Mobile Sniffer Org

CHAPTER 1

INTRODUCTION

1.1 RESISTOR

A resistor is a block or material that limits the flow of current. The greater the

resistance, the lower the current will be, assuming the same voltage imposed on the

resistor. The hydraulic analogy of a resistor would be the pipe with water flowing

through it. The wider the diameter of a pipe, the higher the water flow through the pipe,

assuming the same pressure difference on the terminals of a pipe.

Resistors have two leads (points of contact) to which the resistor can be connected to an

electrical circuit.

The endpoints at the left and right sides of the symbol indicate the points of contact for

the resistor. The ratio of the voltage to current will always be positive, since a higher

voltage on one side of a resistor is a positive voltage, and a current will flow from the

positive side to the negative side, resulting in a positive current. If the voltage is reversed,

the current is reversed, leading again to a positive resistance.

1.2 Capacitor

A capacitor (formerly known as condenser) is a passive two-terminal electrical

component used to store energy in an electric field. The forms of practical capacitors vary

widely, but all contain at least two electrical conductors separated by

a dielectric (insulator); for example, one common construction consists of metal foils

separated by a thin layer of insulating film. Capacitors are widely used as parts

of electrical circuits in many common electrical devices.

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When there is a potential difference (voltage) across the conductors, a

static electric field develops across the dielectric, causing positive charge to collect on

one plate and negative charge on the other plate. Energy is stored in the electrostatic

field. An ideal capacitor is characterized by a single constant value, capacitance,

measured in farads. This is the ratio of the electric charge on each conductor to the

potential difference between them.

The capacitance is greatest when there is a narrow separation between large areas

of conductor, hence capacitor conductors are often called "plates," referring to an early

means of construction. In practice, the dielectric between the plates passes a small

amount of leakage current and also has an electric field strength limit, resulting in

a breakdown voltage, while the conductors and leads introduce an

undesired inductance and resistance.

Capacitors are widely used in electronic circuits for blocking direct current while

allowing alternating current to pass, in filter networks, for smoothing the output of power

supplies, in the resonant circuits that tune radios to particular frequencies and for many

other purposes.

1.3. OP-AMP

An operational amplifier ("op-amp") is a DC-coupled high-gain electronic

voltage amplifier with a differential input and, usually, a single-ended output.[1] An op-

amp produces an output voltage that is typically hundreds of thousands times larger than

the voltage difference between its input terminals.

Operational amplifiers are important building blocks for a wide range of

electronic circuits. They had their origins in analog computers where they were used in

many linear, non-linear and frequency-dependent circuits. Their popularity in circuit

design largely stems from the fact that characteristics of the final op-amp circuits

with negative feedback (such as their gain) are set by external components with little

dependence on temperature changes and manufacturing variations in the op-amp itself.

Op-amps are among the most widely used electronic devices today, being used in

a vast array of consumer, industrial, and scientific devices. Many standard IC op-amps

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cost only a few cents in moderate production volume; however some integrated or hybrid

operational amplifiers with special performance specifications may cost over $100 US in

small quantities. Op-amps may be packaged as components, or used as elements of more

complex integrated circuits.

The op-amp is one type of differential amplifier. Other types of differential

amplifier include the fully differential amplifier (similar to the op-amp, but with two

outputs), the instrumentation amplifier (usually built from three op-amps), the isolation

amplifier (similar to the instrumentation amplifier, but with tolerance to common-mode

voltages that would destroy an ordinary op-amp), and negative feedback

amplifier (usually built from one or more op-amps and a resistive feedback network).

1.4 TRANSISTOR:

A transistor is a semi-conductor device used to amplify and switch electronic signals

and power. It is composed of a semiconductor material with at least three terminals for

connection to an external circuit. A voltage or current applied to one pair of the

transistor's terminals changes the current flowing through another pair of terminals.

Because the controlled (output) power can be much more than the controlling (input)

power, a transistor can amplify a signal. Today, some transistors are packaged

individually, but many more are found embedded in integrated circuits.

The transistor is the fundamental building block of modern electronic devices, and

is ubiquitous in modern electronic systems. Following its release in the early 1950s the

transistor revolutionized the field of electronics, and paved the way for smaller and

cheaper radios, calculators, and computers, among other things.

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CHAPTER 2

COMPONENT LIST

Ic’s

1. Ic CA3130

2. Ic NE555

Resistors

1.100 kΩ

2. 2.2 MΩ --- 2 no’s

3.15 kΩ

4.12 kΩ --- 2 no’s

5. 1 kΩ

Capacitor

1. 22 pF ---- 2 no’s

2. 0.22 µF

3.100 µF

4. 47 pF

5. 0.1 µF --- 3 no’s

6. 4.7 µF

Antenna

TELESCOPIC AREAL ANTENNA

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Transistor

BC 548

LED’s

Red led

Buzzer

Piezo buzzer

Battery

12v, battery

Switch

Two pin on/off switch

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CHAPTER 3

HARDWARE DESCRIPTION

3.1. IC’s

An integrated circuit or monolithic integrated circuit (also referred to as IC, chip,

and microchip) is an electronic circuit manufactured by the patterned diffusion of trace

elements into the surface of a thin substrate of semiconductor material.

Integrated circuits are used in virtually all electronic equipment today and have

revolutionized the world of electronics. Computers, cellular phones, and other digital

appliances are now inextricable parts of the structure of modern societies, made possible

by the low cost of production of integrated circuits.

In this project we are using Two Ic’s which are explained below.

3.1.1 CA3130

CA3130 is op amp that combine, the advantage of both CMOS and bipolar

transistors.

Gate-protected P-Channel MOSFET (PMOS) transistors are used in the input

circuit to provide very-high-input impedance, very-low-input current and exceptional

speed performance. The use of PMOS transistors in the input stage results in common-

mode input-voltage capability down to 0.5V below, the negative-supply terminal, an

important attribute in single-supply applications.

A CMOS transistor-pair, capable of swinging the output voltage to within 10mV

of either supply-voltage terminal (at very high values of load impedance), is employed as

the output circuit. The CA3130 Series circuits operate at supply voltages ranging from

5V to 16V, (±2.5V to±8V). They can be phase compensated with a single external

capacitor, and have terminals for adjustment of offset voltage for applications requiring

offset-null capability. Terminal provisions are also made to permit strobing of the output

stage

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Pinout diagram

Figure: 3.1.1 Pinout out diagram of CA3130

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Features

MOSFET Input Stage Provides:

- Very High ZI = 1.5 TΩ (1.5 x 1012Ω) (Type)

- Very Low II . . . . . . . . . . . . . 5pA (Type) at 15V Operation

. . . . . . . . . . . . . . . . . . . . . = 2pA (Type) at 5V Operation

Ideal for Single-Supply Applications

Common-Mode Input-Voltage Range Includes Negative Supply Rail; Input

Terminals can be Swung 0.5V

Below Negative Supply Rail

CMOS Output Stage Permits Signal Swing to Either (or both) Supply Rails

Applications

Ground-Referenced Single Supply Amplifiers

High-Input-Impedance Comparators (Ideal Interface with Digital CMOS)

High-Input-Impedance Wideband Amplifiers

Voltage Followers (e.g. Follower for Single-Supply D/A Converter)

Voltage Regulators (Permits Control of Output Voltage Down to 0V)

Peak Detectors

3.1.2 NE555

Figure:3.1.2 pin out diagram of Ne555

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The connection of the pins for a DIP package is as follows:

Pin Name Purpose

1 GND Ground, low level (0 V)

2 TRIG OUT rises, and interval starts, when this input falls

below 1/3 VCC.

3 OUT This output is driven to +VCC or GND.

4 RESET A timing interval may be interrupted by driving this input

to GND.

5 CTRL "Control" access to the internal voltage divider (by default,

2/3 VCC).

6 THR The interval ends when the voltage at THR is greater than

at CTRL.

7 DIS Open collector output; may discharge a capacitor between

intervals

8 V+, VCC Positive supply voltage is usually between 3 and 15 V.

The 555 has three operating modes:

Monostable mode: in this mode, the 555 functions as a "one-shot" pulse generator.

Applications include timers, missing pulse detection, bounce free switches, touch

switches, frequency divider, capacitance measurement, pulse-width modulation (PWM)

and so on.

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Astable: free running mode: the 555 can operate as an oscillator. Uses include LED

and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse

position modulation and so on.

Selecting a thermistor as timing resistor allows the use of the 555 in a

temperature sensor: the period of the output pulse is determined by the temperature. The

use of a microprocessor based circuit can then convert the pulse period to temperature,

linearize it and even provide calibration means.

Bistable mode or Schmitt trigger: the 555 can operate as a flip-flop, if the DIS

pin is not connected and no capacitor is used. Uses include bounce-free latched switches.

In the monostable mode, the 555 timer acts as a "one-shot" pulse generator.

The pulse begins when the 555 timer receives a signal at the trigger input that falls below

a third of the voltage supply. The width of the output pulse is determined by the time

constant of an RC network, which consists of a capacitor (C) and a resistor (R). The

output pulse ends when the voltage on the capacitor equals 2/3 of the supply voltage. The

output pulse width can be lengthened or shortened to the need of the specific application

by adjusting the values of R and C.

The output pulse width of time t, which is the time it takes to charge C to 2/3 of

the supply voltage, is given by

T = RC\ln(3) \approx 1.1 RC

where, t is in seconds, R is in ohms and C is in farads.

While using the timer IC in monostable mode, the main disadvantage is that the

time span between the two triggering pulses must be greater than the RC time constant.

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3.2 Resistors

Figure:3.2.1 Resistor

A device used in electrical circuits to maintain a constant relation between current

flow and voltage. Resistors are used to step up or lower the voltage at different points in a

circuit and to transform a current signal into a voltage signal or vice versa, among other

uses. The electrical behavior of a resistor obeys Ohm's law for a constant resistance;

however, some resistors are sensitive to heat, light, or other variables. Variable resistors,

or rheostats, have a resistance that may be varied across a certain range, usually by means

of a mechanical device that alters the position of one terminal of the resistor along a strip

of resistant material. The length of the intervening material determines the resistance.

Figure: 3.2.2 internal diagram of Resistor

Mechanical variable resistors are also called potentiometers, and are used in the

volume knobs of audio equipment and in many other devices.

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Figure: 3.2.3Three terminal resistor

It has three terminals. Resistance can be varied using this potentiometer

3.3 Capacitors

Figure: 3.3.1 Types of capacitors

A capacitor which is an energy-storage device is used to store energy between

two conductors. These conductors are also called plates. An insulator is placed between

these two plates. These plates are charged in order to store energy. One of the main

functions of a capacitor is to work as a filter. In this process blocks DC (Direct Current)

and passes AC (Alternating Current).

A capacitor (formerly known as condenser) is a device for storing electric charge.

The forms of practical capacitors vary widely, but all contain at least two conductors

separated by a non-conductor. Capacitors used as parts of electrical systems, for example,

consist of metal foils separated by a layer of insulating film.

A capacitor is a passive electronic component consisting of a pair separated by a

dielectric (insulator). When there is a potential difference (voltage) across the conductors,

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a static electric field develops across the dielectric, causing positive charge to collect on

one plate and negative charge on the other plate. Energy is stored in the electrostatic

field. An ideal capacitor is characterized by a single constant value, capacitance,

measured in farads. This is the ratio of the electric charge on each conductor to the

potential difference between them.

Capacitors are widely used in electronic circuits for blocking direct current while

allowing alternating current to pass, in filter networks, for smoothing the output of power

supplies, in the resonant circuits that tune radios to particular frequencies and for many

other purposes.

The capacitance is greatest when there is a narrow separation between large areas

of conductor, hence capacitor conductors are often called "plates", referring to an early

means of construction. In practice the dielectric between the plates passes a small amount

of leakage current and also has an electric field strength limit, resulting in a breakdown

voltage, while the conductors and leads introduce an undesired inductance and resistance.

Figure:3.3.2 capacitor

The above picture shows the basic diagram of capacitor.

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3.4 Antenna

An antenna (or aerial) is an electrical device which couples radio waves in free space to an

electrical current used by a radio receiver or transmitter. In reception, the antenna intercepts

some of the power of an electromagnetic wave in order to produce a tiny voltage that the radio

receiver can amplify.

Figure:3.4.1 Antenna

Alternatively, a radio transmitter will produce a large radio frequency current that may

be applied to the terminals of the same antenna in order to convert it into an electromagnetic

wave (radio wave) radiated into free space. Antennas are thus essential to the operation of all

radio equipment, both transmitters and receivers. They are used in systems such as radio and

television broadcasting, two-way radio, wireless LAN, mobile telephony, radar, and satellite

communications.

Typically an antenna consists of an arrangement of metallic conductors (or

"elements") with an electrical connection (often through a transmission line) to the

receiver or transmitter. A current forced through such a conductor by a radio transmitter

will create an alternating magnetic field according to Ampere's law. Or the alternating

magnetic field due to a distant radio transmitter will induce a voltage at the antenna

terminals, according to Faraday's law, which is connected to the input of a receiver. In the

so-called far field, at a considerable distance away from the antenna, the oscillating

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magnetic field is coupled with a similarly oscillating electric field; together these define

an electromagnetic wave which is capable of propagating great distances.

Light is one example of electromagnetic radiation, along with infrared and x-rays,

while radio waves differ only in their much lower frequency (and much longer

wavelength). Electronic circuits can operate at these lower frequencies, processing radio

signals conducted through wires. But it is only through antennas that those radio

frequency electrical signals are converted to (and from) propagating radio waves.

Depending on the design of the antenna, radio waves can be sent toward and received

from all directions ("omnidirectional"), whereas a directional or beam antenna is

designed to operate in a particular direction.

The first antennas were built in 1888 by Heinrich Hertz (1857–1894) in his

pioneering experiments to prove the existence of electromagnetic waves predicted by the

theory of James Clerk Maxwell. Hertz placed dipole antennas at the focal point of

parabolic reflectors for both transmitting and receiving.

3.5 Transistors

Transistors amplify current, for example they can be used to amplify the small

output current from a logic IC so that it can operate a lamp, relay or other high current

device. In many circuits a resistor is used to convert the changing current to a changing

voltage, so the transistor is being used to amplify voltage.

A transistor may be used as a switch (either fully on with maximum current, or fully off

with no current) and as an amplifier (always partly on).

Types of transistor:

There are two types of standard transistors, NPN and PNP, with different

circuit symbols. The letters refer to the layers of semiconductor material used to make

the transistor. Most transistors used today are NPN because this is the easiest type to

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make from silicon. If you are new to electronics it is best to start by learning how to use

NPN transistors.

Figure:3.5.1 Transistor circuit symbols

The leads are labeled base (B), collector (C) and emitter (E).

These terms refer to the internal operation of a transistor but they are not much

help in understanding how a transistor is used, so just treat them as labels!

A Darlington pair is two transistors connected together to give a very high current gain.

In addition to standard (bipolar junction) transistors, there are field-effect transistors

which are usually referred to as FETs.

3.5.1 BC 548

Figure:3.5.2 transistor BC 548

BC548 is .general purpose silicon, NPN, bipolar junction transistor. It is used for

amplification and switching purposes. The current gain may vary between 110 and

800. The maximum DC current gain is 800.

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Its equivalent transistors are 2N3904 and 2SC1815. These equivalent transistors

however have different lead assignments. The variants of BC548 are 548A, 548B and

548C which vary in range of current gain and other characteristics.

The transistor terminals require a fixed DC voltage to operate in the desired region

of its characteristic curves. This is known as the biasing. For amplification applications,

the transistor is biased such that it is partly on for all input conditions. The input signal at

base is amplified and taken at the emitter. BC548 is used in common emitter

configuration for amplifiers. The voltage divider is the commonly used biasing mode. For

switching applications, transistor is biased so that it remains fully on if there is a signal at

its base. In the absence of base signal, it gets completely off.

3.6 Piezo buzzer

Figure:3.6.1piezo buzzer

The piezo buzzer produces sound based on reverse of the piezoelectric effect. The

generation of pressure variation or strain by the application of electric potential across a

piezoelectric material is the underlying principle. These buzzers can be used alert a user

of an event corresponding to a switching action, counter signal or sensor input. They are

also used in alarm circuits.

The buzzer produces a same noisy sound irrespective of the voltage variation applied to it. It consists of piezo crystals between two conductors. When a potential is applied across these crystals, they push on one conductor and pull on the other. This,

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push and pull action, results in a sound wave. Most buzzers produce sound in the range of 2 to 4 kHz.

3.7. LED

Figure:3.7.1 Led

Circuit symbol:

Figure:3.7.2. Led circuit symbol

Function

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as

indicator lamps in many devices and are increasingly used for other lighting. Introduced

as a practical electronic component in 1962, early LEDs emitted low-intensity red light,

but modern versions are available across the visible, ultraviolet,and infrared wavelengths,

with very high brightness.

When a light-emitting diode is forward-biased (switched on), electrons are able

to recombine with electron 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. LEDs are often small in area (less than 1 mm2), and integrated optical

components may be used to shape its radiation pattern.

L EDs present many advantages over incandescent light sources including lower

energy consumption, longer lifetime, improved robustness, smaller size, and faster

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switching. LEDs powerful enough for room lighting are relatively expensive and require

more precise current and heat management than compact fluorescent lamp sources of

comparable output.

Light-emitting diodes are used in applications as diverse as replacements

for aviation lighting, automotive lighting (in particular brake lamps, turn signals,

and indicators) as well as in traffic signals. LEDs have allowed new text, video displays,

and sensors to be developed, while their high switching rates are also useful in advanced

communications technology. Infrared LEDs are also used in the remote control units of

many commercial products including televisions, DVD players, and other domestic

appliances.

LEDs emit light when an electric current passes through them. LEDs must be

connected the correct way round, the diagram may be labelled or + for anode

and k or - for cathode (yes, it really is k, not c, for cathode!). The cathode is the short lead

and there may be a slight flat on the body of round LEDs. If you can see inside the LED

the cathode is the larger electrode (but this is not an official identification method).

LEDs can be damaged by heat when soldering, but the risk is small unless you are

very slow. No special precautions are needed for soldering most LEDs.

3.8. BATTERY

Figure: 3.8 battery.

An electrical battery is one or more electrochemical cells that convert stored

chemical energy into electrical energy. Since the invention of the first battery (or "voltaic

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pile") in 1800 by Alessandro Volta, batteries have become a common power source for

many household and industrial applications. According to a 2005 estimate, the worldwide

battery industry generates US$48 billion in sales each year, with 6% annual growth.

There are two types of batteries: primary batteries (disposable batteries), which are

designed to be used once and discarded, and secondary batteries (rechargeable batteries),

which are designed to be recharged and used multiple times. Batteries come in many

sizes, from miniature cells used to power hearing aids and wristwatches to battery banks

the size of rooms that provide standby power for telephone exchanges and computer data

centers.

3.9 Switch

Figure: 3.9.1 On/Off switch

An electrical switch is any device used to interrupt the flow of electrons in a

circuit. Switches are essentially binary devices: they are either completely on ("closed") or

completely off ("open"). There are many different types of switches, and we will explore

some of these types in this chapter.

Though it may seem strange to cover this elementary electrical topic at such a late

stage in this book series, I do so because the chapters that follow explore an older realm

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of digital technology based on mechanical switch contacts rather than solid-state gate

circuits, and a thorough understanding of switch types is necessary for the undertaking.

Learning the function of switch-based circuits at the same time that you learn about solid-

state logic gates makes both topics easier to grasp, and sets the stage for an enhanced

learning experience in Boolean algebra, the mathematics behind digital logic circuits.

CHAPTER 4

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WORKING

Mobile phone uses RF with a wavelength of 30cm at 872 to 2170 MHz That is

the signal is high frequency with huge energy. When the mobile phone is active, it

transmits the signal in the form of sine wave which passes through the space. T he

encoded audio/video signal contains electromagnetic radiation which is picked up by the

receiver in the base station. Mobile phone system is referred to as “Cellular Telephone

system” because the coverage area is divided into “cells” each of which has a base

station. The transmitter power of the modern 2G antenna in the base station is 20-100

watts.

AM Radio uses frequencies between 180 kHz and 1.6 MHz. FM radio uses 88 to

180 MHz TV uses 470 to 854 MHz Waves at higher frequencies but within the RF region

is called Micro waves. Mobile phone uses high frequency RF wave in the micro wave

region carrying huge amount of electromagnetic energy. That is why burning sensation

develops in the ear if the mobile is used for a long period. Just like a micro wave oven,

mobile phone is ‘cooking’ the tissues in the ear. RF radiation from the phone causes

oscillation of polar molecules like water in the tissues. This generates heat through

friction just like the principle of microwave oven. The strongest radiation from the

mobile phone is about 2 watts which can make connection with a base station located 2 to

3 km away.

Ordinary LC (Coil-Capacitor) circuits are used to detect low frequency radiation in

the AM and FM bands. The tuned tank circuit having a coil and a variable capacitor

retrieve the signal from the carrier wave. But such LC circuits cannot detect high

frequency waves near the microwave region. Hence in the circuit, a capacitor is used to

detect RF from mobile phone considering that, a capacitor can store energy even from an

outside source and oscillate like LC circuit.

4.1 USE OF CAPACITOR

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The non polarized disc capacitor is used to pass AC and not DC. Capacitor can

store energy and pass AC signals during discharge. 0.22 capacitor is selected because it is

a low value one and has large surface area to accept energy from the mobile radiation. To

detect the signal, the sensor part should be like an aerial. So the capacitor is arranged as a

mini loop aerial (similar to the dipole antenna used in TV).In short with this arrangement,

the capacitor works like an air core coil with ability to oscillate and discharge current.

One lead of the capacitor gets DC from the positive rail and the other lead goes to

the negative input of IC1. So the capacitor gets energy for storage. This energy is applied

to the inputs of IC1 so that the inputs of IC are almost balanced with 1.4 volts. In this

state output is zero. But at any time IC can give a high output if a small current is induced

to its inputs. There a natural electromagnetic field around the capacitor caused by the

50Hz from electrical wiring. When the mobile phone radiates high energy pulsations,

capacitor oscillates and release energy in the inputs of IC. This oscillation is indicated by

the flashing of the LED and beeping of Buzzer. In short, capacitor carries energy and is in

an electromagnetic field. So a slight change in field caused by the RF from phone will

disturb the field and forces the capacitor to release energy.

4.2 Demo circuit

IC1 is designed as a differential amplifier Non-inverting input is connected to the

potential divider R1, R2. Capacitor C2 keeps the non inverting input signal stable for

easy swing to + or – R3 is the feedback resistor IC1 functions as a current to voltage

converter, since it converts the tiny current released by the 0.22 capacitor as output

voltage.

At power on LED glows for a moment as IC1 gives a small ouput due to

difference in voltage caused by the capacitor which is on the process of charging as

capacitor C1 charges both the inputs of the IC1 get equal voltage and thus output current

is 0.

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Figure: 4.2.1 Demo circuit

When the high frequency radiation from the mobile phone is sensed by the

circuit, 0.22 cap discharges its stored current to the + input of IC1 and its output goes

high momentarily. (In the standby state, output of the differential amplifier is low since

both inputs get equal voltage of 0.5 volts or more). Any increase in voltage at + input will

change the output state to high.

4.3. FULL CIRCUIT

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R1 1M

R2 100K

C1 0.22

C2 47 UF

R3 1M

LED

IC 3130

Figure: 4.3.1 circuit diagram of mobile sniffer

Normally IC1 is off. So IC2 will be also off. When the power is switched on, as

stated above, IC1 will give a high output and T1 conducts to trigger LED and Buzzer.

This can be a good indication for the working of the circuit.

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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 sniffer. Here 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 CA3130 (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 0 and ‘null’ inputs (pin 1) of

IC1 (can be done away with).

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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 is then amplified by a transistor and thus triggers monostable timer IC2 through

capacitor C7.

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CHAPTER 5

Limitations, Applications And Conclusion

Limitations:

"RANGE" The prototype version has only limited range of 1 -1.5 meters. But if a

preamplifier stage using JFET or MOSFET transistor is used as an interface between the

capacitor and IC, range can be increased.

Applications:

The presence of an activated mobile phone from distance to distance of eight

meters to prevent the use of mobile phones in the examination halls,

confidential rooms ,Etc……

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

video transmission.

Conclusion:

When the mobile phone is on or activated the RF transmission signal is detected by

the detector(diode) and starts sounding a beep alarm ,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 range of this detector can be extended to 1.5

meter by placing two identical mobile sniffers in a room.

This project can be extended by adding number or network detector.

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CHAPTER:6

Bibliography

www.efymag.com

www.alldatasheets.com

www.wikipedia.com

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