CHAPTER 1

INTRODUCTION

1.1 MOTIVATION: An undirected IR free-space communications system is presented which achieves a range in excess of that typically attributed to systems based on diffuse IR radiation. Several papers have described free space optical communications based on diffuse radiation (undirected) techniques and point-to point (directed) techniques. Few have described a compromise system, such as the one discussed here, which achieves coverage over a wide area with an array of line-of-sight IR links, though are examples of papers that discuss this idea. The diffuse IR system described in gives an experimental range of 10-20 meter. The system described here is shown to be capable of a practical range of greater than 10 meter in an indoor environment and greater than 12 meter outdoors in sunlight. The present system is useful in an environment where the ceiling is too high and the walls are too far apart to support practical transmission by diffuse radiation, and where a moderate range and moderate to high data rate are required over a wide coverage area. This type of environment exists, for example, in office buildings, ware houses, shopping malls, airports and at anywhere outdoors.

1.2 OBJECTIVE: The main idea behind the project is to generate musical notes by infrared radiations. The infrared radiations are transmitted and received by IR LED and Phototransistor respectively.

This project emphasizes the way by which music is generated and driven by IR rays. This circuit uses a popular melody generator IC UM66 that can continuously generate musical notes. The melody produced is heard through the receiver’s loudspeaker. For maximum sound transmission the IR LEDs should be oriented towards IR phototransistor.

Using this circuit, audio musical notes can be generated and can be heard up to a distance of 10 meters. The receiver can be placed at a maximum distance of 1 meter from the transmitter without any considerable noise interference. The circuits of transmitter and receiver are quite simple and can be placed and carried any where easily. The small apparatus provided with the infrared communication function is in many cases operated by a battery incorporated inside so that it is convenient when a user carries it during movement, and it is preferable that power consumption be minimized also to lengthen the continuous operation possible time of IR emission is optimized. Here there is no use of any modulation techniques when working with IR rays. Hence there is no necessity of carrier generation. This makes the transmitter and receiver designs much simpler. However the communication distance can be improved by using Far IR LEDs. The range of communication can be increased to about 250 meters by using far IR LEDs. In the apparatus provided with a conventional communication function, however, the infrared

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light with a constant intensity is constantly radiated regardless of the communication distance. This project emphasizes the way by which music is generated and driven by IR rays and gives an explanation to the one of the methods of receiving IR rays without considerable noise interference.

1.3 WHAT IS INFRARED COMMUNICATION?

Light Comparison

Name Wavelength Frequency (Hz) Photon Energy (eV)

Gamma ray less than 0.01 nm more than 10 EHZ 100 keV - 300+ GeV

X-Ray 0.01 nm to 10 nm 30 EHz - 30 PHZ 120 eV to 120 keV

Ultraviolet 10 nm - 390 nm 30 PHZ - 790 THz 3 eV to 124 eV

Visible 390 nm - 750 nm 790 THz - 405 THz 1.7 eV - 3.3 eV

Infrared 750 nm - 1 mm 405 THz - 300 GHz 1.24 meV - 1.7 eV

Microwave 1 mm - 1 meter 300 GHz - 300 MHz 1.24 µeV - 1.24 meV

Radio 1 mm - 100,000 km 300 GHz - 3 Hz 12.4 feV - 1.24 meV

Table 1.1 : Frequencies Range for different EM waves

Infrared (IR) light is electromagnetic radiation with longer wavelengths than those of visible light, extending from the nominal red edge of the visible spectrum at 0.74 micrometres (µm) to 300 µm. This range of wavelengths corresponds to a frequency range of approximately 1 to 400 THz, and includes most of the thermal radiation emitted by objects near room temperature. Infrared light is emitted or absorbed by molecules when they change their rotational-vibrational movements. The existence of infrared radiation was first discovered in 1800 by astronomer William Herschel.Much of the energy from the Sun arrives on Earth in the form of infrared radiation. Sunlight at zenith provides an irradiance of just over 1 kilowatt per square meter at sea level. Of this energy, 527 watts is infrared radiation, 445 watts is visible light, and 32 watts is ultraviolet radiation. The balance between absorbed and emitted infrared radiation has a critical effect on the Earth's climate.Infrared light is used in industrial, scientific, and medical applications. Night-vision devices using infrared illumination allow people or animals to be observed without the observer being detected. In astronomy, imaging at infrared wavelengths allows observation of objects obscured by interstellar dust. Infrared imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatus.

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1.3.1 Commonly used sub-division:

DivisionName

AbbreviationWavelength

PhotonEnergy

Characteristics

Near-infrared

NIR, IR-A DIN

0.75-1.4 µm

0.9-1.7 eV

Defined by the water absorption, and commonly used in fiber optic telecommunication because of low attenuation losses in the SiO2 glass (silica) medium. Image intensifiers are sensitive to this area of the spectrum. Examples include night vision devices such as night vision goggles.

Short-wavelength infrared

SWIR, IR-B DIN

1.4-3 µm 0.4-0.9 eV

Water absorption increases significantly at 1,450 nm. The 1,530 to 1,560 nm range is the dominant spectral region for long-distance telecommunications.

Mid-wavelength infrared

MWIR, IR-C DIN. Also called intermediate infrared (IIR)

3-8 µm150-400 meV

In guided missile technology the 3-5 µm portion of this band is the atmospheric window in which the homing heads of passive IR 'heat seeking' missiles are designed to work, homing on to the Infrared signature of the target aircraft, typically the jet engine exhaust plume

Long-wavelength infrared

LWIR, IR-C DIN

8–15 µm 80-150 meV

This is the "thermal imaging" region, in which sensors can obtain a completely passive picture of the outside world based on thermal emissions only and requiring no external light or thermal source such as the sun, moon or infrared illuminator.Forward-looking infrared (FLIR) systems use this area of the spectrum. This region is also called the "thermal infrared."

Far infrared FIR15 - 1,000 µm

1.2-80 meV far-infrared laser)

Table 1.2: Different sub divisions of IR frequencies

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1.3.2 Telecommunication bands in the infrared:In optical communications, the part of the infrared spectrum that is used is divided into seven bands based on availability of light sources transmitting/absorbing materials (fibers) and detectors:[12]

Band Descripton Wavelength range

O band Original 1260–1360 nm

E band Extended 1360–1460 nm

S band Short wavelength 1460–1530 nm

C band Conventional 1530–1565 nm

L band Long wavelength 1565–1625 nm

U band Ultra long wavelength 1625–1675 nm

Table 1.3: Classification of IR in communication field

The C-band is the dominant band for long-distance telecommunication networks. The S and L bands are based on less well established technology, and are not as widely deployed.

1.4 WHY IR COMMUNICATION? Infrared imaging is used extensively for military and civilian purposes. Military applications include target acquisition, surveillance, night vision, homing and tracking. Non-military uses include thermal efficiency analysis, environmental monitoring, industrial facility inspections, remote temperature sensing, short-ranged wireless communication, spectroscopy, and weather forecasting. Infrared astronomy uses sensor-equipped telescopes to penetrate dusty regions of space, such as molecular clouds; detect objects such as planets, and to view highly red-shifted objects from the early days of the universe.

Humans at normal body temperature radiate chiefly at wavelengths around 10 μm (micrometers), as shown by Wien's displacement law.

At the atomic level, infrared energy elicits vibrational modes in a moleculethrough a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry.Infrared spectroscopy examines absorption and transmission of photons in the infrared energy range, based on their frequency and intensity.

CHAPTER 2

4

LITERATURE SURVEY

2.1 WHAT IS IR LED? As normal PN junction diode provide current as the output when subjected to forward bias, in the same way an IR led gives IR radiation at its output in forward bias. Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.7 micrometers, and extending conventionally to 300 micrometers. These wavelengths correspond to a frequency range of approximately 430Hz to 1THz, and include most of the thermal radiation emitted by objects near room temperature. Microscopically, IR light is typically emitted or absorbed by molecules when they change their rotational or irrational movements.

2.2 WHAT IS PHOTODIODE? A photodiode is a type of photo detector, capable of converting light into either current or voltage, depending upon the mode of operation. Photodiode works on the principle of photoconductivity. When light is absorbed by a semiconductor material, the number of free electrons and electron’s holes changes and raises its electrical conductivity, this phenomenon is called photoconductivity. To cause excitation, the light that strikes the semiconductor must have enough energy to raise electrons across the band gap Photoconductivity may also be defined as an electrical property of Light Emitting Diode (LED) which is the fact that a LED produces a voltage difference across its leads when it is subjected to light, as if it was in photo-cell, but with much lower output current. In other words, the voltage generated by the LED cannot be, in any way, used to generate electrical power from the output voltage, it can barely be detected. This is why we used an Op-Amp (operational Amplifier) to accurately detect very small voltage changes. Photoconductivity is a phenomenon in which a material becomes more electrically conductive due to the absorption of electromagnetic radiation such as visible light, ultraviolet light, infrared light, or gamma radiation. Photodiodes are similar to regular semiconductor diodes except that they may be either exposed to (detect UV or X-rays) or an optical fiber connection to allow light to reach the sensitive part of the device.

2.3 LIST OF COMPONENTS

5

6

S.No. Name Of The Component Quantity

1. IC UM-66(IC1) 1

2. IC LM741 (IC2) 1

3. IC LM386 (IC3) 1

4. RED LED(1) 1

5. IR LED(2 & 3) 2

6. Resistance R1 & R11 (1 K) 2

7. Resistance R2(4.7 K) 1

8. Resistance R3(22 K) 1

9. Resistance R4(82 ohm) 1

10. Resistance R5 & R12(10 ohm) 2

11. Resistance R6 & R7(10 K) 2

12. Resistance R8 & R13(15 K) 2

13. Resistance R9(100K) 1

14. Resistance R10(680 ohm) 1

15. Capacitor C1(1uF,16V) 1

16. Capacitor C2,C4,C8 & C10(220 uF, 25V) 4

17. Capacitor C3,C5,C7 & C9(0.1 uF) 4

18. Capacitor C6(10 uF,16V) 1

19. Transistor BC547(T1) & SK140/BD140(T2) 2

20. IR Phototransistor L14F1(T3) 1

21. Zener diode 3.3V 1/4W 2

22.

23.

24.

Speaker (8 ohm, 1W)

Preset VR1 (1M) & VR2 (10K)

9V battery

1

2

2

Table 2.1: List of components used

2.4 SPECIFICATION OF COMPONENTS

2.4.1 TRANSISTOR The essential usefulness of a transistor comes from its ability to use a small signal applied between one pair of its terminals to control a much larger signal at another pair of terminals. This property is called gain. A transistor can control its output in proportion to the input signal; that is, it can act as an amplifier. Alternatively, the transistor can be used to turn current on or off in a circuit as an electrically controlled switch, where the amount of current is determined by other circuit elements. There are two types of transistors, which have slight differences in how they are used in a circuit. A bipolar transistor has terminals labeled base,collector, and emitter. A small current at the base terminal (that is, flowing from the base to the emitter) can control or switch a much larger current between the collector and emitter terminals. For a field-effect transistor, the terminals are labeled gate, source, and drain, and a voltage at the gate can control a current between source and drain. The image to the right represents a typical bipolar transistor in a circuit. Charge will flow between emitter and collector terminals depending on the current in the base. Since internally the base and emitter connections behave like a semiconductor diode, a voltage drop develops between base and emitter while the base current exists. The amount of this voltage depends on the material the transistor is made from, and is referred to as VBE.

Transistor as a switch

Fig 2.1 BJT used as an electronic switch, in grounded-emitter configuration.Transistors are commonly used as electronic switches, both for high-power applications such as switched-mode power supplies and for low-power applications such as logic gates. In a grounded-emitter transistor circuit, such as the light-switch circuit shown, as the base voltage rises, the base and collector current rise exponentially. The collector voltage drops because of the collector load resistance (in this example, the resistance of the light bulb). If the collector voltage were zero, the collector current would be limited only by the light bulb resistance and the supply voltage. The transistor is then said to be saturated - it will have a very small voltage from collector to emitter. Providing sufficient base drive current is a key problem in the use of bipolar transistors as switches. The transistor provides current gain, allowing a

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relatively large current in the collector to be switched by a much smaller current into the base terminal. The ratio of these currents varies depending on the type of transistor, and even for a particular type, varies depending on the collector current. In the example light-switch circuit shown, the resistor is chosen to provide enough base current to ensure the transistor will be saturated. In any switching circuit, values of input voltage would be chosen such that the output is either completely off, or completely on. The transistor is acting as a switch, and this type of operation is common in digital circuits where only "on" and "off" values are relevant.

Transistor as an amplifier

Fig 2.2 Amplifier circuit, common-emitter configuration. The common-emitter amplifier is designed so that a small change in voltage (Vin) changes the small current through the base of the transistor; the transistor's current amplification combined with the properties of the circuit mean that small swings in Vin produce large changes in Vout.Various configurations of single transistor amplifier are possible, with some providing current gain, some voltage gain, and some both. From mobile phones to televisions, vast numbers of products include amplifiers for sound reproduction, radio transmission, and signal processing. The first discrete transistor audio amplifiers barely supplied a few hundred milli watts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved.Modern transistor audio amplifiers of up to a few hundred watts are common and relatively inexpensive.

NPN General Purpose Amplifier

Absolute Maximum Ratings TA=25°C :-

Symbol Paramet

er

Value Units

8

VCEO Collector-Emitter Voltage 30

V

VCES Collector-Base Voltage 30

V

VEBO Emitter-Base Voltage 5.0

V

IC Collector Current - Continuous 500

mA

TJ, Tstg Operating and Storage Junction Temperature Range

-55 to +150 C

Table 2.2: Transistor Absolute Maximum Ratings TA=25°C

NOTES:

1) These ratings are based on a maximum junction temperature of 150 degrees C.

2) These are steady state limits. The factory should be consulted on applications involving pulsed or low duty cycle operations.

Thermal Characteristics TA=25°C :-

Symbol Characteristic Max

Units

BC548 / A / B / C

PD Total Device Dissipationrate above 25 C

6255.

mW

mW / C

R JCThermal Resistance, Junction to Case 83

.3

C/W

R JAThermal Resistance, Junction to Ambient

200

C/W

Table 2.3: Transistor Thermal Characteristics TA=25°C

Electrical Characteristics TA = 25°C :-

a. OFF CHARACTERISTICS

Collector-Emitter Breakdown Voltage

IC = 10 mA, IB = 0 30 V

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Symbol Parameter Test Conditions Min Max Units

V(BR)CBO

Collector-Base Breakdown Voltage

IC = 10 A, IE = 0 30 V

V(BR)CES

Collector-Base Breakdown Voltage

IC = 10 A, IE = 0 30 V

V(BR)EBO

Emitter-Base Breakdown Voltage

IE = 10 A, IC = 0 5.0 V

ICBO Collector Cutoff Current VCB = 30 V, IE = 0

VCB = 30 V, IE = 0, TA = +150 C

15

5.0

nA

A

Table 2.4: Transistor OFF CHARACTERISTICS

b. ON CHARACTERISTICS

hFE DC Current Gain VCE = 5.0 V, IC = 2.0 mA 548

548A

548B

548C

110

110

200

420

800

220

450

800

VCE(sat) Collector-Emitter Saturation Voltage

IC = 10 mA, IB = 0.5 mA IC = 100 mA, IB = 5.0 mA

0.25

0.60

V

V

VBE(on) Base-Emitter On Voltage VCE = 5.0 V, IC = 2.0 mA VCE = 5.0 V, IC = 10 mA

0.58 0.70

0.77

V

V

Table 2.5: Transistor ON CHARACTERISTICS

2.4.2 LM 741 Operational Amplifier

General DescriptionThe LM741 series are general purpose operational amplifiers which feature improved 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:

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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 is identical to the LM741/LM741A except that the LM741C has their performance guaranteed over a 0˚C to+70˚C temperature range, instead of −55˚C to +125˚C.

Electrical Characteristics

Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits.

NOTE 2: For operation at elevated temperatures, these devices must be derated based on thermal resistance, and Tj max. (Listed under “Absolute MaximumRatings”). Tj = TA + (θjA PD).

Note3: For supply voltages less than ± 15V, the absolute maximum input Voltage is equal to the supply voltage.

Note 4: Unless otherwise specified, these specifications apply for VS = ± 15V, −55˚C ≤TA ≤+125˚C (LM741/LM741A). For the LM741C/LM741E, these specifications are limited to 0˚C ≤TA ≤+70˚C.

Note 5: Calculated value from: BW (MHz) = 0.35/Rise Time(µs).

Table 2.6: Parameters of IC LM 741

Connection Diagrams of LM 741

a. Metal Can Package

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Thermal Resistance

Cerdip (J) DIP (N) HO8 (H) SO-8 (M)

jA (Junction to Ambient)

100˚C/W 100˚C/W 170˚C/W 195˚C/W

jC (Junction to Case)

N/A N/A 25˚C/W N/A

Fig 2.3: OP-AMP in metal can package

b. Dual-In-Line or S.O Package

Fig 2.4: OP-AMP in DIP package

2.4.3 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 increase the gain to any value from20 to 200. The inputs are ground referenced while the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 mill watts when operating from a 6 volt supply, making the LM386 ideal for battery operation.

Features

Battery operation Minimum external parts

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Wide supply voltage range: 4V–12V or 5V–18V Low quiescent current drain: 4mA Voltage gains from 20 to 200 Ground referenced input Self-centering output quiescent voltage Low distortion: 0.2% (AV = 20, VS = 6V, RL = 8W, PO =

125mW, f = 1kHz) 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

DATA SHEET OF LM 386 IC

Parameter Conditions Min Typ Max UnitsOperatingSupply Voltage (VS)LM386N1,3,LM386M1, LM386MM1LM386N-4

4

5

12

18

V

V

Quiescent Current (IQ) VS = 6V, VIN = 0 4 8 mA

Output Power (POUT)LM386N-1, LM386M-1, LM386MM-1LM386N-3LM386N-4

VS = 6V, RL=8THD=10% VS = 9V, RL = 8, THD =10%,VS = 16V, RL = 32,

THD = 10%

250

500

700

325

700

1000

mW

mW

mW

Voltage Gain (AV) VS = 6V, f = 1 kHz 10 μF from Pin1to8

26 dB

Bandwidth (BW) VS = 6V, Pins 1 and 8 Open

300 Khz

Total HarmonicDistortion(THD)

VS = 6V, RL = 8W,POUT=125mW f = 1 kHz, Pins1and

0.2 %

13

8 Open

Power Supply Rejection Ratio (PSRR)

Input Resistance (RIN) Input Bias Current (IBIAS) VS = 6V, Pins 2 and 3 Open

VS = 6V, f = 1 kHz,CBYPASS=10 μF Pins 1 and 8 Open, Referred to Output

50

50 250

dB

KWnA

Table 2.7: Data sheet for IC LM 386

Absolute Maximum Ratings

Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified.

Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. OperatingRatingsindicateconditions,for which the device is functional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit is given, however, the typical value is a good indication of device performance.

Note 3: For operation in ambient temperatures above 25°C, the device must be derated based on a 150°C maximum junction temperature and 1) a thermal resistanceof 107°C/W junction to ambient for the dual-in-line package and 2) a thermal resistance of 170°C/W for the small outline package

Figure of IC LM 386

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Fig 2.5:IC layout of LM 386

2.4.4 RESISTORS

A Resistor is a two-terminal electronic component designed to oppose an electric current by producing a voltage drop between its terminals in proportion to the current, that is, in accordance with Ohm's law:

V = IR

Resistors are used as part of electrical networks and electronic circuits. They are extremely commonplace in most electronic equipment. Practical resistors can be made of various compounds and films, as well as resistance wire (wire made of a high-resistivity alloy, such as nickel/chrome).

The primary characteristics of resistors are their resistance and the power they can dissipate. Other characteristics include temperature coefficient, noise, and inductance. Less well-known is critical resistance, the value below which power dissipation limits the maximum permitted current flow, and above which the limit is applied voltage. Critical resistance depends upon the materials constituting the resistor as well as its physical dimensions; it's determined by design.

Resistors can be integrated into hybrid and printed circuits, as well as integrated circuits. Size, and position of leads (or terminals) are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power.

15

Fig 2.6 Resistors

16

Table 2.8:Types of Resistors

Units

The ohm (symbol: Ω) is a SI-driven unit of electrical resistance, named after Georg Simon Ohm. Commonly used multiples and submultiples in electrical and electronic usage are the milliohm, kilo-ohm, and mega-ohm.

Examples

R47 0.47 ohms

4R7 4.7 ohms

470R 470 ohms

4K7 4.7K ohms

47K 47K ohms

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47K3 47.3K ohms

470K 470K ohms

4M7 4.7M ohms

Table 2.9: Representation of Resistance units

The unit of Resistor is “OHMS”.

Sub Unit:

nΩ = Nano OHMS = 10-9 = 1/1000000000

µΩ = Micro OHMS = 10-6 = 1-1000000

mΩ = Milli OHMS= 10-3 = 1/1000

Ω = OHMS = 1

KΩ = Kilo OHMS = 103 = 1000

MΩ = Mega OHMS = 106 = 1000000

GΩ = Giga OHMS= 109 = 1000000000

Resistor Conversion:

1000 nΩ = 1 µΩ

1000 µ Ω = 1 mΩ

1000 mΩ = 1 Ω

1000 Ω = 1 KΩ

1000 KΩ = 1 MΩ

1000 MΩ = 1 GΩ

2.4.5 Variable Resistors

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    There are two kinds of resistors, FIXED and VARIABLE. The fixed resistor will have one value and will never change (other than through temperature, age, etc.). The resistors shown in A and B of figure 1-29are classed as fixed resistors. The tapped resistor illustrated in B has several fixed taps and makes more than one resistance value available. The sliding contact resistor shown in C has an adjustable collar that can be moved to tap off any resistance within the ohmic value range of the resistor.

    There are two types of variable resistors, one called a POTENTIOMETER and the other a RHEOSTAT (see views D and E of fig. 1-29.)An example of the potentiometer is the volume control on your radio, and an example of the rheostat is the dimmer control for the dash lights in an automobile. There is a slight difference between them. Rheostats usually have two connections, one fixed and the other moveable. Any variable resistor can properly be called a rheostat. The potentiometer always has three connections, two fixed and one moveable. Generally, the rheostat has a limited range of values and

a high current-handling capability. The potentiometer has a wide range of values, but it usually has a limited current-handling capability. Potentiometers are always connected as voltage dividers.

ConstructionVariable resistors consist of a resistance track with connections at both ends and a wiper which moves along the track as you turn the spindle. The track may be made from carbon, cer met (ceramic and metal mixture) or a coil of wire (for low resistances). The track is usually rotary but straight track versions, usually called sliders, are also available.

Variable resistors may be used as a rheostat with two connections (the wiper and just one end of the track) or as a potentiometer with all three connections in use. Miniature versions called presets are made for setting up circuits which will not require further adjustment.

Fig 2.7 Inside of a Variable Resistance

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Fig 2.8 Variable Resistance

Variable resistors are often called potentiometers in books and catalogues. They are specified by their maximum resistance, linear or logarithmic track, and their physical size. The standard spindle diameter is 6mm. The resistance and type of track are marked on the body:    4K7 LIN means 4.7 k linear track.1M LOG means 1 M logarithmic track.

Some variable resistors are designed to be mounted directly on the circuit board, but most are for mounting through a hole drilled in the case containing the circuit with stranded wire connecting their terminals to the circuit board.

2.4.6 Light-emitting diode.

Fig 2.9 LEDs

Blue, green, and red LEDs; these can be combined to produce most perceptible colors, including white. Infrared and ultraviolet (UVA) LEDs are also available.

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Fig 2.10 LED schematic symbol

.

A light-emitting-diode (LED) is a semiconductor diode that emits light when an electric current is applied in the forward direction of the device, as in the simple LED circuit. The effect is a form of electroluminescence where incoherent and narrow-spectrum light is emitted from the p-n junction in a solid state material.

LEDs are widely used as indicator lights on electronic devices and increasingly in higher power applications such as flashlights and area lighting. An LED is usually a small area (less than 1 mm2) light source, often with optics added directly on top of the chip to shape its radiation pattern and assist in reflection.[2][3] The color of the emitted light depends on the composition and condition of the semi conducting material used, and can be infrared, visible, or ultraviolet. Besides lighting, interesting

Applications include using UV-LEDs for sterilization of water and disinfection of devices,[4] and as a grow light to enhance photosynthesis in plants.

2.4.7 Photodiode

Fig 2.11 Different Types Of LEDs

A photodiode is a type of photodetector capable of converting light into either current or voltage, depending upon the mode of operation.

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Photodiodes are similar to regular semiconductor diodes except that they may be either exposed (to detect vacuum UV or X-rays) or packaged with a window or optical fibre connection to allow light to reach the sensitive part of the device. Many diodes designed for use specifically as a photodiode will also use a PIN junction rather than the typical PN junction.

2.4.8 UM66 Melody Generator:

This is the simplest ever musical calling bell that can be easily built. It uses the musical 3 pin IC UM66 and a popularly known Transistor BC548b. The circuit can be made even without soldering and the ideal for the first electronic project for newbie’s. Here the musical IC UM66 generates the music when it receives supply and drives a small speaker through a class c amplifier using silicon transistor BC548b. Here is a simple melody generator circuit you can make using an IC. The  UM66 series are CMOS IC’s  designed for using in calling bell, phone and toys. It has a built in ROM programmed for playing music. The device has very low power consumption. Thanks for the CMOS technology. The melody will be available at pin3 of UM66 and here it is amplified by using Q1 to drive the speaker. Resistor R1 limits the base current of Q1 within the safe values. Capacitor C1 is meant for noise suppression.

The battery supply should be kept in a battery container to ensure the connection. The volume of the sound of this circuit is so much that it can be used as a calling bell. To reduce the volume of the circuit then a resistance is inserted in place of the blue line connection. In this circuit please don't give the supply beyond 3 volt without modification as the IC may get damaged.

It is better that you should not run this circuit in Eliminator as most of the available eliminator don't have a good filter built in and have no precision over voltage protection. The circuit should not be run in Rechargeable battery also if the Speaker resistance is less than 8 Ohm and may burn the Transistor.

UM66 is a pleasing music generator IC which works on a supply voltage of 3V. The required 3V supply is given through a zener regulator its output is taken from the pin no1 and is given to a push pull amplifier to drive the low impedance loud speaker. A class A amplifier before push pull amplifier can be used to decrease the noise and improve output. UM66 is a 3 pin IC package just looks like a BC 547 transistor.

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SPECIFICATIONS OF UM66

IC UM 66 Datasheet

Table 2.10: Data Sheet of UM 66

2.4.9 LoudspeakerA loudspeaker (or "speaker") is an electro acoustical transducer that converts an electrical

signal to sound. The speaker pushes the air in accordance with the variations of an electrical signal and causes sound waves to propagate.

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 your speakers carefully. Some basic ideas about speaker enclosures might help with perspective.

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If a good loudspeaker is chosen from a reputable manufacturer and paid a good price for it, then it will be presumed that good sounds can be reproduction from it. But it is not without a good enclosure. The enclosure is an essential part of sound production because of the following problems with a direct radiating loudspeaker.

Fig 2.12 Layout of a Small Speaker

ConstructionAn enormous amount of engineering work has gone into the design of today's dynamic

loudspeaker. A light voice coil is mounted so that it can move freely inside the magnetic field of a strong permanent magnet. The speaker cone is attached to the voice coil and attached with a flexible mounting to the outer ring of the speaker support. Because there is a definite "home" or equilibrium position for the speaker cone and there is elasticity of the mounting structure, there is inevitably a free cone resonant frequency like that of a mass on a spring.

The frequency can be determined by adjusting the mass and stiffness of the cone and voice coil, and it can be damped and broadened by the nature of the construction, but that naturalmechanical frequency of vibration is always there and enhances the frequencies in the frequency range near resonance. Part of the role of a good enclosure is to minimize the impact of this resonant frequency.

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CHAPTER 3

PROBLEM DEFINITION, DESIGN & IMPLEMENTATION

IR MUSIC TRANSMITTER AND RECIEVER

3.1 TRANSMITTERThe IR music transmitter works off a 9V battery. Figure (1) shows the circuit of the IR music Transmitter. It uses popular melody generator IC U M-66 (IC1) that can continuously generate musical tones. The output of IC1 is fed to the IR driver stage (Built across the transistors T1 and T2) to get the maximum range. Here the red LED (LED1) flickers according to the musical tones generated by UM66 IC, indicating modulation. IR LED2 and LED3 are infrared transmitting LEDs. For maximum sound transmission these should be oriented towards IR phototransistor L14F1 (T3).

3.2 RECEIVERThe IR music receiver uses popular op-amp IC µA741 and audio-frequency amplifier IC LM386 along with phototransistor L14F1 and some discrete components(Fig. 2).The melody generated by IC UM66 is transmitted through IR LEDs, received by phototransistor T3 and fed to pin 2 of IC µA741 (IC2). Its gain can be varied using pot meter VR1. The output of IC µA741 is fed to IC LM386 (IC3) via capacitor C5 and pot meter V- R 2 .The melody produced is heard through the receiver’s loudspeaker. Pot meter VR2 is used to control the volume of Loudspeaker LS1 (8-ohm, 1W).

3.3 Basic Working:The electrical signal from your music player is converted into an invisible infrared light signal by the infrared light emitting diode (IR LED) in the transmitter circuit. To transmit this over a longer distance, a brighter IR LED is needed or an invisible light is to be focused using lens. The invisible infrared light signal must hit the photo transistor in the receiver. The photo transistor in the receiver converts this invisible infrared light signal into an electrical signal. Then, the amplifier in the receiver circuit takes this electrical signal and makes it larger using energy from the battery. Finally, this larger electrical signal drives the speaker which turns electrical energy into sound energy.

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3.4 Circuit Diagram:

a. Transmitter:

Fig 3.1: Transmitter Section

b. Receiver:

Fig 3.2: Receiver Section

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3.5 Block Diagram:

a. Transmitter:

+9V power supply

Fig 3.3: Block Diagram of Transmitter

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3.3 v regulatorMelody

GeneratorTransistor

DriverStage - 1

Transistor Driver

Stage - 2

IR LED

LED Music Flicker

Indicator

b. Receiver:

+9V Power Supply

Fig 3.4:Block diagram of Receiver

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PhotoTransistor

Audio Amplifier

stage-1

Audio Amplifier

stage-2

Loud Speaker

Gain Control

Gain Control

3.6 CIRCUIT DESCRIPTION

The circuit can be divided into two parts:

IR music transmitter and Receiver.

The IR music transmitter works off a 9V battery, while the IR music receiver works off regulated 9V to 12V. Fig. 3.1 shows the circuit of the IR music transmitter. It uses popular melody generator IC UM66 (IC1) that can continuously generate musical tones. The output of IC1 is fed to the IR driver stage (built across the transistors T1 and T2) to get the maximum range. Here the red LED (LED1) flickers according to the musical tones generated by UM66 IC, indicating modulation. IR LED2 and LED3 are infrared transmitting LEDs. For maximum sound transmission these should be oriented towards IR phototransistor L14F1 (T3). The IR music receiver uses popular op-amp IC μA741 and audio-frequency amplifier IC LM386 along with phototransistor L14F1 and some discrete components. The melody generated by IC UM66 is transmitted through IR LEDs, received by phototransistor T3 and fed to pin2 of IC μA741 (IC2). Its gain can be varied using potential meter VR1. The output of IC μA741 is fed to IC LM386 (IC3) via capacitor C5 and potential meter VR2.The melody produced is heard through the receiver’s loudspeaker. Potential meter VR2 is used to control the volume of loudspeaker LS1 (8-ohm, 1W). Switching off the power supply stops melody generation.

3.7 WORKING

Using this circuit, audio musical notes can be generated and heard up to a distance of IR MUSIC TRANSMITTER ANDRECEIVER 10 meters .The circuit can be divided into two parts: IR music transmitter and receiver. The IR music transmitter works off a 9V battery, while the IR music receiver works off regulated 9V to12V. It uses popular melody generator IC UM66(IC1) that can continuously generate musical tones. The output of IC1 is fed to the IR driver stage (built across the transistors T1 and T2) to get the maximum range. Here the red LED (LED1) flickers according to the musical tones generated by UM66 IC, indicating modulation.IR LED2 and LED3 are infrared transmitting LEDs. For maximum sound transmission these should be oriented towards IR phototransistor L14F1 (T3).The IR music receiver uses popular op-amp IC μA741 and audio-frequency amplifier IC LM386 along with phototransistor L14F1 and some discrete components (Fig. 2).The melody generated by IC UM66is transmitted through IR LEDs, received by phototransistorT3 and fed to pin 2 of IC μA741 (IC2). Its gain can be varied using pot meter VR1. The output of IC μA741 is fed to IC LM386 (IC3) via capacitorC5 and pot meter VR2.The melody produced is heard through the receiver’s loudspeaker. Pot meter VR2 is used to control the volume of loudspeaker LS1 (8-ohm,1W). Switching off the power supply stops melody generation.

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CHAPTER 4

CIRCUIT CONSTRUCTION METHODS AND DEPLOYMENT

4.1 PCB manufacturing process:

Design Specification It is an important process in the fabrication of electronic equipment. The design of PCBs

(Printed circuit board) depends on circuit requirements like noise immunity, working frequency

and voltage levels etc. High power PCBs requires a special design strategy. The fortification

process to the printed circuit board will determine to a large extent the price and reliability of the

equipment. A common target aimed is the fabrication of small series of small series of highly

reliable professional quality PCBs with low investment.

The layout of a PCB has to incorporate all the information of the board before one can go on the

artwork preparation. This means that a concept which clearly defines all the details of the circuit

and partly defines the final equipment is prerequisite before the actual layout can start.

4.2 PCB Layout: a. Transmitter:

Fig 4.1 Transmitter PCB Layout

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b.Receiver:

Fig 4.2 Receiver PCB Layout

4.3 Board types

The two most popular PCB types are:

4.3.1 Single Sided Boards

The single sided PCBs are mostly used in entertainment electronics where manufacturing costs

have to be kept at a minimum. However in industrial electronics cost factors cannot be neglected

and single sided boards should be used wherever a particular circuit can be accommodated on

such boards.

4.3.2 Double Sided Boards ~ Double sided PCBs can be made with or without plated

through holes. The production of boards with plated through holes is fairly expensive. Therefore

plated through hole boards are only chosen where the circuit complexities and density of

components does not leave any other choice.

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4.4 PCB Designing:

After the accomplishment of circuit designing, next step that follows is PCB making. Among the

various discoveries and development to bring electronics to the level it has reached until now,

PCB has definitely contributed in a significant manner as a means to inter-connect electronic

components. The design of PCB can be considered as the last step in the electronic circuit design

as well as the first major step in the production of PCB’s. Intimate knowledge of all implication

is required. The designing of PCB consist of designing of layout followed by generation or

preparation of artwork. The layout therefore includes all the relevant aspects and details of the

PCB design. The various steps involved in PCB making are as follows:

a) Layout Planning

b) Component Hole

c) Graphic Layout

d) Etching

e) Drilling

f) Component Mounting

g) Soldering

4.4.1 Layout Planning

The layout of PCB must incorporate all the information that clearly defines all details of the

circuit and partly of the final equipment. A detail circuit diagram is an important prerequisite.

Layout planning takes care of component layout as well as their interconnection. The layout

should be developed in the direction of signal flow as far as possible, so that one achieves

shortest possible interconnections. Among the components, the larger ones are placed first and

the space between is filled with smaller ones. Components requiring input/output connections

come near the connectors. In designing the interconnection, which are usually done with pencil,

actual space requirement in the artwork must be considered. The end of the layout designing is

the pencil sketched component and conductor drawing, which is called layout sketch. Beside the

component outline, component holes and interconnecting pattern, the layout sketch should also

include information on:

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4.4.2 Component holes

Usually in a given PCB cost of the holes required is of one particular diameter and this diameter

is mentioned once in the layout sketch. Holes of different diameter are shown with a code in the

actual layout sketch. The code must explain outside the layout area. For e.g. we have used two

kinds of holes are of 0.8mm and 1.1mm.0.8 mm for all the components except jumpers and IC

base. For jumpers and IC based we drilled 1mm holes. Changing of our track from large to small

and then back to large again is known as “necking”. This is often required when we have to go

between IC or component pads. This allows having nice big low impedance tracks, but still has

the flexibility of route between tight spots.

In practice, the current flowing through it and the maximum temperature rise of the track that can

be tolerated will dictate track width. Every track will have a certain amount of resistance, so the

track will dissipate heat just like a resistor. The wider the track, the lower is the resistance.

4.4.3 Graphic Layout

The Graphic layout or the Artwork is the basic circuit design that is required on the PCB. The

circuit connections and the components are together setup in a particular design which is printed

on the Circuit Board.

4.4.4 Etching (Patterning)

Copper over the entire substrate, sometimes on both sides, (creating a “blank PCB”) then

removing unwanted copper after applying a temporary mask (e.g. by chemical etching), leaving

only the desired copper traces. A few PCB’s are made by adding traces to the bare substrate (or a

substrate with a very thin layer of copper) usually by a complex process of multiple

electroplating steps.

Chemical etching

Inexpensive ingredients, and with proper use and maintenance, literally never wears out. The

real beauty of this mixture of hydrogen peroxide, sulphuric acid, copper sulphate and organic

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stabilizers is that excess copper can be removed by simple precipitation, after which, the bath is

ready to consume more copper. In addition, during operation, the etch ant is “self agitating”. The

bubbles and heat evolve during etching, so thoroughly stir up the bath the etch ant works almost

as well in a simple dip (immersion) tank as it does in a far more expensive spray etcher. Screen

printing ink is used according to the type of etch ant used. For acid etching, an acid resistive ink

is used, which is soluble in alkaline solution

4.4.5 Drilling

Drilling can be done using a CNC machine or manually.

a.Manual Drilling

With the laminate stack formatted as detailed above, manual drilling is a straightforward, if

somewhat mind-numbing process. Items to consider include: When using a conventional drill

press, hole placement accuracy can be improved and drill breakage minimized through the use of

a “sensitive drilling” or “finger” chuck. Small format, precision high-speed drill presses, ideal for

PCB fabrication, is also available from a number of sources.

If available, position a work lamp on a flexible mount as close to the work surface as possible.

Minimize burr formation, and outlast HSS bits almost 10 to 1. The carbide drills are easier to

break and must be handled carefully. Always use drill bits that have been fitted with depth

setting rings. This will allow you to set the plunge depth stop on your drill press to a single value

that will work for all bit diameters.

b. Through-holes

Load the largest diameter bit to be used into the drill chuck, making sure that the depth ring is

pressed firmly against the ends of the chuck jaws when they are fully tightened. Using a piece of

scrap backing materials as a gauge, adjust the spindle travel stop on your drill press to a depth

that insures that the entire tip of the drill bit penetrates at least half of the material’s thickness.

Under no circumstances allow a PCB drill bit to drill into the table of your drill press. PCB bits

are specially designed to drill copper clad and will shatter if plunged into cast iron, steel, or

aluminum.

Starting with largest diameter drill bit, drill all the through holes, stopping periodically to insure

that the drill bit has not snapped off and that the spindle travel stop has not slipped.

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As you drill each hole size check off that diameter on the drilling chart. This is a good

bookkeeping technique that will help you keep track of your progress and insure that no holes

size is missed.

Hold the stack up to the light for visual inspection. Ascertain that all of the holes have been

drilled through and that none are blocked by drill debris. If some debris is seen, remove by

carefully pushing a smaller diameter bit through the hole.

4.4.6 Component Mounting

From the greatest variety of electronic components available, which runs into thousands of

different types 1, is often a perplexing task to know which is right for a given job. There could be

damage such as hairline crack on PCB. If there are, then they can be repaired by soldering a short

link of bare copper wire over the affected part. This holds the component in position ready for

soldering. Some components will be considerably larger. So it is best to start mounting the

smallest first and progressing through the largest. Next will be probably the resistor, small signal

diodes or other similar size components. Some capacitors are also very small but it would be best

to fit it afterwards. Although transistors and integrated circuit are small items there are good

reasons for leaving the soldering of these until the last step. All the components before mounting

are rubbed with sand paper so that oxide layer is removed from the tips. Now they are mounted

according to the component layout.

4.4.7 Soldering

This is the operation of joining the components with PCB after this operation the circuit will be

ready to use to avoid any damage or fault during this operation following care must be taken. A

longer duration contact between soldering iron bit and components lead can exceed the

temperature rating of the device and cause partial or total damage of the device. Hence, before

soldering we must read the maximum soldering temperature and soldering time for device. The

wattage of soldering iron should be selected as maximum as permissible for that soldering place.

To protect the device by leakage current of iron its bit should be earthed properly.We should

select soldering wire with proper ratio of Pb and Tn to provide the suitable melting temperature.

roper amount of good quality flux must be applied on the soldering point to avoid dry soldering.

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CHAPTER 5

FUTURE ENHANCEMENTS & CONCLUSION

5.1 APPLICATIONS

Today everyone is looking for portability of electronic gadgets. The IR rays communication can

play a crucial role in developing such wireless gadgets. Here are a few gadgets that can be built

using IR transmission and reception systems.

A few of those applications are:

1. Wireless Music Systems.

2. Mobile gadgets.

3. CC cameras.

4. Remote controls.

5. Infrared lasers are used in communications.

5.1.1 Wireless Music Systems The principle used in above circuits can be used in wireless music systems. The speakers that we use today in our desktop computers can be made wireless by using infrared ray transmission. This increases the portability of the audio systems and in fact a desktop computer can be used as disc-man in our room.

5.1.2 Mobile gadgets The same principle of IR audio Transmission can be used in cord less earphones which can be very useful especially when you are driving.

Fig 5.1 IR Wireless Headphones

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5.1.3 CC Cameras IR ray transmission can be employed in microphones that can be used in cc cameras. This reduces the complexity to a great extent. The audio systems that are employed today for security purposes in cc cameras can be replaced with IR transmission systems which are quite simple and easy to handle

Fig 5.2 IR CC Camera

5.1.4 Remote ControlsRF-Link AVS-5811 5.8 GHz Wireless PAL Audio/Video Transmitter and Receiver System Built-in IR Remote Extender

The RF-Link AVS-5811 5.8GHz wireless PAL video/audio sender consists of one transmitter and one receiver. This device transmits wirelessly vivid video and hi-fi stereo sound from a VCR, TV set, LD, DVD, and VCD, Satellite Receiver or cable set top box to any TV or monitor. It can also be used in conjunction with a camcorder or CCD camera and turns into a wireless security monitoring system. As to the transmission capability, the signal can go up to 300 feet clear light-of-sight and even penetrate wall. With the built-in IR remote extender, it allows the user to remotely control the audio/video sources in the other rooms. In addition, four user selectable channels allow multiple transmitters to multiple receivers operation in the same area. All these advanced features will make your home life with amazing convenience and joy.

Avoid the interference from crowded 2.4GHz ISM band applications such as Video Sender, 802.11b Wireless LAN, Bluetooth, Cordless Phone, Microwave Oven, etc 5.8 GHz wireless transmitter and receiver with 4 selectable channels Transmitting and receiving of crisp video and hi-fi stereo even through walls Long transmission range up to 300 feet clear line-of-sight. PAL video format

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Fig 5.3 IR Remote Extender

5.1.5 CommunicationInfrared LED and Laser Product Overview -The Next Generation of Wireless IR Links

Connecting high-speed LAN systems while maintaining full network speeds can be accomplished by using high-performance infrared (IR) optical LED/laser technology. Flight Transport systems offer a complete series of next generation wireless line-of-sight IR communication solutions. The Flight Transport systems result from 30 aggregate years of research and development in the field of IR communications. Using the right combination of LED/VCSEL/LASER transmit/receive boards, IR systems can be tailored for your specific speed and distance requirements. 

Fig 5.4 IR lasers in Communications

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5.2 ADVANTAGES AND DISADVANTAGES

5.2.1 ADVANTAGESThe greatest advantages of infrared are being able to use your own receiver with public transmitters (like in movie theatres) and getting the best sound reproduction. Because of their superior sound reproduction, they are often used movies, plays and musical productions. They may not be the best system for profound hearing losses as they lack the acoustic output (loudness) of FM systems. On the other hand, they also present less risk of injury.Infrared systems are secure systems because the signal will not leave the room. Thus, it is the system of choice for jury deliberations and business meetings that need to protect discussions (e.g., around development of new materials or software).Because light does not transmit through walls, multiple systems can be used within a building. With the exception of high frequency lights and bright sunlight, there are few sources of interference with infrared system.

a. Parameters wise advantages are:

1. Highly sensitive.

2. Two stage Gain control.

3. Very low noise.

4. Low cost and reliable circuit.

5. Can transmit up to 10 meter.

b. Usage wise advantages are:

1. Compatibility: 95 kHz is industry standard

2. No spillover means security

3. Can be used in adjacent rooms

4. Widest bandwidth and best sound reproduction

5. Appropriate for mild to moderate/ Severe loss

6. Not affected by radi transmission.

5.2.2 DISADVANTAGESReceivers are required for all users. The receivers and transmitters must be in direct line of sight of each other. This reduces the amount of flexibility you have in movement within the room without interrupting the signal. Unlike FM, you cannot cover the receiver or put it anywhere where the direct line of sight will be blocked (like clipping it to your belt and sitting in a class).Quality varies with the company, here, too. Only purchase systems from dealers with trial periods and return policies, and who offer troubleshooting on the phone or in person. Large areas require multiple emitter panels, which will increase the cost of the system.

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The disadvantages are:

1. Not for long distance.

2. Work in fixed range.

3. Noise if object between transmitter and receiver.

4. Receivers are required for every device.

5. Must have line of sight.

6. Indoor or evening use

7. High intensity or fluorescent lights cause interference.

8. Large areas require multiple emitter panels.

5.3 CONCLUSIONIR ray communication is very easy to understand and simple to implement. It finds various applications in short distance field of communications. It is one of the best ways of building wireless gadgets. In future there is scope of building virtual environment using the principles of IR ray transmission and reception. Virtual gaming which also employs IR reception techniques is still in research process which is soon going to rule the world of gaming.

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REFERENCES

Electronics for you (jan 2007)

www.fairchild.com

www.national.com

www.scridb.com

www.wineyardtechnologies.com

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