CLAP SWITCH

1. ABSTRACT
This involves the design of various sages consisting of the pickup transducer frequency, audio
low power and low noise amplifier, timer, bistable and switches. It also consists of special
network components to prevent false triggering and ensure desired performance objectives. A
decade counter IC serves the bistable function instead of flip-flop, special transistor and edge
triggering network for low audio frequency. This is the circuit of a very sensitive clap switch. It
switches ON/OFF a White LED or electrical appliances through claps. The circuit can sense the
sound of claps from a distance of 1-2 meters. Condenser Mic picks up sound vibrations caused
by the clap. These sound vibrations are given to the inverting input (pin2) of IC1.It amplifies the
sound collected by the Mic. Resistor R1, R3 and variable resistor VR1 adjust the sensitivity of
the amplifier. Resistor R1 set the sensitivity of Mic. The amplified output pulses from IC1 passes
to the input of IC2 (CD 4017).Resistor R4 keeps the input (pin14) of IC2 low so as to prevent
false triggering. IC2 is a decade counter IC which is wired as a toggle switch. That its outputs 1
and 2 (pins 2 and 3) becomes high and low when the input pin14 receives pulses. Pin4 (output4)
is connected to the reset pin15 so that further counting will be inhibited. The high output from
IC2 passes through the current limiter R6 to the base of switching transistor T1. When T1
conducts, White LED (D2) turns on. If a 6V 100 ohms relay is connected to the points marked
(A and B), the relay will also energize and the load (bulb or electrical equipments) will be
switched on. In the next clap, output pin 2 becomes low and relay and White LED will be
switched off. LED D1 (Red LED) indicates the OFF position.
1

2. 2
CHAPTER-1
INTRODUCTION
The primary purpose of switch is to provide means for connecting two or more terminals in order
to permit the flow of current across them, so as to allow for interaction between electrical
components, and to easily isolate circuits so as to terminate this communication flow when need
be. The motivating force behind this design is based on the desire to alleviate the problem faced
by the aged and physically challenged persons in trying to control some household appliances. It
also takes into considerations the illiterates that may have problems operating some “complex”
hand-held Remote Control Units (RCUs)
Therefore this paper provides an introductory study on the basic principles involved in utilizing
acoustic energy to control switching process. This is achieved by converting the energy
generated by the “handclap” into electrical pulse, which is in turn used to drive an electronic
circuitry that includes a relay, which in turn switches ON/OFF any appliance connected through
it to the main.
The device is activated by clapping twice within a set time period that is determinedby a time
constant (RC) component value in the circuit
1.1 BASIC DESIGN ELEMENTS
CLAP ACTIVATED SWITCH
The clap activated switching device can basically be described as a low frequency sound pulse
activated switch that is free from false triggering. The input component is a transducer that
receives clap sound as input and converts it to electrical pulse. This pulse is amplified and used
to drive IC components which changes output state to energize and also de-energize a relay
causing the device to be able to switch larger devices and circuits. The output state of the
switching device circuit can only change, when the circuit receives two claps within a time
period that will be determined by the RC component value in the circuit.
The transducer (microphone) is connected to an amplifier sub-circuit which is connected to timer
ICs . These timer ICs are wired as monostable multi vibrators and their output is used to drive a
decade counter IC that is wired as bi-stable to drive the relay.
This is the circuit of a very sensitive clap switch. It switches ON/OFF a White LED or electrical
appliances through claps. The circuit can sense the sound of claps from a distance of 1-2 meters.

3. Condenser Mic picks up sound vibrations caused by the clap. These sound vibrations are given to
the inverting input (pin2) of IC1.It amplifies the sound collected by the Mic. Resistor R1, R3 and
variable resistor VR1 adjust the sensitivity of the amplifier. Resistor R1 set the sensitivity of
Mic. The amplified output pulses from IC1 passes to the input of IC2 (CD 4017).Resistor R4
keeps the input (pin14) of IC2 low so as to prevent false triggering. IC2 is a decade counter IC
which is wired as a toggle switch. That its outputs 1 and 2 (pins 2 and 3) becomes high and low
when the input pin14 receives pulses. Pin4 (output4) is connected to the reset pin15 so that
further counting will be inhibited. The high output from IC2 passes through the current limiter
R6 to the base of switching transistor T1. When T1 conducts, White LED (D2) turns on. If a 6V
100 ohms relay is connected to the points marked (A and B), the relay will also energize and the
load (bulb or electrical equipments) will be switched on. In the next clap, output pin 2 becomes
low and relay and White LED will be switched off. LED D1 (Red LED) indicates the OFF
position
Fig. 1.1 clap switch
3

4. 4
CHAPTER-2
CAPACITOR
2.1 CAPACITOR
This article is about the electronic component. For the physical phenomenon, see capacitance.
For an overview of various kinds of capacitors, see types of capacitor.
Fig 2.1 Modern capacitors, by a cm rule
Fig. 2.2 A typical electrolytic capacitor
A capacitor (formerly known as condenser) is a passive electronic component consisting of a pair
of conductors separated by a dielectric (insulator). When there is a potential difference (voltage)
across the conductors, a static electric field develops in the dielectric that stores energy and
produces a mechanical force between the conductors. An ideal capacitor is characterized by a
single constant value, capacitance, measured in farads. This is the ratio of the electric charge on
each conductor to the potential difference between them.Capacitors are widely used in electronic

5. circuits for blocking direct current while allowing alternating current to pass, in filter networks,
for smoothing the output of power supplies, in the resonant circuits that tune radios to particular
frequencies and for many other purposes.
The effect is greatest when there is a narrow separation between large areas of conductor, hence
capacitor conductors are often called "plates", referring to an early means of construction. In
practice the dielectric between the plates passes a small amount of leakage current and also has
an electric field strength limit, resulting in a breakdown voltage, while the conductors and leads
introduce an undesired inductance and resistance.
5
2.2 HISTORY
Fig. 2.3 Battery of four Leyden jars in Museum Boerhaave, Leiden, the Netherlands.
In October 1745, Ewald Georg von Kleist of Pomerania in Germany found that charge could be
stored by connecting a high voltage electrostatic generator by a wire to a volume of water in a
hand-held glass jar.[1] Von Kleist's hand and the water acted as conductors and the jar as a
dielectric (although details of the mechanism were incorrectly identified at the time). Von Kleist
found, after removing the generator, that touching the wire resulted in a painful spark. In a letter
describing the experiment, he said "I would not take a second shock for the kingdom of France."

6. The following year, the Dutch physicist Pieter van Musschenbroek invented a similar capacitor,
which was named the Leyden jar, after the University of Leiden where he worked.
Daniel Gralath was the first to combine several jars in parallel into a "battery" to increase the
charge storage capacity. Benjamin Franklin investigated the Leyden jar and "proved" that the
charge was stored on the glass, not in the water as others had assumed. He also adopted the term
"battery", (denoting the increasing of power with a row of similar units as in a battery of
cannon), subsequently applied to clusters of electrochemical cells. Leyden jars were later made
by coating the inside and outside of jars with metal foil, leaving a space at the mouth to prevent
arcing between the foils. The earliest unit of capacitance was the 'jar', equivalent to about 1
nanofarad. Leyden jars or more powerful devices employing flat glass plates alternating with foil
conductors were used exclusively up until about 1900, when the invention of wireless (radio)
created a demand for standard capacitors, and the steady move to higher frequencies required
capacitors with lower inductance. A more compact construction began to be used of a flexible
dielectric sheet such as oiled paper sandwiched between sheets of metal foil, rolled or folded into
a small package.Early capacitors were also known as condensers, a term that is still occasionally
used today. The term was first used for this purpose by Alessandro Volta in 1782, with reference
to the device's ability to store a higher density of electric charge than a normal isolated
conductor.
6
2.3 THEORY OF OPERATION
Charge separation in a parallel-plate capacitor causes an internal electric field. A dielectric
(orange) reduces the field and increases the capacitance.
Fig. 2.4 A simple demonstration of a parallel-plate capacitor

7. A capacitor consists of two conductors separated by a non-conductive region called the dielectric
medium though it may be a vacuum or a semiconductor depletion region chemically identical to
the conductors. A capacitor is assumed to be self-contained and isolated, with no net electric
charge and no influence from any external electric field. The conductors thus hold equal and
opposite charges on their facing surfaces and the dielectric develops an electric field. In SI units,
a capacitance of one farad means that one coulomb of charge on each conductor causes a voltage
of one volt across the device. The capacitor is a reasonably general model for electric fields
within electric circuits. An ideal capacitor is wholly characterized by a constant capacitance C,
defined as the ratio of charge ±Q on each conductor to the voltage V between them
Sometimes charge build-up affects the capacitor mechanically, causing its capacitance to vary. In
this case, capacitance is defined in terms of incremental changes:
7
2.4 ENERGY STORAGE
Work must be done by an external influence to "move" charge between the conductors in a
capacitor. When the external influence is removed the charge separation persists in the electric
field and energy is stored to be released when the charge is allowed to return to its equilibrium
position. The work done in establishing the electric field, and hence the amount of energy stored,
is given by:
2.5 CURRENT-VOLTAGE RELATION
The current i(t) through any component in an electric circuit is defined as the rate of flow of a
charge q(t) passing through it, but actual charges, electrons, cannot pass through the dielectric

8. layer of a capacitor, rather an electron accumulates on the negative plate for each one that leaves
the positive plate, resulting in an electron depletion and consequent positive charge on one
electrode that is equal and opposite to the accumulated negative charge on the other. Thus the
charge on the electrodes is equal to the integral of the current as well as proportional to the
voltage as discussed above. As with any antiderivative, a constant of integration is added to
represent the initial voltage v (t0). This is the integral form of the capacitor equation,
8
.
Taking the derivative of this, and multiplying by C, yields the derivative form,[13]
.
The dual of the capacitor is the inductor, which stores energy in the magnetic field rather than the
electric field. Its current-voltage relation is obtained by exchanging current and voltage in the
capacitor equations and replacing C with the inductance L.
2.6 DC CIRCUITS
See also: RC circuit
A simple resistor-capacitor circuit demonstrates charging of a capacitor.
A series circuit containing only a resistor, a capacitor, a switch and a constant DC source of
voltage V0 is known as a charging circuit. If the capacitor is initially uncharged while the switch
is open, and the switch is closed at t = 0, it follows from Kirchhoff's voltage law that

9. Taking the derivative and multiplying by C, gives a first-order differential equation,
At t = 0, the voltage across the capacitor is zero and the voltage across the resistor is V0. The
initial current is then i (0) =V0 /R. With this assumption, the differential equation yields
Where τ0 = RC is the time constant of the system.
As the capacitor reaches equilibrium with the source voltage, the voltage across the resistor and
the current through the entire circuit decay exponentially. The case of discharging a charged
capacitor likewise demonstrates exponential decay, but with the initial capacitor voltage
replacing V0 and the final voltage being zero.
9
2.7 AC CIRCUITS
See also: reactance (electronics) and Impedance, the vector sum of reactance and resistance,
describes the phase difference and the ratio of amplitudes between sinusoidally varying voltage
and sinusoidally varying current at a given frequency. Fourier analysis allows any signal to be
constructed from a spectrum of frequencies, whence the circuit's reaction to the various
frequencies may be found. The reactance and impedance of a capacitor are respectively

10. Where j is the imaginary unit and ω is the angular velocity of the sinusoidal signal. The - j phase
indicates that the AC voltage V = Z I lags the AC current by 90°: the positive current phase
corresponds to increasing voltage as the capacitor charges; zero current corresponds to
instantaneous constant voltage, etc.
Note that impedance decreases with increasing capacitance and increasing frequency. This
implies that a higher-frequency signal or a larger capacitor results in a lower voltage amplitude
per current amplitude—an AC "short circuit" or AC coupling. Conversely, for very low
frequencies, the reactance will be high, so that a capacitor is nearly an open circuit in AC
analysis—those frequencies have been "filtered out".Capacitors are different from resistors and
inductors in that the impedance is inversely proportional to the defining characteristic, i.e.
capacitance.
10
2.8 PARALLEL PLATE MODEL
The simplest capacitor consists of two parallel conductive plates separated by a dielectric with
permittivity ε (such as air). The model may also be used to make qualitative predictions for other
device geometries. The plates are considered to extend uniformly over an area A and a charge
density ±ρ = ±Q/A exists on their surface. Assuming that the width of the plates is much greater
than their separation d, the electric field near the centre of the device will be uniform with the
magnitude E = ρ/ε. The voltage is defined as the line integral of the electric field between the
plates
Solving this for C = Q/V reveals that capacitance increases with area and decreases with
separation
.
The capacitance is therefore greatest in devices made from materials with a high permittivity.

11. Several capacitors in parallel.
2.9 CAPACITOR-ON-IDEAL BEHAVIOUR
Capacitors deviate from the ideal capacitor equation in a number of ways. Some of these, such as
leakage current and parasitic effects are linear, or can be assumed to be linear, and can be dealt
with by adding virtual components to the equivalent circuit of the capacitor. The usual methods
of network analysis can then be applied. In other cases, such as with breakdown voltage, the
effect is non-linear and normal (i.e., linear) network analysis cannot be used, the effect must be
dealt with separately. There is yet another group, which may be linear but invalidate the
assumption in the analysis that capacitance is a constant. Such an example is temperature
dependence.
11
2.10 BREAKDOWN VOLTAGE
Above a particular electric field, known as the dielectric strength Eds, the dielectric in a capacitor
becomes conductive. The voltage at which this occurs is called the breakdown voltage of the
device, and is given by the product of the dielectric strength and the separation between the
conductors,
Vbd = Edsd
The maximum energy that can be stored safely in a capacitor is limited by the breakdown
voltage. Due to the scaling of capacitance and breakdown voltage with dielectric thickness, all
capacitors made with a particular dielectric have approximately equal maximum energy density,
to the extent that the dielectric dominates their volume.
For air dielectric capacitors the breakdown field strength is of the order 2 to 5 MV/m; for mica
the breakdown is 100 to 300 MV/m, for oil 15 to 25 MV/m, and can be much less when other
materials are used for the dielectric. The dielectric is used in very thin layers and so absolute
breakdown voltage of capacitors is limited. Typical ratings for capacitors used for general

12. electronics applications range from a few volts to 100V or so. As the voltage increases, the
dielectric must be thicker, making high-voltage capacitors larger than those rated for lower
voltages. The breakdown voltage is critically affected by factors such as the geometry of the
capacitor conductive parts; sharp edges or points increase the electric field strength at that point
and can lead to a local breakdown. Once this starts to happen, the breakdown will quickly "track"
through the dielectric till it reaches the opposite plate and cause a short circuit.
The usual breakdown route is that the field strength becomes large enough to pull electrons in the
dielectric from their atoms thus causing conduction. Other scenarios are possible, such as
impurities in the dielectric, and, if the dielectric is of a crystalline nature, imperfections in the
crystal structure can result in an avalanche breakdown as seen in semi-conductor devices.
Breakdown voltage is also affected by pressure, humidity and temperature.
12
2.11 EQUIVALENT CIRCUIT
Fig.2.5 Two equivalent circuits of a real capacitor
An ideal capacitor only stores and releases electrical energy, without dissipating any. In reality,
all capacitors have imperfections within the capacitor's material that create resistance. This is
specified as the equivalent series resistance or ESR of a component. This adds a real component
to the impedance:

13. As frequency approaches infinity, the capacitive impedance (or reactance) approaches zero and
the ESR becomes significant. As the reactance becomes negligible, power dissipation approaches
PRMS. = VRMS.² /RESR.Similarly to ESR, the capacitor's leads add equivalent series inductance or
ESL to the component. This is usually significant only at relatively high frequencies. As
inductive reactance is positive and increases with frequency, above a certain frequency
capacitance will be canceled by inductance. High frequency engineering involves accounting for
the inductance of all connections and components.
If the conductors are separated by a material with a small conductivity rather than a perfect
dielectric, then a small leakage current flows directly between them. The capacitor therefore has
a finite parallel resistance, and slowly discharges over time (time may vary greatly depending on
the capacitor material and quality).
13
.

14. 14
CHAPTER-3
LIGHT-EMITTING DIODE
A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps
in many devices, and are increasingly used for lighting. Introduced as a practical electronic
component in 1962, early LEDs emitted low-intensity red light, but modern versions are
available across 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 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.
3.1 HISTORY
DISCOVERIES AND EARLY DEVICES
Green electroluminescence from a point contact on a crystal of SiC recreates H. J. Round's
original experiment from 1907.Electroluminescence was discovered in 1907 by the British

15. experimenter H. J. Round of Marconi Labs, using a crystal of silicon carbide and a cat's-whisker
detector. Russian Oleg Vladimirovich Losev independently reported on the creation of an LED
in 1927. His research was distributed in Russian, German and British scientific journals, but no
practical use was made of the discovery for several decades. Rubin Braunstein of the Radio
Corporation of America reported on infrared emission from gallium arsenide (GaAs) and other
semiconductor alloys in 1955. Braunstein observed infrared emission generated by simple diode
structures using gallium antimonide (GaSb), GaAs, indium phosphide (InP), and silicon-germanium
(SiGe) alloys at room temperature and at 77 kelvin.In 1961, American experimenters
Robert Biard and Gary Pittman working at Texas Instruments, found that GaAs emitted infrared
radiation when electric current was applied and received the patent for the infrared LED.
The first practical visible-spectrum (red) LED was developed in 1962 by Nick Holonyak Jr.,
while working at General Electric Company.[2] Holonyak is seen as the "father of the light-emitting
diode". M. George Craford, a former graduate student of Holonyak, invented the first
yellow LED and improved the brightness of red and red-orange LEDs by a factor of ten in 1972.
In 1976, T.P. Pearsall created the first high-brightness, high efficiency LEDs for optical fiber
telecommunications by inventing new semiconductor materials specifically adapted to optical
fiber transmission wavelengths. Until 1968, visible and infrared LEDs were extremely costly, on
the order of US $200 per unit, and so had little practical use. The Monsanto Company was the
first organization to mass-produce visible LEDs, using gallium arsenide phosphide in 1968 to
produce red LEDs suitable for indicators. Hewlett Packard (HP) introduced LEDs in 1968,
initially using GaAsP supplied by Monsanto. The technology proved to have major uses for
alphanumeric displays and was integrated into HP's early handheld calculators. In the 1970s
commercially successful LED devices at under five cents each were produced by Fairchild
Optoelectronics. These devices employed compound semiconductor chips fabricated with the
planar process invented by Dr. Jean Hoerni at Fairchild Semiconductor. The combination of
planar processing for chip fabrication and innovative packaging methods enabled the team at
Fairchild led by optoelectronics pioneer Thomas Brandt to achieve the needed cost reductions.
These methods continue to be used by LED producers.
15

16. 16
3.2 PRACTICAL USE
Fig. 3.1 Red, yellow and green (unlit) LEDs used in a traffic signal in Sweden.
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 (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.

17. Illustration of Haitz's Law. Light output per LED as a function of production year, note the
logarithmic scale on the vertical axis.
17
CONTINUING DEVELOPMENT
The first high-brightness blue LED was demonstrated by Shuji Nakamura of Nichia Corporation
and was based on InGaN borrowing on critical developments in GaN nucleation on sapphire
substrates and the demonstration of p-type doping of GaN which were developed by Isamu
Akasaki and H. Amano in Nagoya. In 1995, Alberto Barbieri at the Cardiff University
Laboratory (GB) investigated the efficiency and reliability of high-brightness LEDs and
demonstrated a very impressive result by using a transparent contact made of indium tin oxide
(ITO) on (AlGaInP/GaAs) LED. The existence of blue LEDs and high efficiency LEDs quickly
led to the development of the first white LED, which employed a Y3Al5O12:Ce, or "YAG",
phosphor coating to mix yellow (down-converted) light with blue to produce light that appears
white. Nakamura was awarded the 2006 Millennium Technology Prize for his invention. The
development of LED technology has caused their efficiency and light output to rise
exponentially, with a doubling occurring about every 36 months since the 1960s, in a way
similar to Moore's law. The advances are generally attributed to the parallel development of
other semiconductor technologies and advances in optics and material science. This trend is
normally called Haitz's Law after Dr. Roland Haitz. In February 2008, Bilkent university in
Turkey reported 300 lumens of visible light per watt luminous efficacy (not per electrical watt)
and warm light by using nanocrystals. In 2009, researchers from Cambridge University reported
a process for growing gallium nitride (GaN) LEDs on silicon. Epitaxy costs could be reduced by

18. up to 90% using six-inch silicon wafers instead of two-inch sapphire wafers. The team was led
by Colin Humphreys.
18
3.3 TECHNOLOGY
Fig. 3.2 Parts of an LED
Fig. 3.3 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.

19. 19
3.4 ULTRAVIOLET AND BLUE LED
Blue LEDs are based on the wide band gap semiconductors GaN (gallium nitride) and InGaN
(indium gallium nitride). They can be added to existing red and green LEDs to produce the
impression of white light, though white LEDs today rarely use this principle.The first blue LEDs
were made in 1971 by Jacques Pankove (inventor of the gallium nitride LED) at RCA
Laboratories. These devices had too little light output to be of much practical use. In the late
1980s, key breakthroughs in GaN epitaxial growth and p-type doping ushered in the modern era
of GaN-based optoelectronic devices. Building upon this foundation, in 1993 high brightness
blue LEDs were demonstrated. By the late 1990s, blue LEDs had become widely available. They
have an active region consisting of one or more InGaN quantum wells sandwiched between
thicker layers of GaN, called cladding layers. By varying the relative InN-GaN fraction in the
InGaN quantum wells, the light emission can be varied from violet to amber. AlGaN aluminium
gallium nitride of varying AlN fraction can be used to manufacture the cladding and quantum
well layers for ultraviolet LEDs, but these devices have not yet reached the level of efficiency
and technological maturity of the InGaN-GaN blue/green devices. If the active quantum well
layers are GaN, instead of alloyed InGaN or AlGaN, the device will emit near-ultraviolet light
with wavelengths around 350–370 nm. Green LEDs manufactured from the InGaN-GaN system
are far more efficient and brighter than green LEDs produced with non-nitride material
systems.With nitrides containing aluminium, most often AlGaN and AlGaInN, even shorter
wavelengths are achievable. Ultraviolet LEDs in a range of wavelengths are becoming available
on the market. Near-UV emitters at wavelengths around 375–395 nm are already cheap and often
encountered, for example, as black light lamp replacements for inspection of anti-counterfeiting
UV watermarks in some documents and paper currencies. Shorter wavelength diodes, while
substantially more expensive, are commercially available for wavelengths down to 247 nm. As
the photosensitivity of microorganisms approximately matches the absorption spectrum of DNA,
with a peak at about 260 nm, UV LED emitting at 250–270 nm are to be expected in prospective
disinfection and sterilization devices. Recent research has shown that commercially available
UVA LEDs (365 nm) are already effective disinfection and sterilization devices. Deep-UV
wavelengths were obtained in laboratories using aluminium nitride (210 nm), boron nitride
(215 nm) and diamond (235 nm).

20. 20
3.5 WHITE LIGHT
There are two primary ways of producing high intensity white-light using LEDs. One is to use
individual LEDs that emit three primary colors red, green, and blue—and then mix all the colors
to form white light. The other is to use a phosphor material to convert monochromatic light from
a blue or UV LED to broad-spectrum white light, much in the same way a fluorescent light bulb
works.Due to metamerism, it is possible to have quite different spectra that appear white.

21. 21
CHAPTER-4
POTENTIOMETER
A potentiometer (colloquially known as a "pot") is a three-terminal resistor with a sliding contact
that forms an adjustable voltage divider. If only two terminals are used (one side and the wiper),
it acts as a variable resistor or rheostat. Potentiometers are commonly used to control electrical
devices such as volume controls on audio equipment. Potentiometers operated by a mechanism
can be used as position transducers, for example, in a joystick.Potentiometers are rarely used to
directly control significant power (more than a watt), since the power dissipated in the
potentiometer would be comparable to the power in the controlled load. Instead they are used to
adjust the level of analog signals (e.g. volume controls on audio equipment), and as control
inputs for electronic circuits. For example, a light dimmer uses a potentiometer to control the
switching of a TRIAC and so indirectly control the brightness of lamps..
4.1 POTENTIOMETER CONSTRUCTION
Fig. 4.1 Potentiometer
Construction of a wire-wound circular potentiometer. The resistive element (1) of the shown
device is trapezoidal, giving a non-linear relationship between resistance and turn angle. The
wiper (3) rotates with the axis (4), providing the changeable resistance between the wiper contact
(6) and the fixed contacts (5) and (9). The vertical position of the axis is fixed in the body (2)
with the ring (7) (below) and the bolt (8) (above).A potentiometer is constructed with a resistive
element formed into an arc of a circle, and a sliding contact (wiper) travelling over that arc. The

22. resistive element, with a terminal at one or both ends, is flat or angled, and is commonly made of
graphite, although other materials may be used. The wiper is connected through another sliding
contact to another terminal. On panel potentiometers, the wiper is usually the center terminal of
three. For single-turn potentiometers, this wiper typically travels just under one revolution
around the contact. "Multiturn" potentiometers also exist, where the resistor element may be
helical and the wiper may move 10, 20, or more complete revolutions, though multiturn
potentimeters are usually constructed of a conventional resistive element wiped via a worm gear.
Besides graphite, materials used to make the resistive element include resistance wire, carbon
particles in plastic, and a ceramic/metal mixture called cermet.One form of rotary potentiometer
is called a String potentiometer. It is a multi-turn potentiometer operated by an attached reel of
wire turning against a spring. It is used as a position transducer.In a linear slider potentiometer, a
sliding control is provided instead of a dial control. The resistive element is a rectangular strip,
not semi-circular as in a rotary potentiometer. Due to the large opening slot or the wiper, this
type of potentiometer has a greater potential for getting contaminated.
Potentiometers can be obtained with either linear or logarithmic relations between the slider
position and the resistance (potentiometer laws or "tapers"). A letter code ("A" taper, "B" taper,
etc.) may be used to identify which taper is intended, but the letter code definitions are variable
over time and between manufacturers.Manufacturers of conductive track potentiometers use
conductive polymer resistor pastes that contain hard wearing resins and polymers, solvents,
lubricant and carbon – the constituent that provides the conductive/resistive properties. The
tracks are made by screen printing the paste onto a paper based phenolic substrate and then
curing it in an oven. The curing process removes all solvents and allows the conductive polymer
to polymerize and cross link. This produces a durable track with stable electrical resistance
throughout its working life.
22
4.2 LINEAR TAPER POTENTIOMETER
A linear taper potentiometer has a resistive element of constant cross-section, resulting in a
device where the resistance between the contact (wiper) and one end terminal is proportional to
the distance between them. Linear taper describes the electrical characteristic of the device, not
the geometry of the resistive element. Linear taper potentiometers are used when an

23. approximately proportional relation is desired between shaft rotation and the division ratio of the
potentiometer; for example, controls used for adjusting the centering of (an analog) cathode-ray
oscilloscope.
23
LOGARITHMIC POTENTIOMETER
A logarithmic taper potentiometer has a resistive element that either 'tapers' in from one end to
the other, or is made from a material whose resistivity varies from one end to the other. This
results in a device where output voltage is a logarithmic function of the mechanical angle of the
potentiometer. Most (cheaper) "log" potentiometers are actually not logarithmic, but use two
regions of different resistance (but constant resistivity) to approximate a logarithmic law. A
logarithmic potentiometer can also be simulated with a linear one and an external resistor. True
logarithmic potentiometers are significantly more expensive. Logarithmic taper potentiometers
are often used in connection with audio amplifiers as human perception of audio volume is
logarithmic.
Fig. 4.2 A high power wirewound potentiometer.
4.3 MEMBRANE POTENTIOMETER
A membrane potentiometer uses a conductive membrane that is deformed by a sliding element to
contact a resistor voltage divider. Linearity can range from 0.5% to 5% depending on the
material, design and manufacturing process. The repeat accuracy is typically between 0.1mm and
1.0mm with a theoretically infinite resolution. The service life of these types of potentiometers is
typically 1 million to 20 million cycles depending on the materials used during manufacturing
and the actuation method; contact and contactless (magnetic) methods are available. Many

24. different material variations are available such as PET(foil), FR4, and Kapton. Membrane
potentiometer manuafacturers offer linear, rotary, and application-specific variations. The linear
versions can range from 9mm to 1000mm in length and the rotary versions range from 0° to
360°(multi-turn), with each having a height of 0.5mm. Membrane potentiometers can be used for
position sensing.
24
4.4 POTENTIOMETER APPLICATIONS
Potentiometers are widely used as user controls, and may control a very wide variety of
equipment functions. The widespread use of potentiometers in consumer electronics has declined
in the 1990s, with digital controls now more common. However they remain in many
applications, such as volume controls and as position sensors.

25. 25
CHAPTER-5
RELAY
A relay is an electrically operated switch. Many relays use an electromagnet to operate a
switching mechanism mechanically, but other operating principles are also used. Relays are used
where it is necessary to control a circuit by a low-power signal (with complete electrical isolation
between control and controlled circuits), or where several circuits must be controlled by one
signal. The first relays were used in long distance telegraph circuits, repeating the signal coming
in from one circuit and re-transmitting it to another. Relays were used extensively in telephone
exchanges and early computers to perform logical operations.A type of relay that can handle the
high power required to directly drive an electric motor is called a contactor.Solid-state relays
control power circuits with no moving parts, instead using a semiconductor device to perform
switching. Relays with calibrated operating characteristics and sometimes multiple operating
coils are used to protect electrical circuits from overload or faults; in modern electric power
systems these functions are performed by digital instruments still called "protective relays".
5.1 BASIC DESIGN AND OPERATION
Fig. 5.1 Simple electromechanical relay

26. Fig. 5.2 Small relay as used in electronics
A simple electromagnetic relay consists of a coil of wire surrounding a soft iron core, an iron
yoke which provides a low reluctance path for magnetic flux, a movable iron armature, and one
or more sets of contacts (there are two in the relay pictured). The armature is hinged to the yoke
and mechanically linked to one or more sets of moving contacts. It is held in place by a spring so
that when the relay is de-energized there is an air gap in the magnetic circuit. In this condition,
one of the two sets of contacts in the relay pictured is closed, and the other set is open. Other
relays may have more or fewer sets of contacts depending on their function. The relay in the
picture also has a wire connecting the armature to the yoke. This ensures continuity of the circuit
between the moving contacts on the armature, and the circuit track on the printed circuit board
(PCB) via the yoke, which is soldered to the PCB.
When an electric current is passed through the coil it generates a magnetic field that attracts the
armature, and the consequent movement of the movable contact(s) either makes or breaks
(depending upon construction) a connection with a fixed contact. If the set of contacts was closed
when the relay was de-energized, then the movement opens the contacts and breaks the
connection, and vice versa if the contacts were open. When the current to the coil is switched off,
the armature is returned by a force, approximately half as strong as the magnetic force, to its
relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in
industrial motor starters. Most relays are manufactured to operate quickly. In a low-voltage
application this reduces noise; in a high voltage or current application it reduces arcing.
When the coil is energized with direct current, a diode is often placed across the coil to dissipate
the energy from the collapsing magnetic field at deactivation, which would otherwise generate a
26

27. voltage spike dangerous to semiconductor circuit components. Some automotive relays include a
diode inside the relay case. Alternatively, a contact protection network consisting of a capacitor
and resistor in series (snubber circuit) may absorb the surge. If the coil is designed to be
energized with alternating current (AC), a small copper "shading ring" can be crimped to the end
of the solenoid, creating a small out-of-phase current which increases the minimum pull on the
armature during the AC cycle. A solid-state relay uses a thyristor or other solid-state switching
device, activated by the control signal, to switch the controlled load, instead of a solenoid. An
optocoupler (a light-emitting diode (LED) coupled with a photo transistor) can be used to isolate
control and controlled circuits.
27
5.2 TYPES
LATCHING RELAY
Latching relay, dust cover removed, showing pawl and ratchet mechanism. The ratchet operates
a cam, which raises and lowers the moving contact arm, seen edge-on just below it. The moving
and fixed contacts are visible at the left side of the image.A latching relay has two relaxed states
(bistable). These are also called "impulse", "keep", or "stay" relays. When the current is switched
off, the relay remains in its last state. This is achieved with a solenoid operating a ratchet and
cam mechanism, or by having two opposing coils with an over-center spring or permanent
magnet to hold the armature and contacts in position while the coil is relaxed, or with a remanent
core. In the ratchet and cam example, the first pulse to the coil turns the relay on and the second
pulse turns it off. In the two coil example, a pulse to one coil turns the relay on and a pulse to the
opposite coil turns the relay off. This type of relay has the advantage that it consumes power only
for an instant, while it is being switched, and it retains its last setting across a power outage. A
remanent core latching relay requires a current pulse of opposite polarity to make it change state.
REED RELAY
A reed relay is a reed switch enclosed in a solenoid. The switch has a set of contacts inside an
evacuated or inert gas-filled glass tube which protects the contacts against atmospheric
corrosion; the contacts are made of magnetic material that makes them move under the influence

28. of the field of the enclosing solenoid. Reed relays can switch faster than larger relays, require
only little power from the control circuit, but have low switching current and voltage ratings.
28
MERCURY-WETTED RELAY
A mercury-wetted reed relay is a form of reed relay in which the contacts are wetted with
mercury. Such relays are used to switch low-voltage signals (one volt or less) where the mercury
reduces the contact resistance and associated voltage drop, for low-current signals where surface
contamination may make for a poor contact, or for high-speed applications where the mercury
eliminates contact bounce. Mercury wetted relays are position-sensitive and must be mounted
vertically to work properly. Because of the toxicity and expense of liquid mercury, these relays
are now rarely used. See also mercury switch.
POLARIZED RELAY
A polarized relay placed the armature between the poles of a permanent magnet to increase
sensitivity. Polarized relays were used in middle 20th Century telephone exchanges to detect
faint pulses and correct telegraphic distortion. The poles were on screws, so a technician could
first adjust them for maximum sensitivity and then apply a bias spring to set the critical current
that would operate the relay.
MACHINE TOOL RELAY
A machine tool relay is a type standardized for industrial control of machine tools, transfer
machines, and other sequential control. They are characterized by a large number of contacts
(sometimes extendable in the field) which are easily converted from normally-open to normally-closed
status, easily replaceable coils, and a form factor that allows compactly installing many
relays in a control panel. Although such relays once were the backbone of automation in such
industries as automobile assembly, the programmable logic controller (PLC) mostly displaced
the machine tool relay from sequential control applications.

29. 29
CONTACTOR RELAY
A contactor is a very heavy-duty relay used for switching electric motors and lighting loads,
although contactors are not generally called relays. Continuous current ratings for common
contactors range from 10 amps to several hundred amps. High-current contacts are made with
alloys containing silver. The unavoidable arcing causes the contacts to oxidize; however, silver
oxide is still a good conductor. Such devices are often used for motor starters. A motor starter is
a contactor with overload protection devices attached. The overload sensing devices are a form
of heat operated relay where a coil heats a bi-metal strip, or where a solder pot melts, releasing a
spring to operate auxiliary contacts. These auxiliary contacts are in series with the coil. If the
overload senses excess current in the load, the coil is de-energized. Contactor relays can be
extremely loud to operate, making them unfit for use where noise is a chief concern.
SOLID-STATE RELAY
Fig. 5.3 Solid state relay, which has no moving parts
A solid state relay (SSR) is a solid state electronic component that provides a similar function to
an electromechanical relay but does not have any moving components, increasing long-term
reliability. With early SSR's, the tradeoff came from the fact that every transistor has a small
voltage drop across it. This voltage drop limited the amount of current a given SSR could handle.
As transistors improved, higher current SSR's, able to handle 100 to 1,200 Amperes, have
become commercially available. Compared to electromagnetic relays, they may be falsely
triggered by transients.

30. 30
SOLID STATE CONTACTOR RELAY
A solid state contactor is a heavy-duty solid state relay, including the necessary heat sink, used
for switching electric heaters, small electric motors and lighting loads; where frequent on/off
cycles are required. There are no moving parts to wear out and there is no contact bounce due to
vibration. They are activated by AC control signals or DC control signals from Programmable
logic controller (PLCs), PCs, Transistor-transistor logic (TTL) sources, or other microprocessor
and microcontroller controls.
BUCHHOLZ RELAY
A Buchholz relay is a safety device sensing the accumulation of gas in large oil-filled
transformers, which will alarm on slow accumulation of gas or shut down the transformer if gas
is produced rapidly in the transformer oil.
FORCED-GUIDED CONTACTS RELAY
A forced-guided contacts relay has relay contacts that are mechanically linked together, so that
when the relay coil is energized or de-energized, all of the linked contacts move together. If one
set of contacts in the relay becomes immobilized, no other contact of the same relay will be able
to move. The function of forced-guided contacts is to enable the safety circuit to check the status
of the relay. Forced-guided contacts are also known as "positive-guided contacts", "captive
contacts", "locked contacts", or "safety relays".
OVERLOAD PROTECTION RELAY
Electric motors need overcurrent protection to prevent damage from over-loading the motor, or
to protect against short circuits in connecting cables or internal faults in the motor windings. One
type of electric motor overload protection relay is operated by a heating element in series with
the electric motor. The heat generated by the motor current heats a bimetallic strip or melts
solder, releasing a spring to operate contacts. Where the overload relay is exposed to the same
environment as the motor, a useful though crude compensation for motor ambient temperature is
provided.

31. 31
5.3 APPLICATIONS
Relays are used to and for:
 Control a high-voltage circuit with a low-voltage signal, as in some types of modems or
audio amplifiers,
 Control a high-current circuit with a low-current signal, as in the starter solenoid of an
automobile,
 Detect and isolate faults on transmission and distribution lines by opening and closing
circuit breakers (protection relays),
 Isolate the controlling circuit from the controlled circuit when the two are at different
potentials, for example when controlling a mains-powered device from a low-voltage
switch. The latter is often applied to control office lighting as the low voltage wires are
easily installed in partitions, which may be often moved as needs change. They may also
be controlled by room occupancy detectors in an effort to conserve energy,
 Logic functions. For example, the boolean AND function is realised by connecting
normally open relay contacts in series, the OR function by connecting normally open
contacts in parallel. The change-over or Form C contacts perform the XOR (exclusive or)
function. Similar functions for NAND and NOR are accomplished using normally closed
contacts. The Ladder programming language is often used for designing relay logic
networks.
o Early computing. Before vacuum tubes and transistors, relays were used as logical
elements in digital computers. See ARRA (computer), Harvard Mark II, Zuse Z2,
and Zuse Z3.
o Safety-critical logic. Because relays are much more resistant than semiconductors
to nuclear radiation, they are widely used in safety-critical logic, such as the
control panels of radioactive waste-handling machinery.
 Time delay functions. Relays can be modified to delay opening or delay closing a set of
contacts. A very short (a fraction of a second) delay would use a copper disk between the
armature and moving blade assembly. Current flowing in the disk maintains magnetic
field for a short time, lengthening release time

32. CONCLUSION
Hereby we would like to conclude that this circuit is very much useful to switch ON and OFF the
household appliances just by clapping hand .This circuit functions on using the sound energy
provided by the clap which is converted into electrical energy by condenser mic .This circuit
turns on and off a light, a fan, a radio, a t.v. etc using this converted electrical energy which is
used to turn on relay (an electronic switch). The clap activated switching device can basically be
described as a low frequency sound pulse activated switch that is free from false triggering. The
input component is a transducer that receives clap sound as input and converts it to electrical
pulse. This pulse is amplified and used to drive IC components which changes output state to
energize and also de-energize a relay causing the device to be able to switch larger devices and
circuits. The output state of the switching device circuit can only change, when the circuit
receives two claps within a time period that will be determined by the RC component value in
the circuit. The transducer (microphone) is connected to an amplifier sub-circuit which is
connected to timer ICs . These timer ICs are wired as monostable multi vibrators and their
output is used to drive a decade counter IC that is wired as bi-stable to drive the relay.
32

33. REFERENCES
[1] http://www.engineersgarage.com/electronic-cricutis/clap-switch
[2] http://www.faadooengineers.com/clap-switch
[3] http://www.wikipedia.org/wiki/Clap switch
[4] http://www.electroschematics.com/840/clap-switch
[5] http://www.slideshare.net/swisis2020/clap-switch
[6] http://www.electronicsproject.org/sound-operated-light
[7] http://www.buildcircuit.com/clap-switch2
[8] http://www.electronicshub.org/clap-switch-circuit-for-devices
[9] http://www.instructables.com/id/Clap-Switch-wall-switch-mountable
[10] http://www.electroschematics.com/5643/sensitive-clap-switch
33

34. LIST OF FIGURE
FIGURE NO. NAME PAGE NO.
1.1 CLAP SWITCH (3)
2.1 MODERN CAPACITORS, BY A CM RULE (4)
2.2 A TYPICAL ELECTROLYTIC CAPACITOR (4)
2.3 BATTERY OF FOUR LEYDEN JARS (5)
2.4 DEMONSTRATION OF A PARALLEL-PLATE CAPACITOR (6)
2.5 TWO EQUIVALENT CIRCUITS OF A REAL CAPACITOR (12)
3.1 R,Y,G LED IN A TRAFFIC SIGNAL IN SWEDEN (16)
3.2 PARTS OF AN LED (18)
3.3 THE INNER WORKINGS OF AN LED (18)
4.1 POTENTIOMETER (21)
4.2 A HIGH POWER WIREWOUND POTENTIOMETER (23)
5.1 SIMPLE ELECTROMECHANICAL RELAY (25)
5.2 SMALL RELAY AS USED IN ELECTRONIC (26)
5.3 RELAY, WHICH HAS NO MOVING PARTS (29)
34