main documentation

TRR ENGINEERING COLLEGE

A PROJECT REPORT ON

“ROUTE GUIDANCE FOR BLIND PEOPLE USING GSM AND GPS MODEMS”

Submitted in partial fulfillment of requirement for the award of degree of

BACHELOR OF TECHNOLOGY

IN

ELECTRONICS AND COMMUNICATION ENGINEERING

By

CH. RAVI SANKAR (08D15A0408)

A. KEERTHI PRIYA (07D11A0407)

P. SUSHMA (07D11A0454)

P. HIMAJA SREE (07D11A0497)

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING


(AFFILIATED TO J.N.T.U HYDERABAD)

Inole (V) Patancheru (M) Medak (Dist)

HYDERABAD

2007 - 2011

Page | 1ROUTE GUIDENCE FOR THE BLIND



(AFFILIATED TO J.N.T.U HYDERABAD)

Inole (V) Patancheru (M) Medak (Dist)

HYDERABAD

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

CERTIFICATE

This is to certify that the project work entitled “ROUTE

GUIDANCE FOR BLIND PEOPLE USING GSM AND GPS

MODEMS” was being submitted by CH RAVI SANKAR

(08D15A0408), A KEERTHI PRIYA (07D11A0407), P SUSHMA

(07D11A0454) P HIMAJA SREE (07D11A0497). In partial fulfillment

of the requirement for the award of degree of bachelor of Technology in

Electronics and Communication Engineering from Jawaharlal Nehru

Technology University – Hyderabad. The results embodied in this project

have not been submitted to any other University or Institution of the

award of any Degree or Diploma.

Prof. C ASHOK KUMAR

Internal Supervisor & Head of the Department.



YOUR PROJECT SURE – CERTIFICATE COMES IN

THIS PAGE



ACKNOWLEDGEMENT

Our heartfelt thanks to our principal Prof. Dr. ANIL KUMAR for having

provided us the necessary infrastructure required for the successful completion of our

project.

We acknowledge our gratitude to Prof. C. ASHOK KUMAR, Head of the

Department, Electronics and Communication Engineering, for the constant guidance

and encouragement.

We thank our internal guide Prof. C. ASHOK KUMAR, for his help and

invigorating suggestions extended with immense care throughout our work.

Our sincere thanks to all of the teaching and non – teaching staff for extending

their support and cooperation for the completion of our project.

CH. RAVI SANKAR (08D15A0408)

A. KEERTHI (07D11A0407)

P. HIMAJA SREE (07D11A0497)

P. SUSHMA (07D11A0454)



CONTENTS

ABSTRACT

List of figures

List of tables

CHAPTER – I

1.1 INTRODUCTION 1

1.2 HISTORY 1

1.3 MOTIVATION 2

1.4 OBJECTIVE 3

1.5 DESIGN POSSIBILITIES 3

1.6 ORGANISATION OF DOCUMENT 4

1.7 BLOCK DIAGRAM 5

CHAPTER – II: MAJOR COMPONENTS 6

2.1 HARDWARE PARTS

2.1.1 MICROCONTROLLER 7

2.1.2 GPS 13

2.1.3 GSM 26

2.1.4 LCD 36

2.1.5 MAX232 41



2.1.6 BUFFER IC (74LS244) 44

2.1.7 POWER SUPPLY 47

2.1.8 INPUT KEYPADS 55

2.1.9BUZZER 56

2.1.10 SERIAL COMMUNICATION (RS 232) 56

2.1.11UART 58

CHAPTER – III:

3.1 CIRCUIT DIAGRAM 68

3.2 INITIAL CIRCUITARY 70

3.3 FINAL CIRCUITARY 71

CHAPTER 4: ADDITIONAL FEATURES:

4.1 INTRODUCTION 72

4.2 COMPONENTS UTILIZED 72

4.2.1 TWO 7555 TIMERIC’S 72

4.2.2 PHOTODIODE 74

4.2.3 INFRARED LED 75

4.2.4 TRANSISTOR BC54 77

CHAPTER – V

CODING



CHAPTER – VI

6.1 ADVANTAGES 79

6.2 LIMITATIONS OF EXISTING DEVICES 79

6.3 APPLICATIONS 80

6.4 FUTURE SCOPE 80

6.5 ACTUAL WAY OF ACCESING THE MODEL 81

CHAPTER – VII

RESULT 82

CONCLUSION 83

REFERENCES 84



ABSTRACT

Based on the investigation about daily activity characteristics and modes

of the blind, the study found that the main difficulties encountered in a trip

of the blind included walking on the road, finding way, taking a bus and

looking for usual life - arena. After analyzing the research and application of

actual blind navigation technologies, to solve the demands and difficulties in

the blind trip, the study presents a blind navigation system based on Radio

Frequency Identification through wireless and mobile communications

technologies. The system consists of GPS, GSM which can be integrated into

the blind cane, mobile phone, Call Center and center information servers. Using

this system, the blind are able to know their location, condition of roads,

vicinity buildings, and inquire about the optimal routes to their destination and

available vehicles. The technologies used in this navigation system are mature,

which ensures the system is practical, universal and with perfect function.

One of the major goals for blind and visually impaired people is independent

mobility. In this paper an electronic travel aid for blind pedestrians is then described.

It involves a sensor in the integrated cane to detect the movement of the user when he

walks and a microcontroller with synthetic speech output. This aid is a portable, self

contained system that will allow blind and visually impaired individuals to travel

through familiar and unfamiliar environments without the assistance of guides. In

addition, it provides information to the user about urban walking routes using spoken

words to indicate what decisions to make.



LIST OF FIGURES:

1. GLOBALLY BLIND PEOPLE HISTORY

2. TELECOMMUNICATION NETWORK

3. SPACE SEGMENT

4. SYSTEM SEGMENTATION

5. A GPS SATELLITE

6. USER SEGMENT

7. NAVIGATIONAL SIGNALS

8. THREE DIMENSIONAL COORDINATE SYSTEM

9. GPS APPLICATIONS IN CIVILIAN

10. GSM NETWORK

11. GSM NETWORK AREAS

12.PIN DIAGRAM OF 16*1 LCD LINES

13. MAX 232 IC

14. CIRCUIT CONNECTIONS OF MAX232

15.CONNECTION DIAGRAM OF BUFFER IC

16. CIRCUIT DIAGRAM FOR POWER SUPPLY

17. IDEAL STEP DOWN TRANSFORMER SHOWING MAGNETIC FLUX IN

THE CORE

18. IDEAL TRANSFORMER



19. BRIDGE RECTIFIER CIRCUIT

20. AC HALF WAVE, FULLWAVE RECTIFIED SIGNALS

21. DIODE BRIDGE SMOOTHING

22. DB9 PIN DIAGRAM

23. UART PIN DIAGRAMS

24. PHOTODIODE MODEL

25. IR LED OPERATION DIAGRAM

26. IR LED MODEL

27. TRANSISTOR BC547 & ITS SYMBOL REPRESENTATION

LIST OF TABLES:

1 TCON REGISTES

2. TMOD REGISTERS

3. ADDRESS LOCATIONS OF16*1 LCD LINES

4. FUNCTION TABLE

5. RECOMMENDED OPERATING CONDITIONS



CHAPTER – I

1.1 INTRODUCTION

People who are blind or visually impaired have choices when it comes to

travelling. At any given time, they can travel using a human guide, holding onto

someone's arm; use a long, white cane to identify and avoid obstacles; use a dog

guide, use special optical or electronic aids, or use no additional aid. The choice of

tools depends on the extent and nature of visual impairment, personal preference,

lighting, and familiarity with the area. In order to travel independently, people with

visual impairments use whatever vision they have, auditory and tactual clues, and

other information they know about an area to keep track of their locations and make

travel decisions.

In this paper, the proposed electronic travel aid involves a

microcontroller with speech output. It is a self contained portable

electronic unit. It can supply the blind person with assistance about

walking routes by using a speech synthesizer to point out what

decisions to make. In addition, the software permits a blind person

to explore the electronic map as well as planning the optimum route

to the desired destination.

1.2 HISTORY:

Simple Electronic Travel Aids have been in development since 1897[BRA,

85]. Real and more complex developments occurred after the Second World War and

through the 1950s and 60s [HEY, 83]. With the advent of the possibilities of remote

sensing in the form of ultrasound and radar more research effort was directed at the

problems of remote sensing of the environment for visually impaired people.

Advances in electronics and circuit miniaturization also aided the development of

these devices into portable mobility machines and a number of devices using these



technologies were developed such as the ‘Mowat Sensor’ [KAY, 84], and the ‘Sona’

[KEL, 84].

Through the 1960s and 70s obstacle detection devices continued to be

developed using a variety of sensing methods, notably lasers. However advances in

the pre-planning of routes were also taking place and with the advent of ‘capsule

paper’ (which expands when heated) tactile maps could be produced more easily than

previously existing methods. Later in the 1980s and 1990s further research allowed a

form of tactile map [JAC, 94] that talked to be developed. Recently through the early

1990s the focus has switched from mobility and obstacle detection to orientation and

location [KAW, 00]-[LOO, 98]. These systems, called ‘Audible Signs’[BEN, 95],

‘Sound Buoys’[BLE, 97] etc, transmit some form of remote signal once a user gets

into range of the device, which then delivers an audible message, either as a tone or

speech. While these systems do solve some problems and despite being relatively

inexpensive, it can be expensive to place these signs extensively in an environment.

FIG 1.1: GLOBALLY BLIND PEOPE IN EARTH

1.3 MOTIVATION:

Imagine walking into an unfamiliar airport. The places we have to search for,

airline ticket counter, security check-in, boarding gate, are difficult to and even with



signs. Imagine how much of a challenge this would be if you cannot even see the

signs!

Many medical and academic buildings lack even this kind of navigation

assistance. Challenging for a sighted person, the task of ending a way in such a

building for an unassisted person with visual impairment becomes nearly impossible.

Outdoor mobility can present more potential dangers to blind travelers

because obstacles and Hazards such as motor vehicles and dangerous terrain can be

life-threatening.

Navigation tends to be more difficult indoors because the environment is so

homogeneous. Rather than searching for unique features, a traveler needs to count

doorways and intersections or find some other way to distinguish between largely

identical features such as offices or doorways.

Thus the implementation of this design helps motivates the visually impaired

feel independent and confident in their lives and also brings up their spirit in

succeeding in every field possible without making their visually impairedness as their

major contempt in life and this design helps people find out the route anywhere in the

world in the most easiest way.

1.4 OBJECTIVE:

The main goal of the project is to provide cost - effective way to

allow buildings to support blind people.

Audio route announcement for the blind hopes to allow visually

impaired users to simply press a button, speak the desired

destination, and be guided there with the use of the audio

instructions.

The system hopes to provide a portable unit that can be easily

carried and operated by visually impaired user. It could be easily

incorporated into walking cane.



1.5 DESIGN POSSIBILITIES:

Many different design possibilities were explored during research.

Wireless Sensor Networks – Due to the high amount of sensors required for

large buildings, this may be impractical, especially when user direction must

be tracked. Programming would be much more complex.

RSSI Techniques – This can be effective at finding distances base on signal

strength but is also affected by the direction problem.

RFID – Seems to provide the most cost effective and simplest way to

determine direction using the technique that the team has developed. The

programming using this technique would also be less complex

1.6 ORGANISATION OF DOCUMENTATION:

In this project documentation we have initially put the

definition and objective of the project as well as the design of the

project which is followed by the implementation and coding phase.

Finally the project has been concluded successfully and also the

future enhancements of the project were given in this

documentation



1.7 BLOCK DIAGRAM:

TEXT

FORMAT

IN THE FORM OF TEXT

AUTOMATIC CALL

FORWARDING

AUDIO FORMAT


GPS

MODULE

GSM

MODULE

KEYPAD CONSISTING OF SWITCHES

89S52

MICRO-

CONTROLLER

MOBILE PHONE

OF BLIND PERSON

LCD

(LIQUID CRYSTAL DISPAY)

SERVICE CENTRE


OUTPUT

FIGURE 1.2: BLOCK DIAGRAM

CHAPTER – II

MAJOR COMPONENTS

2.1 MICROCONTROLLER:

A) DESCRIPTION OF MICROCONTROLLER 89S52:

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

controller with 8Kbytes of in-system programmable Flash memory. The device is

manufactured Using Atmel’s high-density nonvolatile memory technology and is

compatible with the industry-standard 80C51 micro controller. 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

one monolithic chip; the Atmel AT89S52 is a powerful micro controller, which

provides a highly flexible and cost-effective solution to many embedded control

applications.

B) FEATURES OF AT89S52:

Compatible with MCS-51 Products

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

256K Internal RAM

32 Programmable I/O Lines

3 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 of flag

C) PIN CONFIGURATION

FIGURE 2.1: PIN CONFIGURATION OF AT89S52



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, full duplex serial port, on-chip oscillator, and clock

circuitry. In addition, the AT89S52 is designed with static logic for penetration

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.

D) SPECIAL FUNCTION REGISTER (SFR) MEMORY:

Special Function Registers (SFR s) are areas of memory that control specific

functionality of the 8051 processor. For example, four SFRs permit access to the

8051’s 32 input/output lines. Another SFR allows the user to set the serial baud

rate, control and access timers, and configure the 8051’s interrupt system.

E) THE ACCUMULATOR:

The Accumulator, as its name suggests is used as a general register to accumulate

the results of a large number of instructions. It can hold 8-bit (1-byte) value and

is the most versatile register.

F) THE “R” REGISTERS:

The “R” registers are a set of eight registers that are named R0, R1etc up to R7.

These registers are used as auxiliary registers in many operations.

The “B” registers: The “B” register is very similar to the accumulator in the

sense that it may hold an 8-bit (1-byte) value. Two only uses the “B” register

8051 instructions: MUL AB and DIV AB.

The Data Pointer: The Data pointer (DPTR) is the 8051’s only user

accessible 16-bit (2Bytes) register. The accumulator, “R” registers are all 1-Byte

values. DPTR, as the name suggests, is used to point to data. It is used by a

number of commands, which allow the 8051 to access external memory.



G) THE PROGRAM COUNTER AND STACK POINTER:

The program counter (PC) is a 2-byte address, which tells the 8051 where the next

instruction to execute is found in memory. The stack pointer like all registers except

DPTR and PC may hold an 8-bit (1Byte)value.

H) TYPES OF MEMORY:

The 8051/8052 has three very general types of memory. To effectively program the

8051/8052 it is necessary to have a basic understanding of these memory types.

The memory types are illustrated in the following graphic. They are: On-Chip

Memory, External Code Memory, and External RAM.

On-Chip Memory refers to any memory (Code, RAM, or other) that physically exists

on the microcontroller itself. On-chip memory can be of several types, but we'll get

into that shortly.

External Code Memory is code (or program) memory that resides off-chip. This is

often in the form of an external EPROM.

External RAM is RAM memory that resides off-chip. This is often in the form of

standard static RAM or flash RAM.

I) TCON REGISTER:

TABLE 2.1: TIMER/COUNTER CONTROL REGISTER



J) TMOD REGISTER:



TABLE 2.2: TIMER/COUNTER 0 AND 1 MODES

2.1.2 GLOBAL POSITIONING SYSTEMPage | 21

ROUTE GUIDENCE FOR THE BLIND


a) INTRODUCTION:

The Global Positioning System (GPS) is the only fully functional Global

Navigation Satellite System (GNSS). The GPS uses a constellation of between 24 and

32 Medium Earth Orbit satellites that transmit precise microwave signals, which

enable GPS receivers to determine their location, speed,. GPS was developed by the

United States Department of Defense. Its official name is NAVSTAR-GPS.

Although NAVSTAR-GPS is not an acronym, a few acronyms have been created for

it. The GPS satellite constellation is managed by the United States Air Force 50th

Space Wing.

Global Positioning System is an earth-orbiting-satellite based system that

provides signals available anywhere on or above the earth, twenty-four hours a day,

which can be used to determine precise time and the position of a GPS receiver in

three dimensions. GPS is increasingly used as an input for Geographic Information

Systems particularly for precise positioning of geospatial data and the collection of

data in the field. Precise positioning is possible using GPS receivers at reference

locations providing corrections and relative positioning data for remote receivers.

Time and frequency dissemination, based on the precise clocks on board the

SVs and controlled by the monitor stations, is another, use for GPS. Astronomical

observatories telecommunications facilities and laboratory standards can be set to

precise time signals or controlled to accurate frequencies by special purpose GPS

receivers.



FIGURE 2.1 GPS SETELLITE VIEW

FIGURE 2.2 GPS LONGITUDE & LATTITUDE INDICATOR

b) BASIC CONCEPT OF GPS OPERATION:

A GPS receiver calculates its position by carefully timing the signals sent by

the constellation of GPS satellites high above the Earth. Each satellite continually Page | 23


http://en.wikipedia.org/wiki/Image:GPS_Satellite_NASA_art-iif.jpg

http://en.wikipedia.org/wiki/Image:Magellan_GPS_Blazer12.jpg


transmits messages containing the time the message was sent, a precise orbit for the

satellite sending the message (the ephemeris), and the general system health and

rough orbits of all GPS satellites (the almanac). These signals travel at the speed of

light through outer space, and slightly slower through the atmosphere. The receiver

uses the arrival time of each message to measure the distance to each satellite, from

which it determines the position of the receiver (conceptually the intersection of

spheres - see trilateration ) The resulting coordinates are converted to more user-

friendly forms such as latitude and longitude, or location on a map, then displayed to

the user.

It might seem that three satellites would be enough to solve for a position,

since space has three dimensions. However, a three satellite solution requires the time

be known to a nanosecond or so, far better than any non-laboratory clock can provide.

Using four or more satellites allows the receiver to solve for time as well as

geographical position, eliminating the need for a super accurate clock. In other words,

the receiver uses four measurements to solve for four variables: x, y, z, and t. While

many GPS applications have no particular use for this (very accurate) time, it is used

in some GPS applications such as time transfer, and it is the only variable of interest

in some applications, such as traffic signal timing.

c) CORRECTING GPS CLOCK:

The method of calculating position for the case of no errors has been

explained. One of the most important errors is the error in the GPS receiver clock.

Because of the very large value of c, the speed of light, the estimated distances from

the GPS receiver to the satellites, the pseudo ranges, are very sensitive to errors in the

GPS receiver clock. This seems to suggest that an extremely accurate and expensive

clock is required for the GPS receiver to work. On the other hand,

manufacturers would like to make an inexpensive GPS receiver which can be mass

marketed. The manufacturers were thus faced with a difficult design problem. The

technique that solves this problem is based on the way sphere surfaces intersect in the

GPS problem.

It is likely the surfaces of the three spheres intersect since the circle of

intersection of the first two spheres is normally quite large and thus the third sphere Page | 24



surface is likely to intersect this large circle. It is very unlikely that the surface of the

sphere corresponding to the fourth satellite will intersect either of the two points of

intersection of the first three since any clock error could cause it to miss intersecting a

point. However the distance from the valid estimate of GPS receiver position to the

surface of the sphere corresponding to the fourth satellite can be used to compute a

clock correction. Let denote the distance from the valid estimate of GPS receiver

position to the fourth satellite and let denote the pseudo range of the fourth

satellite. Let . Note that is the distance from the computed GPS

receiver position to the surface of the sphere corresponding to the fourth satellite.

Thus the quotient, , provides an estimate of: (correct time) - (time

indicated by the receiver's on-board clock) and the GPS receiver clock can be

advanced if is positive or delayed if is negative.

d) SYSTEM SEGMENTATION:

The current GPS consists of three major segments. These are the space

segment (SS), a control segment (CS), and a user segment (US).

e) SPACE SEGMENT

FIGURE 2.3 GPS SPACE SEGMENT

A visual example of the GPS constellation in motion with the Earth rotating.

Notice how the number of satellites in view from a given point on the Earth's surface,

in this example at 45°N, changes with time.


http://en.wikipedia.org/wiki/Image:ConstellationGPS.gif


The space segment (SS) comprises the orbiting GPS satellites or Space

Vehicles (SV) in GPS parlance. The GPS design originally called for 24 SVs, eight

each in three circular orbital planes, but this was modified to six planes with four

satellites each.

FIGURE 2.4: SYSTEM SEGMENTATION



FIGURE 2.5: A GPS SATELLITE

f) CONTROL SEGMENT:

The flight paths of the satellites are tracked by US Air Force monitoring

stations in Hawaii, Kwajalein, Ascension Island, Diego Garcia, and Colorado Springs,

Colorado, along with monitor stations operated by the National Geospatial-

Intelligence Agency (NGA). The tracking information is sent to the Air Force Space

Command's master control station at Schreiber Air Force Base in Colorado Springs,

which is operated by the 2nd Space Operations Squadron (2 SOPS) of the United

States Air Force (USAF). Then 2 SOPS contacts each GPS satellite regularly with a

navigational update (using the ground antennas at Ascension Island, Diego Garcia,

Kwajalein, and Colorado Springs). These updates synchronize the atomic clocks on

board the satellites to within a few nanoseconds of each other, and adjust the

ephemeris of each satellite's internal orbital model. The updates are created by a

Kalman filter which uses inputs from the ground monitoring stations, space weather

information, and various other inputs.

Satellite maneuvers are not precise by GPS standards. So to change the orbit

of a satellite, the satellite must be marked 'unhealthy', so receivers will not use it in

their calculation. Then the maneuver can be carried out, and the resulting orbit

tracked from the ground. Then the new ephemeris is uploaded and the satellite

marked healthy again.



g) USER SEGMENT

FIGURE 2.6 RECEIVER SEGMENTS

PS receivers come in a variety of formats, from devices integrated into cars,

phones, and watches, to dedicated devices such as those shown here from

manufacturers Trimble, Garmin and Leica (left to right).

The user's GPS receiver is the user segment (US) of the GPS. In general, GPS

receivers are composed of an antenna, tuned to the frequencies transmitted by the

satellites, receiver-processors, and a highly-stable clock (often a crystal oscillator).

They may also include a display for providing location and speed information to the

user. A receiver is often described by its number of channels: this signifies how many

satellites it can monitor simultaneously. Originally limited to four or five, this has

progressively increased over the years so that, as of 2007, receivers typically have

between 12 and 20 channels.

h) THE COMMUNICATION LINK BUDGET ANALYSIS

The orbital planes are centered on the Earth, not rotating with respect to the

distant stars. The six planes have approximately 55° inclination (tilt relative to Earth's

equator) and are separated by 60° right ascension of the ascending node (angle along

the equator from a reference point to the orbit's intersection). The orbits are arranged

so that at least six satellites are always within line of sight from almost everywhere on

Earth's surface.


http://en.wikipedia.org/wiki/Image:GPS_Receivers.jpg


Orbiting at an altitude of approximately 20,200 kilometers (12,600 miles or

10,900 nautical miles; orbital radius of 26,600 km (16,500 mi or 14,400 NM)), each

SV makes two complete orbits each sidereal day. The ground track of each satellite

therefore repeats each (sidereal) day. This was very helpful during development, since

even with just four satellites, correct alignment means all four are visible from one

spot for a few hours each day. For military operations, the ground track repeat can be

used to ensure good coverage in combat zones.

As of March 2008, there are 31 actively broadcasting satellites in the GPS

constellation. The additional satellites improve the precision of GPS receiver

calculations by providing redundant measurements. With the increased number of

satellites, the constellation was changed to a non uniform arrangement. Such an

arrangement was shown to improve reliability and availability of the system, relative

to a uniform system, when multiple satellites fail. Some reports in 2008 indicated that

the 32nd satellite was causing difficulties for some GPS receivers.

i) NAVIGATIONAL SIGNALS:

FIGURE 2.7: NAVIGATIONAL SIGNAL


http://en.wikipedia.org/wiki/Image:GPS_signal_modulation_scheme.svg


j) GPS BROADCAST SIGNAL

Each GPS satellite continuously broadcasts a Navigation Message at 50 bit/s

giving the time-of-week, GPS week number and satellite health information (all

transmitted in the first part of the message), an ephemeris (transmitted in the second

part of the message) and an almanac (later part of the message). The messages are

sent in frames, each taking 30 seconds to transmit 1500 bits.The first 6 seconds of

every frame contains data describing the satellite clock and its relationship to GPS

time. The next 12 seconds contain the ephemeris data, giving the satellite's own

precise orbit. The ephemeris is updated every 2 hours and is generally valid for 4

hours, with provisions for updates every 6 hours or longer in non-nominal conditions.

The time needed to acquire the ephemeris is becoming a significant element of the

delay to first position fix, because, as the hardware becomes more capable, the time to

lock onto the satellite signals shrinks, but the ephemeris data requires 30 seconds

(worst case) before it is received, due to the low data transmission rate.

The almanac consists of coarse orbit and status information for each satellite

in the constellation, an ionosphere model, and information to relate GPS derived time

to Coordinated Universal Time (UTC). A new part of the almanac is received for the

last 12 seconds in each 30 second frame. Each frame contains 1/25th of the almanac,

so 12.5 minutes are required to receive the entire almanac from a single satellite. The

almanac serves several purposes. The first is to assist in the acquisition of satellites at

power-up by allowing the receiver to generate a list of visible satellites based on

stored position and time, while an ephemeris from each satellite is needed to compute

position fixes using that satellite. In older hardware, lack of an almanac in a new

receiver would cause long delays before providing a valid position, because the

search for each satellite was a slow process. Advances in hardware have made the

acquisition process much faster, so not having an almanac is no longer an issue. The

second purpose is for relating time derived from the GPS (called GPS time) to the

international time standard of UTC. Finally, the almanac allows a single frequency

receiver to correct for ionospheric error by using a global ionospheric model. The

corrections are not as accurate as augmentation systems like WAAS or dual frequency

receivers. However it is often better than no correction since ionospheric error is the

largest error source for a single frequency GPS receiver. An important thing to note



about navigation data is that each satellite transmits only its own ephemeris, but

transmits an almanac for all satellites.

Each satellite transmits its navigation message with at least two distinct spread

spectrum codes: the Coarse / Acquisition (C/A) code, which is freely available to the

public, and the Precise (P) code, which is usually encrypted and reserved for military

applications. The C/A code is a 1023 length Gold code at 1.023 million chips per

second so that it repeats every millisecond. As pointed out in a chip is essentially the

same thing as a bit and chips per second are the same as bits per second. The

justification for coming up with this new term, chip, is that in some cases a sequence

of bits is used as a type of Modulation and contains no information.

k) POSITION DETERMINATION:

Before providing a more mathematical description of position calculation, the

introductory material on these topics is reviewed. To describe the basic concept of

how a GPS receiver works, the errors are at first ignored. Using messages received

from four satellites, the GPS receiver is able to determine the satellite positions and

time sent. The x, y, and z components of position and the time sent are designated as

where the subscript i denotes which satellite and has the value 1, 2, 3,

or 4. Knowing the indicated time the message was received , the GPS receiver can

compute the indicated transit time, . of the message.

Assuming the message traveled at the speed of light, c, the distance traveled,

can be computed as . Knowing the distance from GPS receiver to a

satellite and the position of a satellite implies that the GPS receiver is on the surface

of a sphere centered at the position of a satellite. Thus we know that the indicated

position of the GPS receiver is at or near the intersection of the surfaces of four

spheres. In the ideal case of no errors, the GPS receiver will be at an intersection of

the surfaces of four spheres. The surfaces of two spheres if they intersect in more than

one point intersect in a circle. A figure, Two Sphere Surfaces Intersecting in a Circle,

is shown below depicting this which hopefully will aid the reader in visualizing this

intersection.



FIGURE 2.8: 3D COORDINATE SYSTEM

The article, trilateration, shows mathematically how the equation for a circle is

determined. A circle and sphere surface in most cases of practical interest intersects at

two points, although it is conceivable that they could intersect in 0 or 1 point. Another

figure, Surface of Sphere Intersecting a Circle (not disk) at Two Points, is shown

below to aid in visualizing this intersection. Again trilateration clearly show this

mathematically. The correct position of the GPS receiver is the one that is closest to

the fourth sphere. This paragraph has described the basic concept of GPS while

ignoring errors.

More than four satellites should be used, if available. This results in an over-

determined system of equations with no unique solution, which must be solved by

least-squares or a similar technique. If all visible satellites are used, the results are

always at least as good as using the four best, and usually better. Also the errors in

results can be estimated through the residuals. With each combination of four or more

satellites, a geometric dilution of precision (GDOP) vector can be calculated, based

on the relative sky positions of the satellites used. As more satellites are picked up,

pseudoranges from more combinations of four satellites can be processed to add more

estimates to the location and clock offset. The receiver then determines which

combinations to use and how to calculate the estimated position by determining the

weighted average of these positions and clock offsets. After the final location and

time are calculated, the location is expressed in a specific coordinate system such as



latitude and longitude, using the WGS 84 geodetic datum or a local system specific to

a country.

Finally, results from other positioning systems such as GLONASS or the upcoming

Galileo can be used in the fit, or used to double check the result. (By design, these

systems use the same bands; so much of the receiver circuitry can be shared, though

the decoding is different.

l) APPLICATIONS:

The Global Positioning System, while originally a military project is considered a

dual-use technology, meaning it has significant applications for both the military and

the civilian industry.

MILITARY:

The military applications of GPS span many purposes:

Navigation: GPS allows soldiers to find objectives in the dark or in unfamiliar

territory, and to coordinate the movement of troops and supplies. The GPS-

receivers commanders and soldiers use are respectively called the

Commanders Digital Assistant and the Soldier Digital Assistant.

Target tracking: Various military weapons systems use GPS to track potential

ground and air targets before they are flagged as hostile. These weapon systems

pass GPS co-ordinates of targets to precision-guided munitions to allow them

to engage the targets accurately. Military aircraft, particularly those used in air-

to-ground roles use GPS to find targets (for example, gun camera video from

AH-1 Cobras in Iraq show GPS co-ordinates that can be looked up in Google

Earth).

This antenna is mounted on the roof of a hut containing a scientific experiment

needing precise timing.

Many civilian applications benefit from GPS signals, using one or more of three

basic components of the GPS: absolute location, relative movement, and time

transfer.



The ability to determine the receiver's absolute location allows GPS receivers to

perform as a surveying tool or as an aid to navigation. The capacity to determine

relative movement enables a receiver to calculate local velocity and orientation,

useful in vessels or observations of the Earth. Being able to synchronize clocks to

exacting standards enables time transfer, which is critical in large communication and

observation systems. An example is CDMA digital cellular. Each base station has a

GPS timing receiver to synchronize its spreading codes with other base stations to

facilitate inter-cell hand off and support hybrid GPS/CDMA positioning of mobiles

for emergency calls and other applications. Finally, GPS enables researchers to

explore the Earth environment including the atmosphere, ionosphere and gravity

field. GPS survey equipment has revolutionized tectonics by directly measuring the

motion of faults in earthquakes.

GPS tours are also an example of civilian use. The GPS is used to determine which

content to display. For instance, when approaching a monument it would tell you

about the monument.

m) GPS MODULE: Latitude and longitude are usually provided in the geodetic

datum on which GPS is based (WGS-84).

Receivers can often be set to convert to other user-required datums.

Receiver position is computed from the SV positions, the measured pseudo-

ranges, and a receiver position estimate.

Four satellites allow computation of three position dimensions and time.

Three satellites could be used determine three position dimensions with a perfect

receiver clock.

In practice this is rarely possible and three SVs are used to compute a two-

dimensional, horizontal fix (in latitude and longitude) given an assumed height.

This is often possible at sea or in altimeter equipped aircraft.

Five or more satellites can provide position, time and redundancy.



Twelve channel receivers allow continuous tracking of all available satellites,

including tracking of satellites with weak or occasionally obstructed signals.

2.1.3 GSM (GLOBAL SYSTEM FOR MOBILE

COMMUNICATION):

a)INTRODUCTION:

GSM (Global System for Mobile communications) is a cellular network, which

means that mobile phones connect to it by searching for cells in the immediate

vicinity. GSM networks operate in four different frequency ranges. Most GSM

networks operate in the 900 MHz or 1800 MHz bands. Some countries in the

Americas use the 850 MHz and 1900 MHz bands because the 900 and 1800 MHz

frequency bands were already allocated.

The rarer 400 and 450 MHz frequency bands are assigned in some countries, where

these frequencies were previously used for first-generation systems.

Time division multiplexing is used to allow eight full-rate or sixteen half-rate speech

channels per radio frequency channel. There are eight radio timeslots (giving eight

burst periods) grouped into what is called a TDMA frame. Half rate channels use

alternate frames in the same timeslot. The channel data rate is 270.833 kbit/s, and the

frame duration is 4.615 ms.

b) GSM ADVANTAGES:

GSM also pioneered a low-cost, to the network carrier, alternative to voice calls, the

Short t message service (SMS, also called "text messaging"), which is now supported

on other mobile standards as well. Another advantage is that the standard includes

one worldwide Emergency telephone number, 112. This makes it easier for

international travelers to connect to emergency services without knowing the local

emergency number.



c) GSM NETWORK:

GSM provides recommendations, not requirements. The GSM specifications define

the functions and interface requirements in detail but do not address the hardware.

The GSM network is divided into three major systems: the switching system (SS), the

base station system (BSS), and the operation and support system (OSS).

FIGURE 2.9: GSM NETWORK

The Switching System:

The switching system (SS) is responsible for performing call processing and

subscriber-related functions. The switching system includes the following functional

units. Page | 36



Home location register (HLR): The HLR is a database used for storage

and management of subscriptions. The HLR is considered the most important

database, as it stores permanent data about subscribers, including a

subscriber's service profile, location information, and activity status. When an

individual buys a subscription from one of the PCS operators, he or she is

registered in the HLR of that operator.

Mobile services switching center (MSC): The MSC performs the

telephony switching functions of the system. It controls calls to and from other

telephone and data systems. It also performs such functions as toll ticketing,

network interfacing, common channel signaling, and others.

Visitor location register (VLR): The VLR is a database that contains

temporary information about subscribers that is needed by the MSC in order

to service visiting subscribers. The VLR is always integrated with the MSC.

When a mobile station roams into a new MSC area, the VLR connected to that

MSC will request data about the mobile station from the HLR. Later, if the

mobile station makes a call, the VLR will have the information needed for call

setup without having to interrogate the HLR each time.

Authentication center (AUC): A unit called the AUC provides

authentication and encryption parameters that verify the user's identity and

ensure the confidentiality of each call. The AUC protects network operators

from different types of fraud found in today's cellular world.

Equipment identity register (EIR): The EIR is a database that

contains information about the identity of mobile equipment that prevents

calls from stolen, unauthorized, or defective mobile stations. The AUC and

EIR are implemented as stand-alone nodes or as a combined AUC/EIR node.

The Base Station System (BSS):

All radio-related functions are performed in the BSS, which consists of base station

controllers (BSCs) and the base transceiver stations (BTSs).



BSC: The BSC provides all the control functions and physical links between

the MSC and BTS. It is a high-capacity switch that provides functions such as

handover, cell configuration data, and control of radio frequency (RF) power

levels in base transceiver stations. A number of BSCs are served by an MSC.

BTS: The BTS handles the radio interface to the mobile station. The BTS is

the radio equipment (transceivers and antennas) needed to service each cell in

the network. A group of BTSs are controlled by a BSC.

The Operation and Support System

The operations and maintenance center (OMC) is connected to all equipment in the

switching system and to the BSC. The implementation of OMC is called the operation

and support system (OSS). The OSS is the functional entity from which the network

operator monitors and controls the system. The purpose of OSS is to offer the

customer cost-effective support for centralized, regional and local operational and

maintenance activities that are required for a GSM network. An important function of

OSS is to provide a network overview and support the maintenance activities of

different operation and maintenance organizations.

Additional Functional Elements

Message center (MXE): The MXE is a node that provides integrated

voice, fax, and data messaging. Specifically, the MXE handles short message

service, cell broadcast, voice mail, fax mail, e-mail, and notification.

Mobile service node (MSN): The MSN is the node that handles the

mobile intelligent network (IN) services.

Gateway mobile services switching center (GMSC): A gateway is

a node used to interconnect two networks. The gateway is often implemented

in an MSC. The MSC is then referred to as the GMSC.

GSM inter-working unit (GIWU): The GIWU consists of both

hardware and software that provides an interface to various networks for data

communications. Through the GIWU, users can alternate between speech and



data during the same call. The GIWU hardware equipment is physically

located at the MSC/VLR.

d) GSM NETWORK AREAS:

The GSM network is made up of geographic areas. As shown in bellow figure, these

areas include cells, location areas (LAs), MSC/VLR service areas, and public land

mobile network (PLMN) areas.

FIGURE 2.10: GSM NETWORK

Location Areas:

The cell is the area given radio coverage by one base transceiver station. The GSM

network identifies each cell via the cell global identity (CGI) number assigned to each

cell. The location area is a group of cells. It is the area in which the subscriber is

paged. Each LA is served by one or more base station controllers, yet only by a single

MSC Each LA is assigned a location area identity (LAI) number.

MSC/VLR service areas:

An MSC/VLR service area represents the part of the GSM network that is covered by

one MSC and which is reachable, as it is registered in the VLR of the MSC.



PLMN service areas:

The PLMN service area is an area served by one network operator.

e) GSM SPECIFICATIONS:

Specifications for different personal communication services (PCS) systems vary

among the different PCS networks. Listed below is a description of the specifications

and characteristics for GSM.

Frequency band: The frequency range specified for GSM is 1,850 to 1,990

MHz (mobile station to base station).

Duplex distance: The duplex distance is 80 MHz. Duplex distance is the

distance between the uplink and downlink frequencies. A channel has two

frequencies, 80 MHz apart.

Channel separation: The separation between adjacent carrier frequencies. In

GSM, this is 200 kHz.

Modulation: Modulation is the process of sending a signal by changing the

characteristics of a carrier frequency. This is done in GSM via Gaussian

minimum shift keying (GMSK).

Transmission rate: GSM is a digital system with an over-the-air bit rate of

270 kbps.

f) GSM SUBSCRIBERS SERVICE: Dual-tone multi frequency (DTMF): DTMF

is a tone signaling scheme often used for various control purposes via the telephone

network, such as remote control of an answering machine. GSM supports full-

originating DTMF.

Facsimile group III—GSM supports CCITT Group 3 facsimile. As standard fax

machines are designed to be connected to a telephone using analog signals, a special



fax converter connected to the exchange is used in the GSM system. This enables a

GSM–connected fax to communicate with any analog fax in the network.

Short message services: A convenient facility of the GSM network is the short

message service. A message consisting of a maximum of 160 alphanumeric characters

can be sent to or from a mobile station. This service can be viewed as an advanced

form of alphanumeric paging with a number of advantages. If the subscriber's mobile

unit is powered off or has left the coverage area, the message is stored and offered

back to the subscriber when the mobile is powered on or has reentered the coverage

area of the network. This function ensures that the message will be received.

Cell broadcast: A variation of the short message service is the cell broadcast

facility. A message of a maximum of 93 characters can be broadcast to all mobile

subscribers in a certain geographic area. Typical applications include traffic

congestion warnings and reports on accidents.

Voice mail: This service is actually an answering machine within the network,

which is controlled by the subscriber. Calls can be forwarded to the subscriber's

voice-mail box and the subscriber checks for messages via a personal security code.

Fax mail: With this service, the subscriber can receive fax messages at any fax

machine. The messages are stored in a service center from which they can be

retrieved by the subscriber via a personal security code to the desired fax number

g) SUPPLEMENTARY SERVICES:

GSM supports a comprehensive set of supplementary services that can complement

and support both telephony and data services.

Call forwarding: This service gives the subscriber the ability to forward

incoming calls to another number if the called mobile unit is not reachable, if it is

busy, if there is no reply, or if call forwarding is allowed unconditionally.

Barring of outgoing calls: This service makes it possible for a mobile subscriber

to prevent all outgoing calls.



Barring of incoming calls: This function allows the subscriber to prevent

incoming calls. The following two conditions for incoming call barring exist: baring

of all incoming calls and barring of incoming calls when roaming outside the home

PLMN.

Advice of charge (AoC): The AoC service provides the mobile subscriber with

an estimate of the call charges. There are two types of AoC information: one that

provides the subscriber with an estimate of the bill and one that can be used for

immediate charging purposes. AoC for data calls is provided on the basis of time

measurements.

Call hold: This service enables the subscriber to interrupt an ongoing call and then

subsequently reestablish the call. The call hold service is only applicable to normal

telephony.

Call waiting: This service enables the mobile subscriber to be notified of an

incoming call during a conversation. The subscriber can answer, reject, or ignore the

incoming call. Call waiting is applicable to all GSM telecommunications services

using a circuit-switched connection.

Multiparty service: The multiparty service enables a mobile subscriber to

establish a multiparty conversation—that is, a simultaneous conversation between

three and six subscribers. This service is only applicable to normal telephony.

Calling line identification presentation/restriction: These services supply

the called party with the integrated services digital network (ISDN) number of the

calling party. The restriction service enables the calling party to restrict the

presentation. The restriction overrides the presentation.

Closed user groups (CUGs): CUGs are generally comparable to a PBX. They

are a group of subscribers who are capable of only calling themselves and certain

numbers

h) MAIN AT COMMANDS:



"AT command set for GSM Mobile Equipment” describes the Main AT

commands to communicate via a serial interface with the GSM subsystem of the

phone.

AT commands are instructions used to control a modem. AT is the abbreviation of

Attention. Every command line starts with "AT" or "at". That's why modem

commands are called AT commands. Many of the commands that are used to control

wired dial-up modems, such as ATD (Dial), ATA (Answer), ATH (Hook control) and

ATO (Return to online data state), are also supported by GSM/GPRS modems and

mobile phones. Besides this common AT command set, GSM/GPRS modems and

mobile phones support an AT command set that is specific to the GSM technology,

which includes SMS-related commands like AT+CMGS (Send SMS message),

AT+CMSS (Send SMS message from storage), AT+CMGL (List SMS messages) and

AT+CMGR (Read SMS messages).

Note that the starting "AT" is the prefix that informs the modem about the start of a

command line. It is not part of the AT command name. For example, D is the actual

AT command name in ATD and +CMGS is the actual AT command name in

AT+CMGS. However, some books and web sites use them interchangeably as the

name of an AT command.

Here are some of the tasks that can be done using AT commands with a GSM/GPRS

modem or mobile phone:

Get basic information about the mobile phone or GSM/GPRS modem. For

example, name of manufacturer (AT+CGMI), model number (AT+CGMM),

IMEI number (International Mobile Equipment Identity) (AT+CGSN) and

software version (AT+CGMR).

Get basic information about the subscriber. For example, MSISDN

(AT+CNUM) and IMSI number (International Mobile Subscriber Identity)

(AT+CIMI).

Get the current status of the mobile phone or GSM/GPRS modem. For

example, mobile phone activity status (AT+CPAS), mobile network



registration status (AT+CREG), radio signal strength (AT+CSQ), battery

charge level and battery charging status (AT+CBC).

Establish a data connection or voice connection to a remote modem (ATD,

ATA, etc).

Send and receive fax (ATD, ATA, AT+F*).

Send (AT+CMGS, AT+CMSS), read (AT+CMGR, AT+CMGL), write

(AT+CMGW) or delete (AT+CMGD) SMS messages and obtain notifications

of newly received SMS messages (AT+CNMI).

Read (AT+CPBR), write (AT+CPBW) or search (AT+CPBF) phonebook

entries.

Perform security-related tasks, such as opening or closing facility locks

(AT+CLCK), checking whether a facility is locked (AT+CLCK) and changing

passwords (AT+CPWD).

(Facility lock examples: SIM lock [a password must be given to the SIM card

every time the mobile phone is switched on] and PH-SIM lock [a certain SIM

card is associated with the mobile phone. To use other SIM cards with the

mobile phone, a password must be entered.])

Control the presentation of result codes / error messages of AT commands.

For example, you can control whether to enable certain error messages

(AT+CMEE) and whether error messages should be displayed in numeric

format or verbose format (AT+CMEE=1 or AT+CMEE=2).



2.1.4 LCD (LIQUID CRYSTAL DISPLAY:

a) INTRODUCTION:

A liquid crystal display (LCD) is a thin, flat display device made up of any

number of color or monochrome pixels arrayed in front of a light source or reflector.

Each pixel consists of a column of liquid crystal molecules suspended between two

transparent electrodes, and two polarizing filters, the axes of polarity of which are

perpendicular to each other. Without the liquid crystals between them, light passing

through one would be blocked by the other. The liquid crystal twists the polarization

of light entering one filter to allow it to pass through the other.

A program must interact with the outside world using input and output devices

that communicate directly with a human being. One of the most common devices

attached to an controller is an LCD display. Some of the most common LCDs

connected to the controllers are 16X1, 16x2 and 20x2 displays. This means 16

characters per line by 1 line 16 characters per line by 2 lines and 20 characters per

line by 2 lines, respectively.



Many microcontroller devices use 'smart LCD' displays to output visual

information. LCD displays designed around LCD NT-C1611 module, are

inexpensive, easy to use, and it is even possible to produce a readout using the 5X7

dots plus cursor of the display. They have a standard ASCII set of characters and

mathematical symbols. For an 8-bit data bus, the display requires a +5V supply plus

10 I/O lines (RS RW D7 D6 D5 D4 D3 D2 D1 D0


available. Line lengths of

8, 16,

20, 24,

32 and

40

charact

ers are

all

standar

d, in

one,

two


b) FEATURES:

(1) Interface with either 4-bit or 8-bit microprocessor.

(2) Display data RAM

(3) 80x8 bits (80 characters).

(4) Character generator ROM

(5). 160 different 5 7 dot-matrix character patterns.

(6). Character generator RAM

(7) 8 different user programmed 5 7 dot-matrix patterns.

(8).Display data RAM and character generator RAM may be

Accessed by the microprocessor.

(9) Numerous instructions

(10) .Clear Display, Cursor Home, Display ON/OFF, Cursor

ON/OFF,

Blink Character, Cursor Shift, Display Shift.

(11). Built-in reset circuit is triggered at power ON.

(12). Built-in oscillator.

Data can be placed at any location on the LCD. For 16×1 LCD, the

address locations are:

TABLE 2.3: : ADDRESS LOCATIONS FOR A 1X16 LINE LCD



c) PIN DESCRIPTION:

Most LCDs with 1 controller has 14 Pins and LCDs with 2 controller has 16

Pins (two pins are extra in both for back-light LED connections).

FIGURE 2.11: PIN DIAGRAM OF 1X16 LINES LCD

TABLE 2.4 PIN DETAILS 1X16 LINES LCD

d) CONTROL LINES:

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 make sure this line is low (0)

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 high (1) and wait for the minimum amount

of time required by the LCD datasheet (this varies from LCD to LCD), and end by

bringing it low (0) again.

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), 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.

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.

Logic status on control lines:

• E - 0 Access to LCD disabled

- 1 Access to LCD enabled

• R/W - 0 Writing data to LCD

- 1 Reading data from LCD

• RS - 0 Instructions

- 1 Character



Writing data to the LCD:

1) Set R/W bit to low

2) Set RS bit to logic 0 or 1 (instruction or character)

3) Set data to data lines (if it is writing)

4) Set E line to high

5) Set E line to low

Read data from data lines (if it is reading)on LCD:

1) Set R/W bit to high

2) Set RS bit to logic 0 or 1 (instruction or character)

3) Set data to data lines (if it is writing)

4) Set E line to high

5) Set E line to low

Entering Text:

First, a little tip: it is manually a lot easier to enter characters and commands in

hexadecimal rather than binary (although, of course, you will need to translate

commands from binary couple of sub-miniature hexadecimal rotary switches is a

simple matter, although a little bit into hex so that you know which bits you are

setting). Replacing the d.i.l. switch pack with a of re-wiring is necessary.

The switches must be the type where On = 0, so that when they are turned to the zero

position, all four outputs are shorted to the common pin, and in position “F”, all four

outputs are open circuit.

All the available characters that are built into the module are shown in Table 3.

Studying the table, you will see that codes associated with the characters are quoted in

binary and hexadecimal, most significant bits (“left-hand” four bits) across the top, and

least significant bits (“right-hand” four bits) down the left.

Most of the characters conform to the ASCII standard, although the Japanese and



Greek characters (and a few other things) are obvious exceptions. Since these

intelligent modules were designed in the “Land of the Rising Sun,” it seems only fair

that their Katakana phonetic symbols should also be incorporated. The more extensive

Kanji character set, which the Japanese share with the Chinese, consisting of several

thousand different characters, is not included!

2.1.5 MAX 232 (RS232 SERIAL IC):

a) INTRODUCTION:

A standard serial interface for PC, RS232C, requires negative logic, i.e.,

logic 1 is -3V to -12V and logic 0 is +3V to +12V. To convert TTL logic, say, TxD

and RxD pins of the microcontroller thus need a converter chip. A MAX232 chip has

long been using in many microcontrollers boards. It is a dual RS232 receiver /

transmitter that meets all RS232 specifications while using only +5V power supply. It

has two onboard charge pump voltage converters which generate +10V to -10V

power supplies from a single 5V supply. It has four level translators, two of which are

RS232 transmitters that convert TTL/CMOS input levels into +9V RS232 outputs.

The other two level translators are RS232 receivers that convert RS232 input to 5V.

Typical MAX232 circuit is shown below.



FIG:MAX 232 IC

FIGURE 2.12 PIN CONFIGURATION OF MAX 232

b) FEATURES:

1. Operates With Single 5-V Power Supply

2. L in BiCMOSE Process Technology

3. Two Drivers and Two Receivers

4.±30-V Input Levels

5. Low Supply Current. 8 mA Typical

6 .Meets or Exceeds TIA/EIA-232-F and ITU

Recommendation V.28

7. Designed to be Interchangeable With

Maxim MAX232

8. Applications

TIA/EIA-232-F

Battery-Powered Systems

Terminals

Modems

Computers



c) CIRCUIT CONNECTIONS:

A standard serial interfacing for PC, RS232C, requires negative logic, i.e., logic '1' is

-3V to -12V and logic '0' is +3V to +12V. To convert a TTL logic, say, TxD and RxD

pins of the uC chips, thus need a converter chip. A MAX232 chip has long been using

in many uC boards. It provides 2-channel RS232C port and requires external 10uF

capacitors. Carefully check the polarity of capacitor when soldering the board. A

DS275 however, no need external capacitor and smaller. Either circuit can be used

without any problems.

FIGURE 2.13: CIRCUIT CONNECTION OF MAX 232



FIGURE 2.14: MAX 232 DISCRIPTIONAL DIAGRAM

2.1.6 BUFFER IC (74LS244):

a) GENERAL DESCRIPTION

These buffers/line drivers are designed to improve both the performance and PC

board density of 3-STATE buffers/ drivers employed as memory-address drivers,

clock drivers, and bus-oriented transmitters/receivers. Featuring 400 mV of

hysteresis at each low current PNP data line input, they provide improved noise

rejection and high fan-out outputs and can be used to drive terminated lines down to

133W.

b) FEATURES

3-STATE outputs drive bus lines directly

PNP inputs reduce DC loading on bus lines

Hysteresis at data inputs improves noise margins



Typical IOL (sink current) 24 mA

Typical IOH (source current) -15 mA

Typical propagation delay times

Inverting 10.5 ns

Non inverting 12 ns

Typical enable/disable time 18 ns

Typical power dissipation (enabled)

Inverting 130 m Non inverting 135 m W

c) CONNECTION DIAGRAM:

FIGURE 2.15: CIRCUIT CONNECTION OF 74LS244

d) FUNCTION TABLE:



TABLE 2.5: FUNCTIONAL TABLE OF 74LS244

I NPUT OUTPUT

G A Y

L L L

L H Z

H X Z

L = LOW Logic Level;

H = HIGH Logic Level

Z = High Impedance

X = Either LOW or HIGH Logic Level;

d) ABSOLUTE MAXIMUM RATINGS

Supply Voltage 7V

Input Voltage 7V

Operating Free Air Temperature Range 0°C to +70°C

Storage Temperature Range -65°C to +150°C

Note 1: The “Absolute Maximum Ratings” are those values beyond which the safety of the device

cannot be guaranteed. The device should not be operated at these limits. The parametric values defined

in the Electrical Characteristics tables are not guaranteed at the absolute maximum ration..The

“Recommended Operating Conditions” table will define the conditions for actual device operation.

e) RECOMMENDED OPERATING CONDITIONS

TABLE 2.6 RECOMMENDED OPERATING CONDITIONS OF 74LS244

SYMBOL PARAMETER MIN NOM MAX UNITS



VCC Supply Voltage 4.75 5 5.25 V

VIH HIGH Level Input

Voltage

V

VIL LOW Level Input

Voltage

0.8 V

IOH HIGH Level

Output Current

-15 mA

IOL LOW Level

Output Current

24 mA

TA Free Air

Operating

Temperature

0 70 °C

2.1.7 POWER SUPPLY:

a) INTRODUCTION:

Power supply is a reference to a source of electrical power. A device or

system that supplies electrical or other types of energy to an output load or group of

loads is called a power supply unit or PSU. The term is most commonly applied to

electrical energy supplies, less often to mechanical ones, and rarely to others

This power supply section is required to convert AC signal to DC signal and

also to reduce the amplitude of the signal. The available voltage signal from the mains

is 230V/50Hz which is an AC voltage, but the required is DC voltage(no frequency)

with the amplitude of +5V and +12V for various applications.

In this section we have Transformer, Bridge rectifier, are connected serially

and voltage regulators for +5V and +12V (7805 and 7812) via a capacitor (1000µF)

in parallel are connected parallel as shown in the circuit diagram below. Each voltage

regulator output is again is connected to the capacitors of values (100µF, 10µF, 1 µF,



0.1 µF) are connected parallel through which the corresponding output(+5V or +12V)

are taken into consideration.

b) CIRCUIT DIAGRAM:

FIGURE 2.16: CIRCUIT DIAGRAM OF POWER SUPPLY

d) CIRCUIT EXPLANATION:

TRANSFORMER:

A transformer is a device that transfers electrical energy from one circuit to another

through inductively coupled electrical conductors. A changing current in the first

circuit (the primary) creates a changing magnetic field; in turn, this magnetic field

induces a changing voltage in the second circuit (the secondary). By adding a load to

the secondary circuit, one can make current flow in the transformer, thus transferring

energy from one circuit to the other.

The secondary induced voltage VS, of an ideal transformer, is scaled from the primary

VP by a factor equal to the ratio of the number of turns of wire in their respective

windings:

1) BASIC PRINCIPLE:Page | 58



The transformer is based on two principles: firstly, that an electric current can

produce a magnetic field (electromagnetism) and secondly that a changing magnetic

field within a coil of wire induces a voltage across the ends of the coil

(electromagnetic induction). By changing the current in the primary coil, it changes

the strength of its magnetic field; since the changing magnetic field extends into the

secondary coil, a voltage is induced across the secondary.

A simplified transformer design is shown below. A current passing through the

primary coil creates a magnetic field. The primary and secondary coils are wrapped

around a core of very high magnetic permeability, such as iron; this ensures that most

of the magnetic field lines produced by the primary current are within the iron and

pass through the secondary coil as well as the primary coil.

Figure 2.17: An ideal step-down transformer showing magnetic flux in the core

2) INDUCTION LAW:

The voltage induced across the secondary coil may be calculated from Faraday's law

of induction, which states that:


http://en.wikipedia.org/wiki/Image:Transformer3d_col3.svg


Where VS is the instantaneous voltage, NS is the number of turns in the secondary coil

and Φ equals the magnetic flux through one turn of the coil. If the turns of the coil are

oriented perpendicular to the magnetic field lines, the flux is the product of the

magnetic field strength B and the area A through which it cuts. The area is constant,

being equal to the cross-sectional area of the transformer core, whereas the magnetic

field varies with time according to the excitation of the primary. Since the same

magnetic flux passes through both the primary and secondary coils in an ideal

transformer, the instantaneous voltage across the primary winding equals

Taking the ratio of the two equations for VS and VP gives the basic equation for

stepping up or stepping down the voltage

2) IDEAL POWER EQUATION:

If the secondary coil is attached to a load that allows current to flow, electrical power

is transmitted from the primary circuit to the secondary circuit. Ideally, the

transformer is perfectly efficient; all the incoming energy is transformed from the

primary circuit to the magnetic field and into the secondary circuit. If this condition is

met, the incoming electric power must equal the outgoing power.

P incoming = IPVP = P outgoing = ISVS

giving the ideal transformer equation



FIGURE 2.18: IDEAL TRANSFORMER

Pin-coming = IPVP = Pout-going = ISVS giving the ideal transformer equation

If the voltage is increased (stepped up) (VS > VP), then the current is decreased

(stepped down) (IS < IP) by the same factor. Transformers are efficient so this formula

is a reasonable approximation.

If the voltage is increased (stepped up) (VS > VP), then the current is decreased

(stepped down) (IS < IP) by the same factor. Transformers are efficient so this formula

is a reasonable approximation.

The impedance in one circuit is transformed by the square of the turns ratio. For

example, if an impedance ZS is attached across the terminals of the secondary coil, it

appears to the primary circuit to have an impedance of

This relationship is reciprocal, so that the impedance ZP of the primary circuit appears

to the secondary to be


http://en.wikipedia.org/wiki/Image:Transformer_under_load.svg


4) DETAILED OPERATION:

The simplified description above neglects several practical factors, in particular the

primary current required to establish a magnetic field in the core, and the contribution

to the field due to current in the secondary circuit.

Models of an ideal transformer typically assume a core of negligible reluctance with

two windings of zero resistance. When a voltage is applied to the primary winding, a

small current flows, driving flux around the magnetic circuit of the core. The current

required to create the flux is termed the magnetizing current; since the ideal core has

been assumed to have near-zero reluctance, the magnetizing current is negligible,

although still required to create the magnetic field.

The changing magnetic field induces an electromotive force (EMF) across each

winding. Since the ideal windings have no impedance, they have no associated

voltage drop, and so the voltages VP and VS measured at the terminals of the

transformer, are equal to the corresponding EMFs. The primary EMF, acting as it

does in opposition to the primary voltage, is sometimes termed the "back EMF". This

is due to Lenz's law which states that the induction of EMF would always be such that

it will oppose development of any such change in magnetic field.

e) BRIDGE RECTIFIER:

A diode bridge or bridge rectifier is an arrangement of four diodes in a bridge

configuration that provides the same polarity of output voltage for any polarity of

input voltage. When used in its most common application, for conversion of

alternating current (AC) input into direct current (DC) output, it is known as a bridge

rectifier. A bridge rectifier provides full-wave rectification from a two-wire AC input,

resulting in lower cost and weight as compared to a center-tapped transformer design,

but has two diode drops rather than one, thus exhibiting reduced efficiency over a

center-tapped design for the same output voltage.

1) BASIC OPERATION:



When the input connected at the left corner of the diamond is positive with respect to

the one connected at the right hand corner, current flows to the right along the upper

colored path to the output, and returns to the input supply via the lower one.

FIGURE 2.19: RECTIFIER CIRCUIT

When the right hand corner is positive relative to the left hand corner, current flows

along the upper colored path and returns to the supply via the lower colored path.

In each case, the upper right output remains positive with respect to the lower right

one. Since this is true whether the input is AC or DC, this circuit not only produces

DC power when supplied with AC power: it also can provide what is sometimes

called "reverse polarity protection". That is, it permits normal functioning when

batteries are installed backwards or DC input-power supply wiring "has its wires

crossed" (and protects the circuitry it powers against damage that might occur without

this circuit in place).

Prior to availability of integrated electronics, such a bridge rectifier was always

constructed from discrete components. Since about 1950, a single four-terminal

component containing the four diodes connected in the bridge configuration became a

standard commercial component and is now available with various voltage and

current ratings.


http://en.wikipedia.org/wiki/Image:Diode_bridge_alt_1.svg


FIGURE 2.20: OUTPUT OF RECTIFIER CIRCUIT

2) OUTPUT SMOOTHING(USING CAPACITOR):

For many applications, especially with single phase AC where the full-wave bridge

serves to convert an AC input into a DC output, the addition of a capacitor may be

important because the bridge alone supplies an output voltage of fixed polarity but

pulsating magnitude (see diagram above).

FIGURE 2.21: OUTPUT SMOOTHING FILTER FOR RECTIFIER


http://en.wikipedia.org/wiki/Image:Rectified_waves.png

http://en.wikipedia.org/wiki/Image:Diode_bridge_smoothing.svg


The function of this capacitor, known as a reservoir capacitor (aka smoothing

capacitor) is to lessen the variation in (or 'smooth') the rectified AC output voltage

waveform from the bridge. One explanation of 'smoothing' is that the capacitor

provides a low impedance path to the AC component of the output, reducing the AC

voltage across, and AC current through, the resistive load. In less technical terms, any

drop in the output voltage and current of the bridge tends to be cancelled by loss of

charge in the capacitor.

This charge flows out as additional current through the load. Thus the change of load

current and voltage is reduced relative to what would occur without the capacitor.

Increases of voltage correspondingly store excess charge in the capacitor, thus

moderating the change in output voltage / current. Also see rectifier output

smoothing.

The capacitor and the load resistance have a typical time constant τ = RC where C and

R are the capacitance and load resistance respectively. As long as the load resistor is

large enough so that this time constant is much longer than the time of one ripple

cycle, the above configuration will produce a smoothed DC voltage across the load.

In some designs, a series resistor at the load side of the capacitor is added. The

smoothing can then be improved by adding additional stages of capacitor–resistor

pairs, often done only for sub-supplies to critical high-gain circuits that tend to be

sensitive to supply voltage noise.

f) VOLTAGE REGULATOR:

A voltage regulator is an electrical regulator designed to automatically maintain a

constant voltage level.

The 78xx (also sometimes known as LM78xx) series of devices is a family of self-

contained fixed linear voltage regulator integrated circuits. The 78xx family is a very

popular choice for many electronic circuits which require a regulated power supply,

due to their ease of use and relative cheapness. When specifying individual ICs within

this family, the xx is replaced with a two-digit number, which indicates the output

voltage the particular device is designed to provide (for example, the 7805 has a 5



volt output, while the 7812 produces 12 volts). The 78xx line is positive voltage

regulators, meaning that they are designed to produce a voltage that is positive

relative to a common ground. There is a related line of 79xx devices which are

complementary negative voltage regulators. 78xx and 79xx ICs can be used in

combination to provide both positive and negative supply voltages in the same circuit,

if necessary.

2.1.8 INPUT KEYPADS:

The inputs ie.4 inputs are utilized here with their specific destinations where the blind

person frequently visits, and these keypads are connected to the port 2 of

microcontroller that is to pin 2122,23,24 to transmit this particular data of the

location of the blind person’s i.e. latitude and longitude and his destination number.

This information reaches the buffer of the microcontroller and thus the remaining

process continues.

So initial inputs are very important for this project and it plays a major and crucial

role in this project by passing on the basic information for tracking of the route

through GPS and sending that tracked information to the service centre through GSM

and thus helps the blind person’s accessibility to go around in a much comfortable

and allow him to live independently.

2.1.9 BUZZER:

Buzzer is one of the component which is connected to the microcontroller of port 2

and pin 25.It has an audible range of 50 DB and thus it helps the blind person to know

that the tracked information is sent through the microcontroller to the GSM to the

customer service and thus it also has an important role . This is the buzzer that gives

the information about the message that reached LCD.

There is another buzzer near the GSM for the ring of the phone that is connected to

the DTMF socket, but here this buzzer in our project has an audible range of 10-15 db

and this can be extended by soldering the pin behind it in the GSM module and thus



can be used in real time implementation which produces double the sound it produced

initially.

Thus buzzer is one of the important component for the blind person to act

accordingly and lead an independent life in a better way.

2.1.10 SERIAL COMMUNICATION (RS232):

The serial communication is the most important component in this project as it

helps in communication between microcontroller, gps and gsm .An RS232 serial

communication is used for most of the projects as it is the only serial, asynchronous

form of communication. The following RS232 connectors can be used to test a

serial port on your computer. The data and handshake lines have been linked. In this

way all data will be sent back immediately. The PC controls its own handshaking.

The first test plug can be used to check the function of the RS232 serial port with

standard terminal software. The second version can be used to test the full

functionality of the RS232 serial port with Norton Diagnostics or Check it.



FIGURE 2.22 SERIAL COMMUNICATION PORTS

A) ADVANTAGES OF SERIAL OVER PARLLEL COMMUNICATION:

Serial Cables can be longer than Parallel cables. The serial port transmits a '1' as -3 to -25 volts and a '0' as +3 to +25 volts where as a parallel port transmits a '0' as 0v and a '1' as 5v. Therefore the serial port can have a maximum swing of 50V compared to the parallel port which has a maximum swing of 5 Volts. Therefore cable loss is not going to be as much of a problem for serial cables than they are for parallel.

You don't need as many wires than parallel transmission. If your device needs to be mounted a far distance away from the computer then 3 core cable (Null



Modem Configuration) is going to be a lot cheaper that running 19 or 25 core cable. However you must take into account the cost of the interfacing at each end.

Infra Red devices have proven quite popular recently. You may of seen many electronic diaries and palmtop computers which have infra red capabilities build in. However could you imagine transmitting 8 bits of data at the one time across the room and being able to (from the devices point of view) decipher which bits are which? Therefore serial transmission is used where one bit is sent at a time. IrDA-1 (The first infra red specifications) was capable of 115.2k baud and was interfaced into a UART. The pulse length however was cut down to 3/16th of a RS232 bit length to conserve power considering these devices are mainly used on diaries, laptops and palmtops.

Microcontroller's have also proven to be quite popular recently. Many of these have in built SCI (Serial Communications Interfaces) which can be used to talk to the outside world. Serial Communication reduces the pin count of these MPU's. Only two pins are commonly used, Transmit Data (TXD) and Receive Data (RXD) compared with at least 8 pins if you use a 8 bit Parallel method (You may also require a Strobe).

2.1.11 UART:

UART stands for Universal Asynchronous Receiver / Transmitter. Its the little box of tricks found on your serial card which plays the little games with your modem or other connected devices. Most cards will have the UART's integrated into other chips which may also control your parallel port, games port, floppy or hard disk drives and are typically surface mount devices. The 8250 series, which includes the 16450, 16550, 16650, & 16750 UARTS are the most commonly found type in your PC. Later we will look at other types which can be used in your homemade devices and projects.



FIGURE 2.24 UART PIN CONFIGURATION

The 16550 is chip compatible with the 8250 & 16450. The only two differences are pins 24 & 29. On the 8250 Pin 24 was chip select out which functioned only as a indicator to if the chip was active or not. Pin 29 was not connected on the 8250/16450 UARTs. The 16550 introduced two new pins in their place. These are Transmit Ready and Receive Ready which can be implemented with DMA (Direct Memory Access). These Pins have two different modes of operation. Mode 0 supports single transfer DMA where as Mode 1 supports Multi-transfer DMA.

All the UARTs pins are TTL compatible. That includes TD, RD, RI, DCD, DSR, CTS, DTR and RTS which all interface into your serial plug, typically a D-type connector. Therefore RS232 Level Converters (which we talk about in detail later) are used.

These are commonly the DS1489 Receiver and the DS1488 as the PC has +12 and -12 volt rails which can be used by these devices. The RS232 Converters will convert the TTL signal into RS232 Logic Levels.

The UART requires a Clock to run. If you look at your serial card a common

crystal found is either a 1.8432 MHZ or a 18.432 MHZ Crystal. The crystal in

connected to the XIN-XOUT pins of the UART using a few extra components which

help the crystal to start oscillating. This clock will be used for the Programmable

Baud Rate Generator which directly interfaces into the transmit timing circuits but not

directly into the receiver timing circuits. For this an external connection mast be made

from pin 15 (Baud Out) to pin 9 (Receiver clock in.) Note that the clock signal will be

at Baud rate * 16



CHAPTER - III

3.1 CIRCUIT DIAGRAM:

FIGURE 3.1 CIRCUIT DIAGRAM OF ROUTE GUIDANCE ANNOUNCER



3.2 INITIAL CIRCUITARY

FIGURE 3.2 INITIAL CIRCUIT OE ROUTE GUIDANCE



3.3 FINAL CIRCUITARY

FIGURE 3.3 FINIAL CIRCUIT OE ROUTE GUIDANCE



CHAPTER – IV

ADDITIONAL FEATURES:

4.1 INTRODUCTION:

One of the major goals for blind and visually impaired people is independent

mobility. In this paper we have an additional feature that if used creates most comfort

for the visually blind person. It involves a sensor in the integrated cane to detect the

movement of the user when he walks. This aid is a portable, self contained system

that will allow blind or visually impaired individuals to travel through familiar and

unfamiliar environments without the assistance of guide i.e. through the customer

service. In addition, it provides information to the user about urban walking routes

using spoken words to indicate what decisions to make and helps him from easily

knowing the hurdles.

4.2 COMPONENTS UTILIZED:

4.2.1 TWO 7555 TIMERIC’S

4.2.2 PHOTODIODE

4.2.3 INFRARED LED

4.2.4 TRANSISTOR BC547

4.2.1 7555 TIMER IC’S:

The ICM7555 is a CMOS timer providing significantly improved performance over

the standard NE/SE555 timer, while at the same time being a direct replacement for

those devices in most applications. Improved parameters include low supply current,

wide operating supply voltage range, low THRESHOLD, TRIGGER, and RESET

currents, no crow barring of the supply current during output transitions, higher

frequency performance and no requirement to decouple CONTROL_VOLTAGE for

stable operation.Page | 75



The ICM7555 is a stable controller capable of producing accurate time delays or

Frequencies.

In the one-shot mode, the pulse width of each circuit is precisely controlled by one

external resistor and capacitor. For a stable operation as an oscillator, the free-running

frequency and the duty cycle are both accurately controlled by two external resistors

and one capacitor.

1. FEATURES:

Exact equivalent in most applications for NE/SE555

Low supply current: 80 mA (typical)

Extremely low trigger, threshold, and reset currents: 20 pA (typical)

High-speed operation: 500 kHz guaranteed

Wide operating supply voltage range guaranteed 3 V to 16 V over full

automotive

Temperatures

Normal reset function; no crow barring of supply during output transition

Can be used with higher-impedance timing elements than the NE/SE555 for

longer

Time constants.

APPLICATIONS:

Precision timing

Pulse generation

Sequential timing

Time delay generation

Pulse width modulation

Pulse position modulation

Missing pulse detector



4.2.2 PHOTODIODE:

PHOTODIODE:

A photodiode is a type of photo detector capable of converting light into either current or voltage, depending upon the mode of operation.

QSD2030F — Plastic Silicon Photodiode

FIGURE 4.1: GENERAL PHOTO DIODE

1) PRINCIPLE OF OPERATION:

A photodiode is a PN junction or PIN structure. When a photon of sufficient energy strikes the diode, it excites an electron, thereby creating a free electron and a (positively charged electron hole). This mechanism is also known as the photoelectric effect. If the absorption occurs in the junction's depletion region, or one diffusion length away from it, these carriers are swept from the junction by the built-in field of the depletion region. Thus holes move toward the anode, and electrons toward the cathode, and a photocurrent is produced.

FEATURES:

Critical performance parameters of a photodiode include:

Responsivety:

The ratio of generated photocurrent to incident light power, typically expressed in A/W when used in photoconductive mode. The Responsivety may also be expressed as a Quantum efficiency, or the ratio of the number of photo generated carriers to incident photons and thus a unites quantity.

Dark current:

The current through the photodiode in the absence of light, when it is operated in photoconductive mode. The dark current includes photocurrent generated by background radiation and the saturation current of the semiconductor junction. Dark



current must be accounted for by calibration if a photodiode is used to make an accurate optical power measurement, and it is also a source of noise when a photodiode is used in an optical communication system.

Noise-equivalent power:

(NEP) The minimum input optical power to generate photocurrent, equal to the rms noise current in a 1 hertz bandwidth. The related characteristic directivity (D) is the

inverse of NEP, 1/NEP; and the specific directivity ( ) is the detectives normalized

to the area (A) of the photo detector, . The NEP is roughly the minimum detectable input power of a photodiode.

When a photodiode is used in an optical communication system, these parameters contribute to the sensitivity of the optical receiver, which is the minimum input power required for the receiver to achieve a specified bit error ratio.

Applications

P-N photodiodes are used in similar applications to other photodetectors such as photoconductors, charge-coupled devices, and photomultiplier tubes.

Photodiodes are used in consumer electronics devices such as compact disc players, smoke detectors, and the receivers for remote controls in VCRs and televisions.

In other consumer items such as camera light meters, clock radios (the ones that dim the display when it's dark) and street lights, photoconductors are often used rather than photodiodes, although in principle either could be used.

Photodiodes are often used for accurate measurement of light intensity in science and industry. They generally have a better, more linear response than photoconductors.

They are also widely used in various medical applications, such as detectors for computed tomography (coupled with scintillations) or instruments to analyze samples (immunoassay). They are also used in pulse ox meters.

4.2.3 INFRARED LED

1) GENERAL DESCRIPTION:

It is the same principle in ALL Infra-Red proximity sensors. The basic idea is to send infra red light through IR-LEDs, which is then reflected by any object in front of the sensor.

Then all you have to do is to pick-up the reflected IR light. For detecting the reflected IR light, we are going to use a very original technique: we are going to use another IR-LED, to detect the IR light that was emitted from another led of the exact same type!



FIGURE 4.2: OPRATION OF IR LED

2) PRINCIPLE OF OPERATION:

This is an electrical property of Light Emitting Diodes (LEDs) which is the fact that a led Produce a voltage difference across its leads when it is subjected to light. As if it was a photo-cell, but with much lower output current. In other words, the voltage generated by the leds can't be - in any way - used to generate electrical power from light, It can barely be detected. that's why as you will notice in the

schematic, we are going to use a Op-Amp (operational Amplifier) to accurately detect very small voltage changes.

FIGURE 4.3 GENERAL IR LED



FEATURES

• = 940 nm

• Chip material =GaAs with AlGaAs window

• Package type: T-1 3/4 (5mm lens diameter

• Matched Photo sensor: QSD122/123/124

• Medium Emission Angle, 40°

• High Output Power

•Package material and color: Clear, united, plastic

• Ideal for remote control application

4.2.4 TRANSISTOR BC547:

1) DESCRIPTION

The BC547 transistor is an NPN Epitaxial Silicon Transistor. The BC547 transistor is a general-purpose transistor in a small plastic package. It is used in general-purpose switching and amplification BC847/BC547 series 45 V, 100 mA NPN general-purpose transistors.

The BC547 transistor is an NPN bipolar transistor, in which the letters "N" and "P" refer to the majority charge carriers inside the different regions of the transistor. Most bipolar transistors used today are NPN, because electron mobility is higher than hole mobility in semiconductors, allowing greater currents and faster operation. NPN transistors consist of a layer of P-doped semiconductor (the "base") between two N-doped layers. A small current entering the base in common-emitter mode is amplified in the collector output. In other terms, an NPN transistor is "on" when its base is pulled high relative to the emitter. The arrow in the NPN transistor symbol is on the emitter leg and points in the direction of the conventional current flow when the device is in forward active mode. One mnemonic device for identifying the symbol for the NPN transistor is "not pointing in." An NPN transistor can be considered as two diodes with a shared anode region. In typical operation, the emitter base junction is forward biased and the base collector junction is reverse biased.

In an NPN transistor, for example, when a positive voltage is applied to the base emitter junction, the equilibrium between thermally generated carriers and the repelling electric field of the depletion region becomes unbalanced, allowing thermally excited electrons to inject into the base region. These electrons wander (or "diffuse") through the base from the region of high concentration near the emitter towards the region of low concentration near the collector. The electrons in the base are called minority carriers because the base is doped p-type which would make holes the majority carrier in the base



FIGURE 4.4 BC547 TRANSISTOR

1) BC547 Transistor Circuit Schematic Symbol

2) FEATURES:

• Low current

• Low voltage

• Three different gain selections

3) APPLICATIONS:

General-purpose switching and amplification



CHAPTER – V

CODING

SOFTWARE USED: “EMBEDDED C”

/*******************/

#include<reg51.h>

#include"lcddisplay.h"

#include"UART.h"

#include<string.h>

#include<intrins.h>

sbit buzzer = P1^7;

sbit gsm = P3^3;

sbit gps = P3^2;

sbit sw1 = P1^0;

sbit sw2 = P1^1;

sbit sw3 = P1^2;

sbit sw4 = P1^3;

unsigned char mobilenum[]="9908172936";

unsigned char msg[5];

unsigned char XX,newmsg=0,a,dest=0,temp[5],jj=0;

/** interrupt function to receive the data from GSM *****/

void serintr(void) interrupt 4

{

if(RI==1)

{

XX=SBUF;

if(XX=='+')



newmsg=1;

else

{

temp[jj++]=XX;

}

if(jj==10)

jj=0;

RI=0;

}

}

void main()

{

unsigned char i,gpsdata[45];

lcd_init();

UART_init();

lcdcmd(0x85);

sw1=sw2=sw3=sw4=1;

gps=1;

gsm=0;

RI=0;

lcdcmd(0x01);

msgdisplay ("searching for");

lcdcmd(0xc0);

msgdisplay("GSM modem");

delay(300);

send_to_modem("ate0"); //to avoid echo signals,

enter();

again:

send_to_modem("at"); // TO CHECKING GSM MODEM...

enter();

if(!RI) // Here we are waiting for data

witch is sending by GSM modem



goto again;

RI=0;

EA=1;

ES=1;

lcdcmd(0x01);

msgdisplay("SYSTEM");

cdcmd(0xc3);

msgdisplay("CONNECTED");

delay(100);

send_to_modem("at+creg=0"); //

enter();

delay(300);

newmsg=0;

xxx: lcdcmd(0x01);

msgdisplay("CHEKING SIM");

send_to_modem("AT+CPIN?"); //

enter();

delay(500);

if(newmsg==0)

goto xxx;

lcdcmd(0xC0);

msgdisplay ("SIM CONNECTED");

delay(500);

send_to_modem("at+cmgf=1"); // tr set message

format as text

mode

enter();

st:

lcdcmd(0x01);

msgdisplay("route guiding");

lcdcmd(0xC0);

msgdisplay("SYSTEM");

delay(500);



newmsg=0;

TR1=0;

TH1=-6;

gsm=1; // deselect the gsm

gps=0; // select the gps

TR1=1;

RI=0;

jj=0 ;

delay(100);

while(1)

{

RI=0;

a=0;

while(a!='$') //wait till the data

started from gps

{

while(RI==0);

a=SBUF;

RI=0;

}

i=0;

while(RI==0);

i=i+1;

RI=0;

while(RI==0);

RI=0;

i=i+1;

while(RI==0);

if(SBUF=='R') // take the value from gprmc command

{

RI=0;

while(RI==0);

i=i+1;



if(SBUF=='M')

{

RI=0;

while(RI==0);

i=i+1;

if(SBUF=='C')

{

RI=0;

while(RI==0);

i=i+1;

while(i<43) /// store the lattitude and longitude

{

while(RI==0);

gpsdata[i]=SBUF;

RI=0;

i++;

}

/** display latitude and longitude*/

lcdcmd(0x01);

msgdisplay("LT ");

for(i=19;i<30;i++)

lcddata(gpsdata[i]);

lcdcmd(0xc0);

msgdisplay("LG ");

for(i=31;i<43;i++)

lcddata(gpsdata[i]);

jj=0;

TH1=-3; // change the baud rate to gsm baud rate

9600

gsm=0; // gsm select

gps=1; // gps deselect



if((temp[0]=='R')&&(temp[1]=='I')&&(temp[2]=='N')&

&(temp[3]=='G')) //if we get a call then accept it

automatically

{

buzzer=0;

ES=0;

send_to_modem("ATA");

enter();

jj=0;

lcdcmd(0x01);

msgdisplay("call lifted ");

delay(500);

buzzer=1;

while(1);

delay(10000);

}

if(sw1==0) // if switch 1 pressed then destination is 2

{

dest=2;

goto sendmsg;

}

if(sw2==0)

{

dest=3;

goto sendmsg;

}

if(sw3==0)

{

dest=4;

goto sendmsg;

}

if(sw4==0)

{



dest=1;

goto sendmsg;

}

TH1=-6; //change the baud rate gps baud rate

gsm=1;

gps=0;

delay(10);

}

}

}

}

sendmsg:

gsm=0; // select the gsm for sending message

gps=1; //deselect gps

ES=0;

RI=0;

buzzer=0;

lcdcmd(0x01);

msgdisplay("destination-->");

lcddata(dest+48);

delay(500);

lcdcmd(0x01);

msgdisplay("sending message");

send_to_modem("at+cmgs=");

ch_send_to_modem('"');

send_to_modem(mobilenum);

ch_send_to_modem('"');

enter();

delay(50);

send_to_modem("PERSON AT ");

send_to_modem("LT:");

for(i=19;i<30;i++)

ch_send_to_modem(gpsdata[i]);



send_to_modem(" LG:");

for(i=31;i<43;i++)

ch_send_to_modem(gpsdata[i]);

send_to_modem(" destination-> ");

ch_send_to_modem(dest+48);

delay(10);

ch_send_to_modem(0x1a);

ES=1;

delay(1500);

lcdcmd(0x01);

msgdisplay("MESSAGE SENT");

buzzer=1;

goto st;

}

CHAPTER – VI

6.1 ADVANTAGES:

It is portable (size and power)

It helps the blind to be independent .

Time wastage is reduced.

It helps in better utilization of guidance system for smoother transportation.



Support the blind, make the blind feel more closeness with normal life, they

will feel self-confident.

6.2 LIMITATIONS OF EXISTING DEVICES:

Existing orientation and way finding aids are limited by:

1) The types, amounts, and accuracy of information they can provide.

2) The types of environments in which they can function.

3) Their user interface structure/operating procedures. One of the reasons for these

limitations is that while there has been a great deal of research in the area of

electronic travel aids for obstacle avoidance , there has been little comparable

research and development of orientation and way finding devices.

Based on the needs and diversity of the potential user population as described above,

and the previous research of the authors (See Previous Research below), a well

designed orientation and way finding aid should ideally be able to provide the user

with:

1) Their current location and head in relative to known landmarks and the desired

destination,

2) Descriptions of prominent surrounding features and the general layout of the

greater surrounding environment, and

3) Things of interest to the user in the greater surround in environment. Further,

location information should be accurate to within one meter, and be provided in a

fashion that can be clearly comprehended regardless of location or type of

environment.

Finally, the system should be usable by people with a variety of age-related co-

morbidities. In other words, the interface must meet established universal design

criteria.

6.3 APPLICATIONS:



The route announcement is not only specified for the blind but also to

common human to release him from the trouble of tracking the route

and reaching to the destination.

It has its application in education field also.

It has applications in detecting nuclear explosive objects.

It also has its application in military field.

6.4 FUTURE SCOPE

To improve advantages and solve some features which are the minute limitations in

our project, some research is done for developing it and making it most advanced

usage of it for blind people :

Through the application and implementation of this system we hope to apply

this principle on many other systems as Kiosk System and other public

systems. With purpose to support more for the blind in particular and disabled

people in general we need optimize the features of the system.

In blind recognition part, we interested to use GSM AND GPS technology

which is very relevant and high efficiency when the blind can control their

situation.

This system will help blind people to find accurate information of the bus

which they should take. So the blind can go to the desire destination. In

addition to the more complex technologies such as voice recognition can also

be applied aimed to optimize the system. This system will give a best support

for the participants to use, especially the blind picture.

Using this system we can extend its application in creating an automatic

vehicle for blind and help them go out independently ,and this can also be

used in the application of detecting of thief or anybody who has entered the

room and protect themselves in everyway possible without being dependent .

6.5 ACTUAL WAY OF ACCESING THE MODEL:



FIGURE 6.1 ACTUAL WAY OFACCESSING THE MODEL

CHAPTER – VII

RESULT ANALYSIS:

The major goal of us doing this project was to establish a tool that is portable and

most convenient one to utilize, using the most common technologies that are used in Page | 92



our day to day life, and the amount of knowledge we have is kept forward only to

help visually impaired people be independent in life and live their lives in the most

happiest way as everyone does and grab success towards them in life. Thus through

this project we’ v created a tool that has not been created yet in INDIA and is

developed in AUSTRALIA with different technologies like speech synthesizer and

tactile displays specially for visually impaired people which made us develop module

with components other then that, and we hope this would help blind people and make

our technology also the “DEVELOPING ONE” and thus soon we can see developed

INDIA.

CONCLUSION

Thus this system is a tool that would remove the barriers in life for visually

challenged people and help them achieve their goals and career that they aspired to



have. It also gives them independence and confidence which would bring success to

them as well bring out the talent of such people in various way and thus helps INDIA

TO BECOME THE DEVELOPED NATION. Thus our motives have partially

become successful and hope this would be utilized in the most effective way possible.

REFERENCES:

WE ARE NOT ADDED ANY REFERENCES YET



NOTE

ALL REFERENCES MUST BE BOOKS

THERE SHOULDN’T ANY ONLINE LINKS.


main documentation

Documents

blind people

blind trip

blind cane

blind pedestrians

blind navigation system

route guidence

blind included walking

route guidance