A solar inverter converts the variable direct current (DC) output of solar panels into alternating current (AC) that can power homes or be fed into the electric grid. It is a critical component that allows solar power to be used with standard appliances. This document discusses the operation of solar inverters and solar panels, which use the photovoltaic effect to generate electricity from sunlight and maximize power output through techniques like maximum power point tracking. It also provides an overview of renewable energy sources like wind, hydro, and solar power and their increasing role in energy supply.

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CHAPTER-1
INTRODUCTION
1.1.INTRODUCTION
A solar inverter, or PV inverter, converts the variable direct current (DC) output of a photovoltaic (PV)
solar panel into a utility frequency alternating current (AC) that can be fed into a commercial electrical
grid or used by a local, off-grid electrical network. It is a critical component in a photovoltaic system,
allowing the use of ordinary commercial appliances. Solar inverters have special functions adapted for
use with photovoltaic arrays, including maximum power point tracking and anti-islanding protection.
This circuit based project demonstrates the principle and operation behind the darkness detector. For
example lamps which switch on automatically in the night. Various decoration lights are needed to be
switched on automatically in dark.
The circuit described here is more of a sensor application with a speaker attached to it as output.
However, depending upon the application, user can attach a night lamp or series of small LEDs to the
circuit too.
Constructed around a 555 timer IC and LDR, this darkness detector circuit uses a 9V battery as a
power source along with a couple of passive circuit components: resistance and capacitance.
1.2.AIM OF THE PROJECT:-
Solar home System is a user friendly and effective light source using the sunlight to provide reliable and
cost effective electricity. The Solar Home System is an Ideal light source and a visible solution for
household electrification in rural areas.This project is most useful in our life becouse in this project one
time investment fixed on life time.In future one day non renewable energy will end then we will use to
the renewable energy. Our aim is to design and implement Solar Street Light system to drive a load
using solar energy.

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CHAPTER-2
RENEWABLE ENERGY
2.1.RENEWABLE ENERGY
Renewable energy is generally defined as energy that comes from resources which are naturally
replenished on a human timescale such as sunlight, wind, rain, tides, waves and geothermal heat.
Renewable energy replaces conventional fuels in four distinct areas: electricity generation, hot
water/space heating, motor fuels, and rural (off-grid) energy services.
About 16% of global final energy consumption presently comes from renewable resources, with 10% of
all energy from traditional biomass, mainly used for heating, and 3.4% from hydroelectricity. New
renewables (small hydro, modern biomass, wind, solar, geothermal, and biofuels) account for another
3% and are growing rapidly. At the national level, at least 30 nations around the world already have
renewable energy contributing more than 20% of energy supply. National renewable energy markets are
projected to continue to grow strongly in the coming decade and beyond. Wind power, for example, is
growing at the rate of 30% annually, with a worldwide installed capacity of 282,482 megawatts (MW) at
the end of 2012.
Renewable energy resources exist over wide geographical areas, in contrast to other energy sources,
which are concentrated in a limited number of countries. Rapid deployment of renewable energy and
energy efficiency is resulting in significant energy security, climate change mitigation, and economic
benefits. In international public opinion surveys there is strong support for promoting renewable sources
such as solar power and wind power.
While many renewable energy projects are large-scale, renewable technologies are also suited to rural
and remote areas and developing countries, where energy is often crucial in human development. United
Nations' Secretary-General Ban Ki-moon has said that renewable energy has the ability to lift the
poorest nations to new levels of prosperity.

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Fig-2.1.Wind renewable energy source.
2.2.OVERVIEW;
Fig-2.2 In 2010 renewable energy accounted for 17% of total energy consumption.
Biomass heat accounted for 11%, and hydropower 3%.Global public support for
energy sources, based on a survey by Ipsos (2011).

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Renewable energy flows involve natural phenomena such as sunlight, wind, tides, plant growth, and
geothermal heat, as the International Energy Agency explains:
Renewable energy is derived from natural processes that are replenished constantly. In its various forms,
it derives directly from the sun, or from heat generated deep within the earth. Included in the definition
is electricity and heat generated from solar, wind, ocean, hydropower, biomass, geothermal resources,
and biofuels and hydrogen derived from renewable resources.
Fig-2.3 Global renewable power capacity excluding hydro.
Wind power is growing at the rate of 30% annually, with a worldwide installed capacity of 282,482
megawatts (MW) at the end of 2012, and is widely used in Europe, Asia, and the United States. At the
end of 2012 the photovoltaic (PV) capacity worldwide was 100,000 MW, and PV power stations are
popular in Germany and Italy. Solar thermal power stations operate in the USA and Spain, and the
largest of these is the 354 MW SEGS power plant in the Mojave Desert. The world's largest geothermal
power installation is The Geysers in California, with a rated capacity of 750 MW. Brazil has one of the
largest renewable energy programs in the world, involving production of ethanol fuel from sugar cane,
and ethanol now provides 18% of the country's automotive fuel. Ethanol fuel is also widely available in
the USA.

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As of 2011, small solar PV systems provide electricity to a few million households, and micro-hydro
configured into mini-grids serves many more. Over 44 million households use biogas made in
household-scale digesters for lighting and/or cooking, and more than 166 million households rely on a
new generation of more-efficient biomass cookstoves. United Nations' Secretary-General Ban Ki-moon
has said that renewable energy has the ability to lift the poorest nations to new levels of prosperity.
Fig-2.4 Global public support for energy sources, based on a survey by Ipsos (2011).
Renewable energy resources and significant opportunities for energy efficiency exist over wide
geographical areas, in contrast to other energy sources, which are concentrated in a limited number of
countries. Rapid deployment of renewable energy and energy efficiency, and technological
diversification of energy sources, would result in significant energy security and economic benefits.

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CHAPTER-3
3.1.MAINSTREEM RENEWABLE TECHNOLOGIES:
3.1.1. Wind power:-
Airflows can be used to run wind turbines. Modern utility-scale wind turbines range from around
600 kW to 5 MW of rated power, although turbines with rated output of 1.5–3 MW have become the
most common for commercial use; the power available from the wind is a function of the cube of the
wind speed, so as wind speed increases, power output increases dramatically up to the maximum output
for the particular turbine. Areas where winds are stronger and more constant, such as offshore and high
altitude sites, are preferred locations for wind farms. Typical capacity factors are 20-40%, with values at
the upper end of the range in particularly favourable sites.
3.1.2. Hydropower:-
Hydroelectric energy is a term usually reserved for large-scale hydroelectric dams. The largest of which
is the Three Gorges Dam in China and a smaller example is the Akosombo Dam in Ghana.Micro hydro
systems are hydroelectric power installations that typically produce up to 100 kW of power. They are
often used in water rich areas as a remote-area power supply (RAPS).Run-of-the-river hydroelectricity
systems derive kinetic energy from rivers and oceans without the creation of a large reservoir.
3.1.3. Solar energy:-
Solar energy, radiant light and heat from the sun, is harnessed using a range of ever-evolving
technologies such as solar heating, solar photovoltaics, solar thermal electricity, solar architecture and
artificial photosynthesis.
Solar technologies are broadly characterized as either passive solar or active solar depending on the way
they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic
panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a
building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and
designing spaces that naturally circulate air.

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Solar power is the conversion of sunlight into electricity, either directly using photovoltaics (PV), or
indirectly using concentrated solar power (CSP). Concentrated solar power systems use lenses or mirrors
and tracking systems to focus a large area of sunlight into a small beam. Commercial concentrated solar
power plants were first developed in the 1980s. Photovoltaics convert light into electric current using the
photoelectric effect. Photovoltaics are an important and relatively inexpensive source of electrical
energy where grid power is inconvenient, unreasonably expensive to connect, or simply unavailable.
However, as the cost of solar electricity is falling, solar power is also increasingly being used even in
grid-connected situations as a way to feed low-carbon energy into the grid.
In 2011, the International Energy Agency said that "the development of affordable, inexhaustible and
clean solar energy technologies will have huge longer-term benefits. It will increase countries’ energy
security through reliance on an indigenous, inexhaustible and mostly import-independent resource,
enhance sustainability, reduce pollution, lower the costs of mitigating climate change, and keep fossil
fuel prices lower than otherwise. These advantages are global. Hence the additional costs of the
incentives for early deployment should be considered learning investments; they must be wisely spent
and need to be widely shared".
3.1.4.Solar panel:-
A solar panel is a set of solar photovoltaic modules electrically connected and mounted on a supporting
structure. A photovoltaic module is a packaged, connected assembly of solar cells. The solar panel can
be used as a component of a larger photovoltaic system to generate and supply electricity in commercial
and residential applications. Each module is rated by its DC output power under standard test conditions
(STC), and typically ranges from 100 to 320 watts. The efficiency of a module determines the area of a
module given the same rated output - an 8% efficient 230 watt module will have twice the area of a 16%
efficient 230 watt module. A single solar module can produce only a limited amount of power; most
installations contain multiple modules. A photovoltaic system typically includes a panel or an array of
solar modules, an inverter, and sometimes a battery and/or solar tracker and interconnection wiring.

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3.2.Theory and construction:-
Solar modules use light energy (photons) from the sun to generate electricity through the photovoltaic
effect. The majority of modules use wafer-based crystalline silicon cells or thin-film cells based on
cadmium telluride or silicon. The structural (load carrying) member of a module can either be the top
layer or the back layer. Cells must also be protected from mechanical damage and moisture. Most solar
modules are rigid, but semi-flexible ones are available, based on thin-film cells. These early solar
modules were first used in space in 1958.
Electrical connections are made in series to achieve a desired output voltage and/or in parallel to provide
a desired current capability. The conducting wires that take the current off the modules may contain
silver, copper or other non-magnetic conductive transition metals. The cells must be connected
electrically to one another and to the rest of the system. Externally, popular terrestrial usage photovoltaic
modules use MC3 (older) or MC4 connectors to facilitate easy weatherproof connections to the rest of
the system.
Bypass diodes may be incorporated or used externally, in case of partial module shading, to maximize
the output of module sections still illuminated.
Some recent solar module designs include concentrators in which light is focused by lenses or mirrors
onto an array of smaller cells. This enables the use of cells with a high cost per unit area (such as
gallium arsenide) in a cost-effective way.

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Fig-3.1 Polycrystalline PV cells connected in a solar module.
3.3. Working of Solar Panels:-
Solar panels harness the energy of the sun light and convert it into usable electricity. In this article, we
are going to have a detailed look at the theory behind the basic principle used in solar panels.
Photons are the basic fundamental unit of any form of light energy. The photons that are emitted by the
sun (visible light) are captured by the solar panels. The generation of electricity in the solar panels is
possible because of a principle called as photovoltaic effect.
Photovoltaic effect: This effect is the creation of an electrical voltage or rather the electric current
flowing in a closed loop, here referred to in a solar panel. This process is somewhat related to the
photoelectric effect; although these are different processes altogether. The electrons that are generated
when the solar panels are exposed to a stream of photons are transferred between the different bands of
energy inside the atom to which they are bound. Typically, the transition of the energy state of electrons
takes place from valence band to the conduction band, but within the material that is used in the solar
panels. This transfer of electrons makes them accumulate in order to cause a buildup of voltage between
the two electrodes.

10. 10
There is however another principle that guides the behaviors of solar panels. This refers to p-n junction
solar cells used in solar panels. Here the material which is illuminated by the sun's energy is the source
of current due to the separation of excited electrons and holes that are swept away in the different
directions. This is caused due to the built in electric field of the p-n junction present at the depletion
region.
Solar panels contain a system of solar cells that are interconnected so that they can transfer the induced
voltage/current between one another so that the required parameters can pile up and a suitable
throughout can be obtained. Series connections of solar cells in solar panels help add up the voltage and
the same is true for solar cells connected using parallel connection.
Solar cells are protected from the mechanical damage as well as external factors like dust and moisture
that can be severe to degrade their performance. Solar cells have materials that are mostly rigid. But
when it comes to the thin films, they need extra care as they are available in semi-flexible nature.
It all depends upon how the solar panels are designed and manufactured. These factors help them
produce electricity from a range of frequencies of light. Solar panels cannot be designed practically in
order to capture photons of the entire spectrum of light emitted by the sun. Capabilities of solar panels
that capture rage of frequencies mostly exclude the infrared, ultraviolet etc. and a poor performance is
witnessed in the low or diffused light.
Another fact is that solar panels produce much lesser efficiency as compared to when their basic
components viz. solar cells are used independently without any interconnections. Typically, solar panels
that are available commercially are only able to depict their best efficiency as low as 21%. Due to the
significant impact of efficiency, a number of techniques are used in order to tweak the performance of
solar cells.
Solar cells are designed in conjunction with concentrators which contain lenses or mirrors to focus the
light on to tightly packed and coupled array of solar cells. Although there is an increase in the design
and implementation of the solar panels in terms of high cost per unit area, the basic motto of increase in
efficiency is achieved with least efforts. Thus the science and technology behind solar panels is
increasing by the day and advancement in the same is occurring at a rapid pace.

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Solar cells convert light energy into electrical energy either indirectly by first converting it into heat, or
through a direct process known as the photovoltaic effect. The most common types of solar cells are
based on the photovoltaic effect, which occurs when light falling on a two-layer semiconductor material
produces a potential difference, or voltage, between the two layers. The voltage produced in the cell is
capable of driving a current through an external electrical circuit that can be utilized to power electrical
devices. This tutorial explores the basic concepts behind solar cell operation.
The tutorial initializes at an arbitrarily set "medium" photon intensity level, with photons randomly
impacting the surface of the solar cell to generate free electrons. The released electrons complete a
simple circuit containing two light bulbs that become illuminated when current flows through. In order
to increase or decrease the photon flux, use the Photon Intensity slider to adjust the number of photons
incident on the surface.
Today, the most common photovoltaic cells employ several layers of doped silicon, the same
semiconductor material used to make computer chips. Their function depends upon the movement of
charge-carrying entities between successive silicon layers. In pure silicon, when sufficient energy is
added (for example, by heating), some electrons in the silicon atoms can break free from their bonds in
the crystal, leaving behind a hole in an atom's electronic structure. These freed electrons move about
randomly through the solid material searching for another hole with which to combine and release their
excess energy. Functioning as free carriers, the electrons are capable of producing an electrical current,
although in pure silicon there are so few of them that current levels would be insignificant. However,
silicon can be modified by adding specific impurities that will either increase the number of free
electrons (n-silicon), or the number of holes (missing electrons; also referred to as p-silicon). Because
both holes and electrons are mobile within the fixed silicon crystalline lattice, they can combine to
neutralize each other under the influence of an electrical potential. Silicon that has been doped in this
manner has sufficient photosensitivity to be useful in photovoltaic applications.

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Fig-3.2 Electron and current flow in solar cells
In a typical photovoltaic cell, two layers of doped silicon semiconductor are tightly bonded together
(illustrated in Figure 1). One layer is modified to have excess free electrons (termed an n-layer), while
the other layer is treated to have an excess of electron holes or vacancies (a p-layer). When the two
dissimilar semiconductor layers are joined at a common boundary, he free electrons in the n-layer cross
into the p-layer in an attempt to fill the electron holes. The combining of electrons and holes at the p-n
junction creates a barrier that makes it increasingly difficult for additional electrons to cross. As the
electrical imbalance reaches an equilibrium condition, A fixed electric field results across the boundary
separating the two sides.
When light of an appropriate wavelength (and energy) strikes the layered cell and is absorbed, electrons
are freed to travel randomly. Electrons close to the boundary (the p-n junction) can be swept across the
junction by the fixed field. Because the electrons can easily cross the boundary, but cannot return in the
other direction (against the field gradient), A charge imbalance results between the two semiconductor
regions. Electrons being swept into the n-layer by the localized effects of the fixed field have a natural
tendency to leave the layer in order to correct the charge imbalance. Towards this end, the electrons will
follow another path if one is available. By providing an external circuit by which the electrons can return
to the other layer, a current flow is produced that will continue as long as light strikes the solar cell. In
the construction of a photovoltaic cell, metal contact layers are applied to the outer faces of the two

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semiconductor layers, and provide a path to the external circuit that connects the two layers. The final
result is production of electrical power derived directly from the energy of light.
The voltage produced by solar cells varies with the wavelength of incident light, but typical cells are
designed to use the broad spectrum of daylight provided by the sun. The amount of energy produced by
the cell is wavelength-dependent with longer wavelengths generating less electricity than shorter
wavelengths. Because commonly available cells produce only about as much voltage as a flashlight
battery, hundreds or even thousands must be coupled together in order to produce enough electricity for
demanding applications. A number of solar-powered automobiles have been built and successfully
operated at highway speeds through the use of a large number of solar cells. In 1981, an aircraft known
as the Solar Challenger, which was covered with 16,000 solar cells producing over 3,000 watts of
power, was flown across the English Channel powered solely by sunlight. Feats such as these inspire
interest in expanding the uses of solar power. However, the use of solar cells is still in its infancy, and
these energy sources are still largely restricted to powering low demand devices.
Current photovoltaic cells employing the latest advances in doped silicon semiconductors convert a
average of 18 percent (reaching a maximum of about 25 percent) of the incident light energy into
electricity, compared to about 6 percent for cells produced in the 1950s. In addition to improvements in
efficiency, new methods are also being devised to produce cells that are less expensive than those made
from single crystal silicon. Such improvements include silicon films that are grown on much less
expensive polycrystalline silicon wafers. Amorphous silicon has also been tried with some success, as
has the evaporation of thin silicon films onto glass substrates. Materials other than silicon, such as
gallium arsenide, cadmium telluride, and copper indium diselenide, are being investigated for their
potential benefits in solar cell applications. Recently, titanium dioxide thin films have been developed
for potential photovoltaic cell construction. These transparent films are particularly interesting because
they can also serve double duty as windows.

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3.4. Solar Applications:-
For several years people have been wondering whether solar energy is really worth it, or whether solar
energy really capable of generating enough power compared to the investment that is required. Also
whether the electricity produced with solar power is can really be put to any commercial use? Research
and development teams around the world have become determined to prove that solar energy is really a
viable alternative energy source. As the result many research institutes around the world have come up
with various options that suggest application of solar energy in almost all the basic appliances in our
daily life? In other words researchers around the world have been desperately coming up with various
ideas that suggest applications of solar energy sources.
Following are the application where solar energy can be used as an effective solution to replace fossil
fuel and prove that solar energy is not just a dream.
For thousands of years man has been harnessing the sun’s energy in various forms which makes the
sun’s energy more versatile and a favored form of alternative energy. First of all the sun’s energy is
abundantly available and every day. Therefore it truly is a renewable energy source. Depending on the
period of history, the use of solar energy has varied. Even in the rural area, people make use of heat
energy of the sun to dry clothes and fish. It is also used for heating purposes with the help of solar water
heater. Other domestic applications also include distillation of water. Based on the types of industries
solar applications can be classified in to 3 categories, industrial, agricultural and power.
The industrial applications include solar water pumps that use solar energy to power motors of the
pumps to draw water.
But this application where solar energy is being used to power an airplane is a giant leap forward
towards making solar energy a viable choice of an alternative energy. However due to recent failures
due to inability of the solar energy to generate enough power rendered the crowd of researchers to
believe that the solar energy is a dream concept and is not practical. However now this myth is finally
being broken and new hopes have risen to take solar energy to a next level.
Another application that is used on a much wider scale is the green houses. These houses domes are
covered with a transparent insulating material in order to isolate the inner region of the dome from the

15. 15
temperature and pressure differences in the region outside the dome. This keeps the inner region
unaffected by bad weather, rain or storms thus allowing a perfect habitable condition for plants to thrive.
The recent studies show that if these houses are kept under controlled conditions a self sustaining eco
system can be formed within the dome, no matter where the location of the dome is.
The PV panels used today are much cheaper and are able to absorb light more efficiently. That is why
home appliances such as water heater and cookers have gone solar. The solar water heaters can use the
solar heat energy to provide boiling water for drinking or bathing and also for desalination purposes. For
many years solar energy is also used to keep the fish dry to prevent them from getting spoiled.
An aircraft that could just keep flying indefinitely till it keeps getting solar energy. Imagine a plane
flying around the world without having to make a stop anywhere to refuel. It’s a simple aircraft with
motors propellers and wings except the fact that the entire wing span has its upper portion covered with
thin PV solar panels.

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CHAPTER-4
BLOCK DIAGRAM
4.1. Block Diagram of Solar System:-
Fig-4.1 Block Diagram of Solar System.
4.2. INVERTER:-
Introduction:-
Inverter is a small circuit which will convert the direct current (DC) to alternating current (AC). The
power of a battery is converted in to’ main voltages ‘or AC power. This power can be used for electronic
appliances like television, mobile phones, computer etc. the main function of the inverter is to convert
DC to AC and step-up transformer is used to create main voltages from resulting AC.

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Simple 100W Inverter Circuit Diagram:-
Fig- 4.2 Circuit Diagram of 100W inverter.
In the circuit diagram battery supply is given to the MOSFET driver where it will convert DC to AC and
the resulting AC is given to the step up transformer from the step up transformer we will the get the
original voltage.
4.2.1 Main Components:-
CD4047: CD4047 is a multi vibrator with very low power consumption designed by TEXAS
INSTRUMENTS.it can operate in monostable multivibrator and also astable multivibrator.in the astable
multivibrator mode it can operate in free running or gatable modes and also provides good astable
frequency stability. It can generate 50% duty cycle which will create a pulse, which can be applied for
inverter circuit. This is mainly used in frequency discriminators, timing circuits frequency divisions etc.

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Fig-4.3 IC CD 4047 BE
Fig-4.4 Pin Diagram of IC CD 4047 BE.
IRF540:-
IRF540 is a N-channel enhanced mode silicon gate field effect transistor (MOSFET).they are mainly
used in switching regulators, switching converters relay drivers etc. the reason for using them in the
INVERTER circuit is the because it is a high switching transistor , can work in very low gate drive
power and have high input impedance.

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Fig-4.5 IRF540
IRF540 Symbol:-
Fig-4.6 Symbol of IRF540
4.3. Resistor:-
A resistor is a passive two-terminal electrical component that implements electrical resistance as a
circuit element. Resistors act to reduce current flow, and, at the same time, act to lower voltage levels

20. 20
within circuits. Resistors may have fixed resistances or variable resistances, such as those found in
thermostats, varsities, trimmers, photo resistors and potentiometers.
Resistors are used to limit the value of current in a circuit. Resistors offer opposition to the flow of
current. They are expressed in ohms for which the symbol is ‘’. Resistors are broadly classified as
(1) Fixed Resistors
(2) Variable Resistors
4.3.1. Fixed resistors:-
The most common of low wattage, fixed type resistors is the molded-carbon composition resistor. The
resistive material is of carbon clay composition. The leads are made of tinned copper. Resistors of this
type are readily available in value ranging from few ohms to about 20M, having a tolerance range of 5
to 20%. They are quite inexpensive. The relative size of all fixed resistors changes with the wattage
rating.
Another variety of carbon composition resistors is the metalized type. It is made by deposition a
homogeneous film of pure carbon over a glass, ceramic or other insulating core. This type of film-resistor
is sometimes called the precision type, since it can be obtained with an accuracy of 1%.
Lead Tinned Copper Material
Colour Coding Molded Carbon Clay Composition
4.3.2. A Wire Wound Resistor :-
It uses a length of resistance wire, such as ni chrome. This wire is wounded on to a round hollow
porcelain core. The ends of the winding are attached to these metal pieces inserted in the core. Tinned
copper wire leads are attached to these metal pieces. This assembly is coated with an enamel coating
powdered glass. This coating is very smooth and gives mechanical protection to winding. Commonly
available wire wound resistors have resistance values ranging from 1 to 100K, and wattage rating up
to about 200W.

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The current through a resistor is in direct proportion to the voltage across the resistor's terminals. This
relationship is represented by Ohm's law:
where I is the current through the conductor in units of amperes, V is the potential difference measured
across the conductor in units of volts, and R is the resistance of the conductor in units of ohms (symbol:
Ω).
The ratio of the voltage applied across a resistor's terminals to the intensity of current in the circuit is
called its resistance, and this can be assumed to be a constant (independent of the voltage) for ordinary
resistors working within their ratings.
Resistors are common elements of electrical networks and electronic circuits and are ubiquitous in
electronic equipment. Practical resistors can be composed of various compounds and films, as well as
resistance wires (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 nine 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 sinks. In a high-voltage circuit, attention must
sometimes be paid to the rated maximum working voltage of the resistor. While there is no minimum
working voltage for a given resistor, failure to account for a resistor's maximum rating may cause the
resistor to incinerate when current is run through it.

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Practical resistors have a series inductance and a small parallel capacitance; these specifications can be
important in high-frequency applications. 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
the position of its leads (or terminals) which is relevant in the practical manufacturing of circuits using
them.
Fig- 4.7 Resistors with wire leads for through-hole mounting
Electronic symbols and notation
The symbol used for a resistor in a circuit diagram varies from standard to standard and country to
country. Two typical symbols are as follows;
Fig-4.8 American-style symbols. (a) Resistor, (b) rheostat (variable resistor), an (c) potentiometer

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Fig-4.9 IEC-style resistor symbol
The notation to state a resistor's value in a circuit diagram varies, too. The European notation avoids
using a decimal separator, and replaces the decimal separator with the SI prefix symbol for the particular
value. For example, 8k2 in a circuit diagram indicates a resistor value of 8.2 kΩ. Additional zeros imply
tighter tolerance, for example 15M0. When the value can be expressed without the need for an SI prefix,
an 'R' is used instead of the decimal separator. For example, 1R2 indicates 1.2 Ω, and 18R indicates
18 Ω. The use of a SI prefix symbol or the letter 'R' circumvents the problem that decimal separators
tend to 'disappear' when photocopying a printed circuit diagram.
Units:-
The ohm (symbol: Ω) is the SI unit of electrical resistance, named after Georg Simon Ohm. An ohm is
equivalent to a volt per ampere. Since resistors are specified and manufactured over a very large range
of values, the derived units of milliohm (1 mΩ = 10−3 Ω), kilo ohm (1 kΩ = 103 Ω), and mega ohm (1
MΩ = 106 Ω) are also in common usage.
The reciprocal of resistance R is called conductance G = 1/R and is measured in siemens (SI unit),
sometimes referred to as a mho. Hence, Siemens is the reciprocal of an ohm: . Although the
concept of conductance is often used in circuit analysis, practical resistors are always specified in terms
of their resistance (ohms) rather than conductance.

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4.3.3. Coding Of Resistor:-
The axial lead carbon resistors measured by the color codes marked on them. Information such as
resistance value, tolerance, temperature co-efficient measured by the color codes, and the amount of
power (wattage) identified by the size.
The color bands of the carbon resistors can be four, five or, six bands, for all the first two bands
represent first two digits to measure their value in ohms. The third band of a four-banded resistor
represents multiplier and the fourth band as tolerance. Whereas, the five and six color-banded resistors,
the third band rather represents as third digit but the fourth and fifth bands represent as multiplier and
tolerance respectively. Only the sixth band represents temperature co-efficient in a six-banded resistor.
Some resistors are large enough in size to have their resistance printed on the body. However there are
some resistors that are too small in size to have numbers printed on them. Therefore, a system of color
coding is used to indicate their values. For fixed, mounded composition resistor four color bands are
printed on one end of the outer casing. The color bands are always read left to right from the end that has
the bands closest to it. The first and second band represents the first and second significant digits, of the
resistance value. The third band is for the number of zeros that follow the second digit. In case the third
band is gold or silver, it represents a multiplying factor of 0.1to 0.01. The fourth band represents the
manufacture’s tolerance.
RESISTOR COLOUR CHART
0 black
1 brown
2 red
3 orange
4 yellow
5 green
6 blue
7 purple
8 silver
9 white
0 black
1 brown
2 red
3 orange
4 yellow
6 blue
7 purple
5 green
8 silver
9 white
0 black
1 brown
2 red
3 orange
4 yellow
5 green
6 blue
7 purple
8 silver
9 white
0 black
1 brown
2 red
3 orange
4 yellow
5 green
6 blue
7 purple
8 silver
9 white

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For example, if a resistor has a colour band sequence: yellow, violet, orange and gold
Then its range will be—
Yellow=4, violet=7, orange=10³, gold=±5% =47KΏ ±5% =2.35KΏ
Most resistors have 4 bands:
 The first band gives the first digit.
 The second band gives the second digit.
 The third band indicates the number of zeros.
 The fourth band is used to show the tolerance (precision) of the resistor.
This resistor has red (2), violet (7), yellow (4 zeros) and gold bands.
So its value is 270000 = 270 k .
The standard color code cannot show values of less than 10 . To show these small values two special
colors are used for the third band: gold, which means × 0.1 and silver which means × 0.01. The first and
second bands represent the digits as normal.
For example:-
Red, violet, gold bands represent 27 × 0.1 = 2.7
blue, green, silver bands represent 56 × 0.01 = 0.56
The fourth band of the color code shows the tolerance of a resistor. Tolerance is the precision of the
resistor and it is given as a percentage. For example a 390 resistor with a tolerance of ±10% will have
a value within 10% of 390 , between 390 - 39 = 351 and 390 + 39 = 429 (39 is 10% of 390).

26. 26
A special color code is used for the fourth band tolerance:
silver ±10%, gold ±5%, red ±2%, brown ±1%.
If no fourth band is shown the tolerance is ±20%.
The measuring of digits against color codes given in the following table.
E.g. the value of a four band Carbon resistor having color bands Red, Red, Red, Silver will have value
22*100=2200 ohms with 10% tolerance.

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4.4.CAPACITOR:-
A capacitor or condenser is a passive electronic component consisting of a pair of conductors separated
by a dielectric (insulator). When a potential difference (voltage) exists across the conductors, an electric
field is present in the dielectric. This field stores energy and produces a mechanical force between the
conductors. The effect is greatest when there is a narrow separation between large areas of conductor,
hence capacitor conductors are often called plates.
An ideal capacitor is characterized by a single constant value, capacitance, which is measured in farads.
This is the ratio of the electric charge on each conductor to the potential difference between them. In
practice, the dielectric between the plates passes a small amount of leakage current. The conductors and
leads introduce an equivalent series resistance and the dielectric has an electric field strength limit
resulting in a breakdown voltage.
Capacitors are widely used in electronic circuits to block the flow of direct current while allowing
alternating current to pass, to filter out interference, to smooth the output of power supplies, and for
many other purposes. They are used in resonant circuits in radio frequency equipment to select particular
frequencies from a signal with many frequencies.

28. 28
Theory of operation
Main article: Capacitance
Charge separation in a parallel-plate capacitor causes an internal electric field. A dielectric (orange)
reduces the field and increases the capacitance.
Fig-4.10 A simple demonstration of a parallel-plate capacitor
A capacitor consists of two conductors separated by a non-conductive region. The non-conductive
substance is called the dielectric medium, although this may also mean 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 an external electric field. The conductors thus
contain equal and opposite charges on their facing surfaces, and the dielectric contains an electric field.
The capacitor is a reasonably general model for electric fields within electric circuits.

29. 29
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 buildup affects the mechanics of the capacitor, causing the capacitance to vary. In
this case, capacitance is defined in terms of incremental changes:
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.
4.5 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 and energy is stored in the
electric field. If charge is later allowed to return to its equilibrium position, the energy is released. The
work done in establishing the electric field, and hence the amount of energy stored.
4.6 Heat sink
Fig-4.11 Heat sink
Waste heat is produced in transistors due to the current flowing through them. Heat sinks are needed for
power transistors because they pass large currents. If you find that a transistor is becoming too hot to
touch it certainly needs a heat sink! The heat sink helps to dissipate (remove) the heat by transferring it
to the surrounding air.

30. 30
4.7 LED (LIGHT EMITTING DIODE)
A junction diode, such as LED, can emit light or exhibit electro luminescence. Electro luminescence is
obtained by injecting minority carriers into the region of a pn junction where radioactive transition takes
place. In radioactive transition, there is a transition of electron from the conduction band to the valence
band, which is made possible by emission of a photon. Thus, emitted light comes from the whole
electron recombination. What is required is that electrons should make a transition from higher energy
level to lower energy level releasing photon of wavelength corresponding to the energy difference
associated with this transition. In LED the supply of high-energy electron is provided by forward biasing
the diode, thus injecting electrons into the n-region and holes into p-region.
The pn junction of LED is made from heavily doped material. On forward bias condition, majority
carriers from both sides of the junction cross the potential barrier and enter the opposite side where they
are then minority carrier and cause local minority carrier population to be larger than normal. This is
termed as minority injection. These excess minority carrier diffuse away from the junction and
recombine with majority carriers.
In LED, every injected electron takes part in a irradiative recombination and hence gives rise to an
emitted photon. Under reverse bias no carrier injection takes place and consequently no photon is
emitted. For direct transition from conduction band to valence band the emission wavelength.
In practice, every electron does not take part in radioactive recombination and hence, the efficiency
of the device may be described in terms of the quantum efficiency which is defined as the rate of
emission of photons divided by the rate of supply of electrons. The number of radioactive
recombination, that take place, is usually proportional to the carrier injection rate and hence to the total
current flowing.
4.7.1 LED Materials:
One of the first materials used for LED is GaAs. This is a direct band gap material, i.e., it exhibits very
high probability of direct transition of electron from conduction band to valence band. GaAs has E= 1.44
eV. This works in the infrared region.

31. 31
Gallium Arsenide Phosphide is a tertiary alloy. This material has a special feature in that it changes from
being direct band gap material.
Blue LEDs are of recent origin. The wide band gap materials such as GaN are one of the most promising
LEDs for blue and green emission. Infrared LEDs are suitable for optical coupler applications.
ADVANTAGES OF LEDs:
1. Low operating voltage, current, and power consumption makes Leds compatible with electronic
drive circuits. This also makes easier interfacing as compared to filament incandescent and
electric discharge lamps.
2. The rugged, sealed packages developed for LEDs exhibit high resistance to mechanical shock
and vibration and allow LEDs to be used in severe environmental conditions where other light
sources would fail.
3. LED fabrication from solid-state materials ensures a longer operating lifetime, thereby
improving overall reliability and lowering maintenance costs of the equipment in which they are
installed.
4. The range of available LED colors-from red to orange, yellow, and green-provides the designer
with added versatility.
5. LEDs have low inherent noise levels and also high immunity to externally generated noise.
6. Circuit response of LEDs is fast and stable, without surge currents or the prior “warm-up”,
period required by filament light sources.
7. LEDs exhibit linearity of radiant power output with forward current over a wide range.
LEDs have certain limitations such as:
1. Temperature dependence of radiant output power and wave length.
2. Sensitivity to damages by over voltage or over current.
3. Theoretical overall efficiency is not achieved except in special cooled or pulsed conditions.

32. 32
4.8 DIODE
4.8.1 ACTIVE COMPONENT-Active
component are those component for not any other component are used its operation. I used in this
project only function diode, these component description are described as bellow.
4.8.2 SEMICONDUCTOR DIODE-A
PN junctions is known as a semiconductor or crystal diode.A crystal diode has two terminal when it is
connected in a circuit one thing is decide is weather a diode is forward or reversed biased. There is a
easy rule to ascertain it. If the external CKT is trying to push the conventional current in the direction of
error, the diode is forward biased. One the other hand if the conventional current is trying is trying to
flow opposite the error head, the diode is reversed biased putting in simple words.
1. If arrowhead of diode symbol is positive W.R.T Bar of the symbol, the diode is forward biased.
2. The arrowhead of diode symbol is negative W.R.T bar , the diode is the reverse bias.
3. When we used crystal diode it is often necessary to know that which end is arrowhead and which
end is bar. So following method are available.
4. Some manufactures actually point the symbol on the body of the diode e. g By127 by 11 4
crystal diode manufacture by b e b.

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5. Sometimes red and blue marks are on the body of the crystal diode. Red mark do not arrow
where’s blue mark indicates bar e .g oa80 crystal diode.
4.9 ZENER DIODE-It
has been already discussed that when the reverse bias on a crystal diode is increased a critical voltage,
called break down voltage. The break down or zener voltage depends upon the amount of doping. If the
diode is heavily doped depletion layer will be thin and consequently the break down of he junction will
occur at a lower reverse voltage. On the other hand, a lightly doped diode has a higher break down
voltage, it is called zener diode
A properly doped crystal diode, which has a shaped break down voltage, is known as a zenor diode.
4.10 ADVANTAGES:
 Improved operational efficiencies.
 Reduces financial risks.
 Better customer service.
 Improve accuracy in meter readings.

34. 34
4.11 TRANSFORMER
A transformer is an electrical device that transfers energy between two circuits through electromagnetic
induction. A transformer may be used as a safe and efficient voltage converter to change the AC voltage
at its input to a higher or lower voltage at its output. Other uses include current conversion, isolation
with or without changing voltage and impedance conversion.
A transformer most commonly consists of two windings of wire that are wound around a common core
to provide tight electromagnetic coupling between the windings. The core material is often a laminated
iron core. The coil that receives the electrical input energy is referred to as the primary winding, while
the output coil is called the secondary winding.
An alternating electric current flowing through the primary winding (coil) of a transformer generates a
varying electromagnetic field in its surroundings which causes a varying magnetic flux in the core of the
transformer. The varying electromagnetic field in the vicinity of the secondary winding induces an
electromotive force in the secondary winding, which appears a voltage across the output terminals. If a
load impedance is connected across the secondary winding, a current flows through the secondary
winding drawing power from the primary winding and its power source.
A transformer cannot operate with direct current; although, when it is connected to a DC source, a
transformer typically produces a short output pulse as the current rises.
4.11.1 CURRENT TRANSFORMER
A current transformer is a type of transformer that is usually placed in the main circuit to step down a
high current circuit to drive a low current device, usually a low current meter or resistor. It is also very
useful in measuring or monitoring high current, high voltage and high power circuits.

35. 35
4.11.2. POTENTIAL TRANSFORMER
Fig:-4.12 Three-phase pole-mounted step-down transformer.
A transformer is a device that transfers electrical energy from one circuit to another through inductively
coupled electrical conductors. A changing current in the first circuit (the primary) creates a changing
magnetic field. This changing magnetic field induces a changing voltage in the second circuit (the
secondary). This effect is called mutual induction.
If a load is connected to the secondary circuit, electric charge will flow in the secondary winding
of the transformer and transfer energy from the primary circuit to the load connected in the secondary
circuit.
The secondary induced voltage VS, of an ideal transformer, is scaled from the primary VP by a
factor equal to the ratio of the number of turns of wire in their respective windings:
By appropriate selection of the numbers of turns, a transformer thus allows an alternating voltage
to be stepped up — by making NS more than NP — or stepped down, by making it less.

36. 36
Transformers are some of the most efficient electrical 'machines',[1] with some large units able to transfer
99.75% of their input power to their output.[2] Transformers come in a range of sizes from a thumbnail-sized
coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons
used to interconnect portions of national power grids. All operate with the same basic principles,
although the range of designs is wide.
Fig-4.13 Transformer of 12V-230V
4.11.3 Applications
Transformers perform voltage conversion; isolation protection; and impedance matching. In terms of
voltage conversion, transformers can step-up voltage/step-down current from generators to high-voltage
transmission lines, and step-down voltage/step-up current to local distribution circuits or industrial
customers. The step-up transformer is used to increase the secondary voltage relative to the primary
voltage, whereas the step-down transformer is used to decrease the secondary voltage relative to the
primary voltage. Transformers range in size from thumbnail-sized used in microphones to units
weighing hundreds of tons interconnecting the power grid. A broad range of transformer designs are
used in electronic and electric power applications, including miniature, audio, isolation, high-frequency,
power conversion transformers, etc.

37. 37
4.11.4 Basic principles
The functioning of a transformer is based on two principles of the laws of electromagnetic induction: An
electric current through a conductor, such as a wire, produces a magnetic field surrounding the wire, and
a changing magnetic field in the vicinity of a wire induces a voltage across the ends of that wire.
The magnetic field excited in the primary coil gives rise to self-induction as well as mutual induction
between coils. This self-induction counters the excited field to such a degree that the resulting current
through the primary winding is very small when no load draws power from the secondary winding.
The physical principles of the inductive behavior of the transformer are most readily understood and
formalized when making some assumptions to construct a simple model which is called the ideal
transformer. This model differs from real transformers by assuming that the transformer is perfectly
constructed and by neglecting that electrical or magnetic losses occur in the materials used to construct
the device.
4.11.5. Ideal transformer
Fig-4.14 Ideal transformer with a source and a load. NP and NS are the number of
turns in the primary and secondary windings respectively.
The assumptions to characterize the ideal transformer are:
 The windings of the transformer have no resistance. Thus, there is no copper loss in the winding,
and hence no voltage drop.

38. 38
 Flux is confined within the magnetic core. Therefore, it is the same flux that links the input and
output windings.
 Permeability of the core is infinitely high which implies that net mmf (amp-turns) must be zero
(otherwise there would be infinite flux) hence IP NP - IS NS = 0.
 The transformer core does not suffer magnetic hysteresis or eddy currents, which cause inductive
loss.
If the secondary winding of an ideal transformer has no load, no current flows in the primary winding.
The circuit diagram (right) shows the conventions used for an ideal, i.e. lossless and perfectly-coupled
transformer having primary and secondary windings with NP and NS turns, respectively.
The ideal transformer induces secondary voltage VS as a proportion of the primary voltage VP and
respective winding turns as given by the equation
,
where,
a is the winding turns ratio, the value of these ratios being respectively higher and lower than
unity for step-down and step-up transformers,[4][5][a][b]
VP designates source impressed voltage,
VS designates output voltage, and,
According to this formalism, when the number of turns in the primary coil is greater than the number of
turns in the secondary coil, the secondary voltage is smaller than the primary voltage. On the other hand,
when the number of turns in the primary coil is less than the number of turns in the secondary, the
secondary voltage is greater than the primary voltage.
Any load impedance ZL connected to the ideal transformer's secondary winding allows energy to flow
without loss from primary to secondary circuits. The resulting input and output apparent power are equal
as given by the equation

39. 39
.
Combining the two equations yields the following ideal transformer identity
.
This formula is a reasonable approximation for the typical commercial transformer, with voltage ratio
and winding turns ratio both being inversely proportional to the corresponding current ratio.
The load impedance ZL and secondary voltage VS determine the secondary current IS as follows
.
The apparent impedance ZL' of this secondary circuit load referred to the primary winding circuit is
governed by a squared turns ratio multiplication factor relationship derived as follows[7][8]
.
For an ideal transformer, the power supplied to the primary and the power dissipated by the load are
equal. If ZL = RL where RL is a pure resistance then the power is given by:[9][10]
The primary current is given by the following equation:[9][10]

40. 40
Induction law
A varying electrical current passing through the primary coil creates a varying magnetic field around the
coil which induces a voltage in the secondary winding. The primary and secondary windings are
wrapped around a core of very high magnetic permeability, usually iron,[c] so that most of the magnetic
flux passes through both the primary and secondary coils. The current through a load connected to the
secondary winding and the voltage across it are in the directions indicated in the figure.
Fig-4.15 Ideal transformer and induction law
The voltage induced across the secondary coil may be calculated from Faraday's law of induction, which
states that:
where Vs is the instantaneous voltage, Ns is the number of turns in the secondary coil, and dΦ/dt is the
derivative[d] of the magnetic flux Φ through one turn of the coil. If the turns of the coil are oriented
perpendicularly to the magnetic field lines, the flux is the product of the magnetic flux density B and the
area A through which it cuts. The area is constant, being equal to the cross-sectional area of the
transformer core, whereas the magnetic field varies with time according to the excitation of the primary.

41. 41
Since the same magnetic flux passes through both the primary and secondary coils in an ideal
transformer,[7] the instantaneous voltage across the primary winding equals
Taking the ratio of the above two equations gives the same voltage ratio and turns ratio relationship
shown above, that is,
.
The changing magnetic field induces an emf across each winding.[11] The primary emf, acting as it does
in opposition to the primary voltage, is sometimes termed the counter emf.[12] This is in accordance with
Lenz's law, which states that induction of emf always opposes development of any such change in
magnetic field.
As still lossless and perfectly-coupled, the transformer still behaves as described above in the ideal
transformer
4.12 AUTOMATIC STREET LIGHT SYSTEMS
Automatic street light system block diagram are divided into to part first is
12V-9V DC converter and second part is darkness detector.Which explain are
Given below

42. 42
4.12.1 12V – 9V DC Converter
This is a project of a simple 12V to 9V converter circuit. This DC to DC converter circuit can be used to
convert any 12V DC source to 9V DC. The circuit can also be used to step down or convert any 12 volt
battery power to 9 volt such as car battery. The heart of the circuit is a LM7809 IC. LM7809 is a fixed
voltage regulator IC performs DC to DC step down converter tasks in electronic circuits. The IC has a
lot of built in features like thermal shutdown, short circuit protection and safe operating area protection.
LM7809 is a IC of LM78xx series all the ICs in this series are made for different fixed output voltages
(for example LM7809 IC which is used in this circuit is made for 9 volt fix output, while LM7805
produces 5 volts). These type of ICs are commonly used in regulated power supply circuits.
Fig-4.16 12V DC to 9V DC converter.

43. 43
4.12.2 IC LM 7809
Working of IC LM 7809
7809 is a voltage regulator integrated circuit(IC) which is widely used in electronic circuits. Voltage
regulator circuit can be manually built using parts available in the market but it will take a lot of time to
assemble those parts on a PCB. Secondly, the cost of those parts is almost equal to the price of 7809
itself so professionals usually prefer to use 7809 IC instead of making a voltage regulator circuit from
scratch. Before you start using 7809, you will need to know about the pin structure of IC 7809.
Apparently, it looks like a transistor. It has three pins. For a better understanding, I have given an image
of 7809 bellow. Please take a look.
You can easily see the V in and V out pins as well as the ground pin. It is really easy to use 7809 for
voltage regulation purposes. I have also included a circuit diagram of 7809 so that you may learn how to
use it in a circuit diagram.
It is wise to use two .1uF capacitors on both input and output sides to filter any ripple or distortion in
voltage but it is not necessary. In the image, you can see that 12V are being supplied on the input side of
7809 but the out put side of 7809 is outputting Regulated 9V. As long as the input voltage remains
above 9V, output voltage of 7809 will remain smooth and regulated.
Please note that input voltage of 7809 can be up to 23V but under my experience, it is wise to avoid
input over 15V. 7809 is claimed to output 9V and almost 1.5A Current but again, I have experienced

44. 44
that we should not put a load over 9V and 1A on it. Since we are using it in power supply, the transfer of
power will result in heat output. We will need to use a heat sink with 7809 otherwise this heat can
damage it. It is advised to use a 1A fuse on the output side of 7809 and a 1.5A fuse on the input side of
7809 to avoid damage in case of short circuit.
4.13 DARKNESS DETECTOR
Summary
This circuit based project demonstrates the principle and operation behind the darkness detector. For
example lamps which switch on automatically in the night. Various decoration lights are needed to be
switched on automatically in dark.
The circuit described here is more of a sensor application with a speaker attached to it as output.
However, depending upon the application, user can attach a night lamp or series of small LEDs to the
circuit too.
Constructed around a 555 timer IC and LDR, this darkness detector circuit uses a 9V battery as a power
source along with a couple of passive circuit components: resistance and capacitance.
Description
In this circuit 555 works in astable mode producing a frequency of about 56 hertz. Pin 4 which is reset
pin is connected to ground through a LDR. Reset pin which is active high if gets directly connected to
ground and circuit does not functions, but in this circuit when there is dark, the resistance of LDR
becomes very high and conduction does not takes place so high voltage is retained at pin4 and circuit
functions; there by making it a dark activate circuit. In presence of light the resistance of LDR
becomes low and reset pin takes ground and LED does not operate while circuit works in dark and LED
operate. This project can have varied applications like by using this circuit for high frequency we can
make dark activated decoration lamps or night lamps (they could be closed by switch too).

45. 45
Circuit Diagram
Fig- 4.17 circuit diagram of darkness detector
4.14 Component
4.14.1 Resistor
Resistor is a passive component used to control current in a circuit. Its
resistance is given by the ratio of voltage applied across its terminals to the
current passing through it. Thus a particular value of resistor, for fixed
voltage, limits the current through it. They are omnipresent in electronic
circuits.

46. 46
4.14.2 Capacitor
Capacitor is a passive component used to store charge. The charge (q) stored
in a capacitor is the product of its capacitance (C) value and the voltage (V)
applied to it. Capacitors offer infinite reactance to zero frequency so they are
used for blocking DC components or bypassing the AC signals. The
capacitor undergoes through a recursive cycl...
4.14.3 LDR
An LDR (Light dependent resistor), as its name suggests, offers resistance in
response to the ambient light. The resistance decreases as the intensity of
incident light increases, and vice versa. In the absence of light, LDR exhibits
a resistance of the order of mega-ohms which decreases too few hundred
ohms in the presence of light. It can act as a sensor, since a varying voltage
drop can be obtained...
4.14.4 555 Timer IC
555 is a very commonly used IC for generating accurate timing pulses. It is
an 8pin timer IC and has mainly two modes of operation: monostable and
astable. In monostable mode time delay of the pulses can be precisely
controlled by an external resistor and a capacitor whereas in astable mode the
frequency & duty cycle are controlled by two external resistors and a...
Explanation:
 In the circuit diagram we can observe that 12V battery is connecter to the diode LED and also
connected to the pin8 of the IC 4047 which is VCC or power supply pin and also to pin 4 and 5

47. 47
which are astable and complement astable of the IC. Diode in the circuit will help not give any
reverse current, LED will work as a indicator to the battery is working or not.
 IC CD4047 will work in the astable multivibrator mode. To work it in astable multivibrator
mode we need an external capacitor which should be connected between the pin1 and pin3. Pin2
is connected by the resistor and a variable resistor to change the change the output frequency of
the IC. Remaining pins are grounded .The pins 10 and 11 are connected to the gate of the
mosfets IRF540. The pin 10 and 11 are Q and ~Q from these pins the output frequencies is
generated with 50% duty cycle.
 The output frequency is connected to the mosfets through resistor which will help to prevent to
the loading of the mosfets. The main AC current is generated by the two mosfets which will act
as a two electronic switches. The battery current is made to flow upper half or positive half of the
primary coil of transformer through Q1 this is done when the pin 10 becomes high and lower
half or negative half is done by opposite current flow through the primary coil of transformer,
this is done when pin 11 is high. By switching the two mosfets current is generated.
 This AC is given to the step up transformer of the secondary coil from this coil only we will get
the increased AC voltage , this AC voltage is so high; from step up transformer we will get the
max voltage. Zenor diode will help avoid the reverse current.
NOTE: The generated AC is not equal to the normal AC mains or house hold current. You cannot use
this voltage for pure electric appliances like heater, electric cooker etc. Because of the fast switching of
mosfets heat is dissipated which will effect the efficiency, use heat sink to remove this problem.

48. 48
CHAPTER-5
APLLICATION:
 High efficiency electronic circuitry
 Very low self-consumption
 100% short circuit protection
 Surge/lighting protectedPerfect design, Easy Installation
 MOSFET based solar charge controller for efficient battery charging
 Automatic dawn dusk operation (with timer-optional)
 Highly Economic and reliable
 Single Battery Type
 Temperature Compensated Battery charging
 Approved by Ministry of Non Conventional Energy Sources, Govt. of India
 Excellent for remote villages

49. 49
CONCLUSION
Sun is the biggest source of energy in the universe. The utilization of other energy sources like coal
energy, wood energy, oil and gas energy, electrical energy etc are increasing day by day as increasing
demands of population. So, in a very near future or even today we are hardly meeting our demands of
energy from the sources other than “Solar Energy”. Advanced countries are already utilizing solar
energy. If we want to overcome our future requirements of Pakistan successfully, we shall definitely
have to plan and execute in the direction of achieving max use of solar energy.

50. 50
FUTURE OF THIS PROJECT:
As whole world is facing a problem of global warming and energy crisis, our project will help to reduce
these problems by using solar energy to generate electricity. Solar energy is a infinite source of
energy.Main motto of our project is to promote use of renewable energy sources. This project is most
useful in our life becouse in this project one time investment fixed on life time.In future one day non
renewable energy will end then we will use to the renewable energy. Our aim is to design and
implement Solar Street Light system to drive a load using solar energy.

51. 51
REFERENCE;
1. Some Websites :
 www.alldatasheets.com
 www.technowave.co.in
 www.datasheetcatalog.com
 www.electronicscircuits.com