SARMA Main Document
Transcript of SARMA Main Document
SOLAR BASED FAN WITH TAGGED SPEED SELECTION FOR RURAL PEOPLE
CHAPTER 1INTRODUCTION
Fig 1: Solar Fan
This project is designed keeping the problem of rural area people in mind. Basically the power shortage is frequent in rural areas, especially in summer, also, now a days the current charges are getting increased. To avoid all these problems we implemented this project with the help of renewable energy resources i.e. the sunlight
In this project the solar panel is used to charge the re-chargeable battery which is the heart of the project. The regulator followed by the battery sets the voltage level constantly i.e.12V. The fan is working with the voltage of 12V.
This project is easy to implement and less cost. It is durable and reliable. With the help of this project we can over-come the problem faced by the rural people because of the power shortage.
In this project battery is recharged from two supply voltages. One from house hold supply and another from solar panels. So in this way we have two phases of supplies are available for charging the battery.
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CHAPTER 2BLOCK DIAGRAM
all
To all sections
Fig 2: Block diagram
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Control Switch Array
DC Motor(Fan)
Solar Panel Unidirectional flow circuit
Rechargeable Battery
Step down T/F
Bridge Rectifier
Filter Circuit
Regulator
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2.1 EXPLANATION OF BLOCK DIAGRAM:
Solar rechargeable fans become necessary for a common man. Especially, in summer,
the power shortage is more. To overcome from the difficulties caused by power shortage this
innovative project is designed. This project is designed for 12V motor.
The battery also can be charged through 230V house hold supply. This charge circuit
uses regulated 12V, 750mA power supply. 7812 three terminal voltage regulator is used for
voltage regulation. Bridge type full wave rectifier is used to rectify the ac out put of
secondary of 230/18V step down transformer.
A rechargeable lead acid battery of 12V is used to power the circuit. A solar panel is
connected to the battery for charging the battery by means of solar energy. A PN junction
diode is used to control the charge current for unidirectional flow.
In this project Control switch array is used in between rechargeable battery and DC
fan. It controls the speed operation of a fan. By using this control switch array.
To run a fan we are using the DC motor. This motor can run with rechargeable
battery. It can be controlled by control switch array.
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CHAPTER 3
SCHEMATIC DIAGRAM
Fig 3: Schematic Diagram
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3.1 WORKING PROCEDURE
A rechargeable lead acid battery of 12V is used to power the circuit.
A solar panel is connected to the battery for charging the battery by means of solar
energy.
A PN junction diode is used to control the charge current for unidirectional flow.
The battery also can be charged through 230V house hold supply.
This charge circuit uses regulated 12V, 750mA power supply.
7812 three terminal voltage regulator is used for voltage regulation.
Bridge type full wave rectifier is used to rectify the ac output of secondary of
230/18V step down transformer.
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EXPLANATION OF EACH BLOCK
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CHAPTER 4
POWER SUPPLY DESIGN
Fig 4.1: Power supply design
Input ac supply gives the voltage of 230 volts to the transformer.
Transformer converts the voltage 230V to 12V.
The AC voltage is converted into DC voltage by the full wave bridge type rectifier.
The AC ripples presented in the output of full wave rectifier are eliminated by the
filter circuit.
For producing the constant output voltage of 12V, regulator is used.
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INPUT AC SUPPLY
TRANSFORMER
FULL WAVE
BRIDGE TYPE
RECTIFIER
FILTER CIRCUIT
VOLTAGE REGULATO
R
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4.1 POWER SUPPLY
The input to the circuit is applied from the regulated power supply. The a.c. input i.e.,
230V from the mains supply is step down by the transformer to 12V and is fed to a rectifier.
The output obtained from the rectifier is a pulsating d.c voltage. So in order to get a pure d.c
voltage, the output voltage from the rectifier is fed to a filter to remove any a.c components
present even after rectification. Now, this voltage is given to a voltage regulator to obtain a
pure constant dc voltage.
4.2 TRANSFORMER:
Usually, DC voltages are required to operate various electronic equipment and these
voltages are 5V, 9V or 12V. But these voltages cannot be obtained directly. Thus the a.c
input available at the mains supply i.e., 230V is to be brought down to the required voltage
level. This is done by a transformer. Thus, a step down transformer is employed to decrease
the voltage to a required level.
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Fig 4.2: Transformer
4.3 RECTIFIER:
The output from the transformer is fed to the rectifier. It converts A.C. into
pulsating D.C. The rectifier may be a half wave or a full wave rectifier. In this project, a
bridge rectifier is used because of its merits like good stability and full wave rectification.
Fig 4.3: Rectifier
The Bridge rectifier is a circuit, which converts an ac voltage to dc voltage using both
half cycles of the input ac voltage. The Bridge rectifier circuit is shown in the figure. The
circuit has four diodes connected to form a bridge. The ac input voltage is applied to the
diagonally opposite ends of the bridge. The load resistance is connected between the other
two ends of the bridge.
For the positive half cycle of the input ac voltage, diodes D1 and D3 conduct, whereas
diodes D2 and D4 remain in the OFF state. The conducting diodes will be in series with the
load resistance RL and hence the load current flows through RL.
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For the negative half cycle of the input ac voltage, diodes D2 and D4 conduct
whereas, D1 and D3 remain OFF. The conducting diodes D2 and D4 will be in series with the
load resistance RL and hence the current flows through RL in the same direction as in the
previous half cycle. Thus a bi-directional wave is converted into a unidirectional wave
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Fig 4.3.1: Bridge rectifier output
4.4 FILTER
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Capacitive filter is used in this project. It removes the ripples from the output of
rectifier and smoothens the D.C. Output received from this filter is constant until the mains
voltage and load is maintained constant. However, if either of the two is varied, D.C. voltage
received at this point changes. Therefore a regulator is applied at the output stage.
Fig 4.4: Capacitor Filter.
Capacitor is a electronic component which stores the energy in the form of electric
field. The capacitor is allows the only ac components and rejects the dc components so from
the properties of the capacitor, here we use the capacitor filter.
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4.5 VOLTAGE REGULATOR
As the name itself implies, it regulates the input applied to it. A voltage regulator is an
electrical regulator designed to automatically maintain a constant voltage level. In this
project, power supply of 5V and 12V are required. In order to obtain these voltage levels,
7805 and 7812 voltage regulators are to be used. The first number 78 represents positive
supply and the numbers 05, 12 represent the required output voltage levels. The L78xx series
of three-terminal positive regulators is available in TO-220, TO-220FP, TO-3, D2PAK and
DPAK packages and several fixed output voltages, making it useful in a wide range of
applications. These regulators can provide local on-card regulation, eliminating the
distribution problems associated with single point regulation. Each type employs internal
current limiting, thermal shut-down and safe area protection, making it essentially
indestructible. If adequate heat sinking is provided, they can deliver over 1 A output current.
Although designed primarily as fixed voltage regulators, these devices can be used with
external components to obtain adjustable voltage and currents.
Fig 4.5: Voltage
Regulator PIN & INTERNAL diagrams.
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CHAPTER 5
CONTROL SWITCH ARRAY
A group of four switches are used at the transmitter end for the robot movement. To
move the robot in forward, backward, left direction we require these control switch Array.
For this operation we are using push button (4 leg push button). A pushbutton is a simple
switch mechanism which permits user generated changes in the state of a circuit. Pushbutton
usually comes with four legs. Anyway, as you can see from the picture below, legs are
always connected in groups of two. When the pushbutton is pressed all the 4 legs are
connected. This kind of 4 switches are connected on pcb .
Fig 5: Control switch array.
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CHAPTER 6
SOLAR PANEL
Fig 6: Solar Panel
6.1 SOLAR PANEL
A solar panel (photovoltaic module or photovoltaic panel) is a packaged
interconnected assembly of solar cells, also known as photovoltaic 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. Because a single solar panel can only produce a
limited amount of power, many installations contain several panels. A photovoltaic system
typically includes an array of solar panels, an inverter, may contain a battery and
interconnection wiring.
Solar panels use light energy (photons) from the sun to generate electricity through
the photovoltaic effect. The structural (load carrying) member of a module can either be the
top layer or the back layer. The majority of modules use wafer-based crystalline silicon cells
or thin-film cells based on cadmium telluride or silicon. The conducting wires that take the
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current off the panels may contain silver, copper or other conductive (but generally not
magnetic) transition metals.
The cells must be connected electrically to one another and to the rest of the system. Cells
must also be protected from mechanical damage and moisture. Most solar panels are rigid,
but semi-flexible ones are available, based on thin-film cells.
Electrical connections are made in series to achieve a desired output voltage and/or in
parallel to provide a desired current capability.
Separate diodes may be needed to avoid reverse currents, in case of partial or total
shading, and at night. The p-n junctions of mono-crystalline silicon cells may have adequate
reverse current characteristics that these are not necessary. Reverse currents waste power and
can also lead to overheating of shaded cells. Solar cells become less efficient at higher
temperatures and installers try to provide good ventilation behind solar panels.
Some recent solar panel 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.[citation needed].
Depending on construction, photovoltaic panels can produce electricity from a range
of frequencies of light, but usually cannot cover the entire solar range (specifically,
ultraviolet, infrared and low or diffused light). Hence much of the incident sunlight energy is
wasted by solar panels, and they can give far higher efficiencies if illuminated with
monochromatic light. Therefore another design concept is to split the light into different
wavelength ranges and direct the beams onto different cells tuned to those ranges. This has
been projected to be capable of raising efficiency by 50%. The use of infrared photovoltaic
cells has also been proposed to increase efficiencies, and perhaps produce power at night.
[citation needed].
Sunlight conversion rates (solar panel efficiencies) can vary from 5-18% in
commercial products, typically lower than the efficiencies of their cells in isolation. Panels
with conversion rates around 18% are in development incorporating innovations such as
power generation on the front and back sides. The Energy Density of a solar panel is the
efficiency described in terms of peak power output per unit of surface area, commonly
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expressed in units of Watts per square foot (W/ft2). The most efficient mass-produced solar
panels have energy density values of greater than 13 W/ft2.
Fig 6.1: Outer view of solar panel.
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Fig 6.1.1: Conversion of Solar Energy
The solar panel diagram above shows how solar energy is converted into electricity through
the use of a silicon cell.
In the diagram above, you can see how a solar panel converts sunlight into energy to
provide electricity for a range of appliances.
This energy can be used for heating, through the use of solar hot water panels, or
electricity through the use of regular solar cells.
6.2 THE THEORY BEHIND THE SOLAR PANEL DIAGRAM
As you can see from the above diagram of a solar panel, photons are contained within
the sun’s rays and beam down to earth.
Once these photons reach the solar panel, they are absorbed by the silicon material,
and this allows electrons to be knocked off their orbit.
As the electrons are knocked off their orbit, they become free electrons and are able to
pick up a current, resulting in the flow of electricity to external sources.
New technologies are making renewable energy devices much more efficient and a
viable contender for electricity production from fossil fuels.
6.3 THE USE OF ELECTRICITY FROM SOLAR PANELS
As the solar panel diagram shows, you can see how power is sourced out to various
locations, this depends on how you plan to use the energy harnessed by a solar cell.
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Possible uses of solar electricity could be to incorporate the current into an existing
power supply, provide a separate power supply dependent upon the solar panel, to charge
solar batteries for the storage of solar electricity, or even to sell back to the national grid.
Solar panels can even be used to heat water in different designs. Some home
swimming pools also use solar energy to heat the water, however this can usually be a very
expensive option.
Solar energy has a huge advantage for providing electricity in remote locations due to the
simple running requirements (i.e. no fossil fuels need to be transported the location).
A remote solar panel system can provide electricity for vital tasks where the laying of
electricity cable is not practical, a working example of this is on satellites
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CHAPTER 7
RECHARGEABLE BATTERY
Fig 7: Rechargeable Battery
7.1 RECHARGEABLE BATTERY
A rechargeable battery or storage battery is a group of one or more electrochemical
cells. They are known as secondary cells because their electrochemical reactions are
electrically reversible. Rechargeable batteries come in many different shapes and sizes,
ranging anything from a button cell to megawatt systems connected to stabilize an electrical
distribution network. Several different combinations of chemicals are commonly used,
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including: lead-acid, nickel cadmium (NiCd), nickel metal hydride (NiMH), lithium ion (Li-
ion), and lithium ion polymer (Li-ion polymer).
Rechargeable batteries have lower total cost of use and environmental impact than
disposable batteries. Some rechargeable battery types are available in the same sizes as
disposable types.
Rechargeable batteries are used for automobile starters, portable consumer
devices, light vehicles (such as motorized wheelchairs, golf carts, electric bicycles, and
electric forklifts), tools, and uninterruptible power supplies. Emerging applications in hybrid
electric vehicles and electric vehicles are driving the technology to reduce cost and weight
and increase lifetime.
Normally, new rechargeable batteries have to be charged before use; newer low
self-discharge batteries hold their charge for many months, and are supplied charged to about
70% of their rated capacity.
Grid energy storage applications use rechargeable batteries for load leveling,
where they store electric energy for use during peak load periods, and for renewable energy
uses, such as storing power generated from photovoltaic arrays during the day to be used at
night. By charging batteries during periods of low demand and returning energy to the grid
during periods of high electrical demand, load-leveling helps eliminate the need for
expensive peaking power plants and helps amortize the cost of generators over more hours of
operation.
The US National Electrical Manufacturers Association has estimated that U.S.
demands for rechargeable batteries is growing twice as fast as demand for non rechargeable.
7.2 CHARGING AND DISCHARGING
During charging, the positive active material is oxidized, producing electrons, and the
negative material is reduced, consuming electrons. These electrons constitute the current flow
in the external circuit. The electrolyte may serve as a simple buffer for ion flow between
the electrodes, as in lithium-ion and nickel-cadmium cells, or it may be an active participant
in the electrochemical reaction, as in lead-acid cells.
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Fig7.2: Charging Of a Secondary Cell Battery
Fig 7.2.1: Battery Charge
The energy used to charge rechargeable batteries usually comes from a battery
charger using AC mains electricity. Chargers take from a few minutes (rapid chargers) to
several hours to charge a battery. Most batteries are capable of being charged far faster than
simple battery chargers are capable of; there are chargers that can charge consumer sizes of
NiMH batteries in 15 minutes. Fast charges must have multiple ways of detecting full charge
(voltage, temperature, etc.) to stop charging before onset of harmful overcharging.
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Fig 7.2.2: A Solar-powered Charger for Rechargeable Batteries
Rechargeable multi-cell batteries are susceptible to cell damage due to reverse
charging if they are fully discharged. Fully integrated battery chargers that optimize the
charging current are available.
Attempting to recharge non-rechargeable batteries with unsuitable equipment may
cause battery explosion Flow batteries, used for specialized applications, are recharged by
replacing the electrolyte liquid.
Battery manufacturers' technical notes often refer to VPC; this is volts per cell, and
refers to the individual secondary cells that make up the battery. For example, to charge a 12
V battery (containing 6 cells of 2 V each) at 2.3 VPC requires a voltage of 13.8 V across the
battery's terminals.
Non-rechargeable alkaline and zinc-carbon cells output 1.5V when new, but this
voltage gradually drops with use. Most NiMH AA and AAA batteries rate their cells at 1.2 V,
and can usually be used in equipment designed to use alkaline batteries up to an end-point of
0.9 to 1.2V
7.3 REVERSE CHARGING
Subjecting a discharged cell to a current in the direction which tends to discharge it
further, rather than charge it, is called reverse charging; this damages cells. Reverse charging
can occur under a number of circumstances, the two most common being:
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When a battery or cell is connected to a charging circuit the wrong way round.
When a battery made of several cells connected in series is deeply discharged.
When one cell completely discharges ahead of the rest, the live cells will apply a reverse
current to the discharged cell ("cell reversal"). This can happen even to a "weak" cell that is
not fully discharged. If the battery drain current is high enough, the weak cell's internal
resistance can experience a reverse voltage that is greater than the cell's remaining internal
forward voltage. This results in the reversal of the weak cell's polarity while the current is
flowing through the cells. This can significantly shorten the life of the affected cell and
therefore of the battery. The higher the discharge rate of the battery needs to be, the better
matched the cells should be, both in kind of cell and state of charge. In some extreme cases,
the reversed cell can begin to emit smoke or catch fire.
CHAPTER 8
DC MOTOR
Fig 8: DC Motor
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8.1 DC MOTOR
A DC motor is an electric motor that runs on direct current (DC) electricity. A motor
is a electrical device which converts electrical energy into mechanical energy. A motor
working on the direct current supply is known as DC MOTOR.
8.2 DC MOTOR CONNECTIONS
Figure shows schematically the different methods of connecting the field and
armature circuits in a DC Motor. The circular symbol represents the armature circuit, and
the squares at the side of the circle represent the brush commutator system. The direction of
the arrows indicates the direction of the magnetic fields.
Fig 8.2: Motor Connections
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Externally –Excited DC-Motor:
This type of DC motor is constructed such that the field is not connected to the
armature. This type of DC motor is not normally used.
Shunt DC Motor
The motor is called “shunt” Motor because the field id parallel, or “shunts” the
armature.
Series DC Motor
The motor field windings for a series motor are in series with the armature.
Compounded DC Motor
A compounded DC motor is constructed so that it contains both a shunt and a series
field. This particular schematic shows in a above diagram fig 8.2 “cumulatively-
compounded” DC motor because the shunt and series fields are aiding one another.
Compound DC Motor
Compound DC motor is also called a “differentially – compounded” DC motor
because the shunt and series field oppose one another.
8.3 BRUSHED DC MOTOR
The brushed DC motor generates torque directly from DC power supplied to the
motor by using internal commutation, stationary permanent magnets, and rotating electrical
magnets.It works on the principle of Lorentz force , which states that any current carrying
conductor placed within an external magnetic field experiences a torque or force known as
Lorentz force. Advantages of a brushed DC motor include low initial cost, high reliability,
and simple control of motor speed. Disadvantages are high maintenance and low life-span for
high intensity uses. Maintenance involves regularly replacing the brushes and springs which
carry the electric current, as well as cleaning or replacing the commutator. These components
are necessary for transferring electrical power from outside the motor to the spinning wire
windings of the rotor inside the motor.
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Fig 8.3: Brushed DC motor
8.4 BRUSHLESS DC MOTOR
Brushless DC motors use a rotating permanent magnet in the rotor, and stationary
electrical magnets on the motor housing. A motor controller converts DC to AC. This design
is simpler than that of brushed motors because it eliminates the complication of transferring
power from outside the motor to the spinning rotor. Advantages of brushless motors include
long life span, little or no maintenance, and high efficiency. Disadvantages include high
initial cost, and more complicated motor speed controllers.
8.5 TORQUE AND SPEED OF A DC MOTOR
The torque of an electric motor is independent of speed. It is rather a function of flux and
armature current. As shown in below fig 8.5
Fig 8.5: Torque Generation
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8.6 CHARACTERISTICS OF DC MOTORS
DC motors respond to load changes in different ways, depending on the arrangement
of the windings.
Fig 8.6: Arrangement of DC Motor
8.7 SHUNT WOUND MOTOR
A shunt wound motor has a high-resistance field winding connected in parallel with
the armature. It responds to increased load by trying to maintain its speed and this leads to an
increase in armature current. This makes it unsuitable for widely-varying loads, which may
lead to overheating.
8.8 SERIES WOUND MOTOR
A series wound motor has a low-resistance field winding connected in series with the
armature. It responds to increased load by slowing down and this reduces the armature
current and minimizes the risk of overheating. Series wound motors were widely used as
traction motors in rail transport of every kind, but are being phased out in favor of AC
induction motors supplied through solid state inverters. The counter-emf aids the armature
resistance to limit the current through the armature. When power is first applied to a motor,
the armature does not rotate. At that instant the counter-emf is zero and the only factor
limiting the armature current is the armature resistance. Usually the armature resistance of a
motor is less than 1 Ω; therefore the current through the armature would be very large when
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the power is applied. Therefore the need arises for an additional resistance in series with the
armature to limit the current until the motor rotation can build up the counter-emf. As the
motor rotation builds up, the resistance is gradually cut out.
8.9 PERMANENT MAGNET MOTOR
A permanent magnet DC motor is characterized by its locked rotor (stall) torque and
its no-load angular velocity (speed)
8.10 PRINCIPLES OF OPERATION
In any electric motor, operation is based on simple electromagnetism. A current-
carrying conductor generates a magnetic field; when this is then placed in an external
magnetic field, it will experience a force proportional to the current in the conductor, and to
the strength of the external magnetic field. As you are well aware of from playing with
magnets as a kid, opposite (North and South) polarities attract, while like polarities (North
and North, South and South) repel. The internal configuration of a DC motor is designed to
harness the magnetic interaction between a current-carrying conductor and an external
magnetic field to generate rotational motion.
Let's start by looking at a simple 2-pole DC electric motor (here red represents a magnet or
winding with a "North" polarization, while green represents a magnet or winding with a
"South" polarization).
Fig 8.10: Operation of Permanent Motor
Every DC motor has six basic parts -- axle, rotor (a.k.a., armature), stator,
commutator, field magnet(s), and brushes. In most common DC motors (and all that Beamers
will see), the external magnetic field is produced by high-strength permanent magnets. The
stator is the stationary part of the motor -- this includes the motor casing, as well as two or
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more permanent magnet pole pieces. The rotor (together with the axle and attached
commutator) rotates with respect to the stator. The rotor consists of windings (generally on a
core), the windings being electrically connected to the commutator. The above diagram
shows a common motor layout -- with the rotor inside the stator (field) magnets.
The geometry of the brushes, commutator contacts, and rotor windings are such that
when power is applied, the polarities of the energized winding and the stator magnet(s) are
misaligned, and the rotor will rotate until it is almost aligned with the stator's field magnets.
As the rotor reaches alignment, the brushes move to the next commutator contacts, and
energize the next winding. Given our example two-pole motor, the rotation reverses the
direction of current through the rotor winding, leading to a "flip" of the rotor's magnetic field,
driving it to continue rotating.
In real life, though, DC motors will always have more than two poles (three is a very
common number). In particular, this avoids "dead spots" in the commutator. You can imagine
how with our example two-pole motor, if the rotor is exactly at the middle of its rotation
(perfectly aligned with the field magnets), it will get "stuck" there. Meanwhile, with a two-
pole motor, there is a moment where the commutator shorts out the power supply (i.e., both
brushes touch both commutator contacts simultaneously). This would be bad for the power
supply, waste energy, and damage motor components as well. Yet another disadvantage of
such a simple motor is that it would exhibit a high amount of torque "ripple" (the amount of
torque it could produce is cyclic with the position of the rotor).
Fig 8.10.1: Two-pole DC Motor
So since most small DC motors are of a three-pole design, let's tinker with the
workings of one via an interactive animation.
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Fig 8.10.2: Three-pole DC Motor
You'll notice a few things from this -- namely, one pole is fully energized at a time
(but two others are "partially" energized). As each brush transitions from one commutator
contact to the next, one coil's field will rapidly collapse, as the next coil's field will rapidly
charge up (this occurs within a few microsecond). We'll see more about the effects of this
later, but in the meantime you can see that this is a direct result of the coil windings' series
wiring:
Fig 8.10.3: Three-pole DC Motor
The use of an iron core armature (as in the Mabuchi, above) is quite common, and has
a number of advantages. First off, the iron core provides a strong, rigid support for the
windings -- a particularly important consideration for high-torque motors. The core also
conducts heat away from the rotor windings, allowing the motor to be driven harder than
might otherwise be the case. Iron core construction is also relatively inexpensive compared
with other construction types.
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But iron core construction also has several disadvantages. The iron armature has a
relatively high inertia which limits motor acceleration. This construction also results in high
winding inductances which limit brush and commutator life.
In small motors, an alternative design is often used which features a 'coreless'
armature winding. This design depends upon the coil wire itself for structural integrity. As a
result, the armature is hollow, and the permanent magnet can be mounted inside the rotor
coil. Coreless DC motors have much lower armature inductance than iron-core motors of
comparable size, extending brush and commutator life.
Fig 8.10.4: Internal Diagram of DC motor
8.11 DC MOTOR BEHAVIOR
8.11.1 HIGH-SPEED OUTPUT
This is the simplest trait to understand and treat -- most DC motors run at very high
output speeds (generally thousands or tens of thousands of RPM). While this is fine for some
BEAM bots (say, photo poppers or solar rollers), many BEAM bots (walkers, heads) require
lower speeds -- you must put gears on your DC motor's output for these applications.
8.12 BACK EMF
Just as putting voltage across a wire in a magnetic field can generate motion, moving
a wire through a magnetic field can generate voltage. This means that as a DC motor's rotor
spins, it generates voltage -- the output voltage is known as back EMF. Because of back
EMF, a spark is created at the commutator as a motor's brushes switch from contact to
contact. Meanwhile, back EMF can damage sensitive circuits when a motor is stopped
suddenly.
8.13 NOISE (RIPPLE) ON POWER LINES
A number of things will cause a DC motor to put noise on its power lines:
commutation noise (a function of brush / commutator design & construction), roughness in
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bearings (via back EMF), and gearing roughness (via back EMF, if the motor is part of a
gearmotor) are three big contributors.
Even without these avoidable factors, any electric motor will put noise on its power
lines by virtue of the fact that its current draw is not constant throughout its motion. Going
back to our example two-pole motor, its current draw will be a function of the angle between
its rotor coil and field magnets:
Fig 8.13: Rippler Waveforms
Since most small DC motors have 3 coils, the coils' current curves will overlay each other:
Fig 8.13.1: Rippler Waveforms for 3 Coils
Added together, this ideal motor's current will then look something like this:
Reality is a bit more complex than this, as even a high-quality motor will display a current
transient at each commutation transition. Since each coil has inductance (by definition) and
some capacitance, there will be a surge of current as the commutator's brushes first touch a
coil's contact, and another as the brushes leave the contact (here, there's a slight spark as the
coil's magnetic field collapses).
As a good example, consider an oscilloscope trace of the current through a Mabuchi
FF-030PN motor supplied with 2 V (1ms per horizontal division, 0.05 mA per vertical
division):
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Fig 8.13.2: Oscilloscope Output Waveform
In this case, the peak-to-peak current ripple is approximately 0.29 mA, while the
average motor current is just under 31 mA. So under these conditions, the motor puts about
less than 1% of current ripple onto its power lines (and as you can see from the "clean" traces,
it outputs essentially no high-frequency current noise). Note that since this is a 3-pole motor,
and each coil is energized in both directions over the course of a rotor rotation, one revolution
of the rotor will correspond to six of the above curves (here, 6 x 2.4 ms = 0.0144 sec,
corresponding to a motor rotation rate of just fewer than 4200 RPM).
Motor power ripple can wreak havoc in Nv nets by destabilizing them inadvertently.
Fortunately, this can be mitigated by putting a small capacitor across the motor's power lines
On the flip side of this coin, motor power ripple can be put to good use -- as was shown
above, ripple frequency can be used to measure motor speed, and its destabilizing tendencies
can be used to reverse a motor without the need for discrete "back-up" sensors.
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CHAPTER 9
ADVANTAGES
To Save Power
When the power is turned off then we get the power from the sun light so in
this way we can able to save the power.
Renewable Energy
Renewable energy means the energy which is again producing. In our project
sunlight is used for charging of the battery, so it is a renewable energy resource.
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Less Cost Effective
All the components used for the solar fan design are less cost, only the solar
panels are expensive so by overall designation it is less cost effective.
Two way Power Supply
In this project tow way power supply is the main advantage .one is from by
using house hold voltage source and another is from solar panels which converts solar
energy into electrical energy .
CHAPTER 10
APPLICATIONS
In air transport :
It is mainly used in the air craft’s to run the fans fast in the plane. Such type of planes
is called “Electric air craft”.
In Home Applications
In home appliances like refrigerators, fan etc..,
In Field of Agriculture
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SOLAR BASED FAN WITH TAGGED SPEED SELECTION FOR RURAL PEOPLE
In the field of agriculture to run a wind mills also we are using this type of solar cells.
Industrial applications
In industrial appliance we can use this solar fan for to run a generator in machines.
Air conditioning systems
In air conditioners the fan is used in inside the conditioner to get an cool air.
In land transport
In land transport also we can use this project to run a vehicle in side motor is used fro
this we can this project is very help full to that.
CHAPTER 11
CONCLUSION & FUTURE SCOPE
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SOLAR BASED FAN WITH TAGGED SPEED SELECTION FOR RURAL PEOPLE
This project presents the “SOLAR BASED FAN WITH TAGGED SPEED SELECTION FOR
RURAL PEOPLE” is been designed and implemented with Driver Circuit in order to drive the
DC Fan with the reference of Solar Panels . Experimental work has been carried out
carefully. The result shows higher efficiency.
To provide more power to drive the motors we have to enhance with more number of
Solar panels.
CHAPTER 12
REFERENCES
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1."Solar Thermal Panel Kozi". solarpanelsonline.org.
2.”Solar Fan Man Looks To Sun For Solutions”. abcnews.go.com
3.”Solar powered fans-get cool breeze for free from these solar fans”.solarpoweredfans.org.
4.”Benfits of using solar powered fans”. irevew.com
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