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CHAPTER 1

INTRODUCTION

Solar energy systems have emerged as a viable source of renewable energy over the

past two or three decades, and are now widely used for a variety of industrial and domestic

applications. Suchsystems are based on a solar collector, designed to collect the suns energy

and to convert it into either electrical power or thermal energy. The literature contains many

studies regarding the use of solar collectors to implement such applications as light fixtures,

window covering systems, cookers, and so forth . In general, the power developed in such

applications depends fundamentally upon the amount of solar energy captured by the

collector, for optimal efficiency, solar panels should be perpendicular to sunlight, when the

illumination is strongest and thus the problem of developing tracking schemes capable of

following the trajectory of the sun throughout the course of the day on a year-round basis has

received significant coverage in the literature. For example, various schemes have been

proposed for optimizing the tilt angle and orientation of solar collectors designed for different

geographical latitudes or possible utilization periods. In general, the results showed that by

using mathematical models to optimize the tilt angle and orientation of the solar collector, a

yearly gain of more than 5% could be obtained in the captured solar radiation compared tothe case in which the collector was fixed on a horizontal surface. Moreover, it has been found

that the amount of solar energy captured by a tilted collector could be increased by more than

40% by adjusting the tilt angle on a seasonal basis.

The position of the sun with respect to that of the earth changes in a cyclic manner

during the course of a calendar year. Tracking the position of the sun in order to expose a

solar panel to maximum radiation at any given time is the main purpose of a solar tracking

PV system. A diagram1.1 depicting the variation of the movement of the sun on annual basis

is shown below. From the diagram depicting the movement of the sun we observe that a

single axis of rotation is does not provide good efficiency , since panel needs tilting on both

side also a double axis tracking system is much superior and more feasible and adaptive than

a single axis tracking system.

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Fig1. 1 Variation of the movement of the sun on annual

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Fig1. 2 General block diagram of the project.

The Solar radiation mechanism represents the panel and the gear mechanism. The

panel collects the incident radiation ,the gear mechanism gives the movement and

mechanical support to the panel and the whole assembly . Sensors are used to sense the

intensity of light. Here two sensor assembly is used .The difference in the intensity sense bythe two sensor is used to track the optimum position of the panel. The sensor feed the inputs

to microcontroller. The microcontroller Section consists of the control circuit which analyses

the inputs form the sensors and then the required signals to the driving circuits.

Driving circuits provides the power required by the two stepper motors to run. The driving

circuits vary the current to the motors to get the panel in the required position which depends

upon the inputs from the microcontroller.

The two stepper motors provide the double axis tracking. The two motors make it

possible for the panel to track the sun for almost any position in the sky.

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CHAPTER 2

SOLAR PANEL

Solar panel converts sunlight directly into electricity by using a semiconductor,usually made of silicon. When the sunlight hits the photovoltaic cells, part of the energy is

absorbed into the semiconductor. When that happens the energy loosens the electrons which

allow them to flow freely. The flows of these electrons are current and when we put metal on

the top and bottom of the photovoltaic cells, we can draw that current to use it externally. All

solar cells require a light absorbing material contained within the cell structure to absorb

photons and generate electrons via the photovoltaic effect. The materials used in solar cells

tend to have the property of preferentially absorbing the wavelengths of solar light that reach

the earth surface. Photovoltaic panels are normally made of either silicon or thin-film cells:

2.1 Types of Solar Panels

2.1.1 Monocrystalline Solar Panels

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http://en.wikipedia.org/wiki/Absorption_(electromagnetic_radiation)http://en.wikipedia.org/wiki/Photovoltaic_effecthttp://en.wikipedia.org/wiki/Photovoltaic_effecthttp://en.wikipedia.org/wiki/Absorption_(electromagnetic_radiation)

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Fig 2. 1Monocrystalline solar panel

Monocrystalline solar panels are made from a large crystal of silicon. These type of solar

panels are the most efficient as in absorbing sunlight and converting it into electricity,

however they are the most expensive. Instead of one large crystal, this type of solar panel

consists of multiple amounts of smaller silicon crystals.

2.1.2 Polycrystalline Solar Panels

Fig 2. 2 Polycrystalline solar panel

Polycrystalline solar panels are the most common type of solar panels on the market today.

They look a lot like shattered glass. They are slightly less efficient then the monocrystalline

solar panels and less expensive to produce. Instead of one large crystal, this type of solarpanel consists of multiple amounts of smaller silicon crystals.

2.1.3 Amorphous Solar Panels

Fig 2. 3 Amorphous solar panel

Amorphous solar panels consist of a thin-like film made from molten silicon that is spread

directly across large plates of stainless steel or similar material. These types of solar panels

have lower efficiency then the other two types of solar panels, and the cheapest to produce.

That means that the solar panel continues to charge while parts of the solar panel cells are in a

shadow. These work great on boats and other types of transportation.

2.2 Solar Panel Specification Table

Part No Description Size Weight Amps/Hr Amps/Day

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STP005 5 w Solar Panel 315x215x25mm 1.0kg 0.33 Up to 2.31

STP010 10 w Solar Panel 397x278x25mm 1.6kgs 0.66 Up to 4.62







Table 2.2 Specification of solar panel

CHAPTER 3

GEAR SYSTEM

When an application calls for the transmission of motion and/or power between shafts that

intersect at right angles (90-degrees), bevel gears are best suited.

A bevel gear is shaped like a section of a cone. Its teeth may be straight or spiral. (If they are

spiral, the pinion and gear must be of opposite hand to run together.) Because bevel gears are

used to reduce speed, the pinion always has fewer teeth.

Bevel gears are useful when the direction of a shaft's rotation needs to be changed. They are

usually mounted on shafts that are 90 degrees apart, but can be designed to work at other

angles as well.

The teeth on bevel gears can be straight or spiral. Straight bevel gear teeth actually have the

same problem as straight spur gear teeth -- as each tooth engages; it impacts the

corresponding tooth all at once.

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Fig 3. 1 Bevel gear Fig 3. 2 spiral bevel gear

Just like with spur gears, the solution to this problem is to curve the gear teeth. These

spiral teeth engage just like helical teeth: the contact starts at one end of the gear and

progressively spreads across the whole tooth

Fig 3. 3 Gear system

The above figure shows the various parameters that are required to be considered in the

selection of the bevel gear. A table depicting the formulas to calculate dimensions of various

parts of bevel gears is given below.

3.1 FORMULAS FOR DETERMINING GEAR DIMENSIONS

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The following formula on Chart gives the dimensions of various parts of bevel gears

Table 3. 1 Gear parameter calculation

CHAPTER 4

STEPPRR MOTOR SELECTION AND TORQUE

CALCULATION

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When a stepper motor is selected, eight different things must be considered:

1. Operating speed in steps/second

2. Torque in oz-in.

3. Load inertia in Ib-in.2

4. Required step angle

5. Time to accelerate in ms

6. Time to decelerate in ms

7. Type of drive to be used

8. Size and weight considerations

9. The torque/speed characteristic

Some of this information will be provided from application specifications, such as the

size and weight considerations, step angle, and the operating speed. Other information must

be calculated. A selected stepper motor should provide an output torque larger than load

torque and be required to start and stop at a proper step rate against load inertia. Also, when

operating the motor at a rate higher than the starting pulse rate, the rate needs to be varied

within a proper acceleration time.

4.1 Torque calculation

4.1.1 Obtaining the load torque

Fig 4. 1 Action of torque

Where,

T: Load torque (kg cm) r: Radius to apply the force F(cm)

F: Force to rotate the coupling shaft of a stepper motor (cm)

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Fig 4. 2 System torque

Where,

T: Load torque (kg cm) N1: Number of pinion teeth

N2: Number of gear teeth W: Weight of table and work (kg)

u: Frictional resistance of rubbing surface P: Pitch of feed screw (cm)h: Transfer efficiency of the system including feed screw and gear

4.1.2 Obtain load inertia

Fig 4. 3 System inertia

where,

J0: Load inertia (kgcms2) J1: Inertia of pinion (kgcms2)

J2: Inertia of gear (kgcms2) J3: Inertia of feed screw (kgcms2)

J4: Inertia of work and table (kgcms2) N1: Number of pinion teeth

N2: Number of gear teeth W: Weight of work and table (kg)

d: Table movement per pulse (cm) P: Pitch of feed screw (cm)

p: Ratio of the circumference of a circle to its diameter (3.14)

a: Step angle per pulse ()

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4.4 Torque v/s Speed Characteristics

Characteristics are dependent upon (change with) the motor, excitation mode and type of

driver or drive method. A typical speed torque curve is shown infig.

Fig 4. 4 Torque v/s Speed characteristic

4.4.1 Holding torque

The maximum torque produced by the motor at standstill.

4.4.2 Pull-In Curve

The pull-in curve defines a area refered to as the start stop region. This is the maximum

frequency at which the motor can start/stop instantaneously, with a load applied, without loss

of synchronism.

4.4.3 Maximum Start Rate

The maximum starting step frequency with no load applied.

4.4.4 Pull-Out Curve

The pull-out curve defines an area refered to as the slew region. It defines the maximum

frequency at which the motor can operate without losing synchronism. Since this region is

outside the pull-in area the motor must ramped (accelerated or decelerated) into this region.

4.4.5 Maximum Slew Rate

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The maximum operating frequency of the motor with no load applied.

CHAPTER 5

STEPPER MOTOR

The Stepper Motor is an electromagnetic device that converts digital pulses into mechanical

shaft rotation. This motor controlled by a series of electromagnetic coils. The center shaft has a

series of magnets mounted on it, and the coils surrounding the shaft are alternately given current or

not, creating magnetic fields which repulse or attract the magnets on the shaft, causing the motor to

rotate.

Advantages

1. The rotation angle of the motor is proportional to the input pulse.

2. The motor has full torque at standstill (if the windings are energized)

3. Precise positioning and repeatability of movement since good stepper motors have an

accuracy of 3 5% of a step and this error is non cumulative from one step to the next.

4. Excellent response to starting/ stopping/reversing.

5. Very reliable since there are no contact brushes in the motor. Therefore the life of the

motor is simply dependant on the life of the bearing.

6. The motors response to digital input pulses provides open-loop control, making the motor

simpler and less costly to control.

7. It is possible to achieve very low speed synchronous rotation with a load that is directly

coupled to the shaft.

8. A wide range of rotational speeds can be realized as the speed is proportional to the

frequency of the input pulses.

Disadvantages1. Resonances can occur if not properly controlled.

2. Not easy to operate at extremely high speeds.

5.1 Type of stepper motor

There are three basic stepper motor

Variable-reluctance

Permanent-magnet

Hybrid

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From the above motor permanent magnet stepper motor used because variable reluctance

motors are generally noisy, no matter what drive waveform is used. As compared permanent

magnet is generally preferred where noise or vibration is issues. Permanent magnet motors

can be micro stepped, allowing positioning to a fraction of a step, and allowing Smooth, jerk-

free moves from one step to the next. Micro stepping is not generally applicable to variable

reluctance motors. These motors are typically run in full-step increments. Complex current

limiting control is required to achieve high speeds with variable reluctance motors. Stator of

permanent magnet stepper motor is constructed as a stack of two windings enclosed in metal

stampings that resemble tin cans and are almost as inexpensive to manufacture. In

comparison, hybrid and variable reluctance motors are made using stacked laminations with

motor windings that are significantly more difficult to wind. Hybrid motors suffer some of

the vibration problems of variable reluctance motors

Permanent magnet motor is available with either unipolar, bipolar or bifilar winding;

the latter can be used in either unipolar or bipolar configurations. The choice between using a

unipolar or bipolar drive system rests on issues of drive simplicity and power to weight ratio.

Bipolar motors have approximately 30% more torque than an equivalent unipolar motor of

the same volume. The reason for this is that only one half of a winding is energized at any

given time in a unipolar motor. A bipolar motor utilizes the whole of a winding when

energized. The higher torque generated by a bipolar motor does not come without a price.

Bipolar motors require more complex control circuitry than unipolar motors. This will have

an impact on the cost of an application.

5.2 Permanent-magnet (PM) Stepper Motors

Thepermanent-magnet stepper motor operates on the reaction between a permanent-magnet

rotor and an electromagnetic field. Figure shows a basic two-pole PM stepper motor. The

rotor shown in Figure5.1 (a) has a permanent magnet mounted at each end. The stator is

illustrated in Figure5.1 (b). Both the stator and rotor are shown as having teeth. The teeth on

the rotor surface and the stator pole faces are offset so that there will be only a limited

number of rotor teeth aligning themselves with an energized stator pole. The number of teeth

on the rotor and stator determine the step angle that will occur each time the polarity of the

winding is reversed. The greater the number of teeth, the smaller the step angle.

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Fig 5. 1 Components of stepper motor (a) rotor, (b) stator

When a PM stepper motor has a steady DC signal applied to one stator winding, the rotor will

overcome the residual torque and line up with that stator field. The holding torque is defined

as the amount of torque required to move the rotor one full step with the stator energized. An

important characteristic of the PM stepper motor is that it can maintain the holding torque

indefinitely when the rotor is stopped. When no power is applied to the windings, a small

magnetic force is developed between the permanent magnet and the stator. This magnetic

force is called a residual, or detent torque. The detent torque can be noticed by turning a

stepper motor by hand and is generally about one-tenth of the holding torque.

Figure5.2 (a) shows a permanent magnet stepper motor with four stator windings. By pulsing

the stator coils in a desired sequence, it is possible to control the speed and direction of the

motor. Figure 5.2(b) shows the timing diagram for the pulses required to rotate the PM

stepper motor illustrated in Figure5.2(a). This sequence of positive and negative pulses

causes the motor shaft to rotate counterclockwise in 90 steps. The waveforms of Figure

5.2(c) illustrate how the pulses can be overlapped and the motor made to rotate

counterclockwise at 45 intervals.

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Fig 5. 2 PM stepper motor (a) 90 step (b) 45 step

A more recent development in PM stepper motor technology is thethin-disk rotor.

This type of stepper motor dissipates much less power in losses such as heat than the

cylindrical rotor and as a result, it is considerably more efficient. Efficiency is a primary

concern in industrial circuits such as robotics, because a highly efficient motor will run cooler

and produce more torque or speed for its size. Thin-disk rotor PM stepper motors are alsocapable of producing almost double the steps per second of a conventional PM stepper motor.

Figure3 shows the basic construction of a thin-disk rotor PM motor. The rotor is constructed

of a special type of cobalt-steel, and the stator poles are offset by one-half a rotor segment.

Fig 5. 3 Thin-disk rotor PM motor

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CHAPTER 6

POWER SUPPY

The power supply circuit is used to energize the control circuit system consisting of the

controlling and the driving circuit. The control and driving circuit being electronic in nature

need DC supply. Following circuit provides the required DC supply.

Circuit for 5v & 12v D.C.Power supply

6.1 Circuit diagram-:

Fig 6. 1 Circuit dig.

Components-:

1.Transformer -1 ph AC to AC,230V/12V,1.5 A. 2.Diode (IN4007)-4 Nos.

3.Capacitor-470 uf : 1No. 4.Resistor - 2.2 kohm:1No.

-0.01uf: 1No -270ohm:1No.

5.IC 7805

6.2 Circuit Description-:

1 phase 230v AC supply converted into 12V a AC by using a single phase transformer .A

bridge rectifier consisting of 4 diodes converts this AC to pulsating DC.The capacitors are

used to remove the ripples contained in output of bridge rectifier. IC 7805 (fixed voltage

regulator IC) with the configuration as shown in above circuit, is used to get +5v & +12v

supply.

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REFERANCES

Solar Panel

Maximum Power line (April,may,june 2009) magazine

www.solarshop.co.in

www.abetterfocus.com

Stepper motor

Stepper motor by v.v Athani

Electrical Technology vol II by B.L.Theraja

www.premotec.com

Gear system

Design data book PSG College of Technology

www.boostgear.com

Power Circuit

Power Electronics by Rashid

Modern Power Electronics by B.K.Bose

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http://www.solarshop.co.in/http://www.premotec.com/http://www.boostgear.com/http://www.solarshop.co.in/http://www.premotec.com/http://www.boostgear.com/

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