bits in T2CON, as shown in Table

below. Timer 2 consists of two 8-bit registers, TH2 and TL2. In the Timer function, the

TL2 register is incremented every machine cycle. Since a machine cycle consists of 12

oscillator periods, the count rate is 1/12 of the oscillator frequency.


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RCLK+TCLK CP/RL2 TR2 MODE

0 0 1 16-bit auto reload

0 1 1 16-bit capture

1 X 1 Baud Rate generatorX X 0 (Off)

Table 3.6 Timer 2 operating modes

In the Counter function, the register is incremented in response to a 1-to-0

transition at its corresponding external input pin, T2. In this function, the external input is

sampled during S5P2 of every machine cycle. When the samples show a high in one cycle

and a low in the next cycle, the count is incremented. The new count value appears in the

register during S3P1 of the cycle following the one in which the transition was detected.

Since two machine cycles (24 oscillator periods) are required to recognize a 1-to-0

transition, the maximum count rate is 1/24 of the oscillator frequency. To ensure that a

given level is sampled at least once before it changes, the level should be held for at least

one full machine cycle.

Capture Mode

In the capture mode, two options are selected by bit EXEN2 in T2CON. If

EXEN2 = 0, Timer 2 is a 16-bit timer or counter which upon overflow sets bit TF2 in

T2CON. This bit can then be used to generate an interrupt. If EXEN2 = 1, Timer 2

performs the same operation, but a 1-to-0 transition at external input T2EX also causes

the current value in TH2 and TL2 to be captured into RCAP2H and RCAP2L,

respectively. In addition, the transition at T2EXcauses bit EXF2 in T2CON to be set. The

EXF2 bit, like TF2, can generate an interrupt. The capture mode is illustrated in Figure 1.

Auto-reload (Up or Down Counter)

Timer 2 can be programmed to count up or down when configured in its 16-bit

auto-reload mode. This feature is invoked by the DCEN (Down Counter Enable) bit

located in the SFR T2MOD. Upon reset, the DCEN bit is set to 0 so that timer 2 will

default to count up. When DCEN is set, Timer 2 can count up or down, depending on the

value of the T2EX pin.

UART

It is the Universal Asynchronous Receiver Transmitter. The UART in the

AT89C52 operates the same way as the UART in the AT89C51. It is used for serial

communication with other compatible devices.


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Interrupts

The AT89C52 has a total of six interrupt vectors: two external interrupts (INT0

and INT1), three timer interrupts (Timers 0, 1, and 2), and the serial port interrupt. These

interrupts are all shown in Figure 6.

Each of these interrupt sources can be individually enabled or disabled by setting

or clearing a bit in Special Function Register IE. IE also contains a global disable bit, EA,

which disables all interrupts at once.

Note that Table shows that bit position IE.6 is unimplemented. In the AT89C51,

bit position IE.5 is also unimplemented. User software should not write 1s to these bit

positions, since they may be used in future AT89 products.

Timer 2 interrupt is generated by the logical OR of bits TF2 and EXF2 in

register T2CON. Neither of these flags is cleared by hardware when the service routine is

vectored to. In fact, the service routine may have to determine whether it was TF2 or

EXF2 that generated the interrupt, and that bit will have to be cleared in software.

The Timer 0 and Timer 1 flags, TF0 and TF1, are set at S5P2 of the cycle in

which the timers overflow. The values are then polled by the circuitry in the next cycle.

However, the Timer 2 flag, TF2, is set at S2P2 and is polled in the same cycle in which

the timer overflows.

Symbol Position Function

EA IE.7

Disables all interrupts. If EA = 0, no interrupt is

acknowledged. If EA = 1, each interrupt source

is individually enabled or disabled by setting or

clearing its enable bit.

- IE.6 Reserved

ET2 IE.5 Timer 2 interrupt enable bit

ES IE.4 Serial Port interrupt enable bit.

ET1 IE.3 Timer 1 interrupt enable bit.

EX1 IE.2 External interrupt 1 enable bit.

ET0 IE.1 Timer 0 interrupt enable bit

EX0 IE.0 External interrupt 0 enable bit.

Table 3.7 Interrupt Sources


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(LSB) (MSB)

A T2 S T1 X1 T0 X0

Enable Bit = 1 enables the interrupt

Enable Bit = 0 disables the interrupt

Table 3.8 Interrupt Enable (IE) Register

2) Design of clock generation circuit

The 8052 has an on-chip oscillator but requires an external clock to run it. Most

often a quartz crystal oscillator is connected to inputs XTAL1 (pin 19) and XTAL2 (pin

18). The quartz crystal oscillator connected to XTAL1 and XTAL2 also needs two

capacitors of 30pF value. One side of each capacitor is connected to ground as shown in

figure below.

Fig. 3.6 Clock generation circuitry

3) Design of pull-up networks

Fig. 3.7 Pull-up network


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In the 8051 based systems where there is no exrernal memory connection, the

pins of port 0 must be connected externally to a 10K-ohm pullup resistor. This is due to

the fact that P0 is an open drain unlike P1, P2 and P3. With external pull-up resistors

connected to P0, it can be used as a simple I/O port, just like P1 and P2.

4) Design of reset circuit

Pin 9 is the reset pin. It is an input and is active high (normally low). Upon

applying a high pulse to this pin, the microcontroller will reset and terminate all activities.

This is often referred to as a power-on reset. Activating a power-on reset will cause all

values in the registers to be lost. It will set program counter to all 0s.

Following figure shows the way of connecting the RST pin to the power-on

circuitry. An 8.2K-ohm resistor and 10 uF capacitor forms the RST circuitry.

Fig. 3.8 Reset circuitry

5) Selection of line converter IC

The 8052 has two pins that are used specifically for transferring and receivingdata serially. These two pins are called as TxD and RxD and are part of the port 3 group

(P3.0 and P3.1). Pin 11 of the 8052 (P3.1) is assigned to TxD and pin 10 (P3.0) is

designated as RxD. These pins are TTL compatible; therefore, they require a line driver to

make them RS232 compatible. One such line driver is the MAX232 chip. This is

discussed next.

3.3.4 MAX232

Since the RS232 is not compatible with 8052, we employ RS232 (voltage

converter) to convert the signals to TTL voltage levels that will be acceptable to the


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8051s TxD and RxD pins. One example of such a converter is MAX232 from Maxim

Corp. The RS232 voltage levels to TTL voltage levels, and vice versa. Other advantage of

the MAX232 chip is that it uses a +5V power source which, is same as the source voltage

for 8052.

The MAX232 has two sets of line drivers for transferring and receiving data, as

shown in the figure below. The line drivers used for TxD are called T1 and T2, while line

drivers for RxD are designated as R1 and R2. In many of the applications only one of

each is used. For example, T1 and R1 are used together for TxD and RxD of the 8052,

and the second is left unused. The T1in pin is the TTL side and is connected to TxD of

the microcontroller, while T1out is the RS232 side that is connected to the RxD pin of

RS232 DB connector. The R1 line driver has a designation of R1in and R1out on pin

numbers 13 and 12, respectively. The R1in (pin 13) is the RS232 side that is connected to

the TxD pin of the RS232 DB connector, and R1out (pin 12) is the TTL side that is

connected to the RxD pin of the microcontroller. MAX232 requires four capacitors

ranging from 1 to 22 uF. The most widely used value for this capacitors is 22 uF.

Fig. 3.9 Pin diagram of MAX232

Applications of MAX232:

1. Portable Computers

2. Low-Power Modems


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3. Interface Translation

4. Battery-Powered RS-232 Systems

5. Multidrop RS-232 Networks

3.4 CIRCUIT LAYOUT

1. Main controller board

Fig. 3.10 Main controller board circuit


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2. Relay Board

Fig. 3.11 Relay board circuit

3. Power supply board

Fig. 3.12 Power supply circuit


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3.5 PCB LAYOUTS

1) PCB Layout for Main Controller Board

Fig. 3.13 PCB layout of main controller board


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2) PCB layout for Relay Board

Fig. 3.14 PCB layout of Relay board

3) PCB Layout for Power Supply Board

Fig. 3.15 PCB layout of power supply board


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3.6 SYSTEM SOFTWARE DESIGN

As our project work involved the applications of software, on consulting with

our project guide we came to the conclusion that we shall use Embedded C for

programming utilizing the Keil software.

Use of embedded processors in passenger cars, mobile phones, medical

equipment, aerospace systems and defense systems is widespread, and even everyday

domestic appliances such as dish washers, televisions, washing machines and video

recorders now include at least one such device. There is a large and growing international

demand for programmers with 'embedded' skills, and many desktop developers are

starting to move into this important area.

The applications of Embedded C are exploited through the Keil software. Keil

was founded in 1986 to market add-on products for the development tools provided by

many of the silicon vendors. It soon became evident that there was a void in the

marketplace that must be filled by quality software development tools. It was then that

Keil implemented the first C compiler designed from the ground-up specifically for the

8051 microcontroller.

Need of programming in Embedded C

The compiler produces HEX files that we download into the ROM of the

microcontroller. The size of HEX file produced by the compiler is one of the main

concerns of microcontroller programmers for the following 2 reasons:

1.Microcontrollers have limited on chip ROM.

2.The code space for 8051 is limited to 64 Kbytes.

The choice of programming language can affect the compiled program size.

While Assembly language produces a hex life that is much smaller than C

programming, in assembly language it is tedious and time consuming process to write

system program code. While in Embedded C it is much easier to write the system

program code, but the hex files size produced is much larger if we need assembly

language.

The following are some of major reasons for writing C instead of Assembly:

1. It is easier & less time consuming to write in C than Assembly.

2. C is easier to modify & update.

3. You can use code available in function libraries.

4. C code is portable to other microcontrollers with little or no modifications.

5. It is easier to develop and understand.


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KEIL Micro Vision is an integrated development environment used to create

software to be run on embedded systems such as a microcontroller. It allows for such

software to be written either in assembly or C programming languages and for that

software to be simulated on a computer before being loaded onto the microcontroller.

The code language used is C.

Fig. 3.16 Keil Vision IDE

3.6.1 ALGORITHM

Before designing any program it is necessary to first develop its algorithm and

basic flowchart. Algorithm is the set of simple and easily understandable statements that

aims to solve the problem in few steps. An algorithm is a representation of a solution to a

problem. If a problem can be defined as a difference between a desired situation and the

current situation in which one is, then a problem solution is a procedure, or method, for

transforming the current situation to the desired one. We solve many such trivial

problems every day without even thinking about it, for example making breakfast,

travelling to the workplace etc.

1. Initialize the receiver

2. Check for new commands

3. Read commands

4. Update status of relays


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5. Delete message

6. Go to step 1

3.6.2 FLOWCHART

Flowcharting is a tool developed in the computer industry, for showing

the steps involved in a process. A flowchart is a diagram made up of boxes, diamonds

and other shapes, connected by arrows - each shape represents a step in the process, and

the arrows show the order in which they occur. Flowcharting combines symbols and

flowlines, to show figuratively the operation of an algorithm.

Fig. 3.17 Flowchart of system code

START

Initialize receiver

Check

whether new

message?

Switch relay

No

Yes

Delete message

Request new command

Receive message from

Modem

Get message


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3.6.3 SYSTEM PROGRAM

#include // standard 8052 library

#include // for using printf

sbit RELAY1=P1^4;

sbit RELAY2=P1^5;

sbit RELAY3=P1^6;

sbit RELAY4=P1^7;

unsigned char z,ret;

unsigned char MSGMODE[] = "AT+CMGF=1"; //text message mode

unsigned char MSGREAD[] = "AT+CMGS=1"; //read 1st message

unsigned char MSGDEL[] = "AT+CMGD=1"; //delete message

void send_rqst(void);

unsigned char get_response(void);

void relay(unsigned char);

void del_msg(void);

void carriage_return(void);

void serial_init(void);

void main(void);

{

serial_init();

RELAY1=0;

RELAY2=0;

RELAY3=0;

RELAY4=0;

while(1){

send_rqst(); // send request

ret = get_response(); // get message

relay(ret); // switch relay

del_msg(); // delete message

}

}


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/* set up serial link */

void serial_init()

{

SCON = 0x50;// 8-bit UART mode

TMOD = 0x20; // timer 1 mode 2 auto reload

TH1 = 0xFD; // 9600 8-n-1

TR1 = 1; // run timer1

}

/* SEND MESSAGE REQUEST */

void send_rqst()

{for (z=0;z


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/* Switch relay according to input */

void relay(unsigned char ret)

{

switch(ret)

{

case '1':

RELAY1=1;

break;

case '2':

RELAY2=1;

break;

case '3':

RELAY3=1;

break;

case '4':

RELAY4=1;

break;

case '5':

RELAY1=0;

break;

case '6':

RELAY2=0;

break;

case '7':

RELAY3=0;

break;case '8':

RELAY4=0;

break;

}

}


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/* delete message */

void del_msg()

{

for (z=0;z


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4. PERFORMANCE ANALYSIS

4.1 FIRST INSTALLATION

The operation of complete unit with basic setup is explained here:

1. Prepare a rough map of the room or hall in which the appliance control is to be

achieved. Detailing should be restricted to interested appliances and wiring or

electric installations and fittings.

2. Check the appliances ratings for current consumption rating (I). If the current

drawn is not mentioned then it can be reckoned from power rating as

I (A) = Power (W) / 230 (V).

3. If the current rating is lower than or equal to 5A, then the appliance is readily

compatible with the relays used. If not, relay(s) must be replaced with those

having current rating higher than I.

4. Trace out the suitable central switchboard panel in the hall. This point can be

easily selected as the switchboard that is equidistant from most appliances or from

their respective supply points.

5. Open the switchboard panel and find out phase wire points in plug sockets. Phase

lines are live conductors which can be identified by phase testers. Open the phase

line connection to socket and connect the relay path wires to just openedterminals.

6. Now the connection of the mains supply to the appliances connected to these

sockets are controlled by two switchesphysical make or break switches and the

relay board switches.

7. Note the serial numbers of socket against relay numbers.

8. Plug the power connector of appliances to sockets and remember its serial

numbers.

9. Turn on the switches of appliances to be used.

10.Connect the DC adapter of GSM modem and AC supply socket to switchboard.

These plugs are to be connected where we have not connected relays, as they are

always kept in ON condition.

11.Place the SIM card in GSM modem in the mentioned manner and lock it.

12.SIM card should be chosen to provide good coverage in the whole home.

13.Turn the modem and main controller board ON and switch them OFF only when

system is not to be used for long time such as 1 day or more.


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4.2 ROUTINE OPERATION

1. To control any appliance, its serial no. must be remembered first.

2. Select the write text message function from menu in the mobile phone.

3. Write the control word followed by # (brackets not to be included). If more than

one action is required, write them serially, separated by ,.

4. Example: To turn appliance 1 on, write message 1#, to turn it off 5#. To switch

appliance 4 on and turn appliance 2 off, write 4#,6#.

5. Send the message to the mobile phone number of the SIM by pressing SEND or

CONNECT key. For frequent operation, this number should be stored in the

phone directory.

6. When the message is received by modem, it is decoded and respective appliances

are turned on or off.

7. If, for some reason, the system doesnt work, press RESET key on main controller

board. That should turn all the appliances off irrespective of their initial

conditions.

4.3 CONTROL WORDS

Appliance Serial No.Control Words

To turn ON To turn OFF

1 1# 5#

2 2# 6#

3 3# 7#

4 4# 8#

1 and 2 1#,2# 5#,6#

1 and 3 1#,3# 5#,7#

1 and 4 1#,4# 5#,8#

2 and 3 2#,3# 6#,7#

2 and 4 2#,4# 6#,8#

3 and 4 3#,4# 7#,8#

1, 2 and 3 1#,2#,3# 5#,6#,7#

1, 2 and 4 1#,2#,4# 5#,6#,8#

1, 3 and 4 1#,3#,4# 5#,7#,8#

2, 3 and 4 2#,3#,4# 6#,7#,8#

1,2,3 and 4 1#,2#,3#,4# 5#,6#,7#,8#

Table 4.1 Control words


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The control message sent to the system may contain any of the codeword given

in the table 4.1 and other possible combinations. The order of the commands has no effect

on the operation as will be seen soon in the results table 4.2.

4.4 RESULTS

CaseSENT MESSAGE

(INPUT)RESPONSE (OUTPUT)

1 1# APPL 1 turns on




5 5# APPL 1 turns off

6 6# APPL 2 turns off

7 7# APPL 3 turns off8 8# APPL 4 turns off

9 1#,2# APPL 1 and APPL 2 turns on



12 2#,1# Same response as case 12




16 5#,6# APPL 1 and APPL 2 turns off





21 7#,

GSM Based Remote Appliance Control System

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