PROJECT

on

WIRELESS AUDIO TRANSMITTER FOR TV

Submitted by

Mr. Abhishek Sharma 1120503

Mr. Danish Khan 1120528

Mr. Pawan Gupta 1120520

in

Electronics & Telecommunication Engineering

Under the Guidance of

Prof Zafar Khan

Anjuman-i-Islam's

M.H.Saboo Siddik College of Engineering

8, M.H. Saboo Siddik Polytechnic Road, Byculla-400008

University of Mumbai

2014-15

CERTIFICATE

This is to certify that

Mr. Abhishek Sharma

Mr. Danish Khan

Mr.Pawan Gupta

are bonafide students of M.H.Saboo Siddik College of Engineering, Mumbai, they

have successfully carried out the project titled “Wireless Audio Transmitter For

Tv” in the partial fulfillment of requirement of mini project II in electronics and

telecommunication engineering from Mumbai University during the academic year

2014-2015.

______________

(Er. Zafar Khan)

Project Guide

___________________ ____________________

Internal Examiner External Examiner

___________________ __________________

Head Of Department Principal

ACKNOWLEDGEMENT

We give our sincere thanks to our guide Prof Zafar Khan for his guidance and

constant support, whenever we needed it. We also extend thanks to our teaching staff

whom we approached for academic help for our project. We also thank the project

co ordinators and non teaching staff as well for arranging necessary facilities. We are

highly grateful to the Head of Department(EXTC), the Principal and the Director for

providing facilities, conductive environment and encouragement.

Mr. Abhishek Sharma ____________

Mr. Danish Khan ____________

Mr. Pawan Gupta ____________

ABSTRACT

This project allows you to watch your favourite TV programmes late at night without disturbing

other family members. The project uses a FM transmission principle. Most modern TVs are

nowadays equipped with audio-in/out and video-in/out RCA sockets. Using an RCA-to-RCA cord,

connect the audio output of your TV to the transmitter’s input. Adjust the gain of the audio

preamplifier for clear reception in a portable FM receiver equipped with an earphone socket.

CONTENTS

Chapter 1: Introduction 01

1.1: Motivation 01

1.2: Objective 01

1.3:Block Diagram 02

Chapter 2: Hardware Requirements 03

2.1: Transistor 03

2.2: Battery 04

2.3: Berg Connector 08

2.4: Antenna 08

2.5: Led 11

2.6: Diode 1N4007 15

2.7: Resistor And Preset 17

2.8: Capacitor And Trimmer 21

Chapter 3: Schematic Diagram 26

3.1: Description 27

Chapter 4: Layout Diagram 28

Chapter 5: Hardware Testing 29

5.1: Countinuity Test 29

5.2: Power On Test 29

Chapter 6: Future Scope 30

Chapter 7: Conclusion 31

References 32

List of Figures

Fig 1.3 Block Diagram

Fig 2.1 BC547 Transistor Pinouts

Fig 2.1.1 BC 547 Transistor

Fig 2.2 Battery

Fig 2.3 Berg Connector

Fig 2.4 Antenna

Fig 2.5 White Led Spectrum

Fig 2.5.1 Different Types Of Led’s

Fig 2.6(a) 1N4007 Diode

Fig 2.6(b) PN Junction Diode

Fig 2.7 Resistors

Fig 2.7.2 Trimpot(PRESET)

Fig 2.8 Capacitor

Fig 2.8.1 Trimmer Capacitor

Fig 3 Schematic Diagram

Fig 4 Layout Diagram

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CHAPTER 1: Introduction

If u want to watch TV during night times it will be a disturbance for other family members. This

circuit is useful in order to get out of this problem by using headphones instead of speakers.

Wireless communication means the transfer of information without the use of enhanced electrical

conductors. The purpose of this circuit can be achieved by using both radio frequency or infrared

waves generated from a transmitter place near the sound source. But it is efficient to choose the

radio frequencies because they will give you much more flexibility to change how and where

you listen. In these days people willing to spend lots of money on their home theatre systems and

speakers. But speakers has high cost. So, the cheaper option will be wireless TV headphones.

They can be used effectively upto 20 feet.

1.1. Motivation:

Everyone require something or other kind of motivation, if we consider today’s world most of

the systems used robotics as well as the communication became wireless. The use of hardware

has reduced to the least by using vlsi techniques. This project is basically motivated by the

people of society who are busy with there work and don’t get time to be refreshed without any

disturbance. We have seen old age is most problem facing age, as in old age peoples hearing

capability is reduced, So by this project they can also enjoy their programs without disturbing

any other. Also,if we combine wireless transmission with other technology then it can be

program to perform multiple task by minimum usage of physical structure. It can produce a

system with maximum efficiency and minimum efforts.

1.2. Objective:

The essential aims to built a WIRELESS TV HEADPHONE CIRCUIT are

To design one main transmitter circuit unit that takes analog input to the receiver of

output.

9

To replace the cable/wire with wireless system.

To design and implement a system that transmits the stereo audio sound, then seperates it

into wireless speaker units using two different frequencies

Fig 1.3 Block Diagram

10

CHAPTER 2: Hardware Requirements

2.1. Transistor

BC547

The BC547 transistor is an NPN Epitaxial Silicon Transistor. The BC547 transistor is a general-

purpose transistor in small plastic packages. It is used in general-purpose switching and

amplification BC847/BC547 series 45 V, 100 mA NPN general-purpose transistors.

Fig 2.1 BC 547 Transistor Pinouts

The BC547 transistor is an NPN bipolar transistor, in which the letters "N" and "P" refer to the

majority charge carriers inside the different regions of the transistor. Most bipolar transistors

used today are NPN, because electron mobility is higher than hole mobility in semiconductors,

allowing greater currents and faster operation. NPN transistors consist of a layer of P-doped

semiconductor (the "base") between two N-doped layers. A small current entering the base in

common-emitter mode is amplified in the collector output. In other terms, an NPN transistor is

"on" when its base is pulled high relative to the emitter. The arrow in the NPN transistor symbol

is on the emitter leg and points in the direction of the conventional current flow when the device

is in forward active mode. One mnemonic device for identifying the symbol for the NPN

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transistor is "not pointing in." An NPN transistor can be considered as two diodes with a shared

anode region. In typical operation, the emitter base junction is forward biased and the base

collector junction is reverse biased. In an NPN transistor, for example, when a positive voltage is

applied to the base emitter junction, the equilibrium between thermally generated carriers and the

repelling electric field of the depletion region becomes unbalanced, allowing thermally excited

electrons to inject into the base region. These electrons wander (or "diffuse") through the base

from the region of high concentration near the emitter towards the region of low concentration

near the collector. The electrons in the base are called minority carriers because the base is doped

p-type which would make holes the majority carrier in the base.

Fig 2.1.1 BC 547 Transistor

Whenever base is high, then current starts flowing through base and emitter and after that only

current will pass from collector to emitter. So that the LED which is connected to collector will

glow to indicate that transistor is ON.

2.2. Battery

An electrical battery is a combination of one or more electrochemical cells, used to convert

stored chemical energy into electrical energy. The battery has become a common power source

for many household and industrial applications.

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Batteries may be used once and discarded, or recharged for years as in standby power

applications. Miniature cells are used to power devices such as hearing aids and wristwatches;

larger batteries provide standby power for telephone exchanges or computer data centers.

2.2.1 WORKING OF BATTERY:

A battery is a device that converts chemical energy directly to electrical energy. It consists of a

number of voltaic cells; each voltaic cell consists of two half cells connected in series by a

conductive electrolyte containing anions and cat ions. One half-cell includes electrolyte and the

electrode to which anions (negatively-charged ions) migrate, i.e. the anode or negative electrode;

the other half-cell includes electrolyte and the electrode to which cat ions (positively-charged

ions) migrate, i.e. the cathode or positive electrode. In the red ox reaction that powers the battery,

reduction (addition of electrons) occurs to cat ions at the cathode, while oxidation (removal of

electrons) occurs to anions at the anode. The electrodes do not touch each other but are

electrically connected by the electrolyte. Many cells use two half-cells with different electrolytes.

In that case each half-cell is enclosed in a container, and a separator that is porous to ions but not

the bulk of the electrolytes prevents mixing.

Each half cell has an electromotive force (or emf), determined by its ability to drive electric

current from the interior to the exterior of the cell. The net emf of the cell is the difference

between the emfs of its half-cells. Therefore, if the electrodes have emfs and, in other words, the

net emf is the difference between the reduction potentials of the half-reactions.

The electrical driving force or across the terminals of a cell is known as the terminal voltage

(difference) and is measured in volts. The terminal voltage of a cell that is neither charging nor

discharging is called the open-circuit voltage and equals the emf of the cell. Because of internal

resistance, the terminal voltage of a cell that is discharging is smaller in magnitude than the

open-circuit voltage and the terminal voltage of a cell that is charging exceeds the open-circuit

voltage. An ideal cell has negligible internal resistance, so it would maintain a constant terminal

voltage of until exhausted, then dropping to zero. If such a cell maintained 1.5 volts and stored a

13

charge of one Coulomb then on complete discharge it would perform 1.5 Joule of work. In actual

cells, the internal resistance increases under discharge, and the open circuit voltage also

decreases under discharge. If the voltage and resistance are plotted against time, the resulting

graphs typically are a curve; the shape of the curve varies according to the chemistry and internal

arrangement employed.

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

into electrical energy. Since the invention of the first battery (or "voltaic pile") in 1800 by

Alessandro Volta, batteries have become a common power source for many household and

industrial applications. According to a 2005 estimate, the worldwide battery industry generates

US$48 billion in sales each year, with 6% annual growth. There are two types of batteries:

primary batteries (disposable batteries), which are designed to be used once and discarded, and

secondary batteries (rechargeable batteries), which are designed to be recharged and used

multiple times. Miniature cells are used to power devices such as hearing aids and wristwatches;

larger batteries provide standby power for telephone exchanges or computer data centers.

2.2.2 Principle of operation

A battery is a device that converts chemical energy directly to electrical energy. It consists of a

number of voltaic cells; each voltaic cell consists of two half cells connected in series by a

conductive electrolyte containing anions and cations. One half-cell includes electrolyte and the

electrode to which anions (negatively charged ions) migrate, i.e., the anode or negative electrode;

the other half-cell includes electrolyte and the electrode to which cations (positively charged

ions) migrate, i.e., the cathode or positive electrode. In the redox reaction that powers the battery,

cations are reduced (electrons are added) at the cathode, while anions are oxidized (electrons are

removed) at the anode. The electrodes do not touch each other but are electrically connected by

the electrolyte. Some cells use two half-cells with different electrolytes. A separator between half

cells allows ions to flow, but prevents mixing of the electrolytes.

Each half cell has an electromotive force (or emf), determined by its ability to drive electric

current from the interior to the exterior of the cell. The net emf of the cell is the difference

14

between the emfs of its half-cells, as first recognized by Volta. Therefore, if the electrodes have

emfs and , then the net emf is ; in other words, the net emf is the difference

between the reduction potentials of the half-reactions. The electrical driving force or

across the terminals of a cell is known as the terminal voltage (difference) and is measured in

volts. The terminal voltage of a cell that is neither charging nor discharging is called the open-

circuit voltage and equals the emf of the cell. Because of internal resistance, the terminal voltage

of a cell that is discharging is smaller in magnitude than the open-circuit voltage and the terminal

voltage of a cell that is charging exceeds the open-circuit voltage. An ideal cell has negligible

internal resistance, so it would maintain a constant terminal voltage of until exhausted, then

dropping to zero. If such a cell maintained 1.5 volts and stored a charge of one coulomb then on

complete discharge it would perform 1.5 joule of work. In actual cells, the internal resistance

increases under discharge, and the open circuit voltage also decreases under discharge. If the

voltage and resistance are plotted against time, the resulting graphs typically are a curve; the

shape of the curve varies according to the chemistry and internal arrangement employed.

As stated above, the voltage developed across a cell's terminals depends on the energy release of

the chemical reactions of its electrodes and electrolyte. Alkaline and carbon-zinc cells have

different chemistries but approximately the same emf of 1.5 volts; likewise NiCd and NiMH

cells have different chemistries, but approximately the same emf of 1.2 volts. On the other hand

the high electrochemical potential changes in the reactions of lithium compounds give lithium

cells emfs of 3 volts or more.

15

Fig 2.2 Battery

2.3. Berg Connector

A Berg connector is a brand of electrical connector used in computer hardware. Berg connectors

are manufactured by Berg Electronics Corporation of St. Louis, Missouri, a division of

Framatome Connectors International.

Berg connectors have a 2.54 mm (=.100 inch) pitch, pins are square (0.64 mm x 0.64 mm =

approx. 0.025 x 0.025 inch), and usually come as single or double row connectors.

Many types of Berg connectors exist. Some of the more familiar ones used in IBM PC

compatibles are:

Fig 2.3 Berg Connector

the 4-pin polarized Berg connectors used to connect 3.5-inch floppy disk drive units to

the power supply unit, usually referred to as simply a "floppy power connector", but often

also referred to as SP4.

the 2-pin Berg connectors used to connect the front panel lights, turbo switch, and reset

button to the motherboard, and

the 2-pin Berg connectors used as jumpers for motherboard configuration.

2.4. Antenna

A Yagi-Uda antenna, commonly known simply as a Yagi antenna or Yagi, invented in 1926

by Shintaro Uda and Hidetsugu Yagi, of Tohoku Imperial University, Japan, is a directional

16

antenna system consisting of an array of a dipole and additional closely coupled parasitic

elements (usually a reflector and one or more directors). The dipole in the array is driven, and

another element, typically 5% longer, effectively operates as a reflector. Other parasitic elements

shorter than the dipole may be added in front of the dipole and are referred to as directors. This

arrangement increases antenna directionality and gain in the preferred direction over a single

dipole. Directional antennas such as the Yagi-Uda are commonly referred to as beam antennas or

high-gain antennas (particularly for transmitting). Yagi antennas with added corner reflectors

and/or UHF elements are commonly used for reception of television broadcasts. Yagi-Uda

antennas are also widely used by amateur radio operators for communication on frequencies

from short wave, through VHF/UHF, and into microwave bands. Amateur radio operators

(hams) often homebrew this type of antenna, and have published many technical papers and

software.

Description:

Yagi-Uda antennas are directional along the axis perpendicular to the dipole in the plane of the

elements, from the reflector through the driven element and out via the director(s). Typically all

elements are spaced about a quarter-wavelength apart. (See also log-periodic antenna.) All

elements usually lie in the same plane, supported on a single boom or crossbar; however, they do

not have to assume this coplanar arrangement: for example, some commercially available Yagi-

Uda antennas for television reception have several reflectors arranged to form a corner reflector

behind the dipole. The bandwidth of a Yagi-Uda antenna, which is usually defined as the

frequency range for which the antenna provides a good match to the transmission line to which it

is attached, is determined by the length, diameter and spacing of the elements. For most designs

bandwidth is typically only a few percent of the design frequency. Yagi-Uda antennas can be

designed to operate on multiple bands. Such designs are more complicated, using pairs of

resonant parallel coil and capacitor combinations (called a "trap" or LC) in the elements. The

trap serves to isolate the outer portion of an element from the inner portion at the trap design

frequency. In practice the higher frequency traps are located closest to the boom of the antenna.

Typically, a triband beam will have two pairs of traps per element.

17

Fig 2.4 Antenna

2.4.1. Theory of Operation:

In order to understand the operation of a Yagi-Uda, a simple antenna consisting of a reflector,

driven element and a single director as discussed in the previous section will be studied. The

driven element is typically a λ/2 dipole and is the only member of the structure that is directly

excited.

All the other elements are considered parasitic. That is, they reradiate power which they receive

from the driven element (they also interact with each other).One way of thinking about it is to

consider a parasitic element to be a normal dipole element with a gap at its centre, the feed point.

Now instead of attaching the antenna to a load (such as a receiver) we connect it to a short

circuit. As is well known in transmission line theory, a short circuit reflects all of the incident

power 180 degrees out of phase. So one could as well model the operation of the parasitic

element as the superposition of a dipole element receiving power and sending it down a

transmission line to a matched load, and a transmitter sending the same amount of power down

the transmission line back toward the antenna element.

If the wave from the transmitter were 180 degrees out of phase with the received wave at that

point, it would be equivalent to just shorting out that dipole at the feed point (making it a solid

element).The fact that the parasitic element involved isn't exactly resonant but is somewhat

shorter (or longer) than λ/2 modifies the phase of the element's current with respect to its

18

excitation from the driven element. The so-called reflector element, being longer than λ/2, has an

inductive reactance which means the phase of the its current lags the phase of the open-circuit

voltage that would be induced by the received field.

The director element, on the other hand, being shorter than λ/2 has a capacitive reactance with

the voltage phase lagging that of the current. If the parasitic elements were broken in the centre

and driven with the same voltage applied to the centre element, then such a phase difference in

the currents would be equivalent to a phased array, enhancing the radiation in one direction and

decreasing it in the opposite direction. Thus one can appreciate the mechanism by which

parasitic elements of unequal length can lead to a unidirectional radiation pattern.

2.5. Led

Light Emitting Diodes (LED) have recently become available that are white and bright, so bright

that they seriously compete with incandescent lamps in lighting applications. They are still pretty

expensive as compared to a GOW lamp but draw much less current and project a fairly well

focused beam.

The diode in the photo came with a neat little reflector that tends to sharpen the beam a little but

doesn't seem to add much to the overall intensity.

When run within their ratings, they are more reliable than lamps as well. Red LEDs are now

being used in automotive and truck tail lights and in red traffic signal lights. You will be able to

detect them because they look like an array of point sources and they go on and off instantly as

compared to conventional incandescent lamps.

19

LEDs are monochromatic (one color) devices. The color is determined by the band gap of the

semiconductor used to make them. Red, green, yellow and blue LEDs are fairly common. White

light contains all colors and cannot be directly created by a single LED. The most common form

of "white" LED really isn't white. It is a Gallium Nitride blue LED coated with a phosphor that,

when excited by the blue LED light, emits a broad range spectrum that in addition to the blue

emission, makes a fairly white light.

There is a claim that these white LED's have a limited life. After 1000 hours or so of operation,

they tend to yellow and dim to some extent. Running the LEDs at more than their rated current

will certainly accelerate this process.

There are two primary ways of producing high intensity white-light using LED’S. One is to use

individual LED’S that emit three primary colours—red, green, and blue—and then mix all the

colours to form white light. The other is to use a phosphor material to convert monochromatic

light from a blue or UV LED to broad-spectrum white light, much in the same way a fluorescent

light bulb works. Due to metamerism, it is possible to have quite different spectra that appear

white.

Fig 2.5 Whits Led Spectrum

20

LEDs are semiconductor devices. Like transistors, and other diodes, LEDs are made out of

silicon. What makes an LED give off light are the small amounts of chemical impurities that are

added to the silicon, such as gallium, arsenide, indium, and nitride.

When current passes through the LED, it emits photons as a byproduct. Normal light bulbs

produce light by heating a metal filament until it is white hot. LEDs produce photons directly

and not via heat, they are far more efficient than incandescent bulbs.

Fig : circuit symbol

Not long ago LEDs were only bright enough to be used as indicators on dashboards or electronic

equipment. But recent advances have made LEDs bright enough to rival traditional lighting

technologies. Modern LEDs can replace incandescent bulbs in almost any application.

2.5.1. Types of LED’S

LEDs are produced in an array of shapes and sizes. The 5 mm cylindrical package is the most

common, estimated at 80% of world production. The color of the plastic lens is often the same as the

actual color of light emitted, but not always. For instance, purple plastic is often used for infrared

LEDs, and most blue devices have clear housings. There are also LEDs in extremely tiny packages,

such as those found on blinkers and on cell phone keypads. The main types of LEDs are miniature,

high power devices and custom designs such as alphanumeric or multi-color.

Fig 2.5.1: Different types of LED’S

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2.5.2. Advantages of using LEDs

Efficiency:

LEDs produce more light per watt than incandescent bulbs; this is useful in

battery powered or energy-saving devices.

Size:

LEDs can be very small (smaller than 2 mm2) and are easily populated onto

printed circuit boards.

On/Off time:

LEDs light up very quickly. A typical red indicator LED will achieve full

brightness in microseconds. LEDs used in communications devices can have even

faster response times.

Cycling:

LEDs are ideal for use in applications that are subject to frequent on-off cycling,

unlike fluorescent lamps that burn out more quickly when cycled frequently, or

HID lamps that require a long time before restarting.

Cool light:

In contrast to most light sources, LEDs radiate very little heat in the form of IR

that can cause damage to sensitive objects or fabrics. Wasted energy is dispersed

as heat through the base of the LED.

Lifetime:

LEDs can have a relatively long useful life. One report estimates 35,000 to 50,000

hours of useful life, though time to complete failure may be longer.

No Toxicity:

LEDs do not contain mercury, unlike fluorescent lamps.

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2.5.3. Disadvantages of using LED’s

High price:

LEDs are currently more expensive, price per lumen, on an initial capital cost

basis, than most conventional lighting technologies.

Temperature dependence:

LED performance largely depends on the ambient temperature of the operating

environment. Over-driving the LED in high ambient temperatures may result in

overheating of the LED package, eventually leading to device failure.

Voltage sensitivity:

LEDs must be supplied with the voltage above the threshold and a current below

the rating. This can involve series resistors or current-regulated power supplies.

Area light source:

LEDs do not approximate a “point source” of light, but rather a lambertian

distribution. So LEDs are difficult to use in applications requiring a spherical light

field. LEDs are not capable of providing divergence below a few degrees. This is

contrasted with lasers, which can produce beams with divergences of 0.2 degrees

or less.

Blue Hazard:

There is increasing concern that blue LEDs and cool-white LEDs are now capable

of exceeding safe limits of the so-called blue-light hazard as defined in eye safety.

2.6. Diode 1N4007

Diodes are used to convert AC into DC these are used as half wave rectifier or full wave

rectifier. Three points must he kept in mind while using any type of diode.

1.Maximum forward current capacity

2.Maximum reverse voltage capacity

3.Maximum forward voltage capacity

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Fig 2.6(a): 1N4007 diodes

The number and voltage capacity of some of the important diodes available in the market

are as follows:

Diodes of number IN4001, IN4002, IN4003, IN4004, IN4005, IN4006 and IN4007 have

maximum reverse bias voltage capacity of 50V and maximum forward current capacity of 1

Amp.

Diode of same capacities can be used in place of one another. Besides this diode of more

capacity can be used in place of diode of low capacity but diode of low capacity cannot be used

in place of diode of high capacity. For example, in place of IN4002; IN4001 or IN4007 can be

used but IN4001 or IN4002 cannot be used in place of IN4007.The diode BY125made by

company BEL is equivalent of diode from IN4001 to IN4003. BY 126 is equivalent to diodes

IN4004 to 4006 and BY 127 is equivalent to diode IN4007.

Fig 2.6(b):PN Junction diode

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2.6.1. PN JUNCTION OPERATION

Now that you are familiar with P- and N-type materials, how these materials are joined together

to form a diode, and the function of the diode, let us continue our discussion with the operation

of the PN junction. But before we can understand how the PN junction works, we must first

consider current flow in the materials that make up the junction and what happens initially within

the junction when these two materials are joined together.

2.6.2. Current Flow in the N-Type Material

Conduction in the N-type semiconductor, or crystal, is similar to conduction in a copper wire.

That is, with voltage applied across the material, electrons will move through the crystal just as

current would flow in a copper wire. This is shown in figure 1-15. The positive potential of the

battery will attract the free electrons in the crystal. These electrons will leave the crystal and flow

into the positive terminal of the battery. As an electron leaves the crystal, an electron from the

negative terminal of the battery will enter the crystal, thus completing the current path. Therefore, the

majority current carriers in the N-type material (electrons) are repelled by the negative side of the

battery and move through the crystal toward the positive side of the battery.

2.6.3. Current Flow in the P-Type Material

Current flow through the P-type material is illustrated. Conduction in the P material is by

positive holes, instead of negative electrons. A hole moves from the positive terminal of the P

material to the negative terminal. Electrons from the external circuit enter the negative terminal

of the material and fill holes in the vicinity of this terminal. At the positive terminal, electrons

are removed from the covalent bonds, thus creating new holes. This process continues as the

steady stream of holes (hole current) moves toward the negative terminal.

2.7. Resistors

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A resistor is a two-terminal electronic component designed to oppose an electric current by

producing a voltage drop between its terminals in proportion to the current, that is, in accordance

with Ohm's law:

V = IR

Fig 2.7 Resistors

The primary characteristics of resistors are their resistance and the power they can

dissipate. 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.

A resistor is a two-terminal passive electronic component which implements electrical resistance

as a circuit element. When a voltage V is applied across the terminals of a resistor, a current I

will flow through the resistor in direct proportion to that voltage. The reciprocal of the constant

of proportionality is known as the resistance R, since, with a given voltage V, a larger value of R

further "resists" the flow of current I as given by Ohm's law:

Resistors are common 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). Resistors

26

are also implemented within integrated circuits, particularly analog devices, and can also be

integrated into hybrid and printed circuits.

The electrical functionality of a resistor is specified by its resistance: common commercial

resistors are manufactured over a range of more than 9 orders of magnitude. When specifying

that resistance in an electronic design, the required precision of the resistance may require

attention to the manufacturing tolerance of the chosen resistor, according to its specific

application. The temperature coefficient of the resistance may also be of concern in some

precision applications. Practical resistors are also specified as having a maximum power rating

which must exceed the anticipated power dissipation of that resistor in a particular circuit: this is

mainly of concern in power electronics applications. Resistors with higher power ratings are

physically larger and may require heat sinking. In a high voltage circuit, attention must

sometimes be paid to the rated maximum working voltage of the resistor.

The series inductance of a practical resistor causes its behaviour to depart from ohms law; this

specification can be important in some high-frequency applications for smaller values of

resistance. In a low-noise amplifier or pre-amp the noise characteristics of a resistor may be an

issue. The unwanted inductance, excess noise, and temperature coefficient are mainly dependent

on the technology used in manufacturing the resistor. They are not normally specified

individually for a particular family of resistors manufactured using a particular technology.[1]

A

family of discrete resistors is also characterized according to its form factor, that is, the size of

the device and position of its leads (or terminals) which is relevant in the practical manufacturing

of circuits using them.

This formulation of Ohm's law states that, when a voltage (V) is present across a resistance (R), a

current (I) will flow through the resistance. This is directly used in practical computations. For

example, if a 300 ohm resistor is attached across the terminals of a 12 volt battery, then a current

of 12 / 300 = 0.04 amperes (or 40 mill amperes) will flow through that resistor.

2.7.1. What is a trimpot?

A trimpot or trimmer potentiometer is a small potentiometer which is used for adjustment, tuning

and calibration in circuits. When they are used as a variable resistance (wired as a rheostat) they

are called preset resistors. Trimpots or presets are normally mounted on printed circuit boards

and adjusted by using a screwdriver. The material they use as a resistive track is varying, but the

most common is either carbon composition or cermet. Trimpots are designed for occasional

adjustment and can often achieve a high resolution when using multi-turn setting screws. When

trimmer potentiometers are used as a replacement for normal potentiometers, care should be

taken as their designed lifespan is often only 200 cycles.

Trimpot definition

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Trimmer potentiometers and preset resistors are small variable resistors which are used in

circuits for tuning and (re)calibration.

2.7.2. Types of trimpots

Several different versions of trimpots are available, using different mounting methods (through

hole, smd) and adjusting orientations (top, side) as well as single and multi-turn variations.

2.7.2(a) Single turn:

Single turn trimmers/presets are very common and used where a resolution of one turn is

sufficient. They are the most cost effective variable resistors available.

Fig 2.7.2 Trimpot

2.7.2(b) Multi turn:

For higher adjustment resolutions, multi-turn trimpots are used. The amount of turns varies

between roughly 5-25, but 5, 12 or 25 turns are quite common. They are often constructed using

a worm-gear (rotary track) or leadscrew (linear track) mechanism to achieve the high resolution.

Because of their more complex construction and manufacturing, they are more costly than single

turn preset resistors. The lead screw packages can have a higher power rating because of their

increased surface area.

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2.8. Capacitor

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.

Fig 2.8 Capacitor

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.

The properties of capacitors in a circuit may determine the resonant frequency and quality factor

of a resonant circuit, power dissipation and operating frequency in a digital logic circuit, energy

capacity in a high-power system, and many other important aspects.

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

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

electric field develops in the dielectric that stores energy and produces a mechanical force

between the conductors. An ideal capacitor is characterized by a single constant value,

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

potential difference between them.

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

hence capacitor conductors are often called "plates", referring to an early means of construction.

In practice the dielectric between the plates passes a small amount of leakage current and also

has an electric field strength limit, resulting in a breakdown voltage, while the conductors and

leads introduce an undesired inductance and resistance.

Fig: Battery of four Leyden jars in Museum Boerhaave, Leiden, the Netherlands.

In October 1745, Ewald Georg von Kleist of Pomerania in Germany found that charge could be

stored by connecting a high voltage electrostatic generator by a wire to a volume of water in a

hand-held glass jar. Von Kleist's hand and the water acted as conductors and the jar as a

dielectric (although details of the mechanism were incorrectly identified at the time). Von Kleist

found, after removing the generator, that touching the wire resulted in a painful spark. In a letter

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describing the experiment, he said "I would not take a second shock for the kingdom of France."

The following year, the Dutch physicist Pieter van Musschenbroek invented a similar capacitor,

which was named the Leyden jar, after the University of Leiden where he worked.

2.8.1. What are trimmer capacitors?

Trimmer capacitors are variable capacitors which serve the purpose of initial calibration of

equipment during manufacturing or servicing. They are not intended for end-user interaction.

Trimmer capacitors are almost always mounted directly on the PCB (Printed Circuit Board), so

the user does not have access to them, and set during manufacturing using a small screwdriver.

Due to their nature, trimmer capacitors are cheaper than full sized variable capacitors and rated

for many fewer adjustments.

Fig 2.8.1 Trimmer Capacitor

Trimmer capacitors are used to initially set oscillator frequency values, latencies, rise and fall

times and other variables in a circuit. Should the values drift over time, these trimmer capacitors

allow repairmen to re-calibrate equipment when needed. There are two types of trimmer

capacitors: air trimmer capacitor and ceramic trimmer capacitor.

Trimmer capacitor definition

A trimmer capacitor is a variable capacitor used for initial calibration and recalibration of

equipment. It is commonly mounted directly on a PCB and accessed only by professional

repairmen, not the end-user.

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2.8.2. Characteristics

1. Voltage rating, capacitance range, polarity

Trimmer capacitors can be rated for voltages up to 300 volts, although voltage ratings of up to

100 volts are much more common. Since trim caps are variable capacitors, they come in a

capacitance range rather than a single capacitance value. The minimum capacitance is usually

between 0.5 pF and 10 pF, while the maximum capacitance is usually between 1 pF and 120 pF.

The actual capacitance value can be varied between the minimum and maximum capacitance

values for a given trimmer capacitor, but it can never be set to zero. It is worth noting that

trimmer capacitors are not polarized.

2. Tolerances and accuracy

Trimmer capacitors do not boast a good capacitance value tolerance. Sometimes, the tolerances

can be as high as -0 to +100%. This means that a trimmer capacitor can have a maximum

capacitance two times larger than nominal. However, bad tolerances do not pose a great problem

to engineers because trimmer capacitors are variable. Even if the maximum value is different

between individual capacitors, they can still be set by turning the screwdriver a certain angle.

Accuracy depends mostly on the operator, as he can choose to spend more time in order to set

the capacitor to a desired value. Often, trimmer capacitors are set by robots instead of human

operators, and they can achieve much better precision. In order to achieve a better accuracy, it is

advised to use a non-metallic tool, since metal screwdrivers will introduce a source of

capacitance that will vary the capacitance value when the tool is moved away from the capacitor.

3. Construction and properties of trimmer capacitors

There are two types of trimmer capacitors: air trimmer capacitor and ceramic trimmer capacitor.

These two types use different materials as the dielectric. Both types use rotating action to change

the capacitance value. The construction of trimmer capacitors is similar to the construction of

their larger variant, the variable capacitor. Trimmer capacitors can be made of semi-circular

metal plates. One is fixed, while the other can be rotated using a screwdriver. The user changes

the capacitance by rotating the shaft and increasing or reducing the amount of overlap between

the two plates. Another way to make a trimmer capacitor is to place a metallic screw in a non-

conductive threaded cylinder. The screw represents one electrode, while the other is located at

the base of the cylinder. By rotating the screw, the distance between the two plates is varied

which results in a change of capacitance. This construction is used in RF and microwave

applications.

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2.8.3. Applications for trimmer capacitors

The potential applications for trimmer capacitors are numerous. They are used whenever there is

a capacitance value that needs to be matched to a certain circuit during the manufacturing

process. The reason for their use (instead of using precise fixed-value capacitors) is that other

elements in the circuit have their own tolerances and their values could differ by as much as 20%

from what the engineer expected to see in a circuit. In order to adapt to those tolerances, trimmer

capacitors are used. They are commonly used in various RF circuits, VHF through microwave.

Special non-magnetic types are used in medical devices such as MRI and NMR scanners, which

produce very high magnetic fields that would otherwise destroy capacitors containing

ferromagnetic materials such as steel. Other common applications include oscillators, tuners,

crystal oscillators and filters. Trimmer capacitors can be found in communication equipment

such as mobile radios and aerospace transmitters and receivers, signal splitters and CATV

amplifiers.

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CHAPTER 3: SCHEMATIC DIAGRAM

Fig 3 Schematic Diagram

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3.1 DESCRIPTION

3.1.1 OPERATION EXPLANATION

There are three components that work together to create and transmit a signal to where it can be

recorded or amplified. The first part is the actual microphone. The second part is the wireless

microphone is the transmitter. The final component, the antenna broadcasts that signal to a short

distance.

Transistor Q1 acts as an audio preamplifier. Transistor Q2 works as an FM oscillator and

modulator in conjunction with other passive components. Trimmer capacitor VC1 connected

across inductor L1 can be varied to achieve the desired frequency. Inductor L1 comprises 4 to 6

turns of closely wound 25SWG enameled copper wire on 4mm dia. air core. A 20-30cm long

wire serves as an antenna.

Most modern TV’s are nowadays equipped with audio-in/out and video in/out sockets. Using an

appropriate cord, connect the audio output of your TV to the transmitter’s input. Adjust the gain

of the audio preamplifier with the help of preset VR1 for clear reception in a portable FM

receiver equipped with an earphone socket. This transmitter draws only a few milliampere of

current and doesn’t require on/off switch.

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CHAPTER 4: LAYOUT DIAGRAM

Fig 4 Layout Diagram

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CHAPTER 5: HARDWARE TESTING

5.1 CONTINUITY TEST:

In electronics, a continuity test is the checking of an electric circuit to see if current flows (that it

is in fact a complete circuit). A continuity test is performed by placing a small voltage (wired in

series with an LED or noise-producing component such as a piezoelectric speaker) across the

chosen path. If electron flow is inhibited by broken conductors, damaged components, or

excessive resistance, the circuit is "open".

This test is the performed just after the hardware soldering and configuration has been

completed. This test aims at finding any electrical open paths in the circuit after the soldering.

Many a times, the electrical continuity in the circuit is lost due to improper soldering, wrong and

rough handling of the PCB, improper usage of the soldering iron, component failures and

presence of bugs in the circuit diagram. We use a multi meter to perform this test. We keep the

multi meter in buzzer mode and connect the ground terminal of the multi meter to the ground.

We connect both the terminals across the path that needs to be checked. If there is continuation

then you will hear the beep sound.

5.2 POWER ON TEST:

This test is performed to check whether the voltage at different terminals is according to the

requirement or not. We take a multi meter and put it in voltage mode, and measure voltage at

different points in circuit to make sure we are getting required voltage at those particular points.

First we apply less voltage and check whether the capacitors are getting charged, it is indicated

by the lamp which is connected in series with supply and circuit. Initially lamp should glow fully

because initially when capacitors are not charged they act as short circuit and due to the flow of

short circuit current the series lamp glows, and when capacitors get gradually charged they act as

open circuit, in this condition the series lamp stops glowing. If it happens then we can conclude

that the circuit is working prope.

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CHAPTER 6: Future Scope

‘Wireless Audio Transmitter From Tv’ is still a young technology, so many consumers are

unaware of the advantages this type of interaction can bring to everyday life. In this chapter we

mention few future systems based on ‘Wireless Audio Transmitter From Tv’ which resembles

the fluency of this technique over others.

Primary goal of this project is to receive a audio signal from tv and listen to it from a certain

distance.Now a days everybody wants home theatre which is a theater built in a home,

designed to mimic (or exceed) commercial theater performance and feeling, more commonly

known as a home cinema.Also,this sound system or home theatre are very much costly,But this

project can really help you to experience the performance of theatre at no cost.Due to wireless

transmission cost is reduced upto a great extent.

Most important thing is that this can be used not only in TV applications,but also in

Computers,Laptops,Mobile and portable music system.This is very much effective where noise

volume has to be reduced.Also,it can be used as an alternative to Bluetooth technology, as this

consumes lesser power.

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CHAPTER 7

CONCLUSION

This is an excellent way of reducing the disturbances caused to others while watching our

favorite TV programs, so this must be encouraged among the people. Wireless audio

transmission is an area of communication that is always moving with technological

advancements. As the new digital radios become more available, dramatic improvements will be

heard by listeners. Careful design of the new transmissions systems will pay off with reduced

costs and improved performance and reliability. HD Radio FM is both robust and efficient in the

difficult mobile environment, SDR provides flexibility and Cognitive Radio will definitely

define a whole new level of wireless audio transmission from tv.

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References

[1] Russell Mohn, “A Three Transistor Discrete FM Transmitter,” ELEN 4314

Communications Circuits - Design Project, pp. 1, April 2007.

[2] “FM broadcasting in the United States”

[3] “The Future of Radio”. The Swedish Radio and TV Authority, 2008.

[4] T.U.M Swarna kumara et al., “A Mini Project on Simple FM-Transmitter”.

[5] E. F. Louis, Principles of Electronic Communication Systems. McGraw-Hill, 2008

[6] “Phase-Locked Loop Tutorial, PLL”

[7] C. Renee, “An Industrial White Paper: HD Radio”

[8] C. W. Kelly, “Digital HD Radio AM/FM Implementation Issues”, USA.

[9] C. W. Kelly, “HD-Radio: Real World Results in Asia”, USA.

[10] B. Groome, “HD Radio (I.B.O.C).”

[11] D. Ferrara, “Advantages and Disadvantages of HD Radio”

[12] D. Correy, “HD Radio: What it is and What it is not”

[13] www.beyondlogic.org

[14] www.wikipedia.org

[15] www.howstuffworks.com

[16] www.alldatasheets.com