synopsos vlc

8/10/2019 Synopsos Vlc

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SAMRAT ASHOK TECHNOLOGICAL

INSTITUTE ,VIDISHA(M.P.)

“Visible Light Communication System”

Guided By: Prepaired By:

Prof. Neelesh Mehra Ayush Jain

Prof. Abhishek Jain Devendra Chauhan

Shivkumar Chouhan

Manohar Kumawat



1.INTRODUCTION

The circuit shows an example of visible light communication(VLC) i.e. the transmission of information using visible light.Using this

circuit we can transmit audio and video data by modulating it and

transmitting the modulated signal with the help of simple LEDs and

receiving the signal using photodiodes or phototransistors in the

range where visible light is reachable.

2.CIRCUIT DIAGRAM

The implementation of VLC can be done using the following circuit.

Fig.1 Audio Transmission Using Visible Light

The alternative arrangement of transmitter and receiver can be

shown in following two circuits.



Fig.2 Alternative Way of Implementing VLC With Filtering At

Receiver

3.CIRCUIT DESCRIPTION

The above circuit shows the audio link that can be used to transmit

signals up to 4 meters.In fig. 1 the signal to be transmitted is applied

to the base of Q1 via resistor R4.The transistor Q1 drives the

transmitting diodes D1 and D2.The audio input will be modulated to



the visible light signals transmitted.

The transmitted visible light signals will be picked by the photo

transistor Q2.The emitter voltage of the transistor Q2 will change

according to the sound modulated to the IR signal. The transistors Q3

and Q4 amplifies this signal to drive the speaker or headphone.C1

and R3 forms a filter to avoid interference from stray light signals.

Notes:

The circuit can be assembled on a general purpose PCB.

We use 9V PP3 batteries for powering the transmitter and

receiver.

The phototransistor Q2 can be any NPN phototransistor likePNZ154, PNA1605F, BPW77NA or BPW85.We have used

2N5777 as phototransistor.

An 8 Ohm speaker or a headphone can be used to hear the

sound.

4.APPLICATIONS

As in this field we are dealing with VLC which is a subcategory of

Free Space Optics(FSO) with having the light of wavelength 400nm

to 700nm.We will use VLC for downlink and Visible Light or IR for

uplink.

1. The infrastructure used for the cloud access(PSTN & ADSL) can be

entirely replaced with the cable wire used for electricity.

2. A new,effective and efficient technology Li-Fi can be implemented

for internet.Using this technology the cost of Communication can be

decreased up to 10 times.

3. Today’s wireless technology is promiscuous and less secure

because it can penetrate the walls.The VLC system is more secure for



local use because the transmission of data will only be wherever the

light is reaching.

5.LIMITATIONS AND FURTHER MODIFICATIONS

Since the visible light can interfere with the environmental light

during the process of modulation and demodulation which will cause

an erroneous and noisy output.Also the presence of obstacle in

communication path is not acceptable and it may cause decrement

in data rate and for the data of low amplitude can be completely lostif a rigid obstacle comes into the path.

For the above limitations we can modify the

circuit by using IR as the uplink at transmitter.Also for the faithful

demodulation multiple LEDs can be used with feedback path for the

approximation of signal from its previous input if any obstacle comes

into the path.

synopsos vlc

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