INFRARED (IR) MUSIC TRANSMITTER AND RECEIVER

ABSTRACT

In the present days people are used to use radio frequency (RF) technology

to listen the music.RF technology is using rapidly because the communication i.e. data

transfer is possible in the long distance cases also.

But in our project we are using Infrared (IR) technology to transfer the

music. Here we are using IR transmitter and IR receiver. In the transmitter side we have a

music tones generator IC i.e. UM66. The output of this is fed to the IR driver stage to get

the maximum range. Here the red LED (LED1) flickers according to the musical tones

generated by UM66 IC, indicating modulation. For maximum sound transmission these

should be oriented towards IR photo-transistor L14F1 (T3). The IR music receiver uses

popular op-amp IC µA741 and audio-frequency amplifier IC LM386 along with photo-

transistor L14F1.

In the receiver side we are using photo transistor and its gain can be

increased by potentiometers. The receiving music tones can be delivered through the

loudspeaker.

This project will be very useful for short distance music transferring in low

budjet.

CHAPTER 3

HARDWARE COMPONENTS

1. UM66

2. 741 OP-AMP

3. LM 386

4. L14F1 PHOTO TRANSISTOR

5. LS1 (8 ohm, 1w) loud speaker.

6. Transistors ,resistors ,capacitors.

3.1 TRANSMITTER SECTION

3.2 RECEIVER SECTION

POWER SUPPLY PHOTO TRANSISTOR

OP-AMP AUDIO FREQUENCY AMPLIFIER

POWER SUPPLYUM66 MELODY

GENERATOR

TRANSMITTING LEDS

DRIVER STAGE

(TRANSISTOR)

3.3 DC BATTERY

A battery is a device that can store electricity. Some are rechargeable,

and some are not. They store direct current (DC) electricity.

A battery really means two or more wet or dry cells connected in series for more voltage,

or in parallel for more current, although people often call a cell a battery. AA, AAA, C,

and D batteries all have 1.5 volts. The voltage of a cell depends on the chemicals used

while the amount of power or current it can supply also depends on how large the cell is;

a bigger cell of a given type can supply more amps, or for a longer time.

The chemical reactions that occur in a battery are exothermic reactions and, thus, produce

heat. For example, if you leave your laptop on for a long time, and then touch the battery,

it will be warm or hot. However, the batteries used in laptops are called lithium-ion

batteries and they sometimes do have a fire hazard (A few years ago, dell laptops that that

were powered by lithium batteries began to catch fire, though this event was rare.).

Batteries come in lots of different shapes and sizes and voltages. It is possible, but not

easy, to run wires to use an odd size battery for an odd purpose.

LOUD SPEAKER

Batteries are always more costly/expensive than mains electricity. But mains electricity is

not suitable for things that are mobile.

Bicycles have tail-lights that can be operated by batteries, and sometimes by a little

generator powered by the wheels.

Hand and foot generators can be used to replace batteries in various devices, but they can

be tiresome.

Wind-up generators are now available to power small clockwork radios, clockwork

torches, etc.

Since clockwork clocks have been around for hundreds of years, and batteries for two

hundred, it is amazing that no-one thought of a clockwork torch until recently.

Rechargeable batteries are recharged by reversing the chemical reaction that occurs

within the battery. But a rechargeable battery can only be recharged a given amount of

time (recharge life). Even iPods, with built in batteries, cannot be recharged forever.

Moreover, each time a battery is recharged , its ability to hold a charge is degraded a bit.

Non-rechargeable batteries should not be charged as various caustic and corrosive

substances can leak out, such as potassium hydroxide.

http://upload.wikimedia.org/wikipedia/commons/d/d9/Batterien.jpg

The very first batteries were invented in the middle east around 1000 B.C. Then they

were buried and forgotten about.

The first battery was invented in 1800 by Alessandro Volta. Nowadays, his battery is

called the voltaic pile.

Later batteries were bottles with a fluid and some metal rods in them. People had to be

careful not to turn these batteries upside-down so the fluid would spill.

In modern batteries, the fluid is "soaked up" in a kind of paste. And everything is put in a

completely tight case: Because of this case, nothing can spill out of the battery. An

exception is car batteries; they still have liquid inside.

Types of batteries

Alkaline battery, "alkaline", not rechargeable

Leclanche battery, "super heavy duty", not rechargeable

Nickel metal-hydride battery, "NiMH", rechargeable

Nickel cadmium battery, "NiCd", rechargeable

Lead acid battery, rechargeable, car battery

Lithium battery, unrechargeable, "coin cell"

Lithium-ion battery, rechargeable, used in cell phones and laptops

Mercury battery, unrechargeable

Silver oxide battery, unrechargeable, watch battery

Alternatives to Batteries

Solar cell

3.4 RESISTOR

A typical axial-lead resistor

Partially exposed Tesla TR-212 1 kΩ carbon film resistor

Axial-lead resistors on tape. The tape is removed during assembly before the leads are

formed and the part is inserted into the board.

Three carbon composition resistors in a 1960s valve (vacuum tube) radio

A resistor is a two-terminal passive electronic component which implements electrical

resistance as a circuit element. When a voltage V is applied across the terminals of a

resistor, a current I will flow through the resistor in direct proportion to that voltage. The

reciprocal of the constant of proportionality is known as the resistance R, since, with a

given voltage V, a larger value of R further "resists" the flow of current I as given by

Ohm's law:

Resistors are common elements of electrical networks and electronic circuits and are

ubiquitous 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). Resistors are also implemented within integrated circuits,

particularly analog devices, and can also be integrated into hybrid and printed circuits.

The electrical functionality of a resistor is specified by its resistance: common

commercial resistors are manufactured over a range of more than 9 orders of magnitude.

When specifying that resistance in an electronic design, the required precision of the

resistance may require attention to the manufacturing tolerance of the chosen resistor,

according to its specific application. The temperature coefficient of the resistance may

also be of concern in some precision applications. Practical resistors are also specified as

having a maximum power rating which must exceed the anticipated power dissipation of

that resistor in a particular circuit: this is mainly of concern in power electronics

applications. Resistors with higher power ratings are physically larger and may require

heat sinking. In a high voltage circuit, attention must sometimes be paid to the rated

maximum working voltage of the resistor.

The series inductance of a practical resistor causes its behavior to depart from ohms law;

this specification can be important in some high-frequency applications for smaller

values of resistance. In a low-noise amplifier or pre-amp the noise characteristics of a

resistor may be an issue. The unwanted inductance, excess noise, and temperature

coefficient are mainly dependent on the technology used in manufacturing the resistor.

They are not normally specified individually for a particular family of resistors

manufactured using a particular technology.[1] A family of discrete resistors is also

characterized according to its form factor, that is, the size of the device and position of its

leads (or terminals) which is relevant in the practical manufacturing of circuits using

them.

CHAPTER 5

WORKING

Ohm's law:

The behavior of an ideal resistor is dictated by the relationship specified in Ohm's law:

Ohm's law states that the voltage (V) across a resistor is proportional to the current (I)

passing through it, where the constant of proportionality is the resistance (R).

Equivalently, Ohm's law can be stated:

This formulation of Ohm's law states that, when a voltage (V) is present across a

resistance (R), a current (I) will flow through the resistance. This is directly used in

practical computations. For example, if a 300 ohm resistor is attached across the

terminals of a 12 volt battery, then a current of 12 / 300 = 0.04 amperes (or 40

milliamperes) will flow through that resistor.

]series and parallel resistors

In a series configuration, the current through all of the resistors is the same, but the

voltage across each resistor will be in proportion to its resistance. The potential difference

(voltage) seen across the network is the sum of those voltages, thus the total resistance

can be found as the sum of those resistances:

As a special case, the resistance of N resistors connected in series, each of the same

resistance R, is given by NR.

Resistors in a parallel configuration are each subject to the same potential difference

(voltage), however the currents through them add. The conductances of the resistors then

add to determine the conductance of the network. Thus the equivalent resistance (Req) of

the network can be computed:

The parallel equivalent resistance can be represented in equations by two vertical lines

"||" (as in geometry) as a simplified notation. For the case of two resistors in parallel, this

can be calculated using:

As a special case, the resistance of N resistors connected in parallel, each of the same

resistance R, is given by R/N.

A resistor network that is a combination of parallel and series connections can be broken

up into smaller parts that are either one or the other. For instance,

However, some complex networks of resistors cannot be resolved in this manner,

requiring more sophisticated circuit analysis. For instance, consider a cube, each edge of

which has been replaced by a resistor. What then is the resistance that would be measured

between two opposite vertices? In the case of 12 equivalent resistors, it can be shown that

the corner-to-corner resistance is 5⁄6 of the individual resistance. More generally, the Y-Δ

transform, or matrix methods can be used to solve such a problem.

One practical application of these relationships is that a non-standard value of resistance

can generally be synthesized by connecting a number of standard values in series and/or

parallel. This can also be used to obtain a resistance with a higher power rating than that

of the individual resistors used. In the special case of N identical resistors all connected in

series or all connected in parallel, the power rating of the individual resistors is thereby

multiplied by N.

Power dissipation

The power P dissipated by a resistor (or the equivalent resistance of a resistor network) is

calculated as:

The first form is a restatement of Joule's first law. Using Ohm's law, the two other forms

can be derived.

The total amount of heat energy released over a period of time can be determined from

the integral of the power over that period of time:

Practical resistors are rated according to their maximum power dissipation. The vast

majority of resistors used in electronic circuits absorb much less than a watt of electrical

power and require no attention to their power rating. Such resistors in their discrete form,

including most of the packages detailed below, are typically rated as 1/10, 1/8, or 1/4

watt.

Resistors required to dissipate substantial amounts of power, particularly used in power

supplies, power conversion circuits, and power amplifiers, are generally referred to as

power resistors; this designation is loosely applied to resistors with power ratings of 1

watt or greater. Power resistors are physically larger and tend not to use the preferred

values, color codes, and external packages described below.

If the average power dissipated by a resistor is more than its power rating, damage to the

resistor may occur, permanently altering its resistance; this is distinct from the reversible

change in resistance due to its temperature coefficient when it warms. Excessive power

dissipation may raise the temperature of the resistor to a point where it can burn the

circuit board or adjacent components, or even cause a fire. There are flameproof resistors

that fail (open circuit) before they overheat dangerously.

Note that the nominal power rating of a resistor is not the same as the power that it can

safely dissipate in practical use. Air circulation and proximity to a circuit board, ambient

temperature, and other factors can reduce acceptable dissipation significantly. Rated

power dissipation may be given for an ambient temperature of 25 °C in free air. Inside an

equipment case at 60 °C, rated dissipation will be significantly less; a resistor dissipating

a bit less than the maximum figure given by the manufacturer may still be outside the

safe operating area and may prematurely fail.

Construction

A single in line (SIL) resistor package with 8 individual, 47 ohm resistors. One end of each

resistor is connected to a separate pin and the other ends are all connected together to

the remaining (common) pin - pin 1, at the end identified by the white dot.

Lead arrangements

Resistors with wire leads for through-hole mounting

ZENER DIODE

A Zener diode is a special kind of diode which allows current to flow in the forward

direction same as an ideal diode, but will also permit it to flow in the reverse direction

when the voltage is above a certain value known as the breakdown voltage, "Zener knee

voltage" or "Zener voltage." The device was named after Clarence Zener, who discovered

this electrical property.

A conventional solid-state diode will not allow significant current if it is reverse-biased

below its reverse breakdown voltage. When the reverse bias breakdown voltage is

exceeded, a conventional diode is subject to high current due to avalanche breakdown.

Unless this current is limited by circuitry, the diode will be permanently damaged due to

overheating. In case of large forward bias (current in the direction of the arrow), the

diode exhibits a voltage drop due to its junction built-in voltage and internal resistance.

The amount of the voltage drop depends on the semiconductor material and the doping

concentrations.

A Zener diode exhibits almost the same properties, except the device is specially

designed so as to have a greatly reduced breakdown voltage, the so-called Zener voltage.

By contrast with the conventional device, a reverse-biased Zener diode will exhibit a

controlled breakdown and allow the current to keep the voltage across the Zener diode

close to the Zener breakdown voltage. For example, a diode with a Zener breakdown

voltage of 3.2 V will exhibit a voltage drop of very nearly 3.2 V across a wide range of

reverse currents. The Zener diode is therefore ideal for applications such as the

generation of a reference voltage (e.g. for an amplifier stage), or as a voltage stabilizer for

low-current applications.

The Zener diode's operation depends on the heavy doping of its p-n junction allowing

electrons to tunnel from the valence band of the p-type material to the conduction band of

the n-type material. In the atomic scale, this tunneling corresponds to the transport of

valence band electrons into the empty conduction band states; as a result of the reduced

barrier between these bands and high electric fields that are induced due to the relatively

high levels of dopings on both sides.[1] The breakdown voltage can be controlled quite

accurately in the doping process. While tolerances within 0.05% are available, the most

widely used tolerances are 5% and 10%. Breakdown voltage for commonly available

zener diodes can vary widely from 1.2 volts to 200 volts.

Another mechanism that produces a similar effect is the avalanche effect as in the

avalanche diode. The two types of diode are in fact constructed the same way and both

effects are present in diodes of this type. In silicon diodes up to about 5.6 volts, the Zener

effect is the predominant effect and shows a marked negative temperature coefficient.

Above 5.6 volts, the avalanche effect becomes predominant and exhibits a positive

temperature coefficient. In a 5.6 V diode, the two effects occur together and their

temperature coefficients neatly cancel each other out, thus the 5.6 V diode is the

component of choice in temperature-critical applications. Modern manufacturing

techniques have produced devices with voltages lower than 5.6 V with negligible

temperature coefficients, but as higher voltage devices are encountered, the temperature

coefficient rises dramatically. A 75 V diode has 10 times the coefficient of a 12 V diode.

All such diodes, regardless of breakdown voltage, are usually marketed under the

umbrella term of "Zener diode".

ADVANTAGES:

Zener diode shown with typical packages. Reverse current − iZ is shown.

Zener diodes are widely used as voltage references and as shunt regulators to regulate the

voltage across small circuits. When connected in parallel with a variable voltage source

so that it is reverse biased, a Zener diode conducts when the voltage reaches the diode's

reverse breakdown voltage. From that point on, the relatively low impedance of the diode

keeps the voltage across the diode at that value.

In this circuit, a typical voltage reference or regulator, an input voltage, U IN, is regulated

down to a stable output voltage UOUT. The intrinsic voltage drop of diode D is stable over

a wide current range and holds UOUT relatively constant even though the input voltage

may fluctuate over a fairly wide range. Because of the low impedance of the diode when

operated like this, Resistor R is used to limit current through the circuit.

In the case of this simple reference, the current flowing in the diode is determined using

Ohms law and the known voltage drop across the resistor R. IDiode = (UIN - UOUT) / RΩ

The value of R must satisfy two conditions:

1. R must be small enough that the current through D keeps D in reverse breakdown.

The value of this current is given in the data sheet for D. For example, the

common BZX79C5V6 device, a 5.6 V 0.5 W Zener diode, has a recommended

reverse current of 5 mA. If insufficient current exists through D, then UOUT will be

unregulated, and less than the nominal breakdown voltage (this differs to voltage

regulator tubes where the output voltage will be higher than nominal and could

rise as high as UIN). When calculating R, allowance must be made for any current

through the external load, not shown in this diagram, connected across UOUT.

2. R must be large enough that the current through D does not destroy the device. If

the current through D is ID, its breakdown voltage VB and its maximum power

dissipation PMAX, then IDVB < PMAX.

A load may be placed across the diode in this reference circuit, and as long as the zener

stays in reverse breakdown, the diode will provide a stable voltage source to the load.

Shunt regulators are simple, but the requirements that the ballast resistor be small enough

to avoid excessive voltage drop during worst-case operation (low input voltage

concurrent with high load current) tends to leave a lot of current flowing in the diode

much of the time, making for a fairly wasteful regulator with high quiescent power

dissipation, only suitable for smaller loads.

Zener diodes in this configuration are often used as stable references for more advanced

voltage regulator circuits.

These devices are also encountered, typically in series with a base-emitter junction, in

transistor stages where selective choice of a device centered around the avalanche/Zener

point can be used to introduce compensating temperature co-efficient balancing of the

transistor PN junction. An example of this kind of use would be a DC error amplifier

used in a regulated power supply circuit feedback loop system.

Zener diodes are also used in surge protectors to limit transient voltage spikes.

Another notable application of the zener diode is the use of noise caused by its avalanche

breakdown in a random number generator that never repeats.

Zener Diode Voltage Regulators

Introduction

A Zener diode is a PN junction that has been specially made to have a reverse voltage

breakdown at a specific voltage. Its characteristics are otherwise very similar to common

diodes. In breakdown the voltage across the Zener diode is close to constant over a wide

range of currents thus making it useful as a shunt voltage regulator.

Characteristics

Figure 1 shows the current versus voltage curve for a Zener diode. Observe the nearly

constant voltage in the breakdown region.

Figure 1: Zener diode characteristics

The forward bias region of a Zener diode is identical to that of a regular diode. The

typical forward voltage at room temperature with a current of around 1 mA is around 0.6

Volts. In the reverse bias condition the Zener diode is an open circuit and only a small

leakage current is flowing as shown on the exaggerated plot. As the breakdown voltage

is approached the current will begin to avalanche. The initial transition from leakage to

breakdown is soft but then the current rapidly increases as shown on the plot. The

voltage across the Zener diode in the breakdown region is very nearly constant with only

a small increase in voltage with increasing current. At some high current level the power

dissipation of the diode becomes excessive and the part is destroyed. There is a

minimum Zener current, IZmin, that places the operating point in the desired breakdown

Zener Diode Voltage Regulators bregion and there is a maximum Zener current, IZmax,

at which the power dissipation drives the junction temperature to the maximum allowed

(typically in the 125 to 150 C range). Beyond that current and the diode can be damaged

or destroyed.

There is no specific value for IZmin although it is typically taken to be ten percent of

IZmax.

It is possible that a lower value could be used particularly at Zener voltages greater than

around six. This insures that the diode operating current is in the breakdown region and

not in the soft transition region. The ten percent value is also a historical rule-of-thumb

for shunt voltage regulators in general. A shunt regulator has to conduct current in order

to be in regulation. To prevent the current from going to zero, shunt regulators are often

designed so that at the maximum load current there is at least ten percent of that current

in the regulator.

Zener diodes are available from about 2.4 to 200 volts typically using the same sequence

of values as used for the 5% resistor series –2.4, 2.7, 3.0 3.3, 3.6, 3.9, 4.3, 4.7, 5.1, 5.6,

6.2, 6.8, 7.5, 8.2, 9.1, 10, 11, 12, 13, 15, 16, 18, 20, 22, 24, etc.

All Zener diodes have a power rating, PZ. From Watt’s law the maximum current is

IZmax = PZ / VZ. Zener diodes are typically available with power ratings of 0.25, 0.4,

0.5,

1, 2, 3, and 5 watts although other values are available.

The purpose of a voltage regulator is to maintain a constant voltage across a load

regardless of variations in the applied input voltage and variations in the load current. A

typical Zener diode shunt regulator is shown in Figure 2. The resistor is sized so that

When the input voltage is at VINmin and the load current is at ILmax that the current

through

the Zener diode is at least IZmin. Then for all other combinations of input voltage and

load

current the Zener diode conducts the excess current thus maintaining a constant voltage

across the load. The Zener conducts the least current when the load current is the highest

and it conducts the most current when the load current is the lowest.

Figure 2: Zener diode shunt regulator

Shunt regulators are normally only used for applications where the load power is not

much (no more than a few watts) because under the worst case situation of no load the

Zener has to dissipate the full load power. Shunt regulators have an inherent current

Zener Diode Voltage Regulators

limiting advantage under load fault conditions because the series resistor limits excess

current.

Design

The following data must be known in order to design a voltage regulator using a Zener

diode.

VZ The desired regulated voltage rounded to the closest available Zener diode

standard voltage.

VINmin The minimum value of the applied input voltage. This must be higher

than VZ, preferably at least twenty-five percent higher.

VINmax The maximum value of the applied input voltage.

ILmin The minimum value of load current which is often taken to be zero.

ILmax The maximum value of load current.

The design method will use the above data to determine the required power rating of the

Zener and the ohmic value and required power rating of the series resistor, R. This is

often an iterative process as with many design processes.

1. Estimate the power rating of the Zener by the equation

[(VINmax –VZ)

PZest = [(------------------) * (1.1 * ILmax)] –ILmin * VZ

[(VINmin –VZ )

Round the result up to the nearest higher available power rating, PZ. This is only

a trial value and may have to be increased depending on the outcome of the

following calculations. This estimate comes from substituting IZmin = 0.1 IZmax

from step 2 into step 3 and then the resulting unrounded R into step 5.

2. Compute IZmin = 0.1 * maximum(PZ / VZ, ILmax).

3. Calculate Rcalc = (VINmin –VZ) / (ILmax + IZmin).

4. Round Rcalc down (never up) to the nearest standard value, R.

5. Calculate the worst case (i.e. highest) power dissipation in the Zener at the

Minimum load current (typically zero) as

PZmax = [((VINmax –VZ) / R) - ILmin] * VZ.

Zener Diode Voltage Regulators

6. If Puma exceeds PZ then repeat steps 2 through 5 using the next higher available

Power rating for the Zener voltage.

7. Calculate the maximum power dissipation of R as Rdiss = (VINmax –VZ)2 / R.

Common practice is to roughly double this power value and round up to the

nearest standard resistor rating. However, depending on the environment an even

higher power rating might be required –that is thermal design which is separate

From this article.

Light-emitting diode.

Parts of an LED. Although not directly labeled, the flat bottom surfaces of the anvil and

post embedded inside the epoxy act as anchors, to prevent the conductors from being

forcefully pulled out from mechanical strain or vibration.

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps

in many devices and are increasingly used for other lighting. Introduced as a practical electronic

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

across the visible, ultraviolet and infrared wavelengths, with very high brightness.

When a light-emitting diode is forward biased (switched on), electrons are able to recombine with

electron holes within the device, releasing energy in the form of photons. This effect is called

electroluminescence and the color of the light (corresponding to the energy of the photon) is

determined by the energy gap of the semiconductor. An LED is often small in area (less than

1 mm2), and integrated optical components may be used to shape its radiation pattern. LEDs

present many advantages over incandescent light sources including lower energy consumption,

longer lifetime, improved robustness, smaller size, faster switching, and greater durability and

reliability. LEDs powerful enough for room lighting are relatively expensive and require more

precise current and heat management than compact fluorescent lamp sources of comparable

output.

Light-emitting diodes are used in applications as diverse as replacements for aviation lighting,

automotive lighting (particularly brake lamps, turn signals and indicators) as well as in traffic

signals. The compact size, the possibility of narrow bandwidth, switching speed, and extreme

reliability of LEDs has allowed new text and video displays and sensors to be developed, while

their high switching rates are also useful in advanced communications technology. Infrared LEDs

are also used in the remote control units of many commercial products including televisions, DVD

players, and other domestic appliances.

Practical use

The first commercial LEDs were commonly used as replacements for incandescent and

neon indicator lamps, and in seven-segment displays, first in expensive equipment such

as laboratory and electronics test equipment, then later in such appliances as TVs, radios,

telephones, calculators, and even watches (see list of signal uses). These red LEDs were

bright enough only for use as indicators, as the light output was not enough to illuminate

an area. Readouts in calculators were so small that plastic lenses were built over each

digit to make them legible. Later, other colors grew widely available and also appeared in

appliances and equipment. As LED materials technology grew more advanced, light

output rose, while maintaining efficiency and reliability at acceptable levels. The

invention and development of the high power white light LED led to use for illumination,

which is fast replacing incandescent and fluorescent lighting. (see list of illumination

applications). Most LEDs were made in the very common 5 mm T1¾ and 3 mm T1

packages, but with rising power output, it has grown increasingly necessary to shed

excess heat to maintain reliability, so more complex packages have been adapted for

efficient heat dissipation. Packages for state-of-the-art high power LEDs bear little

resemblance to early LEDs.

Technology

The inner workings of an LED

I-V diagram for a diode. An LED will begin to emit light when the on-voltage is

exceeded. Typical on voltages are 2–3 volts

LED development began with infrared and red devices made with gallium arsenide.

Advances in materials science have enabled making devices with ever-shorter

wavelengths, emitting light in a variety of colors.

LEDs are usually built on an n-type substrate, with an electrode attached to the p-type

layer deposited on its surface. P-type substrates, while less common, occur as well. Many

commercial LEDs, especially GaN/InGaN, also use sapphire substrate.

Most materials used for LED production have very high refractive indices. This means

that much light will be reflected back into the material at the material/air surface

interface. Thus, light extraction in LEDs is an important aspect of LED production,

subject to much research and development.

Lifetime and failure

Solid state devices such as LEDs are subject to very limited wear and tear if operated at

low currents and at low temperatures. Many of the LEDs made in the 1970s and 1980s

are still in service today. Typical lifetimes quoted are 25,000 to 100,000 hours but heat

and current settings can extend or shorten this time significantly.

Types

LEDs are produced in a variety of shapes and sizes. The 5 mm cylindrical package (red,

fifth from the left) is the most common, estimated at 80% of world production The color

of the plastic lens is often the same as the actual color of light emitted, but not always.

For instance, purple plastic is often used for infrared LEDs, and most blue devices have

clear housings. There are also LEDs in SMT packages, such as those found on blinkies

and on cell phone keypads (not shown).

The main types of LEDs are miniature, high power devices and custom designs such as

alphanumeric or multi-color.

Application-specific variations

Flashing LEDs are used as attention seeking indicators without requiring external

electronics. Flashing LEDs resemble standard LEDs but they contain an

integrated multivibrator circuit which causes the LED to flash with a typical

period of one second. In diffused lens LEDs this is visible as a small black dot.

Most flashing LEDs emit light of one color, but more sophisticated devices can

flash between multiple colors and even fade through a color sequence using RGB

color mixing.

Calculator LED display, 1970s.

Bi-color LEDs are actually two different LEDs in one case. They consist of two

dies connected to the same two leads anti parallel to each other. Current flow in

one direction emits one color, and current in the opposite direction emits the other

color. Alternating the two colors with sufficient frequency causes the appearance

of a blended third color. For example, a red/green LED operated in this fashion

will color blend to emit a yellow appearance.

Tri-color LEDs are two LEDs in one case, but the two LEDs are connected to

separate leads so that the two LEDs can be controlled independently and lit

simultaneously. A three-lead arrangement is typical with one common lead

(anode or cathode).RGB LEDs contain red, green and blue emitters, generally

using a four-wire connection with one common lead (anode or cathode). These

LEDs can have either common positive or common negative leads. Others

however, have only two leads (positive and negative) and have a built in tiny

electronic control unit.

Alphanumeric LED displays are available in seven-segment and starburst format.

Seven-segment displays handle all numbers and a limited set of letters. Starburst

displays can display all letters. Seven-segment LED displays were in widespread

use in the 1970s and 1980s, but rising use of liquid crystal displays, with their

lower power needs and greater display flexibility, has reduced the popularity of

numeric and alphanumeric LED displays.

Advantages

Efficiency: LEDs emit more light per watt than incandescent light bulbs. Their

efficiency is not affected by shape and size, unlike fluorescent light bulbs or

tubes.

Color: LEDs can emit light of an intended color without using any color filters as

traditional lighting methods need. This is more efficient and can lower initial

costs.

Size: LEDs can be very small (smaller than 2 mm2) and are easily populated onto

printed circuit boards.

On/Off time: LEDs light up very quickly. A typical red indicator LED will

achieve full brightness in under a microsecond. LEDs used in communications

devices can have even faster response times.

Cycling: LEDs are ideal for uses subject to frequent on-off cycling, unlike

fluorescent lamps that fail faster when cycled often, or HID lamps that require a

long time before restarting.

Dimming: LEDs can very easily be dimmed either by pulse-width modulation or

lowering the forward current.

Cool light: In contrast to most light sources, LEDs radiate very little heat in the

form of IR that can cause damage to sensitive objects or fabrics. Wasted energy is

dispersed as heat through the base of the LED.

Slow failure: LEDs mostly fail by dimming over time, rather than the abrupt

failure of incandescent bulbs.

Lifetime: LEDs can have a relatively long useful life. One report estimates

35,000 to 50,000 hours of useful life, though time to complete failure may be

longer. Fluorescent tubes typically are rated at about 10,000 to 15,000 hours,

depending partly on the conditions of use, and incandescent light bulbs at 1,000–

2,000 hours.

Shock resistance: LEDs, being solid state components, are difficult to damage

with external shock, unlike fluorescent and incandescent bulbs which are fragile.

Focus: The solid package of the LED can be designed to focus its light.

Incandescent and fluorescent sources often require an external reflector to collect

light and direct it in a usable manner.

Disadvantages

High initial price: LEDs are currently more expensive, price per lumen, on an

initial capital cost basis, than most conventional lighting technologies. The

additional expense partially stems from the relatively low lumen output and the

drive circuitry and power supplies needed.

Temperature dependence: LED performance largely depends on the ambient

temperature of the operating environment. Over-driving an LED in high ambient

temperatures may result in overheating the LED package, eventually leading to

device failure. Adequate heat sinking is needed to maintain long life. This is

especially important in automotive, medical, and military uses where devices

must operate over a wide range of temperatures, and need low failure rates.

Voltage sensitivity: LEDs must be supplied with the voltage above the threshold

and a current below the rating. This can involve series resistors or current-

regulated power supplies.[90]

Light quality: Most cool-white LEDs have spectra that differ significantly from a

black body radiator like the sun or an incandescent light. The spike at 460 nm and

dip at 500 nm can cause the color of objects to be perceived differently under

cool-white LED illumination than sunlight or incandescent sources, due to

metamerism, red surfaces being rendered particularly badly by typical phosphor

based cool-white LEDs. However, the color rendering properties of common

fluorescent lamps are often inferior to what is now available in state-of-art white

LEDs

Area light source: LEDs do not approximate a “point source” of light, but rather

a lambertian distribution. So LEDs are difficult to apply to uses needing a

spherical light field. LEDs cannot provide divergence below a few degrees. In

contrast, lasers can emit beams with divergences of 0.2 degrees or less.

Blue hazard: There is a concern that blue LEDs and cool-white LEDs are now

capable of exceeding safe limits of the so-called blue-light hazard as defined in

eye safety specifications such as ANSI/IESNA RP-27.1–05: Recommended

Practice for Photobiological Safety for Lamp and Lamp Systems.

Applications

LED lighting in the aircraft cabin of an Airbus A320 Enhanced.

A large LED display behind a disc jockey.

LED destination signs on buses, one with a colored route number.

LED digital display that can display 4 digits along with points.

CERAMIC CAPACITOR

in electronics, a ceramic capacitor is a capacitor constructed of alternating layers

of metal and ceramic, with the ceramic material acting as the dielectric. The temperature

coefficientdepends on whether the dielectric is Class 1 or Class 2. A ceramic capacitor

(especially the class 2) often has high dissipation factor, high frequency coefficient of

dissipation.

Construction

A ceramic capacitor is a two-terminal, non-polar device. The classical ceramic capacitor

is the "disc capacitor". This device pre-dates the transistor and was used extensively in

vacuum-tube equipment (e.g., radio receivers) from about 1930 through the 1950s, and in

discrete transistor equipment from the 1950s through the 1980s. As of 2007, ceramic disc

capacitors are in widespread use in electronic equipment, providing high capacity and

small size at low price compared to other low value capacitor types.

Ceramic capacitors come in various shapes and styles, including:

disc, resin coated, with through-hole leads

multilayer rectangular block, surface mount

bare leadless disc, sits in a slot in the PCB and is soldered in place, used for UHF

applications

tube shape, not popular now

CLASSES OF CERAMIC CAPACITOR

Class I capacitors: accurate, temperature-compensating capacitors. They are the most

stable over voltage, temperature, and to some extent, frequency. They also have the

lowest losses. On the other hand, they have the lowest volumetric efficiency. A typical

class I capacitor will have a temperature coefficient of 30 ppm/°C. This will typically be

fairly linear with temperature. These also allow for high Q filters—a typical class I

capacitor will have a dissipation factor of 0.15%. Very high accuracy (~1%) class I

capacitors are available (typical ones will be 5% or 10%). The highest accuracy class 1

capacitors are designated C0G or NP0.

Class II capacitors: better volumetric efficiency, but lower accuracy and stability. A

typical class II capacitor may change capacitance by 15% over a −55 °C to 85 °C

temperature range. A typical class II capacitor will have a dissipation factor of 2.5%. It

will have average to poor accuracy (from 10% down to +20/-80%).

Class III capacitors: high volumetric efficiency, but poor accuracy and stability. A

typical class III capacitor will change capacitance by -22% to +56% over a temperature

range of 10 °C to 55 °C. It will have a dissipation factor of 4%. It will have fairly poor

accuracy (commonly, 20%, or +80/-20%). These are typically used for decoupling or in

other power supply applications.

At one point, Class IV capacitors were also available, with worse electrical characteristics

than Class III, but even better volumetric efficiency. They are now rather rare and

considered obsolete, as modern multilayer ceramics can offer better performance in a

compact package.

These correspond roughly to low K, medium K, and high K. Note that none of the classes

are "better" than any others—the relative performance depends on application. Class I

capacitors are physically larger than class III capacitors, and for bypassing and other non-

filtering applications, the accuracy, stability, and loss factor may be unimportant, while

cost and volumetric efficiency may be. As such, Class I capacitors are primarily used in

filtering applications, where the main competition is from film capacitors in low

frequency applications, and more esoteric capacitors in RF applications. Class III

capacitors are typically used in power supply applications. Traditionally, they had no

competition in this niche, as they were limited to small sizes. As ceramic technology has

improved, ceramic capacitors are now commonly available in values of up to 100 µF, and

they are increasingly starting to compete.

With electrolytic capacitors, where ceramics offer much better electrical performance at

prices that, while still much higher than electrolytic, are becoming increasingly

reasonable as the technology improves.

ELECTROLYTIC CAPACITOR

An electrolytic capacitor is a type of capacitor that uses an electrolyte, an ionic

conducting liquid, as one of its plates, to achieve a larger capacitance per unit volume

than other types. They are often referred to in electronics usage simply as "electrolytics".

They are used in relatively high-current and low-frequency electrical circuits, particularly

in power supply filters, where they store charge needed to moderate output voltage and

current fluctuations in rectifier output. They are also widely used as coupling capacitors

in circuits where AC should be conducted but DC should not. There are two types of

electrolytics; aluminum and tantalum.

Electrolytic capacitors are capable of providing the highest capacitance values of any

type of capacitor but they have drawbacks which limit their use. The standard design

requires that the applied voltage must be polarized; one specified terminal must always

have positive potential with respect to the other. Therefore they cannot be used with AC

signals without a DC polarizing bias. However there are special non-polarized

electrolytic capacitors for AC use which do not require a DC bias. Electrolytic capacitors

also have relatively low breakdown voltage, higher leakage current and inductance,

poorer tolerances and temperature range, and shorter lifetimes compared to other types of

capacitors.

The principle of the electrolytic capacitor was discovered in 1886 by Charles Pollak, as

part of his research into anodizing of aluminum and other metals. Pollack discovered that

due to the thinness of the aluminum oxide layer produced, there was a very high

capacitance between the aluminum and the electrolyte solution. A major problem was

that most electrolytes tended to dissolve the oxide layer again when the power is

removed, but he eventually found that sodium perborate (borax) would allow the layer to

be formed and not attack it afterwards. He was granted a patent for the borax-solution

aluminum electrolytic capacitor in 1897.

The first application of the technology was in making starting capacitors for single-phase

alternating current (AC) motors. Although most electrolytic capacitors are polarized, that

is, they can only be operated with direct current (DC), by separately anodizing aluminum

plates and then interleaving them in a borax bath, it is possible to make a capacitor that

can be used in AC systems.

Nineteenth and early twentieth century electrolytic capacitors bore little resemblance to

modern types, their construction being more along the lines of a car battery. The borax

electrolyte solution had to be periodically topped up with distilled water, again

reminiscent of a lead acid battery.

The first major application of DC versions of this type of capacitor was in large telephone

exchanges, to reduce relay hash (noise) on the 48 volt DC power supply. The

development of AC-operated domestic radio receivers in the late 1920s created a demand

for large capacitance (for the time) high voltage capacitors, typically at least 4

microfarads and rated at around 500 volts DC. Waxed paper and oiled silk capacitors

were available but devices with that order of capacitance and voltage rating were bulky

and prohibitively expensive.

Construction

Aluminum electrolytic capacitors are constructed from two conducting aluminum foils,

one of which is coated with an insulating oxide layer, and a paper spacer soaked in

electrolyte. The foil insulated by the oxide layer is the anode while the liquid electrolyte

and the second foil acts as the cathode. This stack is then rolled up, fitted with pin

connectors and placed in a cylindrical aluminum casing. The two most popular

geometries are axial leads coming from the center of each circular face of the cylinder, or

two radial leads or lugs on one of the circular faces. Both of these are shown in the

picture.

Polarity

In aluminum electrolytic capacitors, the layer of insulating aluminum oxide on the

surface of the aluminum plate acts as the dielectric, and it is the thinness of this layer that

allows for a relatively high capacitance in a small volume. This oxide has a dielectric

constant of 10, which is several times higher than most common polymer insulators. It

can withstand an electric field strength of the order of 25 megavolts per meter which is an

acceptable fraction of that of common polymers. This combination of high capacitance

and reasonably high voltage result in high energy density.

Most electrolytic capacitors are polarized and require one of the electrodes to be positive

relative to the other; they may catastrophically fail if voltage is reversed. This is because

a reverse-bias voltage above 1 to 1.5 V will destroy the center layer of dielectric material

via electrochemical reduction (see redox reactions). Following the loss of the dielectric

material, the capacitor will short circuit, and with sufficient short circuit current, the

electrolyte will rapidly heat up and either leak or cause the capacitor to burst, often in

spectacularly dramatic fashion.

To minimize the likelihood of a polarized electrolytic being incorrectly inserted into a

circuit, polarity is very clearly indicated on the case. A bar across the side of the capacitor

is usually used to indicate the negative terminal. Also, the negative terminal lead of a

radial electrolytic is shorter than the positive lead and may be otherwise distinguishable.

On a printed circuit board it is customary to indicate the correct orientation by using a

square through-hole pad for the positive lead and a round pad for the negative.

Special capacitors designed for AC operation are available, usually referred to as "non-

polarized" or "NP" types. In these, full-thickness oxide layers are formed on both the

aluminum foil strips prior to assembly. On the alternate halves of the AC cycles, one of

the foil strips acts as a blocking diode, preventing reverse current from damaging the

electrolyte of the other one.

Modern capacitors have a safety valve, typically either a scored section of the can, or a

specially designed end seal to vent the hot gas/liquid, but ruptures can still be dramatic.

An electrolytic can withstand a reverse bias for a short period, but will conduct

significant current and not act as a very good capacitor. Most will survive with no reverse

DC bias or with only AC voltage, but circuits should be designed so that there is not a

constant reverse bias for any significant amount of time.

CapacitorPolarizedCapacitor

VariableCapacitor

The above are the most common schematic symbols for electrolytic capacitors. Some

schematic diagrams do not print the "+" adjacent to the symbol. Older circuit diagrams

show electrolytic capacitors as a small positive plate surrounded below and on the sides

by a larger dish-shaped negative electrode, usually without "+" marking.

Electrolyte

The electrolyte is usually boric acid or sodium borate in aqueous solution, together with

various sugars or ethylene glycol which are added to retard evaporation. Getting a

suitable balance between chemical stability and low internal electrical resistance is not a

simple matter; in fact, the exact compositions of high-performance electrolytes are

closely guarded trade secrets. It took many years of painstaking research before reliable

devices were developed. The electrolytic solvent has to have high dielectric constant,

high dielectric strength, and low resistivity; a solute of ionic conductivity facilitators is

mixed within.

Electrolytes may be toxic or corrosive. Working with the electrolyte requires safe

working practice and appropriate protective equipment such as gloves and safety glasses.

Some very old tantalum electrolytics, often called "Wet-slug", contain corrosive sulfuric

acid; however, most of these are no longer in service due to corrosion.

There are three major types of water-based electrolytes for aluminium electrolytic

capacitors: standard water-based (with 40-70% water), and those containing ethylene

glycol or dipropyl ketone (both with less than 25% water). The water content helps

lowering the equivalent series resistance, but can make the capacitor prone to generating

gas, especially if the electrolyte formulation is faulty; this is a leading cause of capacitor

plague, to which the high water content electrolytes are more susceptible. The lower

voltage ratings (thinner oxide layer) and lower operating voltage (slower regeneration of

oxide layer) are further aggravating factors.

There are a number of non-aqueous electrolytes, which use only a small amount of

water. The electrolytes are generally composed of a weak acid, a salt of weak acid, and a

solvent, and optional thickening agent and other additives. The electrolyte is usually

soaked into an electrode separator. The weak acids are usually organic acid (glacial acetic

acid, lactic acid, propionic acid, butyric acid, crotonic acid, acrylic acid, phenol, cresol,

etc.) or boric acid. The salts employed are often ammonium or metal salts of organic

acids (ammonium acetate, ammonium citrate, aluminium acetate, calcium lactate,

ammonium oxalate, etc.) or weak inorganic acids (sodium perborate, trisodium

phosphate, etc.). Solvent-based electrolytes may be based on alkanolamines

(monoethanolamine, diethanolamine, triethanolamine,...) or polyols (diethylene glycol,

glycerol, etc.).

Electrical behavior of electrolytics

A common modeling circuit for an electrolytic capacitor has the following schematic:

where Rleakage is the leakage resistance, RESR is the equivalent series resistance (ESR), LESL

the equivalent series inductance (L being the conventional symbol for inductance).

RESR must be as small as possible since it determines the loss power when the capacitor is

used to smooth voltage. Loss power varies with the square of the ripple current flowing

through it and proportionally to RESR. Low ESR capacitors are imperative for high

efficiencies in power supplies. Low ESR capacitance can sometimes lead to destructive

LC voltage spikes when exposed to voltage transients.

This is only a simple model and does not include dielectric absorption (soakage) and

other non-ideal effects associated with real electrolytic capacitors.

Capacitance

The capacitance value of any capacitor is a measure of the amount of electric charge

stored per unit of potential difference between the plates. The basic unit of capacitance is

a farad; however, this unit has been too large for general use until the invention of the

double-layer capacitor, so microfarad (μF, or less correctly uF), nanofarad (nF) and

picofarad (pF) are more commonly used.

Many conditions determine a capacitor's value, such as the thickness of the dielectric and

the plate area. In the manufacturing process, electrolytic capacitors are made to conform

to a set of preferred numbers. By multiplying these base numbers by a power of ten, any

practical capacitor value can be achieved, which is suitable for most applications.

Passive electronic components, including capacitors, are usually produced in preferred

values (e.g., IEC 60063 E6, E12, etc. series).

The capacitance of aluminum electrolytic capacitors tends to change over time, and they

usually have a tolerance range of 20%. Some have asymmetric tolerances, typically

−20% but with much larger positive tolerance as many circuits merely require a

capacitance to be not less than a given value; this can be seen on datasheets for many

consumer-grade capacitors. Tantalum electrolytics can be produced to tighter tolerances

and are more stable.

Types

Electrolytic capacitors of several sizes

Unlike capacitors that use a bulk dielectric made from an intrinsically insulating material,

the dielectric in electrolytic capacitors depends on the formation and maintenance of a

microscopic metal oxide layer. Compared to bulk dielectric capacitors, this very thin

dielectric allows for much more capacitance in the same unit volume, but maintaining the

integrity of the dielectric usually requires the steady application of the correct polarity of

voltage or the oxide layer will break down and rupture, causing the capacitor to lose its

ability to withstand applied voltage (although it can often be "reformed"). In addition,

electrolytic capacitors generally use an internal wet chemistry and they will eventually

fail if the water within the capacitor evaporates.

Electrolytic capacitance values are not as tightly-specified as with bulk dielectric

capacitors. Especially with aluminum electrolytics, it is quite common to see an

electrolytic capacitor specified as having a "guaranteed minimum value" and no upper

bound on its value. For most purposes (such as power supply filtering and signal

coupling), this type of specification is acceptable.

As with bulk dielectric capacitors, electrolytic capacitors come in several varieties:

Aluminum electrolytic capacitor: compact but lossy, these are available in the range of

<1 µF to 1 F with working voltages up to several hundred volts DC. The dielectric is a thin

layer of aluminum oxide. They contain corrosive liquid and can burst if the device is

connected backwards. The oxide insulating layer will tend to deteriorate in the absence

of a sufficient rejuvenating voltage, and eventually the capacitor will lose its ability to

withstand voltage if voltage is not applied. A capacitor to which this has happened can

often be "reformed" by connecting it to a voltage source through a resistor and allowing

the resulting current to slowly restore the oxide layer.[9] Bipolar electrolytics (also called

Non-Polarised or NP capacitors) contain two capacitors connected in series opposition

and are used when one electrode can be either positive or negative relative to the other

at different instants. Bad frequency and temperature characteristics make them

unsuited for high-frequency applications. Typical ESL values are a few nanohenries.

Tantalum: compact, low-voltage devices up to several hundred µF, these have a lower

energy density and are produced to tighter tolerances than aluminum electrolytics.

Tantalum capacitors are also polarized because of their dissimilar electrodes. The

cathode electrode is formed of sintered tantalum grains, with the dielectric

electrochemically formed as a thin layer of oxide. The thin layer of oxide and high

surface area of the porous sintered material gives this type a very high capacitance per

unit volume. The cathode electrode is formed either of a liquid electrolyte connecting

the outer can or of a chemically deposited semi-conductive layer of manganese dioxide,

which is then connected to an external wire lead. A development of this type replaces

the manganese dioxide with a conductive plastic polymer (polypyrrole) that reduces

internal resistance and eliminates a self-ignition failure.[11]

Compared to aluminum electrolytics, tantalum capacitors have very stable capacitance,

little DC leakage, and very low impedance at high frequencies. However, unlike

aluminum electrolytics, they are intolerant of positive or negative voltage spikes and are

destroyed (often exploding violently) if connected in the circuit backwards or exposed to

spikes above their voltage rating.

Tantalum capacitors are more expensive than aluminum-based capacitors and generally

only available in low-voltage versions, but because of their smaller size for a given

capacitance and lower impedance at high frequencies they are popular in miniature

applications such as cellular telephones.

RELIABILITY AND LENGTH OF LIFE

Aluminum, and to a lesser extent tantalum, electrolytics have worse noise, leakage, drift

with temperature and ageing, dielectric absorption, and inductance than other types of

capacitor. Additionally, low temperature is a problem for most aluminum capacitors: for

most types, capacitance falls off rapidly below room temperature while dissipation factor

can be ten times higher at −25 °C than at 25 °C. Most limitations can be traced to the

electrolyte. At high temperature, the water can be lost to evaporation, and the capacitor

(especially the small sizes) may leak outright. At low temperatures, the conductance of

the salts declines, raising the ESR, and the increase in the electrolyte's surface tension can

cause reduced contact with the dielectric. The conductance of electrolytes generally has a

very high temperature coefficient, +2%/°C is typical, depending on size. The electrolyte,

particularly if degraded, is implicated in various reliability issues as well.

High-quality aluminum electrolytics (computer-grade) have better performance and life

than consumer-grade parts. High temperatures and ripple currents shorten life. Typical

basic electrolytics are rated to work at temperatures up to 85 °C, and are rated for a

worst-case life of about 2000 hours (a year is about 9000 hours); commonly available

higher-temperature units are available for temperatures of 105 °C, and a working

temperature of 175 °C is possible. One of the effects of ageing is an increase in ESR;

some circuits can malfunction due to a capacitor with correct capacitance but elevated

ESR, although a capacitance meter will not find any fault (an ESR meter will). Runaway

failure is possible if increased ESR increases heat dissipation and temperature.

Since the electrolytes evaporate, design life is most often rated in hours at a set

temperature, for example, 2000 hours at 105 °C, which is the highest commonly used

working temperature, although parts working up to 175 °C are available. Standard

inexpensive consumer-grade electrolytic capacitors are rated for 85 °C maximum

working temperature. Life in the operational environment is dictated by the Law of

Arrhenius, which dictates that the capacitor life is a function of temperature and DC

voltage. As a rule of thumb, the life doubles for each 10 °C lower operating temperature.

In our example, it reaches 15 years at 45 °C (for caps rated at 105 °C). The operating

temperature however is not just the ambient temperature. Ripple currents can increase it

significantly. The actual operating temperature is a complex function of ambient

temperature, air speed, ripple current frequency and amplitude, and also affected by

material thermal resistance and the surface area of the can case.[14] In general, high

amplitude ripple currents shorten the life expectancy, whereas low frequency ripple is

more detrimental than high frequency. The EIA IS-749 is a standard for testing

electrolytic capacitor life.

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 newbies. 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.

Fig-1 : Connection Diagram

The connection diagram is shown below. The component details with cost is also with

this. 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. If

anyone want to reduce the volume of the circuit then insert a resistance () 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 got 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. UM

66

Points of importance:

1. Never connect the IC in reverse supply connection.

2. The music depends on the part number of the IC .

3. The transistor are should be connected in proper pin configuration.

4. The recommended power supply is battery of 3 volt.

5. The speaker and resistance has no terminal polarity and connection

points can be interchanged

Modifications

1. For supply voltage difference.

The IC positive point should be biased with potential divider such that the voltage at the

positive in should not exceed 2.5 volt. For example it should be 68k and 10k and the

terminal voltage will be 1.82 volt. Sometimes the IC is supplied only through a very high

value series resistance like 220k from 12 volt, but the output bias current of the IC will

not be sufficient then to drive and works as a signal and can only be driven through

preamplifier or using Darlington pair/Zhikli pair as buffer.

2. To limit speaker current/reduce volume.

The speaker current can be limited using series resistance in blue line such that the base

current as well as collector current (i. e. Speaker current also). The formula is R=(Vcc-

Vee)-.05*[ratio of potential divider if used]*b/Ispk. Ispk=Speaker Current, b= hFE of

the transistor

3.to Increase volume/Protection of Transistor.

The current carrying capacity can be increased using Darlington pair with power

transistor to increase volume.

PHOTOTRANSISTORS

Like diodes, all transistors are light-sensitive. Phototransistors are designed specifically

to take advantage of this fact. The most-common variant is an NPN bipolar transistor

with an exposed base region. Here, light striking the base replaces what would ordinarily

be voltage applied to the base -- so, a phototransistor amplifies variations in the light

striking it. Note that phototransistors may or may not have a base lead (if they do, the

base lead allows you to bias the phototransistor's light response.

For phototransistor selection and comparison information, see the phototransistor section

of the BEAM Reference Library's BEAM Pieces collection.

Note that photodiodes also can provide a similar function, although with much lower gain

(i.e., photodiodes allow much less current to flow than do phototransistors). You can use

this diagram to help you see the difference (both circuits are equivalent):

For an illuminating comparison of the various photo-sensitive devices, make sure to

check out "Choosing the Detector for your Unique Light Sensing Application."

PHOTOTRANSISTOR FREQUENCY RESPONSE

All silicon photosensors (phototransistors, etc.) respond to the entire visible radiation

range as well as to infrared. In fact, all diodes, transistors, Darlingtons, triacs, etc. have

the same basic radiation frequency response. This response peaks in the infrared range.

This is why manufacturers offer infrared-emitting diodes. Their goal is to maximize the

signal-to-noise ratio, by using an emitter with the best match to the phototransistor

response. However, note the response is very broad and virtually any light source will

work.

Basically, a phototransistor can be any bipolar transistor with a transparent case. There

are some variations provide advantages. For example, a focusing lens can be built into the

case for directional sensitivity. Coatings can be applied to block some higher or lower

wavelengths. The transistor itself may provide higher gain, or higher frequency, or lower

capacitance, etc.

The diagram above illustrates the frequency response of silicon phototransistor junctions,

along with the spectral output of an infrared LED.

A PHOTOTRANSISTOR EXPERIMENT

As an experiment, remove the metal top on a fairly large power transistor. You should

use a hacksaw or Dremel tool. Cut carefully around the transistor until you can lift the

metal top off the transistor.

Don't destroy what's inside the case! This is the silicon chip and it is what you need for

this experiment.

Connect your current-reading meter to two of the transistor terminals. Set the meter to a

low current value, say, a few milliamps. Then shine a strong flashlight directly into the

exposed chip. Or, better yet, place the chip and meter hookup in direct hot sunshine.

You should see a current reading on the meter. If not, change your meter leads to two

other terminals on the transistor. In some cases, you may need to use a small flame as a

light source, such as a kitchen match or candle.

The reason for suggesting strong sunlight or a small flame is that when light of the proper

wavelength hits a semiconductor material such as a PN or NP junction, it increases the

concentration of charge carriers. Bright sunlight has both visible and infrared frequencies

over a wide spectrum, and a burning object (such as a match) also radiates visible and

infrared frequencies.

How It Works

The actual operation of a phototransistor depends on the biasing arrangement and light

frequency. For instance, if a PN junction is forward biased, the increased current through

the junctions due to incident light will be relatively insignificant. On the other hand, if the

same junction is reverse biased, the increase in current flow will be considerable and is a

function of the light intensity. Therefore, reverse bias is the normal mode of operation.

Now, if the PN junction is the collector-base diode of a bipolar transistor, the light-

induced current effectively replaces the base current. The physical base lead of the

transistor can be left as an open terminal, or it can be used to bias up to a steady state

level. It is the nature of transistors that a change in base current can cause a significant

change (increase) in collor current. Thus, light stimulation causes a change in base

current, which in turn causes a bigger increase in collector current and, considering the

current gain (hfe), a rather large increase at that.

LM386 (AUDIO FREQUENCY 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

from 20 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 milliwatts when

operating from a 6 volt supply, making the LM386 ideal for battery operation.

APPLICATION HINTS

GAIN CONTROL

To make the LM386 a more versatile amplifier, two pins (1and 8) are provided for gain

control. With pins 1 and 8 open the 1.35 kΩ resistor sets the gain at 20 (26 dB). If a

capacitor is put from pin 1 to 8, bypassing the 1.35 kΩ resistor, the gain will go up to 200

(46 dB). If a resistor is placed in series with the capacitor, the gain can be set to any value

from 20 to 200. Gain control can also be done by capacitively coupling a resistor (or

FET) from pin 1 to ground. Additional external components can be placed in parallel

with the internal feedback resistors to tailor the gain and frequency response for

individual applications. For example, we can compensate poor speaker bass response by

frequency shaping the feedback path. This is done with a series RC from pin 1 to 5

(paralleling the internal 15 kΩ resistor). For 6 dB effective bass boost: R . 15 kΩ, the

lowest value for good stable operation is R = 10 kΩ if pin 8 is open. If pins 1 and 8 are

bypassed then R as low as 2 kΩ can be used. This restriction is because the amplifier is

only compensated for closed-loop gains greater than 9.

INPUT BIASING

The schematic shows that both inputs are biased to ground with a 50 kΩ resistor. The

base current of the input transistors is about 250 nA, so the inputs are at about 12.5 Mv

when left open. If the dc source resistance driving the LM386 is higher than 250 kΩ it

will contribute very little additional offset (about 2.5 mV at the input, 50 mV at the

output). If the dc source resistance is less than 10 kΩ, then shorting the unused input to

ground will keep the offset low (about 2.5 mV at the input, 50 mV at the output). For dc

source resistances between these values we can eliminate excess offset by putting a

resistor from the unused input to ground, equal in

value to the dc source resistance. Of course all offset problems are eliminated if the input

is capacitively coupled. When using the LM386 with higher gains (bypassing the 1.35 kΩ

resistor between pins 1 and 8) it is necessary to bypass the unused input, preventing

degradation of gain and possible instabilities. This is done with a 0.1 µF capacitor or a

short to ground depending on the dc source resistance on the driven input.

FEATURES

1. Battery operation

2. Minimum external parts

3. Wide supply voltage range: 4V–12V or 5V–18V

4. Low quiescent current drain: 4mA

5. Voltage gains from 20 to 200

6. Ground referenced input

7. Self-centering output quiescent voltage

8.Available in 8 pin MSOP package

APPLICATIONS

1. AM-FM radio amplifiers

2. Portable tape player amplifiers

3. Intercoms

4. TV sound systems

5. Line drivers

6. Ultrasonic drivers

7. Small servo drivers

8. Power converter

LM741 OPERATIONAL AMPLIFIER

General Description

The 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: 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.

Features

Short-Circuit Protection

Offset-Voltage Null Capability

Large Common-Mode and Differential Voltage Ranges

No Frequency Compensation Required

Low Power Consumption

No Latch-Up

Designed to Be Interchangeable With Fairchild uA741

WORKING PROCEDURE

Using this circuit, audio musical notes can be generated and heard up to a distance of 10

metres. 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. First diagram 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 photo-transistor L14F1 (T3). The IR music receiver uses popular op-amp IC µA741 and

audio-frequency amplifier IC LM386 along with photo-transistor L14F1 and some

discrete component.

The melody generated by IC UM66 is transmitted through IR LEDs, received by

phototransistor received by phototransistor T3 and fed to pin 2 of IC µA741 (IC2). Its

gain can be varied using potmeter VR1. The output of IC µA741 is fed to IC LM386 (IC3)

via capacitor C5 and potmeter VR2. The melody produced is heard through the

receiver’s loudspeaker. Potmeter VR2 is used to control the volume of loudspeaker LS1

(8-ohm, 1W). Switching off the power supply stops melody generation.

RESULT

Assemble the circuit on the bread board and general board. After assembling the

circuit on the boards check it for proper connections before switching on the power

supply.

The implementation of IR MUSIC TRANSMITTER AND RECEIVER is done

successfully. The communication is properly done without any interference between

different modules in the design. Design is done to meet all the specifications and

requirements.

It can be concluded that the design implemented in the present work provide portability,

flexibility and the data transmission is also done with low power consumption.