AProject Reportat

CELL PHONE DETECTORSubmitted by:Name (Roll no.)

Aadil Amaan (0905330001)

Mahesh Kumar Sahu (0905330040)

Pranay Ranjan Maurya (0905330056)

Puneet Kumar Gupta

(0905330060)

AZAD INSTITUTE OF ENGINEERING & TECHNOLOGY, LUCKNOW(Affiliated to Gautam Buddha Technical University, Lucknow)

Department of Electronics Engineering

Session (2012-2013)

ACKNOWLEDGEMENT

Our sincerest appreciation must be extended by our faculties. We also want to thank faculties of the College. They have been very kind and helpful to us. We want to thank all teaching and nonteaching staff to support us. Especially we are thankful to Mr. S. K. Mishra (HOD) for providing this golden opportunity to work on this project, inspiration during the course of this project and to complete the project within stipulated time duration and four walls of College Lab. We would like to express our sincere gratitude to our Guide Ms. Sonal Mam for their help during the course of the project right from selection of the project, their constant encouragement, expert academic and practical guidance.

ABSTRACT

This handy, pocket-size mobile transmission detector or sniffer can sense the presence of an activated mobile cell phone from a distance of one and-a-half meters. So it can be used to prevent use of mobile phones in examination halls, confidential rooms, etc. It is also useful for detecting the use of mobile phone for Spying and unauthorized video transmission. The circuit can detect the incoming and outgoing calls, SMS and video transmission even if the mobile phone is kept in the silent mode. The moment the Bug detects RF transmission signal from an activated mobile phone, it starts sounding a beep alarm and the LED blinks. The alarm continues until the signal transmission ceases. Assemble the circuit on a general purpose PCB as compact as possible and enclose in a small box like junk mobile case. As mentioned earlier, capacitor C3 should have a lead length of 18 mm with lead spacing of 8 mm. Carefully solder the capacitor in standing position with equal spacing of the leads. The response can be optimized by trimming the lead length of C3 for the desired frequency. You may use a short telescopic type antenna.Use the miniature 12V battery of a remote control and a small buzzer to make the gadget pocket-size. The unit will give the warning indication if someone uses Mobile phone within a radius of 1.5 meters.

CONTENTS PAGE NO. CHAPTER ONE1.1 Introduction (5) 1.2 Cellular Phone Technology (7)1.2.1 Cellular Phone Features

(7)1.2.2 Cellular Phone Communication Standards

(8)1.3 Overview of Cell Phone Detector

(9)1.3.1 Mobile Bug

(11)1.4 Circuit Diagram (12)1.5 Description of Circuit Diagram (13)

CHAPTER TWO2.1 Introduction (14)2.2 Block Diagram (18)2.3 Block Diagram Explanation (18)2.3.1 Transmission Lines (19)2.4 PCB Layout (20)2.5 PCB Fabrication (20)2.5.1 The Printed Circuit Board (21)2.5.2 Copper-clad Laminates (21)2.5.3 Board Cleaning Before Pattern Transfer (22)2.5.4 Screen Printing (22)2.5.5 Etching (22)2.5.6 Chemistry (22)2.5.7 Drilling (23)2.5.8 Component Mounting (24)2.5.9 Soldering (24)2.5.10 Soldering Steps (25)CHAPTER THREE3.1 Introduction (26)3.2 List of Components (30)3.3 Components Description (31)3.3.1 Resistor (31)3.3.2 Capacitor (34)3.3.3 Transistor (38)3.3.4 LED (45)3.3.5 Piezo Buzzer (57)3.4 Pin Diagram of ICs (62)3.4.1 IC CA3130 (62)3.4.2 IC NE555 (63)3.5 Working, Applications, and Features of IC CA3130 (63)3.6 Working, Applications, and Features of IC NE555 (66)CHAPTER FOUR4.1 Introduction (71)4.2 Circuit Testing on Breadboard (72)4.3 Working of Cell Phone Detector (73)4.3.1 Purpose of the circuit (73)4.3.2 Concept (73)4.3.3 How the circuit works? (73)4.3.4 Uses of the capacitor (74)

4.3.5 How the capacitor senses the RF? (74)CHAPTER FIVE5.1 Introduction (75)5.2 Applications (76)5.3 Advantages (77)

5.3 Limitations (78)5.4 Future Scope (78)5.5 References (79)CHAPTER ONE

1.1 INTRODUCTION:

In this chapter we will discuss the overview of Cell Phone Detector and see its demo circuits. We will also discuss about circuit diagram and description of the circuit diagram. But before we discuss the above we have to know about the previous detection techniques which has been introduced already in the market.The first signal detection technique, an existing design utilizing discrete component is difficult to implement. They are very affordable to construct, but require precision tuning. This design is analyzed and found to be inaccurate.

The second signal detection technique, a design using a down converter, voltage controlled oscillator (VCO), and a bandpass filter was investigated for cellular phone detection. The performance of this technique through hardware and computer modeling is discussed and the results are presented. The new system is accurate and a practical solution for detecting cellular phone in a secure facility.Amobile phone(also known as acellular phone,cell phone, and ahand phone) is a device that can make and receivetelephone callsover a radio linkwhile moving around a wide geographic area. It does so by connecting to acellular networkprovided by amobile phone operator, allowing access to thepublic telephone network. By contrast, acordless telephoneis used only within the short range of a single, private base station.

In addition to telephony, modern mobile phones also support a wide variety of otherservicessuch astext messaging,MMS,email, Internet access, short-range wireless communications (infrared,Bluetooth), business applications, gaming and photography. Mobile phones that offer these and more general computing capabilities are referred to assmart phones.

Acellular networkormobile networkis aradionetwork distributed over land areas called cells, each served by at least one fixed-location transceiver known as acell siteorbase station. In a cellular network, each cell uses a different set of frequencies from neighboring cells, to avoid interference and provide guaranteed bandwidth within each cell.

When joined together these cells provide radio coverage over a wide geographic area. This enables a large number of portable transceivers (e.g.,mobile phones,pagers, etc.) to communicate with each other and with fixed transceivers and telephones anywhere in the network, via base stations, even if some of the transceivers are moving through more than one cell during transmission.In acellular radiosystem, a land area to be supplied with radio service is divided into regular shaped cells, which can be hexagonal, square, circular or some other regular shapes, although hexagonal cells are conventional. Each of these cells is assigned multiple frequencies (f1f6) which have correspondingradio base stations. The group of frequencies can be reused in other cells, provided that the same frequencies are not reused in adjacent neighboring cells as that would causeco-channel interference.

The increasedcapacityin a cellular network, compared with a network with a single transmitter, comes from the fact that the same radio frequency can be reused in a different area for a completely different transmission. If there is a single plain transmitter, only one transmission can be used on any given frequency. Unfortunately, there is inevitably some level ofinterferencefrom the signal from the other cells which use the same frequency. This means that, in a standard FDMA system, there must be at least a one cell gap between cells which reuse the same frequency.

In the simple case of the taxi company, each radio had a manually operated channel selector knob to tune to different frequencies. As the drivers moved around, they would change from channel to channel. The drivers knew whichfrequency covered approximately what area. When they did not receive a signal from the transmitter, they would try other channels until they found one that worked. The taxi drivers would only speak one at a time, when invited by the base station operator (this is, in a sense,time division multiple access(TDMA).Practically every cellular system has some kind of broadcast mechanism. This can be used directly for distributing information to multiple mobiles, commonly, for example inmobile telephonysystems, the most important use of broadcast information is to set up channels for one to one communication between the mobile transceiver and the base station. This is calledpaging. The three different paging procedures generally adopted are sequential, parallel and selective paging.

The details of the process of paging vary somewhat from network to network, but normally we know a limited number of cells where the phone is located (this group of cells is called a Location Area in theGSMorUMTSsystem, or Routing Area if a data packet session is involved; inLTE, cells are grouped into Tracking Areas). Paging takes place by sending the broadcast message to all of those cells. Paging messages can be used for information transfer. This happens inpagers, in CDMAsystems for sendingSMSmessages, and in theUMTSsystem where it allows for low downlink latency in packet-based connections.

In a cellular system, as the distributed mobile transceivers move from cell to cell during an ongoing continuous communication, switching from one cell frequency to a different cell frequency is done electronically without interruption and without a base station operator or manual switching. This is called thehandoveror handoff. Typically, a new channel is automatically selected for the mobile unit on the new base station which will serve it. The mobile unit then automatically switches from the current channel to the new channel and communication continues.1.2 CELLULAR PHONE TECHNOLOGY:

Cellular Phone Technology is rapidly changing. Features like Bluetooth, USB, high resolution cameras, microphones, Internet, 802.11 wireless, and memory cards added every year.Also, the communication technology a cellular phone uses such as CDMA, GSM, 3G and 4G are rapidly changing.

1.2.1 CELLULAR PHONE FEATURES:

Bluetooth is a secure wireless protocol that operates at 2.4GHz. The protocol uses a master slave structure and is very similar to having a wireless USB port on your cellular phone. Device like a printer, keyboard, mouse, audio device, and storage device can be connected wirelessly. This feature is only use for hands-free devices but can also be used for file transfer of picture, music, and other data.

Universal Serial Bus (USB) is a way for cellular phone to connect to a computer for data transfer. This feature is very similar to Bluetooth for cellular phone with the exception of using a cable. On todays cellular phones this feature is mainly used for charging the battery or programming by the manufacturer. It can also be used to transfer picture, music, and other data. Cameras on cellular phones are a very popular feature that was added in the last 10 years. In recent years, high resolution cameras have become a standard feature. Most cellular phones will come with at least a 2 mega pixel camera and the more expensive phones can be as much as 8 mega pixels.Microphones have been featured on cellular phone since they first came out. In the last 10 years the microphones have become dual purpose; now there are programs on the phone that record voice to file such a simple voice recorder or as part of a video.

Some cellular phones come with 802.11 wireless built in and allows the phone to connect to any nearby wireless network. This provides an alternate connection method to the Internet and saves money if you are on a limited data plan. Also, connecting with 802.11 is most likely going to provide better throughput than using the cellular phone network.All these features make cellular phone today very versatile. They can connect with almost any storage medium or computer. In the years to come, cellular phones will continue to gain more and more features.

1.2.2 CELLULAR PHONE COMMUNICATION STANDARDS:

Currently the three main technologies used by cellular phone providers are 2G, 3G, and 4G. Each generation of technology uses a different transmission protocol. The transmission protocols dictate how a cellular phone communicates with the tower. Some examples are: frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), Global System for Mobile Communication (GSM), CDMA2000, wide-band code division multiple access (WCDMA), and time division synchronous code division multiple access (TD-SCDMA). All of these protocols typically operates in the 824-894 MHz band in the United States. Some protocols such as GSM (depending on the provider) will use the 1800-2000 MHz band.1.3 OVERVIEW OF CELL PHONE DETECTOR:

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

Figure: 1.1IC1 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 output go high and LED lights for a short period. This is because + input gets more voltage than the input. After a few seconds, output goes low because the output current passes to the input through R2. Meanwhile, capacitor C1 also charges. So that both the inputs gets almost equal voltage and the output remains low. 0.22 capacitor (no other capacitor can be substituted) remains fully charged in the standby state.

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.The circuit can detect both the incoming and outgoing calls, SMS and video transmission even if the mobile phone is kept in the silent mode. The moment the bug detects RF transmission signal from an activated mobile phone, it starts sounding a beep alarm and the LED blinks. The alarm continues until the signal transmission ceases. 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 required for a mobile bug.Here the circuit uses a 0.22F 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 8) and null inputs (pin 1) of IC1 for phase compensation and gain control to optimise the frequency response.

When the mobile phone signal is detected by C3, the output of IC1 becomes high and low alternately according to the frequency of the signal as indicated by LED1. This triggers mono stable timer IC2 through capacitor C7. Capacitor C6 maintains the base bias of transistor T1 for fast switching action. The low-value timing components R6 and C9 produce very short time delay to avoid audio nuisance.Assemble the circuit on PCB and enclose in a small box like junk mobile case. As mentioned earlier, capacitor C3 should have a lead length of 18 mm with lead spacing of 8 mm. Carefully solder the capacitor in standing position with equal spacing of the leads. The response can be optimised by trimming the lead length of C3 for the desired frequency. You may use a short telescopic type antenna.1.3.1 Mobile Bug: 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.1.4 CIRCUIT DIAGRAM: Figure 1.2: Circuit Diagram of Cell Phone Detector1.5 CIRCUIT DIAGRAM DESCRIPTION:

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 cell phone detector. Here the circuit uses a 0.22pF 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 for phase compensation and gain control to optimise the frequency response.When the mobile phone signal is detected by C3, the output of IC1 becomes high and low alternately according to the frequency of the signal as indicated by LED1. This triggers monostable timer IC2 through capacitor C7. Capacitor C6 maintains the base bias of transistor T1 for fast switching action. The low-value timing components R6 and C9 produce very short time delay to avoid audio nuisance.CHAPTER TWO

2.1 INTRODUCTION:

In this chapter we will discuss about the block diagram of the cell phone detector and also the description of it, PCB layout and PCB fabrication also included in this chapter to explain the description of cell detector thoroughly in a suitable manner. But before this we have to see the main aspects about this which performs an important role. Using a down converter, voltage controlled oscillator (VCO), and a bandpass filter in the second technique explored for cellular phone detection. Two signals inputted in the down converter. The first signal is from the antenna and is between 829-835 MHz depending on the cellular phone (832 MHz for this experiment). The signal is from the VCO, which is tuned to 800 MHz band. The down converter multiplies the two signals together producing the sum and the difference. This is then filtered by a bandpass filter with the passband lower and upper edges respectively at 28 MHz and 36 MHz band. Filtering eliminates the sum of the signals and any environmental noise. Now all the remains is the difference, a 29-35 MHz signal that indicates an active cellular phone is in the area. This can easily be converted using analog to digital converters and output to an alarm or a computer. Let us see the PCB layout introduction it will help us in this chapter.Schematic driven layoutis the concept inIC LayoutorPCBlayout where theEDA softwarelinks the schematic and layout databases. It was one of the first big steps forward in layout software from the days when editing tools were simply handling drawn polygons.

Schematic driven layout allows for several features that make the layout designer's job easier and faster. One of the most important is that changes to the circuit schematic are easily translated to the layout. Another is that the connections between components in the schematic are graphically displayed in the layout ensuring work is correct by construction.Aprinted circuit board, orPCB, is used to mechanically support and electrically connectelectronic components using components pathways. When the board has only copper tracks and features, and no circuit elements such as capacitors, resistors or active devices have been manufactured into the actual substrate of the board, it is more correctly referred to asprinted wiring board(PWB) oretched wiring board. Use of the termPWBorprinted wiring boardalthough more accurate and distinct from what would be known as a trueprinted circuit board, has generally fallen by the wayside for many people as the distinction betweencircuitandwiringhas become blurred. Today printed wiring (circuit) boards are used in virtually all but the simplest commercially produced electronic devices, and allow fully automated assembly processes that were not possible or practical in earlier era tag type circuit assembly processes.

A PCB populated with electronic components is called aprinted circuit assembly(PCA),printed circuit board assemblyorPCB Assembly (PCBA). In informal use the term "PCB" is used both for bare and assembled boards, the context clarifying the meaning.

Alternatives to PCBs includewire wrapandpoint-to-point construction. PCBs must initially be designed and laid out, but become cheaper, faster to make, and potentially more reliable forhigh-volume productionsince production and soldering of PCBs can be automated. Much of the electronics industry's PCB design, assembly, and quality control needs are set by standards published by theIPCorganization.Excluding exotic products using special materials or processes, all printed circuit boards manufactured today can be built using the following four items which are usually purchased from manufacturers:(i) Laminates(ii) Copper-clad Laminates

(iii) Resin impregnated B-stage cloth (pre-preg)

(iv) Copper foilLaminates are manufactured by curing under pressure and temperature layers of cloth or paper withthermo setresinto form an integral final piece of uniform thickness. The size can be up to 4 by 8 feet (1.2 by 2.4 m) in width and length. Varying cloth weaves (threads per inch or cm), cloth thickness, and resin percentage are used to achieve the desired final thickness anddielectriccharacteristics.

Each trace consists of a flat, narrow part of thecopperfoil that remains after etching. The resistance, determined by width and thickness, of the traces must be sufficiently low for the current the conductor will carry. Power and ground traces may need to be wider than signal traces. In a multi-layer board one entire layer may be mostly solid copper to act as aground planefor shielding and power return. Formicrowavecircuits,transmission linescan be laid out in the form ofstriplinesandmicro stripswith carefully controlled dimensions to assure a consistentimpedance.

In radio-frequency and fast switching circuits theinductanceandcapacitanceof the printed circuit board conductors become significant circuit elements, usually undesired; but they can be used as a deliberate part of the circuit design, obviating the need for additional discrete components."Multi layer" printed circuit boards have trace layers inside the board. One way to make a 4-layer PCB is to use a two-sided copper-clad laminate, etch the circuitry on both sides, then laminate to the top and bottom pre-preg and copper foil. Lamination is done by placing the stack of materials in a press and applying pressure and heat for a period of time. This results in an inseparable one piece product. It is then drilled, plated, and etched again to get traces on top and bottom layers. Finally the PCB is covered with solder mask, marking legend, and a surface finish may be applied. Multi-layer PCB's allows for much higher component density.Block Diagam:

Above diagram shows how a cellular phone detector works by using Down Converter, Bandpass Filter, and Voltage Controlled Oscillator (VCO). Now we will see how our cell phone detector works without using above devices.

2.2 BLOCK DIAGRAM OF CELL PHONE DETECTOR:

2.3 DESCRIPTION OF BLOCK DIAGRAM: There are five major blocks in the case of cell phone detector. They are

(i) Antenna

(ii) LC tuner circuit

(iii) Current to voltage converter

(iv) 555 monoshot circuit

(v) Output stage The first stage is the Antenna stage. The transmission frequency of mobile phone ranges from 0.9 to 3 GHz with a wavelength of 3.3 to 10 cm. These frequencies send by an active mobile phone need to be received. This function is carried out by the receiving antenna. An ordinary RF detector using tuned circuit is not suitable for detecting signals in the GHz frequency band used in mobile phones. So a circuit detecting GHz signal is required for a mobile detector.

Here the circuit uses 0.22F disk capacitor to capture RF signals from the mobile phones. The lead length of the capacitor is fixed as 18mm with a spacing of 08mm 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 phones. This capacitor along with the lead inductance act as a transmission lines to intercept the signals from the mobile. The capacitor creates a field, stores energy and transfers the stored energy in the form of minute current to the input of a current to voltage converter circuit. This forms the second stage which is LC Tuner stage.The current coming to the input of the converter IC, upset its balanced input and then convert the current into corresponding output voltage. When the mobile phone signals are detected by the input capacitor, the output of the converter IC, becomes high and low as indicated by the LED. This triggers the monostable circuit also. The low value timing components R and C produce very short time delay to avoid audio nuisance. A buzzer is triggered by using the output of the monoshot timer. The buzzer along with the LEDF forms the output stage that provide us the indication as sound and light respectively.2.3.1 TRANSMISSION LINE:

A transmission line conveys electromagnetic waves. A pair of parallel wires and coaxial cables is the commonly employed transmission lines. It is used to connect transmitter and antenna, receiver and antenna etc. At low frequency the energy loss in the connecting wires is negligible. But for higher frequency the loss can be reduced by using two parallel wires, one for forward connection and the other for return current. A transmission line is characterized by its lumped parameter as described below.

Series Resistance:

Due to finite conductivity of the conductors, there is a uniform distributed resistance. There is also power loss due to radiation from the lines. Thus the finite conductivity and radiation loss can be modeled as a series resistance per loop of length.

Series Inductance:

A current carrying conductor has an associated magnetic field. Both, the grow and decay of the current is opposed, and hence it possesses inductance. This inductance is distributed throughout the line. It acts in series.Series Capacitance:

The two conducting wires is separated by a distance, situated in a dielectric medium gives rise to a capacitance that acts parallel with the wires. Shunt Leakage Conductance:

Since the wires are separated by a dielectric medium that cannot be perfect in its insulation, current leaks through it when the lines carry a current. This leakage of current through the dielectric between the wires is represented by a shunt conductance per unit length.

2.4 PCB Layout of the Cell Phone Detector Circuit:

Figure: 2.3 PCB Layout

2.5 PCB Fabrication:2.5.1 The Printed Circuit Board:

Printed Circuit Boards (PCBs) are certainly the most important element in the fabrication of electronic equipment. It is the design of properly laid-out PCBs that determine many of the limiting properties with respect to noise immunity, as well as to fast-pulse, high frequency and low level characteristics of equipments. High power PCBs in their turn requires a special design strategy. The first step in the production of the printed circuit board is to obtain the layout of the PCB from the circuit diagram. For obtaining the layout computer-aided design techniques are used. In this technique the diagrams are drawn directly on a graphics work station. The software then checks for any design and layout rules error. After correction of errors, if any, the layout is obtained based on this layout the printed circuit boards are fabricated from copper-clad laminates. 2.5.2 Copper-Clad Laminates:

A laminate can be simply described as the product obtained by pressing layers of a filler material impregnated with resin under heat and pressure. The commonly used fillers are a variety of papers, or glass in various forms such as cloths and continuous filament mat. The resigns could be phenolic, epoxy, polyester, PTFE (Polytetrafluroethylene), etc. Each of this fillers and resins contributes intrinsically to the characteristic properties of the finished copper-clad laminates. It is further possible to manipulate the properties of copper clad laminates by fine variations in the manufacturing process. The large range of possible copper clad laminates has been standardized in the national and international specifications. Thus, there are exactly laid down specification for each copper-clad laminate grade, being defined by the resin/filler system and the minimum/maximum limits of the properties. A copper-clad laminate must have a good copper-to-base laminate bond strength. The appearance of copper side must be smooth and uniform. All these properties must be retained during the production of PCB and also under its working conditions. All electrical and mechanical properties of the laminates are affected by the environmental conditions such as humidity, temperature corrosive atmosphere etc. Similarly most of the electrical properties vary with changing in frequency. Thus while choosing the copper-clad laminates the various environmental conditions likely to be encountered are to be considered.2.5.3 Board Cleaning Before Pattern Transfer:

After choosing the copper-clad laminate it should be cleaned. The cleaning of the copper-clad prior to resist application is an essential step for any PCB process using etch or plating resist. Insufficient cleaning is one of the reasons most often encountered for difficulties in PCB fabrication although it might not always be immediately recognized as this. But it is quite often the reason for poor resist-adhesion, uneven photo resist-film, pinholes, poor plating-adhesion, etc. The first step in cleaning process is scrubbing with a pumice/salt solution. This removes inorganic matters like particulates and oxide and also performs degreasing up to a certain extent. The pumice used is of a very fine grade to minimize deep scratches. After scrubbing with the abrasive, a water rinse is done to remove slurry. This is followed by a strong acid dip in hydrochloric acid (10 vol %) which will residual alkali and metallic oxides and prepare the surface for maximum resist adhesion. A final rinse using de-ionized gives guarantees that no fresh contamination is brought on to the surface. The time span until the next processing step which is screen-printing is made as short as possible to minimize the formation of fresh oxides. 2.5.4 Screen Printing:

Screen-printing is the process by which the conductor pattern which is on the film master is transferred on to the copper-clad laminates. With the screen-printing process one can produce PCBs with a conductor width as low as 2.5mm and registration error of just 0.1mm on an industrial scale with a high reliability. In its basis form the screen-printing process is very simple. A screen fabric with uniform meshes and openings is stretched and fixed on a solid frame of a metal or wood. The circuit pattern is photographically transferred on to the screen, leaving the meshes in pattern area open, while meshes in the rest of area are closed. In the actual printing step, ink is forced by the moving squeegee through the open meshes on to the surface of material to be printed. The ink deposition in a magnified cross-section shows the shape of trapezoid. The ideal screen printing ink should have many features which cannot be combined. It should dry rapidly on the PCB but dry slowly on the screen. It should be highly resistant against all the chemicals but easy to be stripped. 2.5.5 Etching:

After drying of the resist of the copper-clad laminate the next process is etching. The final copper pattern is formed by selective removal of all unwanted copper, which is not protected by etch resist. For small scale PCB production ferric chloride is used as enchant because it is very simple to use.2.5.6 Chemistry: Free acid attack the copper is formed by the hydrolysis reaction

FeCl3 + 3H2O Fe(OH)3 + 3HCl .eq(2.1)The copper is oxidized by ferric ions, forming cuprous chloride (CuCl) and ferrous chloride (FeCl2)

FeCl3 + Cu FeCl2 + CuCl eq(2.2)

Cuprous chloride (CuCl) oxidizes further in the etching solution to cupric chloride (CuCl2)

FeCl3 + CuCl FeCl2 + CuCl2 ..eq(2.3)

The built up cupric chloride (CuCl2) itself reacts also with copper and forms cuprous chloride (CuCl)

CuCl2 + Cl 2CuCl .eq(2.4)After etching is over the ferric chloride, contaminated surface should be cleaned. After a simple spray water rinse, a dip in a 5% (volume) oxalic acid solution is done to remove the copper and iron salt. A vigorous final water rinse has to flow.

2.5.7 Drilling:

After the etching operation the next step is drilling of component mounting holes in the PCBs. Holes are made by drilling whenever a superior holes finish or plated-through holes process is required and where the tool costs for a punching tool cannot be justified. Therefore drilling is applied by all the professional grade PCB manufacturer and generally and in all the smaller PCB production plan and in laboratories. The importance of holes drilling into PCBs has further gone up with electronic component miniaturization and is need for smaller diameters (diameter less than half the board thickness) and higher package density where hole punching is practically ruled out. This is done using drilling machines with suitable size drill bits. To compensate for laminate resilience the drill bit diameter is chosen 0.05mm bigger than the holes diameter expected. The usual size of hole is 0.8 mm and for bigger components like preset and power devices the size is 1.2 mm. The production of holes with diameter and tolerances as specified above should not need any special attention: a suitable drilling machine with a correctly sharpened drill bit will provide these results. After drilling the required number of holes of specified dimensions the next step is mounting the components on the PCB.2.5.8 Component Mounting:

Component mounting on the PCB in such a way to minimize the cracking of solder joints due to mechanical stress on the joint. This can be ensured by bending of the axial component lead in a manner to guarantee and optimum retention of the component on the PCB while a minimum stress is introduced on the solder joint. Bending is done with care taken not to damage the component or its leads. The lead bending radius is chosen to be approximately two times the lead diameter. The bent leads should fit into the holes perpendicular to the board so that any stress on the component lead junction is minimized. The component lead bending is done using a bending tool for easy but perfect component preparation. 2.5.9 Soldering:

Soldering is the process of joining metals by using lower melting point metal or alloy with joining surface.

Solder:

Soldering is the process of joining materials. Soldered joints in electronics switches will establish strong electrical connection between components leads. The popularly used solders are alloys of tin and lead melt below the melting point of the tin.Flux:

In order to make the surface accept to make the solder readily, the component terminals should be free from oxide and other obstructing films. The leads should be cleaned chemically or by abrasion using blades or knives.

A small amount of lead coating can be done on cleaned portion of the lead using soldered iron. This process is called thinning. Zink Chloride or Ammonium Chloride separately or in combination is mostly used as fluxes. These are available in petroleum jelly as paste flux. The residue which remains after soldering may be washed out with more water accompanied by brushing.

Soldering Iron:

It is tool used to melt solder and apply at the joint in the circuit. It operates at 230v supply. The iron bit at the tip of it gets heated within few minutes. 50W or 25W soldering irons are commonly used for soldering purpose.2.5.10 Soldering Steps:

For proper soldering on PCBs the soldering steps are:

(i) Make the layout of component in the circuit. Plug in the cord of the soldering iron into the mains to get heated.

(ii) Straighten and remove the coating of components leads using a blade or knife. Apply a little flux on the leads. Take a little solder on soldering iron and apply the molten solder on the leads. Care must be taken to avoid the components to getting heated up. (iii) Mount the components on PCB by bending the leads of components using noise pliers.

(iv) Apply flux on the joints and solder the joints. Soldering must be done in minimum to avoid the dry soldering and heating up of components.

(v) Wash the residue using water and brush.

CHAPTER THREE

3.1 Introduction:

In this chapter we will see the components used in the cell phone detector and also discuss about the main aspects of their working and features. But before the discussing of above let us see about some quality of the semiconductor devices.

Semiconductor devicesareelectronic componentsthat exploit theelectronicproperties ofsemiconductor materials, principallysilicon,germanium, andgallium arsenide, as well asorganic semiconductors. Semiconductor devices have replacedthermionic devices(vacuum tubes) in most applications. They useelectronicconductionin thesolid stateas opposed to thegaseous state or thermionic emissionin a high vacuum.Semiconductor devices are manufactured both as single discrete devices and asintegrated circuits(ICs), which consist of a numberfrom a few (as low as two) to billionsof devices manufactured and interconnected on a single semiconductorsubstrate, orwafer.

Semiconductor materials are so useful because their behavior can be easily manipulated by the addition of impurities, known asdoping. Semiconductorconductivitycan be controlled by introduction of an electric or magnetic field, by exposure tolightor heat, or by mechanical deformation of adopedmono crystallinegrid; thus, semiconductors can make excellent sensors. Current conduction in asemiconductoroccurs via mobile or "free"electronsandholes, collectively known ascharge carriers. Doping a semiconductor such assiliconwith a small amount of impurity atoms, such asphosphorusorboron, greatly increases the number of free electrons or holes within the semiconductor. When a doped semiconductor contains excess holes it is called "p-type", and when it contains excess free electrons it is known as n-type, wherep(positive forholes) orn(negative forelectrons) is the sign of the charge of the majority mobile charge carriers. The semiconductor material used in devices is doped under highly controlled conditions in a fabrication facility.By far,silicon(Si) is the most widely used material in semiconductor devices. Its combination of low raw material cost, relatively simple processing, and a useful temperature range make it currently the best compromise among the various competing materials. Silicon used in semiconductor device manufacturing is currently fabricated intobowls that are large enough in diameter to allow the production of 300mm (12 in.)wafers.

Germanium(Ge) was a widely used early semiconductor material but its thermal sensitivity makes it less useful than silicon. Today, germanium is often alloyed with silicon for use in very-high-speed SiGe devices.

Gallium arsenide(GaAs) is also widely used in high-speed devices but so far, it has been difficult to form large-diameter bowls of this material, limiting the wafer diameter to sizes significantly smaller than silicon wafers thus making mass production of GaAs devices significantly more expensive than silicon. Other less common materials are also in use or under investigation.

Silicon carbide(SiC) has found some application as the raw material for bluelight-emitting diodes(LEDs) and is being investigated for use in semiconductor devices that could withstand very high operating temperaturesand environments with the presence of significant levels ofionizing radiation. Variousindiumcompounds (indium arsenide, indiumantimonde, and indiumphosphide) are also being used in LEDs and solid statelaser diodes.Seleniumsulfideis being studied in the manufacture ofphotovoltaic solar cells. The most common use fororganic semiconductorsisOrganic light-emitting diodes.Semiconductors are the foundation of modernelectronics, including radio, computers, and telephones. Semiconductor-based electronic components includetransistors,solar cells, many kinds of diodesincluding thelight-emitting diode(LED), the silicon controlled rectifier, photo-diodes, and digital and analog integrated circuits. Increasing understanding of semiconductor materials and fabrication processes has made possible continuing increases in the complexity and speed of semiconductor devices, an effect known asMoore's law.

Semiconductors are defined by their unique electric conductive behavior. Metals are goodconductorsbecause at theirFermi level, there is a large density of energetically available states that each electron can occupy. Electrons can move quite freely between energy levels without a high energy cost. Metal conductivity decreases with temperature increase because thermal vibrations ofcrystal latticedisrupt the free motion of electrons.Insulators, by contrast, are very poor conductors of electricity because there is a large difference in energies (called aband gap) between electron-occupied energy levels and empty energy levels that allow for electron motion.In the classic crystalline semiconductors, electrons can have energies only within certain bands (ranges). The range of energy runs from the ground state, in which electrons are tightly bound to the atom, up to a level where the electron can escape entirely from the material. Each energy band corresponds to a large number of discretequantum statesof the electrons. Most of the states with low energy (closer to the nucleus) are occupied, up to thevalence band.

Semiconductors and insulators are distinguished frommetalsby the population of electrons in each band. The valence band in any given metal is nearly filled with electrons under usual conditions, and metals have many free electrons with energies in the conduction band. In semiconductors, only a few electrons exist in the conduction band just above the valence band, and an insulator has almost no free electrons.

The ease with which electrons in the semiconductor can be excited from the valence band to the conduction band depends on theband gap. The size of this energy gap (band gap) determines whether a material is semiconductor or aninsulator(nominally this dividing line is roughly 4eV).

In acrystal, many atoms are adjacent and many energy levels are possible for electrons. Since there are so many (on the order of 1022) atoms in a macroscopic crystal, the resulting energy states available for electrons are very closely spaced. Since theHeisenberg principlelimits the precision of any measurement of the combination of an electron's momentum (related to energy) and its position, in a crystal effectively the available energy levels form a continuous band of allowed energy levels.

The concept ofholescan also be applied tometals, where theFermi levellieswithinthe conduction band. With most metals theHall effectindicates electrons are the charge carriers. However, some metals have a mostly filled conduction band. In these, the Hall effect reveals positive charge carriers, which are not the ion-cores, but holes. In the case of a metal, only a small amount of energy is needed for the electrons to find other unoccupied states to move into, and hence for current to flow. Sometimes even in this case it may be said that a hole was left behind, to explain why the electron does not fall back to lower energies: It cannot find a hole. In the end in both materials electron-phononscattering and defects are the dominant causes forresistance.The conductivity of semiconductors may easily be modified by introducing impurities into theircrystal lattice. The process of adding controlled impurities to a semiconductor is known asdoping. The amount of impurity, or dopant, added to anintrinsic(pure) semiconductor varies its level of conductivity. Doped semiconductors are referred to asextrinsic. By adding impurity to pure semiconductors, the electrical conductivity may be varied by factors of thousands or millions.

A 1cm3specimen of a metal or semiconductor has of the order of 1022atoms. In a metal, every atom donates at least one free electron for conduction, thus 1cm3of metal contains on the order of 1022free electrons. Whereas a 1cm3of sample pure germanium at 20C, contains about 4.21022atoms but only 2.51013free electrons and 2.51013holes. The addition of 0.001% of arsenic (an impurity) donates an extra 1017free electrons in the same volume and the electrical conductivity is increased by a factor of 10,000.

ICs were made possible by experimental discoveries showing thatsemiconductor devicescould perform the functions ofvacuum tubesand by mid-20th-century technology advancements insemiconductor device fabrication. The integration of large numbers of tinytransistorsinto a small chip was an enormous improvement over the manual assembly of circuits using discreteelectronic components. The integrated circuits, mass productioncapability, reliability, and building-block approach tocircuit designensured the rapid adoption of standardized Integrated Circuits in place of designs using discrete transistors.There are two main advantages of ICs overdiscrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit byphotolithographyrather than being constructed one transistor at a time. Furthermore, much less material is used to construct a packaged IC die than to construct a discrete circuit. Performance is high because the components switch quickly and consume little power (compared to their discrete counterparts) as a result of the small size and close proximity of the components. As of 2012, typical chip areas range from a few square millimeters to around 450mm2, with up to 9 milliontransistorsper mm2. Theelectrical resistanceof anelectrical conductoris the opposition to the passage of anelectric currentthrough that conductor; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical notion of friction. TheSIunit of electrical resistance is theohm(), while electrical conductance is measured insiemens(S).

An object of uniform cross section has a resistance proportional to itsresistivityand length and inversely proportional to its cross-sectional area. All materials show some resistance, except forsuperconductors, which have a resistance of zero.

Objects such as wires that are designed to have low resistance so that they transfer current with the least loss of electrical energy are called conductors. Objects that are designed to have a specific resistance so that they can dissipate electrical energy or otherwise modify how a circuit behaves are calledresistors. Conductors are made of high-conductivitymaterials such as metals, in particular copper and aluminium. Resistors, on the other hand, are made of a wide variety of materials depending on factors such as the desired resistance, amount of energy that it needs to dissipate, precision, and costs.3.2 List of Components: RESISTORS

1. R1 ________2.2M

2. R2 ________100K

3. R3 ________2.2M

4. R4 ________1K

5. R5________12K

6. R6________15K

CAPACITORS

7. C1 ________22P

8. C2 ________22P

9. C3 ________0.22 F

10. C4 ________100 F

11. C5_________47P

12. C6 _________0.1 F

13. C7_________ 0.1 F

14. C8_________ 0.01 F

15. C9__________4.7 F

16. IC CA3130

17. IC NE555

18. T1 BC548

19. LED

20. ANTENNA

21. PIEZO BUZZER

22. 5 INCH LONG ANTENNA

23. ON/OFF SWITCH

24. POWER SUPPLY

3.3 Components Description:3.3.1 Resistors:

Figure 3.1: ResistorsA 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 = IRResistors 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.Significance:Resistors are found in nearly every circuit because their ability to limit current allows them to protect electronics from circuit overload or destruction. Diodes, for example, are current sensitive and so are almost always coupled with a resistor when they are placed inside of a circuit. Resistors are also combined with other electrical components to form important fundamental circuits. They can be paired with capacitors to perform as filters or voltage dividers. Another role is that of the formation of oscillatory AC circuits when they are coupled with capacitors and inductors.

Construction:Resistors are typically formed from carbon encased in lacquer but may be made from conductors or semiconductors. Wire-wound ones are made from coils of metal wire and are extremely accurate and heat resistant. Carbon film resistors are made from carbon on a ceramic cylinder and photo resistors, also called photocells, are made from materials such as cadmium-sulfide.

Function:Because resistors convert electrical energy into heat they form heating elements in irons, toasters, heaters, electric stoves, hair dryers and similar devices. Their resistive properties cause them to generate light and are used to create filaments in light bulbs.

As voltage dividers, resistors are placed in series with each other. Their function is to produce a particular voltage from an input that is fixed or variable. The output voltage is proportional to that of the input and is usually smaller. Voltage dividers are useful for components that need to operate at a lesser voltage than that supplied by the input.

Resistors also help filter signals and are used in oscillatory circuits in televisions and radios.

Resistors are used withtransducersto makesensor subsystems. Transducers are electronic components which convert energy from one form into another, where one of the forms of energy is electrical. Alight dependent resistor, orLDR, is an example of aninput transducer. Changes in the brightness of the light shining onto the surface of the LDR result in changes in its resistance. As will be explained later, an input transducer is most often connected along with a resistor to make a circuit called apotential divider. In this case, the output of the potential divider will be a voltage signal which reflects changes in illumination.

Microphones and switches are input transducers.Output transducersinclude loudspeakers, filament lamps and LEDs. Can you think of other examples of transducers of each type?

In other circuits, resistors are used to direct current flow to particular parts of the circuit, or may be used to determine the voltage gain of an amplifier. Resistors are used with capacitors to introduce time delays.

Most electronic circuits require resistors to make them work properly and it is obviously important to find out something about the different types of resistor available, and to be able to choose the correct resistor value, in,, or M, for a particular application.

3.3.2 Capacitors:

Figure 3.2: 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.

Capacitance (symbol C) is a measure of a capacitor's ability tostore charge. A large capacitance means that more charge can be stored. Capacitance is measured in farads, symbol F. However 1F is very large, so prefixes (multipliers) are used to show the smaller values: (micro) means 10-6(millionth), so 1000000F = 1F

n (nano) means 10-9(thousand-millionth), so 1000nF = 1F

p (pico) means 10-12(million-millionth), so 1000pF = 1nFUses of Capacitors:Capacitors are used for several purposes:Timing- For example with a555timerICcontrolling thecharginganddischarging.

Smoothing- For example in apowersupply.

Coupling- For example between stages of anaudiosystemand to connect aloudspeaker.

Filtering- For example in the tone control of anaudiosystem.

Tuning- For example in aradiosystem.

Storing energy- For example in a camera flash circuit.

Energy storage:A capacitor can store electric energy when disconnected from its charging circuit, so it can be used like a temporarybattery. Capacitors are commonly used in electronic devices to maintain power supply while batteries are being changed. (This prevents loss of information in volatile memory.)

Conventional electrostatic capacitors provide less than 360joulesper kilogram of energy density, while capacitors using developing technology can provide more than 2.52kilojoulesper kilogram. Incar audiosystems, large capacitors store energy for theamplifierto use on demand.

Power conditioning:Reservoir capacitorsare used inpower supplieswhere they smooth the output of a full or half waverectifier. They can also be used incharge pumpcircuits as the energy storage element in the generation of higher voltages than the input voltage.

Capacitors are connected in parallel with the power circuits of most electronic devices and larger systems (such as factories) to shunt away and conceal current fluctuations from the primary power source to provide a "clean" power supply for signal or control circuits. Audio equipment, for example, uses several capacitors in this way, to shunt away power line hum before it gets into the signal circuitry. The capacitors act as a local reserve for the DC power source, and bypass AC currents from the power supply. This is used incar audioapplications, when a stiffening capacitor compensates for the inductance and resistance of the leads to thelead-acidcar battery.

Power factor correction:In electric power distribution, capacitors are used forpower factor correction. Such capacitors often come as three capacitors connected as athree phaseload. Usually, the values of these capacitors are given not in farads but rather as areactive powerin volt-amperes reactive (VAr). The purpose is to counteract inductive loading from devices likeelectric motorsandtransmission linesto make the load appear to be mostly resistive. Individual motor or lamp loads may have capacitors for power factor correction, or larger sets of capacitors (usually with automatic switching devices) may be installed at a load center within a building or in a large utilitysubstation.

Noise filters and snubbers:When an inductive circuit is opened, the current through the inductance collapses quickly, creating a large voltage across the open circuit of the switch or relay. If the inductance is large enough, the energy will generate anelectric spark, causing the contact points to oxidize, deteriorate, or sometimes weld together, or destroying a solid-state switch. Asnubbercapacitor across the newly opened circuit creates a path for this impulse to bypass the contact points, thereby preserving their life; these were commonly found incontact breakerignition systems, for instance. Similarly, in smaller scale circuits, the spark may not be enough to damage the switch but will stillradiateundesirableradio frequency interference(RFI), which afiltercapacitor absorbs. Snubber capacitors are usually employed with a low-value resistor in series, to dissipate energy and minimize RFI. Such resistor-capacitor combinations are available in a single package.

Capacitors are also used in parallel to interrupt units of a high-voltagecircuit breakerin order to equally distribute the voltage between these units. In this case they are called grading capacitors.In schematic diagrams, a capacitor used primarily for DC charge storage is often drawn vertically in circuit diagrams with the lower, more negative, plate drawn as an arc. The straight plate indicates the positive terminal of the device, if it is polarized.

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.

(1) Ceramic capacitor: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.

Figure 3.3: 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:

(i) disc, resin coated, with through-hole leads

(ii) multi-layer rectangular block, surface mount(iii) bare leadless disc, sits in a slot in the PCB and is soldered in place, used for UHF applications

(iv) tube shape, not popular now

(2) Electrolytic capacitor:

Figure 3.4: electrolytic capacitorAn 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.

Electrolytic capacitors can have a very high capacitance, allowing filters made with them to have very low corner frequencies.

3.3.3 Transistor:

Figure 3.5: TransistorsA transistor is a semiconductor device commonly used to amplify or switch electronic signals. A transistor is made of a solid piece 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, the transistor provides amplification of a signal. Some transistors are packaged individually but most are found in integrated circuits.

The transistor is the fundamental building block of modern electronic devices, and its presence is ubiquitous in modern electronic systems.

The first BJTs were made fromgermanium(Ge).Silicon(Si) types currently predominate but certain advanced microwave and high performance versions now employ thecompound semiconductormaterialgallium arsenide(GaAs) and thesemiconductor alloysilicon germanium(SiGe). Single element semiconductor material (Ge and Si) is described aselemental.Rough parameters for the most common semiconductor materials used to make transistors are given in the table to the right; these parameters will vary with increase in temperature, electric field, impurity level, strain, and sundry other factors.

Thejunction forward voltageis the voltage applied to the emitter-base junction of a BJT in order to make the base conduct a specified current. The current increases exponentially, as the junction forward voltage is increased. The values given in the table are typical for a current of 1 mA (the same values apply to semiconductor diodes). The lower the junction forward voltage the better, as this means that less power is required to "drive" the transistor. The junction forward voltage for a given current decreases with increase in temperature. For a typical silicon junction the change is 2.1 mV/C.In some circuits special compensating elements (sensistors) must be used to compensate for such changes.

The density of mobile carriers in the channel of a MOSFET is a function of the electric field forming the channel and of various other phenomena such as the impurity level in the channel. Some impurities, called dopants, are introduced deliberately in making a MOSFET, to control the MOSFET electrical behavior.

Theelectron mobilityandhole mobilitycolumns show the average speed that electrons and holes diffuse through the semiconductor material with anelectric fieldof 1 volt per meter applied across the material. In general, the higher the electron mobility the faster the transistor can operate. The table indicates that Ge is a better material than Si in this respect. However, Ge has four major shortcomings compared to silicon and gallium arsenide:

Its maximum temperature is limited; it has relatively highleakage current; it cannot withstand high voltages; it is less suitable for fabricating integrated circuits.

Because the electron mobility is higher than the hole mobility for all semiconductor materials, a given bipolarNPN transistortends to be swifter than an equivalentPNP transistortype. GaAs has the highest electron mobility of the three semiconductors. It is for this reason that GaAs is used in high frequency applications. A relatively recent FET development, thehigh electron mobility transistor(HEMT), has ahetero structure(junction between different semiconductor materials) of aluminium gallium arsenide (AlGaAs)-gallium arsenide (GaAs) which has twice the electron mobility of a GaAs-metal barrier junction. Because of their high speed and low noise, HEMTs are used in satellite receivers working at frequencies around 12GHz.

Maximum junction temperaturevalues represent a cross section taken from various manufacturers' data sheets. This temperature should not be exceeded or the transistor may be damaged.

AlSi junctionrefers to the high-speed (aluminumsilicon) metalsemiconductor barrier diode, commonly known as aSchottky diode. This is included in the table because some silicon power IGFETs have aparasiticreverse Schottky diode formed between the source and drain as part of the fabrication process. This diode can be a nuisance, but sometimes it is used in the circuit.

Transistor works in such a manner that a current is applied at one end consisting of one pair of terminals; it brings changes in the current flowing through another pair of terminals at other end. Since, the controlled power can be much more than the controlling power, there takes place the amplification of a signal. Info to know about transistor is that there are some transistors which are packaged individually however; normally the transistors are embedded in integrated circuits.

One gets an idea about the importance of transistor from the fact that nowadays, the use of transistor is almost there in every electronic device. It wont be inappropriate to say about transistor that it has become the fundamental building block of modern electronic devices, and its presence is everywhere in modern electronic systems.

The transistor considered as the main component in almost all walks of modern electronics, and is termed as one of the greatest inventions of modern times.

The importance of transistor in today's life resides on its capability to be mass produced using a highly automated process which is possible due to semiconductor device fabrication. It has resulted in making lower cost transistors. Moreover it can perform multiple functions as transistor can act as an amplifier by controlling its output in proportion to the input signal. Or, it can also be used as a switch in high power applications as well as low power application like logic gates.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.Transistors are commonly used as electronic switches, both for high-power applications such asswitched-mode power suppliesand for low-power applications such aslogic gates.

In a grounded-emitter transistor circuit, such as the light-switch circuit shown, as the base voltage rises, the emitter and collector current rises exponentially. The collector voltage drops because of reduced resistance from collector to emitter. If the voltage difference between the collector and emitter were zero (or near zero), the collector current would be limited only by the load resistance (light bulb) and the supply voltage. This is calledsaturationbecause current is flowing from collector to emitter freely. When saturated the switch is said to beon.Providing sufficient base drive current is a key problem in the use of bipolar transistors as switches. The transistor provides current gain, allowing a relatively large current in the collector to be switched by a much smaller current into the base terminal. The ratio of these currents varies depending on the type of transistor, and even for a particular type, varies depending on the collector current. In the example light-switch circuit shown, the resistor is chosen to provide enough base current to ensure the transistor will be saturated.

In any switching circuit, values of input voltage would be chosen such that the output is either completely off,or completely on. The transistor is acting as a switch, and this type of operation is common indigital circuitswhere only "on" and "off" values are relevant.Thecommon-emitter amplifieris designed so that a small change in voltage (Vin) changes the small current through the base of the transistor; the transistor's current amplification combined with the properties of the circuit mean that small swings inVinproduce large changes inVout.

Various configurations of single transistor amplifier are possible, with some providing current gain, some voltage gain, and some both.

Frommobile phonestotelevisions, vast numbers of products include amplifiers forsound reproduction, radio transmission, andsignal processing. The first discrete transistor audio amplifiers barely supplied a few hundred milliwatts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved. Modern transistor audio amplifiers of up to a few hundredwattsare common and relatively inexpensive.Advantages:The key advantages that have allowed transistors to replace their vacuum tube predecessors in most applications are:(i) Small size and minimal weight, allowing the development of miniaturized electronic devices.

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

(iii) Lower possible operating voltages, making transistors suitable for small, battery-powered applications.

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

(v) Lower power dissipation and generally greater energy efficiency.

(vi) Higher reliability and greater physical ruggedness.

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

(viii) Complementary devices available, facilitating the design of complementary-symmetry circuits, something not possible with vacuum tubes.

(ix) Insensitivity to mechanical shock and vibration, thus avoiding the problem of microphonics in audio applications.

Limitations:(i) 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.

(ii) 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.

(iii) 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.

(iv) Silicon transistors are much more sensitive than electron tubes to an electromagnetic pulse, such as generated by an atmospheric nuclear explosion.Bipolar junction 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. In an NPN transistor operating in the active region, the emitter-base junction is 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.[14] 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.3.3.4 LED:

Electronic symbol

Figure 3.6: 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 LEDwas introduced as a practical electronic component in 1962.../../../Documents and Settings/Administrator/Desktop/pro hiren/Led.htm - cite_note-LemelsonMIT-1 All early devices emitted low-intensity red light, but modern 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 1mm2) with integrated optical components to shape its radiation pattern and assist in reflection.../../../Documents and Settings/Administrator/Desktop/pro hiren/Led.htm - cite_note-2LEDs 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.

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.

Figure 3.7: Various types LEDsAlight-emittingdiode(LED) is asemiconductorlight source.LEDs are used as indicator lamps in many devices and are increasingly used for other lighting. Appearing as practical electronic components in 1962,early LEDs emitted low-intensity red light, but modern versions are available across thevisible,ultraviolet, andinfraredwavelengths, with very high brightness.

When a light-emitting diode is switched on,electronsare able to recombine with holes within the device, releasing energy in the form ofphotons. This effect is calledelectroluminescenceand the color of the light (corresponding to the energy of the photon) is determined by the energy band gap of the semiconductor. An LED is often small in area (less than 1mm2), and integrated optical components may be used to shape itsradiation pattern. LEDs present many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. However, LEDs powerful enough for room lighting are relatively expensive and require more precise current and heat management than compactfluorescent lampsources of comparable output.

Light-emitting diodes are used in applications as diverse asaviation lighting,automotive lighting, advertising, general lighting, andtraffic 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 are also used inseven-segment display.

The LED consists of a chip of semiconducting materialdopedwith impurities to create ap-n junction. As in other diodes, current flows easily from the p-side, oranode, to the n-side, orcathode, but not in the reverse direction. Charge-carriers electronsandholes flow into the junction fromelectrodeswith different voltages. When an electron meets a hole, it falls into a lowerenergy level, and releasesenergy in the form of aphoton.

Thewavelengthof the light emitted, and thus its color depends on theband gapenergy of the materials forming thep-n junction. Insilicon orgermaniumdiodes, the electrons and holes recombine by anon-radiative transition, which produces no optical emission, because these areindirect band gapmaterials. The materials used for the LED have adirect band gapwith energies corresponding to near-infrared, visible, or near-ultraviolet light.

LED development began with infrared and red devices made withgallium arsenide. Advances inmaterials sciencehave enabled making devices with ever-shorter wavelengths, emitting light in a variety of colors.

LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on its surface. P-type substrates, while less common, occur as well. Many commercial LEDs, especially GaN/InGaN, also usesapphiresubstrate.

Most materials used for LED production have very highrefractive indices. This means that much light will be reflected back into the material at the material/air surface interface. Thus,light extraction in LEDsis an important aspect of LED production, subject to much research and development.

Typical indicator LEDs are designed to operate with no more than 3060milliwatts(mW) of electrical power. Around 1999,Philips Lumiledsintroduced power LEDs capable of continuous use at onewatt. These LEDs used much larger semiconductor die sizes to handle the large power inputs. Also, the semiconductor dies were mounted onto metal slugs to allow for heat removal from the LED die. LED power densities up to 300W/cm2 have been achieved.

One of the key advantages of LED-based lighting sources is highluminous efficiency. White LEDs quickly matched and overtook the efficacy of standard incandescent lighting systems. In 2002, Lumileds made five-watt LEDs available with aluminous efficacyof 1822 lumens per watt (lm/W). For comparison, a conventionalincandescent light bulbof 60100 watts emits around 15 lm/W, and standard fluorescent lightsemit up to 100 lm/W. A recurring problem is that efficacy falls sharply with rising current. This effect is known asdroop and effectively limits the light output of a given LED, raising heating more than light output for higher current.

As of 2012, the Lumiled catalog gives the following as the best efficacy for each color:

This method involvescoatingLEDs of one color (mostly blue LEDs made of InGaN) withphosphorsof different colors to form white light; the resultant LEDs are calledphosphor-based white LEDs. A fraction of the blue light undergoes theStokes shiftbeing transformed from shorter wavelengths to longer. Depending on the color of the original LED, phosphors of different colors can be employed. If several phosphor layers of distinct colors are applied, the emitted spectrum is broadened, effectively raising thecolor rendering index(CRI) value of a given LED.

Phosphor-based LED efficiency losses are due to the heat loss from the Stokes shift and also other phosphor-related degradation issues. Their efficiencies compared to normal LEDs depend on the spectral distribution of the resultant light output and the original wavelength of the LED itself. For example, the efficiency of a typical YAG yellow phosphor based white LED ranges from 3 to 5 times the efficiency of the original blue LED because of the greaterluminous efficacyof yellow compared to blue light. Due to the simplicity of manufacturing the phosphor method is still the most popular method for making high-intensity white LEDs. The design and production of a light source or light fixture using a monochrome emitter with phosphor conversion is simpler and cheaper than a complexRGBsystem, and the majority of high-intensity white LEDs presently on the market are manufactured using phosphor light conversion.

Among the challenges being faced to improve the efficiency of LED-based white light sources is the development of more efficient phosphors. Today the most efficient yellow phosphor is still the YAG phosphor, with less than 10% Stoke shift loss. Losses attributable to internal optical losses due to re-absorption in the LED chip and in the LED packaging itself account typically for another 10% to 30% of efficiency loss. Currently, in the area of phosphor LED development, much effort is being spent on optimizing these devices to higher light output and higher operation temperatures. For instance, the efficiency can be raised by adapting better package design or by using a more suitable type of phosphor. Conformal coating process is frequently used to address the issue of varying phosphor thickness.

White LEDs can also be made bycoatingnear-ultraviolet(NUV) LEDs with a mixture of high-efficiencyeuropium-based phosphors that emit red and blue, plus copper and aluminium-doped zinc sulfide (ZnS:Cu, Al) that emits green. This is a method analogous to the wayfluorescent lampswork. This method is less efficient than blue LEDs with YAG:Ce phosphor, as theStokes shiftis larger, so more energy is converted to heat, but yields light with better spectral characteristics, which render color better. Due to the higher radiative output of the ultraviolet LEDs than of the blue ones, both methods offer comparable brightness. A concern is that UV light may leak from a malfunctioning light source and cause harm to human eyes or skin.LEDs are used increasingly in aquarium lights. In particular for reef aquariums, LED lights provide an efficient light source with less heat output to help maintain optimal aquarium temperatures. LED-based aquarium fixtures also have the advantage of being manually adjustable to emit a specific color-spectrum for ideal coloration of corals, fish, and invertebrates while optimizing photosynthetically active radiation (PAR), which raises growth and sustainability of photosynthetic life such as corals, anemones, clams, and macroalgae. These fixtures can be electronically programmed to simulate various lighting conditions throughout the day, reflecting phases of the sun and moon for a dynamic reef experience. LED fixtures typically cost up to five times as much as similarly rated fluorescent or high-intensity discharge lighting designed for reef aquariums and are not as high output to date.

The lack of IR or heat radiation makes LEDs ideal forstag