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CHAPTER 1: INTRODUCTION TO PROJECTMeasuring the distance is a need of human being always because of many
reasons. Knowing distance of any object is so important in lots of categories. In
nowadays world, cars, planes, robots, rockets… etc. are need to measure or sense the
distance of the objects that are near to them. In addition that, in astronomy, army, security
works, research works as water, petrol or mine; distance measuring is very important
subject for efficient working, and success.
Distance measuring is done with many ways. For example with sound, light, laser,
infra‐red, radio navigation, etc. In nowadays world, with the help of developing
technology, measuring distance is getting so easy with the sensors.
Most of the distance measuring systems have become so common and so easy to use
in the daily life of humans. For example, to park a car, to search anything under the land,
to have a safe travelling for airplanes, ...etc. and lots of using areas are so common.
In the project that is explained in this report is about measuring distance and its
called “Ultrasonic Range Finder” because of using the ultrasonic sensors in our project
for this purpose.
Ultrasonic principle is based on high frequency sound waves that human ear can not
hear. The reasons of using this high frequency waves are can be said as below:‐These waves radiate extremely smooth and linear‐Energy of these waves are in high level‐These waves can be easily reflected from hard planes
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The measure of the distance is done simply by following below steps-
Fig1- Block diagram of Ultrasonic Range finder
Firstly ultrasonic waves are sent and then wait until reflected signal has come. After
that, the time is calculated between sent and received signal. Finally, time and the
velocityof the sound multiplied each other, so the half of the result shows the distance of
the object.
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CHAPTER-2: INTRODUCTION TO 8051 MICROCONTROLLER
The heart of the project is the 8051 microcontroller which is controlling all the
project.
2.1: FEATURES
The 8051 is an 8-bit processor
The 8051 has 128 bytes of RAM
4K bytes of on-chip ROM
Two 16 bit timers
One serial port
Four I/O ports, each 8 bits wide
6 interrupt sources
Separate 64k programme and 64k data memory
The CPU can work on only 8 bits of data at a time
2.2: PIN DIAGRAM
Fig2- Pin diagram of 8051
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2.3: PORTS
The 8051 has four I/O ports
Port 0 (pins 32-39)
Port 1(pins 1-8)
Port 2(pins 21-28)
Port 3(pins 10-17)
Each port has 8 pins
• Named P0.X (X=0,1,...,7), P1.X, P2.X, P3.X
• P0.0 is the bit 0(LSB)of P0
• P0.7 is the bit 7(MSB)of P0.
2.4: CLOCK GENERATION
Fig3- clock generation
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8051 has 2 oscillator pins called XTAL1 and XTAL2. A resonance circuit is connected to
these 2 input pins to create a supply for the oscillators that inside of the IC. Generally a
crystal and 2 capacitors is enough for that circuit. A connected resonance circuit that is
also used in our design is seen in the figure below. Here, no matter the value of the
capacitors. They can be chosen between 27 – 47 pF.
2.5: RESET CIRCUIT
The RST input on pin 9 is the master reset for the 8051. When this signal is brought high,
for at least two machine cycles the 8051 internal registers are loaded with appropriate
values for an orderlysystem start-up.
Fig4-Reset circuit
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2.6: CONSTITUTION OF PORT3
The port 3 of 8051 provides alternative functions as shown in following table
Table1- Alternative functions of port3
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3: INTRODUCTION TO ULTRASONIC SENSORS
400SR100 type ultrasonic sensor is has two parts as transmitter and receiver parts.
Transmitter part transmits the high frequency signal to object and receiver part gets the
reflected signal from any object. These ultrasonic sensors work with high frequency that
more than a human ear can hear.
Fig5- Ultrasonic sensors
Ultrasonic sensor couples are connected themselves with respect to the diagram of
the circuit diagram . The first sensor is transmitting sensor and it has an input pin to get
the PWM.
This input is used for giving high frequency signal. The second one is receiver sensor and
it has an output pin that would be connected to 8051. That output from receiver is
connected to the microcontroller to make it work when received signal is taken from any
object.
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3.1: TIMING DIAGRAM
Fig6-Timing diagram of sensor
The ultrasonic transmitter unit with a 40 kHz pulse burst and expect an echo from the
object whose distance you want to measure. Fig. 7 shows the transmitted burst, which
lasts for a period of approximately 0.5 ms. It travels to the object in the air and the echo
signal is picked up by another ultrasonic transducer unit (receiver), also a 40 kHz pre-
tuned unit.
The received signal, which is very weak, is amplified several times in the receiver circuit
and appears somewhat as shown above.
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3.2BEAM PATTERN
Fig7-Beam pattern of ultrasonic transmitter
The signal at the main lobe is having maximum power whereas at the side lobes it
is having less power.
3.3 SPECIFICATIONS OF 400SR100:
Driving voltage – 10 to 20 v
Driving current- 20mA
Frequency - 40kHz
Maximum range- 3 meters
Minimum range- 3 centimeters
Beam angle -72º
Operating Temperature- -30º to 80ºC
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3.4 DISTANCE MEASURMENT
The distance is measured by using the relation of distance and velocity of sound
DISTANCE= (TIME X VELOCITY OF SOUND IN A MEDIUM.)/2
The velocity of sound is approximately 330m/s in air.
This value is divided by two because the ultrasonic wave will take time to reach at the
object as well as to return as an echo.
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4: CIRCUIT DESCRIPTION OF ULTRASONIC RANGE FINDER
4.1: CIRCUIT DIAGRAM AND WORKING
Fig. 9 shows the circuit of the microcontroller-based distance meter. The 40kHz
pulse bursts from the microcontroller are amplified by transistor. Inverting buffer 4049
drives the ultrasonic sensor used as the transmitter. Three inverters (N1, N2and N3) are
connected in parallel to increase the transmitted power.
This inverted output is fed to another set of three inverters (N4, N5and N6).
Outputs of both sets of parallel inverters are applied as a push pull drive to the ultrasonic
transmitter. The positive going pulse is applied to one of the terminals of the ultrasonic
sensor and the same pulse after 180-degreephase shift is applied to another terminal. Thus
the transmitter power is increased for increasing the range.
The echo signal received by the receiver sensor after reflection is very weak. It is
amplified by quad operational amplifier LM324.
The first stage is a buffer with unity gain. The received signal is directly fed to the
non-inverting input (pin 3) of A1 and coupled to the second stage by a 3.3nf(small-value)
capacitor.
The second stage of theinverting amplifier uses a 2-mega-ohm
resistor for feedback. The third stage is a precision rectifier amplifier with a
gain of 10.
The rectifier functions, unlike a simple diode, even for signal voltageof less than
0.6V. The output is filtered to accept 40kHz frequencies and fed to pin 12 of LM324
which is non inverting input of the fourth comparator. Pin13 is the inverting pin of the
comparator used for level adjustment using trimmer which is set to Vref=0.17v.
The output of this comparator which will be amplified echo pulse given to the pin
P3.2 of microcontroller for counting of time. When port-3 pin P3.2 goes high, we know
that the echo signal has arrived; the timer is read and the 16-bit number is divided by
twice the velocity of sound and then converted into decimal format as a 4-digit number.
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4.2: SOFTWARE
PROGRAM:
#include<reg51.h>
sfrldata=0xA0; // assign port2 to for lcd data
sbitrs=P1^2; // assign lcd rs, rw, enable pins
sbitrw=P1^1;
sbit en=P1^0;
sbit echo=P3^2; // assign echo pin
sbit trig=P1^4; // assign pin for 40kHz pulse
int a,p,count=0, d=0,e,e1,f,f1,g,g1,h,h1,t,t1;
unsigned char r[]=" ULTRASONIC";
unsigned char s[]="RANGE FINDER";
unsigned char j[]="DISTANCE=";
void msdelay(unsigned int k) //delay subroutine
{
Unsigned int i, j;
for(i=0;i<=k;i++)
{
for(j=0;j<=1275;j++);
}
}
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Void lcdmsg(unsigned int value) //lcd data subroutine
{
ldata=value;
rs=1;
rw=0;
en=1;
msdelay(10);
en=0;
}
Void lcdcmd(unsigned int value) //lcd command subroutine
{
ldata=value;
rs=0;
rw=0;
en=1;
msdelay(10);
en=0;
}
void main()
{
P3=0XFF; // port 3 as input port
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P1=0xF8; // pins P1.0, P1.1, P1.2 as output
P2=0x00; // port 2 as output port
trig=0;
echo=0;
TMOD=0X22; // timer0, timer1, both in mode2 i.e. auto reload
TH0=0xF5; // count in timer 0 for 40kHz pulse
TH1=0xCB; // count in timer1 for pulse width(14.5mS)
lcdcmd(0x38); // lnitialise lcd as 2 lines and 5x7 matrix
lcdcmd(0x0E); //lcd on
for(a=0;a<11;a++)
{
lcdmsg(r[a]);
}
lcdcmd(0xc0);
for(a=0;a<12;a++)
{
lcdmsg(s[a]);
}
while(1)
{
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count=0;
{
for(p=0;p<26;p++) // send 25 40kHz pulses to Tx
{
TF0=0;
TH0=0XF5;
trig=0;
TR0=1;
while(TF0==0){}
trig=1;
TF0=0;
while(TF0==0){}
}
}
if(echo==1) // check whether echo is available
{
while (echo==1)
{
TR1=1; // if yes, start timer1
lcdcmd(0x01);
for(a=0;a<9;a++)
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{
lcdmsg(j[a]);
}
while(TF1==0)
{}
count++;
TF1=0;
}
TR1=0; // stop timer
d=(count*0.0145*330)/2; // count distance
e=d/1000;
t=d%1000;
f=t/100;
t1=t%100;
g=t1/10;
h=t1%10;
e1=0x30|e;
f1=0x30|f;
g1=0x30|g;
h1=0x30|h;
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lcdcmd(0x89); // display distance on lcd
lcdmsg(e1);
lcdcmd(0x8A);
lcdmsg(f1);
lcdcmd(0x8B);
lcdmsg(g1);
lcdcmd(0x8C);
lcdmsg(h1);
lcdmsg('c');
lcdmsg('m');
}
}
}
PROGRAM DESCRIPTION
The program is written in embedded C language.
The pin P1.4 is used for giving the 40 kHz pulse which is done with the help of
timer0. Port 2 is assigned for data sending to lcd. RS, RW ,E pins ofl lcd are connected
to P1.2, P1.1,P1.0 respectively.
The echo pulse from the comparator output is given to P3.2. By using timer1 the
high level width of the pulse which is proportional to the distance between object is
calculated. ( distance= time x velocity of sound/2).
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4.3: APPLICATIONS
Automatic parking system.
Obstacle warning system
Terrain monitoring robots
Industrial distance measurement
Burglar alarm unit for office or home
Airplane landing
4.4: ADVANTAGES OF ULTRASONIC DISTANCE MEASUREMENT
It can give very accurate measurement which is highly important in military
applications, airplane landing, etc.
We can also measure distance of an object through water.
By making few modifications we can also detect a moving objects and find their
range and speed.
4.5: DISADVANTAGES OF ULTRASONIC DISTANCE MEASUREMENT
It requires very precise frequency, a slight change in frequency of pulse may
affect the accuracy.
The characteristics of ultrasonic sensor change with change in temperature, so
special attention is required to be given for applications where high accuracy is
required.
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CONCLUSION
Ultrasonic distance meter project was very useful application for us because of using
several elements, hardware design, connecting them, and programming microcontroller
as software. This project has taught us how a real project can be realized, to develop our
programing ability, and hardware design.
By the help of this project work, our ability of setting up circuit, connecting elements,
soldering, and hand practice are developed and so that we got a good trust of ourselves to
success something in real.
In addition to that, this project‐work is as a start of an experiment for our job that we
will do in future. With the help of that, we learnt how to see the difficulties and problems,
how to overcome all of them and solve all problems so that to reach the success.
Beside all them, we have found the possibility to realize a real thing. It’s not as the
same to do it by simulations on PC. Seeing a real thing and its running make us feel more
positive.
We believe that with the continuing of similar applications project, our ability in most
of subject will be raised day by day.
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REFERENCES-
E-Book
The 8051 microcontroller by Md. Ali Mazidi
Websites
www.8051project.com
www.alldatasheets.com
www.datasheetarchieves.com
www.efymag.com
www.midascomponents.uk
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