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1.1 Introduction

This project is a simple mobile phone detector. This is the handy cell phone detector, pocket size

mobile transmission sniffer that can sense the presence of an active cell phone in a radius of 1m -

1.5m.

As the cellphone sends or receives a message or a call, it sends off a signal. This signal is

detected by our circuit and will cause LED to blink, and. buzzer to sound. This is the basic

principle of this project. This is the simple circuit that can detect any cellphone activities like

sending or receiving calls or SMS or any video transmissions.

1.2 Working Principle

The transmission frequency of a mobile ranges from 0.9GHZ - 3GHZ. So a circuit

capable of detecting gigahertz signals is needed. Here, the circuit uses a 0.20uF disk capacitor

(C3) to capture the RF signals from the mobile phone. The disk capacitor along with its leads

from a small gigahertz loop to catch the signals.

The IC CA3130 (IC1) is an op-amp that is used in this circuit as a current to voltage converter

with the capacitor C3 connected between its inverting and non-inverting inputs. The IC1

provides the base voltage to the transistor Q1.

Capacitor C5 (47pf) is connected across strobe (pin 8) and null inputs (pin 1) of IC1 for phase

compensation and gain control to optimize the frequency of the signals. As the capacitor C3

receives the signal, the output of IC1 becomes high and low alternatively depending on the

frequency of the signal as indicated by LED1. This triggers the monostable timer IC NE555

(IC2) through the capacitor C7. Capacitor C6 (0.1microFarad) maintains the base-bias of

transistor T1 for fast switching action. The low-value timing components R6 (16K) and C9 (4.7

micro farad) produces a very short time delay to avoid audio nuisance. Thus the LED starts

blinking and the piezoelectric buzzer starts sounding as soon as the signal is received.

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1.3 Block Diagran

Fig.1.1: Block Diagram of Mobile Detector

3

1.4 Schematic Diagram:

Fig.1.2: Schematic Diagram of Mobile Detector

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First of all, we get 230V AC supply from switch. After that 230V AC supply is passed through

the step down center tapped transformer so that 12V AC supply is obtained which is passed to

bridge wave rectifier to convert 12V AC to 12V DC. Now 12V DC supply is go to a capacitor

which act as a filter. Then, DC supply is go to LM7812 voltage regulator which gives fix 12V

DC supply. This is indicated by green LED (D2).

This 12V DC is applied to the rest of the circuit through a push-button On-Off switch (DSW1).

Here, the circuit uses a 0.20uF disk capacitor (C3) to capture the RF signals from the mobile

phone. The disk capacitor along with its leads from a small gigahertz loop to catch the signals.

The IC CA3130 (IC1) is an op-amp that is used in this circuit as a current to voltage converter

with the capacitor C3 connected between its inverting and non-inverting inputs. The IC1

provides the base voltage to the transistor Q1.

Capacitor C5 (47pf) is connected across strobe (pin 8) and null inputs (pin 1) of IC1 for phase

compensation and gain control to optimize the frequency of the signals. As the capacitor C3

receives the signal, the output of IC1 becomes high and low alternatively depending on the

frequency of the signal as indicated by LED1. This triggers the monostable timer IC NE555

(IC2) through the capacitor C7. Capacitor C6 (0.1microFarad) maintains the base-bias of

transistor T1 for fast switching action. The low-value timing components R6 (16K) and C9 (4.7

micro farad) produces a very short time delay to avoid audio nuisance. Thus the LED starts

blinking and the piezoelectric buzzer starts sounding as soon as the signal is received.

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2.1 Literature Review

This paper describes several approaches developments of mobile including the concept of

detection and adaptation for mobile content.

Mandeep Singh et al. Has given a paper in this is a mobile machine that can detect and follow

the line drawn on floor generally the path is predefined and can be visible like a black line on a

white surface. Light dependent resistor (LDR) sensors that installs under the robot. This paper

presents a real time detection of mobile phones in restricted area. Mobile transmission detector

can sense the presence of an activated mobile phone from a distance of about one and half

meters. If anyone is using mobile in these range then it will give alarm and robot will stop at that

location. If an obstacle comes the path of robot it gives alarm.[1]

K. Mohan Dece et al.in 2012, has proposed an paper which relates the novel mobile detector

sensing, alarming and reporting system is to find the mobile phone in and around some distance

in restricted areas such as prisons, colleges, schools, hospitals, petrol bunks etc. When anyone

mobile is used in the prohibited place this device will detect that mobile signals through the

antenna. In that particular place when a mobile signal is received, the receiver in the device will

receive the signal through the antenna when a mobile receive the signal at a particular place the

alarm makes the sound for indication of the mobile and one LED will glow for the indication that

with this device GSM module is attached to send this short message service (SMS) to the

registered number to the micro controller. This detector is used to detect the presence of mobile,

when it detect any mobile it gives the signal to the PIC16F877A micro controller. The controller

when receives the signal will turn on the buzzer circuit and will also send the detected message

to some particular mobile number via the GSM module. Also the information displayed in the

LCD module as MOBILE DETECTED [2].

Christian C. Mbaocha et al. in 2012 given a paper for ubiquity of the cell phone has made

communication easier and faster, integrating the world into a global village as people who are in

different geographic location are connected in seconds, its great to be able to call anyone at any

time. There is a great need to limit the use of cellphone at particular places and at particular

times. Hence the use of intelligent mobile phone detector is guaranteed. These work concentrates

in designing a system that will decade the presence of GSM signals from an authorized user in

restricted areas which will in turn trigger another device to restrict the user from service. The

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system will be able to jam GSM frequency signal apart detection to prevent the transmitted

signal from getting to the users cell phone [3].

Gary Fernandes in 2012, has given a paper in which it uses an operational amplifier (op-amp)

to sense the presence of an activated cell phone from a distance of several meters, the simple

circuit can detect any activity of a mobile phone such as incoming and outgoing voice, voice

mail, texting, and data. If a cell phone signal is detected the circuit will blink a LED and or a

sound buzzer. Keep in mind that the phone must be transmitted and the only time a phone is

transmitting is when it is receiving voice, text, internet or data. The sensitivity can be adjusted on

the circuit by adjusting the potentiometer. These circuit is made very simple using the least

amount of components. The components used are very inexpensive and readily available [4].

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3.1 Problem Identification

The main objective of this project is to detect an activated mobile phone use from a radius

of 1 meter and 1 an half meter. This can be used in the places where the use of mobile

phone is prohibited like examination halls, confidential rooms, petrol pumps, meetings etc.

Some common problems with the mobile phone detector are detection of one mobile phone at a

time.

Most cellular phone detectors available today only alarms if there is a cellular phone or

transmission device in the general area. They appeared to alarm randomly and arent very

accurate.

Detecting a cellular phone signal using an accurate signal detection technique is the focus of

these research and can be solved by using a down converter in conjunction with a band-pass

filter. The technique is more accurate and provides signal detection at a lower frequency making

it easier to work with.

If these solution was implemented, it would greatly reduce the risk of cellular phones getting into

secure facilities. Business and government would save a lot of money on security.

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4.1 Hardware Description:

4.1.1Hardware Required

COMPONENTS REQUIRED QUANTITY

IC CA3130 1

IC NE555/LM555 1

TRANSISTOR BC548 1

VOLTAGE REGULATOR (IC7812) 1

STEP-DOWN TRANSFORMER (12-0-12) 1

DIODES(1N4007) 4

LED

o RED 1

o GREEN 1

PIEZO BUZZER 1

ON/OFF SWITCH 1

RESISTORS

o 2.2M 2

o 100K 1

o 1K 1

o 12K 1

o 16K 1

o 4K 1

CAPACITORS

o 22p (DISK/CERAMIC) 2

o 100u (16V) 1

o 47p 1

o 4.7u(16V) 1

o 0.1u 6

o 0.01u 1

o 470u 1

o PCB(copper -cladded board) 1

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4.1.2 IC CA 3130 (Current to Voltage Converter)

This IC is a 15 MHz BiMOS Operational amplifier with MOSFET inputs and Bipolar output.

The inputs contain MOSFET transistors to provide very high input impedance and very low

input current as low as 10pA. It has high speed of performance and suitable for low input current

applications.

Fig.4.1: Pin diagram of CA3130

CA3130A and CA3130 are op amps 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 to0.5V 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. The CA3130A offers superior

input characteristics over those of the CA3130.

4.1.2.1Features of IC CA 3130

MOSFET Input Stage Provides:

- Very High ZI = 1.5 T

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- Very Low current . . . . . . =5pA at 15V Operation

Ideal for Single-Supply Applications

Common-Mode Input-Voltage Range Includes Negative Supply Rail; Input Terminals can be

Swung 0.5VBelow Negative Supply Rail

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

4.1.2.2Applications

Ground-Referenced Single Supply Amplifiers

Fast Sample-Hold Amplifiers

Long-Duration Timers/ Mono stables

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

Single-Supply Full-Wave Precision Rectifiers

Photo-Diode Sensor Amplifiers

4.1.3 IC NE555 Timer

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and

oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-

flop element. Derivatives provide up to four timing circuits in one package.

4.1.3.1 Pin Diagram of IC NE555

Fig.4.2: Pin diagram of IC NE555

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The NE555 IC is a highly stable controller capable of producing accurate timing pulses. With a

monostable operation, the time delay is controlled by one external resistor and one capacitor.

With an astable operation, the frequency and duty cycle are accurately controlled by two external

resistors and one capacitor.

4.1.3.2 Pin Details of NE555

1. Ground, is the input pin of the source of the negative DC voltage

2. Trigger, negative input from the lower comparators (comparator B) that maintain oscillation

capacitor voltage in the lowest 1 / 3 Vcc and set RS flip-flop

3. Output, the output pin of the IC 555.

4. Reset, the pin that serves to reset the latch inside the IC to be influential to reset the IC work.

This pin is connected to a PNP-type transistor gate, so the transistor will be active if given a

logic low. Normally this pin is connected directly to Vcc to prevent reset

5. Control voltage, this pin serves to regulate the stability of the reference voltage negative input

(comparator A). This pin can be left hanging, but to ensure the stability of the reference

comparator A, usually associated with a capacitor of about 10nF to berorde pin ground

6. Threshold, this pin is connected to the positive input (comparator A) which will reset the RS

flip-flop when the voltage on the capacitor from exceeding 2 / 3 Vcc.

7. Discharge, this pin is connected to an open collector transistor Q1 is connected to ground

emitter. Switching transistor serves to clamp the corresponding node to ground on the timing of

certain

8. VCC, pin it to receive a DC voltage supply. Usually will work optimally if given a 5-15V. The

current supply can be seen in the datasheet, which is about 10-15mA.

4.1.3.3 Modes of NE555

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, bouncefree switches, touch switches, frequency divider,

capacitance measurement, pulse-width modulation (PWM) and so on.

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. The 555 can be used as a simple ADC, converting an analog value to a

pulse length. E.g. 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

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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.

Monostable

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 (resistance) and C is in farads (capacitance).

Fig.4.3:Astable operation of NE555

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

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

4.1.3.4 Features

High Current Drive Capability (200mA)

Adjustable Duty Cycle

Temperature Stability of 0.005%/C

Timing from Sec to Hours

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Turn off Time Less than 2Sec

4.1.3.5 Applications

Precision Timing

Pulse Generation

Time Delay Generation

Sequential Timing

4.1.4 Bipolar Junction Transistor (BC548)

Fig4.4: Symbol of BJT

Fig.4.5: BC548 transistor

The bipolar junction transistor (BJT) was the first type of transistor to be mass-produced. Bipolar

transistors are so named because they conduct by using both majority and minority carriers. The

three terminals of the BJT are named emitter, base, and collector. The BJT consists of two p-n

junctions: the baseemitter junction and the basecollector junction, separated by a thin region of

semiconductor known as the base region (two junction diodes wired together without sharing an

intervening semiconducting region will not make a transistor). "The [BJT] is useful in amplifiers

because the currents at the emitter and collector are controllable by the relatively small base

current."[14] In an NPN transistor operating in the active region, the emitter-base junction is

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forward biased (electrons and holes recombine at the junction), and electrons are injected into the

base region. Because the base is narrow, most of these electrons will diffuse into the reverse-

biased (electrons and holes are formed at, and move away from the junction) base-collector

junction and be swept into the collector; perhaps one-hundredth of the electrons will recombine

in the base, which is the dominant mechanism in the base current. By controlling the number of

electrons that can leave the base, the number of electrons entering the collector can be controlled.

Collector current is approximately (common-emitter current gain) times the base current. It is

typically greater than 100 for small-signal transistors but can be smaller in transistors designed

for high-power applications.

Unlike the FET, the BJT is a lowinput-impedance device. Also, as the baseemitter voltage

(Vbe) is increased the baseemitter current and hence the collectoremitter current (Ice) increase

exponentially according to the Shockley diode model and the Ebers-Moll model. Because of this

exponential relationship, the BJT has a higher trans-conductance than the FET.

Bipolar transistors can be made to conduct by exposure to light, since absorption of photons in

the base region generates a photocurrent that acts as a base current; the collector current is

approximately times the photocurrent. Devices designed for this purpose have a transparent

window in the package and are called phototransistors.

4.1.4.1 Usage

The bipolar junction transistor, or BJT, was the most commonly used transistor in the 1960s and

70s. Even after MOSFETs became widely available, the BJT remained the transistor of choice

for many analog circuits such as simple amplifiers because of their greater linearity and ease of

manufacture. Desirable properties of MOSFETs, such as their utility in low-power devices,

usually in the CMOS configuration, allowed them to capture nearly all market share for digital

circuits; more recently MOSFETs have captured most analog and power applications as well,

including modern clocked analog circuits, voltage regulators, amplifiers, power transmitters,

motor drivers, etc.

4.1.4.2 Advantages

The key advantages that have allowed transistors to replace their vacuum tube predecessors in

most applications are

Small size and minimal weight, allowing the development of miniaturized electronic devices.

Highly automated manufacturing processes, resulting in low per-unit cost.

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Lower possible operating voltages, making transistors suitable for small, battery-powered

applications.

No warm-up period for cathode heaters required after power application.

Lower power dissipation and generally greater energy efficiency.

Higher reliability and greater physical ruggedness.

Extremely long life. Some transistorized devices have been in service for more than 30 years.

Complementary devices available, facilitating the design of complementary-symmetry circuits,

something not possible with vacuum tubes.

Insensitivity to mechanical shock and vibration, thus avoiding the problem of micro phonics in

audio applications.

4.1.4.3 Limitations

Silicon transistors do not operate at voltages higher than about 1,000 volts (SiC devices can be

operated as high as 3,000 volts). In contrast, electron tubes have been developed that can be

operated at tens of thousands of volts.

High power, high frequency operation, such as used in over-the-air television broadcasting, is

better achieved in electron tubes due to improved electron mobility in a vacuum.

On average, a higher degree of amplification linearity can be achieved in electron tubes as

compared to equivalent solid state devices, a characteristic that may be important in high fidelity

audio reproduction.

Silicon transistors are much more sensitive than electron tubes to an electromagnetic pulse, such

as generated by an atmospheric nuclear explosion.

4.1.5 Volage Regulator (7812)

Voltage regulators comprise a class of widely used IC. Regulator IC units contain the circuitry

for reference source, comparator amplifier, control device, and overload protection all in a single

IC. Although the internal construction of the IC is somewhat different from that described for

discrete voltage regulator circuits, the external operation is much the same. IC unit provides

regulation of either a fixed positive voltage, a fixed negative voltage, or an adjustable set voltage.

A power supply can be built using a transformer connected to the ac supply line to step the ac

voltage to desired amplitude, then rectifying that ac voltage, filtering with a capacitor and RC

filter, if desired, and finally regulating the dc voltage using an IC regulator. The regulators can

be selected for operation with load currents from hundreds of mili ampere to tens of amperes,

corresponding to power ratings from mill watts to tens of watts.

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The KA78XX/KA78XXA series of three-terminal positive regulator are available in the

TO220/D-PAK package and with several fixed output voltages, making them useful in a wide

range of applications. Each type employs internal current limiting, thermal shut down and safe

operating area protection, making it essentially indestructible. If adequate heat sinking is

provided, they can deliver over 1A output current. Although designed primarily as fixed voltage

regulators, these devices can be used with external components to obtain adjustable voltages and

currents.

Fig.4.6: Voltage regulator

4.1.6 Transformer

Fig 4.7: Step-down transformer

A transformer is a device that transfers electrical energy from one circuit to another through

inductively coupled electrical conductors. A changing current in the first circuit (the primary)

creates a changing magnetic field; in turn, this magnetic field induces a changing voltage in the

second circuit (the secondary). By adding a load to the secondary circuit, one can make current

flow in the transformer, thus transferring energy from one circuit to the other. It is the

phenomenon of mutual induction.

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The secondary induced voltage VS, of an ideal transformer, is scaled from the primary VP by a

factor equal to the ratio of the number of turns of wire in their respective windings:

Transformers are of two types:

1. Step up transformer

2. Step down transformer

In power supply we use step down transformer. We apply 220V AC on the primary of step down

transformer. This transformer steps down this voltage to 12V AC.

4.1.7 Diodes (1N4007)

The 1N4001 series (or 1N4000 series) is a family of popular 1.0 A (ampere) general purpose

silicon rectifier diodes commonly used in AC adapters for common household appliances.

Blocking voltage varies from 50 to 1000 volts. This diode is made in an axial-lead DO-41 plastic

package.

The 1N5400 series is a similarly popular series for higher current applications, up to 3 A. These

diodes come in the larger DO-201 axial package.

These are fairly low-speed rectifier diodes, being inefficient for square waves of more than 15

kHz. The series was second sourced by many manufacturers. The 1N4000 series were in the

Motorola Silicon Rectifier Handbook in 1966, as replacements for 1N2609 through 1N2617. The

1N5400 series were announced in Electrical Design News in 1968, along with the now lesser

known 1.5 A 1N5391 series. These devices are widely used and recommended.

Fig.4.8: Diode (1n4007)

4.1.8 Light-Emitting Diode (LED)

A light-emitting diode (LED) is an electronic light source. LEDs are used as indicator lamps in

many kinds of electronics and increasingly for lighting. LEDs work by the effect of

electroluminescence, discovered by accident in 1907. The LED was introduced as a practical

electronic component in 1962. All early devices emitted low-intensity red light, but modern

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LEDs are available across the visible, ultraviolet and infra-red wavelengths, with very high

brightness.

LEDs are based on the semiconductor diode. When the diode is forward biased (switched on),

electrons are able to recombine with holes and energy is released in the form of light. This effect

is called electroluminescence and the color of the light is determined by the energy gap of the

semiconductor. The LED is usually small in area (less than 1 mm2) with integrated optical

components to shape its radiation pattern and assist in reflection.

LEDs present many advantages over traditional light sources including lower energy

consumption, longer lifetime, improved robustness, smaller size and faster switching. However,

they are relatively expensive and require more precise current and heat management than

traditional light sources.

Fig.4.9: Internal structure of a LED

Applications of LEDs are diverse. They are used as low-energy indicators but also for

replacements for traditional light sources in general lighting, automotive lighting and traffic

signals. The compact size of LEDs has allowed new text and video displays and sensors to be

developed, while their high switching rates are useful in communications technology.

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Fig.4.10: Various Types of LEDs

4.1.9 Piezo Buzzer

Piezoelectricity is the ability of some materials (notably crystals and certain ceramics, including

bone) to generate an electric field or electric potential in response to applied mechanical stress.

The effect is closely related to a change of polarization density within the material's volume. If

the material is not short-circuited, the applied stress induces a voltage across the material. The

word is derived from the Greek piezo or piezein, which means to squeeze or press.

It most commonly consists of a number of switches or sensors connected to a control unit that

determines if and which button was pushed or a preset time has lapsed, and usually illuminates a

light on the appropriate button or control panel, and sounds a warning in the form of a

continuous or intermittent buzzing or beeping sound.

Initially this device was based on an electromechanical system which was identical to an electric

bell without the metal gong (which makes the ringing noise). Often these units were anchored to

a wall or ceiling and used the ceiling or wall as a sounding board. Another implementation with

some AC-connected devices was to implement a circuit to make the AC current into a noise loud

enough to drive a loudspeaker and hook this circuit up to an 8-ohm speaker. Nowadays, it is

more popular to use a ceramic-based piezoelectric sounder which makes a high-pitched tone.

Usually these were hooked up to "driver" circuits which varied the pitch of the sound or pulsed

the sound on and off. In game shows it is also known as a "lockout system" because when one

person signals ("buzzes in"), all others are locked out from signaling. Several game shows have

large buzzer buttons which are identified as "plungers".

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Fig.4.11: Various types of buzzers

4.1.10 Switch

In electronics, a switch is an electrical component that can break an electrical circuit, interrupting

the current or diverting it from one conductor to another. The most familiar form of switch is a

manually operated electromechanical device with one or more sets of electrical contacts. Each

set of contacts can be in one of two states: either closed meaning the contacts are touching and

electricity can flow between them, or open, meaning the contacts are separated and non-

conducting.

Fig.4.12: Push-button switches

4.1.11 Resistors

A resistor is a two-terminal electronic component that produces a voltage across its terminals that

is proportional to the electric current through it in accordance with Ohm's law:

V=IR

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4.1.11.1 Units

The ohm (symbol: ) . Commonly used multiples and submultiples in electrical and electronic

usage are the milliohm (1x10-3), kilohm (1x103), and megohm (1x106).

Fig.4.13: Resistors

Resistors are elements of electrical networks and electronic circuits and are ubiquitous in most

electronic equipment. Practical resistors can be made of various compounds and films, as well as

resistance wire (wire made of a high-resistivity alloy, such as nickel/chrome).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. Less

well-known is critical resistance, the value below 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; it's determined by

design. Resistors can be integrated into hybrid and printed circuits, as well as integrated circuits.

Size, and position of leads (or terminals) are relevant to equipment designers; resistors must be

physically large enough not to overheat when dissipating their power.

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Fig.4.14: Resistor color codes

4.1.12 Capacitors

A capacitor or condenser is a passive electronic component consisting of a pair of conductors

separated by a dielectric. When a voltage potential difference exists between the conductors, an

electric field is present in the dielectric. This field stores energy and produces a mechanical force

between the plates. The effect is greatest between wide, flat, parallel, narrowly separated

conductors.

An ideal capacitor is characterized by a single constant value, capacitance, which is measured in

farads. This is the ratio of the electric charge on each conductor to the potential difference

between them. In practice, the dielectric between the plates passes a small amount of leakage

current. The conductors and leads introduce an equivalent series resistance and the dielectric has

an electric field strength limit resulting in a breakdown voltage.

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.

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Fig.4.15: Capacitor symbols

4.1.12.1Ceramic Capacitors

In electronics ceramic capacitor is a capacitor constructed of alternating layers of metal and

ceramic, with the ceramic material acting as the dielectric. The temperature coefficient depends

on whether the dielectric is Class 1 or Class 2. A ceramic capacitor (especially the class 2) often

has high dissipation factor, high frequency coefficient of dissipation.

Fig.4.16: Ceramic capacitors

A ceramic capacitor is a two-terminal, non-polar device. The classical ceramic capacitor is the

"disc capacitor". This device pre-dates the transistor and was used extensively in vacuum-tube

equipment (e.g., radio receivers) from about 1930 through the 1950s, and in discrete transistor

equipment from the 1950s through the 1980s. As of 2007, ceramic disc capacitors are in

widespread use in electronic equipment, providing high capacity & small size at low price

compared to other low value capacitor types.

Ceramic capacitors come in various shapes and styles, including:

disc, resin coated, with through-hole leads

multilayer rectangular block, surface mount

bare leadless disc, sits in a slot in the PCB and is soldered in place, used for UHF

applications

http://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Capacitorhttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Ceramichttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Temperature_coefficienthttp://en.wikipedia.org/wiki/EIA_Class_1_dielectrichttp://en.wikipedia.org/wiki/EIA_Class_2_dielectrichttp://en.wikipedia.org/wiki/Dissipation_factorhttp://en.wikipedia.org/wiki/Through-hole_technologyhttp://en.wikipedia.org/wiki/Surface-mount_technology

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4.1.12.2 Electrolytic Capacitors

Fig.4.17: Axial lead (top) and radial lead (bottom) electrolytic capacitors

An electrolytic capacitor is a type of capacitor that uses an ionic conducting liquid as one of its

plates with a larger capacitance per unit volume than other types. They are valuable in relatively

high-current and low-frequency electrical circuits. This is especially the case in power-supply

filters, where they store charge needed to moderate output voltage and current fluctuations in

rectifier output. They are also widely used as coupling capacitors in circuits where AC should be

conducted but DC should not.

Fig.4.18: Various applications of capacitor

http://en.wikipedia.org/wiki/File:Capacitors_electrolytic.jpghttp://en.wikipedia.org/wiki/Capacitorhttp://en.wikipedia.org/wiki/Electrical_networkhttp://en.wikipedia.org/wiki/Rectifierhttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Direct_current

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4.1.13 Printed Circuit Board (PCB)

Fig.4.19: PCB Boards

In electronics, printed circuit boards, or PCBs are used to mechanically connect electronic

components using conductive path ways, or traces etched from copper sheets. After populating

the board with electronic components, a printed circuit assembly (PCA) is formed. PCBs are

rugged, inexpensive, and can be highly reliable. They require much more layouteffort and higher

initial cost than either wire-wrapped or point-to-point constructed circuits, but are much faster

and consistent in high volume production.

4.1.13.1 Manufacturing Process

4.1.13.1.1 Patterning (Etching)

The vast majority of printed circuit board are made by adhering a layer of copper over the

entire substrate, some time on both side, (creating a blank PCB ) then removing unwanted

copper after applying a temporary mask (e.g. a chemical etching), leaving only a desired copper

traces to the bare substrate (or a substrate with a very thin layer of copper) usually by a complex

process of multiple electroplating steps.

4.1.13.1.2 PCB Milling

PCB milling uses a 2 or 3 mechanical milling systems to mill away the copper foil from the

substrate. A PCB milling machine (referred to as a PCB 38prototype) operates in a similar way

to a plotter, receiving command from the host software that control the position of the milling

head of the x, y, and z axis. Additive process also exists. The most common is the semi-

additive process. In this version, the unpattern board has a thin layer of copper already on it. A

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reverse mask is then applied. Additional copper is then plated on to the board in the unmask

region, copper may be plated to any desired weight. Tin-lead or other surface plating is then

applied. The mask is stripped away and a brief etching step remove the unexposed original

copper laminated from the board, isolating the individual traces.

4.1.13.1.3 Drilling

Holes, or vias, through a PCB are typically drilled with tiny drill bits made of solid tungsten

carbide. The drilling is performed by automated drilling machines with placement controlled by

a drill tape or drill file. This computer generated files are also called numerically controlled drill

(NCD) files or Excellon files. The drill file describes the location and sizes of each drill hole.

When very small vias are required, drilling with mechanical bits is costly because of high rates

of wear and breakage. In this case, the vias may be evaporated by laser. Laser-drill vias typically

have an inferior surface finish inside the hole. These holes are called micro vias.

4.1.13.1.4 Solder Plating and Solder Resist

The pads and land to which component will be mounted are typically plated, because the bare

copper is not readily solder able. Traditionally, any exposed copper was plated with solder. This

solder was traditionally a tirn-lead alloy, however new solder compounds are now used to

achieve compliance with the RoHS directive in the ErU, which restricts the use of lead. Edge

connectors, made on the side of some boards, are often gold plated. Gold plating is also

sometimes applied on the whole boards.

4.1.13.1.5 Silk Screen

Line art and text may be printed onto the outer surface of a by silk screening. When space

permits, the silk screen text can indicate component designators, switch setting requirements, test

points, and other features useful in assembling, testing and servicing the circuit board.

4.1.13.1.6 Populating

After the PCB is completed, electronic component must be attached to form a functional printed

circuit assembly. In through-hole construction, component leads may be inserted in holes and

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electrically and mechanically fixed to the board with a molten metal solder, while in surface

mount construction, the component are simply soldered to pads or lands on the other surface of

PCB.

4.1.13.1.7 Protection and Packaging

PCBs intended for extreme environment often have a conformal coat, which is applied by

dipping or spraying after the component have been soldered. The coat prevents corrosion and

leakage currents or shorting due to condensation. The earliest conformal coats were wax.

Modern conformal coats are usually dips of dilute solution of silicon rubber, polyurethane,

acrylic, or epoxy. Some are engineering plastics sputter onto the PCB in a vacuum chamber.

Mass-production PCBs have small pads for automated test equipment to make temporary

connections. Sometimes the pads must be isolated with resistor.

Fig.4.20: A developed PCB

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5.1 Result

In this project we used CA3130, IC NE 555 Timer, bridge rectifier, LED, piezo buzzer, resistor,

capacitor, etc.

The whole circuit and the system are shown in the picture below:

5.1.1Hardware Testing

Fig.5.1: Component testing on bread-board

In this picture, we have used a 9V battery instead of the transformer and the rectifier circuit,

which gave the appropriate result.

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Fig.5.2: The whole circuit setup of mobile detector.

5.1.2 Hardware Implementation on PCB

This project is then finally implemented on the PCB (printed circuit board).

Fig 5.3 Implementation of the circuit on PCB

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Fig.5.4: A working mobile phone detector circuit

In this image, the working mobile phone detector is displayed. The power is switched ON via

step-down transformer through the bridge rectifier, then to voltage regulator. The regulated

12V DC supply is indicated by the green LED. The electromagnetic signals from mobile

phone is intercepted by the antenna and the capacitors, and this is indicated by the red

LED.

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6.1 Conclusion

In this project, we made an attempt to design a MOBILE DETECTOR that can detect both the

incoming and outgoing calls, SMS and internet usage (like video transmission) even if the

mobile is kept at the silent mode. Our circuit has detected the presence of an activated mobile

even at a distance of about one and a half meters. It gave the indication of the presence of mobile

by glowing the LED, according to the receiving frequency and by buzzing the sound of the

buzzer. The alarm continues until the signal ceases. But the problems for this design is that it can

only sense the frequency of the mobile phones, it cannot detect how many of mobile phones been

used. However, by detecting the presence of the mobile phones, it can alert to user to silent or

switch off their mobile phones from those particular areas.

By designing this project, it can be used to help the management system for preventing the

usage of mobile phones in prohibited areas. This design can help to prevent the noise interruption

and maintain the peace environment to the other people in those areas.

6.2Future Scope

This project has been developed and implemented. However, it can be improved to target more

advanced and better application in the next stage of research. For future improvement, there are

several suggestions stated below:

1. Another sensor design can be develop to detect how many phones available in that particular

zone / area

2. Increase the range of the detection area (range can be wider)

3. Develop automatic system:

a) Single way transmission - host will give message to receiver

b) 2 ways transmission and receive - host need to know the mobile status

c) 2 ways transmission and receive + automatic with phone preset

d) 2 ways + automatic switch mode (2 ways)

e) Automatic switch to silent in silent mode zone

f) Away silent zone, switch back to previous/ general

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REFERENCES

1. Mandeep Singh, Kamaljeet singh, Dr. Neena Gupta, Design and Implementation of Cell-

phone Detection Based Line Follower Robot, Department of electronics and communication

engineering, ISSN-2277-1956.

2. K. Mohan Dece, Novel Mobile Detector Sensing, Alarming and Reporting System, SRM

University, ARPN journal of science and technology, ISSN-2225-7217, VOL-2 no, 1 January

2012.

3. Christian C. Mbaocha, Design and Implementation of Intelligent Mobile phone Detector,

Department of electrical/electronic engineering, Nigeria, ISSN-L: 2233-9553 VOL-3 no.1, July

2012.

4. Gary Fernandes, OP-AMP Cellphone RF Signal Detector, revised on 2012, online circuit

lab.

5. Amit Mishra, Techniques to abolish the effect of sniffer existing in the network,

International Journal of Computer Information System.

6. Mohan Kumar, Mobile Bug, in 2008, Electronics for You.

7. Abdul K A, Asad Nalm, Ayman Samier (2008), Mobile Phone International Jamming

System.

WEBSITES.

www.google.com,

www.wikipedia.org,.

www.pdfmachine.com,

www.efymag.com,

www.datasheets.com,

www.slideshare.com,

www.ijecse.org

.

http://www.google.com,/http://www.wikipedia.org,/http://www.pdfmachine.com,/http://www.efymag.com,/http://www.datasheets.com,/http://www.slideshare.com,/http://www.ijecse.org/

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