BSc Project

PROJECT REPORT FOR THE EVALUATIONPROJECT REPORT FOR THE EVALUATION OF FINAL YEAR BSc PHYSICSOF FINAL YEAR BSc PHYSICS

EXAMINNATIONEXAMINNATION

TRIVANDRUM

SUBMITTED BY,SUBMITTED BY,

Vijitha IVijitha I

881576881576

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MOBILE BUG DETECTOR

SUBMITTED BY,SUBMITTED BY,

Vijitha IVijitha I

881576881576

UNDER THE GUIDANCE OFUNDER THE GUIDANCE OF

Dr. Deepa MDr. Deepa M

(Lecturer Selection Grade of All Saints’ College)(Lecturer Selection Grade of All Saints’ College)

A report submitted in partial fulfillment ofthe requirements of

BACHELOR’S DEGREE IN PHYSICS UNIVERSITY OF KERALA

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BONAFIED CERTIFICATEBONAFIED CERTIFICATE

TRIVANDRUM

This is to certify that the Project Report titled “Mobile Bug Detector”

submitted by VIJITHA I Register No: 881576 during Final Year of the BSc

Program embodies original work done by her under my guidance and

supervision.

Signature of the Head of the Department Signature of the Lecturer in Charge

Name: Dr. MOLLY ISAAC Name: Dr. DEEPA MDesignation: READER Designation: LECT.SEL.GR.

EXAMINER

1.

2.

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DECLARATION

This is to state that the project titled “Mobile Bug Detector” is based on

the original work carried by me under the guidance of Dr. Deepa M, Lecturer of All

Saints’ College towards the partial fulfillment of the requirements for the BSc course of

University of Kerala (2007 – 2010). This has not been submitted in part or full towards

any other degree or diploma course.

Vijitha I

881576

Signature

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ACKNOWLEDGEMENT

I express my sincere gratitude to the Dr. Deepa M, Lecturer, for the encouragement given to me for doing the Project.

Many people have contributed a great deal to this work. I take this opportunity to express my sincere thanks and gratitude to all of them.

I am thankful to Dr. Molly Isaac, Head of the Department for all the help she has given to me while doing this Project.

I am also thankful to the respondents who have sincerely co-operated with me, without them this work would have been impossible.

I extent my gratitude to all other teachers of Department of Physics for their immense help through out the work and extent my gratitude to all my friends for their encouragement to complete this project work. I also extend my heartfelt thanks to my family and well wishers.

Above all, I thank God Almighty without whose blessings this effort would not have been a reality.

Vijitha I

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CONTENTSCONTENTS

1. Declaration……………………………………………………………………………4

2. Acknowledgement………………………………………………………....................5

3. Abstract……………………………………………………………………………….7

4. CHAPTER 1-

Introduction……………………………………………….....................8

1.1. Objective…………………………………………………………………………9

1.2. Materials Required…………………………………………………………….10

1.3. Limitations……………………………………………………………………...10

5. CHAPTER 2-Details of

Components………………………………………………...11

2.1. Capacitors………………………………………………………………………12

2.2. Integrated Circuit……………………………………………………………...13

2.2.a. CA3140…………………………………………………………………...13

2.2.b. NE555……………………………………………………………………14

2.3. Light Emitting Diode…………………………………………………………..15

2.4. Printed Circuit Board…………………………………………………………16

2.5. Piezo Buzzer……………………………………………………………………17

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2.6. Resistors………………………………………………………………………...18

2.7. Transistor………………………………………………………………………19

2.7.a. BC548…………………………………………………………………….19

6. CHAPTER 3-Circuit

Design………………………………………………………….20

3.1.

Diagram……………………………………………………...............................21

3.2.

Working………………………………………………………………...............22

7. CHAPTER 4-

Conclusion……………………………………………………………..23

8. CHAPTER 5-

Bibliography…………………………………………………………...25

ABSTRACTABSTRACT

The ultimate aim of the project included in the final year BSc degreeThe ultimate aim of the project included in the final year BSc degree

syllabus is to improve students practical and technical knowledge. The project worksyllabus is to improve students practical and technical knowledge. The project work

is more important in evaluation and assessment of our qualifying examination.is more important in evaluation and assessment of our qualifying examination.

Here the project aims to develop a handy, pocket size mobile transmissionHere the project aims to develop a handy, pocket size mobile transmission

detector. The use of mobile phones in examination halls and confidential roomsdetector. The use of mobile phones in examination halls and confidential rooms

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increases day by day. The “mobile bug detector” circuit helps to sense the presenceincreases day by day. The “mobile bug detector” circuit helps to sense the presence

of an activated mobile phone from a distance of one and a- half- metres.of an activated mobile phone from a distance of one and a- half- metres.

The circuit uses a 0.22 The circuit uses a 0.22 µµF disk capacitor to capture the RF signals from theF disk capacitor to capture the RF signals from the

mobile phone. The moment the bug detects the RF transmission signal from anmobile phone. The moment the bug detects the RF transmission signal from an

activated mobile phone, it starts sounding a beep alarm and the LED blinks. Theactivated mobile phone, it starts sounding a beep alarm and the LED blinks. The

unit will give the warning indication if someone uses mobile phone within a radiusunit will give the warning indication if someone uses mobile phone within a radius

of 1.5 metres.of 1.5 metres.

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CHAPTER 1INTRODUCTION

INTRODUCTION

The handy, pocket-size mobile transmission detector can sense the

presence of an activated mobile phone from a distance of one and-a-half metres. So it can

be used to prevent use of mobile phones in examination halls, confidential rooms, etc. It

is also useful for detecting the use of mobile phone for spying and unauthorized video

transmission.

The circuit can detect both the incoming and outgoing calls, SMS and video

transmission even if the mobile phone is kept in the silent mode. The moment the bug

detects RF transmission signal from an activated mobile phone, it starts sounding a beep

alarm and the LED blinks. The alarm continues until the signal transmission ceases.

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An ordinary RF detector using tuned LC circuits is not suitable for detecting

signals in the GHz frequency band used in mobile phones. The transmission frequency of

mobile phones ranges from 0.9 to 3 GHz with a wavelength of 3.3 to 10 cm. So a circuit

detecting gigahertz signals is required for a mobile bug.

Objective

The aim of this project is to design a mobile bug detector. The circuit is

designed to detect unauthorized use of mobile phones in examination halls, confidential

rooms etc. It detects an active phone even in the silent mode. It works up to a distance of

about 1.5 metres.

Materials Required

CAPACITORS- 22pF, 0.22 µF, 100 µF, 47pF, 0.1 µF, 0.01 µF, 4.7 µF

INTEGRATED CIRCUIT- CA 3140, NE555

LIGHT EMITTING DIODE

PRINTED CIRCUIT BOARD

PIEZO-BUZZER

RESISTORS- 2.2 M, 100 K, 1 K, 12 K, 15K

TRANSISTOR- BC 548

12V BATTERY

5- INCH LONG ANTENNA

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Limitations

Limited range- Due to simplicity in design, it can detect cell phone

from a distance of 2 meters radius only. With this design, range

cannot be increased. Detection range depends on the output power

of the GSM handset. With Nokia it is around 2 meters.

The circuit functions properly only if it is assembled carefully on a

common PCB.0.22 µF capacitor is the heart of the circuit. It should

be soldered close to the inputs of IC CA 3140.

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CHAPTER 2DETAILS OF COMPONENTS

CAPACITORS

A Capacitor or condenser is a passive electronic component consisting of a pair of conductors separated by a dielectric (insulator). When a potential difference (voltage) exists across the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the conductors. The effect is greatest when there is a narrow separation between large areas of conductor, hence capacitor conductors are often called plates.

A capacitor consists of two conductors separated by a non-conductive region. The non-conductive substance is called the dielectric medium, although this may also mean a vacuum or a semiconductor depletion region chemically identical to the conductors. A capacitor is assumed to be self-contained and isolated, with no net electric charge and no influence from an external electric field. The conductors thus contain equal and opposite charges on their facing surfaces, and the dielectric contains an electric field. The capacitor is a reasonably general model for electric fields within electric circuits.

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Capacitors are widely used in electronic circuits to block the flow of direct current while allowing alternating current to pass, to filter out interference, to smooth the output of power supplies, and for many other purposes. They are used in resonant circuits in radio frequency equipment to select particular frequencies from a signal with many frequencies.

INTEGRATED CIRCUITINTEGRATED CIRCUIT

An Integrated Circuit is one in which circuit components such as transistors, diodes, resistors, capacitors, etc. are automatically part of a small semiconductor chip. An Integrated Circuit consists of a number of circuit components and their inter connections in a single small package to perform a complete electronic function. These components are formed and connected within a small chip of semiconductor material.

CA3140

The CA3140 are integrated circuit operational amplifiers that combine the advantages of high voltage PMOS transistors with high voltage bipolar transistors on a single monolithic chip. The CA3140 BiMOS operational amplifiers feature gate protected MOSFET (PMOS) transistors in the input circuit to provide very high input impedance, very low input current, and high speed performance. The CA3140 operate at supply voltage from 4V to 36V (either single or dual supply). These operational amplifiers are

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internally phase compensated to achieve stable operation in unity gain follower operation, and additionally, have access terminal for a supplementary external capacitor if additional frequency roll-off is desired. Terminals are also provided for use in applications requiring input offset voltage nulling. The use of PMOS field effect transistors in the input stage results in common mode input voltage capability down to 0.5V below the negative supply terminal, an important attribute for single supply applications. The output stage uses bipolar transistors and includes built-in protection against damage from load terminal short circuiting to either supply rail or to ground.

NE555

The NE555 is a highly stable controller capable of producing accurate timing

pulses. With monostable operation, the time delay is controlled by one external resistor

and one capacitor. With astable operation, the frequency and duty cycle are accurately

controlled with two external resistors and one capacitor.

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LIGHT EMITTING DIODE

A Light-emitting diode (LED) is a semiconductor light source. The LED is based on the semiconductor diode. When a diode is forward biased (switched on), electrons are able to recombine with holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor. An LED is usually small in area (less than 1 mm2), and integrated optical components are used to shape its radiation pattern and assist in reflection. LEDs present many advantages over incandescent light sources including lower energy consumption, longer lifetime,

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improved robustness, smaller size, faster switching, and greater durability and reliability. However, they are relatively expensive and require more precise current and heat management than traditional light sources. Current LED products for general lighting are more expensive to buy than fluorescent lamp sources of comparable output.

The LED consists of a chip of semiconducting material impregnated, or doped, with impurities to create a p-n junction.

PRINTED CIRCUIT BOARD

Printed Circuit Board (PCB) serves as key hardware building blocks for products found in all segments of the electronics market. A PCB supports the components and provides interconnections between them. A PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks, or traces, etched from copper sheets laminated onto a non-conductive substrate.

The board is typically coated with a solder mask that is green in color. Other colors that are normally available are blue and red. The vast majority of printed circuit boards are made by bonding a layer of copper over the entire substrate, sometimes on both sides, then removing unwanted copper after applying a temporary mask, leaving

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only the desired copper traces. A few PCBs are made by adding traces to the bare substrate (or a substrate with a very thin layer of copper) usually by a complex process of multiple electroplating steps. Holes through a PCB are typically drilled with tiny drill bits made of solid tungsten carbide.

PCBs are inexpensive, and can be highly reliable. They require much more layout effort and higher initial cost than either wire-wrapped or point-to-point constructed circuits, but are much cheaper and faster for high-volume production.

PIEZO BUZZER

Piezo Buzzer is a low cost, low power consuming, space saving PCB- mountable device. It can work on a wide range of supply voltages- starting form 1.5V to 27V. It is a self oscillating handy sounder with a variety of sound modes ( continuos, intermittent etc).

The piezo buzzer is a modern signalling device drawing much less current than the older buzzer and bells.

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RESISTORS

A Resistor is a two-terminal electronic component that produces a voltage across its terminals that is proportional to the electric current passing through it. Resistors give electricity to do. Resistors have two leads with no polarity (no positive and negative leads), so the leads are interchangable. Resistors are rated in ohms, indicating how much resistance they offer in a circuit, in watts, indicating the maximum power that they can take.

The primary characteristics of a resistor are the resistance, the tolerance, maximum working voltage and the power rating. Other characteristics include temperature coefficient, noise, and inductance. Critical resistance is the the value below

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which power dissipation limits the maximum permitted current flow, and above which the limit is applied voltage. Critical resistance depends upon the materials constituting the resistor as well as its physical dimensions.

Four-band identification is the most commonly used color-coding scheme on resistors. It consists of four colored bands that are painted around the body of the resistor. The first two bands encode the first two significant digits of the resistance value, the third is a power-of-ten multiplier or number-of-zeroes, and the fourth is the tolerance accuracy, or acceptable error, of the value. The first three bands are equally spaced along the resistor; the spacing to the fourth band is wider.

TRANSISTOR

A Transistor is a semiconductor device used to amplify or switch electronic signals. It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. The transistor is the fundamental building block of modern electronic devices, and its presence is ubiquitous in modern electronic systems.

A transistor consists of two pn junctions formed by sandwiching either p-type or n-type semiconductor between a pair of opposite types. Accordingly there are two types of transistors, namely, npn transistor and pnp transisitor. A transistor (pnp or npn) has three sections of doped semiconductors. The section on one side is the emitter and the

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section on the opposite side is the collector. The middle section is called the base and forms two juinctions between the emitter and collector.

BC 548

The BC548 is a general purpose silicon, NPN, bipolar junction transistor. It is designed to use as general purpose amplifiers and switches requring collector currents to 300 mA.

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CHAPTER 3CIRCUIT DESIGN

DIAGRAM

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WORKING

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The circuit uses a 0.22μF disk capacitor (C3) to capture the RF signals from the mobile phone. The lead length of the capacitor is fixed as 18 mm with a spacing of 8 mm between the leads to get the desired frequency. The disk capacitor along with the leads acts as a small gigahertz loop antenna to collect the RF signals from the mobile phone.

Op-amp IC CA3140 (IC1) is used in the circuit as a current-to-voltage converter with capacitor C3 connected between its inverting and non-inverting inputs. It is a CMOS version using gate-protected p-channel MOSFET transistors in the input to provide very high input impedance, very low input current and very high speed of performance. The output CMOS transistor is capable of swinging the output voltage to within 10 mV of either supply voltage terminal.

Capacitor C3 in conjunction with the lead inductance acts as a transmission line that intercepts the signals from the mobile phone. This capacitor creates a field, stores energy and transfers the stored energy in the form of minute current to the inputs of IC1. This will upset the balanced input of IC1 and convert the current into the corresponding output voltage.

Capacitor C4 along with high-value resistor R1 keeps the non-inverting input stable for easy swing of the output to high state. Resistor R2 provides the discharge path for capacitor C4. Feedback resistor R3 makes the inverting input high when the output becomes high. Capacitor C5 (47pF) is connected across ‘strobe’ (pin 8) and ‘null’ inputs pin 1) of IC1 for phase compensation and gain control to optimise the frequency response.

When the mobile phone signal is detected by C3, the output of IC1 becomes high and low alternately according to the frequency of the signal as indicated by LED1. This triggers monostable timer IC2 through capacitor C7. Capacitor C6 maintains the base bias of transistor T1 for fast switching action. The low-value timing components R6 and C9 produce very short time delay to avoid audio nuisance.

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CHAPTER 4CONCLUSION

CONCLUSION

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The circuit is assembled on a general purpose PCB as compact as possible

and enclose in a small box like junk mobile case. As mentioned earlier, capacitor C3

should have a lead length of 18 mm with lead spacing of 8 mm.

The capacitor is soldered carefully in standing position with equal spacing of the

leads. The response can be optimized by trimming the lead length of C3 for the desired

frequency. A short telescopic type antenna can also be used.

The miniature 12V battery of a remote control is used and a small buzzer to make

the gadget pocket-size. The unit will give the warning indication if someone uses mobile

phone within a radius of 1.5 metres.

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CHAPTER 5BIBLIOGRAPHY

BIBLIOGRAPHY

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1. Digital Electronics TOKHEIM

2. Electronics For You JANUARY 2008 EDITION

3. Electronics Project Vol.20 EFY ENTERPRISES PVT. LTD.

4. Lumped Elements for RF and

Microwave Circuits I.J. BAHL

5. Physical Computing DAN O’SULLIVAN & TOM IGOE

6. Principles of Electronics V.K.MEHTA & ROHIT MEHTA

7. Printed Circuit Assembly Design LEONARD MARKS & JAMES

CATERINA

8. www.datasheetcatalog.com

9. www.electronicsforu.com

10. www.intersil.com

11. en.wikipedia.org

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