tribhuvan university institute of engineering on...

TRIBHUVAN UNIVERSITY

Institute of Engineering Advanced College of Engineering and Management

Kupondole, Lalitpur

A Final Year Project Report on

“WIRELESS ULTRASOUND FLOOD MONITORING SYSTEM”

[CODE NO.: EG777EX]

BY

Amit Kumar Tamang Exam Roll No: 23005 Kushal Khanal Exam Roll No: 23023 Santosh Kumar Baral Exam Roll No: 23036

Lalitpur, Nepal February, 2008


Institute of Engineering

Advanced College of Engineering and Management Kupondole,Lalitpur

A Final Year Project Report on

“WIRELESS ULTRASOUND FLOOD MONITORING SYSTEM”

[CODE NO.: EG777EX]

BY

Amit Kumar Tamang ([email protected]) Exam Roll No: 23005 Kushal Khanal ([email protected]) Exam Roll No: 23023 Santosh Kumar Baral ([email protected]) Exam Roll No: 23036

A FINAL YEAR PROJECT WORK SUBMITTED TO THE DEPARTMENT OF COMPUTER AND ELECTRONICS ENGINEERING FOR THE PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF THE BACHELOR’S IN ELECTRONICS AND COMMUNICATION ENGINEERING

Lalitpur,Nepal February, 2008


Institute of Engineering

Advanced College of Engineering and Management Kupondole,Lalitpur

Department of Computer and Electronics Engineering

“WIRELESS ULTRASOUND FLOOD

MONITORING SYSTEM” Being a project submitted in partial fulfillment of the requirements for the degree of Bachelor’s Degree in Electronics and Communication Engineering. In the

Department of Computer and Electronics Engineering Advanced College of Engineering and Management

Tribhuvan University

BY

Amit Kumar Tamang ([email protected]) Exam Roll No: 23005 Kushal Khanal ([email protected]) Exam Roll No: 23023 Santosh Kumar Baral ([email protected]) Exam Roll No: 23036

Lalitpur,Nepal February, 2008

CERTIFICATE

We have pleasure in forwarding the project of Amit Kr.Tamang, Kushal Khanal,

Santosh Kr. Baral entitled “Wireless Flood Monitoring System Using Ultrasound”

for the completion of Bachelor of Engineering in Electronics and Communication of

this institute.

Amit Kr. Tamang, Kushal Khanal, Santosh Kr. Baral have completed the project work

for the full prescribed period under the curriculum, and the project embodied the result

of their investigations conducted during the period they worked as a full time student of

this department.

(Er. Rosish Shakya) (Er.Surya Pd. Aryal)

Supervisor External Examiner

(Er. Nita Koirala) (Er. Dhaneshwar Sah)

Internal Examiner H.O.D of Computer and Electronics

TABLE OF CONTENTS

Title Page Number

Acknowledgements i Abstract ii List of abbreviations iii List of figures iv-v

1. Introduction 1-2

Background 1 Problem Statement 2 Objectives 2

2. Literature Review 3-16

Previous works 3 Related Theory 5

2.2.1 Sound 5 2.2.2 Factors affecting the propagation of sound wave 6 2.2.3 Properties of sound 8 2.2.4 Application of the reflection of sound 9 2.2.5 Ultrasound 9 2.2.6 Doppler’s effect 12 2.2.7 Application of Doppler’s shift 12 2.2.8 Ultrasonic transducer 16 2.2.9 Application of ultrasound 16

3. Methodology 17-72

3.1 System Architecture 17 3.1.1 Transmission 18 3.1.2 Reception 18 3.1.3 Detection 19 3.1.4 Signal holding 19 3.1.5 Pulse Shaping 19 3.1.6 Level Calculation 19 3.1.7 Flow Calculation 19 3.1.8 Display 19 3.1.9 Wireless Module 20

3.2 Description of components 20 3.2.1 Ultrasonic transducers 20

3.2.2 8051 Microcontroller 20 3.2.3 Voltage Regulators 26 3.2.4 Diodes 27 3.2.5 Line driver or Voltage translator 28 3.2.6 DC socket 28 3.2.7 LM833 29

3.2.8 LM358 31 3.2.9 CD4011 31 3.2.10 CD4069 32 3.2.11 74HC04 33

3.2.12 555 Timer 34 3.2.13 LCD 34 3.2.14 RF Modules 34

3.3 Circuit Explanation 36 3.3.1 Power Supply Circuit 36 3.3.2 Transmission Section 36 3.3.3 Reception Section 37 3.3.4 Signal Detection 39 3.3.5 Circuit Diagram 44

3.4 Program in System 46 3.4.1 Flowchart 46 3.4.2 Resolution calculations 53

3.5 Serial Communication 56 3.5.1 Serial data communication in MCU 57 3.5.2 RS232 Protocol 58

3.6 Software & Equipments 59 3.6.1 Proteus 6 Professional 59 3.6.2 MCU programming in C 62 3.6.3 SDCC Compiler 64 3.6.4 Visual Basic 6.0 66 3.6.5 Oscilloscope 68 3.6.6 Digital Multimeter 69

3.7 Problem faced 70

4. Result and Conclusions 73 4.1 Results 73 4.2 Limitation 73 4.2 Conclusion 73 4.3 Future Enhancements 73

References 74 Appendix A: Liquid Crystal Display 75 Appendix B: Keypad interfacing with MCU 79 Appendix C: Cost Analysis 82

i

ACKNOWLEDGEMENTS

First of all we would like to express our sincere thanks to the Department of Computer

and Electronics Engineering, ACEM, for providing us the environment to complete

this final year project successfully.

We would like to record our appreciation to our H.O.D. Er. Dhaneshwor Shah, for his

valuable encouragement throughout the project. His efforts created an environment and

infrastructure to our project.

We express our gratitude to our project Supervisor Er. Rosish Shakya who seriously

helped us from the beginning to the end of our project. He managed us his precious time,

suggestions and continuous effort to support us. We are obliged to Er .Anish Adhikari

and Er. Amit KC for their genuine attempts that they showed to us.

We are extremely obliged to record our heartfelt thanks to our friend Mr. Rajesh

shrestha for his priceless help and guidance in visual basic programming.

We express our appreciation to Mr. Ujwol Napit for his valuable suggestion and Mr.

Dhan Bahadur Magar for his priceless effort during our demonstration.

We would like to express our heartfelt thanks to Project Association of Computer and

Electronics, PACE for valuable support during the project.

We extend our sincere thanks to I.O.E which has given us the opportunity to do this

project which will help us enhance our career.

We would like thank Mr. Ganesh Gautam for cooperating us in various ways. Last but

not the least, we would like to appreciate all of our classmates for their encouragement

and help, they fuelled in us throughout.

Amit Kumar Tamang

Kushal Khanal

Santosh Kumar Baral

ii

ABSTRACT

Our project entitled “Wireless Ultrasound Flood Monitoring System” is designed to

reduce the information gap between the government and the people in case of natural

catastrophes like flood, glacial outburst. We don’t have the Information System till now

that informs people about the possible dangers of those disasters. Each and every year

many people lose their home, property and life. In one hand the government itself has no

information and secondly it has problem in evacuating the people from such site.

Examples are the terror of eruption of glacial lake Chho-Rolpa, Pashupati Bagmati Dam

eruption and various Terai region floods due to the dams built in border side of Indian

territory. Thus we came up with this project. In our project, the level and flow of water is

continuously monitored. Our device can be placed at these sites. Ultrasonic transducer

which generates 40 KHz frequency wave is chosen, that is non hazardous, non audible,

non irritating and it is easily reflected from any medium except air. The level and flow of

water are calculated by the microcontroller controlled site and sent wirelessly to the

remote monitoring station by RF modules. There is also the provision of GUI made by

Visual Basic that helps the operator at site to read out the current values after proper

authentication. There is the facility of Visual display, automatic mode and manual mode

and the information database. The Front End VB GUI is bounded to back end MsAccess

Database via SQL. The statistics for latest ten values for both level and flow can be

visually perceived in plots. Flow uses Doppler’s Shift and level calculation is based on

echo reflection property of waves. The increasing flow hints at the probability of flood

and the increasing level ensures the flood is certain. So the emergency alarming is

performed to the public and the alternative control action such as automatic gate opening

can be performed manually from the monitoring station. Our project is simple, reliable

and economically feasible according to the cost benefit analysis. Thus with

implementation of our project destruction by catastrophes can be drastically reduced .It is

dedicated to the welfare of the public and the government. We have been able to meet our

requirement.

iv

LIST OF FIGURES Figure Number

Title Page Number

2.1 Effect of wind on sound 7 2.2 Illustration of Echo Reflection 9 2.3 A transducer with a circular radiating surface whose diameter is

large in comparison to a wavelength produces a narrow, conical beam pattern with multiple secondary lobes.

11

2.4 Illustration of Doppler’s shift 12 2.5 Application of the Doppler’s shift in Echolocation of a Moving

Object 13

2.6 Ultrasonic transducer 16 3.1 System Block Diagram 17 3.2 Back view of the SQ40T/SQ40R 20 3.3 AT89C51 IC pin description 23 3.4 Minimum connection of 8051 MCU system 26 3.5 Pin description of voltage regulator 7805 & 7809 26 3.6 Figure showing input sine wave and its half wave rectification

using diodes. 27

3.7 Negative voltage protection in the circuitry using diode 27 3.8 Line driver MAX232 28 3.9 Null modem 29 3.10 Dual 8 pin Opamp 30 3.11 Non inverting configuration of an amplifier 31 3.12 Quad NAND gate IC 32 3.13 Logical symbol and truth table of NAND gate 32 3.14 Six NOT gates IC 33 3.15 Logical symbol and truth table of NOT gate 33 3.16 555 timer configuration to generate square wave. 34 3.17 RF modules 35 3.18 Voltage regulators 36 3.19 Astable mode of 555 timer 37 3.20 Circuit to excite ultrasonic transmitter 38 3.21 Opamp as comparator (a) Circuit diagram (b) Timing diagram 40 3.22 SR FF (a) Circuit Diagram (b) Timing diagram 41-42 3.23 Pulse shaping circuit 42

3.24 (a) Schematic of circuit at site 44 3.24 (b) Schematic of circuit at monitoring station 45

3.25 Flowchart for level 47 3.26 Flowchart for flow 47 3.27 Overall Flowchart of the system 49-53 3.28 Waveform of serial data unit 57 3.29 Snap shot of simulation circuit to test the code in Porteus ISIS

professional 61

v

3.30 Designed PCB layout 62 3.31 Snap shot of outlook of EZ-Downloader 65 3.32 Compiling ultrasound.c using SDCC 66 3.33 Snap shot of interfacing form designed using Visual Basic

(a) Manual mode (b) Auto mode 67

3.34 Plots of measured values of level and flow 68 A.1 Structure of 2X16 LCD 76 C.1 Circuit diagram of Keypad 90 C.2 Flowchart for keypad programming 91

Wireless Ultrasound Flood Monitoring System

1

Introduction

1.1 Background Technology is the result of effective technique applied for solving particular problems

with available resources. The technology has made human life easier, safer and more

productive. The life of mankind has become impossible without the technology. Latest

technologies are emerging day by day and one can’t remain aloof without using

technology.

In fact the technology has revolutionized the world. The development of electronics

industries accelerated from 1980s only after the invention of ICs. The invention of ICs

has extensively reduced the size, weight, cost and increased the quality, reliability of

every electronics product. From a simple amplifier radio to satellite communication,

space exploration, electronics products are widely used.

The production of such electronics goods is not simple as we use it. It involves the detail

study of nature, waves, flow of energy, study of available materials, various experiences

and expertise of the past and their modification as per the requirement. It takes a lot of

time, effort and perhaps lifelong dedication of many individuals.

Our final year project is one of the implementation of electronics to make wireless

ultrasound flood monitoring and alarming system. Our project is a microcontroller based

prototype for level and flow measurement of flowing water. The system is mainly

designed to be used at the remote site and for the monitoring purpose. The ultrasonic

transducers are used to measure the liquid level and its flow at suspected place. And

AT89C51/52 is used as MCU. The system consists of RF wireless modules for the data

transmission from the remote site to the remote monitoring station which will indicate

the water level, water flow and useful for flood monitoring. The detail description about

ultrasound and ultrasonic technology, description about the ATMEL AT89C51, software

and hardware description are presented in the sections followings.


2

1.2 Problem Statement In Nepal, there is not a single system, which can be used for monitoring and alarming in

case of floods and eruption of glacial lakes. That has resulted in loss of lives and

property especially in Terai and Himalayan region. There is also problem for government

in timely informing and evacuating people form the affected sites, which has multiplied

the casualties.

There have been many cases of visit of environmental inspectors form different nations

to inspect the condition of glacier’s lake and they seem to be very interested rather that

us. For instance the visit of Japanese environmentalist to Solukhumbu’s Imja glacial

lake, PM of Norway observing various glacial lakes in Nepal.

In consideration with above severe problem, we have come up with our design. Our

design can remotely monitor the level and flow of water in suspected site and alarm the

people as per the information given from the site. And we are certain that this system can

serve as a prototype to figure out, the dependencies on the foreigners on such problems.

1.3 Objectives: The main issue of our project is to design a Remote Flood Monitoring and Alarming

System. So, our objectives are:

a. To measure the level of Water

b. To measure the flow of Water

c. To convey the information Wirelessly to the monitoring station

d. To activate the emergency alarming as per the information


3

Literature Review

2.1 Previous works Nothing in this world is hundred percent static as lord Buddha said “Everything in this

universe is in the state of flux”. Nothing is ultimate and satisfactory. The nature of

human is to dream and imagine, thus modify available tools and technique, which lead

human to this era.

Technology has revolutionized the life standard of human. We are in the information

age of the 21st century. The role of engineers in this age is certainly of vital importance.

It is of their genuine attempt and aptitude that everyday one more comfortable

technology is in our hand. The change is physiological, psychological, and technological

and persists in each and every aspect of life and environment within which man lives.

Our project entitled “Wireless ultrasound flood monitoring and alarming system” is

not truly original in itself from the very scratch. At different times in the past, many

attempts were continually made by our seniors some of which concepts we have

incorporated from theirs. We came across the reports “Distance measurement using

Ultrasound “that simply illustrated how ultrasound echo- reflection can be used in the

distance measurement. This illustration was limited up to 0.3m in distance and the

resolution was poor. They had used PIC not able to measure the distance of moving

object as well.

The other project that we came across was “Ultrasonic Imaging System” undertaken in

similar concept as the radar pulses they were passed inside the body which reflected

waves in various patterns that gives the various information of different organs of the

body. These waves were slow than x ray naturally. The electronic circuitry of this project

was so poor that it could not deserve the quality of imaging. They had used various

modes such as A-Mode, B-Mode, Doppler’s Mode and M-Mode.


4

Next we came across a project work entitled” Wireless PC to PC communication

Using IR Modulation” which was limited to the text files only. They had used data

transfer in asynchronous mode to transfer text files from one PC to another. They had

used IR modulation and demodulation techniques and the data transfer rate was limited

up to maximum rate of 2400bps. The text file was transferred on polling basis rather

than the in interrupt basis.

“Device Control Using IR” was also a project in which 555 timer was used in

modulating the ASCII value pulses and decoding those pulses to perform specified

action depending upon the characters sent at the same rate of 2400 bps.

“Wireless Remote Water Level Monitoring System Using Ultrasound” was a project

by our seniors. This used the Echo -Reflection property of ultrasound. The level of water

was detected by calculating the time elapsed between transmitted and received pulse and

multiplying that time by the standard velocity at that temperature. There was not special

provision of selecting the velocity of sound as per the environmental temperature. The

resolution calculated was so poor that the look up table method was implemented in

microcontroller programming. The wireless transmission was not achieved satisfactorily.

There was no interface to handle the device in site and therefore no question of user

authentication at site. On the other hand the flow theory was explained but not carried

out due to lack of time. There was not the provision of continuous measurement of the

parameters and previous value observation as well.

Thus we became ready to overcome all the challenges that project faced and came up

with more features, more accurate values, and longer range of operation. The level

monitoring is directly calculated rather than based on look up table to predict only the

range. Flow is completely the concept of our own based on Doppler’s Effect that we

carried out. Further we shaped the pulse on our own way. Half duplex communication

between the remote site and a center based PC monitoring system in easy user guided

VB interface. There is the feature of Automatic and Manual mode of operation and the

provision for previous statistical data plotted. This will generate the error signaling in


5

condition of the measured parameters being out of range. As an enhancement of the

project further, the velocity of different layers of fluid in streamlined motion and the

profile could also be shown along with mass flow per second. But due to limitation of

time we performed preliminary tests but could not achieve the complete success.

2.2 Related Theory 2.2.1 Sound

Sound is a mechanical longitudinal wave that is produced by any vibrating body.

Sound energy is transferred from one place to another in the form of compression and

rarefactions. Compressions are those regions where the density of the propagating

medium increases and rarefactions are those regions where the density of the medium

decreases. Being a mechanical wave it needs material medium for the propagation of

wave. The particles of the medium vibrate simple harmonically about their mean position

along the direction of propagation of wave.

The velocity of sound depends upon the Bulk Modulus and Density. The bulk modulus

also called compressibility of liquids is defined and the ratio of increase in pressure to

a change in volume. Also for adiabatic expansion of air considered, then velocity of

sound is inversely proportional to the density (δ) and directly proportional to the square

root of the temperature which further depends upon humidity. As the humidity of air

increases the amount of water vapor increases in the air which reduces the density of

air that in turn increases the velocity of sound. This can be well proved by the

following equation

MRT

MPVPEv ====γ

δγ

δ …(2.1)

For air,

E = 1.5 x 105 Nm-2

δ = 1.27 kgm-3

v = 345 ms-1


6

For water,

E = 2.05 x 109 Nm-2

δ = 1.27 kgm-3

v = 345 ms-1

2.2.2 Factors affecting the propagation of sound wave

Density of Medium:

The velocity of sound is dependent upon the density of the medium along with the

Elasticity property of the medium. At a given pressure, the velocity of sound is inversely

proportional to the square root of the density. That means greater the density of the

medium smaller will be the velocity of sound in the gaseous medium where there is

constant pressure. For example the velocity of sound in Hydrogen gas is greater in

Oxygen at constant pressure because of the fact that the density of hydrogen is less than

that of the oxygen.

In case the elasticity of the medium is much high as compared to the increase in

density velocity of the sound will be greater than that of the gaseous medium. For this

reason the velocity of the sound is greater in liquids than in gases and still greater in the

solids than the liquids. For example, the sound of train heard from the rails is faster than

the sound from the air as the velocity of sound is greater in iron (solids) than the

gases(air).

Moisture or Humidity:

The presence of moisture in the air reduces the density of air because the density of

vapor(0.92Kgm-3) is less than the dry air (1.293 Kgm-3) . Since the velocity of sound in

gases is inversely proportional to the square root of the density of the medium, the

velocity of sound is greater in a moist day than in a dry day.

Temperature:

The velocity of sound is directly proportional to the square root of the absolute

temperature of the gaseous medium. That means the velocity of the sound in hot air is


7

greater than on a cold day. In fact the velocity of sound increases by 0.61 ms-1 for every

degree rise in temperature.

Velocity of Wind:

Figure 2.1: Effect of wind on sound

The velocity of sound is affected by the wind velocity. Let δ be the angle between the

velocity of sound V(sound) and the wind direction U(Wind). Then The effective velocity

of sound is given by

V= U(wind) Cos δ + V(sound) ...(2.2)

From the above relation it is clear that the velocity of the sound increases when δ is acute

otherwise the velocity of sound decreases. As special cases, the velocity of sound and air

will be added together when both are in same direction(δ=0), will be subtracted when in

opposite direction(δ=1800). Also it is interesting to note that the wind will not affect the

velocity of the sound when it blows perpendicular(δ=900) to the propagation of the

sound.

Pressure:

The velocity of sound in gaseous medium has no effect in the velocity of the sound. It is

because the gases are compressible. That means as the pressure increases, the density of

the gases increases and the overall ratio of the pressure and density remains constant .So

the velocity of sound in gases is independent of the pressure.


8

Intensity of sound is defined as the amount of sound per unit area per unit time when

the unit area is being held perpendicular to the direction of propagation of the wave.

The loudness of sound is the ratio of intensity of sound and the threshold of hearing

10(-12) Wm-2 for a test frequency of 1000Hz expressed in decibels. Sound undergoes

different properties such as reflection, refraction, diffraction, Interference, attenuation,

scattering etc.

The intensity goes on decreasing exponentially with the distance (x) and depending

upon a property called attenuation constant (u) as given by

I = I0 e(-u*x) …(2.3)

2.2.3 Properties of sound

Reflection of Sound:

When we consider the reflection of sound waves, the nature and direction of motion of

the particles of reflected wave depends upon whether the reflecting surface is a denser or

a rarer medium.

Reflection from denser medium:

Sound consisting of longitudinal waves and hence compressions and rarefactions, when

strikes the surface of denser medium, a wave of compression is reflected as a wave of

compression and the rarefaction is reflected as the rarefaction i.e. no change in the type

takes place. That means that a phase shift of 1800 takes place from reflection from the

denser medium.

Reflection from rarer medium:

When sound wave strike the surface of rarer medium, a wave of compression is reflected

as the wave of rarefaction and the wave of rarefaction is reflected as the wave of the

compression i.e. the change in type takes place. However, the direction of motion of

particles after reflection remains the same as that of incident waves i.e. there takes place

no change in sign. In other words , no change in phase takes place in the reflected wave.


9

2.2.4 Application of the reflection of Sound:

Echo:

When sound is produced in front of a obstacle, sound is reflected back and repetition of

sound is heard back (if within the audio range 20HZ to 20KHz). This repetition of sound

from distant object is called echo.

Let,

∆t=Time taken to hear echo from distant obstacle.

v= Velocity of sound at that temperature.

D=Distance between the source and the obstacle

Then , ⎟⎠⎞

⎜⎝⎛ ∆×=

2tVD ...(2.4)

Figure 2.2: Illustration of Echo Reflection

2.2.5 Ultrasound

Ultrasound is sound of frequency beyond the audible range of Human 20 Hz to 20 KHz.

Ultrasound can not be perceived by the human ear but can be heard by the bats and

whales in detecting the objects nearby and act accordingly. The sound below 20 Hz

sound is called infrasound.

Ultrasound in the range of 2 MHz to 20 MHz is used in Medical ultrasound. And for

internal local use of about 50 MHz. Higher frequencies have shorter wavelength and


10

their reflectance increases to provide better information about the objects that come

their way.

The generation and measurement of ultrasonic waves is accomplished mainly by

piezoelectric (or magnetostrictive) or by optical means. Piezoelectric sensors are based

on piezoelectric effects – an effect that produces electric field due to polarization of the

dielectric material due to applied mechanical deformation or pressure and vice versa.

In optical methods we use diffraction property of light the ultrasonic waves are

rendered visible.

Ultrasound is reflected at interfaces between tissues with differing acoustic

impedances. The acoustic impedance is measured as the product of velocity of sound

and the physical density of the medium.

Sounds in the range of 20 KHz to 100 KHz are commonly used for communication and

navigation by bats, dolphins. Much higher frequencies are used for medical purposes.

Ultrasonic waves are produced and received by the ultrasonic transducers. A variety of

medical diagnostic applications that work on echo-reflection and Doppler’s shift are

used such as in echocardiogram. Ultrasound imaging is one of the emerging

technologies that have very high resolution.

Ultrasound Properties:

Some of the fundamentals that influence the operation of ultrasonic sensors are

explained here. The maximum detection range of an ultrasonic sensor is typically longer

for lower frequencies, while the resolution and accuracy are typically better at higher

frequencies. The strength of the target echo, however, is greatly affected by the geometry

and reflectivity of the target, thereby affecting the range and resolution of the distance

measuring system.

One of the biggest sources of error in an ultrasonic position measurement is the

variability of sound speed in the transmission path between the sensor and the target,


11

largely caused by uncertainty in the average temperature along the path. Maximum

measurement accuracy is therefore obtained when temperature compensation is used

within the sensor. The temperature uncertainty affects absolute accuracy substantially

more than it does the relative accuracy of an incremental measurement.

It is not unusual for the amplitude of echo levels to change by large amounts from pulse

to pulse due to variations in sound speed in the medium, caused by factors such as air

turbulence or target movement. Also, long-term changes in humidity can have a

significant effect on the strength of an echo from a target.

It is usually desirable to use a sensor with the narrowest possible radiation pattern that

can detect the required targets. The beam width and the directivity depends upon the

ration of D/λ. Greater the ration greater the directivity and less will be the beamwidth.

For a greater frequency, the narrower the radiation pattern of the sensor, the longer the

maximum range of the sensor and the less susceptibility to unwanted targets at the sides

of the sensor. However, a very narrow radiation pattern from a sensor will require more

accurate orientation of the sensor's axis with regard to the acoustic beam's

perpendicularity to a flat target. In any event, the user must understand the effective

beam angle of the sensor when determining which targets will be detected and which

will be ignored. This effective beam angle changes with the distance of the target and the

strength of the reflection from the target.

Figure 2.3: A transducer with a circular radiating surface whose diameter is large in

comparison to a wavelength produces a narrow, conical beam pattern with

multiple secondary lobes.


12

2.2.6 Doppler’s Effect

The apparent change in frequency due to the relative motion of the sound source and

the observer is called Doppler’s Effect. This effect was observe d by Christian Doppler

in 1942 and proved in 1945 in Holland and so called Doppler’s Effect. Doppler’s effect

in light and sound can be used to find the velocity of the moving object.

Doppler’s effect in light is used by RADAR (Radio Navigation And Ranging). It

determines the velocity of flying planes practically applied in airports and many military

and spy planes.

Figure 2.4: Illustration of Doppler’s shift

According to this effect when the source of sound approaches the stationary observer

then the apparent frequency increases and when it recedes away the apparent frequency

decreases and the target object velocity can be obtained using above equation.

Also Red shift phenomenon in light is observed under this effect that shows the evidence

of increasing universe.

2.2.7 Application of Doppler’s Shift

This section describes the application of the Doppler’s shift in Echolocation of a Moving

Object in detail. And the theory described below supports our system to implement the

Doppler’s Shift practically.


13

Figure 2.5: Application of the Doppler’s shift in Echolocation of a

Moving Object

In the figure 2.5 we have,

f = Actual frequency of Ultrasound transmitted by the Transmitter i.e. source

f’ = Frequency of the moving object (Which becomes the secondary transmitter i.e.

Secondary Source of Sound)

f” = Apparent Frequency of Ultrasound to the receiver.

c = Velocity of the sound wave at that particular temperature, humidity and for that

particular medium.(Say air).

0v = Velocity of the moving Object.

d = Distance between the Transmitter and the Receiver

D = Distance between the Receiver and object

As object moves at a constant speed, the object intercepts the ultrasound and scatters it

back. The frequency received by the moving object is given by the following formula.

fv

cosv c ' f

s

0 ×⎟⎟⎠

⎞⎜⎜⎝

⎛ +=

α …(2.5)

As it scatters ultrasound, the object becomes a secondary, moving ultrasound source. The

velocity of this source towards receiver is βcosv 0


14

The receiver frequency f” is given by

fcosvc

cosv-c

c f'cosv-c

c 'f' 0

0 0×⎟⎠

⎞⎜⎝

⎛ +×⎟⎟⎠

⎞⎜⎜⎝

⎛=×⎟⎟

⎠

⎞⎜⎜⎝

⎛=

cα

ββ …(2.6)

Hence,

fcosv-ccosvc

'f' 0

0 ×⎟⎟⎠

⎞⎜⎜⎝

⎛ +=

βα

…(2.7)

Assume, βα = Now solving equation 2.5 for v0, we get,

βsecf'f'f - 'f' v0 ××⎟⎠⎞

⎜⎝⎛

+= c …(2.8)

From the experimental arrangement, we can show that

( )D2

D4dsec

22 +=β …(2.9)

Then the velocity of the moving object is given by

( )D2

D4df'f'f - 'f' v

22

0+

××⎟⎠⎞

⎜⎝⎛

+= c …(2.10)

In terms of time relation the above equation will be

( )D2

D4dTrxTtxTrx-Ttx v

22

0+

××⎟⎠⎞

⎜⎝⎛

+= c …(2.11)

The shift is too small to be measured over a single pulse, we have to take ’”N” number of

pulses to observe accumulative shift.

( )D2

D4dTrxNTtxNTrxN-Ttx Nv

22

0+

××⎟⎠⎞

⎜⎝⎛

×+×××

= c …(2.12)


15

When we have d<<D, Then Sec(ß) ≈1

c×⎟⎠⎞

⎜⎝⎛

×+×××

=TrxNTtxNTrxN-Ttx Nv0 …(2.13)

If the experimental arrangement is symmetric (α ~ β) and if we assume: v0cosα << c,

then Doppler shift can be written as:

fcos v2

f- 'f' f 0 ×⎟⎠⎞

⎜⎝⎛≅=∆

cα

…(2.14)

Experimentally, we can measure the beat frequency between the transmitted (f) and

received (f”) sounds, amplified as Doppler waveform, from which we obtain the Doppler

shift.

Knowing the ultrasound frequency f and speed c, we can measure the Doppler shift ∆f

and the angle α and thus we can calculate the speed of the moving object 0v :

( )⎟⎠⎞

⎜⎝⎛=

αcos f 2'-ff'cv0 …(2.15)

Assume °= 60α , we get

( )⎟⎠⎞

⎜⎝⎛=

f '-ff'cv0 …(2.16)

⎟⎠⎞

⎜⎝⎛ −×= 1

f'f'v0 c …(2.17)

⎟⎠⎞

⎜⎝⎛ −×= 1

TrxTtxv0 c …(2.18)


16

2.2.8 Ultrasonic Transducers

Ultrasonic transducers are based on Piezoelectric Effect or on the Magnetostrictive

effect. This can be utilized to produce ultrasonic transducer of up to some giga-hertz

operations as per the specific requirements. The transducers used in our project are

SQ40T and SQ40R for our purpose because other high frequency transducers were not

available in our market.

Figure 2.6: Ultrasonic transducer

2.2.9 Application of ultrasound

Ultrasound was primarily used in SONAR systems where various oceanic floors and bed

distance were measured. It is used in imaging systems including eco-cardiology where

the picture and working condition of the heart is shown in video. It is used in treatment

of kidney stone where special shock waves are sent to the prone areas and stones broken

down into smaller pieces that could be readily carried out by the urinary system

thereafter. It is still used in determining the blood flow within the vessels and different

flow of liquids in pipes in the industries.

Ultrasound is used in many detection and control applications as well. Those

applications include loop control, Roll Diameter, Tension Control, Winding and

Unwinding Control in Cloth weaving industries. Similarly, it is used in Liquid Level

Control, Thru Beam Detection for High Speed Counting, Full Detection, Thread or

Wire Break Detection, Vehicle Detection for Car Wash and Automotive Assembly,

Irregular Parts Detection for Hoppers and Feeder Bowls, Counting or Profiling Using

Ultrasonic System, Thickness Gauging, Web Break Detection, Quality Control

Inspection and so on.


17

CHAPTER THREE

Methodology

3.1 System architecture The main principle of measuring liquid level is to measure the time between the time of

transmitting and receiving of the reflected pulse from the liquid level surfaces. The total

time lapsed is double time period (i.e. the time required from transmitter to the liquid

level and reflected from liquid level to the receiver). So total time is divided by two, in

order to find out the duration of pulse on reaching liquid level. The calculation is

governed by the following relation.

2TvD ×= …(3.1)

Where,

D is distance between the receiver and liquid level (in meter)

v =Velocity of Ultrasonic Wave in Air (in meter per second)

T=Time Taken by the Ultrasonic Sound from Transmitter to Receiver (in second)

Figure 3.1: System Block Diagram


18

3.1.1 Transmission:

For the excitation of the ultrasonic transducer SQ40T, we need 40KHz pulse. The

generation of excitation pulse is done in following stages:

Generation of 40 KHz square wave

NE555 timer (astable mode) is used for the generation of the pulses with 50% duty cycle.

It generates 40 KHz square wave when enabled by the MCU. The purpose of using

NE555 is to generate the 40KHz frequency rather than the square wave.

Conversion of square wave to transducer exciting pulses

For this purpose the transistors and inverters are used. The square wave so generated has

logic level of 0V to 5V. In order to convert this logic to inverter compatible logic (0V –

9) we have used two transistors (BC547). Then the inverters are used to convert these

signals to increase the transmission power. The logic behind using these inverters is to

generate two different pulses 180 degree out of phase with each other, so that they can be

fed to the positive and the negative terminals of the transducer SQ40T.The transducer

SQ40T generates the 40KHz ultrasound by piezoelectric effect.

3.1.2 Reception

The receiver transducer SQ40R resonates at 40 KHz to receive only the transmitted

signal. The two major operations done after receiving signal after the receiver transducer

SQ40R are:

a. Amplification

b. Rectification

a. Amplification

Since the signal received at the transducer SQ40R is of low strength and even imposed

with noise, we need to amplify the signal. Thus, we have used LNA LM833N, which

rejects noise and amplifies the required signal.

The amplification is done in two stages with maximum gain of 60dB so that the signal

can be used for further processing.


19

b. Rectification

The amplified signal is then rectified by diodes 1N4002. We have carried out half wave

rectification to generate DC level of received signal.

3.1.3 Detection

Now the generated DC voltage obtained form rectification process is fed to comparator

LM358. This comparator is used to compare the DC level of received signal against

preset threshold value to generate high logic if signal is received otherwise low logic.

3.1.4 Signal Holding

In order to hold the logic level generated from detector or comparator SR flip flop is

used, so that MCU can acknowledge the received signal. The output of the latch is set to

low logic with the help of MCU initially to predefine the state of latch.

3.1.5 Pulse Shaping

To measure the flow the sine wave, the output of LNA is fed to pulse shaping circuitry

that uses single inverter of 74HC04. The output is square wave of logic level 0V to 5V

compatible with MCU.

3.1.6 Level calculation

MCU is used to observe the time elapsed between the transmitted and received signal.

This time is used to calculate the level of reflecting water surface.

3.1.7 Flow calculation

The pulse shaped signal from 74HC04 is fed into the MCU for measuring the frequency

of received signal. Then the frequency shift between the transmitted and received wave is

calculated and applied with Doppler’s effect to measure the velocity of water.

3.1.8 Display

The calculated level and flow of water is displayed on the 16 x 2 LCD which is low

power passive display device. (see Appendix A for LCD)


20

3.1.9 Wireless module

Finally, the information from site is delivered to the monitoring station using

commercially available RF modules and vice versa.

3.2 Description of components 3.2.1 Ultrasonic transducer

For the purpose of generating the ultrasound, we have used SQ40T as transmitter

transducer of ultrasound and SQ40R as a receiver transducer of ultrasound. Theses

transducer operates at their best at 40 KHz of AC signal. The transmitter is excited the

best, and at 18 V P-P of AC signal. Similarly, the SQ40R I more sensitive to frequency

of 40 KHz and can produce signal up to few hundreds milivolts after sensing ultrasonic

signal.

Figure 3.2 Back view of the SQ40T/SQ40R

3.2.2 8051 Microcontroller Microcontrollers are designed in a single chip, which typically includes a

microprocessor, certain byte of R/W memory, from 1K to 2K bytes of ROM, and several

signal lines to connect I/O lines. They are used in such functions as controlling

appliances and traffic lights. We have used ATMEL 89C51 microcontroller in our

project. Some features are summarized below:

• 8-Bit CPU Optimized for Control Applications

• Extensive Boolean Processing Capabilities (Single-Bit Logic)

• On-Chip Flash Program Memory

• On-Chip Data RAM


21

• Bidirectional and Individually Addressable I/O Lines

• Multiple 16-Bit Timer/Counters

• Full Duplex UART

• Multiple Source/Vector/Priority Interrupt Structure

• On-Chip Clock Oscillator

• On-chip EEPROM (AT89S series)

• SPI Serial Bus Interface (AT89S Series)

• Watchdog Timer (AT89S Series)

More detailed description of it is presented as below:

The microcontroller is the device that can perform various operations and computations

on the data. It consists of the arithmetic and the logic unit, I/O unit, control unit and other

various components.

The 8051 is the most popular microcontroller used today. Many derivative

microcontrollers have been developed which are based on and compatible with the

8051.To program an 8051 requires an important skill for one who plans to develop

product that will take advantage of microcontrollers. One of the 8051 based

microcontrollers is the most popular and widely used chip named as AT89C51.

The 8051 is an 8-bit machine. Its memory is organized in bytes and practically all its

instructions deal with byte quantities. It uses an accumulator as the primary register for

instruction results. Other operands can be accessed using one of the four different

addressing modes available:

• Register implicit

• Direct

• Indirect or immediate

Operands reside in one of the five memory spaces of the 8051. The five memory spaces

of the 8051 are:

• Program memory

• External Data Memory


22

• Internal data Memory

• Special Function Registers

• Bit Memory

The AT89C51 microcontroller includes 4k Bytes of In-System reprogrammable Flash

memory. Also 128*8-bit Internal RAM with 32 programmable I/O Lines. It consists of

two 16-bit Timer/Counters and six Interrupt Sources. The AT89C51 is a low power, high

performance CMOS 8-bit micro-computer with 4K bytes of flash programmable and

erasable read only memory. The on-chip Flash allows the program memory to be

reprogrammed in-system or by conventional nonvolatile memory programmer. By

combining a versatile 8-bit CPU with flash on a monolithic chip, the Atmel AT89C51 is

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

to many embedded control applications.

The AT89C51 provides the following standard features timer/counter, five vector two-

level interrupt architecture, full duplex serial port, on-chip oscillator and clock circuitry.

In addition, the AT89C51 is designed with static logic for operation down to zero

frequency and supports two software selectable power saving modes. The Idle Mode

stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system

to continue functioning. The Power-down mode saves RAM contents but freezes the

oscillator disabling all other chip functions until the next hardware reset.

Features of AT89C51:

• 4K bytes of In-system reprogrammable Flash Memory.

• Endurance: 1,000 Write/Erase cycles

• Fully static operation: 0 Hz to 24 MHz.

• Three level program memory lock.

• 32 programmable I/O lines

• 128 x 8-Bit Timer/counters.


23

• Six Interrupt Sources.

• Programmable Serial Channel.

• Low power Idle and Power Down Modes.

Pin Description:

Vcc

Supply voltage

Gnd

Ground

Port 0

Port 0 is an 8-bit open-drain bi-directional I/O port. So, it requires external pull up

resisters when used as simple I/O port. It is also designed as AD0-AD7 i.e. it can be

used for both address and data bus. When ALE = 0, it acts as data bus D0 –D7, but when

ALE = 1, it acts as address bus A0-A7. In our system, we have used Port 0 as the data

bus for the LCD.

Figure 3.3: AT89C51 IC pin description


24

Port 1 / Port 2

Port 1 / Port 2 both are an 8-bit bi-directional I/O port with internal pull-ups. Port 1 / Port

2 both acts as simple I/O when 8051 used with no external memory connection. But,

with the system with external memory connection, Port 2 acts as higher order address

bus along with the Port 0 to provide the 16-bits address for the external memory.

Port 1 is dedicated for the keypad while in case of Port 2, pin 2.1 used to enable the 555

timer, pin 2.2 used to enable/disable the latch in the circuit,pin2.7,2.6 & 2.5 used for the

control signaling of the LCD.

Port 3

Port 3 is also an 8-bit bi-directional I/O port with internal pull-ups. The port 3 output

buffers can sink/source four TTL inputs. When 1s are written to port 3 pins they are

pulled high by internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are

externally being pulled low will source current because of the internal pull ups. Port 3

also serves the function of various special features of the AT89C51 as listed below; Port

3 also receives some control signals for Flash programming and verification.

Port 3 also serves the functions of various special features of the AT89C51 as listed

below:

Port pin Alternate functions

P 3.0 RXD ( serial input port)

P 3.1 TXD ( serial transmit port)

P 3.2 INT0 ( external interrupt 0)

P 3.3 INT1 (external interrupt 1)

P 3.4 T0 ( timer 0 external input)

P 3.5 T1 ( timer 1 external input)

P 3.6 WR (external data memory write strobe)

P 3.7 RD ( external data memory read strobe)

Table 3.1: Port 3 Alternate function table


25

ALE/PROG

ALE (address latch enable) is an output pin and is active high, while connecting to an

external memory.

RST

RESET pin (i.e. pin 9) is an input pin and active high (normally low).

Where the high pulse must last for minimum of the two machine cycles before it goes to

low.Upon application of the high pulse, the MCU will be reset such that all the values of

its register will reset and program counter will be set to 0s.Infact, it is also referred to as

reset interrupt among the six interrupts available in 8051 MCU.

PSEN

“Program store Enable” is read strobe to external program memory. When the AT89C51

is executing code from external program memory, PSEN is activated twice each machine

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

memory.

EA/VPP

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

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

This pin also receives the 12-volt programming enable voltage during Flash

programming for two parts that require 12-volt VPP.

XTAL1

Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2

Output from the inverting oscillator amplifier.


26

3.2.3 Voltage Regulators

In our system we’ve used 7805&7809 as a voltage Regulators. It is a 3-Terminal

Regulator with Output Current Up to 100mA. It doesn’t require External Components It

has provision for Internal Thermal Overload Protection and Internal Short-Circuit

Limiting.

Figure 3.4: Minimum connection of 8051 MCU system

Figure 3.5: Pin description of voltage regulator 7805 & 7809


27

This 78xx series of fixed-voltage monolithic integrated-circuit voltage regulators is

designed for a wide range of applications. These applications include on-card regulation

for elimination of Noise and distribution problems associated with single-point

regulation.

The 7805 is most common and well-known of the 78xx series regulators, as its small

component count and medium-power regulated 5V make it useful for powering TTL.

3.2.4 Diodes

We have used silicon diodes 1N4001 in order to carry half wave rectification of the input

sine wave, to obtain its DC amplitude.

Figure 3.6: Figure showing input sine wave and its half wave

rectification using diodes.

Moreover, the diodes are also used as protection against negative voltage at the power

supply of circuit in reverse bias mode.

Figure 3.7: Negative voltage protection in the circuitry using diode


28

3.2.5 Line driver or Voltage translator

As a Line driver IC we have used the MAX232 IC in our system. It operates with Single

5-V Power Supply. The MAX232 device is a dual driver/receiver that includes a

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

Each receiver converts EIA-232 inputs to 5-V TTL/CMOS levels. These receivers have a

typical threshold of 1.3 V and a typical hysteresis of 0.5 V, GND and can accept ±30-V

inputs. Each driver converts TTL/CMOS input levels into EIA-232 levels. The MAX232

is characterized for operation from 0°C to 70°C. The MAX232I is characterized for

operation from –40°C to 85°C.

Since both 8051 MCU and computer are DTE, the communication between them can be

done with RS232 standard using MAX232 and null modem or virtual modem

configuration. Each DTE acts as virtual modem to other DTE.

3.2.6 DC socket

A DC connector is a electrical connector for supplying direct current (DC) power. DC

connectors are poorly standardized, compared to domestic AC power plugs and sockets.

DC plug is a common name used for one common type of cylindrical two-conductor

plug

Figure 3.8: Line driver MAX232


29

Figure 3.9: Null modem

available in a range of sizes and used to power small pieces of electronic equipment.

Several competing standards exist for DC plugs, and in some cases incompatible plugs

will fit together, or can be made to fit, possibly damaging equipment if the voltage is

wrong, the polarity is wrong, current ratings are exceeded, power supply filtering or

stability is inadequate for the equipment being powered.

The intended use of these plugs is on the cable connected to a power supply. The

matching jack or socket is then mounted in the equipment to be powered

3.2.7 LM833

The LM833 is a dual general purpose operational amplifier designed with particular

emphasis on performance in audio systems.

This dual amplifier IC utilizes new circuit and processing techniques to deliver low

noise, high speed and wide bandwidth without increasing external components or

decreasing

stability. The LM833 is internally compensated for all closed loop gains.

The LM833 is pin-for-pin compatible with industry standard dual operational amplifiers.

It has:

• High gain bandwidth: 15MHz (typical); 10MHz (min)


30

• Wide power bandwidth: 120KHz

Figure 3.10: Dual 8 pin Opamp

The gain bandwidth product (GBW or GB) for an amplifier is the product of the open

loop gain (constant for a given amplifier) and its 3 dB bandwidth. This quantity is

commonly specified for operational amplifiers, and allows circuit designers to determine

the maximum gain that can be extracted from the device for a given frequency (or

bandwidth) and vice versa.

Understanding the meaning of gain bandwidth product (GBWP)

If the GBWP of an op-amp is 1 MHz, it means that the gain of the device falls to unity at

1 MHz. Hence, when the device is wired for unity gain, it will work up to 1 MHz

(GBWP = gain x bandwidth, therefore if BW = 1 MHz, gain = 1) without excessively

distorting the signal. So by simple mathematics, for 40 KHz, the gain will be 25. Further,

if the maximum frequency of operation is 1 Hz, then the maximum gain that can be

extracted from the device is 6101×

We have used both opamps of LM833 for amplifying weak signal from transducer.

An opamp has the 1

2

RRGain −= in above configuration. So with the help of feed back

resistor we can vary gain easily.


31

Figure 3.11: Non inverting configuration of an amplifier

3.2.8 LM358

The LM358 consists of two independent, high gain; internally frequency compensated

operational amplifiers which were designed specifically to operate from a single power

supply over a wide range of voltages.

Application areas include transducer amplifiers, dc gain blocks and all the conventional

op amp circuits which now can be more easily implemented in single power supply

systems

The schematic and pin configuration of LM358 is same as that of LM833 as shown in

figure 3.10 above.

3.2.9 CD4011

The CD4011BC quad gates are monolithic complementary MOS (CMOS) IC

constructed with N- and P-channel enhancement mode transistors.

The devices also have buffered outputs which improve transfer characteristics by

providing very high gain. All inputs are protected against static discharge with diodes to

VDD and VSS.

We have used three NAND gates to realize SR-FF.


32

Figure 3.12: Quad NAND gate IC

Each of the gates performs the same function as shown in figure 3.13.

Figure 3.13: Logical symbol and truth table of NAND gate

3.2.10 CD4069

The CD4069 is a six NOT gate having IC, used for inverting logic in a electronic circuit

between 0V and 9V.

In our circuitry we have used the inverting property of NOT gate to generate excitation

pulse for transducer.


33

Figure 3.14: Six NOT gates IC

3.2.11 74HC04

The 74HC04 is also a six NOT gate having IC used for inverting logic between 0V and

5V. In our circuitry we have used it to produce active low logic when signal is detected,

as interrupt of MCU is active low and the gates are also used for pulse shaping. The

schematic of 74HC04 is same as that of CD4069 as in figure 3.14. The working on each

NOT gate can be summarized as follows:

Figure 3.15: Logical symbol and truth table of NOT gate


34

3.2.12 555 timer

It is a 8 pin special IC designed for the purpose of generating square wave by connecting

the proper connecting elements. With the help of variable resistors, we can generate

square wave at different frequency.

It is used to generate the signal of 40 KHz which is the frequency of ultrasound to be

excited as implement in our system.

Figure 3.16: 555 timer configuration to generate square wave.

3.2.13 LCD

The LCD, liquid crystal display, is used for the Displaying of the information at the site’s

circuit. It displays the level, flow values and plays the role for interfacing with the user at

site. For detail information about LCD(see Appendix A).

3.2.14 RF modules

RFM12B has been used as transceiver to communicate with monitoring station and the

site. It works on the signal ranges from 433/868/915 MHz. The SPI interface is used to


35

communicate with the microcontroller for the various parameter settings like baud rate,

clock rate, modes, carrier frequency etc. The RF modules are shown in the figure 3.17

below.

Figure 3.17: RF modules

Note: For further detail about the components described in section 3.2 refer to the CD

attached herewith, which contains the datasheets of the used components. Further, refer

the Books and site as mentioned in the References.


36

3.3 Circuit Explanation 3.3.1 Power supply circuit:

We have used 7805 and 7809 IC for power supply in our system, as some IC operate in

9V while some at 5V.

Also decoupling capacitor are used in the IC’s input and output to filter out ripples in

source.

Figure 3.18: Voltage regulators

3.3.2 Transmission section

a. 555 timer

Here, according to pin 4 of 555 is enabled /disabled by MCU, the 555 timer in astable

mode configuration generates square wave of 40 KHz.

The value of components for generating 40 KHz wave is:

R1=10K

R2 = 13K

C = 102 p

C )RR (R

1.44 frequency 321

×++

= …(3.2)


37

b. Transistors and inverters

Signal from 555 timer is fed to two points:

i) Through the NAND gate, then to the transistor

ii) Directly to the base of next transistor.

The transistors are in inverting mode, thus they amplify the current. At the same time

since the transistors is working in (0-9)V logic thus there is power of signal. Now, the

outputs from the collector of the two transistors are fed to the CMOS inverters (which

are capable for high frequency switching).

Figure 3.19: Astable mode of 555 timer

Then, the two square wave signal 180º out of phase with each other, are fed to the

positive and negative terminal of transducer. The capacitor C is used to block any DC

noise in the excitation signal.

3.3.3 Reception section

The received signal by SQ40R is of very low strength. Statistically on receiving

ultrasound, the signal measured is of frequency 40 KHz with (60-130) mV peak to peak

amplitude. Now, this received signal is further processed as:


38

a. Coupling the signal

The resistor R is used to GND any DC level in the received signal; C is used to couple

the high frequency ultrasound signal.

b. Amplifying the signal

For amplification, we have used the LNA LM833N.This is a two-opamp IC operating at

9V. Here, we carry amplification in two stages in inverting mode of opamp. The gain in

the signal can be varied 10 times to 1000 times i.e. 20dB to 60dB.The first stage gain can

be varied from 1dB to 60dB, whereas the second stage gain is fixed to 20dB.

Figure 3.20: Circuit to excite ultrasonic transmitter

Here, amplification is not done in reference to 0V. As the IC operates in (0-9)V logic so

if we amplify at 0V the signal will go below 0V ,hence experience the clipping .So, we

have carried out amplification at reference of 4.5V, so that even signal of 9V peak to

peak , there won’t be clipping if we adjust gain properly. Since the opamp has negative


39

feedback, the voltages at the positive and negative terminals are equal. This is called

virtual GND .So, with this configuration of bipolar signal can be amplified even if the

opamp operates in single mode power supply.

This technique is very useful when we need full wave signal, while we are using opamp

in single mode power supply. So, after amplification we get the signal of frequency 40

KHz with (5-8) V peak to peak amplitude.

c. Signal rectification

Now, the sinusoidal signal after amplification is half wave rectified using the diodes

1N4001, to obtain the DC value of the amplified signal. The output of the signal

rectification is DC signal of (4-8) V. Although, the half wave rectification could be

carried out using single diode but the diode that is grounded is used to provide complete

path for negative cycle of input wave.

3.3.4 Signal detection

Noise is inevitable in any system, so our system is also prone to noise due to the

interference from various sources like RF, microwave emitting sources etc. But, we have

been able to discriminate noise against signal through proper filtering techniques.

Experimentally, we have observed that that noise DC level doesn’t rise above 2.5V in

our environment.

The signal detector is LM358 as comparator.LM358 has two opamps. We have used one

opamp in comparator mode where:

i) Changing voltage is applied to positive terminal

ii) Reference voltage is applied to the negative terminal

The opamp in comparator mode has no feedback, so theoretically gain is infinite. Now, if

the input at the non-inverting terminal becomes a more positive than the negative

terminal(with reference voltage), the output should have been in kilo-volts . But this is

limited by the biasing voltage of opamp. In our case the IC works in (0-9) V logic thus

output can only saturate to 9V.


40

The reference voltage is calculated as follows:

( )⎟⎟⎠

⎞⎜⎜⎝

⎛+

×=ba

ccbrf RR

VR V …(3.3)

(a)

(b)

Figure 3.21: Opamp as comparator

(a) Circuit diagram

(b) Timing diagram

We have used Rb as variable resistor, so as to change the reference voltage as per need

by experimenting.

The DC level obtained from rectification stage is fed to the non–inverting terminal of

comparator and compared against reference level of 3V.So, the output of the comparator


41

is logic 1(9V) for signal and logic (0V) for noise in the environment. The resistor Ro at

the output is used to change the (0-9)V logic to (0-5)V logic as our next stage IC

operates on (0-5)V logic.

a. Signal holding

We have used SR-FF for holding the received signal as shown in figure 3.22. The logic

level 1 generated by the signal detecting circuit appears for very short time, so MCU

may not be able to acknowledge it Thus, in order to hold that signal for MCU , we have

used latch circuitry.

In order to pre-define the output of the latch we hold the input at ‘Z’ low, so that output

of the latch is low independent of input at ‘W’. Signal at ‘Z’ is changed to high state only

after ultrasound is transmitted by system, which makes the output of latch dependent

only on the input ‘W’. This helps to avoid false triggering.

We have used three NAND gates of CD4011 IC in order to realize the latch.

The output of the latch is finally fed to the MCU after inverting it, as the interrupt of

MCU is active low. We have also used pull down resistor after the inverter before

feeding the signal to MCU; so as to properly set the logic levels (i.e. avoid floating

logic).

b. Pulse shaping

In order to find the flow of water, we need to find the frequency of the reflected signal

for which we need a MCU compatible pulse. So, in order to convert the amplified sine

wave from LM833 to MCU compatible square wave having logic levels (0-5)V, we used

following circuitry.

(a)


42

(b)

Figure 3.22: SR FF

(a) Circuit Diagram

(b) Timing diagram

Figure 3.23: Pulse shaping circuit


43

This circuit is similar to Schmitt trigger operation. This is comparator application which

switches the output negative when the input passes upward through a positive reference

voltage and output positive when the input passes downward through a positive reference

voltage.

The Schmitt trigger is also the comparator application which switches the output

negative when the input passes upward through a positive reference voltage. It then uses

negative feedback to prevent switching back to the other state until the input passes

through a lower threshold voltage, thus stabilizing the switching against rapid triggering

by noise as it passes the trigger point.

But we didn’t use the Schmitt trigger because it was more convenient to generate square

wave using hex buffer 74HC04.


44


45

(b)

Figure 3.24: (a) Schematic of circuit at site

(b) Schematic of circuit at monitoring station.

3.4 Program in system


46

3.4.1 Flow Chart

The flowcharts described below are not the entire flowchart of the system. Rather, the

level and flow finding flowcharts have been described separately. So that, it gives the

central idea of the program to find level and flow of the flowing water.

Flow chart for level

The flowchart shown in figure 3.25 describes the method to find the level of the moving

water. To find level, first the ultrasonic wave is transmitted from the ultrasonic

transmitter transducer. At that mean time a timer is started. This timer belongs to the

internal timer of the MCU. Then, we wait for the reflected wave from water surface to be

received by the ultrasonic receiver transducer. As the receiver receives the reflected

wave the timer that started earlier is stopped. Now, the timer register of the timer will

have the time (∆T) that elapsed for the transmitted wave to be received after the

reflection from the water surface.

Now with the help of this time, the level of the water is found using formula described in

flowchart figure 3.22. For detail about calculating the level of water see section 3.4.2

resolution calculation of level.

Flowchart for flow

The flowchart shown in figure 3.26 describes the method of finding the flow of the

moving water. To find the flow, first the ultrasound wave is transmitted. As the reflected

wave start receiving the frequency of the received wave is calculated and the frequency

shift there after. Now, the value of frequency shift is employed in the formula shown in

flowchart figure 3.26 to find out the velocity of moving water. For detail about

calculating the flow of water see section 3.4.2 resolution calculation of flow


47

Figure 3.25: Flowchart for Figure 3.26: Flowchart for level calculation flow calculation


48

Overall Flowchart

The flowchart shown in figure 3.27 describes the entire flow of system. Before

proceeding to the flowchart some of the terms used in the flowcharts are described

below.

Lvl_flw_flag is flag to indicate level or flow of water to be measured.

Wave_40k is the control signal to excite or stop the generation of 40KHz of wave

Latch is the enable / disable signal for the latch (SR flip flop) in the circuit.

Lvl_count keeps the record of measured level of the water

Lvl_flag is the flag to indicate the final value of level

Pulse_counter is the counter to count the number of square pulses have been received.

Flow keeps the record of measured flow of the water


49

START

Greeting MessageDisplay

Waiting for stationCommandi.e. SerRx()

Display “invalid

command”

Is It handover To station

i.e H?

Call Subroutine Site_control

Is It to find Level

“L”?

IsIt to find Flow

“F”?

Call Subroutine Find_level

Call SubroutineFind_flow

YES YES YES

NO NO NO

IsLevel exceeds

Threshold Value?

Is Flow exceeds

ThresholdValue?

BUZZER ON

BUZZER OFF

YES

YES

NO


50

Sub routineSite_control

User Authentication

Wait for site commandi.e Key()

Is It handover

ToStation?i.e “H”

Is It to find level?

“L”

Is It to find

flow?“F”

DisplayInvalid

command

Call subroutineFind_level

Call SubroutineFind_flowReturn

YES

NO

YES

NO

YES

NO

IsLevel exceeds

Threshold Value?

Is Flow exceeds

ThresholdValue?

BUZZER ON

BUZZER OFF

YES

NONO

YES


51

SubroutineLEVEL

Set timer0 in Mode2With

TH0 = E3 (resolution)

Enable interrupts timer0 & External

interrupt 1

Reset level valuesLvl_count = 0Lvl_flag = 0

Start transmitting wave as Wave_40k = 1

&Latch = 1

Start timer0

IsLvl_flag = 1?

Is External interrupt1

Occurred?

Is Timer0 interrupt

Occurred?

Disable interrupts

AsEA = 0

Also transmit it to the monitoring

station

return

Display lvl_count as required level

On LCD

Call ISRINT1

Call ISR T0

NO

YES

YES

NO

YES

NO

ISRINT1

Stop Timer0

Dpt_flag = 1

Wave_40k = 0Latch = 0

return

ISRT0

Increase Lvl_count by

1

Return


52

SubroutineFLOW

Pulse_Counter = 0Enable External

interrupt 0

Set timer0 in Mode1 with

TH0 = 0,TL0 =0

Wave_40k = 1

Is External interrupt

0Occurred?

Call ISRINT0

If pulse_counter

= 1

Start timer0 as TR0 = 1

A

A

Is External

Interrupt 0Occurred?

Call ISR INT0

IfPulse_Counter

=1001

Stop Timer0

Flow = TH0 x 256 +TL0

Flow = | flow – 25000 |

Flow = Flow x 1.3 (i.e resolution)

B

YES

NO

YES

NO

YES

NO

NO


53

Figure 3.27: Overall Flowchart of the system

3.4.2 Resolution calculations

The resolution of any device implies the ability of that device to measure the smallest

possible value any quantity. This section of the resolutions describes the resolution

calculation of level and flow in detail. Moreover, it also gives a brief idea about how the

level finding formula 3.1 and flow finding formula of equation 2.16 have been exploited

in the MCU programming.

Resolution calculation of level

From the formula of velocity, we have

tD v =

Where,

v = velocity of sound in m/s

D = distance traveled

t = time taken to travel distance D

vD t , =or


54

For, 1 cm of resolution for level

D = 1 cm

v = 340 m/s (assume)

Such that, t = 0.01/340

= 29.41 µs

Hence, it shows that to travel 1 cm of distance by ultrasound it takes 29.41 µs.

Now, the query comes into play, how to implement above fact by microcontroller

AT89C51 with 11.0592 MHz of crystal frequency?

We know that,

AT89C51 with 11.0592 MHz of crystal has machine cycle of period 1.085 µs,

So, The Number of machine cycle (MC) required to represent 1 cm is given as

Number of MC = ss

µµ

085.141.29

≈ 27

So, if we increase any variable depth (say) by one at each elapsed of 27 MC from the

time we send the burst of pulses until it is received; we finally come up with the required

value of distance stored in variable level.

Then, what is the minimum distance that can be measured with AT89C51 with crystal

11.0592 MHz?

We have,

Distance = velocity of sound * time elapsed

So,

Minimum Distance = Velocity of sound * possible minimum time- elapse that can be

detected by MCU

= 340 m/s * 1.085 µs

= 3.689 * 10-4 m

= 0.36 mm


55

Hence, the minimum distance that can be measured by AT89C51 with 11.0592 MHz of

crystal is 0.36mm.

Resolution Calculation for flow

From the equation 2.17 we have,

⎟⎟⎠

⎞⎜⎜⎝

⎛−×= 1

TT

v vrx

txs0

Where,

0v = velocity of a moving object

sv = velocity of sound

txT = time to send 1000 burst of pulses of 40 KHz

= 1000 x 25µs

= 25000µs

rxT = time to receive 1000 burst of reflected wave (which is shifted by Doppler Effect

around 40KHz)

Now minimum velocity that can be measured or resolution for flow:

⎟⎠⎞

⎜⎝⎛ −×= 1

2499925000 340 v0

= 0.013600544 m/s

= 1.3 cm/s

Moreover, the resolution can be increased by increasing the number of pulses as

illustrated in example below:

For example, if the 2500 burst pulses of 40 KHz is considered. Then

txT = 2500 x 25µs

= 62500 µs

Such that,

⎟⎠⎞

⎜⎝⎛ −×= 1

6249962500 340 v0

= 5.44 x 10 -3ms-1 = 5.44 mm/s

This indicates the flow having the resolution of 5.44mm/s.


56

3.5 Serial Communication

The data I/O of the PC depend upon the Microprocessor Architecture. It can employ

Memory Mapped I/O or I/O Mapped I/ O. In I/O Mapped I/O, the devices are identified

with the separate I/O address. The maximum numbers of devices in this approach that

can be well addressed depends upon the number of data bits in the Microprocessor

Architecture Design. For example 8 bit architecture in 8085 can address up to 256

devices using this approach. The data transfer for this approach is faster than the

Memory Mapped I/O because there is no need to go to memory address to fetch operands

time and again. However, the number of devices that can be addressed is limited and

small range than the Memory mapped I/O. The instructions such as IN and OUT are

used.

In Memory Mapped I/O, the devices are treated like the memory locations. The

addressability of I/O devices is much high and is determined by the number of Bits in the

Address Bus. The memory instructions such as LDA, STA, LDAX, STAX, are used for

data I/O in such approach.

Data transfer can occur in either of the two ways: Serial and Parallel data transfer in

synchronous and asynchronous mode. .Asynchronous mode is often used in data

communication between PC and the peripherals because of higher speed of the processor

than the peripheral devices in general. The asynchronous data transfer takes place bitwise

or character wise. The start bit, stop bit, parity bit are used for baud rates that is fixed to

be same at the both transmitting side and receiving side. UART such as Motorola’s

MC6850 is used for asynchronous data communication.

In synchronous mode there is provision of synchronization between the transmitter and

the receiver. The receiver can respond to the varying clock rate of the transmitter and the

data transfer takes place block wise rather than character wise. The start bit, stop bit and

parity bits are also used. The USRT chips are used for synchronous mode of data

communication.


57

In Parallel data transfer a number of lines are used to transfer a word at a time. This

technique is faster than the serial data communication technique however it is suitable

for short distance communication only. The printers and such peripherals use

parallel data transfer.

In serial data transfer a single line is used to transfer a bit at a time. This technique is

slower than parallel data transfer however highly economical. It is used for long distance

communication such as in internet. Most of the time serial data communication is of

interest. The signal high is indicated by MARK and the signal low level is called

SPACE. There are different protocols to govern the serial data transfer such as RS 232 C

(Now called as EIA-232), RS 423A and RS 422A that was developed in 1960s.]

Figure 3.28: waveform of serial data unit

3.5.1 Serial data communication in MCU

In Microcontroller there is one inbuilt chip called USART (Universal Synchronous

Asynchronous Receiver and Transmitter) that facilitates both the synchronous and

asynchronous data communication. The TXD (pin 11) and RXD (pin 10) of

AT89C51/AT 89C52 microcontroller are used for the serial communication purpose. In

this project we have implemented serial communication in polling mode rather than in

interrupt mode since we don’t need high speed of operation and we didn't have to mind

for the CPU Utilization Factor.

The PC side VB interface is used for fixing the data rate (asynchronous) half duplex

communication. There is the provision of setting the values of auto mode and manual


58

mode tracking. The data is wirelessly transmitted by the RF Transmitter at the site and

Received at the monitoring system by the RF receiver and finally to the PC via serial

Port.

3.5.2 RS232 Protocol

The protocol governing the serial communication in our case is RS232C.Some Features

of RS 232C Standard are listed below:

• EIA Standard 232 developed in early 1960s

• RS 232C in late 1960s.

• .Named as EIA-232C later however most commonly called RS 232C.

• Describes the function of 25 signal and handshake pin for serial data transfer.

• Describes the voltage levels, impedance levels, rise and fall times, maximum bit

rate and maximum capacitances for these signal lines.

• Connector should have 25 pins, the DTE should be Male and the DCE should be

female. However IBM reduced these 25 pins to 9 pins that are often required for

asynchronous communication. Those connectors are DB25 and DB9 connectors

respectively.

• Voltage levels: +3V to +15V->logic "0" For logic Low

-3V to -15V->logic "1" For logic High

-3V to +3V->Transition region (often avoided).

• Commonly used standard is: +12V for logic "0"

-12V for logic "1"

• The signal direction is specified with respect to the DCE (Data communication

Equipment).

• Both Chasis ground (pin 1) and Signal ground (pin 7) are available. To prevent

large AC induced ground currents in the signal ground

these two should be connected together only at the power supply in the terminal or

computer.

• TXD (pin 2), RXD (pin 3) make handshake signals for primary forward

communication channel.

• Most frequently used pins signals and the description is given below:


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25 pin 9 pin Signal Direction Description

1 - - - Protective Ground

2 3 TD DTE→DCE Transmitted data

3 2 RD DCE→DTE Received Data

4 7 RTS DTE→DCE Request to send

5 8 CTS DCE→DTE Clear to Send

6 6 DSR DCE→DTE Data set Ready

7 5 DCD DCE→DTE Data Carrier Detect

8 1 DTR DTE→DCE Data terminal Ready

20 4 RI DCE→DTE Ring Indicator

22 9 DSRD DCE↔DTE Data Signal Rate Detector

Table 3.2: Pin description of DB-9 connector and its relation with the

DB- 25 connector with respect to pins

With these signal connection we can establish simplex, half-duplex and full-duplex

asynchronous communication. The connection between both DTEs can be emulated by

the careful examination of these signals such as Null Modem. we have used Half-duplex

communication in our project. Since 232C Standard is very old and not compatible with

the PC we have used MAX 232ACP IC (Line Driver/Translator) for the TTL

compatibility.

3.6 Software & Equipments

This section is intended to give some basic introduction and useful information about the

software and tools that we employed in to develop our system.

3.6.1 Proteus 6 Professional

Many CAD users dismiss schematic capture as a necessary evil in the process of creating

PCB layout but Proteus 6 Professional has always disputed this point of view. With PCB


60

layout now offering automation of both component placement and track routing, getting

the design into the computer can often be the most time consuming element of the

exercise. And if you use circuit simulation to develop your ideas, you are going to spend

even more time working on the schematic.

ISIS has been created with this in mind. It has evolved over twelve years research and

development and has been proven by thousands of users worldwide. The strength of its

architecture has allowed us to integrate first conventional graph based simulation and

now - with PROTEUS VSM - interactive circuit simulation into the design environment.

For the first time ever it is possible to draw a complete circuit for a micro-controller

based system and then test it interactively, all from within the same piece of software.

Meanwhile, ISIS retains a host of features aimed at the PCB designer, so that the same

design can be exported for production with ARES or other PCB layout software.

The Proteus Professional v 6.9, Lab Center Electronics 1990-2005, has been used for the

simulation and PCB layout designed purpose in our system. And this software proved to

be the most comprehensive tool for testing many microcontroller based circuitry with

MCU coding, of course and it has also helped to give professional look to our circuit.

Proteus used in Simulation

We have used the Proteus ISIS professional to carry out the simulation of our design and

checking the corrective ness of the coding done in C language. The library of the ISIS

was rich in the commercially available ICs, which proved to be fruitful for us to check

the output of circuit at various conditions and to check the feasibility of any new

components to be added in the systems.

During the simulation of our system, ISIS had been very useful to test the code from the

very beginning. As the Proteus ISIS professional don’t have simulation facility for the

ultrasonic transducers we had to test the entire code of the system by providing the

induced interrupts by the use of buttons for level interrupt and Digital clock generator for

the flow interrupt as shown in the figure 3.29 below.


61

Figure 3.29: Snap shot of simulation circuit to test the code in Porteus ISIS

professional

Proteus used in PCB design:

We have used the Proteus ARES professional for the PCB design. The design of PCB

was employed manually rather than using the self routing tool ELECTRA available in

ARES.


62

Figure 3.30: Designed PCB layout

3.6.2 MCU Programming in C

The programming of MCU is done in Assembly language, C language etc. Among then

we have chosen C language programming instead of Assembly language programming

due to the various reasons as explained followings:


63

When compliers complies the code written in C language to produce Hex files, that

loaded into the ROM of MCU. The size of HEX file is larger with respect to the HEX

file produced by the program written in assembly language.

As MCU has limited on chip ROM. For example AT89C51 MCU has only 4KB of

ROM. Moreover, memory can only be extended up to 64KB as address bus used is of 16

bits.

Hence, the size of HEX file produced by the complier is the major issue while writing

the code in MCU.

Assembly language Vs C language

In spite of the problem explained above while doing the MCU programming in C

language, we chose C language because the assembly language is tedious and time

consuming while the C language is much easier and less time consuming to write

program. Furthermore, program in C sis easier to modify, update and more importantly

to debug. C language also allows us to use codes available in function libraries.

C data types for MCU

This sections attempts to review some of the widely used C data types in MCU. The

section explain how the proper use of C data types is carried out, such that the

programmer would be able to produce small size of HEX file as much as possible.

Unsigned char: The unsigned char is an 8 bit data types that takes the value in the range

of 0-255 (00-FFH). It is most widely used data types for MCU. By default, C compilers

assume as signed char if we don’t put keyword unsigned in front of char. it is also used

for the ASCII character as genuinely used in C language.

Signed char: It is also an 8 bit data type using D7 among (D7-D0) of 1 byte data to

represent the ‘+’ or ‘-‘ sign of the magnitude, such that there are only 7 bits for the

magnitude of signed numbers giving range of (-128 to 127). This data types is used

where the sign of the magnitude becomes vital.


64

Unsigned int: When the values of variables exceed 256 then the unsigned int comes into

play. This is 16 bits data type giving the range of 0 – 65535 (0000 – FFFFH), it occupies

2 bytes of RAM space of MCU. Hence, misuse of this data type will result in

unnecessary increase in size of HEX file.

Signed int: It uses D15 bit of (D15 – D0) data to represent sign as described in case of

signed char, giving the magnitude range of (-32,768 to +32767)

Finally, it can be concluded that when the variables are declared during programming the

MCU in C language,

• The programmer should drag his/her attention to the size of the data types & its

intended use.

• There should not be unnecessary declaration of variables, i.e. no redundant

declaration or optimum use of the declared variable.

If one takes care of the above mentioned point then s/he will be able to mitigate the size

of HEX files effectively.

3.6.3 SDCC compiler

SDCC (Small Device C Compiler) is free open source, retarget table; optimizing ANSI-

C compiler by Sandeep Dutta designed for 8 bit Microprocessors. The current version

targets Intel MCS51 based Microprocessors (8031, 8032, 8051, 8052, etc.), Dallas

DS80C390 variants, Freescale (formerly Motorola) HC08 and Zilog Z80 based MCUs. It

can be retargeted for other microprocessors, support for Microchip PIC, Atmel AVR is

under development. SDCC has extensive language extensions suitable for utilizing

various microcontrollers and underlying hardware effectively. The Supported data-types

are: bool, char, short, int ,long, float

Compiling in SDCC

For single source file 8051 projects the process is very simple. Compile your programs

with the following command "sdcc sourcefile.c". This will compile, assemble and link

your source file. Output files are as follows:


65

sourcefile.asm ,sourcefile.lst , sourcefile.rst , sourcefile.sym, sourcefile.rel or

sourcefile.o, sourcefile.map, sourcefile.mem, sourcefile.ihx , sourcefile.adb,

sourcefile.cdb, sourcefile. - (no extension) .

Post processing the Intel Hex file

In most cases this won’t be needed but the Intel Hex file which is generated by SDCC

might include lines of varying length and the addresses within the file are not guaranteed

to be strictly ascending. If your tool chain or a boot loader does not like this you can use

the tool packihx which is part of the SDCC distribution:

packihx sourcefile.ihx >sourcefile.hex

Now the Sourcefile.hex is loaded in the ROM of MCU using the software EZ-

Downloader v4.1 as shown in figure 3.31

Figure 3.31: snap shot of outlook of EZ-Downloader

for example:

let us consider we have written a code in notepad and saved it as ultrasound.c.

then first we enter into the command prompt and further enter into the correct path where

the ultrasound.c is saved in.

next we type “sdcc ultrasound.c”

then”packihx ultrasound.ihx>ultrasound.hex”

now ultrasound.hex is available to be loaded into the ROM of MCU. This process is

illustrated in figure 3.32 below.

Note: while declaring the array of unsigned char, put “code” before variable name as:

unsigned char code var_name[ ]. This will compile the var_name[ ] in separate code

memory, such that internal memory (127 bytes) scarcity will not occur.


66

Figure 3.32: Compiling ultrasound.c using SDCC

3.6.4 Visual basic 6.0 The PC Motoring Station in our project interfaces the user via VB 6.0 interface. Visual

Basic provides a complete graphical user friendly interface with its integrated

development environment. This development environment has many tools, applications

and even the wizard for the development for frequent applications.

The Visual Basic Environment provides users facilities to build many applications. This

allows users with even little programming knowledge and experience to build strong and

useful applications. Many Object Linking and Embedding OLE; Active Controls can be

added for versatility in the program. Programs such as Excel Spreadsheet can be

embedded to develop programs that can be used in Front End Applications to a Back

End (database )system , serving as the user interface which collects user input and

displays the processed output in more appealing and interesting way. The SQL is used to

bind the front end and the back end in our application.

Much of the outline code is generated by VB such as drawing line, Box, Color Setting,

Formatting the objects and therefore the programmer has no overhead of extra coding

other than the main event triggered coding. The main objects of VB are Form, The

Buttons, Text areas, Menus, Dropdown list, Controls etc. The graphical interface and

Tools, Running Compiling and Debugging are easily accomplished.


67

Serial Communication is mainly used in our PC Monitoring station. This allows the

incoming information from the remote site location to the Monitoring Station and vice

versa. The form takes the input of auto-mode time setting value and has the display for

the retrieved data from the site for the flow and level of the liquid. Some alarming

provision is also added. Further, our program has the database of the Real Time Data

retrieved from the site and also has capability to plot the latest 10 values via the Bar

Diagram which helps to interpret and statistic analysis. Further, Site Control signals are

also generated.

(a)

(b)

Figure 3.33: Snap shot of interfacing Form designed using

Visual Basic (a) Manual Mode (b) Auto Mode


68

Figure 3.34 : Plots of measured values of level and flow

3.6.5 0scilloscope

An oscilloscope (sometimes abbreviated CRO, for cathode-ray oscilloscope, or

commonly just scope or O-scope) is a type of electronic test equipment that allows signal

voltages to be viewed, usually as a two-dimensional graph of one or more electrical

potential differences (vertical axis) plotted as a function of time or of some other voltage

(horizontal axis).

One of the most frequent uses of scopes is troubleshooting malfunctioning electronic

equipment. One of the advantages of a scope is that it can graphically show signals:

where a voltmeter may show a totally unexpected voltage, a scope may reveal that the

circuit is oscillating. In other cases the precise shape of a pulse is important.

In a piece of electronic equipment, for example, the connections between stages (e.g.

electronic mixers, electronic oscillators, amplifiers) may be 'probed' for the expected


69

signal, using the scope as a simple signal tracer. If the expected signal is absent or

incorrect, some preceding stage of the electronics is not operating correctly. Since most

failures occur because of a single faulty component, each measurement can prove that

half of the stages of a complex piece of equipment either work, or probably did not cause

the fault.

Once the faulty stage is found, further probing can usually tell a skilled technician

exactly which component has failed. Once the component is replaced, the unit can be

restored to service, or at least the next fault can be isolated.

Another use is for software engineers who must program electronics. Often a scope is the

only way to see if the software is running the electronics properly.

Another use is to check newly designed circuitry. Very often a newly designed circuit

will misbehave because of design errors, bad voltage levels, electrical noise etc. Digital

electronics usually operate from a clock, so a dual-trace scope which shows both the

clock signal and a test signal dependent upon the clock is useful. "Storage scopes" are

helpful for "capturing" rare electronic events that cause defective operation.

3.6.6 Digital multimeter

Digital multimeter usually employ an electronic circuit that acts as an integrator, linearly

ramping output voltage when input voltage is constant (this can be easily realized with

an opamp). The dual-slope integrator method applies a known reference voltage to the

integrator for a fixed time to ramp the integrator's output voltage up, then the unknown

voltage is applied to ramp it back down, and the time to ramp output voltage down to

zero is recorded (realized in an ADC implementation). The unknown voltage being

measured is the product of the voltage reference and the ramp-up time divided by the

ramp-down time. The voltage reference must remain constant during the ramp-up time,

which may be difficult due to supply voltage and temperature variations.


70

3.7 Problem faced During the period of the project, we have come across the lots of genuine problem that

are encountered in any project. So, those problems have not been addressed here. Rather

the major problems of our project have been described here.

Problem in Hardware

As hard to theoritize any concept, much harder is to realize the system with electronic

component. The commercially available ICs and other components don’t operate with

expected reliability.

The simplicity in the circuitry seems that it is a single day work to complete the project.

But after starting, one will experience what obstacles might one face in the course of

making a system synchronizing hardware and software. It is simple to realize the

circuitry module wise during the first attempt, if you are lucky. However, one can

succeed in realizing modules with several serious attempts. For instant, talking about

power supply. It is full of spikes which if used directly may damage the ICs used. So, use

of decoupling capacitor is mandatory.

We started our circuitry design in "bread board" which has a lot of errors in itself. In

order to overcome unseen resistances and leakages that can occur in breadboard, we

switched to realize the circuitry with dot-matrix board. But this proved to be a nightmare.

It took days to build the circuitry which caused massive loss of precious time. At the

same time, the dot-matrix board proved to be further noisier. The initial build was neat

and clean. But as the circuit didn't work so we had to replace the live wire without

removing the insulation plastic. Finally after use a lot of jumpers, replacing and

displacing, the circuit started working. But it took three days to complete the circuitry

and even longer (five days!!) to debug it, for proper working.

Finally we decided to switch to PCB design of our system circuitry. And truly speaking

this is the best method in order to realize circuitry. It took less time and effort to build

up. If one undermines the cost of the PCB board design in easy. In the process we used

ARES of Proteus Professional 6 for the design.


71

The previous two methods proved to be cumbersome and can be strictly avoided if one

considers time value of money. Even after PCB design, we had a serious error in

detecting signal because the comparator used to detect the noise always produced logic 1.

From previous work on this project, we found that the problem persisted because of the

transducers. The assumption made was that instead of the ultrasonic sound being

reflected from obstacle surface, the beam of ultrasound is directly received by the

receiver transducer directly. But an intensive, dedicated & long analysis we found the

root cause of the problem. The method initially used was dividing the circuit modules

and conquer. But this proved worthless. The circuit was still buggy and we had no

solutions still. Then after consulting with some senior teachers, we were suggested to use

a resistor across the input of comparator and ground. Testing this on circuit didn't prove

to be fruitful. However the advanced simulation ISIS of Proteus Professional 6 proved to

be a boon.

We carried out the simulations and it yielded the same problem as the hardware circuitry.

Then, we used resistor across input of comparator LM358 and ground, and simulated for

various value of resistors. Finally, we got it through.

The previous work on this project had only concept to measure flow and some ideas on

how to carry the task of finding flow. But we used our own concept of changing the

amplified sine wave from LM833 to square wave to find the frequency of received wave.

The concept was made but it took few days to find appropriate circuitry for the process.

Moreover, sometime use of LCD can be troublesome where LCD might be working but

the contrast may not be set properly. In general, we can ground the Pin 3 of LCD for

optimum contrast.

Problem in Software

The major challenges that we encountered in programming is during the calculation of

flow. In fact, the ultrasound that we used having feature of 40 KHz is responsible for the

following problem.


72

Because 40 KHz of signal has 25 µs of time period and as already mentioned above

during calculation of flow we are supposed to count up the predetermined number of

reflected and received pulses. To count each consecutive pulses only time around 25µs is

available. So the instruction to count the pulses should not have length longer than 25µs

(at most).

In programming to count the burst of pulses we used external hardware interrupt, so it

was always challenge for us to shorten or limit the interrupt service routine of that

interrupt. Moreover, we used the C language instead of Assembly language, which made

our challenge more challenging. Because, unlike in Assembly language, it is always

tough to calculate the machine cycle spent of any instruction in C language.

So, as a solution, we decided not to increase the length of ISR of flow’s external

hardware interrupt. Such that we wrote only one instruction to increase the pulse counter.

And to enable the flow’s external hardware interrupt, we took the help of level’s external

hardware interrupt.

Now, initially we enabled the level’s interrupt and as the reflected wave is received the

level’s interrupt is generated. And in level’s interrupt’s ISR the flow’s interrupt is

enabled. While, at the mean time interestingly, in level’s ISR it disable itself.

Moreover if we were availed with MCU with machine cycle in the range of nanoseconds,

we could have time flexibility in ISR (more instructions could have been written inside

ISR without expending more time) that could enhance the precision, resolution and

ultimately accuracy in flow measurement.

Wireless Ultrasound Flood Monitoring system

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Result and Conclusion

4.1 Results

Due to the limitation of ultrasonic transducers used we could successfully measure the

level of the fluid only up to 2.55 m with resolution of 1 cm (However, it can be increased

up to 0.33 mm). Similarly, in case of measuring flow we could measure the range of flow

rather than accurate flow as set with the resolution of 1.3cm/s.(However, it can be

increased up to 5.44 mm/s). However, we are very hopeful that the circuit would perform

more reliably, if the received wave from the Ultrasound Receiver is filtered and digitized

using ADC.

4.2 Limitation

As far as the limitation of our system is concerned, we could not confirm the accuracy of

value of flow being measured by our system, due to the unavailability of flow measuring

device like flow meter. Moreover, the value of flow wasn’t consistent. Similarly, in case

of level it could detect up to 2.5 meter only. So, it has become the prototype only and to

implement the system in real scenario, we need more sophisticated transducers.

4.3 Conclusion

In our system the flow range detection is good enough to meet our requirement. Precise

level measurement and range flow detection is sufficient to inform and alarm the people

to be aware of flood. Moreover, if we get the consistence value of flow, the system has

the broad application in industries where the information about the flow of any fluid is

vital.

4.4 Future Enhancements

The recommendation for the future enhancements in the project can be:

• To obtain the accuracy in flow such that discharge of the liquid could be measured

• To apply various statistical approaches to accommodate turbulent flow

• Posting the data in the internet such that it could be monitored form any part of the

world


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References

1. Muhammad Ali Mazidi, Janice Gillispie Mazidi , Rolin D. McKinlay, The 8051

Microcontroller and Embedded Systems Using Assembly and C, Second Edition.

2. Kim R. Fowler,Electronic Instrument Design, Architecting for Life cycle.

3. Rajesh Gyawali,Rakshya Shrestha, Rosish Shakya, Shristi Adhikari, “Wireless

Remote Water Level Monitoring System using Ultrasound.”

4. Websites:

http://www.national.com

http://www.alldatasheet.com

http://www.edaboard.com

http://www.8052.com

http://www.en.wikipedia.org

http://hyperphysics.phy-astr.gsu.edu

http://www.interq.or.jp


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APPENDIX A LIQUID CRYSTAL DISPLAY (LCD)

The liquid crystal display (LCD) is passive display equipment. This means it doesn’t emit

light; instead, it uses the ambient light in the environment. By manipulating this light, it

displays required text using very little power. This has made LCDs preferred technology

whenever low power consumption and compact size is critical hence; it is suitable for use

in battery-powered electronic devices. It 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 of an LCD consists of a layer of liquid crystal molecules aligned between two

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

perpendicular to each other. With no liquid crystal between the polarizing filters, light

passing through one filter would be blocked by the other. The surfaces of the electrodes

that are in contact with the liquid crystal material are treated so as to align the liquid

crystal molecules in a particular direction.

Before applying an electric field, the orientation of the liquid crystal molecules is

determined by the alignment at the surfaces. In a twisted nematic device (the most

common liquid crystal device), the surface alignment directions at the two electrodes are

perpendicular, and so the molecules arrange themselves in a helical structure, or twist.

Because the liquid crystal material is birefringent (i.e. light of different polarizations

travels at different speeds through the material), light passing through one polarizing

filter is rotated by the liquid crystal helix as it passes through the liquid crystal layer,

allowing it to pass through the second polarized filter. Half of the light is absorbed by the

first polarizing filter, but otherwise the entire assembly is transparent.

When a voltage is applied across the electrodes, a torque acts to align the liquid crystal

molecules parallel to the electric field, distorting the helical structure. This reduces the

rotation of the polarization of the incident light, and the device appears gray. If the

applied voltage is large enough, the liquid crystal molecules are completely untwisted

and the polarization of the incident light is not rotated at all as it passes through the liquid

crystal layer. This light will then be polarized perpendicular to the second filter, and thus


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be completely blocked and the pixel will appear black. By controlling the voltage applied

across the liquid crystal layer in each pixel, light can be allowed to pass through in

varying amounts, correspondingly illuminating the pixel.

LCD provides a useful interface for the user, debugging an application or just giving it a

"professional" look. The most common type of LCD controller provides a relatively

simple interface between a processor and an LCD. Using this interface is often not

attempted by inexperienced designers and programmers because it is difficult to find

good documentation on the interface, initializing the interface can be a problem and the

displays themselves are expensive.

The 2 lines x 16 character LCD modules are available from a wide range of

manufacturers and should all be compatible with the HD44780. The diagram below

shows the pin numbers for these devices. When viewed from the front, the left pin is pin

14 and the right pin is pin 1.

Figure A.1:- Structure of 2X16 LCD

44780 standards:

The 44780 standard requires 3 control lines as well as either 4 or 8 I/O lines for the data

bus. The user may select whether the LCD will require a total of 11 data lines (3 control

lines plus 8 lines for the data bus). The three control lines are referred to as EN, RS and

RW.


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EN:

The EN line is called “Enable”. This control line is used to tell the LCD that you are

sending it data. To send data to the LCD, your program should make sure this line is low

and then set the other two control lines and/or put data on the data bus. When other lines

are completely ready, set EN high and wait for the minimum amount of time as specified

in the data sheet and end by bringing it back to low again.

RS:

The RS line is the “Register Select” line. When RS is low, the data is to be treated as a

command or special instruction. When RS is high 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:

The RW line is the “Read/Write” control line. When RW is low, the information on the

data bus is being written on the LCD. When RW is high, the program is effectively

querying or reading the LCD. Only one instruction is a read command. All others are

write commands so RW will almost always be low.

D0 – D7:

The 8-bit data pins, D0 – D7, are used to send information to the LCD or read the

contents of the LCD’s internal registers.

To display letters and numbers, we send ASCII codes for the letters A – Z, a – z and

numbers 0 – 9 to these pins while making RS = 1.There are also instruction command

codes that can be sent to the LCD to clear the display or force the cursor to the home

position or blink the cursor. Table A below lists the instruction command codes.

We also use RS = 0 to check the busy flag bit to see if the LCD is ready to receive

information. The busy flag is D7 and can be read when R/W = 1 and RS = 0, as follows:

if R/W = 1, RS = 0. When D7 = 1(busy flag =1), the LCD is busy taking care of internal

operations and will not accept any new information. When D7 = 0, the LCD is ready to

receive new information. It is always recommended to check the busy flag before writing

any data to the LCD.


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Table A.1 : LCD Command Codes

Code (Hex) Command to LCD Instruction

Register

1 Clear display screen

2 Return Home

4 Decrement Cursor(shift cursor to left)

6 Increment Cursor(shift cursor to right)

5 Shift Display right

7 Shift Display left

8 Display off, cursor off

A Display off, cursor on

C Display on, cursor off

E Display on, cursor blinking

F Display on, cursor blinking

10 Shift cursor position to left

14 Shift cursor position to right

18 Shift the entire display to the left

1C Shift the entire display to the right

80 Force cursor to beginning of first line

C0 Force cursor to beginning of second line

38 2 lines and 5 X 7 matrix


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APPENDIX B KEYPAD INTERFACING WITH MCU

This section describes the basic circuit of 4 X 4 matrix keypad using push to on switches

and the basic algorithm to interface the keypad with MCU. The circuit of figure C.1

shows the 4x4 matrix keypad connected to a single port. The rows are connected to an

output port (upper nibble of the port) and the columns are connected to input port (lower

nibble of the port). If no key has been pressed, reading the input port will yield 1s for all

columns since they are all connected to high (Vcc). If all the rows are grounded and a key

is pressed, one of the columns will have 0 since the key pressed provides the path to

ground. It is the function of the MCU to scan the keypad continuously to detect and

identify the key pressed. The process described as below:

The process is proceeding with grounding rows and reading the columns. To detect a

pressed key, the MCU grounds all rows by providing 0 to the output latch, that it reads

the columns. If the data read from the columns is D3 – D0 = 1111, no key has been

pressed and the process continues until a key press is detected. However, if one of the

column bits has a zero, this means that a key press has occurred. For example, if D3 – D0

= 1101, this means that a key in the D1 column has been pressed. After a key press is

detected, the MCU will go through the process of identifying the key. Starting with the

top row, the MCU grounds it by providing a low to row D0 only: then it reads the

columns. If the data read is all 1s, no key in that row is activated and the process is

moved to the next row. It grounds the next row, read the columns, and checks for any

zero. This process continues until the row is identified. After identification of the row in

which the key has been pressed, the next task is to find out which column the pressed key

belongs to. This should be easy since the MCU knows at any time which row and column

are being accessed.

The entire process has also been described in flowchart figure C.2


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Figure C.1: Circuit diagram of Keypad

The figure C.1 shows the circuit diagram of keypad of 4X4 array with 16 push to on

switches. Both ends of the switches are connected to the pin of a single port with resistors

connected to the Vcc. The value of the resistor we used is of 4.7 KΩ


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Figure C.2 : Flowchart for keypad programming


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APPENDIX C

COST ANALYSIS

List Of Components Quantity Cost/piece Total Cost in Rupees

LM833N 1 120 120

LM358 1 80 80

AT89C51 1 150 150

CD4011 1 60 60

CD4069 1 60 60

L7809 1 20 20

L7805 1 15 15

74HC04 1 40 40

555 Timer 1 20 20

MAX232 1 80 80

Resistors/Diodes - 70 70

Capacitors - 100 100

Crystal Oscillator 1 35 35

Ultrasonic Transducers 2 850 1700

Transistors 2 20 40

Connecting Wires - 100 100

RF modules 4 1650 6600

LCD 1 640 640

Total Cost 9930


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3.3.5 Circuit Diagram

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