mobile detector (thesis)
DESCRIPTION
a simple mobile detector using a fixed power supply (bridge wave rectifier+step-down transformer).TRANSCRIPT
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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
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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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