VEHICLE SPEED MEASUREMENT
SYSTEM
TABLE OF CONTENTSTopic Page No.
CERTIFICATE ....................................................................................................... 2
DECLARATION ..................................................................................................... 3
ACKNOWLEDGEMENT… .................................................................................... 4
ABSTRACT.............................................................................................................. 5
CHAPTER 1.INTRODUCTION.............................................................. ................ 6
1.1. The Basic Concept ....................................................................................... 7
1.2. Circuit Description...................................................................................... 8
1.3. Components List.......................................................................................... 10
CHAPTER 2.CONSTRUCTION AND WORKING
2.1. Construction………………………………………………………………... 12
2.2. PCB layout…………………………………………………………………. 13
2.3. PCB designing ………….…………………………………………………. 14
2.4. Coding………………………………………………………………………. 19
CHAPTER 3.Component Description
3.1. Resistance…………………………………………………………….....32
3.2.
Capacitor………………………………………………………………...33
3.3. Semiconductor Diode ………………………………………………….. 34
3.4. LED……………………………………………………………………. 35
3.5. Laser……………………………………………………………………..37
3.6 LDR ……………………………………………………………………...42
3.7 PIC16F877 Microcontroller…………………………………………….. 44
3.8.Voltage regulator IC 7805 ……………………………………………… 55
3.9 Transformer……………………………………………………………... 57
CHAPTER 4.CONCLUSION ……………………………….………………… 59
BIBLIOGRAPHY…………………………………………………………… ... 60
ABSTRACT
With the advent of modern era an exponential increase in the number of vehicle the
number of accident has risen alarmingly. One of the main reasons for such a rise is the
negligence of drivers especially on highway, where less traffic seemingly allow him to
take a negligent approach toward safety rules. Often high speeding vehicles pose a
danger to fellow commuter .This project aspire to solve such problem by measuring the
vehicle speed and then giving alarm in case of overspeed.
CHAPTER 1
INTRODUCTION
The system “Vehicle Speed Measurement System” has come into existence, to prevent
accidents that keep occurring due to speed violation, since the drivers tend to ignore their
speedometers. Speed measurement using a light barrier is achieved by using transmitter
and receiver. They are basically implemented on highways.
This speed checker will come handy for the highway traffic police as it will not only
provide a 16X2 LCD Module Display in accordance with a vehicle‘s speed but also
sounds an alarm if the vehicle exceeds the permissible speed for the highway.
The system basically comprises of two laser transmitter- Ultrasonic sensor pairs, which
are installed on the Highway 100m apart, with the transmitter and the sensor of each pair
on the opposite sides of the road.
1.1 BASIC CONCEPT
The system displays the time taken by the vehicle in crossing this 100m distance from
one pair to the other with a resolution of 0.01second, from which the speed of the vehicle
can be calculated as follows:
Speed (kmph) = Distance/Time
= 0.1km/{(Readingx0.01)/3600}
Or,
Reading = 3600/Speed (On display)
As per the above equation, for a speed of 40kmph the display will read 900(or 9seconds),
and for a speed of 60kmph the display will read 600 (or 6 seconds). Note that the LSB
of the display equals 0.01second and each succeeding digit is 10 times the preceding
digit. Then if the speed cross a prescribed limit through alarm we may know it.
.
.1.2 CIRCUIT DESCRIPTION
The circuit consists of major parts:
1) The power supply
2) The transmitter section :- ultrasonic sensor
3) The micro controller section
The power supply is used to convert to ac to dc via transformer, then with the help of
voltage regulator IC 7805 a 5 Volt dc supply and through IC 7806 a 6 volt dc supply is
obtain .The need of these supply arises due to the fact that every electronic component
either works on a 5 v and 6 v dc supply
The transmitter section consists of a two laser transmitters.
The receiver section consists of two ultrasonic detectors; these two detectors catch the
rays coming from the transmitter. When a object pass through the first pass it blocked
the light coming from the first transmitter which is noted by the first detector and when
the object passes through the second transmitter then the absence of light is obtained by
the second detector .Then the distance is calculated by the microcontroller .
The microcontroller is the main controlling section of the project. It performs a number
of functions. It is attached through the two photo detector through two forward bias
transistor which serves as amplifiers to amplify the current received.
The second function of microprocessor is to calculate speed of travelling vehicle with
help of elapse time measurement method.
This microcontroller is then attached to a buzzer which produces an alarm if the speed of
vehicle exceed a specified speed limit .Microcontroller is also interfaced with a 16X2
LCD Module display which shows the vehicle speed.
1.3 COMPONENT LIST:
1. Resistors (all ½ watt, ± 5% carbon)
Quantity Value
7 10K
6 1K
1 20K
2.Capacitors
Quantity Value
2 470uF,25V electrolytic
2 22 pF, 25V electrolytic
1 1000uF, 35V electrolytic
3. Integrated Circuits
Quantity Value
1 16X2 LCD Module display
1 PIC16f8777A
1 7805 , 5V regulator
4. Diodes
Quantity Value
2 IN4007, rectifier diode
3 Light Emitting Diode
2 Laser Diodes
5. Miscellaneous
Quantity Value
1 230V AC primary to 12-0-12V, 500mA
secondary transformer
1 4 MHz, Crystal Oscillator
2 Push-to-on switch
1 On/Off switch
2 Transistors
Ultrasonic Range Meter
The Ultrasonic Range Meter is an efficient way to measure the distance of unreachable
obstacles. It is based on sending sound waves through a specific medium and observing the
returning echoes to measure the distance from the device to the obstacle.
The device is divided into three parts, transmitter, receiver and the microcontroller. The
transmitter consists of an electronics circuitry which generates electrical signal .In addition, an
electromechanical transducer to convert electrical signal to physical form to drive through the
medium, which is air. The receiver also consists of an electronics circuitry which detects the
echoes bounced back from the obstacles. The microcontroller is programmed for selectivity
sequence and to calculate the time of flight of the signal to find the distance and display it.
The system architecture of the Ultrasonic Range Meter was built to be cheaper, requires less
power and delivers better performance. It can be reconfigured to adapt to a variety of pulsed
Ultrasonic systems.
Introduction
The main purpose of this project is to measure the distance to unreachable objects, obstacles or
places using a portable device.
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Figure 2.1: The hand-held ultrasonic range meter device.
2.2 Motivation
The motivation of using this device is when construction engineers at any sites need to measure
distances to unreachable places in a quick and easy way using this device with high efficiency
and accuracy.
2.3 Characteristics
This device detects the distance to an object and shows the result in centimeters. This device is
activated by a trigger mechanism, pressing the trigger for one time will give us the distance to
an object if there was no error like poor aiming. The distance to an object is displayed using a
digital display with a high intensity in order to be seen in any lighting conditions.
It is a simple and portable device similar to a gun as shown in Figure 2.2 that uses a laser pointer
to aim at a specific area to get the reflection at the receiver side.
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Figure 2.2: Description of each part of the device.
2.4 Conclusion
In order to design and build a portable device, the weight of the device is a primary problem.
The technology of using ultrasonic to measure distances is in continuous progress, features have
been added to this technology to make it easy to use and more accurate by assigning more
challenging constraints. The constraints of our device are discussed in the next chapter.
3.1 Introduction
Defining the constraints of our device will help to design and then build the hand-held ultrasonic
range meter device. By defining these constraints, the problems will be clearer, the suitable
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solutions will become easier to find and those constraints will help to get the design needed
from the engineer.
3.2 Minimum target size and ultrasonic medium
The minimum target size is 40cm*40cm in order to get detection at the receiver side.
The ultrasonic medium is air.
3.3 Target range
The target range is the distance range between the person who is using the hand-held ultrasonic
range meter device and the targeted object. The target range consists of two boundaries, one is
the minimum distance limit and the other is the maximum distance limit. If the operator of the
hand-held ultrasonic range meter device exceeds these two boundaries, the hand-held
ultrasonic range meter device may not detect the distance or may display a false detection.
The target range is between 10 centimeters and 300 centimeters.
3.4 Range measurement accuracy
Each specific distance has an error percentage; the more samples sent the less the error is.
The range measurement accuracy is the accuracy of the distances measured between the
operator of the hand-held ultrasonic range meter device and the targeted object; it allows
knowing how much each distance is close to the real value of the distance. The range
measurement accuracy is +/- 3 cm. The less this value is, the more accurate distances would be
calculated by the hand-held ultrasonic range meter device.
3.5 The battery
A 9 V battery could be used to activate this device.
3.6 Weight and size
Our device would not exceed the weight 0.5 kilogram. This weight is acceptable for the operator
to carry the hand-held ultrasonic range meter device and to fix his arm while aiming at the
targeted object.
The area of the cover is 15cm x 7 cm, and the height is 8 cm.
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3.7 Budget
This hand-held ultrasonic range meter device is between 50 U.S dollars and 75 U.S dollars.
3.8 Time
The time estimated to accomplish the hand-held ultrasonic range meter device is one month
due to the changes in the constraints.
3.9 Number of engineers
The number of engineers working on the hand-held ultrasonic range meter device is three
engineers.
3.10 Conclusion
After discussing and choosing the constraints, the solutions for these sets of challenging
problems are to be discussed and solved physically and mathematically in the next chapter.
4.1 Introduction
To solve the problem of detecting the distance to an object, many solutions are presented. In this
chapter the solutions are discussed, all the advantages and disadvantages are shown. The
comparison between these solutions will help to determine which solution has more advantages
and satisfies the constraints at the same time.
4.2 Hand-held laser range meter device
4.2.1 Description
This device is characterized by its accuracy and portability; it uses a laser beam. The two
techniques might be used to measure the distance. There are two techniques that have been
used in order to measure distances, the time of flight technique and the triangulation technique.
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4.2.1.1 Time of flight measurement
Even the fastest photon requires a certain period of time to cover the distance from the sensor
to the target and back. This time is directly proportional to the distance traveled, taking into
account the velocity of light in the medium involved, which may be easily derived from the
velocity of light in a vacuum. The cost and complexity of this method depends upon the
precision and resolution required.
Data acquisition and analysis electronics must cope with ns and sub-ns time scales: decimeter
ranges may be easily resolved by nanosecond pulses but precision in the millimeter and sub-
millimeter range requires pulse lengths of a few tens of picoseconds and the associated
electronics. Clearly, a poorly resolved pulse will lead to uncertainty in the accuracy of the
measurement; the standard deviation in measured distance is proportional to the optical pulse
rise time and is inversely proportional to the signal-to-noise ratio. At ranges of a few kilometers
and above, a different problem arises; at such distances the amount of reflected photons which
reach the detector is very small. Signal intensity can be improved by optimum beam focusing at
the source, or by the use of a retro reflector mounted in the target.
4.2.1.2 Triangulation
Triangulation is the most commonly used method for distances of 10 meters or less. A laser or
LED is used to produce a collimated beam which then impinges on the surface of the target. The
target reflects light in many directions, some of the reflected light reaching the detector. The
position of the reflected light focused onto the detector depends on the distance between the
sensor and target. Detectors such as position sensitive detectors (PSD), diode arrays or CCD
arrays enable the reflected light to be detected with high spatial resolution and at high sampling
frequencies. The sensor-object distance is calculated trigonometrically and accuracies of better
than 0.5% are the norm.
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Measurement times of less than 10 ms are common, allowing real-time study of moving or
vibrating objects. The light source should be compact and should produce an intense, small spot
of light with minimal divergence. Amplitude modulation is used in order to eliminate the effects
of stray (background) light.
Figure 4.1: Hand-held laser range meter device.
4.2.2 The advantages
As shown in Figure 4.1, the hand-held laser range meter device is a portable device.
It is characterized with its high accuracy and high precision. The laser beam consists of a small
beam width which reaches a long target range.
4.2.3 The disadvantages
The poor aiming on the targeted object causes a bad reflection of the laser and that would
display a false detection of the object’s distance that has been targeted.
The atmospheric conditions may affect the ranging capabilities of the hand-held laser range
meter device. The rain and snow reflect the laser beam and that may display a false detection of
the object’s distance.
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4.3 Hand-held ultrasonic range meter device
4.3.1 Description:
This device works on the same concept of the laser gun device but the difference is that it uses a
large beam width of ultrasonic waves as shown in Figure 4.2. The time of flight and triangulation
techniques might be used to measure the distance using ultrasonic waves.
Figure 4.2: Hand-held ultrasonic range meter device.
4.3.2 The advantages
The hand-held ultrasonic range meter device is a portable device as shown in Figure 4.2. The
hand-held ultrasonic range meter device is characterized with its precision and high accuracy.
Atmospheric conditions will not affect the capabilities of the device.
4.3.3 The disadvantages
The beam of the hand-held ultrasonic range meter device consists of a large beam width as
shown in Figure 4.2 and that may cause a false detection of the object’s distance at the receiver
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side because the beam may hit a group of objects placed near each others and the reflection of
the ultrasonic wave is caused by several objects. The object must be flat and not an absorber
and it should be normal to the direction of the ultrasonic wave. This device could be jammed
and is affected by interference.
4.4 Comparison
After looking at the advantages and the disadvantages, the best solution is to use the gun device
using laser beams. The beam width of the hand-held laser range meter device is smaller than
the beam width of the hand-held ultrasonic range meter device as shown in Figure 4.5; this
enables the operator of the hand-held laser range meter device to hit a specific object and get
less reading errors unlike other devices.
The comparison has shown that the hand-held ultrasonic range meter devices could be better in
some cases because it will not be affected by the atmospheric conditions. As shown in Table 4.1,
using a descending order from the best accuracy and precision of the devices to the worst, the
most accurate and precise is the hand-held laser range meter device. The second is the hand-
held ultrasonic range meter device. Depending on our constraints, our choice was to design an
ultrasonic range meter because of the budget and availability of the components.
Table 4.1: Solutions comparison with respect to its accuracy and precision.
Devices Hand-held laser
range meter
Hand-held ultrasonic
range meter
Accuracy High accuracy High accuracy
Precision High precision Precise
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Figure 4.3: Beam width comparison of ultrasonic waves and laser beams.
4.5 Conclusion
Each solution has its advantages and disadvantages depending on the situation where the
device is used; the hand-held laser range meter device is a fast growing technology because of
its efficiency and its accuracy as well as the hand-held ultrasonic range meter device as shown in
Table 4.1. In the next chapter the design of the hand-held ultrasonic range meter device will be
implemented.
CHAPTER 5
All designs are based on specific constraints. The design of the hand-held ultrasonic range meter
device is based on measuring the distance using the time of flight technique. The process of this
design is more explained in details in the next section.
5.2 The overall system
The calculations are done by the following way. First of all, the device calculates the time that
the ultrasonic wave took to reach the targeted object and come back to the receiver. Thus, if we
need to calculate the time needed for the ultrasonic wave to reach the object from the device,
we divide the previous time we had by two. Second, the device multiplies the time by the speed
of sound (340 m/s) to get the distance between the device and the object. The time from
transmission of the pulse to reception of the echo is the time taken for the sound energy to
travel through the air to the object and back again. Since the speed of sound is constant through
air, measuring the echo reflection time lets you calculate the distance to the object using this
equation:
Distance = (s * t)/2 (in meters) (5.1)
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Where: s [m/s] is the speed of sound in air and t [s] is the round trip echo time.
Table 5.1: The delay times of boundary range
Round trip echo
time
Distance
t = 588 us10 cm
t = 17.6 ms3 m
.
Figure 5.1: General block diagram.
5.2.1 Calculation of the distance to an object
The hand-held Ultrasonic Range meter device offers precise ranging information from roughly
10cm to 3 meters. The ranger works by transmitting a pulse of sound outside the range of
human hearing. This pulse travels at the speed of sound away from the ranger in a cone shape
and the sound reflects back to the ranger from any object/target in the path of this sonic wave.
The ranger pauses for a brief interval after the sound is transmitted and then awaits the
reflected sound in the form of an echo. The controller driving the ranger then requests a ping;
the ranger creates the sound pulse, and waits for the return echo. If received, the ranger reports
this echo to the controller and the controller can then compute the distance to the object based
on the elapsed time.
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The Pulse Trigger Input line should be held low and then brought high for a minimum of 100μsec
to initiate the sonic pulse. The pulse is generated on the falling edge of this input trigger. The
ranger’s receiver circuitry is held in a short blanking interval of 600 μsec to avoid noise from the
initial ping and then it is enabled to listen for the echo. The echo line is low until the receive
circuitry is enabled. Once the receive circuitry is enabled, the falling edge of the echo line signals
an echo detection or nothing if there is no reflection.
The long-range measurement is difficult a little. To measure the correct distance, the following
conditions are necessary.
The object must be perpendicular to the range meter.
The surface of the object must be flat.
There is not object which reflects the ultrasonic around.
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Figure 5.2: Theoretical graph of the pulses and its echo-reflection pulse.
5.3 Ultrasonic system
It consists of a transmitter and receiver pair on the device and a microcontroller with a digital
display. There are two different transducers for transmitter and receiver. The transmitter
transmits and the receiver waits for the reflected signals. The Figure 5.3 illustrates this system.
Figure 5.3: The overall design of the ultrasonic system.
5.3.1 Ultrasonic Transmitter
The transmitter consists of an electronics circuitry and an electromechanical transducer.
The electronic circuitry generates the required frequency electrical signal and the
electromechanical transducer converts that electrical signal into the physical form and activates
the open medium surface. This oscillating physical surface creates the ultrasonic Waves. The
oscillating surface creates a pressure variation and ultimately a pressure wave with a frequency
equal to that of the surface oscillation. The Figure 5.4 shows the generation of ultrasonic waves.
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Figure 5.4: The transmitter circuit design.
The transmitter was designed to oscillate at a resonant frequency of about 40 KHz. The 555
timer generates a 40 KHz sinusoidal ultrasonic wave. The frequency is calculated by using the
following formula:
F = 1.44 / 2 * R1 * C = 1.44 / 2 * 15.6 KΩ * 1nF = 46 kHz. (5.1)
This design of the transmitter was done in way to get the closest value to 40 KHz by adjusting
the resistor and the capacitor to the values shown in the Figure 5.4.
5.3.1.1 The 555 timer datasheet
The 555 monolithic timing circuits is highly stable controller capable of producing accurate time
delays, or oscillation .In the delay time of operation, the time is precisely controlled by one
external resistor and capacitor .For a stable operation as an oscillator, the free running
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frequency and the duty cycle are both accurately controlled with two external resistors and one
capacitor. As shown in Figure 5.5:
Figure 5.5: The 555 block diagram.
The Table 5.2 shows the datasheet of the 555 timer, the parameter rating and the units
characterized by each component.
Table 5.2: The datasheet of the 555 timer
Symbol Parameter Rating Unit
VCC Supply Voltage +16 V
Pd Maximum allowable power
dissipation 600 mW
TAOperating ambient
temperature range0 to 70 ºC
VTH (Vcc = 5v) Threshold voltage 3.33 V
VTRIG(Vcc = 5v) Trigger Voltage 1.67 V
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VRESET Reset Voltage 0.3 to 1.0 V
.5.3.2 Ultrasonic Receiver
The receiver also has the same configuration except that it has a receiver electronic circuitry and
a transducer, which converts the ultrasonic sound waves into an electrical signal. The sound
waves travel into the medium and are reflected by an object in the path of the waves. This
reflected wave is then sensed by the receiver, which actually calculates the time of flight of the
signal to find the distance. The Figure 5.6 illustrates the receiver circuit.
Figure 5.6: The receiver circuit design.
5.3.2.1 Basis of the operational amplifier
The operational amplifier is the amplifier with the very big voltage gain.
In case of TL082 to be using this time, at the specification, the voltage gain becomes 150V/mV. It
is the 15 V output in 0.1 mV of the input. To say becomes 150,000 times of gain. In case of the
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operational amplifier, the value of the voltage gain doesn't have the relation too much. Anyway,
the fact that the voltage gain is big is important.
5.3.2.2 The Difference Gain amplification
There are positive input and negative input in the operational amplifier.
The voltage gain can be calculated by the following formula.
G = Vo/Vi = -(Rf/Ri) (5.2)
Figure 5.7: The difference gain amplification.
Using the voltage divider formula:
Vb = V1 * R2/(R1 + R2) (5.3)
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The current passing through Ri is the same current passing through Rf because the current
entering the negative input is negligible in μA (in the ideal operational amplifier, it is considered
zero) and this gives the following equation:
(Vi – Va) / Ri = (Va – Vo) / Rf (5.4)
Vo = (V1 * R2 * (Rf + Ri) / (R1 + R2) * Ri)– Vi * Rf / Ri (5.5)
5.3.2.3 Signal amplification circuit
The signal amplification circuit is illustrated below in the Figure 5.8.
Figure 5.8: The circuit of the signal amplification.
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The ultrasonic signal which was received with the reception sensor is amplified by 2500 times
(68dB) of voltage with the operational amplifier with two stages.
The voltage gain G is 100 times at the first stage (40dB) and 25 times (28dB) at the next stage.
Generally, the positive and the negative power supply are used for the operational amplifier.
The circuit this time works with the single power supply of +5 V. Therefore, for the positive input
of the operational amplifiers, the half of the power supply voltage is applied as the bias voltage
and it is made 2.5 V in the central voltage of the amplified alternating current signal.
When using the operational amplifier with the negative feedback, the voltage of the positive
input terminal and the voltage of the negative input terminal become equal approximately. So,
by this bias voltage, the side of the positive and the side of the negative of the alternating
current signal can be equally amplified. When not using this bias voltage, the distortion causes
the alternating current signal. When the alternating current signal is amplified, this way is used
when working the operational amplifier for the two power supply with the single power supply.
Using the formula in 5.1:
Vi is the input voltage at the ultrasonic transducer.
Vo1 is the output voltage of the first amplification stage.
Vo2 is the output voltage of the second amplification stage.
At minimum distance, d = 10 cm,
Vi max = 2.50004 V.
Vo1 = (5 * 47K * (100k + 1k) / (47k + 47k) * 1K) - 2.50004 * 100k / 1k = 2.496 V.
Vo2 = (5 * 47K * (100k + 3.9k) / (47k + 47k) * 3.9K) - 2.496 * 100k / 3.9k = 2.6 V.
At maximum distance, d = 3 m,
Vi max = 2.4999 V.
Vo1 = (5 * 47K * (100k + 1k) / (47k + 47k) * 1K) - 2.4999 * 100k / 1k = 2.46 V.
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Vo2 = (5 * 47K * (100k + 3.9k) / (47k + 47k) * 3.9K) - 2.46 * 100k / 3.9k = 2.50156 V.
ΔVi = 2.50004 – 2.4999 = 0.04 mV.
A slight change in Vi formed a bigger change in Vo2.
Δ Vo2 = ΔVi * Gain = 0.04 * 2500 = 100 mV.
5.3.2.4 Data of the TL082 operational amplifier
As for TL082, the two operational amplifiers are enclosed with the one package.
Figure 5.9: Pin connections top view.
Table 5.3: The datasheet of the TL082 operational amplifier.
Symbol Symbol Value Unit
19
Supply VoltageVCC
VEE
+18
-18V
Differential Input Voltage VID ±30 V
Input Voltage Range VIDR ±15 V
Output Short Circuit Duration tSC Continuous
Power Dissipation
(Plastic Package)
PD
1/8JA
680
10
mW
mW/°C
Operating Ambient
Temperature RageTA 0 - +70 °C
Storage Temperature Range Tstg -65 - +150 °C
Slew rate SR 16 V/μs
Gain bandwidth product GBW 4 MHz
The magnitude of the input voltage must not exceed the magnitude of the supply voltage or
15V, whichever is less. The output may be shorted to ground or either supply. Temperature
and/or supply voltages must be limited to ensure that power dissipation ratings are not
exceeded.
For the 741 operational amplifier, GBW = 1 MHz, SR = 0.5 V/μs.
For the TL082 operational amplifier, GBW = 4 MHz, SR = 16 V/μs.
Vi(t) = 0.04 cos ( 40000 * 2 * Π * t) mV.
Vo(t) = 100 cos ( 40000 * 2 * Π * t) mV.
(Vo(t)) = 2 * Π * 40000 * 0.1 = 0.025 V/μs.′
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0.025 V/μs < 0.5 V/μs the 741 operational amplifier could be used.
0.025 V/μs < 16 V/μs the TL082 operational amplifier could be used.
The TL082 operational amplifier has a better slew rate.
For a 10% error in the frequency, F = 40000 * 0.9 = 36000 Hz.
The required gain bandwidth product for a gain = 2500 is,
GBW = 36000 * 2500 = 90 MHz > 4 MHz.
The signal amplification is split into two stages because of this gain bandwidth product.
The maximum gain G max = 4 MHz / 36000 Hz = 111.11.
The maximum gain is greater than the gain for the first stage 100 and the second stage 25.
5.3.3 Detection circuit
The detection is done to detect the received ultrasonic signal. It is the half-wave rectification
circuit which used the 1N4148 diodes.
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Figure 5.10: The detection circuit.
The DC voltage according to the level of the detection signal is gotten by the capacitor
behind the diode. The 1N4148 diode is used because it is a fast switching diode.
5.5 Power supply and battery
The Ultrasonic transmitter and receiver require four connections to operate. First there are the
power and ground lines. The Ultrasonic transmitter and receiver require a 5V power supply
capable of handling roughly 50mA of continuous output. The remaining two wires are the signal
wires, one to enable or disable the transmitter and the other to get the returned echo. The
microcontroller needs also a 5V to operate. This 5V power supply is got using a regulator. The
user can use a 12V DC power supply or a 9V battery to operate this device illustrated in Figure
5.13.
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Figure 5.13: The power supply circuit.
5.6 Ultrasonic sensors
A market survey has been done to select the best available ultrasonic proximity sensor available
at that time. The following are some of the sensors that have been considered for the
development of this system.
Table 5.5: The Ultrasonic sensor specifications.
Transducer Range Beam
angle
Measurement speed Frequency Sensitivity
SQ-40T/R 10 cm - 3 m 30º 20 ms 40 Khz high
SensComp
600
15 cm –10.7 m 15º 200 ms 50 Khz good
The ultrasonic transducers are optimized for 25 kHz, 32 kHz, 40 kHz or wide bandwidth
transducers. This project uses a 40 kHz transducer but it will still work with the others if the
appropriate changes to the software are being made. The receiver and generator circuits will
work as they are. The 40 kHz signal is easily generated by the microcontroller but detection
requires a sensitive amplifier and a peak detector. Transducers are devices that convert
electrical energy to mechanical energy, or vice versa. The transducer converts received echoes
into analog electrical signals that are output from the transducer. Ultrasonic transducers
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operate to radiate ultrasonic waves through a medium such as air. Transducers generally create
ultrasonic vibrations through the use of piezoelectric materials such as certain forms of crystals
or ceramic polymers. The overall capacitance of a transducer is dependent upon the area and
the thickness of the piezo material.
Ultrasonic transducers are available in various technical forms. Ultrasonic transducers are
typically formed of either piezoelectric elements or of micro-machined ultrasonic
transducer (MUT) elements. For industrial use, solid-state transducers are usually used,
because of their robustness. They basically include a piezoceramic device as an element
for converting between electric signals and acoustic signals and a resonant adapter layer,
with which the transfer of sound to the air is optimized. The piezoelectric elements
typically are made of a piezoelectric ceramic such as lead-zirconate-titanate (PZT), with a
plurality of elements being arranged to form a transducer. Piezoceramic ultrasonic
transducers are the transducers of choice for rugged, industrial applications because they
are efficient and environmentally robust. These sensors have been used in industry for
numerous applications; however have not been capable of short range object detection
until recently. A micro-machined ultrasonic transducer (MUT) is formed using known
semiconductor manufacturing techniques resulting in a capacitive ultrasonic transducer
cell that comprises a flexible membrane supported around its edges over a silicon
substrate. The membrane is supported by the substrate and forms a cavity. The MUT may
be electrically energized to produce an appropriate ultrasonic wave. Similarly, when
electrically biased, the membrane of the MUT may be used to receive ultrasonic signals
by capturing reflected ultrasonic energy and transforming that energy into movement of
the electrically biased membrane, which then generates a receive signal. Capacitive
micro-machined ultrasonic transducers (cMUTs) are tiny diaphragm-like devices with
electrodes that convert the sound vibration of a received ultrasound signal into a
modulated capacitance. For transmission the capacitive charge is modulated to vibrate the
diaphragm of the device and thereby transmit a sound wave. In general, ultrasonic
transducers are constructed by incorporating one or more piezoelectric vibrators which
are electrically connected to pulsing-receiving system. [3]
5.6.1 Electrostatic Ultrasonic Sensors
24
Electrostatic ultrasonic sensors operate similar to an electrical capacitor. These sensors usually
are composed of a fixed conductive plate and a free metallic surface coated with a layer of
insulation that separates the two plates.
When an electric potential is placed across the fixed conductive plate, the free metallic surface
is pulled against the fixed plate. When an oscillating electrical potential is applied to the fixed
plate, the free plate oscillates at a similar frequency thereby creating acoustic pressure waves.
When receiving an ultrasonic signal, the Electrostatic ultrasonic sensors produce a varying
capacitance created by the pressure waves hitting the free metallic surface.
5.6.2 Piezoelectric Ultrasonic Sensors
Piezoelectric ultrasonic Sensors are composed of a Piezo material and an acoustic surface. The
Piezo material can either be a crystal or ceramic. The Piezo material is attached to the acoustic
surface such that any physical changes in the geometry of the material will affect the acoustic
surface.
When an electrical potential is placed across the Piezo material, the geometry changes thereby
disturbing the acoustic surface.
When an oscillating electrical potential is placed across the Piezo material, the acoustic surface
generates an acoustic signal. When receiving an ultrasonic signal, the ultrasonic waves strike the
acoustic surface thereby compressing the Piezo material.
The Piezo material emits electrons when compressed thereby creating an electrical signal.
Piezoelectric materials vibrate in response to alternating voltages of certain frequencies applied
across the material. Piezoelectric elements are similar to common analog capacitors in that
piezo elements generally include two electrodes separated by a piezoelectric material that
functions as a dielectric, shown in Figure 5.14 and the sensitivity with respect to frequency is
described in Figure5.15.[3]
25
Figure 5.14: The SQ-40T/R ultrasonic transducer.
Figure 5.15: The sensitivity of the SQ-40T/R with respect to the frequency.
26
5.7 The schematic of the ultrasonic range meter design:
The functionality of this system can be divided into three main parts as shown in Figure
5.27; the transmitter, the receiver, the microcontroller and the digital display.
The transmitter, enabled via the microcontroller, is designed to activate a 555 oscillator with a
frequency of 40 KHz. The width of the pulse is 0.1 ms, every 40 ms a pulse is transmitted.
One of the most important and sophisticated part of the device is the receiver.
The receiver consists of a signal amplification stage and peak detection stage.
The signal is amplified by a gain of 2500 in order to reduce the noise effect.
In order to reduce the cost of the power supply of the device, the +/- Vcc was avoided and 0-5 V
power supply was used in the design of the signal amplification stage.
The peak detection is used to transform the signal into a pulse.
The microcontroller controls all the parts in the device and performs all the arithmetic
calculations of the distance and displays it on the 7-segment digital display. This process of
distance calculation is continuously repeated as long as the device is turned on.
The laser pointer on the device is used to pinpoint the target in order to get less error caused by
the malfunction use of the device.
The program used in the PCB design is ExpressPCB which is a professional program.
The design of the PCB is splitted into two PCB circuits as shown in Figures 5.28, 5.29; one for the
transmitter and receiver and the other for the microcontroller with transistors used to enable
the 7-segment display.
27
Figure 5.16: The overall schematic of the Ultrasonic range meter.
Figure 5.17: The printed circuit board diagram of the microcontroller.
6.1 Factors affecting the performance of Ultrasonic sensors
Position/distance measurement using ultrasonic sensors is based on the principle of measuring
the time of flight of the ultrasonic waves in a particular medium. There are number of factors
28
which affect the accuracy of measurement and therefore should be taken into consideration
while designing the ultrasonic sensing system. The following are some of the factors.
6.1.1 Radiation pattern:
All ultrasonic sensors have their specific radiation pattern associated with it.
This acoustic radiation pattern is a function of spatial angle called beam angle. Beam angle, Ω
is defined as the total angle between the points at which the sound power reduces to half its
peak value, commonly known as 3 dB points.
The spot diameter of the beam can be formulated as.
D = 2R tan (0.5 Ω) (5.6)
Where, D = spot diameter in centimeters.
R = target range in centimeters.
Ω = beam angle in degrees.
At minimum range, R = 10 cm and Ω = 30º.
D = 2 * 10 * tan (15º) = 5.358 cm.
At maximum range, R = 300 cm and Ω = 30º.
D = 2 * 300 * tan (15º) = 160.769 cm.
Radiation pattern consists of a main lobe and side lobes. Radiation power is dominant mainly in
the front region of the sensor, so as to say that the main lobe is directly in front of the sensor,
followed by side lobes sidewise with null region in between these lobes.
Radiation pattern is mainly determined by factors such as the frequency of operation and the
size, shape and acoustic phase characteristics of the vibrating surface. The beam pattern of the
transducer is independent of its nature as a transmitter or receiver.
29
In most of the application, side lobes are suppressed and narrow beams are used. This
suppression is achieved by the processing system and so, the radiation pattern of the transducer
may not be same as the radiation pattern of the whole ultrasonic sensing system. The
narrowness of the beam pattern is a function of the diameter of the radiating surface to the
wavelength of the sound at the operating frequency. As the D/λ ratio increases, beam narrows
out whereas as D/λ ratio decreases, beam broadens. For most of the application narrow beam is
desired and therefore D/λ ratio should be more. The following Figures 6.1, 6.2 show the
radiation pattern, its main lobe and side lobes with the relative attenuation.
Figure 6.1: Geometric approximation of the ultrasonic beam width.
30
Figure 6.2: Beam pattern with respect to amplitude.
6.1.2 Frequency, wavelength and attenuation:
The frequency of the ultrasonic sensing system is determined by the resonant frequency of the
ultrasonic transducer. The selection of this transducer is made considering number of factors
such as transducer size, measurement resolution, measurement range, background noise and
attenuation. The wavelength of the ultrasonic wave can be found out with the following
formula,
λ = C/f (6.1)
Where λ is the wavelength, C is the velocity of sound equal to 340 m/s at 20º C and f is the
frequency equal to 40 KHz.
C, velocity of sound varies with variation in temperature, pressure, medium type, humidity, air
turbulence, conventional currents. So before calculating the wavelength, the speed of sound is
required to be calculated.
λ = 340/40 = 8.5 mm.
6.2 Environmental factors:
The attenuation of sound power depends on the speed of sound, which depends on many
environmental factors like temperature, medium, pressure, humidity, acoustic interference,
radio frequency interference.
6.2.1 Temperature
The velocity of sound in a medium varies with temperature. So, the time taken by the sound to
echo back to the receiver will vary and since this time of flight is proportional to the measured
31
distance. The measured distance will vary with the variation in temperature. Thus the variation
in temperature introduces errors in the measurement.
The sound wave propagation speed in the air depends on the temperature. So, to measure the
distance more correctly, it is necessary to revise according to the temperature. The sound wave
propagation speed can be calculated using one of the two formulas.
V = 331.5 + 0.6 * T [ m/sec ] (6.2)
T : The temperature (°C)
Table 6.1: The speed of sound at each temperature.
Temperature (°C) in air Speed of sound (m/sec)
-10 325.5
0 331.5
10 337.5
20 343.5
30 349.5
40 355.5
50 361.5
32
300
310
320
330
340
350
360
370
-10 0 10 20 30 40 50
Temperature ºC
Spee
d of
sou
nd m
/s
Figure 6.3: Graph of speed with respect to temperature
In this project, the speed of sound used in this program is 340 m/s because this speed is relative
to the temperature 20 ºC which is an average value. A temperature sensor could be added to
this project with a small manipulation to the program, in order to use the right speed value. In
this way, this device would be used in all atmospheric conditions. [4]
6.2.2 Pressure and humidity
As the pressure reduces, the density of particle in the medium decreases thus providing less and
less resistance to the traveling wave. Although slightly pressure effects the velocity of sound
wave, humidity which is defined as the moisture content in the medium basically has a very little
effect on the velocity of sound but it actually effect the radiating surface. The acoustic pressure
p must satisfy the three-dimensional wave equation.
(6.3)
6.2.3 Medium
33
Velocity of sound depends on the kind of medium the sound travels. Sound speed varies with
different medium. The Table 6.2 summarizes some of the medium with the sound velocity in it.
Table 6.2: The ultrasonic wave speed through different mediums
Medium Speed, m/s at 10°C
Air 331.5
Ammonia 414.8
Argon 301.9
Carbon Dioxide 257.8 (low frequency)
Carbon Disulfide 184.7
Carbon Monoxide 337.1
Chlorine 205.4
Ethylene 313.9
Helium 969.8
Hydrogen 1269.4
Illuminating Gas 490.4
Methane 431.9
Neon 434.9
Nitric Oxide 324.9
Nitrogen 334.06
Nitrous Oxide 261.8
Oxygen 317.2
34
.
6.2.4 Acoustic Interference
If the environment contains number of objects that generates background noise and if this
background noise falls in the sensitive frequency of the receiver of the ultrasonic sensing
system, it will result in erroneous measurement.
This error is more pronounced when the amplitude/power of the background noise is more then
the echo itself resulting in very low SNR (signal to noise ratio), which is undesirable. Typically,
the background noise is less at higher frequency and so narrow beam angles works best in an
area where background noise is high.
6.2.5 Radio Frequency Interference
Radio frequency signal present in the environment also affects the ultrasonic sensing system.
6.3 Target Consideration
The principle of ultrasonic sensing is based on transmission of sound wave followed by the
reflection of the echo. These echoes are summed up at the receiver. The return echo is a
function of target distance, geometry, surface, size, composition, orientation of object/sensor
etc.
6.3.1 Composition
Some of the objects are good reflector and some are good absorber. So the amount of echo
returned back depends on the kind of material the object is composed of. This finally effects the
35
measurement as it varies from object to object for the same fix distance of the target from the
sensor. The object must not be composed of soft surfaces that absorb most of the sound energy.
6.3.2 Size and shape
Size and shape affects the amount of echo reflected back to the receiver. For example, for large
planner object (object size >> beam size) almost all the ultrasonic wave will be reflected back to
the receiver. Whereas in case where the object is very small as compared to the beam size, then
part of the ultrasonic sound wave will be reflected to the receiver and the rest will be lost. The
shape determines the angle at which the ultrasonic wave will be reflected. Common to all
ultrasonic ranging systems is the problem of ultrasonic reflection. With light waves, our eye can
see objects because the incident light energy is scattered by most objects, which means that
some energy will reach our eye, despite the angle of the object to us or to the light source. This
scattering occurs because the roughness of an object's surface is large compared to the
wavelength of light 550 nm. Only with very smooth surfaces such as a mirror does the
reflectivity become highly directional for light rays. Ultrasonic energy has wavelengths much
larger 6.35 mm in comparison. Therefore, ultrasonic waves find almost all large flat surfaces
reflective in nature. The amount of energy returned is strongly dependent on the incident angle
of the sound energy.
Figure 6.4 shows a case where a large object is not detected because the energy is reflected
away from the receiver.
36
Figure 6.4: Undetected large object due to reflection.
6.3.3 Position and Orientation
If the size of object is small as compared to the beam size, then the measurement depends on
the position of the object in the beam region. When object is on the main lobe axis, the
reflected echo reaching to the receiver will be very strong and if it is out of axis, the reflected
echo will be weak.
Although the basic range formula is accurate, there are several factors when considering the
accuracy of the result. Since the speed of sound relies on the temperature, a 10N temperature
difference may cause the range to be in error by 1%.
Geometry also affects range in two major ways. The range equation assumes that the sonar
beam width is negligible. An object may be off center, but normal to the transmitted beam. The
range computed will be correct, but the X-component may be in error. Using the formula: X = R
* sin f (6.4)
At a range of 9 meters and a beam width of 30N, the X component would be 2.33 meters off
center. Figure 6.5 illustrates this.
37
Figure 6.5: Object offset due to ultrasonic beam width.
Another geometric effect is shown in Figure 6.6. When the object is at an angle to the receiver,
the range computed will be to the closest point on the object, not the range from the center line
of the beam. This is called cosine error.
Figure 6.6: Range error due to angle between object and sonar.
38
6.4 Power of the detected signal
We need to calculate the power of the detected laser beam in order to detect the reflection at
the receiver in a maximum distance range. Power of the detected signal is calculated by the
following way:
Pdet = Pult * є * δ * S / (4 * π * R²) (6.5)
Pult is the power of the emitted ultrasonic wave.
S is the object target area that reflected the echo.
R is the distance between the device and the target.
є is the target response to the ultrasonic wave.
δ is the geometric form-factor for propagation of the ultrasonic wave and the response signal
through the ambient media (air, water …).
6.5 Noise
The output of the sensor involves noise, which is primarily introduced because of the
uncertainty of the echo which might comes back from the false object/target. Also the
attenuation of the sonic burst depends on the position of the object/target in the lobe region.
6.6 Errors
In general it is desired to develop the worst case analysis to permit the design of the hand-held
ultrasonic range meter device capable of operation under all conditions with a minimum error
(maximum acceptable error is +/- 3 cm). The errors associated with both calculations and
measurements can be characterized with regard to their accuracy and precision as shown in
Figure 6.7. Accuracy refers to how closely a computed or measured value agrees with the true
39
value. Precision refers to how closely individual computed or measured values agree with each
other.
Figure 6.7: (a) The samples are inaccurate and imprecise. (b) The samples
are accurate and imprecise. (c) The samples are inaccurate and
precise. (d) The samples should be accurate and precise in order
to get the acceptable error.
6.6.1 Truncation errors
The truncation errors are those that result from using an approximation in place of an exact
mathematical procedure.
For a distance that is being measured, the hand-held ultrasonic range meter device showed a
distance R but the real distance was R +/- 3 cm. This means that the error is at its maximum.
40
At a minimum distance range, with the distance equal to 10 cm.
T1 is the real time of the real distance for the echo to propagate, get reflected by the targeted
object then get back to the receiver.
T1 = (0.1 m * 2) / 340 m/s = 588 μs.
T2 is the time captured by the microcontroller for the echo to propagate, get reflected by the
targeted object then get back to the receiver.
T2 = (0.12 m * 2)/ 340 m/s = 705 μs.
Truncation error = ((T2 – T1)/T2) * 100 = 16.6 %. (6.6)
At a maximum distance range, with the distance equal to 300 cm.
T1 is the real time of the real distance for the echo to propagate, get reflected by the targeted
object then get back to the receiver.
T1 = (3 m * 2) / 340 m/s = 17.6 ms.
T2 is the time captured by the microcontroller for the echo to propagate, get reflected by the
targeted object then get back to the receiver.
T2 = (3.07 m * 2)/ 340 m/s = 18.05 ms.
Truncation error = ((T2 – T1)/T2) * 100 = 2.54 %. (6.7)
6.6.2 Cosine error
41
The effect attributable to cosine error occurs with ultrasonic when the position of this ultrasonic
range meter device is not in true alignment with the target. Since the distance to be determined
is relative to the position of the object with respect to the position of the device, any deviation
from true alignment results in an increase in the distance displayed.
CHAPTER 2
CONSTRUCTION AND WORKING
2.1 CONSTRUCTION
Assemble the circuit on a PCB. An actual-size, single-side PCB layout for speed checker
is shown in fig. and its component in other one. Before operation using a multi meter
check whether the power supply output is correct. If yes, apply power supply to the
circuit by flipping switch S3 to ‘on’. In the circuit use long wires for connecting the two
LDRs, so that you can take them out of the PCB and install on one side of the highway,
100metres apart.
42
Install the two laser transmitters (such as laser torches) on the other side of the highway
exactly opposite to the ultrasonic . Reset the circuit by pressing switch S2, so the display
shows ‘0000.’ Using switch S1, select the speed limit (say, 60 kmph) for the highway.
When any vehicle crosses the first laser, ultrasonic will trigger IC. The output of IC goes
high for the time set to cross 100 meters with the selected speed (60 kmph) and LED1
glows during this period. When the vehicle crosses the second laser light, the output of
IC2 goes high and Led2 glows for this period. Buzzer sounds an alarm if the vehicle
crosses the distance between the lasers set ups at more than the selected speed (lesser
period than preset period). The counter starts counting when the first laser beam is
intercepted and stops when the second laser beam is intercepted.
The time taken by the vehicle to cross both the laser beams is displayed on the LCD
display. For 40kmph speed setting, with timer frequency set at 100Hz, if display count is
less than ‘600,’ it means that the vehicle has crossed the speed limit (and simultaneously
the buzzer sounds). Reset the circuit for monitoring the speed vehicle.
2.2 PCB LAYOUT
43
2.3 PCB DESIGNING
Printed circuit board is a piece of art. The performance of an electronics circuit depends
upon layout and design of PCB. Various steps in design of PCB are explained.
44
The general consideration while artwork is discussed below:
PCB is used to rout electrical current & signal through copper track, which are firmly
bounded to an insulating base. The material used for PCB is paper phenolic which is less
costly & used in consumer electronics circuits. Paper phenolic is more resistant to
moisture but difficult to machined drill as glass epoxy.
Rules for Layout
PCB interconnects various electronic components by an interconnection. The general
considerations are:
1. Mechanical considerations, size shape, mounting PCB etc.
2. User system considerations whether for consumer or laboratory or industry.
3. Electrical & electronic parameters such as impedance, gain, electromagnetic
coupling etc.
4. Ease of maintenance.
Designing
Now-a-days PCB has become an important factor during designing various circuits.
Advantages of PCB over normal wiring:
1. PCB is necessary for interconnecting a large no. Of component in very small area
with minimum parasitic wiring effect.
2. PCB is suitable for the mass production with less chance of wiring effect.
3. Wiring is avoided.
4. Servicing is easier.
5. By using PCB, electronic equipment becomes more reliable, small in size & less
costly.
6. Small component are easily mounted on PCB.
7. Construction is neat, small & truly a work of art.
45
2.3.1 Production of PCB manually
To prepare the PCB manually following procedure is accepted:
1. Measure the dimension of components such as resistor, capacitor or diodes.
2. Measure the proper space between terminals of active components such as
transistor, IC’s etc.
3. Decide high density or low-density circuit. Use vertical mounting wherever
possible.
Measure the dimension of components and spacing between terminals of IC’s. Draw the
layout as in artwork using trace paper & carbon paper. Draw the image of figure.
Then cake holes into PCB by using drill machines (after etching is done). Avoid drilling
before etching.
After drying pen ink, keep PCB in FeCl3 solution & add some HCI for faster etching.
After drilling the PCB, draw layout using etching pen of good quality & leave it drying.
During etching unwanted copper is dissolved FeCl3 solution & wanted copper tracks are
saved below ink.
Procedure
The procedure of making of PCB consists of following steps:
(I) Drawing of the lay out.
(II) Printing of PCB
(III) Etching of PCB
Drawing of the layoutWith the circuit diagram and the entire component at hand, we draw a complete lay out
plan on a graph paper. We should care regarding location shape utilization and we keep
the line on the other side as for as possible, we trace the complete layout on a trace paper.
Printing of PCB
46
We cut the referred size of PCB using hawk saw and file. Now we put carbon paper on it.
Since the tracing paper transparent we can now reproduce carbon paint over the carbon
surface by using ball pen over it.
Etching of PCB
Etching is a process of attacking & removing the unprotected & unwanted copper from
PCB to yield desired conductor pattern. The most common etchant used in industry is
ferric chloride. Theoretically any one of following solution can used to etch the board:
1. Ammonium persulphate.
2. Cupric acid
3. Cupric chloride
4. Ferric chloride
Method of etching includes tray rocking, tank etching & spray etching. Out of these, tray
rocking is simplest one. These consist of a tray of Pyrex glass attached to a power-
rocking table, if power-rocking table is not available, rocking of tray with etching
solution can be done manually also.
Ferric chloride crystals of 500 gm. are mixed in water to make a total solution of 1 liter
Cupric & ferric ions precipitate out of solution the room of sludge that tends to settle at
bottom of etching bath. Ideal etch condition requires that etchant be heated to a
temperature between 60-70 degrees.
The PCB is immersed in etchant solution width copper side up in the tray. Only one
board should be etched at a time, as the table is rocked the unprotected copper dissolves.
When etching is completed the board is rinsed under water &then allowed to dry. Using
lacquer thinner or acetic acid or petrol removes the resist material. After the resist has
been removed, clean the copper. After the board is inspected & inspected & approved, it
is ready for whole drilling, component mounting then for soldering.
47
Soldering Technique
Soldering
Soldering is a process for the jointing metal parts with the addition of solder where the
melting temperature is solvated below that of material joined.
Selection of Proper Soldering Iron
There should be a proper soldering iron for each type of job, as we know that metal is a
very good conductor of neat therefore when soldering on a metal, chassis of heavy iron is
used.
But it will not practical to use such type of iron on a PCB used in project because heat
dissipation on the other side could damage a PCB a low wattages (35w)’ soldering iron is
used for this purpose.
Selection of solder
Selection of proper solder wire for the job is the major consideration in the making of
good soldering connections it should be of low melting temperature metal consisting
basically of fin and load with varying amount of other metal such as a antimony and
cadmium to give alloys various physical purpose in the process of joining of two metal
together the solder detach a small amount of surface of each at temperature below there
melting point the action of melting solder on metal is similar to the action of water on salt
generally the composition used fro the solder in 60% tin and 40% lead.
Flux
The application of a proper flux is a necessary link in the soldering chain the metal we
commonly used in electronics is usually converted with a fine non-metallic film called
“oxide”. The major function of the flux is to deal with the metal oxide.
Soldering Technique
48
1. Proper iron should be selected or a special job. A side tipped, high voltage is
necessary when soldering on a metal chassis pen. For PCB repairing a low
wattage pencil iron should be recommended tip of which should be narrow.
2. The iron tip should be kept clean, when iron is used continuously. It is exposed to
air and the tip may become oxidized oxidization can be prevented by keeping the
tip may clean at all the time.
3. When the iron is turned, the tip should be whipped removed any excessive metal
solder. A ray should never be used to write the tip because it may have small
deposit of carbon instead of a commercial tip cleaner.
4. The area to be soldered should clean at all the time. It may look clean. A thin
oxide film may be present and prevent proper soldering only or greasily deposit or
small bit or large material should be cleaned, that may be embedded on the
surface to be soldered purpose.
5. A flat face of a well-sheeted iron should be applied against the surface to be
soldered. This should be heated to a high temperature enough to melt the solder.
6. The solder should be removed first and when the iron on junction should be
distributed or more any portion of it.
7. When the surface is sufficiently heated, the solder is applied to the deposit and not
to melt and flow freely towards the iron.
8. The area around the junction should be checked to any excess solder on tinning
plate, which can cause shorts.
9. The excess of solder should be removed and cleaned.
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CHAPTER3
COMPONENT DESCRIPTION
3.1 RESISTOR
Resistor is a component of an electric circuit that resists the flow of direct or alternating
electric current. Resistors can limit or divide the current, reduce the voltage, protect an
electric circuit, or provide large amounts of heat or light.
An electric current is the movement of charged particles called electrons from one region
to another. The amount of resistance to the flow of current that a resistor causes depends
on the material it is made of as well as its size and shape. Resistors are usually placed in
electric circuits, which are devices formed when current moves through an electrical
conductor.
When a voltage, or electric potential, is applied to opposite ends of a circuit, it causes
current to flow through the circuit. As the current flows, it encounters a certain amount of
resistance from the conductor and any resistors in the circuit. Each material has a
characteristic resistance. For example, wood is a bad conductor because it offers high
resistance to the current; copper is a better conductor because it offers less resistance. In
any electric circuit, the current in the entire circuit is equal to the voltage across that
circuit divided by the resistance of the circuit. Resistors are often made to have a specific
value of resistance so that the characteristics of the circuit can be accurately calculated.
50
Resistors are designed to have a specific value of resistance. Most resistors used in
electric circuits are cylindrical items a few millimeters long with wires at both ends to
connect them to the circuit. Resistors are often color coded by three or four color bands
that indicate the specific value of resistance. Some resistors obey Ohm’s law, which
states that the current density is directly proportional to the electrical field when the
temperature is constant. The resistance of a material that follows Ohm’s law is constant,
or independent of voltage or current, and the relationship between current and voltage is
linear.
3.2 CAPACITOR
Capacitor, or electrical condenser, is a device used for storing an electrical charge. In its
simplest form a capacitor consists of two metal plates separated by a non-conducting
layer called the dielectric. When one plate is charged with electricity from a direct-
current or electrostatic source, the other plate will have induced in it a charge of the
opposite sign; that is, positive if the original charge is negative and negative if the charge
is positive. The electrical size of a capacitor is its capacitance, the amount of electric
charge it can hold.
Capacitors are useful when direct current must be prevented from entering some part of
an electric circuit. Fixed-capacity and variable-capacity capacitors are used in
conjunction with coils as resonant circuits in radios and other electronic equipment.
51
Large capacitors are also employed in power lines to resonate the load on the line and
make it possible for the line to transmit more power.
Capacitors are produced in a wide variety of forms. Air, mica, ceramics, paper, oil, and
vacuums are used as dielectrics, depending on the purpose for which the device is
intended.
3.3 SEMICONDUCTOR DIODE
Circuit Diagram
Diode is a electronic device that allows the passage of current in only one direction. The
diodes, most commonly used in electronic circuits today are semiconductor diodes. The
52
simplest of these, the germanium point-contact diode, dates from the early days of radio,
when the received radio signal was detected by means of a germanium crystal and a fine,
pointed wire that rested on it. In modern germanium (or silicon) point-contact diodes, the
wire and a tiny crystal plate are mounted inside a small glass tube and connected to two
wires that are fused into the ends of the tube.
3.4 LED
A diode is an electronic component through which current passes in only one direction.
Light-emitting diodes (LEDs) are semiconductors that produce light when current passes
through them. They are used in many common devices, such as the tuning indicator on a
radio. An arrangement of seven LEDs in the shape of an ‘8’ can be used to display any
number from 0 to 9. This arrangement is often used on calculators and digital watches.
Light-Emitting Diode (LED), device that emits visible light or infrared radiation when an
electric current passes through it. LEDs are made of semiconductors, or electrical
conductors, mixed with phosphors, substances that absorb electromagnetic radiation and
re-emit it as visible light. When electrical current passes through the diode the
semiconductor emits infrared radiation, which the phosphors in the diode absorb and
53
reemit as visible light. The visible emission is useful for indicator lamps and
alphanumeric displays in various electronic devices and appliances. Devices such as
remote controls and cameras that focus automatically use infrared LEDs, which emit
infrared radiation instead of visible light.
Light-emitting diodes use the properties of electroluminescence, in which certain
substances emit electromagnetic radiation when excited by the flow of an electric current,
and fluorescence, in which some substances absorb wavelengths of electromagnetic
radiation other than visible light and re-emit the radiation as visible light. When charged
particles such as electrons pass through certain semiconductors, they boost to higher
orbits one or more electrons in some of the atoms in the semiconductor. When these
electrons fall back to lower orbits, the atom emits infrared radiation. When this radiation
strikes a phosphor atom, electrons in the phosphor atom jump to higher orbits. The
phosphor atom emits visible light when the electrons fall back to a lower orbit.
54
3.8 VOLTAGE REGULATOR IC 7805
LM78XX Series Voltage Regulators
General Description
The LM78XX series of three terminal regulators is available with several fixed output
voltages making them useful in a wide range of applications. One of these is local on card
regulation, eliminating the distribution problems associated with single point regulation.
The voltages available allow these regulators to be used in logic systems,
instrumentation, Hi-Fi, and other solid state electronic equipment. Although designed
primarily as fixed voltage regulators, these devices can be used with external components
to obtain adjustable voltages and currents.
The LM78XX series is available in an aluminum TO-3 package which will allow over
1.0A load current if adequate heat sinking is provided. Current limiting is included to
limit the peak output current to a safe value. Safe area protection for the output transistor
is provided to limit internal power dissipation. If internal power dissipation becomes too
high for the heat sinking provided, the thermal shutdown circuit takes over preventing the
IC from overheating.
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Considerable effort was expanded to make the LM78XX series of regulators easy to use
and minimize the number of external components. It is not necessary to bypass the
output, although this does improve transient response. Input bypassing is needed only if
the regulator is located far from the filter capacitor of the power supply. For output
voltage other than 5V, 12V and 15V the LM117 series provides an output voltage range
from 1.2V to 57V.
Features
Output current in excess of 1A
Internal thermal overload protection
No external components required
Output transistor safe area protection
Internal short circuit current limit
Available in the aluminum TO-3 package
Voltage Range
LM7805C -5V
LM7812C -12V
LM7815C -15V
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3.9 TRANSFORMER
MUTUAL INDUCTANCE
When current flows through a coil, magnetic field is induced around the coil. When A.C.
Supply is given to coil, then since there is positive and negative half cycles in a A.C.
cycle. So there magnetic fields also attains maximum and minimum values. If we place
another coil in the magnetic fields of first coil then their produces a voltage in expound
coil. Transformer works on that principle.
Coil L1 is connected to A.C. source. This coil is called primary coil. When alternating
current flows through the coil then there induces a alternating magnetic field. In a half
cycle the direction of current through the coil is as shown by arrow, this current makes
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North Pole of upper end of coil L1. As the value of current increases, the magnetic field
cut the turns of coil L2. Due to this there produces a induced Electromagnetic force (emf)
and thus current flows though the load resistance, in this way due to flow of terminating
current in coil L1 there an alternating current flows through coil L2 also.
In transformer both coils are wounded is opposite direction to each other. Here current
starts to flow from upper end of coil L1. This current causes upper end positive. The
induced magnetic field produced produces current in secondary coil L2 and so there
voltage induces. The positive end of induces. The positive end of induced voltage in
secondary is at upper end of secondary and negative end is at lower end of coil. In that
type of transformer the secondary voltage in 180 out of phase with primary voltage. This
relationship is known as signal inversion.
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After completion of first half cycle, the current flow through coil L1 stops for a moment
since at this time input is passing through 180. As current decreases, magnetic fields in
L1 become eliminate. Later on current through coil L1 decrease, there current through
coil L1 also decreases. In next half cycle the current through coil L1 reverses its
direction. Due to this there produces opposite polarity magnetic field through around the
coil. Again this field cuts the turns of coil L2 and produced EMFF in L2. The polarity is
reversed, so polarity of induced voltage in coil L2 in also reversed. In this way in this half
cycle also there current flows through the secondary.
CHAPTER 4
CONCLUSION
The monitoring of speed of the vehicles on the highway is necessary and this model
presents a simple and economical solution to this problem. However there are several
advancements that can be made. One of it is the use of microcontrollers.
We can also use a GSM modem to inform the administering authorities regarding any
over speeding vehicles. In this case the modem will enable the system to send a message
regarding the vehicles identity to the required person on the mobile.
Another system which is being used practically in this field is the Doppler radar. This
system is based on the phenomenon of Doppler Shift to measure to speed of the vehicle.
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Bibliography
BOOK REFERENCES
1. Boylestad , Robert L. and Nashelsky Louis, Electronic Devices and Circuit
Theory, Pearson Education, 2002.
2. Mano Morris M., Digital Design ,Prentice Hall India, New Delhi, 2002.
3. Sedra Adel S. and Smith Kenneth C., Microelectronic Systems,Oxford University
Press,2006.
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WEBSITE REFERENCES
www.geocities.com
www.efymag.com
www.google.com
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