Li-Fi audio transmission is the transmission of wireless data by using visible light as a medium of communication in which the receiver section interprets the incoming light which is detected using a solar panel and converts to the audible sound signal with the help of a speaker.

1. 1
A Mini Projectreport on
Li-Fi Audio Transmission
submitted in partial fulfillment of the requirement for the award of the degree of
BACHELOR OF TECHNOLOGY
IN
Electronics & Communication Engineering
Submitted
by
N Prem Kumar 16K81A0438
T Sriya Sharma 16K81A0458
Younesh Jayaraman 16K81A0460
Under the Guidance of
P Prasanna Kumari, Assistant Professor
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING
St. MARTIN’S ENGINEERING COLLEGE
UGC AUTONOMOUS
(Affiliated to Jawaharlal Nehru Technological University, Hyderabad)
Dhulapally, Secunderabad-500 100
NBA &NAAC A+ Accredited
2019-2020

2. 2
St.MARTIN’S ENGINEERINGCOLLEGE
UGC AUTONOMOUS
(Affiliated to Jawaharlal Nehru Technological University, Hyderabad)
Dhulapally, Secunderabad-500 100
NBA &NAAC A+ Accredited
2019-2020
Department Of Electronics & Communication Engineering
CERTIFICATE
This is to certify that the main-project work entitled “ Li-Fi Audio
Transmission ” is a bonafide work carried out by N Prem Kumar (16K81A0438), T
Sriya Sharma(16K81A0458), Younesh Jayaraman(16K81A0460) in partial
fulfillment of the requirements for the degree of Bachelor of Technology in
Electronics & Communication Engineering by the Jawaharlal Nehru Technological
University, Hyderabad during the academic year2019-2020.
The results embodied in this report have not been submitted to any other
University or Institution for the award of any degree.
INTERNAL GUIDE HEAD OF THE DEPARTMENT
P Prasanna Kumari Dr. B. Hari Krishna
EXTERNAL EXAMINER

3. 3
ACKNOWLEDGEMENT
We sincerely thank the management of our college St. MARTIN’S
ENGINEERING COLLEGE for providing the required facilities during our project
work.
We derive our great pleasure in expressing our sincere gratitude to our principal Dr.P.
Santosh Kumar Patra for his timely suggestions, which helped us to complete the
project work successfully.
It is the very auspicious moment we would like to express our gratitude to Dr. B. Hari
Krishna, Head of the Department, ECE for his consistent encouragement during the
progress of this project.
We take it as a privilege to thank our project coordinator Mrs. K Hanuja, Assistant
Professor, Department of ECE for the ideas that led to complete the project work and
we also thank them for their continuous guidance, support, continuousailing patience,
throughout the course of this work.
we sincerely thank our project Internal guide Mrs. P Prasanna Kumari, Assistant
Professor, Department of ECE for guidance and encouragement in carrying out this
project work.

4. 4
DECLARATION
We, the students of ‘Bachelor of Technology in Department of Electronics
and Communication Engineering’, session: 2016 – 2020, St. Martin’s Engineering
College, hereby declare that the project work entitled ‘Li-Fi Audio Transmission’ is
the outcome of our own bonafide work and is correct to the best of our knowledge and
this work has been undertaken taking care of Engineering Ethics. This result embodied
in this project report has not been submitted in any university for the award of any
degree.
N Prem Kumar T Sriya Sharma Younesh Jayaraman
16K81A0438 16K81A0458 16K81A0460

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CONTENTS
TITLE Page no.
Abstract……………………………………………………………...viii
List of Figures……………………………………………………......ix
List of Tables……………………………………………………........xi
Chapter 1: Introduction
1.1 Introduction....................................................................1
Chapter 2: Block Diagram
2.1 Description.....................................................................4
2.1.1 Audio input..........................................................5
2.1.2 LEDs....................................................................5
2.1.3 Photodetector.......................................................6
2.1.4 Amplifier circuit & Speaker................................7
2.1.5 Amplified Audio Output......................................8
Chapter 3 Components & Connections
3.1 Required components....................................................9
3.1.1 9V Battery..........................................................10
3.1.2 Resistors.............................................................11
3.1.3 Capacitors...........................................................12
3.1.4 Potentiometer......................................................13

6. 6
3.1.5 Solar Panel..........................................................14
3.1.6 Speaker...............................................................15
3.1.7 IC LM386...........................................................16
3.1.8 3.5mm Jack.........................................................17
3.1.9 LED Strip............................................................17
Chapter 4 Circuit Diagram & Working
4.1 Transmitter Circuit of Li-Fi...........................................21
4.2 Receiver Circuit of Li-Fi...............................................21
4.3 Working.........................................................................22
Chapter 5 PCB Layout
5.1 PCB Design....................................................................24
5.2 Electronic Design Automation tools..............................24
5.3 PCB Design Procedure...................................................25
5.3.1 Drawing the circuit Schematic..............................25
5.3.2 Design rule check & netlist creation.....................26
5.3.3 Creating the PCB artwork.....................................27
5.3.4 PCB Fabrication....................................................27
5.3.5 Etching..................................................................28
5.3.6 Drilling..................................................................29
5.3.7 Soldering...............................................................30

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Chapter 6 ComparisonBetweenLi-Fi & Wi-Fi................................34
Chapter 7 Result
7.1 Result..............................................................................36
Chapter 8 Conclusion
8.1 Advantages.....................................................................37
8.1.1 Capacity.................................................................37
8.1.2 Efficiency...............................................................37
8.1.3 Availability............................................................38
8.1.4 Security..................................................................38
8.1.5 No Limit for Connectivity.....................................38
8.2 Applications....................................................................38
8.2.1 Education System..................................................39
8.2.2 Medical Applications.............................................39
8.2.3 Cheaper Internet Aircraft.......................................39
8.2.4 Underwater Applications.......................................40
8.2.5 Disaster Management............................................40
8.2.6 Applications in Sensitive Areas.............................40
8.2.7 Traffic Management...............................................41
8.2.8 Replacement for Other Technologies.....................41
8.3 Conclusion.......................................................................41

8. 8
8.4 Future Scope...................................................................42
References..............................................................................................44

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ABSTRACT
The term Li-Fi stands for “Light Fidelity”, the next generation of internet,
where Light will be used as a medium to transmit the data and has higher speeds than
Wi-Fi as the speed of light is much faster than the radio waves which is used in Wi-Fi.
In Wireless communication, Wi-Fi is the most versatile and effective
technology which compact with radio frequencies for data transmission. But because
of multiple accesses, Wi-Fi is facing many challenges namely capacity, availability,
efficiency and security. The Wi-Fi emits radio waves which are very harmful to the
patients and the radio waves interpret the medical instruments.
This paper focuses on developing a light fidelity (Li-Fi) based system and
analyzing its performance. This protocol can be adapted where radio waves are
restricted, such as airplanes hospitals, and in some research facilities. Li-Fi is a novel
technology for high-density wireless data transfer relieving no radio interferences in
confined areas so it can be used in biosensors to measure various health parameters.
This technology envisions a future where data for laptops, smartphones, and tablets will
be transmitted in an economic and eco-friendly medium of light in a room.

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LIST OF FIGURES
TITLE Page no.
1.1 The Future of the Internet- Li-Fi...................................................2
1.2 Electromagnetic Spectrum............................................................3
2.1 Block Diagram of Li-Fi Audio Transmission...............................4
2.2 LED Strip......................................................................................6
2.3 PhotodiodeSymbol.......................................................................6
2.4 Solar Panel as Photodetector.........................................................7
3.1 Required Connections.................................................................10
3.2 9V Battery...................................................................................10
3.3 Internal Structure of a Capacitor.................................................12
3.4 Potentiometer 10k.......................................................................13
3.5 Solar Panel..................................................................................14
3.6 Speaker........................................................................................15
3.7 IC LM386....................................................................................16
3.8 Jack Cable....................................................................................17
3.9 LED Symbol................................................................................17
3.10 LED Architecture......................................................................19
4.1 Circuit Diagram of Li-Fi Audio Transmission............................20
4.2 Transmitter Circuit.......................................................................21

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4.3 Receiver Circuit..........................................................................22
5.1 Schematic Diagram.....................................................................26
5.2 PCB Layout of Li-Fi...................................................................33
7.1 Result..........................................................................................36

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LIST OF TABLES
TITLE Page no.
3.1 Colour Coding of Resistors........................................................11
6.1 Li-Fi Vs Wi-Fi............................................................................34
6.2 Comparison of current & future wireless technology................35

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CHAPTER 1
INTRODUCTION
1.1 Introduction:
Over the past few years, there has been a rapid growth in the utilization of the
RF region of the electromagnetic spectrum. This is because of the huge growth in the
number of mobile phone subscriptions in recent times. This has been causing a rapid
reduction in the free spectrum for future devices. Light-fidelity (Li-Fi) operates in the
visible light spectrum of the electromagnetic spectrum i.e. it uses visible light as a
medium of transmission rather than the traditional radio waves.
Li-Fi stands for Light-Fidelity. Li-Fi is the transmission of data using visible
light by sending data through an LED light bulb that varies in intensity faster than the
human eye can follow. If the LED is on, the photodetector registers a binary one;
otherwise it‟s a binary zero. The idea of Li-Fi was introduced by a German physicist,
Harald Hass, which he also referred to as “Data through Illumination”. The term Li-Fi
was first used by Haas in his TED Global talk on Visible Light Communication.
According to Hass, the light, which he referred to as „DLight‟, can be used to produce
data rates higher than 1 Gigabit per second which is much faster than our average
broadband connection.

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Fig 1.1 The Future of the Internet- Li-Fi
The high-speed achievement of Li-Fi can be explained using the frequency
spectrum of Electromagnetic Radiations. From the electromagnetic spectrum, we can
see that the frequency band of the visible light is between 430THz to 770THz and that
of Radio Frequency Band is between 1Hz to 3THz, Hence the Frequency Bandwidth
of the visible light is about 400 times greater than the Radio Frequency Bandwidth. So
a number of bits can be transferred through this Bandwidth than in the radio frequency
bandwidth. Hence Data rate will be higher in the LiFi and higher speed can be achieved.
Using Li-Fi we can transmit any data that can be transferred using a
conventional Wi-Fi network. That can be Images, Audio, Video, Internet connectivity,
etc.. but the advantages over the Wi-Fi Network are High speed, Increased Security,
More Number of Connected Devices, and Less cost. In the coming years, a number of
devices that support Li-Fi will hit the Market. It is estimated that the compound annual
growth of Li-Fi market will be of 82% from 2015 to 2018 and to be worth over $6
billion per year by 2018.

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Fig 1.1 Electromagnetic Spectrum
This Mini Project discusses the implementation of the most basic Li-Fi based
system to transmit Sound signals from one device to another through visible light. The
purpose is to demonstrate only the working of the simplest model of Li-Fi with no major
consideration of the data transfer speed. This model will demonstrate how the notion
of one-way communication via visible light works, in which Light-emitting diodes
(LEDs) are employed as the light sources or Transmitter antennas. The model will
transmit digital signals via direct modulation of the light. The emitted light will be
detected by an optical receiver. In addition to the demonstration purpose, the model
enables investigation into the features of the visible light and LEDs incorporated in the
communication model.

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CHAPTER 2
BLOCK DIAGRAM
Fig 2.1 Block Diagram of Li-Fi Audio Transmission
2.1 Description:
The basic block diagram consists of
1. Audio Input from source
2. LEDs
3. Photodetector
4. Amplifier Circuit
5. Speaker
6. Amplified Audio at Destination

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2.1.1 Audio Input:
An audio signal is a representation of sound, typically using a level of electrical
voltage for analog signals, and a series of binary numbers for digital signals. Audio
signals have frequencies in the audio frequency range of roughly 20 to 20,000 Hz,
which corresponds to the lower and upper limits of human hearing.
Input consists of an analog signal, which is usually taken from the Audio output
of the Mobile Phone, Laptop or any other Musical Instruments. The signal will be at a
low voltage level which is not enough to drive an LED, So in order to drive the LEDs,
we have to amplify the signal using amplifiers.
2.1.2 LEDs:
A light-emitting diode (LED) is a semiconductor light source that emits light
when current flows through it. Electrons in the semiconductor recombine with electron
holes, releasing energy in the form of photons. The color of the light (corresponding to
the energy of the photons) is determined by the energy required for electrons to cross
the bandgap of the semiconductor.] White light is obtained by using multiple
semiconductors or a layer of light-emitting phosphor on the semiconductor device.
In Li-Fi Transmission, the most important requirement of the light source is its
ability to turn ON and OFF Repeatedly in very short intervals (in ns range). So we use
LEDs that have very low switching time. These LEDs turn ON and OFF in Nanosecond
based on the Pulse signal. Since switching taking at a faster rate, it cannot be detected
by the human eye. So it 5 will appear as illuminating even though they are blinking.
Thus the modulated signal is transmitted to the receiver via Visible Light.

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Fig 2.2 LED Strip
2.1.3 Photodetector:
Fig 2.3 Photodiode Symbol

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The transmitted signal from the LEDs has to be detected, demodulated and
acknowledged. So in order to detect the message signal from the blinking LED light,
we use a photocell or a Solar Cell (which comprises large no of photocells connected
in series). The solar cell detects only the variation of the light since the blinking can be
easily detected and the output of the solar cell will be the message signal in the analog
form. So using solar we could detect and demodulate the message signal transmitted.
Fig 2.4 Solar Panel as Photodetector
2.1.4 Amplifier Circuit & Speaker:
The demodulated signal will be at a low voltage range. So it is Amplified to the
arbitrary voltage level using an amplifier. This amplifier will be the same type of
amplifier which we used on the transmitter side. This is due to the fact that if any phase
errors occurred, it will be cleared at this stage. The speaker will convert the electrical
signal to the audible form using electromagnets present in the speaker.

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2.1.5 Amplified Audio Output:
The demodulated audible signal is transmitted from the speaker to its final
destination. So that the audience can listen to the amplified audio message that has been
transmitted from the transmitter at the source.

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CHAPTER 3
COMPONENTS & CONNECTIONS
3.1 Required Components:
1. 9V battery
2. Resistors
3. Capacitors
4. Potentiometer 10k
5. Solar Panel
6. Speaker
7. IC LM386
8. 3.5mm jack
9. LED strip

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Fig 3.1 Required Connections
3.1.1 9V Battery:
Fig 3.2 9V Battery

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The nine-volt battery, or a 9-volt battery, is a common size of the battery that was
introduced for the early transistor radios. It has a rectangular prism shape with rounded
edges and a polarized snap connector at the top. This type is commonly used in walkie-
talkies, clocks and smoke detectors.
The nine-volt battery format is commonly available in primary carbon-zinc and
alkaline chemistry, in primary lithium iron disulfide, and in a rechargeable form in
nickel-cadmium, nickel-metal hydride, and lithium-ion. Mercury-oxide batteries of this
format, once common, have not been manufactured in many years due to their mercury
content.
3.1.2 Resistors:
Table 3.1 Colour Coding of Resistors

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A resistor is a passive two-terminal electrical component that implements electrical
resistance as a circuit element. In electronic circuits, resistors are used to reduce
current flow, adjust signal levels, to divide voltages, bias active elements, and terminate
transmission lines, among other uses. Resistors used in the project are 10k ohm, 100
ohms.
3.1.3 Capacitors:
Fig 3.3 Internal structure of a capacitor
A capacitor is a device that stores electrical energy in an electric field. It is a
passive electronic component with two terminals. The effect of a capacitor is known

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as capacitance. Capacitors used for this project are one 0.1 uf, two 10 uf, one 100 uf,
one 1000 uf.
3.1.4 Potentiometer10k:
Fig 3.4 Potentiometer 10k
A potentiometer, informally a pot, is a three-terminal resistor with a sliding or
rotating contact that forms an adjustable voltage divider. If only two terminals are used,
one end and the wiper, it acts as a variable resistor or rheostat.
The measuring instrument called a potentiometer is essentially a voltage divider
used for measuring electric potential (voltage); the component is an implementation of
the same principle, hence its name.
Potentiometers are commonly used to control electrical devices such as volume
controls on audio equipment. Potentiometers operated by a mechanism can be used as

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position transducers, for example, in a joystick. Potentiometers are rarely used to
directly control significant power (more than a watt) since the power dissipated in the
potentiometer would be comparable to the power in the controlled load.
3.1.5 Solar Panel:
Photovoltaic solar panels absorb sunlight as a source of energy to generate
direct current electricity. A photovoltaic (PV) module is a packaged, connected
assembly of photovoltaic solar cells available in different voltages and wattages.
Photovoltaic modules constitute the photovoltaic array of a photovoltaic
system that generates and supplies solar electricity in commercial and residential
applications. The most common application of solar energy collection outside
agriculture is solar water heating systems.
Fig 3.5 SolarPanel

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3.1.6 Speaker:
A loudspeaker or loud-speaker or speaker is an electroacoustic transducer; a
device that converts an electrical audio signal into a corresponding sound.[2] The most
widely used type of speaker in the 2010s is the dynamic speaker, invented in 1924
by Edward W. Kellogg and Chester W. Rice. The dynamic speaker operates on the
same basic principle as a dynamic microphone, but in reverse, to produce sound from
an electrical signal. When an alternating current electrical audio signal is applied to
its voice coil, a coil of wire suspended in a circular gap between the poles of
a permanent magnet, the coil is forced to move rapidly back and forth due to Faraday's
law of induction, which causes a diaphragm (usually conically shaped) attached to the
coil to move back and forth, pushing on the air to create sound waves.
Besides this most common method, there are several alternative technologies
that can be used to convert an electrical signal into sound. The sound source (e.g., a
sound recording or a microphone) must be amplified or strengthened with an audio
power amplifier before the signal is sent to the speaker.
Fig 3.6 Speaker

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3.1.7 IC LM386:
IC LM386 is an audio amplifier can amplify sound that is given from
Microphone. This circuit can be used as a “Small mic and loudspeaker system” for a
small space like a room. This circuit can also be used in many applications like portable
music players, intercoms, radio amplifiers, TV sound systems, Ultrasonic drivers, etc.
It can also be used as a sound sensor for microcontrollers. It is inexpensive, low power
operated and only needs few components to work. This circuit depends on the LM386
IC to increase sound.
LM386 is a low voltage sound intensifier and oftentimes utilized as a part of
battery controlled music gadgets like radios, guitars, toys and so forth. The pick up go
is20 to 200, pick up is inside set to 20 (without utilizing outside segment) yet can be
expanded to 200 by utilizing resistor and capacitor between PIN 1 and 8, or just with a
capacitor. Voltage picks up essentially implies that Voltage out is 200 times the Voltage
IN. LM386 has a wide supply voltage go 4- 12v. The following is the Pin outline of
LM386.
Fig 3.7 IC LM386

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3.1.8 3.5mmjack:
3.5mm jack is a phone connector, also known as phone jack, audio
jack, headphone jack or jack plug, is a family of electrical connectors typically used
for analog audio signals. The phone connector was invented for use in telephone
switchboards in the 19th century and is still widely used.
Fig 3.8 Jack Cable
3.1.9 LED Strip:
Fig 3.9 LED Symbol

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The most important requirement that a light source has to meet in order to serve
communication purposes is the ability to be switched on and off repeatedly in very short
intervals. By utilizing the advantage of fast switching characteristics of LED‟s
compared with the conventional lightning, the LED illumination is used as a
communication source. Since the illumination exists everywhere, it is expected that the
LED illumination device will act as a lighting device and a communication transmitter
simultaneously everywhere in the near future.
Typically, red, green, and blue LEDs emit a band of spectrum, depending on
the material system. The white LED draws much attention to the illumination devices.
Comparing the LED illumination with the conventional illumination such as fluorescent
lamps and 14 incandescent bulbs, the LED illumination has many advantages such as
high efficiency, environment-friendly manufacturing, design flexibility, long lifetime,
and better spectrum performance.
LEDs emit light when energy levels change in the semiconductor diode. This
shift in energy generates photons, some of which are emitted as light. The specific
wavelength of the light depends on the difference in energy levels as well as the type
of semiconductor material used to form the LED chip.
The solid-state design allows LEDs to withstand shock, vibration, frequent
switching i.e; electrical on and off a shock and environmental i.e; mechanical shocks
extremes without compromising their famous long life typically 100,000 hours or more.
The basic LED consists of a semiconductor diode chip mounted in the reflector cup of
a lead frame that is connected to electrical (wire bond) wires and then encased in a solid
epoxy lens. The architecture of the LED is shown in Fig.

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Fig 3.10 LED Architecture

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CHAPTER 4
CIRCUIT DIAGRAM & WORKING
Fig 4.1 Circuit diagram of Li-Fi Audio Transmission

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4.1 Transmitter circuit of Li-Fi:
On the transmitter side, we have a white Bright LED and a battery that is
connected to 3.5mm jack and jack will be connected to an audio source. Here we are
using a battery to power up the LEDs because there is less power coming from the audio
source which is not enough to power the LEDs. Connections are shown below in the
circuit diagram:
Fig 4.2 Transmitter Circuit
4.2 ReceiverCircuit of Li-Fi:
On the receiver side, we are using the Solar panel and a speaker that is
connected by an Aux cable.

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Fig 4.3 Receiver Circuit
4.3 Working:
On the transmitter side, when we connect 3.5mm jack to audio source
LED will glow but there is no fluctuation in the intensity of light when the audio source
is OFF. As soon as you play the audio, you will see that there is a frequent change in
the intensity of light. When you increase the volume, LED’s intensity is changing faster
than the human eye can follow.
A solar panel is so sensitive that it can catch small intensity change and
correspondingly there is a change in the voltages at the output of the solar panel. So,
when the light of LED falls on the panel, voltages will vary according to the intensity
of light. Then voltages of solar panels are fed into an amplifier (Speaker) which
amplifies the signal and giving the audio output through the speaker connected to the
amplifier.

35. 35
The output will come as long as the solar panel is in contact with LEDs. You
can put the LEDs at max. 15-20cm distance from the solar panel to get clear audio
output. You can further increase the range by increasing the area of solar panel and
higher wattage Power LED.

36. 36
CHAPTER 5
PCB LAYOUT
5.1 PCB Design:
The design of a printed circuit board (PCB) can be considered as the last step in
electronic circuit design as well as the first step in production. It plays an important role
in the performance and reliability of electronic circuits, the productivity of the PCB‟s
its assembling, and its serviceability depends on design. All these factors get reflected
in a piece of electronic equipment. It is clear that the task of PCB design is not very
simple or always straight forward. The schematic is a follower by layout generation.
The layout design is the stage where engineering capacity combined with creativity is
the governing inputs.
5.2 Electronic design automation tools:
Most product testing is being done is done with the help of computer programs.
The term Electronic Design Automation (EDA) is being used to describe the use of
these tools. With the help of advanced powerful computing systems and interactive
software tools and development of electronic circuits has undergone automation. Thus
the software and hardware tools, which enable this automation includes PCB designing,
IC design, circuit simulation, etc. These tools help us in such a way that we can draw
the circuit; test the functioning of the circuit in response to test inputs in simulation
software. After a successful simulation, we can get the PCB artwork done by replacing
the routing software. The design automation tool used here is ORCAD.

37. 37
5.3 PCB design procedures:
The PCB designing procedure consists of the following steps:
1. Drawing the circuit schematic
2. Design rule check and netlist creation
3. Creating the PCB artwork
4. PCB fabrication
5. Etching
6. Drilling
7. Soldering
5.3.1 Drawing the circuit schematic:
The drawing of the circuit is done through ORCAD CAPTURE. It includes
many libraries with thousands of component symbols. We can select the required
symbol from the library and place it on the schematic page. After placing the component
symbols, we can complete the interconnection using wire or bus control. 18 The next
step is to assign a part reference. Each component has to be assigned a footprint or PCB
pattern name. The footprint gives the actual size physical representation of components
on the PCB artwork. The component symbol and foot symbol should correspond in all
respects.

38. 38
Fig 5.1 Schematic Diagram
5.3.2 Designrule check and netlist creation:
After the circuit schematic is completed with all required information such as
part reference and footprints, the design rule check can be used for checking errors in
the design. It will check for duplicate symbols, overlapped lines, and dangling lines.
After the schematic design file passes the DRC check, it is processed by a
program called an electric rule checker (ERC) that checks for writing errors. The final
operation to be done before starting PCB artwork is the netlist creation.
A netlist creation of the components and interconnection along with other
information such as footprints, track width, etc. A netlist software or tool can take the
circuit schematic as input and generate a netlist. The netlist can be used as an
information source for the remaining stages.

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5.3.3 Creating the PCB artwork:
In automatic design, the netlist obtained from the previous stage is used for
getting the required footprint and interconnections. The software used for the PCB
artwork design in the ORCAD LAYOUT.
5.3.4 PCB fabrication:
You need to generate a positive (copper black) UV translucent artwork film.
You will never get a good board without good artwork, so it is important to get the
best possible quality at this stage. The most important thing is to get a clear sharp
image with a very solid opaque black. The artwork is done using ORCAD software. It
is absolutely essential that your PCB software prints holes in the middle of pads,
which will act as center marks when drilling.
It is virtually impossible to accurately hand-drill boards without these holes.
If you are looking to buy PCB software at any cost level and want to do hand-
prototyping of boards before production, check that this facility is available when
defining pad and line shapes, the 19 minimum size recommended (through-linking
holes) for reliable result is 50 mil, assuming 0.8mm drill size; 1 mil=(1/1000)th of an
inch. You can go smaller drill sizes, but linking will be harder. 65mil round or square
pads for normal components.
ICs, with 0.8 mm hole, will allow a 12.5mil, down to 10mil if you really need
to. The center-to-center spacing of 12.5 mil tracks should be 25 mil-slightly less may
be possible if your printer can manage it. Take care to preserve the correct diagonal
track-track spacing on mitered corners; the grid is 25mil and track width 12.5mil. The
artwork must be printed such that the printed side is in contact with the PCB surface
when exposing, to avoid blurred edges.

40. 40
In practice, this means that if you design the board as seen from the
component side, the bottom (solder side) layer should be printed the „correct‟ way
round, and the top side of the double-sided board must be printed mirrored.
5.3.5 Etching:
Ferric chloride etchant is messy stuff, but easily available and cheaper than most
alternatives. It attacks any metal including stainless steel. So when setting up a PCB
etching area, use a plastic or ceramic sink, with plastic fitting and screws wherever
possible, and seal any metal screws with silicon. Copper water pipes may be splashed
or dripped-on, so sleeve or cover them in plastic; heat-shrink sleeve is great if you are
installing new pipes.
Fume extraction is not normally required, although a cover over the tank or tray
when not in use is a good idea. You should always use the hex hydrate type of ferric
chloride, which should be dissolved in warm water until saturation. Adding a teaspoon
of table salt helps to make the etchant clearer for easier inspection. Avoid anhydrous
ferric chloride. It creates a lot of heat when dissolved. So always add the powder very
slowly to water; do not add water to the powder, and use gloves and safety glasses.
The solution made from anhydrous ferric chloride doesn’t etch at all, so you
need to add a small amount of hydrochloric acid and leave it for a day or two. Always
take extreme care to avoid splashing when dissolving either type of ferric chloride, acid
tends to clump together and you often get big chunks coming out of the container and
splashing into the solution.
It can damage eyes and permanently stain clothing. If you are making PCBs in
a professional environment where time is money you should get a heated bubble-etch
tank. With fresh hot ferric chloride, the PCB will etch in well under 5 minutes. Fast

41. 41
etching produces better edge-quality and consistent line widths. If you aren’t using a 20
bubble tank, you need to agitate frequently to ensure even etching. Warm the etchant
by putting the etching tray inside a larger tray filled with boiling water.
5.3.6 Drilling:
If you have fiberglass (FR4) board, you must use tungsten carbide drill bits.
Fiberglass eats normal high-speed steel (HSS) bits very rapidly, although HSS drills
are alright for older larger sizes (> 2mm). Carbide drill bits are available as straight-
shank or thick-shank. In straight shank, the whole bit is the diameter of the hole, and in
the thick shank, a standard size (typically about 3.5 mm) shank tapers down to the hole
size. The straight-shank drills are usually preferred because they break less easily and
are usually cheaper.
The long thin section provides more flexibility. Small drills for PCB use usually
come with either a set of collets of various sizes or a three-jaw chuck. Sometimes the
3-jaw chuck is an optional extra and is worth getting for the time it saves on changing
collets. For accuracy, however, 3-jaw chucks are not brilliant, and small drill sizes
below 1 mm quickly formed grooves in the jaws, preventing good grip. Below 1 mm,
you should use collets, and buy a few extra of the smallest ones; keeping one collect
per drill size as using a larger drill in a collet will open it out and it no longer grips
smaller drills well. You need a good strong light on the board when drilling, to ensure
accuracy.
A dichroic halogen lamp, underrun at 9V to reduce brightness, can be mounted
on a microphone gooseneck for easy positioning. It can be useful to raise the working
surface above 15 cm above the normal desk height for more comfortable viewing. Dust
extraction is nice, but not essential and occasional blow does the trick! A foot-pedal
control to switch the drill “off” and “on” is very convenient, especially when frequently

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changing bits. Avoid hole sizes less than 0.8 mm unless you really need them. When
making two identical boards, drill them both together to save time.
To do this, carefully drill a 0.8 mm hole in the pad near each corner of each of
the two boards, getting the center as accurately as possible. For larger boards, drill a
hole near the center of each side as well. Lay the boards on the top of each other and
insert a 0.8 mm track pin in two opposite corners, using the pins as pegs to line the
PCBs up. Squeeze or hammer the pins into boards, and then into the remaining holes.
The two PCBs are now nailed together accurately and can be drilled together.
5.3.7 Soldering:
Soldering is the joining together of two metals to give physical bonding and
good electrical conductivity. It is used primarily in electrical and electronic circuitry.
Solder is a combination of metals, which are solid at normal room temperatures and
become liquid between 180 and 200 degrees Celsius.
Solder bonds well to various metals, and extremely well to copper. Soldering is
a necessary skill you need to learn to successfully build electronics circuits. To solder,
you need a soldering iron. A modern basic electrical soldering iron consists of a heating
element, a soldering bit (often called a tip), a handle and a power cord. The heating
element can be either a resistance wire wound around a ceramic tube or a thick film
resistance element printed on to a ceramic base.
The element is then insulated and placed into a metal tube for strength and
protection. This is then thermally insulated from the handle. The heating element of
soldering iron usually reaches temperatures of around 370 to 400 degrees Celsius
(higher than need to melt the solder). The strength or power of a soldering iron is usually

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expressed in watts. Irons generally used in electronics are typically in the range of 12
to 25 watts. Higher powered iron will not run hotter. Most irons are available in a variety
of voltages; 12V, 24V, 115V and 230V are most popular. Today most laboratories and
repair shops use soldering irons, which operate at 24V. You should always use this low
voltage where possible, as it is much safer.
For advanced soldering work, you will need a soldering iron with temperature
control. In this type of soldering irons, the temperature may be usually set between 200
and 450 degrees Celsius. Many temperature control soldering irons designed for
electronics have a power rating of around 40 to 50 watt. They will heat fast and give
enough power for operation but are mechanically small.
You will occasionally see gas-powered soldering irons that use butane rather
than the main electrical supply to operate. They have a catalytic element that once
warmed up, continues to glow hot when gas passes over them. Gas-powered soldering
irons are designed for occasional “on the spot” used for quick repairs, rather than for
mainstream construction or for assembly work.
Currently, the best commonly available, workable, and safe solder alloy is
63/37. That is 63% lead, 37% tin. It is also known as eutectic solder. Its most desirable
characteristic is that it solids („pasty‟) state and its liquid state occur at the same
temperature -361 degree 22 Fahrenheit. The combination of 63% lead and 37% tin
melts at the lowest possible temperature.
Nowadays there is a tendency to move to use lead-free solders, but it will take
years until they catch on normal soldering work. Lead-free solders are nowadays
available, but they are generally more expensive or harder to work on than traditional
solders that they have lead in them. The metals involved are not the only things to
consider in a solder. Flux is vital to a good solder joint.

44. 44
Flux is an aggressive chemical that removes oxide and impurities from the parts
to be soldered. The chemical reactions at the point(s) of the connection must take place
for the metal to fuse. RMA type flux (Rosin Mildly Active) is the least corrosive of the
readily available materials and provides an adequate oxide. In electronics, a 60/40 fixed
core solder is used. This consists of 60% lead and 40% tin, with flux cores added to the
length of the solder. There are certain safety measures which you should keep in mind
when soldering.
The tin material used in soldering contains dangerous substances like lead (40-
60% of typical soldering tins are lead and lead is poisonous). Also, the various fumes
from the soldering flux can be dangerous. While it is true that lead does not vaporize at
the temperature at which soldering is typically done. When soldering, keep the room
well ventilated and use a small fan or fume trap. A proper fume trap of a fan will keep
the most pollution away from your face.
Professional electronic workshops use expensive fume extraction systems to
protect their workers. Those fume extraction devices have a special filter that filters out
dangerous fumes. If you can connect a duct to the output from the trap to the outside,
that would be great. Always wash hands prior to smoking, eating, drinking or going to
the bathroom. When you handle soldering tin, your hands will pick up the lead, which
needs to be washed out from it before it gets to your body. Do not eat, drink or smoke
while working with soldering iron. Do not place cups, glasses or a plate of food near
your working area.

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Fig 5.2 PCB Layout of Li-Fi

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CHAPTER 6
COMPARISON OF LI-FI & WI-FI
Li-Fi is a term used to describe visible light communication technology applied
to high-speed wireless communication. It acquired this name due to the similarity to
Wi-Fi, only using light instead of the radio. Wi-Fi is great for general wireless coverage
within buildings, and Li-Fi is ideal for high-density wireless data coverage in confined
areas and for relieving radio interference issues, so the two technologies can be
considered complimentary.
Table 6.1 Li-Fi Vs Wi-Fi

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Table 6.2 Comparison between current and future wireless
Technology
The table also contains the current wireless technologies that can be used for
transferring data between devices today, i.e. Wi-Fi, Bluetooth, and IrDA. Only Wi-Fi
currently offers very high data rates. The IEEE 802.11.n in most implementations
provides up to 150Mbit/s (in theory the standard can go to 600Mbit/s) although in
practice you receive considerably less than this. Note that one out of three of these is
an optical technology.

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CHAPTER 7
RESULT
7.1 Result:
In our project, we designed and implemented a wireless communication device
which Transmits Audio Message wirelessly known as LIGHT FIDELITY (Li-Fi). The
project contains two sections 1 – Transmitter Section and 2 – Receiver Section. The
transmitter section Modulate the incoming message audio signal and transmit towards
the receiver in the form Visible Light using LEDs. The receiver section interprets the
incoming light which is detected using a solar panel and converts to the audible sound
signal with the help of Speaker.
Fig 7.1 Result

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CHAPTER 8
CONCLUSION
8.1 Advantages:
Li-Fi technology is based on LEDs or other light sources for the transfer of data.
The transfer of the data can be with the help of all kinds of light, no matter the part of
the spectrum that they belong to. That is, the light can belong to the invisible, ultraviolet
or the visible part of the spectrum. Also, the speed of communication is more than
sufficient for downloading movies, games, music and all in very little time. Also, Li-Fi
removes the limitations that have been put on the user by the Wi-Fi.
8.1.1 Capacity:
Light has 400 times wider bandwidth than radio waves. Also, light sources are already
installed. So, Li-Fi has got better capacity and also the infrastructures are already
available.
8.1.2 Efficiency:
Data transmission using Li-Fi is very cheap. LED lights consume less energy
and are highly efficient and long-lasting.

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8.1.3 Availability:
Availability is not an issue as light sources are present everywhere. There are
billions of light bulbs worldwide, They just need to be replaced with LEDs for proper
transmission of data.
8.1.4 Security:
Light waves do not penetrate through walls. So, they can„t be intercepted and
misused.
8.1.5 No Limit for Connectivity:
The High-speed capability of Li-Fi enables a large number of users can be
connected since the speed will not be throttled or slowed down.
8.2 Applications:
There are numerous applications of this technology, from public internet access
through street lamps to auto-piloted cars that communicate through their headlights.
Applications of Li-Fi can extend in areas where the Wi-Fi technology lacks its presence
like medical technology, power plants, and various other areas. Since Li-Fi uses just
the light, it can be used safely in aircraft and hospitals where Wi-Fi is banned because
they are prone to interfere with the radio waves. All the street lamps can be transferred

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to Li-Fi lamps to transfer data. As a result of it, it will be possible to access the internet
at any public place and street. Some of the future applications of Li-Fi are as follows
8.2.1 Education Systems:
Li-Fi is the latest technology that can provide the fastest speed of internet
access. So, it can replace Wi-Fi at educational institutions and at companies so that all
the people can make use of Li-Fi at the same speed intended in a particular area.
8.2.2 Medical Applications:
Operation theatres (OTs) do not allow Wi-Fi due to radiation concerns. The
usage of Wi-Fi at hospitals interferes with the Mobile and PC which blocks the signals
for monitoring equipment. So, it may be hazardous to the patient's health. To overcome
this and to make OTtech-savvy LiFi can be used to accessing the internet and to control
medical types of equipment. This can even be beneficial for robotic surgeries and other
automated procedures.
8.2.3 Cheaper Internet In Aircraft:
The passengers traveling in aircraft get access to low-speed internet at a very
high rate. Also, Wi-Fi is not used because it may interfere with the navigational systems
of the pilots. In aircrafts, Li-Fi can be used for data transmission. Li-Fi can easily
provide high-speed internet via every light source such as overhead reading bulb, etc.
present inside the airplane.

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8.2.4 Underwater Applications:
Underwater ROVs (Remotely Operated Vehicles) operate from large cables
that supply their power and allow them to receive signals from their pilots above. But
the tether used in ROVs is not long enough to allow them to explore larger areas. If
their wires were replaced with light say from a submerged, high-powered lamp then
they would be much freer to explore. They could also use their headlamps to
communicate with each other, processing data autonomously and sending their findings
periodically back to the surface. Li-Fi can even work underwater where Wi-Fi fails
completely, thereby throwing open endless opportunities for military operations.
8.2.5 Disaster Management:
Li-Fi can be used as a powerful means of communication in times of disaster
such as earthquakes or hurricanes. The average people may not know the protocols
during such disasters. Subway stations and tunnels, common dead zones for most
emergency communications, pose no obstruction for Li-Fi. Also, for normal periods,
Li-Fi bulbs could provide cheap high-speed Web access to every street corner.
8.2.6 Applications In Sensitive Areas:
Power plants need fast, interconnected data systems so that demand, grid
integrity and core temperature (in case of nuclear power plants) can be monitored. Wi-
Fi and many other radiation types are bad for sensitive areas surrounding the power
plants. Li-Fi could offer safe, abundant connectivity for all areas of these sensitive
locations. This can save money as compared to the currently implemented solutions.
Also, the pressure on a power plant„s own reserves could be lessened. Li-Fi can also be
used in petroleum or chemical plants where other transmission or frequencies could be
hazardous.

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8.2.7 Traffic Management:
In traffic signals, Li-Fi can be used which will communicate with the LED
lights of the cars which can help in managing the traffic in a better manner and the
accident numbers can be decreased. Also, LED car lights can alert drivers when other
vehicles are too close. 5.3.8 REPLACEMENT FOR OTHER TECHNOLOGIES Li-Fi
doesn’t work using radio waves. So, it can be easily used in places where Bluetooth,
infrared, Wi-Fi, etc. are banned.
8.2.8 Replacement For Other Technologies:
Li-Fi doesn’t work using radio waves. So, it can be easily used in places where
Bluetooth, infrared, Wi-Fi, etc. are banned.
8.3 Conclusion:
This technology is still under research and surely it will be a breakthrough in
communication. It assures data speed of100gbps which is entirely greater than radio
waves. The scope of this Li-Fi technology is ultimately greater. As Li-Fi provides
secured, low cost, easy data transmission and provides reliable communication, It can
be used in industrial, medical, military applications. Li-Fi is still in its beginning stages,
but improvements are being made rapidly, and soon this technology will be able to be
used in our daily lives. It is intended that this research will provide the starting steps for
further study. In spite of the research problems, it is our belief that the VLC system will
become one of the most promising technologies for the future generation in optical
wireless communication.

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The possibilities are numerous and can be explored further. If his technology
can be put into practical use, every bulb can be used something like a Wi-Fi hotspot to
transmit wireless data and we will proceed toward the cleaner, greener, safer and
brighter future. The concept of Li-Fi is currently attracting a great deal of interest, not
least because it may offer a genuine and very efficient alternative to radio-based
wireless. As a growing number of people and their many devices access wireless
internet, the airwaves are becoming increasingly clogged, making it more and more
difficult to get a reliable, high-speed signal. This may solve issues such as the shortage
of radio-frequency bandwidth and also allow the internet where traditional radio-based
wireless isn’t allowed such as aircraft or hospitals. The main shortcoming, however, is
that it only works in a direct line of sight.
8.4 Future Scope:
Li-Fi is an emerging technology and hence it has vast potential. A lot of research
can be conducted in this field. Already, a lot of scientists are involved in extensive
research in this field. This technology, pioneered by Harald Haas, can become one of
the major technologies in the near future. If this technology can be used efficiently, we
might soon have something of the kind of WI-FI hotspots wherever a light bulb is
available. As the amount of available bandwidth is limited, the airwaves are becoming
increasingly clogged, making it more and more difficult to get a reliable, highspeed
signal. Li-Fi technology can solve this crisis.
Moreover, it will allow inter access in places such as operation theatres and
aircraft where internet access is usually not allowed. The future of Li-Fi is Gi-Fi. Gi-Fi
or gigabit wireless refers to wireless communication at a data rate of more than one
billion bits (gigabit) per second. In 2008researchers at the University of Melbourne
demonstrated a transceiver integrated on a single integrated circuit (chip) that operated
at 60 GHz on the CMOS process. It will allow wireless transfer of audio and video data

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at up to 5 gigabits per second, ten times the current maximum wireless transfer rate, at
one-tenth the cost.
Researchers chose the 57–64 GHz unlicensed frequency band since the
millimeter-wave range of the spectrum allowed high component on-chip integration as
well as the integration of very small high gain arrays. The available 7 GHz of spectrum
results in very high data rates, up to 5 gigabits per second to users within an indoor
environment, usually within a range of 10 meters. Some press reports called this "Gi-
Fi". It was developed by Melbourne University-based laboratories of NICTA (National
ICT Australia.

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REFERENCES
[1] http://en.wikipedia.org/wiki/Li-Fi
[2] www.YouTube.com – TED Talk by Harald Hass on Li-Fi
[3] “Li-Fi (Light Fidelity)-The future technology In Wireless
communication?” by Jyoti Rani. “Journal from International Journal of
Applied Engineering Research” (IJAER); ISSN 0973-4562 Vol.7 No.11
(2012)
[4] www.lificonsortium.org/
[5] Priyanka Dixit and Kunal Lala – Li-Fi the Latest Technology in
Wireless; ISBN 978817515738
[6] https://circuitdigest.com/
[7] Google Images