NORTHERN INDIA ENGINEERING COLLEGE MINOR PROJECT REPORT ON “LASER TORCH-BASED VOICE TRANSMITTER AND RECEIVER” Submitted in accordance with the curriculum requirements for seventh semester of the degree course in BACHELOR OF TECHNOLOGY In the branch of ELECTRICAL & ELECTRONICS ENGINEERING of UNIVERSITY OF GGSIPU YEAR 2015
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NORTHERN INDIA ENGINEERING COLLEGE
MINOR PROJECT REPORT
ON
“LASER TORCH-BASED VOICE
TRANSMITTER AND RECEIVER”
Submitted in accordance with the curriculum requirements for
seventh semester of the degree course in
BACHELOR OF TECHNOLOGYIn the branch of
ELECTRICAL & ELECTRONICS ENGINEERING
of
UNIVERSITY OF GGSIPU
YEAR 2015
NORTHERN INDIA ENGINEERING COLLEGE
CERTIFICATE
This is to certify that this mini project entitled
Laser torch based voice transmitter and reciver has been completed by
Praveen kumar, Mohan Rathor, Honey Dabas, Vikrant
Choudhary & Poorvesh during
Seventh semester in partial fulfillment of the award of the degree in BACHELOR
OF TECHNOLOGY IN ELECTRICAL & ELECTRONICS
ENGINEERING of GGSIPU UNIVERSITY during the academic year 2013-
2016.
Project guide Staff in charge Head of the Department
ACKNOWLEDGEMENT
To bring something into existence is truly the work of ALMIGHTY. We thank
GOD ALMIGHTY for making this venture a success.
We express our wholehearted thanks to the Management of the college, Mr.
Akhilesh Das Gupta, Chairman, for providing us an opportunity to do our
studies in this esteemed institution. We thank our HOD, Prof. Ajit Kr Sharma
for providing the facilities for our studies and constant encouragement in all
achievements.
At the outset we wish to place on record our sincere thanks to quite a few people
without whose help, this venture would not have been a success.
we extend my deep gratitude to my project guides Mrs Amruta Patnaik and Mr
Vikasdeep for their guidance, timely advice and support rendered during all stages
of the project work. We express our whole hearted gratitude to them.
We express our thanks to to EEE staff and lab technicians during the course of this
work.
We convey our thanks to our parents and friends who have directly or
indirectly helped us in the successful completion of the project.
CONTENTS1.Abstract
2.Introduction
3. Block Diagram
4. Block Diagram Description
5.Circuit Diagram
6.Working of Circuit Diagram
7.Component List
8.Component Description
9.Circuit Description
i.Trasmitter
ii reciver
10.component layout
11.Soldering
12.Advantages
13.Application
14.Conclusion
15.References
1.ABSTRACT
Using this circuit we can communicate with your neighbors wirelessly. Instead of
RF signals, light from a laser torch is used as the carrier in the circuit. The laser
torch can transmit light up to a distance of about 500 meters. The phototransistor of
the receiver must be accurately oriented towards the laser beam from the torch. If
there is any obstruction in the path of the laser beam, no sound will be heard from
the receiver. The transmitter circuit comprises condenser microphone transistor
amplifier BC548 followed by an pomp stage built around µA741. The gain of the
op-amp can be controlled with the help of 1-mega-ohm potmeter VR1.The AF
output from IC1 is coupled to the base of transistor BD139 (T2), which, in turn,
modulates the laser beam.
The transmitter uses 9V power supply. However, the 3-volt laser torch (after
removal of its battery) can be directly connected to the circuit—with the body of
The torch connected to the emitter of BD139 and the spring-loaded lead protruding
from inside the torch to circuit ground. The receiver circuit uses an npn
phototransistor as the light sensor that is followed by a two-stage transistor
preamplifier and LM386-based audio Power amplifier. The receiver does not need
any complicated alignment. Just keep the phototransistor oriented towards the
remote transmitter’s laser point and adjust The volume control for a clear sound.
To avoid 50Hz hum noise in the speaker, keep the phototransistor away from AC
light sources such as bulbs. The reflected sunlight, however, does not cause any
problem. But the sensor should not directly face the sun.
2. INTRODUCTION
Laser as a communication medium can provide a good substitute for the present
day communication systems as the problem of interference faced in case of
electromagnetic waves is not there and high deal of secrecy is available.
Use of laser in communication systems is the future because of the advantages of
the full channel speeds, no communication licenses required at present,
compatibility with copper or fiber interfaces and no bridge or router requirements .
Besides this there are no recurring line costs, portability, transparency to networks
or protocols, although range is limited to a few hundred meters. Also the laser
transmission is very secure because it has a narrow beam (any potential
evesdropping will result in an interruption which will alert the personnel. Also it
cannot be detected with use of spectrum analyzers and RF meters and hence can be
used for diverse applications including financial, medical and military. Lasers can
also transmit through glass, however the physical properties of the glass have to be
considered. Laser transmitter and receiver units ensure easy, straightforward
systems alignment and long-term stable, servicefree operation, especially in
inaccessible environments, optical wireless systems offer ideal, economical
alternative to expensive leased lines for buildings. The laser can also be
commissioned in satellites for communication, as laser radar requires small
aperture as compared to microwave radar. Also there is high secrecy and no
interference like in EM waves. Further, potential bandwidth of radar using lasers
can translate to very precision range measurement. For these reasons, they can be
used as an alternative to present modes of communication. laser communication,
which is both wide-band and high-speed .
3.BLOCK DIAGRAM
MIC
Transmitting
Section
Laser
Torch
Receivin
g
section
Loud
speaker
4.BLOCK DIAGRAM EXPLANATION
i.CONDENSER MICROPHONE :
It is also called a capacitor or electrostatic microphone. Condenser
means capacitor, which stores energy in the form of an electric field. Condenser
microphones require power from a battery or external source. Condenser also tends
to be more sensitive and responsive than dynamic, making them well suited to
capturing subtle nuances in a sound.
The diaphragm vibrates when struck by sound waves, changing the distance
between the two plates and therefore changing the capacitance. Specifically when
the plates are closer together capacitance increases and a charge current occurs and
this current will be used to trigger the transmitting section.
ii. TRANSMITTING SECTION :
The transmitter section comprises condenser microphone, transistor
amplifier BC548 followed by an op-amp stage built around IC1.
The gain of the op-amp can be controlled with the help of 1-mega ohm
pot meter VR1. The AF output from IC1 is coupled to the base of
transistor Bd139, which in turn, modulates the laser beam. The
transmitter uses 9V power supply. however, the 3-volt laser torch ( after
the removal of its battery) can be directly connected to the circuit--with
the body of the torch connected to the emitter of BD139 and the spring-
loaded lead protruding from inside the torch to circuit ground.
iii. LASER TORCH :
Here we use the light rays coming from laser torch as the medium for
transmission. Laser had potential for the transfer of data at extremely high rates,
specific advancements were needed in component performance and systems
engineering, particularly for space-qualified hardware. Free space laser
communications systems are wireless connections through the atmosphere. They
work similar to fibre optic cable systems except the beam is transmitted through
open space. The laser systems operate in the near infrared region of the spectrum.
The laser light across the link is at a wavelength of between 780 - 920 nm. Two
parallel beams are used, one for transmission and one for reception.
vi. RECEIVING SECTION :
The receiver circuit uses an NPN phototransistor as the light sensor that is followed
by a two stage transistor preamplifier and LM386-based audio power amplifier.
The receiver doesn't need any complicated alignment. Just keep the phototransistor
oriented towards the remote transmitter's laser point and adjust the volume control
for a clear sound.
v. LOUD SPEAKER
Aloudspeaker (or "speaker") is an electro acoustic transducer that converts an
electrical signal into sound. The speaker moves in accordance with the variations
of an electrical signal and causes sound waves to propagate through a medium such
as air or water.
5. Circuit Diagram
Transmitter
Reciver
R1= 100k ohm C2= 0.1 uf
R2= 1M ohm C3= 100uf 25V Electrolytic
R3= 10k pot U1= 741 op amp
C1= 0.1 uf U2= LM 386 aud amp
Q1= NPN photo transistor
6. Working of Circuit Diagram
Transmitter: The mic is the audio input. C1 is a coupling capacitor that connects the audio from
the mic to T1. T1 is a transistor that is used to amplify the audio a bit. C2 couples
the audio to IC1 which amplifies it some more. The audio from the IC is then
routed to T2 which modulates the power to the LED. This puts the audio onto the
light beam. VR1 is a variable resistor which adjusts the gain of the IC. C3, C4 and
R7 are power filters that remove noise from the power supply. The other resistors
Just supply the right voltage to the various parts.
Receiver:T3 is a photo sensitive transistor which receives the laser from the LED
transmitter. The transistor puts out a signal that is proportional to the light from the
LED. This not only receives the signal it also demodulates it. C5 couples this audio
to T4 and T5 which amplify the signal. The signal is them coupled through C8 to
VR2. VR2 is a volume control for IC2. IC2 amplifies the signal more and drives