LI-FI(LIGHT FIDELITY)
BASED HIGH DATA RATE VISIBLE LIGHT COMMUNICATION FOR DATA AND AUDIO
TRANSMISSION
ABSTRACT
Li-Fi
stands for Light-Fidelity. The technology is very new and was proposed by the
German physicist Harald Haas in 2011. Li-Fi provides transmission of data
through illumination by sending data through a LED light bulb that varies in
intensity faster than human eye can follow. In this , we will discuss the
technology in detail and also how Wi-Fi can be replaced by Li-Fi. Wi-Fi is
useful for general wireless coverage within buildings while Li-Fi is ideal for
high density wireless data coverage in confined areas where there are no
obstacles. Li-Fi is a wireless optical networking technology that uses light
emitting diodes (LEDs) for transmission of data. The term Li-Fi refers to
visible light communication (VLC) technology that uses as medium to deliver
high-speed communication in a manner similar to Wi-Fi. Li-Fi provides better
bandwidth, efficiency, availability and security than Wi-Fi and has already
achieved high speeds in the lab. Li-Fi is a data transfer technique that uses light. Light is
analogous not only to illumination but also to speed. Li-Fi is also much
secured since light cannot pass through walls. It uses visible light portion of
the electromagnetic spectrum to transmit information. Hence the visible light
communication solves the problem of radio frequency congestion. In this project
we transmit data and audio through light at very high data rates without use of
microcontrollers and its other peripheral devices.
INTRODUCTION
Li-Fi, a short form for Light Fidelity, is a wireless technology that
makes use of visible light communication instead of radio waves. In this,
common household LED bulbs can be utilised to allow data transfer with a speed
of up to 224 gigabits per second, which equates to downloading around 18 movies
each of 1.5 GB in every single second.
This term was coined by Professor Harald Haas during a TED TALK in
the year 2011. Basically, with this technology, people will be able to use
light bulbs and solar cells as wireless routers for transmitting data. He even
set up a company named pureLiFi in 2012 and aims to be the world leader in
Visible Light Communications technology.
A simple LiFi circuit is presented
here for school and college final year projects showing how to transmit music
through LED light across a given distance, using only LED light without
creating any fluctuations in the LED and yet transferring the light with perfection. Light Fidelity (Li-Fi) is a
bidirectional, high-speed and fully networked wireless communication technology
similar to Wi-Fi. Li-Fi is the term some have used to label the fast and cheap
wireless communication system, which is the optical version of Wi-Fi. Li-Fi
uses visible light instead of Gigahertz radio waves for data transfer.
LIFI (light
fidelity) is data through
illumination-taking he fiber out of fiber optics by sending data through an LED light bulb that
varies in intensity faster than the human eye can notice.
At the heart of this technology is a new generation of high brightness LED's.
If the LED is on a digital 1 is transmitted, if the LED is off then a digital 0 is transmitted.
They can be switched on
and off in order to transmit data continuously.
CIRCUIT DIAGRAM
COMPONENT
1. light-emitting diode (LED):-
LED is a semiconductor light
source that emits light when current flows through it. When a
current flows through the diode, electrons are able to recombine
with electron holes within the device, releasing energy in the form
of photons. This effect is called electroencephalogram. The color of
the light (corresponding to the energy of the photons) is determined by the energy band
gap of the semiconductor. White light is obtained by using multiple
semiconductors or a layer of light-emitting phosphor on the
semiconductor device. Parts of a conventional LED. The flat bottom surfaces of
the anvil and post embedded inside the epoxy-act as anchors, to prevent the conductors from
being forcefully pulled out via mechanical strain or-vibration.
Figure : Led
2.Solar :- Solar-powered photovoltaic (PV) panels convert the
sun's rays into electricity by exciting electrons in silicon cells
using the photons of light fromthe sun. This electricity can then be
used to supply renewable energy to yourhome or business.Solar
cells can be used to generate electricity from sunlight. It is a device
thatconverts light energy into electrical energy. Sometimes the term
solar cell isreserved for devices intended specifically to capture energy from
sunlight, whilethe term photovoltaic cell is used when the light
source is unspecified.
Figure : Solar Plate
3.Speaker:- An audio
amplifier is an electronic device that increases the strength (amplitude)
of audio signals that pass through it. An audio
amplifier amplifies low-power audio signals to a level which is
suitable for driving loudspeakers.
Figure :- Speaker
4. Capacitor:-A capacitor can store electric energy when it is connected to its
charging circuit. And when it is disconnected from its charging circuit, it can
dissipate that stored energy, so it can be used like a temporary battery.
Capacitors are commonly used in electronic devices to maintain power supply
while batteries are being changed.
Figure
:- Capacitor
5. 3.5MM Jack Cable:- An audio
signal is a representation of sound, typically as an electrical voltage
for analog signals and a binary number for digital
signals. Audio signals have frequencies in
the audio frequency range of roughly 20 to 20,000 Hz (the limits of human
hearing).
Figure :- 3.5mm Jack
6.Resistor:- it is an electrical
device may be a passive two-terminal electrical part that implements resistance
as a circuit component. In electronic circuits, resistors unit of measurement
accustomed reduce current flow, alter signal levels, to divide voltages, bias active
components, and terminate transmission lines, among completely different uses.
Figure
:- Resistor
7. Battery :-
An electric battery is a device
consisting of one or more electrochemical cells with external
connections provided to power electrical devices such as flashlights, and electric
cars. When a battery is supplying electric power, its positive terminal
is the cathode and its negative terminal is the anode. The
terminal marked negative is the source of electrons that will flow through an
external electric circuit to thepositive terminal. When a battery is connected
to an external electric load.
Figure :-
Battery
8. Wire:-
A length
of such material, consisting either of a single filament or of several
filaments woven or twisted together and usually insulated with a dielectric
material, used as a conductor of electricity.
Figure:- Wire
MUSIC CIRCUIT
This project is about
making a 5 Watt stereo audio amplifier using the UTC TEA2025 IC chip.
Figure :-
Music Circuit
Figure :- IC
Diagram
TEUTC TEA2025 is a monolithic
integrated audio amplifier IC in a 16-pin plastic dual in line package. It is
originally designed for portable cassette players and radios, but it can be
used to make a pretty decent stereo audio amplifier for an ipod or mp3 player.
It requires very few external components and can run on as low as 3 V power
supply. The pin diagram of TEA2025 and the application circuit for stereo
application are shown below.
An interesting characteristic of TEA2025 is it has built-in
thermal protection circuit. If you want to run it at its full capacity (5 W),
you should provide a heat sink in the circuit. In case you don’t, the internal
thermal protection won’t let the device damage; all that happens is that the
output power is reduced when an excessive junction temperature is sensed.
At the input stage, a logarithmic dual taper potentiometer (10
or 20 K) can be used to provide the volume control feature. The 0.22 µF
capacitors at the input side help to minimize any noise due to variable resistor
contact. The 0.15 µF capacitors at the output end are for frequency stability.
Use of other value capacitors could result in unwanted oscillations at the
output. Long wire connections and ground loops in the circuit could also cause
oscillations,so a good layout of the circuit PCB is very important. I built
this circuit on a 5 cm x 9 cm general purpose prototyping circuit board as
shown below. The circuit is put inside a 6 cm x 11 cm size plastic enclosure
and necessary connections (power supply, speaker, and stereo input terminals)
are drawn out of the box.The circuit can be powered from 3-12 V power supply. I
am powering this with my spare 9.6V rechargeable battery from my broken RC toy.
I am happy with the performance of TEA2025 as an stereo audio amplifier.
COMPONENT USING MUSIC CIRCUIT
1. Capacitor:- capacitor is a little like a battery. Although
they work in completely different ways, capacitors and batteries both store
electrical energy. If you have read How Batteries Work, then you know
that a battery has two terminals. Inside the battery, chemical reactions
produce electrons on one terminal and absorb electrons on
the other terminal. A
capacitor is much simpler than a battery, as it can't produce new electrons --
it only stores them. Inside the capacitor, the terminals connect to
two metal plates separated
by a non-conducting substance,or dielectric. You can easily make a
capacitor from two pieces of aluminum foil and a piece of paper. It won't be a
particularly good capacitor in terms of its storage capacity, but it will work.
Figure
:-Capacitor
2.
TEA2025 IC:- The UTC TEA2025 is a monolithic integrated
audio amplifier IC in a 16-pin plastic dual in line package. It is originally
designed for portable cassette players and radios, but it can be used to make a
pretty decent stereo audio amplifier for an ipod or mp3 player. It requires
very few external components and can run on as low as 3 V power supply. The pin
diagram of TEA2025 and the application circuit for stereo application are shown
below.
Figure :- IC
Diagram
3. Speaker:- A speaker is a term used to
describe the user who is giving vocal commands to a software program. Speakers
are made up of a cone, an iron coil, a magnet, and housing (case). When the
speaker receives electrical input from a device, it sends the current through
the causing it to move back and forth. This motion then vibrates the outer
cone, generating sound waves picked up by our ears.
Figure :-
speaker
4. Resistance:- The resistor is a passive
electrical component to create resistance in the flow of electric current. In
almost all electrical networks and electronic circuits they can be found. The
resistance is measured in ohms. An ohm is the resistance that occurs when a
current of one ampere passes through a resistor with a one volt drop across its
terminals. The current is proportional to the voltage across the terminal ends.
This ratio is represented by Ohm’s law:
Resistors are used for many purposes. A few examples
include delimit electric current, voltage division, heat generation, matching
and loading circuits, control gain, and fix time constants. They are
commercially available with resistance values over a range of more than nine
orders of magnitude. They can be used to as electric brakes to dissipate
kinetic energy from trains, or be smaller than a square millimeter for electronics
Figure :-
Resistor
WORKING
Li-Fi and Wi-Fi are quite similar as both transmit data
electromagnetically. However, Wi-Fi uses radio waves, while Li-Fi runs on
visible light waves.As we now know, Li-Fi is a Visible Light Communications
(VLC) system. This means that it accommodates a photo-detector to receive light
signals and a signal processing element to convert the data into 'stream able'
content.An LED light bulb is a semiconductor light source meaning that the
constant current of electricity supplied to an LED light bulb can be dipped and
dimmed, up and down at extremely high speeds, without being visible to the
human eye.
For example, data is fed into an LED light bulb (with signal
processing technology), it then sends data (embedded in its beam) at rapid
speeds to the photo-detector (photodiode).The tiny change in the rapid dimming
of LED bulbs is then converted by the 'receiver' into electrical signal. The
signal is then converted back into a binary data stream that we would recognize
as web, video and audio applications that run on internet-enabled devices.
EFFICIENCY:-
The current system
is high on energy consumption.
For every unit of
energy consumed the data
transmitted is relatively less.
The data speeds in
the current system can
only reach up to a few hundreds of megabits per second.
BENEFITS:-
Security:-
In contrast to radio
frequency waves used by Wi-Fi, lights cannot penetrate through walls and
doors. This makes it more secure and makes it easier to control access to a
network As long as transparent materials like windows are covered,
access to a Li-Fi channel is limited to devices inside the room.
Underwater application:-
Most remotely operated
underwater vehicles (ROVs) are controlled by wired connections. The length
of their cabling places a hard limit on their operational range, and other
potential factors such as the cable's weight and fragility may be restrictive.
Since light can travel through water, Li-Fi based communications could offer
much greater mobility. Li-Fi's utility is limited by the distance light
can penetrate water. Significant amounts of light do not penetrate further than
200 meters. Past 1000 meters, no light penetrates.
Hospital:-
Many treatments now involve
multiple individuals, Li-Fi systems could be a better system to transmit
communication about the information of patients. Besides providing a
higher speed, light waves also have little effect on medical
instruments and human bodies.
Vehicles:-
Vehicles could
communicate with one another via front and back lights to increase road safety.
Street lights and traffic signals could also provide information about current
road situations.
Industrial automation:-
Anywhere in industrial areas data has to be
transmitted, Li-Fi is capable of replacing slip rings, sliding
contacts and short cables, such as Industrial Ethernet. Due to the
real time capability of Li-Fi (which is often required for automation
processes) it is also an alternative to common industrial Wireless LAN standards.
Speed:-
Li-Fi can possibly deliver data transfer speeds of 224 gigabits per
second which clearly leaves Wi-Fi far behind. As per the tests conducted by
pureLiFi, the technology produced over 100 Gbps in a controlled environment.
Moreover, the visible light spectrum is 1,000 times larger than the 300 GHz of
RF spectrum which helps in gaining high speed.
Energy Efficiency:-
Usually, Wi-Fi needs two radios to communicate back and forth which
takes a lot of energy to discern the signal from the noise as there may be
several devices using the same frequency. Each device has an RF transmitter and
base band chip for enabling communication. However, as Li-Fi uses LED lights,
the transmission requires minimal additional power for enabling communication.
Data Density:-
Owing to the interference issues, Wi-Fi works in a less dense
environment while Li-Fi works in a highly dense environment. The area covered
by one Wi-Fi access point has 10s or 100s of lights and each LiFi light can
deliver the same speed or greater than a Wi-Fi access point. Therefore, in the
same area, LiFi can provide 10, or 100, or 1000 times greater wireless
capacity.
CONCLUSION:-
The concept of Li-Fi is currently attracting a great deal of interest,
not least because it may offer a genuine and efficient alternative to radio
based wireless. As a growing number of people and their devices access wireless
internet, the air waves are becoming increasingly clogged, making it more and
more difficult to get a reliable, high-speed signal. So Li-Fi has a bright
future. LI FI will make are lives
more technology driven in the near future.With its magic of light it can make
our world a greener, safer, cleaner and more over a brighter place to live.
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