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BIRZEIT UNIVERSITY

 FACULTY OF ENGINEERING AND TECHNOLOGY  

ELECTRICAL AND COMPUTER SYSTEMS ENGINEERING DEPARTMENT

IMPLEMENTATION OF A SIMPLE LI-FI SYSTEM

Prepared by

Mohammad Awad

Rasheed Amira

Mohannad Abu Shanab

Supervised by

Mr. Nofal Nofal

Graduation Project Submitted to the Electrical

Engineering Department in Partial Fulfillment of the Requirements for the

Degree of B.Sc. in Electrical Engineering

BIRZEIT

April -2016

Table of Contents

Introduction 1

Chapter One: Architecture of a simple Li-Fi System: 2

1.1 Introduction 2

1.2 Overview of Li-Fi Transmitters...........................................................................................2

1.3 Overview of Li-Fi Receiver 3

    1.4 Data Sourse..........................................................................................................3

Chapter Two: Implementation Li-Fi Transmitters: 4

2.1 Introduction 4

2.2 Hardware connection of Li-fi Transmitters: 4

2.3 RDL-UNO ATmega 328 6

2.4 FT232 BreakOut Board: 7

Chapter Three: Implementation of the Li-Fi Receivers: 9

3.1: Introduction 9

3.2: The hardware connection of Li-Fi receiver and its function 10

Chapter 3: Conclusion and Results 11

Refrences 12

Appendix A 13

Introduction

The studies provide that Li-Fi system has a great speed, higher data rate,safer, and simple configuration compared to Wi-Fi system. But these studies need a practical model to ensure that the theoretical studies can be implemented and able to use wherever it placed. To implement this system we are going to design a simple Li-Fi system that depends on the basic concept of Li-Fi which is the Visible Light Communication (VLC).The design producer will be done by two steps, the first one is to design a prototype model that provide the basic concept, and the second one will be a small system which uses this concept to transmit a text from one device to another.

Chapter Tow: Li-Fi Hardware

2.1 Introduction

As shown in figure 1.1, Li-Fi system consists of two main parts which are transmitter and receiver. The transmitter consists of led lamp and micro-controller which are connected to the PC. A receiving device named photo detector is used to receive a signal and to process it, this device can be connected with PC port. On one end, the data from the PC converted to digital data. when the LED is switched on the microchip converts the digital data in form of light. The light sensitive device photo detector receives the signal and converts it back into original data form. This method of using rapid pulses of light to transmit information wirelessly is technically referred

 as Visible Light Communication .

                   

 Figure 2.1: Architecture of a Simple  Li-Fi System

2.2 Text Massage Hardware Description

The hardware consists of two main parts which is transmitter and receiver. The transmitter is a part of the Li-Fi communication system. It consists of the input data, Micro-controller, and a LED lamp. The input data is text. This data will be modulated by the micro-controller and the Li-Fi TX kit. On other side, Receiver is another part of the Li-Fi communication system. It consists of a receiving device which is called photo-detector and  micro-controller . They are  used for receiving signal and processing it. The data will be demodulated by the micro-controller and the Li-Fi RX kit.

2.2.1 RDL-UNO ATmega 328

ATmega 328 is one of the most commonly used Micro controllers with open source platform amongst many hobbyist and industrial communities. The simplicity and the low power of ATmega 328 helps design many prototype boards which could be used in numerous applications. We introduced RDL UNO ATmega 328 development board having common UNO interface to the available shields. The board also has inbuilt Xbee footprint with memory card interface in a single compact board without the need of doing external connections and hence as a whole the final product becomes cost effective. The RDL UNO ATmega 328 also includes 6 analog inputs, 14 digital I/O pins (6 amongst these could be used as PWM outputs), a crystal oscillator with 16 MHz frequency, a 5 pin female connector to connect FT232 plugin, a power jack, a reset button and an ICSP header. This board does not have an inbuilt USB to directly load the program from the computer. As we all know, once the program has been dumped into the board, the part of the USB connectors become useless. So to load the program we have given common interface through FT232 breakthrough board where we can connect to a computer and load the codes into the RDL UNO ATmega 328. Since the USB interface has been removed, we have provided Xbee foot print and Micro SD card slot which is commonly used by many electronics enthusiasts. Once the program has been dumped into the RDL UNO ATmega 328 we can remove the FT232 plugin and could be used independently for other purposes. This board is fully compatible with Arduino like open source software. Figure 2.4 shows the Atmega board.

                                                       Figure 2.2:Atmega Board

2.2.2  FT232 BreakOut Board

It's a common high speed IC used to convert USB to serial converter. It's quite commonly used to connect a microcontroller TTL data to any USB interface host to establish a bridge for communications between USB to serial devices. This particular breakthrough board can be used to program RDL UNO ATMEGA 328 and use directly in to your own circuits. Also this breakthrough board can also act as a bridge between Xbee and its Xbee utility software to configure various Xbee's. Figure 2.5 shows the FT232 BreakOut Board.

 

Figure 2.3 : FT232 BreakOut Board.

2.2.3 Li-Fi TX

Transmitter of the Li-Fi consists of the input data, Processing unit , and a LED panel. The input data which comes from the data source will be processed by Processing unit, after that it will passed through LED lamp to the receiver of the system via free space. The transmitter of the system is shown in figure 2.4.

Figure 2.4: Transmitter of the Li-Fi System

The main function of the Li-Fi transmitter is to modulate the data in an appropriate form so that the receiver will receive this data and handle it , till it  will be completely recovered by the receiver. The transmitter will be connected to array of LED which is shown in figure 2.5.

Figure 2.5: Array of LED

This array is considered the source of the light which will carry the data form the sending end to the receiver end.The connection between the transmitter and the array of LED is shown in figure 2.6.By the end of this process the data will flow in the space until the data hit the surface of the photodetector which is the first stage in the demodulation process.

Figure 2.6: The Connection between Transmitter and the Array of LED

Features of the LED panel :

' 9x9 LED Matrix

' Easy expandable  connectors for 9x9 LED matrix in all four direction

' constant current driven

' Supply voltage 12 to 15V

' High Brightness

' Long life

' Low Power Consumption

2.2.3 Li-Fi RX

Receivers are another part of the Li-Fi communication system. It consists of a receiving device named photodiode. It is used for receiving the signal and processing it. This device is connected with PC. Figure 2.7 shows the receiver of the system.

Figure 2.7: Li-Fi Receiver

Receiver can receive data with 38400 baud rate serially. The Distance which can be achieved is 1 Feet to 10 Feet for wireless open optical communication.

2.3  Hardware Connection of Li-Fi Transmitter and Receiver

2.4 Live Voice Hardware Description

In this part, the main components used are mini-solar panel, transformer, light source and voice source Instead of using microphone to transmit  sound wave to the laptop and hear it , a mini-solar cell was used which is sensitive to the light. So, at the moment of connecting the solar cell, sound will be hear due to the static current that comes from light sources. The computer can Deal with the static current well and remove it. Live voice circuit works using amplitude modulation, exactly like AM radio, except using a visible light wavelength instead of a radio frequency. The audio signal leaves the iPhone  as a varying voltage which forces a varying current through the laser. Then the laser's varying brightness conveys the musical information. Finally, the solar cell  varies in voltage  as the brightness on it changes. The mic amp applies a small voltage to the solar cell which is connected to the PC, then the PC amplifies the resulting current and removes the static current, then we obtained that voltage as sound.A problem with this system is that at each step there is a non-linear transfer function, that is, there is distortion that occurs because the brightness changes are not always proportional to the change in voltage applied. The hardware connection of the live voice circuit  is shown in figure 2.8.

2.5 File Transfer Hardware Description

 We are trying to transmit data via the medium of laser. Basically the data to be transmitted is obtained in digital format then the voltage is varied (high or low) with certain frequency across the laser diode according to 1 or 0(low for 0 and high for 1). A photo diode is used to sense the high and low on the receiver side along with a clock of the same frequency. This is free space, line of sight, serial data transmission method. The steps of data processing are shown in figure 2.9.

Figure 2.9: Data Processing

2.5.1 Arduino

Arduino is an open-source physical computing platform based on a simple microcontroller board, and a development environment for writing software for the board. Arduino can be used to develop interactive objects, taking inputs from a variety of switches or sensors, and controlling a variety of lights, motors, and other physical outputs or they can communicate with software running on your computer. The Arduino programming language is an implementation of wiring, in other words the programmer writs a code about a citrine object on his/her computer which is connected to the microcontroller platforms by a USB port, after running the code the microcontroller will give specific outputs. Arduino also simplifies the process of working with microcontrollers ,the following are some benefits of using Arduino:

- inexpensive: Arduino boards are relatively inexpensive compared to other    

    microcontroller platforms.

- Simple, clear programming environment : The Arduino programming environment

   is easy-to-use for beginners, yet flexible enough for advanced users to take

   advantage of as well.   

- Available for anyone to use since it's an open source.

Figure 2.10: Arduino Structure

In this part two Arduino boards were be used, one at the transmitter and the other at the receiver. The one at the transmitter is used to make interface between the first laptop and the laser by transferring the data (from the laptop) in the form of zeros and ones, in the way if a digital zero is transferred there will be no voltage given to the LEDs. If a digital one is transferred a 5 volts will be given to the laser. The other one is used at the receiver, which reads the output and convert it to zeros and ones.

2.5.2 Photodiode

The photodiode used is GaAsP photodiode. It is a photosensor with suppressed sensitivity in the long wavelength range compared to Si photodiodes. It has spectral response close to the human eye sensitivity and is suitable for spectrophotometry, color sensing, etc. It is sensitive to the red light only and has Low dark current. moreover, it has High stability. Figure 2.11 shows the GaAsp photodiode.

Figure 2.11: GaAsp Photodiode

2.5.3 Problem Faced and it's Solutions

2.5.3 Keyes laser

1.4 Data Source

The main source of data for this simple system will be the string (Text) data from laptops. These data can be in different forms, in general it will be a string data, then it will be converted to digital data.

'

'

Chapter Three :Implementation of the Li-Fi Receivers:

3.1: Introduction

Chapter 3: Conclusion and Results

The design procedures of the prototype were done, but this prototype won't be used. However instead of using this prototype, an educational components of a Li-Fi transmitter and receiver were bought. This components are capableto modulate and demodulate the data, transmitting it, and receiving it. The test of this model will be done in the next few weeks, the test depends on choose a type of the data transmission such transmitting a text from one end to another end. If this test will pass without any problems, we're going to try to transmit a photo or a video from one sending end device to receiving end device.

References

1.AmanSodhi, Jeslin Johnson, Light Fidelity (LI-FI) - The Future of Visible Light Communication, International Journal of Engineering Research and General Science, Volume 3, Issue 2, ISSN 2091-2730 , (2015).

2. LIFI Communication DIY Kit

 http://researchdesignlab.com/diy-kits/lifi-communication-diy-kit-atmel. html# product _tabs _description_tabbed .Retrieved April. 2016.

3. FT232 BreakOut Board

http://researchdesignlab.com/ft232-shield.html. Retrieved April. 2016.

'

Appendix A

Codes

1-Transmitter code:

char rec;

void setup()

{

Serial.begin(38400); // initialize the serial communications

}

void loop()

{

Serial.write("hello");

}

2-Receiver Code:

void setup() {

Serial.begin(38400);

delay(20);

}

void loop() {

if (Serial.available())

Serial.write(Serial.read());

}

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