-***Sorry if it"s totally unreadable it's my first inscrutable so be kind lol ***_
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 phones subscriptions in recent times. This has been causing a rapid reduction in 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 that are more eco-friendly compare to RF use more simple circuit and light the room which can in the same time save money and energy by Counterflix .
Li-Fi stands for Light-Fidelity. Li-Fi is 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 photo detector 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 Giga bits per second which is much faster than our average broadband connection.
Step 1: Grab Your COMPONENTS and Material
The main advantage of Led over laser transmission is that led are more simple and they don't need much components .
The Basic Components of the Circuits :
- Power Supply (5V Supply) and (12V Supply for the LED)
- Capacitors (470uf , 2*10nf, 20nf )
- Resistors (1k,10k variable )
- NE555 IC
-Transistor (tip122) ( or a mosfet )
- Potentiometer (Change the frequency of the oscillator)
- Light Source – 1W LED (or Three led In series)
The basic Components of the Receiver Circuits are:
· Photo Detector – Solar cell
· Speaker 4 ohm 1 w
· Capacitor (100 uf, 2*1000 uf , 0.1 uf )
· Resistance (10k)
· Variable Resistance (50 k)
· 9v battery or any other power supply (between 5v and 15v)
Soldring iron ,pcb ,hot glue gun.....etc
Step 2: TRANSMITTER CIRCUIT :
CIRCUIT WORKING :
In The Ne555 there in pin 5 a VCO a voltage Controlled Oscillator which basically Turn the amplitude of the sine wave into the width of the pulse as it’s shown in the oscilloscope:
The Capacitors C3, C4 are filters to reduce AC components spike in circuit..
The width of the pulse wave is controlled by The resistor RV1 by changing the value of the resistance we change the time charging and discharging the capacitor and btw changing the time the pulse stay high and low so it changes the time of on/off signal in the output pin 3,lower the resistance value the higher frequency will be modulated in the output .
The Pulse signal is equivalent to the ON/OFF Signal in the Output pin 3 which control the intensity of the Light Source LED (D1)(D2)(D3).
The Pulse wave is further Amplified and Modulated using Transistor TIP121 (T1)(it's a darling-tone transistor but using mosfet is more efficient ) , which is an Amplifier Modulator having high current gain. The transistor will act as a Lamp Driver and drives the LED. LED emits light according to the pulse wave form and make lifi (Light-Fidelity )
For the project we know that the human ear can only hear between 100 hz – 20khz so we are using the carrier frequency wave above 20 khz or above and by the way only hear the Audio source input in receiver circuit .
Step 3: RECEIVER CIRCUIT:
CIRCUIT WORKING :
The Solar cell is used to detect the Light from the Transmitting LEDs. And reproduces
an Analog output corresponding to the input signal.
The frequency of the analog will be same as that of input signal, since the flickering of LED is controlled by the input signal and solar cell detects only the fluctuation in the LED signal and produces the output.
The output is then amplified using TDA22. It also helps in removing any phase changes occurs in the transmitted signal. And then filtered to remove any other light room about 60hz high pass filter The Amplified signal is fed to the speaker.
The speaker converts the analog signal to the Audible Sound signal using the electromagnet present in the Speaker.
Step 4: Soldering on Pcb :
1 Transmitter Soldering :
I Just wanted to make it look like a light- bulb , so i cut the pcb to fit in the light bulb shape , then implement all the component and start soldering according to the schismatic
2 - Receiver soldering:
.Did not do anything special just solder .
There you have it it's finish xd :)
If you want more details you can read the word file ( .docx ) .
By using Li-Fi we can have Energy saving Parallelism. With growing number of people and their many devices access wireless internet, on one way data transfer at high speed and at cheap cost. In future we can have LED array beside a motorway helping to light the road, displaying the latest traffic updates and transmitting internet information to wirelessly to passengers Laptops, Notebooks and Smart phones. This is the kind of extra ordinary, energy saving parallelism that is believed to deliver by this pioneering technology.