laser commn - short report

7/26/2019 Laser Commn - Short Report

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ABSTRACT

Communication is the important and vital action that every living being onthis earth does. At present we have fiber optic communication that is the most

proffered means of communication. All telephones broadband use fiber optic.

Here we are going to talk about a wireless laser link that could be used to

transmit information from one end to another in its line of sight. Laser voice

communication is a wireless communication that replaces the present fiber optic

communication and gives us the greatest advantage of infinite distance wireless

communication. The laser beam here is used as a carrier, which is modulated by

the signal to be transmitted. On the receiver end the desired signal is separatedfrom the carrier. Wireless laser communication links are very popular in space

applications for providing inters satellite communication.


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CONTENTS

1.

INTRODUCTION

2.

BLOCK DIAGRAM

3.

BLOCK DIAGRAM EXPLANATION

4.

WORKING

5.

CIRCUIT DIAGRAM

6.

CIRCUIT DIAGRAM EXPLANATION


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INTRODUCTION

Light Amplification by Stimulated Emission of Radiation (LASER or laser) is amechanism for emitting electromagnetic radiation, often visible light, via the

process of stimulated emission. The emitted laser light is (usually) a spatially

coherent,narrow low-divergence beam that can be manipulated with lenses. In

laser technology, "coherent light" denotes a light source that produces (emits)

light of in-step waves of identical frequency, phase, and polarization. The laser's

beam of coherent light differentiates it from light sources that emit incoherent

light beams, of random phase varying with time and position. Laser light is

generally a narrow-wavelength electromagnetic spectrum monochromatic light;yet, there are lasers that emit a broad spectrum of light, or emit different

wavelengths of light simultaneously.

This project is to take communication to the

next economic level, which is very much needed for the present scenario.
http://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Visible_lighthttp://en.wikipedia.org/wiki/Stimulated_emissionhttp://en.wikipedia.org/wiki/Coherence_(physics)http://en.wikipedia.org/wiki/Beam_divergencehttp://en.wikipedia.org/wiki/Phase_(waves)http://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Electromagnetic_spectrumhttp://en.wikipedia.org/wiki/Electromagnetic_spectrumhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Phase_(waves)http://en.wikipedia.org/wiki/Beam_divergencehttp://en.wikipedia.org/wiki/Coherence_(physics)http://en.wikipedia.org/wiki/Stimulated_emissionhttp://en.wikipedia.org/wiki/Visible_lighthttp://en.wikipedia.org/wiki/Electromagnetic_radiation


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BLOCK DIAGRAM

TRANSMITTER

MIC SWITCHING

CIRCUITS

VISUAL

INDICATION

LASER DIODE

9V

BATTERY

ON/OFF

SWITCH


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RECEIVER

PHOTO

TRANSISTOR AMPLIFIER

AUDIO

FREQUENCY

AMPLIFIER

LOUD

SPEAKER

GAIN

CONTROL


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BLOCK DIAGRAM EXPLANATION

Transmitter section:

MIC

Condenser microphone is used as the sound sensor. A microphone is an

acoustic to electric transducer orsensor that converts sound into an electric

signal. Here the sound signals that has to be transmitter is sensed with the help of

the mic.

AMPLIFIER

Generally, an amplifier or simply amp is any device that changes, usually

increases, the amplitude of a signal.Here sound is measured by the condenser

microphone; it convertssound into anelectrical signal. This output electrical

signals are difficult to measure due to their relatively low voltage (in the range of

millivolts). In order to detect a particular signal accurately, it should requires

amplification. Therefore an amplifier is necessary to boost the size of the signal.

SWITCHING CIRCUITS

The transistor based switching circuit is used here. The output from the

amplifier section is given to the laser torch via the switching circuit.

VISUAL INDICATIONS

The LEDs are used here as visual indicators. A light-emitting diode (LED) is a

semiconductor light source. LEDs are used as indicator lamps in many devices,

and are increasingly used for lighting. Introduced as a practical electronic

component in 1962, early LEDs emitted low-intensity red light, but modern

versions are available across thevisible,ultraviolet andinfrared wavelengths, with

very high brightness.
http://en.wikipedia.org/wiki/Sensorhttp://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Signal_(electrical_engineering)http://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Electrical_signalhttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Lightinghttp://en.wikipedia.org/wiki/Visible_spectrumhttp://en.wikipedia.org/wiki/Ultraviolethttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Ultraviolethttp://en.wikipedia.org/wiki/Visible_spectrumhttp://en.wikipedia.org/wiki/Lightinghttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Electrical_signalhttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Signal_(electrical_engineering)http://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Sensor


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LASER DIODE

Laser is of prime importance in Optical memories, Fiber optic

communications, Military applications, Surgical procedures, CD players, Printers

etc. Various forms of lasers like Gallium Arsenide laser, Helium Neon laser, Carbondioxide laser etc are used in various applications. Laser light is Monochromatic

and can be focused as a pencil beam. The LASER diode sends the modulated beam

to the receiver.

Receiver section:

PHOTOTRANSISTOR

The phototransistor is a semiconductor light sensor formed from a basic

transistor with a transparent cover that provides much better sensitivity. The

brightness of the light shining on the phototransistors base (B) terminal

determines how much current it will allow to pass into its collector (C) terminal,

and out through its emitter (E) terminal. Brighter light results in more current;

less-bright light results in less current. The phototransistor senses the light from

the laser diode.

AMPLIFIER

This amplifier section comprises of a transistor based two staged preamplifier.

GAIN CONTROL

The gain of the system is controlled with the help of a preset. The preset can

be varied in order to control the input given to the AF amplifier

AUDIO FREQUENCY AMPLIFIER

Audio Frequency (AF) amplifier helps in supplying AF (Audio Frequency)

power to operate the loud speaker, hand piece or other output device.


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LOUD SPEAKER

A loudspeaker (or "speaker") is an electro acoustictransducer 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 amedium such as air or water.
http://en.wikipedia.org/wiki/Transducerhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Signal_processinghttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Signal_processinghttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Transducer


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WORKING

Transmitter Section:

The transmitter section comprises a condenser microphone, switching

circuits and laser diode. The microphone receives the sound signal and converts

into the equivalent electrical signal. This electrical signal is then passed through

the switching circuits. Switching circuit include a transistor amplifier and an op-

amp circuit. Modulated laser beam is obtained at the output of switching circuit.

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 transmitter uses 9V

power supply.

Receiver Section:

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 receiver circuit uses a

phototransistor as the light sensor, which converts the received light energy into

an equivalent electrical energy that is followed by a two-stage transistorpreamplifier and an audio power amplifier. The electrical energy after proper

signal conditioning, it is fed to the loudspeaker. The loudspeaker converts the

electrical energy into equivalent sound energy. Thus sound is transmitted from

one end to another end.

The receiver does not need any complicated alignment. Just keep the

phototransistor oriented towards the remote transmitters laser point and adjust

the volume control for a clear sound.


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CIRCUIT DIAGRAM

TRANSMITTER


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RECEIVER


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CIRCUIT DIAGRAM EXPLANATION

TRANSMITTER SECTION

The transmitter section includes the microphone, the switching circuits, the

amplifier and the laser diode. Here we use a condenser mic to sense the sound

signals and convert to electrical signals. These signals are then fed to a transistor

based amplifier section. This is further given to an op-amp based amplifier

section. UA 741 is used as the op-amp. The gain of the inverting amplifier can be

controlled with the help of the feedback resistance i.e. 1M preset. The capacitors

C1 & C2 act as coupling capacitors. The amplified output is given to the laser torch

via BD139 transistor. This power transistor is used to drive the laser torch. The AFoutput from IC1 is coupled to the base of transistor BD139 (T2), which, in turn,

modulates the laser beam.

COMPONENT DETAILS

Condenser Microphones

Condenser microphone uses a capacitor toconvert acoustical energy into electrical energy. It

requires power from a battery or external source. The

resulting audio signal is stronger signal than that from a

dynamic. Condensers also tend to be more sensitive

and responsive than dynamics, making them well-

suited to capturing subtle nuances in a sound. They are

not ideal for high-volume work, as their sensitivity

makes them prone to distort. Working of this device isas follows.

A capacitor has two plates with a voltage between them. In the condenser

MIC, one of these plates is made of very light material and acts as the diaphragm.

The diaphragm vibrates when struck by sound waves, changing the distance


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between the two plates and therefore changing the capacitance. Specifically,

when the plates are closer together, capacitance increases and a charge current

occurs. When the plates are further apart, capacitance decreases and a discharge

current occurs.

A voltage is required across the capacitor for this to work. This voltage is supplied

either by a battery in the MIC or by externalphantom power.

BC548

This device is designed for use as general purpose

amplifiers and switches requiring collector currents

to 300 mA.

Features:

NPN general purpose

TO-92 package

Small signal

Applications:

Switching

Small signal amplification

Low power
http://www.mediacollege.com/audio/phantom-power/http://www.mediacollege.com/audio/phantom-power/


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LM741

General Description

The LM741 series are general purpose operational amplifiers which featureimproved performance over industry standards like the LM709. They are direct,

plug-in replacements for the 709C, LM201, MC1439 and 748 in most applications.

The amplifiers offer many features which make their application nearly foolproof:

overload protection on the input and output, no latch-up when the common

mode range is exceeded, as well as freedom from oscillations. The

LM741C/LM741E are identical to the LM741/LM741A except that the

LM741C/LM741E have their performance guaranteed over a 0C to +70C

temperature range, instead of 55C to +125C.

BD139

Features:

High current (max. 1.5 A)

Low voltage (max. 80 V)

Applications:

Driver stages in hi-fi amplifiers and

television circuits.


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DESCRIPTION

NPN power transistor in a TO-126; SOT32 plastic package. PNP complements:

BD136, BD138 and BD140.

LASER DIODE

Light Amplification by Stimulated Emission of

Radiation (LASER or laser) is a mechanism for emitting

electromagnetic radiation, often visible light, via theprocess of stimulated emission. The emitted laser

light is (usually) a spatially coherent, narrow low-

divergence beam, that can be manipulated with

lenses.In laser technology, "coherent light" denotes a

light source that produces (emits) light of in-step
http://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Visible_lighthttp://en.wikipedia.org/wiki/Stimulated_emissionhttp://en.wikipedia.org/wiki/Coherence_(physics)http://en.wikipedia.org/wiki/Beam_divergencehttp://en.wikipedia.org/wiki/Beam_divergencehttp://en.wikipedia.org/wiki/Lens_(optics)http://en.wikipedia.org/wiki/Lens_(optics)http://en.wikipedia.org/wiki/Beam_divergencehttp://en.wikipedia.org/wiki/Beam_divergencehttp://en.wikipedia.org/wiki/Coherence_(physics)http://en.wikipedia.org/wiki/Stimulated_emissionhttp://en.wikipedia.org/wiki/Visible_lighthttp://en.wikipedia.org/wiki/Electromagnetic_radiation


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waves of identical frequency, phase, and polarization. The laser's beam of

coherent light differentiates it from light sources that emit incoherent light

beams, of randomphase varying with time and position

Laser light is generally a narrow-wavelength electromagnetic spectrummonochromatic light; yet, there are lasers that emit a broad spectrum of light, or

emit different wavelengths of light simultaneously.

RECEIVER SECTION

The LASER light from the transmitter section is detected with the help of a

phototransistor L14F. The phototransistor conducts when the light from the laser

falls on it. The output from the collector terminal is then interfaced to a two stage

pre amplifier based on BC549 transistor. This section is followed by an audio

amplifier. LM386 op-amp based audio amplifier is used. This amplified signal is

then fed to a loud speaker so that we can hear sound signals ie transmitted from

the transmitter end. The 10k preset is adjusted so that the sound signals become

clear.

L14F

L14F is an NPN phototransistor. It acts as a photodetector in the sense that it can convert the incident light into

electric response. They are commonly used as sensors usually

paired with a light source like LED. These are the bipolar

transistors having a transparent case. This transparent case

exposes the base collector region of transistor to external

light. When light incidents on this junction, electrons are generated by the

photons. These electrons are injected in the base of phototransistor. The current

gain of the transistor amplifies the resulting photocurrent at the base collectorjunction. Thus a phototransistor conducts in the presence of light and remains in

off mode in absence of light. The maximum dark current is 100nA; while in light

its current is 500A.

A phototransistor is different from a simple transistor in the way that in the

latter, voltage applied to the base is replaced by light striking it. Simply put, a
http://en.wikipedia.org/wiki/Phase_(waves)http://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Electromagnetic_spectrumhttp://en.wikipedia.org/wiki/Electromagnetic_spectrumhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Phase_(waves)


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phototransistor amplifies variations in the light striking it. Phototransistors may or

may not have a base terminal. If a base terminal is available, it is used to bias its

light response.

Photodiodes can also be used for similar function as phototransistors, but

they have much lower gain and thus lower photocurrent. Phototransistors cannot

detect low intensities of light but are more responsive to the exposed light. Also,

the transistor response lasts for a longer period as compared to a photodiode.

The required light source is a gallium arsenide LED with peak wavelength is

940 nm. The emitter lead is indicated by a protruding edge in the transistor case.

The base is nearest to the emitter. The collector is at the other extreme side of

the casing.

BC549

DESCRIPTION

NPN transistor in a TO-92; SOT54 plastic package. PNP

complements: BC559 and BC560.

FEATURES

Low current (max. 100 mA) Low voltage (max. 45 V).

APPLICATIONS

Low noise stages in audio frequency equipment.

LM386

Low Voltage Audio Power Amplifier

General Description

The LM386 is a power amplifier designed for use in low

voltage consumer applications. The gain is internally set to 20

to keep external part count low, but the addition of an

external resistor and capacitor between pins 1 and 8 will


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increase the gain to any value up to 200. The inputs are ground referenced while

the output is automatically biased to one half the supply voltage. The quiescent

power drain is only 24 milliwatts when operating from a 6 volt supply, making the

LM386 ideal for battery operation.

Features

Battery operation

Minimum external parts

Wide supply voltage range: 4V12V or 5V18V

Low quiescent current drain: 4 mA

Voltage gains from 20 to 200

Ground referenced input Self-centering output quiescent voltage

Low distortion

Available in 8 pin MSOP package

Applications

AM-FM radio amplifiers

Portable tape player amplifiers

Intercoms

TV sound systems

Line drivers

Ultrasonic drivers

Small servo drivers

Power converters

LOUD SPEAKER

A loudspeaker (or "speaker") is an electro acoustic transducer that converts an

electrical signal intosound.The speaker moves in accordance with the variations
http://en.wikipedia.org/wiki/Transducerhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Signal_processinghttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Signal_processinghttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Transducer


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of an electrical signal and causes sound waves to propagate through a medium

such as air or water

A loudspeaker (or "speaker") is an electro acoustic transducer that converts an

electrical signal intosound.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

The loudspeakers are almost always the limiting element on the fidelity of a

reproduced sound in either home or theater. The other stages in sound

reproduction are mostly electronic, and the electronic components are highly

developed. The loudspeaker involves electromechanical processes where the

amplified audio signal must move a cone or other mechanical device to produce

sound like the original sound wave. This process involves many difficulties, and

usually is the most imperfect of the steps in sound reproduction. Choose yourspeakers carefully. Some basic ideas about speaker enclosures might help with

perspective.
http://en.wikipedia.org/wiki/Transducerhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Signal_processinghttp://en.wikipedia.org/wiki/Soundhttp://www.google.co.in/imgres?imgurl=http://www.iconicspkrs.com/images/165_8g.jpg&imgrefurl=http://www.iconicspkrs.com/basshorndrivers.html&usg=__uS2orXxBy8vPjFMcMTawhBd0F-s=&h=1426&w=1906&sz=204&hl=en&start=8&tbnid=JkmemO1ZqUP9yM:&tbnh=112&tbnw=150&prev=/images?q=loudspeaker&um=1&hl=en&rlz=1R2SUNC_enIN374&tbs=isch:1&um=1&itbs=1http://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Signal_processinghttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Transducer

laser commn - short report

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