GSM Based Campus Display System

CAPSTONE PROJECT

Submitted in fulfillment of the

requirement for the award of the

Degree of

BACHELOR OF TECHNOLOGY

IN

Electronics and Communication Engineering

By

Sharwan Kumar

Hemant Kumar Singh

Rahul Kumar

Komal Karan

Brijesh Yadav

Under the Guidance of

Asst Prof. Komal Arora

Lovely Professional University

Punjab

Month and Year of Submission (APRIL 2014)

i

CERTIFICATE

This is to certify that the Project Report titled GSM Based Campus Display System that is being

submitted by Sharwan Kumar, Rahul Kumar, Hemant Kumar Singh, Komal Karan and Brijesh

Yadav are in partial fulfilment of the requirements for the award of BACHELOR OF

TECHNOLOGY DEGREE, is a record of bonafide work done under our guidance.

The content of this Project Report, in full or in parts have neither been taken from any other source

nor have been submitted to any other institute or University for award of any degree.

Ms. Komal Arora

Assistant Professor

Lovely Professional University

Phagwara, Punjab

Objective of the Report is Satisfactory / Unsatisfactory

E x a m i n e r I E x a m i n e r I I

ii

ACKNOWLEDGEMENT

The Students are free to acknowledge all those whom they feel they should acknowledge on the

basis of the guidance and help provided during the implementation of the Project work. If the

students have conducted their project elsewhere (viz. outside Lovely Professional University)

appropriate acknowledgement should be given to all concerned.

It is customary to acknowledge the University Management & our School Dean for giving the

candidates an opportunity to carry out their studies at the University.

Submitted By:-

Sharwan Kumar (11003078)

Hemant Kumar Singh (11011283)

Rahul Kumar (11002826)

Komal Karan (11008428)

BrijeshYadav (11011445)

iii

CERTIFICATE

This is to certify that Sharwan Kumar, Rahul Kumar, Hemant Kumar Singh, Komal Karan and

Brijesh Yadav have completed their thesis titled, GSM Based Campus Display System under

my guidance and supervision. To the best of my knowledge, the present work is the result of their

original investigation and study. No part of the Project Report has ever been submitted for any other

degree at any University.

The Project Report is fit for submission and the partial fulfillment of the conditions for the award of

BACHELOR OF TECHNOLOGY.

Date: 25/04/2014

Ms.Komal Arora

Assistant Professor

Lovely Professional University

Phagwara, Punjab.

iv

DECLARATION

We Sharwan Kumar, Rahul Kumar, Hemant Kumar Singh, Komal Karan and Brijesh Yadav

students of B.Tech.(ECE) under Department of Electronics and Communication Engineering of

Lovely Professional University, Punjab, hereby declare that all the information furnished in this

project report is based on my own intensive research and is genuine.

This project does not, to the best of my knowledge, contain part of our work which has been

submitted for the award of our degree either of this university or any other university without

proper citation.

Date: 25/04/2014 Signature and Name of the student

Sharwan Kumar (11003078)

Hemant Kumar Singh (11011283)

Rahul Kumar (11002826)

Komal Karan (11008428)

BrijeshYadav (11011445)

v

ABSTRACT

Wireless communication has announced its arrival on big stage and the world is going mobile.

Everything needs to be controlled without movement of an inch. This remote control of appliances

is possible through Embedded Systems. The use of Embedded System in Communication has

given rise to many interesting applications that ensures comfort and safety to human life.

The main aim of the project will be to design a SMS driven automatic display board which can

replace the currently used programmable electronic display. It is proposed to design receive cum

display board which can be programmed from mobile phone. The message to be displayed is sent

through a SMS from an authorized transmitter. The GSM modem receives the SMS and displays

the desired information. Started off as an instantaneous News display unit, this project has been

improved by taking the advantage of the computing capabilities of microcontroller.

The system required for the purpose is a Microcontroller based SMS box. The main components

are microcontroller, GSM modem. These components are integrated with the display board and thus

incorporate the wireless features. The GSM modem receives the SMS. The AT commands are

serially transferred to the modem through MAX232. In return the modem transmits the stored

message through the COM port. The microcontroller validates the SMS and then displays the

message in the LCD display board.

vi

LIST OF TABLES

Page no.

1. Series of Diode 18

2. Port 3 Configuration 30

3. MAX 232 Pin Specifications 33

vii

LIST OF FIGURES

Page no.

1. Block Diagram Representation 8

2. Flow Chart Representing 9

3. Operational Flow Chart 10

4. Proteus Schematic Snapshot 12

5. Resistors 14

6. Carbon Resistors 15

7. Electrolytic Capacitor 16

8. Ceramic Capacitor 16

9. Frequency Diode 17

10. Full and Half Wave Rectifier 17

11. IN400X Series Diode 18

12. Pull Down Resistor 18

13. Voltage Divider Circuit 19

14. LEDs 19

15. LED Circuit 20

16. IC 7805 20

17. Crystal Oscillator 21

18. Transformer Circuit 22

19. Center Tapped Transformer 22

viii

20. Winding of Transformer 23

21 Center Tapped Transformer 23

22. Rectifier with Power Supply 24

23. Diagram of Microprocessor and Microcontroller 26

24. Pin Diagram of 8052 28

25. Oscillator Circuit 28

26. Reset Switch 29

27. LCD 2*16 Character Module 32

28. MAX 232(operating circuit) 34

29. GSM Module 37

ix

TABLE OF CONTENTS

CONTENTS Page no.

LIST OF TABLES

LIST OF FIGURES

CHAPTER 1-INTRODUCTION 1

1.1 Brief Introduction to Wireless Communication 1

1.2 Objective and Goal of Project 1

1.3 An Insight to Approach 2

CHAPTER 2- LITERATURE REVIEW 3

2.1 Internet Based Monitoring 3

2.2 GSM-SMS Based Monitoring 5

2.3Remote Monitoring Wireless Sensor Networks (WSN) 6

CHATPER 3- PROJECT DESCRIPTION 8

3.1 Block Diagram 8

3.2 Flow Chart 9

3.3 Operational Flow Chart 10

3.4 Software Required 11

x

CHAPTER 4- HARDWARE PROFILE 13

4.1 Basic Components Description 13

4.2 Power Supply and Rectifier 24

4.3 LCD and GSM Interfacing with Microcontroller 25

CHAPTER 5- RESULT AND DISCUSSION 36

5.1 Offline Testing Result 36

5.2 Online Testing and Observation 36

5.3 Overview 37

5.4 Proposal 37

CHAPTER 6- CONCLUSION 39

6.1 Conclusion and Problem Faced 39

6.2 Future Improvements 39

CHAPTER7- REFERENCES 41

7.1 Books 41

7.1 URLs 41

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CHAPTER 1

INTRODUCTION

1.1 A BRIEF INTRODUCTION TO WIRELESS COMMUNICATION

In the present time technologically is advancing in our country in the area of telecommunications

with about 126 million phone lines, 7.5 million cellular phone users, 5 thousand AM radio

broadcast stations, 5 thousand FM radio stations, 1 thousand television broadcast stations, 9

thousand cable television systems, 530 million radios, 193 million television sets, 24 ocean cables,

and scores of satellite facilities. This is truly an "Information Age" and sometimes, we need to look

at where we have been in order to see the future more clearly. A term to describe communication

where a piece of information is sent or transmitted from one point to all other points. There is just

one sender, but the information is simultaneously sent to all connected receivers. In networking, a

distinction is made between broadcasting and multicasting. Broadcasting sends a message to

everyone on the network whereas multicasting sends a message to a select list of recipients.

One of the most common examples is broadcast through a cellular network service. This serves

multiple end users at different locations in a simulcast fashion. Practically every cellular system has

some kind of broadcast mechanism. This can be used directly for distributing information to

multiple mobiles, commonly, for example in a mobile telephony system, the most important use of

broadcast information is to set up channels for one to one communication between the mobile

Trans-receiver and the base station. This is called paging.The details of the process of paging vary

somewhat from network to network, but normally we know a limited number of cells where the

phone is located (this group of cells is called a location area in the GSM system or Routing Area in

UMTS). Paging takes place by sending the broadcast message on all of those cells.

1.2 OBJECTIVE AND GOAL OF PROJECT

Today, interaction with digital displays is a deskbound or device-dependent experience. However,

developments in display and information sharing technologies may enable a new form of

interaction with digital media: ubiquitous computing. In ubiquitous computing, the physical

location of data and processing power is not apparent to the user. Rather, information is made

available to the user in a transparent and contextually relevant manner. A single display device

restricts the repertoire of interactions between the user and digital media, so ubiquitous computing

requires displays wherever the user might need one in appliances, tabletops public transport, walls,

etc.Wireless communication has announced its arrival on big stage and the world is going mobile.

This enables us to display a message at a specific location by a single handed cell phone user in just

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a click of a command button. We want to control everything and without moving an inch. This

remote control of appliances is possible through Embedded Systems. The use of Embedded

System in Communication has given rise to many interesting applications that ensures comfort and

safety to human life.Our project aims at integrating the expansiveness of a wireless cellular network

and the ease of information transfer through the SMS with the coverage of public display boards. It

is thereby a modest effort to realize the complete potential of public display boards in instantaneous

information broadcast in swift response to events of interests. The system required for this purpose

is a Microcontroller based SMS Module. The main components are microcontroller, GSM modem,

Serial Driver.

1.3 AN INSIGHT TO APPROACH

These components are integrated with the display board and thus incorporate the wireless features.

The GSM modem receives the SMS. The AT commands are serially transferred to the modem

through MAX232. In return the modem transmits the stored message through the COM port. The

microcontroller validates the SMS and then displays the message in the LCD display board.

This many-to-one network of SMS transmission has become quite popular and many a business has

entered into this model with mixed results. However, as of this writing, the vast majority of

businesses that revolve around the GSM-SMS system have been targeted to consumers. This paper

aims to propose industrial applications that will utilize the distinct advantages of the GSM.SMS

system over other possible technologies in the industrial setting.

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CHAPTER 2

LITERATURE REVIEW

The literature related to this project has been reviewed for last twenty years in order to find out

work carried out by various researchers. There are many systems for remote monitoring and control

designed as commercial products or experimental research platforms. It is noticed that most of the

research carried out belongs to the following categories:

Internet based Monitoring using Servers, GPRS modems, etc. with different approaches.

GSM-SMS protocols using GSM module individually or in combination with Internet.

Monitoring using Wireless Sensor Networks.

Wireless Monitoring using Bluetooth, Wi-Fi and RF

2.1 INTERNET BASED MONITORING

Internet monitoring is one of the common approaches for remote monitoring. Many researchers

have worked in field of Internet based remote monitoring.

Al-Ali and Al-Rousan, 2004 developed Java based home automation system via World Wide Web.

The home appliances were controlled from ports of embedded system board connected to PC based

server at home. RF and master node has serial RS232 link with PC server. The nodes are based on

AT89S52c.PC server is formed of a user interface component, the database and the web server

components. An Internet page has been setup running on a Web server. The user interface and the

Internet front end are connected to a backend data base server. The control of devices is established

and their condition is monitored through the Internet.[2]Al-Khateeb, 2009 used X10 controller

interfaced through serial port to PC server for control of devices. The Common Gateway Interface

(CGI) is used to interface between the browser and the X10 protocol via http connection. The server

executes CGI programs in order to satisfy a particular request from the browser, which expresses its

request using the http.

Peng Liul, 2007developed model of web services based email extension for remote monitoring of

embedded systems which integrates web services into emails. It uses a general purpose email

messaging framework to connect devices and manipulators. This low cost model fits for systems

with low connection bandwidth, small data transportation volume and non real- time control, e.g.,

monitoring of home appliances and remote meter-reading. Tan and Soy, 2002 developed a system

for controlling home electrical appliances over the Internet by using Bluetooth wireless technology

to provide a link from the appliance to the Internet and Wireless Application Protocol (WAP) to

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provide a data link between the Internet and a mobile phone. However, technical details relating

controller are not revealed. Nikolova et al, 2002 demonstrated that the control of home appliances

can be extended beyond the home network to wireless mobile networks without any modification in

the network specifications. This was accomplished by developing and implementing a HAVi

(Home Audio Video Interoperability) - WAP UI gateway that intermediates between a wired home

network and a wireless communication network using HAVi and WAP specifications, respectively.

The gateway uses both pull and pushes technologies, improves the network integration and provides

opportunities for developing applications that combine mobile devices with home network devices.

Yen-Shin Lai et al, 2002 developed an Internet-based monitoring and control of fuzzy controlled

inverter for air conditioning system. The system consists of client/server, programmable logic

controller, D/A modules, inverters, induction motors and the temperature sensing modules. The

client accepts the command from the user and can also access the database created in server, using

Internet Explorer (IE) Browser. The server performs function of fuzzy logic control,

communication interface between server and PLC, and receiving command from client.

Furthermore, the server also creates a database of the sensed temperature, speed of inverter-

controlled motor drives, and reference command. Chen Chao, 2009 developed a remote wireless

monitoring system for off grid Wind turbine based on the GPRS and the Internet. The remote

monitoring system is made up of three parts: controlling terminal, central monitoring computer and

communication network.

Controlling terminal consists of microcontroller ARM7 LM3S1138, data acquisition module and

GPRS communication module WAVECOM Q2406B connected to ARM7 system using serial port.

GPRS module sends parameters relating wind turbine to central monitoring computer. The client

can access central monitoring computer server through Internet and know parameters of different

wind turbines. Kumari and Malleswaran, 2010 developed real time based equipment condition

monitoring and controlling system using embedded web based technology which directly connects

the equipment to network as a node. The embedded system consists of ARM7 based LPC 2148

microcontroller board, A/D, signal conditioning, sensors, and communications interface. The

function of web based system is to collect the real time data information of the on-site equipment

and remotely send the data in the form of user defined data transmission style. The remote

Computer collects the data and running status through the network and provides the comparison on

the historical data. If the parameter value is different from the original set value, the corrected

signal is sent to the control unit.[8]

The embedded remote monitoring system completes the data Collection in the embedded platform

and provides the data to remote host through the TCP/IP protocol from Web server. It creates

condition to realize unattended management through providing Web-based graphical management

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interface for the Internet or LAN users. Hongping and Kangling, 2010 proposed the architecture of

embedded remote monitoring system based on Internet. The system adopts embedded web server as

a central monitoring node and results in improvement in stability and reliability of system.

Moreover, utilization of dynamic monitoring web based on Java Applet improves the response

capability and brings convenience for complex monitoring web design. Zhu and Cui, 2007

developed remote intelligent monitoring system based on embedded Internet technology for device-

room monitoring of the campus network. The Intelligent Monitoring Terminal (IMT) is provided

with the functions of Embedded Internet Node Unit and local MSD (Monitoring System Devices).

IMT can give alarm of theft or fire according to detection analysis of temperature, sound and smog.

And it also can connect to Internet for carrying out remote data communication. The MCU

S3C44B0, which utilize 32-bit ARM kernel, is adopted in intelligent monitoring terminal. Clinux

operating system is chosen as the software core of embedded system. It offers self-contained

TCP/IP network protocol module and provides strong support for embedded Internet technology.

2.2 GSM-SMS BASED MONITORING

With the wide spread use of cellular networks, this approach is also popular when small amount of

data is to be transferred through the network. Extensive work has been carried out by researchers

using this approach especially in medical field.Chen Peijiang and Jiang Xuehua, 2008 describe a

remote monitoring system based on SMS of GSM. The system includes two parts which are the

monitoring center and the remote monitoring station. The monitoring center consists of a computer

and a TC35 GSM communication module. The computer and TC35 are connected by RS232. The

remote monitoring station includes a TC35 GSM communication module, a MSP430F149 MCU, a

display unit, various sensors, data gathering and processing unit.[2].Jiang et al, 2008 proposed a

system for early diagnosis of hypertension and other chronic diseases. The proposed design consists

of three main parts: a wrist Blood Pressure (BP) measurement unit, a server unit and a terminal unit.

Blood Pressure is detected using data acquired by sensors intelligently using DSP microchip. The

data is then transmitted to the remote server unit located at Community Healthcare Centers/Points

(CHC/P) by using Short Messaging Service (SMS), and notification information is sent to the

terminal unit to inform users if patients BP is abnormal.

Xu Meihua, 2009 described a remote medical monitoring system based on GSM (Global System for

Mobile communications) network. This system takes advantage of the powerful GSM network to

implement remote communication in the form of short messages and uses FPGA as the control

center to realize the family medical monitoring network. The system is made up of user terminal

equipments, GSM network and hospital terminal equipments. Hospital terminal equipments can be

a personal computer (connected with GSM modules) or other receiving equipments such as the

Page | 6

mobile phone of the related doctor, while user terminal equipments are used to collect, demonstrate

and transmit kinds of physiological parameters. User terminal devices include the temperature

acquisition module, blood pressure/heart rate acquisition module, FPGA of Actel Fusion series,

information-sending and information-receiving module Siemens TC35 GSM module, LCD displays

and expansion modules.Van Der Werff, 2005 proposed a mobile-based home automation system

that consists of a mobile phone with Java capabilities, a cellular modem, and a home server. The

home appliances are controlled by the home server, which operates according to the user commands

received from the mobile phone via the cellular modem.In the proposed system the home server is

built upon an SMS/GPRS (Short Message Service/General Packet Radio Service) mobile cell

module Sony Ericsson GT48 and a microcontroller Atmel AVR 169, allowing a user to control and

monitor any variables related to the home by using any java capable cell phone.

Khiyal, 2009 proposed SMS based system for controlling of home appliances remotely and

providing security when the user is away from the place. Home appliance control system (HACS)

consists of PC which contains the software components through which the appliances are controlled

and home security is monitored and GSM Modem that allows the capability to send and receive

SMS to and from the system. The communication with the system takes place via RS232 serial port.

2.3 REMOTE MONITORING WIRELESS SENSOR NETWORKS (WSN), BLUETOOTH,

WI-FI, ZIGBEE TECHNOLOGIES

Many Wireless Technologies like RF, Wi-Fi, Bluetooth and Zigbee have been developed and

remote monitoring systems using these technologies are popular due to flexibility, low operating

charges, etc. Today Wireless Sensor Network are used into an increasing number of commercial

solutions, aimed at implementing distributed monitoring and control system in a great number of

different application areas.[4]Wijetunge, 2008 designed a general purpose controlling module

designed with the capability of controlling and sensing up to five devices simultaneously. The

communication between the controlling module and the remote server is done using Bluetooth

technology.The server can communicate with many such modules simultaneously. The controller is

based on ATMega64 microcontroller and Bluetooth communication TDK Blu2i module which

provides a serial interface for data communication. The designed controller was deployed in a home

automation application for a selected set of electrical appliances.Kanma, 2003 proposed a home

appliance control system over Bluetooth with a cellular phone, which enables remote-control, fault-

diagnosis and software-update for home appliances through Java applications on a cellular phone.

The system consists of home appliances, a cellular phone and Bluetooth communication adapters

for the appliances.The communication adapter hardware consists of a 20MHz 16bit CPU, SRAM

and a Bluetooth module. The communication adapter board is connected to the home appliance and

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to the cellular phone through serial ports. The appliances can communicate with the cellular phone

control terminal via Bluetooth SPP.Yunseop Kim, 2008 described details of the design and

instrumentation of variable rate irrigation, a wireless sensor network, and software for real-time in-

field sensing and control of a site-specific precision linear-move irrigation system. Communication

signals from the sensor network and irrigation controller to the base station were successfully

interfaced using low-cost Bluetooth wireless radio communication through Bluetooth RS-232 serial

adaptor (SD202, Initium Company).Harms, 2010describe the emerging wireless sensor networks

(WSN) for autonomous Structural Health monitoring SHM systems for bridges. In SmartBrick

Network, the base station and sensor nodes collect data from the onboard and external sensors. The

sensor nodes communicate their data from quasi-static sensors, e.g., temperature sensors, strain

gauges and seismic detectors to the base station over the ZigBee connection. The base station

processes these data and communicates them, along with any alerts generated, to a number of

destinations over the GSM/GPRS link provided by the cellular phone infrastructure. The data are

reported by email and FTP to redundant servers, via the Internet, at regular intervals or on an event-

triggered basis. The alerts are sent directly by SMS text messaging and by email. Wireless sensor

networks are the key enabler of the most reliable and durable systems for long-term SHM and have

the potential to dramatically increase public safety by providing early warning of impending

structural hazards.Mulyadi,2009 implemented a wireless medical interface based on ZigBee and

Bluetooth technology. The purpose is to acquire, process, and transfer raw data from medical

devices to Bluetooth network. The Bluetooth network can be connected to PC or PDA for further

processing. The interface comprises two types of device: MDIZ and MDIZB.MDIZ acquires data

from medical device, processes them using microcontroller, and transmit the data through ZigBee

network through UART. MDIZB receives data from several MDIZs and transmit them out to PC

through Bluetooth network. MDIZB comprises of ZigBee module, two processors, RAM, and

Bluetooth module. It receives data from ZigBee network through its ZigBee module. The data are

then sent to processor 1. Processor 1 decides priority of MDIZs. In processor 1, the data frame is

added with Start byte and End byte to mark the beginning and the end of data frame.

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CHAPTER 3

PROJECT DESCRIPTION

As explained in the introduction chapter, the realization of complete circuitry of the Display

boards and the wireless GSM medium in information transfer is the major issue that the

following project deals with.

3.1 BLOCK DIAGRAM

As we see in the figure below, there are three interfacing circuits, MAX-232 with

microcontroller, LCD display with microcontroller, and MAX-232 with GSM MODEM. The

display boards used commercially can be as follows

Figure 1: Block Diagram Representation [12]

The block diagram clearly represents the interconnection and interfacing of the various modules of

the circuit as is implemented on board, as we soldered on the Zero PCB. The various modules are a

Power circuit, a Rectifier circuit, a GSM modem, a MAX 232 driver, a microcontroller AT89S52,

Alarm Circuit with a Buzzer and a LCD Display. The GSM module acts as a Receiver circuit for

the message transmitted by the end user through a cell phone.

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3.2 FLOW CHART

Figure 2: Flow chart representing the end user perspective on control flow [4]

The above given flowchart gives the end user perspective on the control flow. During normal

operations the LCD reads a message from a fixed memory location in the microcontroller and

displays it continuously, until a new message arrives for validation. It is then when a branching

occurs basing on the validity of the senders number and further taking into account the priority

assigned to the new message in comparison to the previous one.

Start

Check for new message

Is the

senders

no. valid?

end

Keep displaying

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3.3 OPERATIONAL FLOW CHART

Figure 3: Operational Flow Chart

3.3.1. Initializations

The baud rate of the modem was set to be 9600 bps using the command AT+IPR=4800.The ECHO

from the modem was turned off using the command ATE/ATE0 at the hyper terminal. For serial

transmission and reception to be possible both the DTE and DCE should have same operational

baud rates. Hence to set the microcontroller at a baud rate of 9600bps, we set terminal count

of Timer 1 at 0FFh (clock frequency = 1.8432). The TCON and SCON registers were set

accordingly.

start

Initialisation band rate

Serial transmission

microcontroller modem

AT + CMGR = 1

SERIAL RESPONSE MESSAGE ERROR STORED IN RAM

Message

Print ?

LCD Display

END

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3.3.2. Serial transfer using TI and RI flags

After setting the baud rates of the two devices both the devices are now ready to transmit and

receive data in form of characters. Transmission is done when TI flag is set and similarly data is

known to be received when the Rx flag is set. The microcontroller then sends an AT command to

the modem in form of string of characters serially just when the TI flag is set. After reception of a

character in the SBUF register of the microcontroller (response of MODEM with the read message

in its default format or ERROR message or OK message), the RI flag is set and the received

character is moved into the physical memory of the microcontroller.[1]

3.3.3. Validity Check

After serially receiving the characters the code then checks for start of the senders number and then

compares the number character by character with the valid number pre stored in the memory. Since

we are employing just one valid number, we are able to do the validation process dynamically i.e.

without storing the new message in another location in the memory. For more than one valid

numbers we would require more memory locations to first store the complete (valid/invalid)

message in the memory and then perform the comparison procedure.

3.3.4 Display

After validity check the control flow goes into the LCD program module to display the valid

message stored in the memory. In case of multiple valid numbers all invalid stored messages are

deleted by proper branching in the code to the delete-message module.

3.4 SOFTWARE REQUIRED

Embedded C

Embedded C is used for microcontroller programming. 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. Because most embedded projects have severe cost constraints, they tend to

use low-cost processors like the 8051 family of devices considered in this paper.

Keil

Keil development tools for the 8051 Microcontroller Architecture support every level of 4software

developer from the professional applications engineer to the student just learning about embedded

software development. The Keil 8051 Development Tools are designed to solve the complex

problems facing embedded software developers.[1]

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Proteus Schematic Snapshot

Figure 4: Proteus Schematic Snapshot [12]

Page | 13

CHAPTER 4

HARDWARE PROFILE

4.1 BASIC COMPONENTS DESCRIPTION

1. Transformer (12V)

2. Diodes (IN4007)

3. Capacitor (470uF,1000uf,22pf)

4. Voltage Regulator (7805 & 7812)

5. Resistors

6. LED

7. GSM Modem

8. MAX 232

9.Transistors

10.IC bases

11. Ribbon wire

12. Jumper wire

13. Soldering Iron

14. Soldering Wire

15. Multimeter

16. PCB

17. Cutter

18. Screw & Nuts

4.1.1 Resistors

The flow of charge (or current) through any material, encounters an opposing force similar in many

respect to mechanical friction. This opposing force is called resistance of the material. It is

measured in ohms. In some electric circuits resistance is deliberately introduced in the form of the

resistor.

Resistors are of following types:

Wire wound resistors.

Carbon resistors.

Metal film resistors.

Wire Wound Resistors:

Wire wound resistors are made from a long (usually Ni-Chromium) wound on a ceramic

core. Longer the length of the wire, higher is the resistance. So depending on the value of

Page | 14

resistor required in a circuit, the wire is cut and wound on a ceramic core. This entire

assembly is coated with a ceramic metal. Such resistors are generally available in power of

2 watts to several hundred watts and resistance values from 1ohm to 100k ohms. Thus wire

wound resistors are used for high currents.[7]

Carbon Resistors:

Carbon resistors are divided into three types:

1. Carbon composition resistors are made by mixing carbon grains with binding material

(glue) and moduled in the form of rods. Wire leads are inserted at the two ends. After this an

insulating material seals the resistor. Resistors are available in power ratings of 1/10, 1/8,

1/4, 1/2, 1.2 watts and values Z from 1 ohm to 20 ohms.

2. Carbon film resistors are made by deposition carbon film on a ceramic rod. They are

cheaper than carbon composition resistors.

3. Cement film resistors are made of thin carbon coating fired onto a solid ceramic substrate.

The main purpose is to have more precise resistance values and greater stability with heat.

They are made in a small square with leads.

Figure 5: Resistors [12]

Metal Film Resistors

They are also called thin film resistors. They are made of a thin metal coating deposited on a

cylindrical insulating support. The high resistance values are not precise in value; however,

such resistors are free of inductance effect that is common in wire wound resistors at high

frequency.

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Example- Carbon Resistor

Figure 6: Carbon Resistor [12]

4.1.2 CAPACITORS

A capacitor can store charge, and its capacity to store charge is called capacitance. Capacitors

consist of two conducting plates, separated by an insulating material (known as dielectric). The two

plates are joined with two leads. The dielectric could be air, mica, paper, ceramic, polyester,

polystyrene, etc. This dielectric gives name to the capacitor. Like paper capacitor, mica capacitor

etc.

Types of Capacitors:-

1.Fixed capacitor.

2.Variable capacitor.

1. Fixed types of capacitor are further of two types:-

Polar Capacitor:Those capacitor have polarity are known as polar capacitor. Electrolytic

capacitor are the example of polar capacitors.

Non Polar Capacitor

Those capacitor have no polarity are known as NON- polar capacitor. Ceramic capacitor are

the example of non polar capacitors

Electrolytic Capacitor:

Electrolytic capacitors have an electrolyte as a dielectric. When such an electrolyte is

charged, chemical changes takes place in the electrolyte. If its one plate is charged

positively, same plate must be charged positively in future. We call such capacitors as

polarized.Normally we see electrolytic capacitor as polarized capacitors and the leads are

marked with positive or negative on the can. Non-electrolyte capacitors have dielectric

material such as paper, mica or ceramic. Therefore, depending upon the dielectric, these

capacitors are classified.

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Figure 7: Electrolytic Capacitor [12]

Ceramic Capacitor

Such capacitors have disc or hollow tabular shaped dielectric made of ceramic material such

as titanium dioxide and barium titanate. Thin coating of silver compounds is deposited on

both sides of dielectric disc, which acts as capacitor plates. Leads are attached to each sides

of the dielectric disc and whole unit is encapsulated in a moisture proof coating. Disc type

capacitors have very high value up to 0.001uf. Their working voltages range from 3V to

60000V. These capacitors have very low leakage current. Breakdown voltage is very high.

Figure 8: Ceramic Capacitor [12]

4.1.3 DIODE

Diodes are semiconductor devices which might be described as passing current in one direction

only. Diodes have two terminals, an anode and a cathode. The cathode is always identified by a dot,

ring or some other mark. Diode is a unidirectional device. In this the current flows in only one

direction.

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Figure 9: Frequency Diode [8]

Diodes can be used as voltage regulators, tuning devices in RF tuned circuits, frequency

multiplying devices in RF circuits, mixing devices in RF circuits, switching applications or can be

used to make logic decisions in digital circuits. There are also diodes which emit "light", of course

these are known as light-emitting-diodes or LED's.

A rectifying diode of the 1N4001-07 ( 1A) type or even one of the high power, high current stud

mounting types. You will notice the straight bar end has the letter "k", this denotes the "cathode"

while the "a" denotes anode. Current can only flow from anode to cathode the principal early

application of diodes was in rectifying / 60 Hz AC mains to raw DC which was later smoothed by

choke transformers and / or capacitors. This procedure is still carried out today and a number of

rectifying schemes for diodes have evolved half wave, full wave and bridge, full wave and bridge

rectifiers.

Figure 10: Full and Half Wave Rectifier [12]

As examples in these applications the half wave rectifier passes only the positive half of successive

cycles to the output filter through D1. During the negative part of the cycle D1 does not conduct

and no current flows to the load.

In the full wave application it essentially is two half wave rectifiers combined and because the

transformer secondary is centre tapped, D1 conducts on the positive half of the cycle while D2

conducts on the negative part of the cycle. Both add together. This is more efficient. The full wave

bridge rectifier operates essentially the same as the full wave rectifier but does not require a centre

tapped transformer. Further discussion may be seen on the topic power supplies

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1N400X Series Diode

Features

Diffused Junction

High Current Capability and Low Forward Voltage Drop

Low Reverse Leakage Current

Figure 11: 1N400X Series Diode [12]

Table: 1 Series of Diode

4.1.4 Signals from switches

When a switch is used to provide an input to a circuit, pressing the switch usually generates a

voltage signal. It is the voltage signal which triggers the circuit into action. What do you need to get

the switch to generate a voltage signal ,we need a voltage divider. The circuit can be built in either

of two ways:

Figure 12: Pull up and Pull Down Resistor [8]

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The pull down resistor in the first circuit forces Vout to become LOW except when the push button

switch is operated. This circuit delivers a HIGH voltage when the switch is pressed. A resistor value

of 10 is often used.In the second circuit, pull up resistor forces Vout to become HIGH except

when the switch is operated. Pressing the switch connects Vout directly to 0 V. In other words, this

circuit delivers a LOW voltage when the switch is pressed. In circuits which process logic signals, a

LOW voltage is called 'logic 0' or just '0', while a HIGH voltage is called 'logic1' or '1'.

These voltage divider circuits are perfect for providing input signals for logic systems. The kinds of

switches could we use. One variety of push button switch is called miniature tactile switch. These

are small switches which work well with prototype board.

Figure 13: Voltage Divider Circuit [12]

4.1.5 LED

Figure 14: LEDs [12]

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LED means light emitting diode. Its function is similar to the diode. But these are not made up from

silicon or germanium. These are generally used as a indicating device. There are variety of LEDs

are available in market depending upon their size and colour.

Polarity of LED

LED has polarity. We can judge its polarity by watching flags in its structure. Bigger flag is

known as cathode and smaller flag is known as anode as shown below.

Figure 15 LED Circuit [8]

4.1.6 Voltage Regulator

The LM78XX 3-terminal positive voltage regulators employ internal current-limiting, thermal

shutdown and safe-area compensation, making them essentially indestructible. Heat sinking is

provided; they can deliver over 1.0A output current. They are intended as fixed voltage regulators

in a wide range of applications including local (on-card) regulation for elimination of noise and

distribution problems associated with single-point regulation. In addition to use as fixed voltage

regulators.

Figure 16 IC 7805 [8]

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Features

Output current up to 1 A

Output voltages of 5; 6; 8; 9; 12; 15; 18; 24 V

Thermal overload protection

Short circuit protection

4.1.7 Crystal

Figure 17: Crystal Oscillator [8]

Its a 2 terminal component. This component has no polarity. Its basic function to generate a Square

Wave of some fixes frequency. Its value is measure in MHz

4.1.8 Transformer

Transformer works on the principle of mutual inductance. We know that if two coils or windings

are placed on the core of iron, and if we pass alternating current in one winding, back emf or

induced voltage is produced in the second winding. We know that alternating current always

changes with the time. So if we apply AC voltage across one winding, a voltage will be induced in

the other winding. Transformer works on this same principle. It is made of two windings wound.

The winding to which AC voltage is applied is called primary winding. The other winding is called

as secondary winding. Transformers are of two types Step Up transformer and Step Down

transformer.

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Figure 18: Transformer Circuit [8]

Step Up Transformer

These transformers are used to increase the voltage level at the output means Voltage at

secondary winding is more than the primary winding. In this transformer secondary winding

has more number of turns than primary winding.

Step Down Transformer

These transformers are used to decrease the voltage level at the output winding means

voltage of secondary winding is less than the primary winding. In this transformer

secondary winding has less number of turns than primary winding. These types of

transformers have major applications in electronics industry.

Further these are divided into two categories

Simple Transformer

Center Tapped Transformers

Figure 19: Center Tapped Transformer [8]

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Simple Transformer

Its a four wire transformer. These types of transformer have 2 wires on primary winding

and 2 wires on secondary output. Symbol of this transformer is shown below.

Figure 20: Winding of Transformer [12]

Center Tapped Transformer

Its a 5 Wire transformer. This type of transformer has 2 wires on primary winding and 3

wires on secondary. Middle one is known as Common. Voltage rating of this transformer

expressed as 6-0-6 V,9-0-9V, 12-0-12 V etc.

Figure 21 Center Tapped Transformer [7]

Specification of Transformer

While purchasing a transformer generally two considerations have to be kept in mind, first

one is voltage rating and second is current rating. Voltage rating depends upon the circuits

operating voltage its generally 5 or 12 Volt so 6 or 12 Volt transformers are generally

used.Current rating of transformer depends upon the load of circuit. If our load current is

more than the transformer current then due to loading effects transformer can burn out. So to

protect our transformer, current rating of transformer should be more than the load

current.All transformer comes with different current rating e.g. 6 V transformer is available

in 500m A, 750mA, 1A, 2A so on. One thing should be kept in mind as the ampear

increases cost of transformer also increases. We have to choose best one according to our

circuit requirements.[4]

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4.2 POWER SUPPLY AND RECTIFIER

Power supply is the essential part of any device or project. We are using microcontroller and LED.

These components needs +5V DC supply. So we need a power supply circuit of +5V DC. Power

supply circuit includes step down transformer, rectifier circuit, filter circuit and regulator circuit.

Figure 22: Rectifier with Power Supply [8]

An indicating component is also attached with the power supply to indicate the power ON condition

of power supply unit.Now the aim is to design the power supply section which converts 230V AC

in to 5V DC. Since 230V is too high to reduce it to directly 5V DC, therefore we need a step down

transformer that reduces the line voltage to certain voltage that will help us to convert it in to a 5V

DC.Considering the efficiency factor of the full wave, we came to a conclusion to choose a

transformer, whose secondary voltage is 3-4 higher than the required voltage. Thus a step down

transformer of 9 V and 500 mA is used to step down the AC power supply. This transformer can

provide current up to 750 mA.Our circuit load is below 750 mA. So there will not be any loading

effect on transformer. Output of transformer is given to the rectifier circuit. We are using a central

tapped full wave rectifier. In this rectifier we are using 1N4007 pn diode to rectify AC voltage.

Output of this rectifier is not purely DC. Output of rectifier is rippled DC.

So we need some filtering section to rectify these ripples. Output voltage of rectifier can be

calculated by:-

Vout = (VIN * 2)

(Forward voltage drop of diode) 1N4007 is a silicon semiconductor material based diode. So in this

case forward Voltage drop is .7 V. Final output of this rectifier be:-

Vout= (9*2) -0.7

Vout= 16.1 V

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Rectifier circuit is build of capacitor. A capacitor of 1000uF, 25V is used to filter the ripples.

Output of capacitor is almost pure DC. But its voltage is 16V and we need +5V DC.So we are

using a voltage regulator to get the desired +5V DC. A 7805 voltage regulator is a suitable

component for this purpose. Output of 7805 regulator is +5V DC. A capacitor of 470uf, 10V is

used to further filter out the critical ripples.

A LED is used as an indicating device. Most of LED operates at 1.5 to 2.5V voltage range with 8-

10 mA. LED used here is of 5mm size. We consider that LED operating at 1.6V with 8mA current.

We can calculate the value of resistor using the KVC law.

Total Voltage= Voltage across resistor+ Voltage across LED

LED and resistor are connected in series so same current will flow. Means 8mA current will flow

through the resistor.

Now Total Voltage is =5V

Voltage across resistor is =1.6v

Current is = 10mA

So our equation will be

5V= (10mA * resistance) + 1.6V

3.4V=10mA * resistance

Resistance =3.4/10mA= 340 ohm

Thus we can calculate the any series resistor for any input voltage and LED.

4.3 LCD AND GSM INTERFACING WITH MICROCONTROLLER

4.3.1 Microcontrollers (MCU)

Figure shows the block diagram of a typical microcontroller, which is a true computer on a chip.

The design incorporates all of the features found in micro-processor CPU, ALU, PC, SP, and

registers. It also added the other features needed to make a complete computer: ROM, RAM,

I/O,timer & counters,and clock circuit.

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Figure 23: Diagram of Microprocessor and Microcontroller [1]

DIFFERENCE BETWEEN MICROCONTROLLER & MICROPROCESSOR

It is very clear from figure that in microprocessor we have to interface additional circuitry

for providing the function of memory and ports, for example we have to interface external

RAM for data storage, ROM for program storage, programmable peripheral interface (PPI)

8255 for the Input Output ports, 8253 for timers, USART for serial port.While in the

microcontroller RAM, ROM, I/O ports, timers and serial communication ports are in built.

Because of this it is called as system on chip. So in micro-controller there is no necessity

of additional circuitry which is interfaced in the microprocessor because memory and input

output ports are inbuilt in the microcontroller.

Microcontroller gives the satisfactory performance for small applications. But for large

applications the memory requirement is limited because only 64 KB memory is available for

program storage. So for large applications we prefer microprocessor than microcontroller

due to its high processing speed.

4.3.2 8051 MICROCONTROLLER

Description

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

of in-system programmable Flash memory. The device is manufactured using Atmels high-

density non-volatile memory technology and is compatible with the industry-standard 80C51

instruction set and pin out.The on-chip Flash allows the program memory to be

reprogrammed in-system or by a conventional non-volatile memory programmer. By

combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip,

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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 contents but freezes the oscillator,

disabling all other chip functions until the next interrupt or hardware reset.

Features

8K Bytes of In-System Programmable (ISP) Flash Memory

Endurance: 1000 Write/Erase Cycles

4.0V to 5.5V Operating Range

Fully Static Operation: 0 Hz to 33 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

Full Duplex UART Serial Channel

Low-power Idle and Power-down Modes

Interrupt Recovery from Power-down Mode

Watchdog Timer

Dual Data Pointer

Power-off Flag

PIN CONFIGURATION OF 8051 MICROCONTROLLER

Although 8051 family members come in different packages such DIP(dual in line

package),QFP(Quad flat package), and LLC(leadless chi0p carrier),they all have 40 pins that are

dedicated to various functions such as I/O,RD,WR, address, data and interrupts.

VCC: Pin 40 provides supply voltage to the chip. The voltage source is +5 Volts.

GND: Pin 20 is the ground.

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Figure 24: PIN DIAGRAM OF THE P89C52 [1]

XTAL1 and XTAL2

The 8051 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 27 pf

value. One side of each capacitor is connected to the ground. Speed refers to the maximum

oscillator frequency connected to XTAL .When the 8051 is connected to a crystal oscillator

is powered up we can observe the frequency on the XTAL2 pin using the oscilloscope.

Figure 25: Oscillator Circuit [1]

RST

Pin 9 is the RESET pin. It is an input and is active high. Upon applying a high pulse to this

pin the microcontroller well reset and terminate all activities.

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

values the registers to be lost. It will set program counter to all zeroes.In order for the

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RESET input to be effective it must have a minimum duration of two machine cycles. In

other words the high pulse must be high for a minimum of two machine cycles before it is

allowed to go low.

Figure 26: Reset Switch [1]

PSEN

This is an output pin. PSEN stands for program store enable. In an 8031 based system in

which an external ROM holds the program code, this pin is connected to the OE pin of the

ROM.

ALE

ALE stands for address latch enable. It is an output pin and is active high. When

connecting an 8031 to external memory, port 0 provides both address and data. In other

words the 8031 multiplexes address and data through port 0 to save pins. The ALE pin is

used for de-multiplexing the address and data by connecting to G pin of the 74LS373 chip.

PORTS 0,1,2,3

All the ports upon RESET are configured as input, since P0-P3 have value FFH on them.

The following is a summary of features of P0-P3.

PORT 0

Port 0 is also designated as AD0-AD7 allowing it to be used for both address and data.

When connecting an 8051/31 to an external memory, port 0 provides both address and data.

The 8051 multiplexes address and data through port 0 to save pins.ALE indicates if p0 has

address A0-A7.in the 8051 based systems where there is no external memory connection the

pins of P0 must be connected externally to 10k-ohm pull-up resistor. This is due to the fact

that P0 is an open drain, unlike P1, P2 and P3.Open drain is a term used for MOS chips in

the same way that open collector is used for TTL chips. In many systems using the 8751,

89c51 or DS89c4*0 chips we normally connect P0 to pull up resistors.

PORT 1, PORT 2

In 8051 based systems with no external memory connection both P1 and P2 are used as

simple I/O. however in 8031/51 based systems with external memory connections P2 must

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be used along with P0 to provide the 16-bit address for the external memory. P2 is also

designated as A8-A15 indicating its dual function.Since an 8031/51 is capable of accessing

64k bytes of external memory it needs a path for the 16 bits of address. While P0 provides

the lower 8 bits via A0-a7 it is the job P2 to provide bits A8-A15 of the address. In other

words when the 8031/51 is connected to external memory P2 is used for the upper 8 bits of

the 16 bit address and it cannot be used for I/O.

PORT 3

Port 3 occupies a total of 8 pins 10 through 17. It can be used as input or output. P3 does not

need any pull-up resistors the same as P1 and P2 did not.Although port 3 is configured as

input port upon reset this is not the way it is most commonly used. Port 3 has the additional

function of providing some extremely important signals such as interrupts

Port 3 Alternate Functions

Table: 2 Port 3 Configuration [1]

P3 Bit Function Pin

P3.0 RxD 10

P3.1 TxD 11

P3.2 INT0 12

P3.3 INT1 13

P3.4 T0 14

P3.5 T1 15

P3.6 WR 16

P3.7 RD 17

Difference between RAM and ROM

RAM is used for data storage while ROM is used for program storage.

Data of RAM can be changed during processing while data of ROM cant be changed

during processing.

ACCUMULATOR (REGISTER A)

Accumulator is a mathematical register where all the arithmetic and logical operations are

done is this register and after execution of instructions the outpour data is stored in the

register is bit addressable near. We can access any of the single bit of this register.

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B REGISTER

B register is same as that of accumulator of. It is also an 8 bit register and every bit of this is

accessible. This is also a mathematical register B which is used mostly for multiplication

and division.

PSW (PROGRAM STATUS WORD) Register

Program status word register is an 8 bit register. It is also referred to as the flag register.

Although the PSW register is 8 bits wide, only 6 bits of it are used by the 8051. The unused

bits are user-definable flags.Four of the flags are called conditional flags, meaning that they

indicate some conditions that result after an instruction is executed. These four are CY

(carry), AC (auxiliary carry), P (parity) and OV (overflow).

SP (STACK POINTER, ADDRESS 81H)

This is the stack pointer of the microcontroller. This SFR indicates where the next value to

be taken from the stack will be read from in Internal RAM. If you push a value onto the

stack, the value will be written to the address of SP + 1. That is to say, if SP holds the

value 07h, a PUSH instruction will push the value onto the stack at address 08h.This SFR is

modified by all instructions, which modify the stack, such as PUSH, POP, and LCALL,

RET, RETI, and whenever interrupts are provoked by the microcontroller.[1]

DPL/DPH (DATA POINTER LOW/HIGH, ADDRESSES 82H/83H)

The SFRs DPL and DPH work together to represent a 16-bit value called the Data Pointer.

The data pointer is used in operations regarding external RAM and some instructions

involving code memory. Since it is an unsigned two-byte integer value, it can represent

values from 0000h to FFFFh (0 through 65,535 decimal).

Two instructions which are used to start and terminate program:

ORG

This instruction indicate the origin of program ORG 3000H

Means program starts from 3000H loc

This instruction hasnt taken any memory space. It is used to show the starting address of

program.

END

This instruction show the END of program or it is used to terminate the program.

4.3.3 LIQUID CRYSTAL DISPLAY

A liquid crystal display (LCD) is a thin, flat electronic visual display that uses the light modulating

properties of liquid crystals (LCs). LCs does not emit light directly. LCDs therefore need a light

source and are classified as "passive" displays. Some types can use ambient light such as sunlight or

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room lighting. There are many types of LCDs that are designed for both special and general uses.

LCDs are more energy efficient, and offer safer disposal, than CRTs. Its low electrical power

consumption enables it to be used in battery-powered electronic equipment. The LCD Module can

easily be used with an 8051 microcontroller such as the 162A. The LCD Module comes with a 16

pin connector. This can be plugged into connector 16 pin.Most common LCDs connected to the

8051 are 16x2 and 20x2 displays. This means 16 characters per line by 2 lines and 20 characters per

line by 2 lines, respectively.

Figure 27: LCD Character 2x16 Module [1]

The user may select whether the LCD is to operate with a 4-bit data bus or an 8-bit data bus. If a 4-

bit data bus is used, the LCD the 44780 standard requires 3 control lines as well as either 4 or 8 I/O

lines for the data bus. The user may select whether the LCD is to operate with a 4-bit data bus or an

8-bit data bus. If a 4-bit data bus is used, the LCD will require a total of 7 data lines (3 control lines

plus the 4 lines for the data bus). If an 8-bit data bus is used, the LCD will require a total of 11 data

lines (3 control lines plus the 8 lines for the data bus).

The three control lines are referred to as EN, RS, and RW.

Enable

The EN line is called "Enable." This control line is used to tell the LCD that you are sending it data.

To send data to the LCD, your program should first set this line high (1) and then set the other two

control lines and/or put data on the data bus. When the other lines are completely ready, bring EN

low (0) again. The 1-0 transition tells the 44780 to take the data currently found on the other control

lines and on the data bus and to treat it as a command.

Register Select

The RS line is the "Register Select" line. When RS is low (0), the data is to be treated as a

command or special instruction (such as clear screen, position cursor, etc.). When RS is high (1),

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the data being sent is text data which should be displayed on the screen. For example, to display the

letter "T" on the screen you would set RS high.

Read Write

The RW line is the "Read/Write" control line. When RW is low (0), the information on the data bus

is being written to the LCD. When RW is high (1), the program is effectively querying (or reading)

the LCD. Only one instruction ("Get LCD status") is a read command. All others are write

commands--so RW will almost always be low.Finally, the data bus consists of 4 or 8 lines

(depending on the mode of operation selected by the user). In the case of an 8-bit data bus, the lines

are referred to as DB0, DB1, DB2, DB3, DB4, DB5, DB6, and DB7.

4.3.4 MAX-232

The MAX232 is an integrated circuit that converts signals from an RS-232 serial port to signals

suitable for use in TTL compatible digital logic circuits. The MAX232 is a dual driver/receiver and

typically converts the RX, TX, CTS and RTS signals.The drivers provide RS-232 voltage level

outputs from a single + 5 V supply via on-chip charge pumps and external capacitors. This makes it

useful for implementing RS-232 in devices that otherwise do not need any voltages outside the 0 V

to + 5 V range, as power supply design does not need to be made more complicated just for driving

the RS-232 in this case.

When a MAX232 IC receives a TTL level to convert, it changes a TTL Logic 0 to between +3 and

+15 V, and changes TTL Logic 1 to between -3 to -15 V, and vice versa for converting from RS232

to TTL.The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to supply

EIA-232 voltage levels from a single 5-V supply.

Table: 3 MAX 232 pin specification

RS232 Line Type & Logic Level RS232 Voltage TTL Voltage to/from

MAX232

Data Transmission (Rx/Tx) Logic 0 +3 V to +15 V 0 V

Data Transmission (Rx/Tx) Logic 1 -3 V to -15 V 5 V

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Figure 28 MAX 232 (operating circuit) [1]

4.3.5 GSM MODEM

A GSM modem is a wireless modem that works with a GSM wireless network. A wireless modem

behaves like a dial-up modem. The main difference between them is that a dial-up modem sends

and receives data through a fixed telephone line while a wireless modem sends and receives data

through radio waves. Like a GSM mobile phone, a GSM modem requires a SIM card from a

wireless carrier in order to operate. Matrix SIM 300 is a Fixed Cellular Terminal (FCT) for data

applications. It is a compact and portable terminal that can satisfy various data communication

needs over GSM. It can be connected to a computer with the help of a standard RS232C serial

port.SIM 300 offers features like Short Message Services (SMS), Data Services (sending and

receiving data files), Fax Services and Web Browsing. Remote login and data file transfer are also

supported. It is the perfect equipment for factory plants, resorts, dams and construction sites where

wired connectivity is not available or not practicable. The SIM 300 is easy to set up. It finds its

applications in IT companies, Banks and Financial Institutions, Logistic Companies, Service

Providers, Remote Project Sites, Professionals, and such other business establishments. Computers

use AT commands to control modems. Both GSM modems and dial-up modems support a common

set of standard AT commands. GSM modem can be used just like a dial-up modem. In addition to

the standard AT commands, GSM modems support an extended set of AT commands. These

extended AT commands are defined in the GSM standards.

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With the extended AT commands, various things can be done:

Reading, writing and deleting SMS messages.

Sending SMS messages.

Monitoring the signal strength.

Monitoring the charging status and charge level of the battery.

Reading, writing and searching phone book entries.

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CHAPTER 5

RESULTS AND DISCUSSION

5.1 OFFLINE TESTING RESULT

Offline testing refers to the initial phase of testing where the module is not yet connected to the

wireless medium. This is the part of the testing process wherein we check if the MODEM receives

the AT commands from the microcontroller and makes its response in form of a new message, an

ERROR message, or an OK message (all in form of bit strings).

The oscilloscope probes are connected to P3.0 & P3.1 which are internally connected to the Tx and

Rx lines of the microcontroller. Online testing requires proper timing and delay routines, and of

course the validations step to be included.

5.2 ONLINE TESTING AND OBSERVATIONS

After inclusion of the validation module in the program code, we test the module in online mode. In

this prototype we used only one valid number. With more memory available three or four valid

numbers can be included. When a message is sent to number carried by the SIM of the MODEM,

the validation module of the program checks character by character the senders number with the

number stored in the memory as the valid or authentic number (in our case the only valid number).

With the same probe connections as in the case of offline testing, we then look for signals on the Tx

and Rx lines. What we see below on the left are the signals on these lines with the ECHO being ON

(ATE1). The corresponding picture on the right depicts the modem response after about 460 ms

(variable as per message length: D) delay with the new message.

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Figure 29: GSM Module [8]

5.3 OVERVIEW

Information sharing holds an important role in development of our institute from Regional

Engineering College (REC). The current means of information transfer are notice and circulars.

New notice or circular is only checked at the end of the day. This makes the process very time

consuming and inefficient .Looking into current trend of information transfer in the campus; it is

seen important notice take time to be displayed in the notice boards. This latency is not expected in

most of the cases and must be avoided.

5.4 PROPOSAL

It is proposed to implement this project at the institute level. It is proposed to place display boards

at major access points. These include canteens, entrance gate, hostel area etc. The proposed

locations of these display boards are shown in the figure.But, the electronics displays which are

currently used are programmable displays which need to be reprogrammed each time a new notice

comes. The process of reprogramming includes burning the microcontroller again and again.This

makes it inefficient for immediate information transfer, and thus the display board looses its

importance. The GSM based display toolkit can be used as a add-on to these display boards and

make it truly wireless. The display board programs itself with the help of the incoming SMS with

proper validation. The valid senders may include the Director, and Registrars. The centralized

system can be placed as the Computer Center for access by any other valid users with

authentications.

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SMS from these users is treated to be and is displayed. Other SMS from any other mobile phone is

discarded. Thus information from valid sources can be broadcasted easily. Such a system proves to

be helpful for immediate information transfer and can be easily implemented at the institute level.

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CHAPTER 6

CONCLUSION

6.1 CONCLUSION AND PROBLEM FACED

The prototype of the GSM based display notice board was efficiently designed. This prototype has

facilities to be integrated with a display board thus making it truly mobile. The GSM MODEM

accepts the SMS, stores it, validates it and then displays it in the LCD module. The SMS is deleted

from the SIM each time it is read, thus making room for the next SMS. The major constraints

incorporated are the use of * as the termination character of the SMS and the display of one SMS

as a time. These limitations can be removed by the use of higher end microcontrollers and extended

RAM. The prototype can be implemented using commercial display boards. In this case, it can

solve the problem of instant information transfer in the campus.

The project undertaken has helped us gain a better perspective on various aspects related to our

course of study as well as practical knowledge of electronic equipments and communication. We

became familiar with software analysis, designing, implementation, testing and maintenance

concerned with our project.

6.2 FUTURE IMPROVEMENTS

The use of microcontroller in place of a general purpose computer allows us to theorize on many

further improvements on this project prototype. Temperature display during periods wherein no

message buffers are empty is one such theoretical improvement that is very possible. The ideal state

of the microcontroller is when the indices or storage space in the SIM memory are empty and no

new message is there to display. With proper use of interrupt routines the incoming message acts as

an interrupt, the temperature display is halted and the control flow jumps over to the specific

interrupt service routine which first validates the senders number and then displays the information

field. Another very interesting and significant improvement would be to accommodate multiple

receiver MODEMS at the different positions in a geographical area carrying duplicate SIM cards.

With the help of principles of TDMA technique, we can choose to simulcast and /or broadcast

important notifications. After a display board receives the valid message through the MODEM and

displays it, it withdraws its identification from the network & synchronously another nearby

MODEM signs itself into the network and starts to receive the message. The message is broadcast

by the mobile switching center for a continuous time period during which as many possible display

board MODEMS catch the message and display it as per the constraint of validation. Multilingual

display can be another added variation of the project. The display boards are one of the single most

Page | 40

important media for information transfer to the maximum number of end users. This feature can be

added by programming the microcontroller to use different encoding decoding schemes in different

areas as per the local language. This will ensure the increase in the number of informed users.

Graphical display can also be considered as a long term but achievable and target able output. MMS

technology along with relatively high end microcontrollers to carry on the tasks of graphics

encoding and decoding along with a more expansive bank of usable memory can make this task a

walk in the park.

Page | 41

CHAPTER 7

REFERENCES

7.1 BOOKs

1. Muhammad Ali Mazidi, Janice G. Mazidi, Rolin D. McKinley The 8051 microcontroller

And embedded systems using assembly and C 2nd edition 01-Sep-2007, Pearson

Education India.

2. SMS and MMS Interworking In Mobile Networks Arnaud Henry-Labordere, Artech

House mobile communications 2004 Technology & Engineering.

3. Ayala, Kenneth J.(1996) The 8051 Microcontroller- Architecture, Programming and

Applications Delmar Publishers, Inc. India Reprint.

4. GSM telecommunication standards, June 2000 Second edition, European

Telecommunications Standards Institute.

5. M Samiullah, NS Qureshi,SMS Repository and Control System using GSM-SMS

Technology, European journal of scientific research, 2012.

6. D Dalwadi, N Trivedi and A Kasundra (2011), Article in Nation conference on recent

Trends in engineering and technology, INDIA

7.2 URLs

7. http://hktiit.ee.ust.hk/technology/TT_wireless.htm.

8. www.wikipedia.org

9. www.atmel.com

10. http://www.alldatasheet.com/view.jsp?Searchword=MC 8051

11. http://www.8052.com/tut8051

12. www.Engineergarage.com

BIO-DATA OF STUDENTS

SHARWAN KUMAR

I am pursuing Bachelor of Technology in Electronics and Communication Engineering from

Lovely Professional University, Punjab. My area of interest is Communication Engineering.

HEMANT KUMAR SINGH

I am pursuing Bachelor of Technology in Electronics and Communication Engineering from

Lovely Professional University, Punjab. My area of interest is Communication Engineering.

RAHUL KUMAR

I am pursuing Bachelor of Technology in Electronics and Communication Engineering from

Lovely Professional University, Punjab. My area of interest is Communication Engineering.

KOMAL KARAN

I am pursuing Bachelor of Technology in Electronics and Communication Engineering from

Lovely Professional University, Punjab. My area of interest is Communication Engineering.

BRIJESH YADAV

I am pursuing Bachelor of Technology in Electronics and Communication Engineering from

Lovely Professional University, Punjab. My area of interest is Communication Engineering.