CHAPTER-1

OVERVIEW

1.1 Introduction

A Solar tracker is a device for orienting a solar photovoltaic panel towards the sun. In

solar tracking systems the surface of the module tracks the sun automatically throughout the

day. Tracking system increases the efficiency of the system considerably there by reducing

the cost per unit of output energy.

1.2 Why To Use Solar Tracking System

From many centuries, sun has been the primary source of energy for the

globe.Technically,solar energy can be defined as Electromagnetic energy transmitted from

the sun ( solar radiation).The amount of energy that reaches the earth is equal to one billionth

of total solar energy generated. But is that small? No. The amount of energy which strikes

the surface of the earth in one day exceeds daily consumption by 10,000 to 15,000 times. In

other words, the amount of solar energy intercepted by the earth every minute is greater than

the amount of energy the world uses in fossil fuels each year.

Moreover, of all the renewable energy sources available, solar energy has the smallest

environmental impacts. Electricity produced from photovoltaic cells does not result in air or

water pollution, deplete natural resources, or endanger animal or human health.

In spite of these benefits, man is not able to use this energy completely and

economically. Two billion people in the world still have no access to electricity. For most of

them, solar energy would be their cheapest electricity source, but they cannot afford it. This

is because the price of electricity produced from solar cells is still significantly more

expensive than it is from fossil fuels like coal and oil. This is because of cost involved in

1

converting the solar energy into required form of electrical energy and low efficiency of

solar system i.e., the output from the solar system is not completely sufficient for our needs.

The problem here is that the sun’s position is not constant throughout the day. The

output from the solar system depends on the intensity of sunlight and the angle at which

radiation is being incident. Hence there is a need to track the sun inorder to produce

maximum output throughout the day. The solution to the problem is our project “SOLAR

TRACKING SYSTEM”.

1.3 Analization of Solar Tracking System

A Solar tracker is a device for orienting a solar photovoltaic panel towards the sun. In

solar tracking systems the surface of the module tracks the sun automatically throughout the

day. Tracking system increases the efficiency of the system considerably there by reducing

the cost per unit of output energy.

Concentrators, especially in solar cell applications require a high degree of accuracy

to ensure that the concentrated sunlight is directed precisely to the powered device, which is

at the focal point of the reflector or lens. The output greatly depends on the angle of

incidence, Zenith angle and azimuth angle. Some solar trackers may operate most effectively

with seasonal position adjustment and most will need inspection and lubrication on an

annual basis.

FIG 1.1 Solar Panels

2

1.3.1 Types of tracking systems

Solar trackers may be active or passive and may be single axis or dual axis. Single

axis trackers usually use a polar mount for maximum solar efficiency. Single axis trackers

will usually have a manual elevation (axis tilt) adjustment on a second axis which is adjusted

on regular intervals throughout the year. Compared to a fixed mount, a single axis tracker

increases annual output by approximately 30%, and a dual axis tracker an additional 6%.

There are two types of dual axis trackers, polar and altitude-azimuth.

Polar Trackers

Polar trackers have one axis aligned to be quasi-parallel to the axis of rotation of the

earth. , polar trackers are used on high accuracy astronomical telescope mounts, which rotate

on an axis exactly parallel to the earth's axis.

Fig 1.2 Polar Trackers

3

Horizontal Axle

Several manufactures can deliver single axis horizontal axis trackers which may be

oriented by either passive or active mechanisms, depending upon manufacturer. Panels are

mounted upon the tube, and the tube will rotate on its axis to track the apparent motion of the

sun through the day.These devices are less effective at higher latitudes. The principal

advantage is the inherent robustness of the supporting structure and the simplicity of the

mechanism.

FIG 1.3 Horizontal Axle

Active Trackers

Active Trackers use motors and gears to direct the tracker as commanded by a

controller responding to the solar direction.

Fig: 1.4 Active trackers

4

Passive Trackers

Passive trackers use a low boiling point compressed gas fluid that is driven to one

side or the other (by solar heat creating gas pressure) to cause the tracker to move in

response to an imbalance. As this is a non-precision orientation it is unsuitable for certain

types of concentrating photovoltaic collectors.

5

CHAPTER 2

AIM AND SCOPE OF THE PROJECT

2.1 Aim And Scope of The Project

From many centuries, sun has been the primary source of energy for the globe.

Technically, solar energy can be defined as Electromagnetic energy transmitted from the sun

( solar radiation).The amount of energy that reaches the earth is equal to one billionth of total

solar energy generated. But is that small? No. The amount of energy which strikes the

surface of the earth in one day exceeds daily consumption by 10,000 to 15,000 times. In

other words, the amount of solar energy intercepted by the earth every minute is greater than

the amount of energy the world uses in fossil fuels each year.

Moreover, of all the renewable energy sources available, solar energy has the

smallest environmental impacts. Electricity produced from photovoltaic cells does not result

in air or water pollution, deplete natural resources, or endanger animal or human health.

In spite of these benefits, man is not able to use this energy completely and

economically. Two billion people in the world still have no access to electricity. For most of

them, solar energy would be their cheapest electricity source, but they cannot afford it. This

is because the price of electricity produced from solar cells is still significantly more

expensive than it is from fossil fuels like coal and oil. This is because of cost involved in

converting the solar energy into required form of electrical energy and low efficiency of

solar system i.e., the output from the solar system is not completely sufficient for our needs.

The problem here is that the sun’s position is not constant throughout the day. The

output from the solar system depends on the intensity of sunlight and the angle at which

radiation is being incident. Hence there is a need to track the sun inorder to produce

maximum output throughout the day. The solution to the problem is our project “SOLAR

TRACKING SYSTEM”.

6

2.2 objective of the project

The main aim of our project is to make the panel to rotate according to the sun’s

direction from morning to evening automatically so that the panel grabs the solar enenrgy to

maximum extent possible throughout the day.

Intelligent Solar Tracking System For maximizing The Energy is used to generate

power from sunlight and can be used it by storing the generated power. This method of

power generation is simple and is taken from natural resource. This need only maximum

sunlight to generate power. This project helps for power generation by setting the equipment

to get maximum sunlight automatically. This system is tracking for maximum intensity of

light. When there is decrease in intensity of light, this system automatically changes its

direction to get maximum intensity of light.

Here we use two sensors in two directions to sense the direction of maximum intensity of

light. The difference between the outputs of the sensors is given to the micro controller unit,

which is used for tracking and generating power from sunlight. It will process the input voltage

from the comparison circuit and control the direction in which the motor has to be rotated so that

it will receive maximum intensity of light from the sun. The power generated from this process

is then stored in a lead acid battery and is made to charge an emergency light and is made to

glow.

7

CHAPTER 3

MATERIAL AND METHOD USED

3.1 Block Diagram

The block diagram of Intelligent Solar tracking System for Maximising The Energy

is as shown below. The different components used to build the System are explained in

different sections below.

Fig 3.1 Block diagram of Intelligent Solar Tracking System for Maximising The

Energy

8

POWER SUPPLYPOWER SUPPLY

STEPPER MOTOR

STEPPER MOTOR

LOADLOAD

ULN 2003

DRIVER

ULN 2003

DRIVER

AT89C52

M ICRO

CONTROLLER

SOLARPANEL

BATTERY

LDR2LDR2

LDR1LDR1

RS-232

LDR 2

LDR 1

3.1.1 Interfacing Diagram

SOLARPANEL

5

4

E

37

O

5

36

R

R 2

2 . 2 k

8

3

16

18

328

20

C 4

10u

12

7

26

12

Vcc(+5v)

15

19

N

Vcc(+5V)

33

40

+5V

C

1 2

9

2

O

39

27

5

24

O

89

R 2

2 . 2 k

23

13

34

C

116

3

4

R

4

I

6

7

C 3

10u

C

16

3

10

Q 1

BC 547

LDR

16

1

22

C 1

10u

15

11

R13

17

35

9

O/P

L

28

21

2

C 2

10u

14

10

R 1

10 k

7

31

1 2

LDR

1

MOTOR14

ULN

DRIVER

15

9

Vcc(+12V)

I

5

Vcc

R 1

10 k

1 2

2

2

M

2003

A

229

6

11

38

STEPPER

12

3

25

13

1

Q 1

BC 547

TVcc(+5V)

10

14

L

30

5

1 2

8

O/P

Fig 3.2 Interfacing diagram of Intelligent Solar Tracking System for Maximizing the

Energy

9

3.2 Micro Controller 8052

A micro controller is an integrated chip that is often part of an embedded system. It

includes a CPU, RAM, ROM, timers and i/o ports like a standard computer, but because they

are designed to execute only a single specific task to control a single system, they are much

smaller and simplified so that they can include all functions required on a single chip.

AT89C52 is a popular version of 8052. The Atmel AT89C52 is an 8052-based is a

low-power, high performance CMOS 8bit microcontroller with 32 I/O Lines, 2

Timers/Counters, 6 Interrupts/2 Priority Levels, UART, 4K Bytes Flash Memory, 128 Bytes

On-chip RAM. The device is manufactured using Atmel’s high-density nonvolatile memory

technology and is compatible with the industry-standard MCS-51 instruction set and pin out.

The on-chip Flash allows the program memory to be reprogrammed in-system or by a

conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with

Flash on a monolithic chip, the Atmel AT89C52 is a powerful microcomputer which

provides a highly-flexible and cost-effective solution to many embedded control

applications.

3.3 Light Emitting Diode (LED)

A light-emitting diode, usually called an LED, is a semiconductor diode that emits

incoherent narrow-spectrum light when electrically biased in the forward direction of the p-n

junction, as in the common LED circuit. This effect is a form of electroluminescence.

A LED is usually a small area light source, often with extra optics added to the chip

that shapes its radiation pattern. LEDs are often used as small indicator lights on electronic

devices and increasingly in higher power applications such as flashlights and area lighting.

The color of the emitted light depends on the composition and condition of the semi

conducting material used, and can be infrared, visible, or ultraviolet. LEDs can also be used

as a regular household light source. Besides lighting, interesting applications include

sterilization of water and disinfection of devices.

10

3.3.1 Physical function of LED

Like a normal diode, the LED consists of a chip of semiconducting material

impregnated, or doped, with impurities to create a p-n junction. As in other diodes, current

flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse

direction. Charge-carriers—electrons and holes—flow into the junction from electrodes with

different voltages. When an electron meets a hole, it falls into a lower energy level, and

releases energy in the form of a photon.

The wavelength of the light emitted, and therefore its color, depends on the band gap

energy of the materials forming the p-n junction. In silicon or germanium diodes, the

electrons and holes recombine by a non-radiative transition which produces no optical

emission, because these are indirect band gap materials. The materials used for the LED

have a direct band gap with energies corresponding to near-infrared, visible or near-

ultraviolet light.

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

Advances in materials science have made possible the production of devices with ever-

shorter wavelengths, producing light in a variety of colors.

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

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

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

are transparent to the emitted wavelength, and backed by a reflective layer, increase the LED

efficiency. The refractive index of the package material should match the index of the

semiconductor, otherwise the produced light gets partially reflected back into the

semiconductor, where it may be absorbed and turned into additional heat, thus lowering the

efficiency. This type of reflection also occurs at the surface of the package if the LED is

coupled to a medium with a different refractive index such as a glass fiber or air. The

refractive index of most LED semiconductors is quite high, so in almost all cases the LED is

coupled into a much lower-index medium. The large index difference makes the reflection

quite substantial (per the Fresnel coefficients), and this is usually one of the dominant causes

11

of LED inefficiency. Often more than half of the emitted light is reflected back at the LED-

package and package-air interfaces. The reflection is most commonly reduced by using a

dome-shaped (half-sphere) package with the diode in the center so that the outgoing light

rays strike the surface perpendicularly, at which angle the reflection is minimized. An anti-

reflection coating may be added as well. The package may be cheap plastic, which may be

colored, but this is only for cosmetic reasons or to improve the contrast ratio; the color of the

packaging does not substantially affect the color of the light emitted. Other strategies for

reducing the impact of the interface reflections include designing the LED to reabsorb and

reemit the reflected light (called photon recycling) and manipulating the microscopic

structure of the surface to reduce the reflectance, either by introducing random roughness or

by creating programmed moth eye surface patterns.

Conventional LEDs are made from a variety of inorganic semiconductor materials,

producing the following colors:

Fig 3.3 LED

Aluminium gallium arsenide (AlGaAs) — red and infrared

Aluminium gallium phosphide (AlGaP) — green

Aluminium gallium indium phosphide (AlGaInP) — high-brightness orange-red,

orange, yellow, and green

Gallium arsenide phosphide (GaAsP) — red, orange-red, orange, and yellow

Gallium phosphide (GaP) — red, yellow and green

12

Gallium nitride (GaN) — green, pure green (or emerald green), and blue also white

(if it has an AlGaN Quantum Barrier)

Indium gallium nitride (InGaN) — 450 nm - 470 nm — near ultraviolet, bluish-green

and blue

Silicon carbide (SiC) as substrate — blue

Silicon (Si) as substrate — blue (under development)

Sapphire (Al2O3) as substrate — blue

Zinc selenide (ZnSe) — blue

Diamond (C) — ultraviolet

Aluminium nitride (AlN), aluminum gallium nitride (AlGaN), aluminium gallium

indium nitride (AlGaInN) — near to far ultraviolet (down to 210 nm)

With this wide variety of colors, arrays of multicolor LEDs can be designed to produce

unconventional color patterns.

3.3.2 Efficency and operational parameters

Most typical LEDs are designed to operate with no more than 30–60 mill watts of

electrical power. Around 1999, Philips Lumileds introduced power LEDs capable of

continuous use at one watt. These LEDs used much larger semiconductor die sizes to handle

the large power inputs. Also, the semiconductor dies were mounted onto metal slugs to allow

for heat removal from the LED die.

One of the key advantages of LED-based lighting is its high efficiency, as measured

by its light output per unit power input. White LEDs quickly matched and overtook the

efficiency of standard incandescent lighting systems. In 2002, Lumileds made five-watt

LEDs available with a luminous efficacy of 18–22 lumens per watt (lm/W). For comparison,

a conventional 60–100 watt incandescent light bulb produces around 15 lm/W, and standard

fluorescent lights produce up to 100 lm/W. (The luminous efficacy article discusses these

comparisons in more detail.)

In September 2003, a new type of blue LED was demonstrated by the company Cree,

Inc. to provide 24 mW at 20 mA. This produced a commercially packaged white light giving

13

65 lumens per watt at 20 mA, becoming the brightest white LED commercially available at

the time, and more than four times as efficient as standard incandescent. In 2006 they

demonstrated a prototype with a record white LED luminous efficacy of 131 lm/W at 20

mA. Also, Seoul Semiconductor has plans for 135 lm/W by 2007 and 145 lm/W by 2008,

which would be approaching an order of magnitude improvement over standard

incandescent and better even than standard fluorescents. Nichia Corporation has developed a

white light LED with luminous efficacy of 150 lm/W at a forward current of 20 mA.

It should be noted that high-power (≥ 1 watt) LEDs are necessary for practical

general lighting applications. Typical operating currents for these devices begin at 350 mA.

The highest efficiency high-power white LED is claimed by Philips Lumileds Lighting Co.

with a luminous efficacy of 115 lm/W (350 mA).

3.3.3 Considerations in use

Unlike incandescent light bulbs, which light up regardless of the electrical polarity,

LEDs will only light with correct electrical polarity. When the voltage across the p-n

junction is in the correct direction, a significant current flows and the device is said to be

forward-biased. If the voltage is of the wrong polarity, the device is said to be reverse biased,

very little current flows, and no light is emitted. Some LEDs can be operated on an

alternating current voltage, but they will only light with positive voltage, causing the LED to

turn on and off at the frequency of the AC supply.

3.3.3.1 Advantages of using LEDs

LEDs produce more light per watt than incandescent bulbs; this is useful in battery

powered or energy-saving devices.

LEDs can emit light of an intended color without the use of color filters that

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

The solid package of the LED can be designed to focus its light. Incandescent and

fluorescent sources often require an external reflector to collect light and direct it in a

usable manner.

14

When used in applications where dimming is required, LEDs do not change their

color tint as the current passing through them is lowered, unlike incandescent lamps,

which turn yellow.

LEDs are ideal for use in applications that are subject to frequent on-off cycling,

unlike fluorescent lamps that burn out more quickly when cycled frequently, or HID

lamps that require a long time before restarting.

LEDs, being solid state components, are difficult to damage with external shock.

Fluorescent and incandescent bulbs are easily broken if dropped on the ground.

LEDs can have a relatively long useful life. One report estimates 35,000 to 50,000

hours of useful life, though time to complete failure may be longer. Fluorescent tubes

typically are rated at about 30,000 hours, and incandescent light bulbs at 1,000–2,000

hours LEDs mostly fail by dimming over time, rather than the abrupt burn-out of

incandescent bulbs.

LEDs light up very quickly. A typical red indicator LED will achieve full brightness

in microseconds; Philips Lumileds technical datasheet DS23 for the Luxeon Star

states "less than 100ns." LEDs used in communications devices can have even faster

response times.

LEDs can be very small and are easily populated onto printed circuit boards.

LEDs do not contain mercury, unlike compact fluorescent lamps.

3.3.3.2 Disadvantages of using LEDs

LEDs are currently more expensive, price per lumen, on an initial capital cost basis,

than more conventional lighting technologies. The additional expense partially stems

from the relatively low lumen output and the drive circuitry and power supplies

needed. However, when considering the total cost of ownership (including energy

and maintenance costs), LEDs far surpass incandescent or halogen sources and begin

to threaten compact fluorescent lamps. In December 2007, scientists at Glasgow

University claimed to have found a way to make Light Emitting Diodes brighter and

use less power than energy efficient light bulbs currently on the market by imprinting

holes into billions of LEDs in a new and cost effective method using a process

known as nano imprint lithography.

15

LED performance largely depends on the ambient temperature of the operating

environment. Over-driving the LED in high ambient temperatures may result in

overheating of the LED package, eventually leading to device failure. Adequate heat-

sinking is required to maintain long life. This is especially important when

considering automotive, medical, and military applications where the device must

operate over a large range of temperatures, and is required to have a low failure rate.

LEDs must be supplied with the correct current. This can involve series resistors or

regulated power supplies.

The spectrum of some white LEDs differs significantly from a black body radiator,

such as the sun or an incandescent light. The spike at 460 nm and dip at 500 nm can

cause the color of objects to be perceived differently under LED illumination than

sunlight or incandescent sources, due to metamerism. Color rendering properties of

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

white LEDs.

LEDs do not approximate a "point source" of light, so cannot be used in applications

needing a highly collimated beam. LEDs are not capable of providing divergence

below a few degrees. This is contrasted with commercial ruby lasers with

divergences of 0.2 degrees or less.[30] This can be corrected by using lenses and other

optical devices.

There is increasing concern that blue LEDs and white LEDs are now capable of

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

specifications such as ANSI/IESNA RP-27.1-05: Recommended Practice for Photo

biological Safety for Lamp and Lamp Systems.

3.3.4 LED applications

Some of these applications are further elaborated upon in the following text.

Remote controls, such as for TVs and VCRs, often use infrared LEDs.

Glow lights, as a more expensive but longer lasting and reusable alternative to Glow

sticks.

Movement sensors, for example in optical computer mice

The Nintendo Wii's sensor bar uses infrared LEDs.

16

In optical fiber and Free Space Optics communications.

Toys and recreational sporting goods, such as the Flash flight

Lumalive, a photonic textile

In pulse oximeters for measuring oxygen saturation

LED phototherapy for acne using blue or red LEDs has been proven to significantly

reduce acne over a 3 month period.

Some flatbed scanners use an array of red, green, and blue LEDs rather than the

typical cold-cathode fluorescent lamp as the light source. Having independent control

of three illuminated colors allows the scanner to calibrate itself for more accurate

color balance, and there is no need for warm-up.

Computers, for hard drive activity and power on. Some custom computers feature

LED accent lighting to draw attention to a given component. Many computer

manufacturers use LEDs to tell the user its current state. One example would be the

Mac, which tells its user when it is asleep by fading the LED activity lights in and

out, in and out.

Sterilization of water and other substances using UV light.

3.3.5 LED schematic symbol

3.4 Light Dependent Resistor (LDR)

A photo resistor is made of a high resistance semiconductor. If light falling on the

device is of high enough frequency, photons absorbed by the semiconductor give bound

electrons enough energy to jump into the conduction band. The resulting free electron (and

its hole partner) conduct electricity, thereby lowering resistance.

17

3.4.1 Physical function of LDR

A photo resistor or Light Dependent Resistor or CDS Cell is an electronic component

whose resistance decreases with increasing incident light intensity. It can also be referred to

as a photoconductor.

A photo resistor is made of a high resistance semiconductor. If light falling on the

device is of high enough frequency, photons absorbed by the semiconductor give bound

electrons enough energy to jump into the conduction band. The resulting free electron (and

its hole partner) conduct electricity, thereby lowering resistance.

Fig 3.4 Light dependent resistor(LDR)

A photoelectric device can be either intrinsic or extrinsic. An intrinsic semiconductor

has its own charge carriers and is not an efficient semiconductor, eg. Silicon. In intrinsic

devices, the only available electrons are in the valence band, and hence the photon must have

enough energy to excite the electron across the entire band gap. Extrinsic devices have

impurities added, which have a ground state energy closer to the conduction band — since

the electrons don't have as far to jump, lower energy photons (i.e. longer wavelengths and

lower frequencies) are sufficient to trigger the device. If a sample of silicon has some of its

18

atoms replaced by phosphorus atoms (impurities), there will be extra electrons available for

conduction. This is an example of an extrinsic Semiconductor.

3.4.2 Cadmium sulfide cells

Cadmium sulfide (CdS) cells rely on the material's ability to vary its resistance

according to the amount of light striking the cell. The more light that strikes the cell, the

lower the resistance. Although not accurate, even a simple CdS cell can have a wide range of

resistance from less than 100 Ω in bright light to in excess of 10 MΩ in darkness. Many

commercially available CdS cells have peak sensitivity in the region of 500nm - 600nm

(green light). The cells are also capable of reacting to a broad range of frequencies, including

infrared (IR), visible light, and ultraviolet (UV). They are often found on street lights as

automatic on/off switches. They were once even used in heat-seeking missiles to sense for

targets.

Standard cadmium based LDRs have a frequency response that varies according to

light level, but is routinely below 1Hz, so they are unsuitable for data links and picture

scanning. Silicon based photodiodes and phototransistors are orders of magnitude faster.

Probably the best known LDR is the ORP12. Smaller cheaper devices are more popular

today.

3.4.3 Circuit symbol

Fig 3.4 Circuit symbol of LDR

19

3.4.4 Applications

Photo resistors come in many different types. Inexpensive cadmium sulfide cells can

be found in many consumer items such as camera light meters, clock radios, security alarms,

street lights and outdoor clocks.

They are also used in some dynamic compressors together with a small incandescent

lamp or light emitting diode to control gain reduction.

Lead sulfide- and indium antimonide-LDR are used for the mid infrared spectral

region. At the other end of the scale, Ge:Cu photoconductors are among the best far-infrared

detectors available, and are used for infrared astronomy and infrared spectroscopy.

Continues power dissipation is 80mW and the Maximum voltage which can be applied to its

100V

3.5 Stepper Motor

A stepper motor is an electromechanical device which converts electrical pulses into

discrete mechanical movements. The stepper motor is used for position control in

applications like disk drives and robotics.

The name stepper is used because this motor rotates through a fixed angular step in response

to each input current pulse received by its controller. In recent years, there has been wide-

spread demand of stepper motors because of the explosive growth of computer industry.

Their popularity is due to the fact that they can be controlled directly by computers,

microprocessors and programmable controllers. Stepper motors are ideally suited for

situations where precise position and precise speed control are required without the use of

closed-loop feedback. When a definite number of pulses are supplied, the shaft turns through

a definite known angle. This fact makes the motor well suited for open-loop position control

because no feedback need be taken from the output shaft.

Every stepper motor has a permanent magnet rotor also known as shaft surrounded by a

stator poles. The most common stepper motor s has four stator windings that are paired with

a center-tapped. This type of stepper motor is commonly referred to as a four-phase stepper

20

motor. The center tap allows a change of current direction in each of two coils when a

winding is grounded, there by resulting in a polarity change of the stator.

The shaft or spindle of a stepper motor rotates in discrete step increments when

electrical command pulses are applied to it in the proper sequence. The direction of the

rotation is determined by the stator poles. The stator poles are determined by the current sent

through the wire coils. As the polarity of the current is changed, the polarity is also changed

causing the reverse motion of the motor The sequence of the applied pulses is directly

related to the direction of motor shafts rotation. The speed of the motor shafts rotation is

directly related to the frequency of the input pulses and the length of rotation is directly

related to the number of input pulses applied. While a conventional motor shaft moves

freely, stepper motor shaft moves in a fixed repeatable increment which allows one to move

it to a precise position. This repeatable fixed movement is possible as a result of basic

magnetic theory where poles of he same polarity repel and opposite poles attract.

The stepper motor converts digital signals into fixed mechanical increment of

motion. It thereby provides a natural interface with the digital computer. It is a synchronous

motor such that the rotor rotates a specific incremental number of degrees for each pulse

input given to the motor system. These motors can provide accurate positioning without the

need of position feedback sensors when compared to other motors. The position is known

simply by keeping track of the input step pulses. Usually, position information can be

obtained simply by keeping count of the pulses sent to the motor thereby eliminating the

need of expensive position sensors and feedback controls.

Stepper motors are rated by the torque they produce, step angle, steps per second and the

number of teeth on rotor.

21

The minimum degree of rotation with which the stepper motor turns for a single

pulse if supply to one wire or a pair is called step angle. The minimum step angle is always a

function of the number of teeth on rotor .i.e., the smaller the step angle the more teeth the

rotor possess.

Steps per complete revolution = Number of phases (coils) x

Number of teeth on rotor

Smaller the step angle, greater the number of steps per revolution and higher the resolution

or the accuracy of positioning obtained. The step angles can be as small as 0.72˚ or as large

as 90˚. The motor speed is measured in steps per second.

Steps per second = (Revolution per minute x steps per Revolution)/ 60

Stepping motors has the extraordinary ability to operate at very high speeds (up to 20,000

steps per second) and yet to remain fully in synchronism with the command pulses, when the

pulse rate is high, the shaft rotation seems continuous. If the stepping rate is increased too

quickly, the motor loses synchronism and stops. Stepper motors are designed to operate for

long periods with the rotor held in a fixed position and with rated current flowing in the

stator windings whereas for most of the other motors, this results in collapse of back emf and

a very high current which can lead to a quick burn out.

A stepper motor is a special kind of motor that moves in individual steps which are

usually .9 degrees each. Each step is controlled by energizing coils inside the motor causing

the shaft to move to the next position. Turning these coils on and off in sequence will cause

the motor to rotate forward or reverse. The time delay between each step determines the

motor's speed. Steppers can be moved to any desired position reliably by sending them the

proper number of step pulses.

Fig 3.5 Stepper motor

22

3.5.1 Back emf

A motor is a machine which converts electric energy into mechanical energy. Its

action is based on the principle that when a current carrying conductor is placed in a

magnetic field, it experiences a mechanical force whose direction is given by Fleming’s left

hand rule.

Fleming's left hand rule (for electric motors) shows the direction of the resultant

motion of the motor on a conductor carrying a current in a magnetic field.

The left hand is held with the thumb, index finger and middle finger mutually at right angles.

The First finger represents the direction of the magnetic Field.

The Second finger represents the direction of the Current (in the classical direction, from

positive to negative).

The Thumb represents the direction of the Thrust or resultant Motion.

Energy conversion is not possible unless there is some opposition whose overcoming

provides the necessary means for such conversion. In case of generator it was the magnetic

drag which provided the necessary opposition. The equivalent in the case of a motor is called

as the back emf.

As soon as the armature or the rotor starts rotating, dynamically (or motionally)

induced emf is produced in the armature conductors. The direction of this induced emf as

found by the Fleming’s right hand rule, is in direct opposition to the applied voltage. That is

why this is known as BACK EMF or counter emf. The electrical work done in overcoming

this opposition is converted into mechanical energy developed in the armature. Therefore, it

is obvious that but for the production of this opposing emf energy could not have been

possible.

When the armature rotates the conductors also rotate and hence cut the flux. In

accordance with the laws of electromagnetic induction, emf is induced in them whose

direction, is in opposition to the applied voltage. This induced emf is called back emf.

Obviously supply voltage has to drive armature current against the opposition of back emf.

These motors also suffer from EMF, which means that once the coil is turned off it

starts to generate current because the motor is still rotating. There needs to be an explicit

23

way to handle this extra current in a circuit otherwise it can cause damage and affect

performance of the motor.

The ULN2003 / MC1413 is a 7-bit 50V 500mA TTL-input NPN darlington driver.

This is more than adequate to control a four phase unipolar stepper motor such as the

KP4M4-001.

Fig 3.6 Pin diagram of ULN 2003

It is recommended to connect a 12v zener diode between the power supply and VDD

(Pin 9) on the chip, to absorb reverse (or "back") EMF from the magnetic field collapsing

when motor coils are switched off. (See Douglas W. Jones' rather more sophisticated

example)

3.5.2 Driving a stepper motor

The four leads of the stator winding are controlled by the four bits of the 8051 port

(p1.0-p1.3). However, since the 8051 lacks sufficient current to drive the stepper motor

windings, we must use a driver such as uln2003a to energize the stator. Instead of the

uln2003a, we could have used transistors as drivers.

However, notice that if transistors are used as drivers, we must also use diodes to

take care of inductive current generated when the coil is turned off. One reason that the

uln2003a is preferable to the use of transistors as drivers is that the uln2003 has as internal

diode to take care of back emf.

24

Most stepper motor circuits that are available online have a bunch of transistors,

Sometimes power transistors too quite a complicated circuit that drives you away far from

using it. Well i felt for most robotic use the stepper motor can be driven by a simple

ULN2003 IC that costs just 12 bucks in my backyard.

While controlling the stepper motor with an embedded or distributed microcontroller for a

specific application, the controlling

signals from the controller to the stepper

motor must be boosted up using a driven

circuitry in order to have the

compatibility between them. In the

following figure, we show that the stepper

motor is driven with ULN 2003 driven

circuitry.

Fig:3.7 Driving a stepper motor

Fig: 3.8 Connection ckt to Stepper motor

The following steps show the 8051 connection to the stepper motor

Use an ohmmeter to measure the resistance of the leads. This should identify which COM

leads are connected to which winding leads.

The common wire(s) are connected to positive side of the motor’s power supply.

25

To distinguish common wire from a coil-end wire is by measuring the resistance.

Resistance between common wire and coil-end wire is always half of what it is between coil-

end and coil-end wires. Just take your multimeter and check the resistance between the

wires. One wire is a common and it must bear a resistance of 75 ohms with all the other

wires then that is the common wire. This is due to the fact that there is actually twice the

length of coil between the ends and only half from center (common wire) to the end.

A pulse is an electrical signal that repeats ON and OFF voltages as shown in the

illustration below. Each cycle of ON and OFF (1 cycle) is called a “pulse.” Normally, 5 volts

is used. ON is high and OFF is low.

3.5.3 Working principle of stepper motor

To make a stepper motor rotate, you must constantly turn on and off the coils. If you

simply energize one coil the motor will just jump to that position and stay there resisting

change. This energized coil pulls full current even though the motor is not turning. The

stepper motor will generate a lot of heat at standstill. The ability to stay put at one position

rigidly is often an advantage of stepper motors. The torque at standstill is called the holding

torque.

Because steppers can be controlled by turning coils on and off, they are easy to

control using digital circuitry and microcontroller chips. The controller simply energizes the

coils in a certain pattern and the motor will move accordingly. At any given time the

computer will know the position of the motor since the number of steps given can be

tracked. This is true only if some outside force of greater strength than the motor has not

interfered with the motion.

When a phase winding of a stepper motor is energized with current, a magnetic flux

is developed in the stator. The direction of this flux is determined by the “right hand rule”

which states: “if the coil is grasped in the right hand with fingers pointing in the direction of

the current in the winding (the thumb is extended at right angle to the fingers), then the

thumb will point in the direction of the magnetic field.”

26

The number of times the stepper motor turns on and off depends on the number of

teeth present on the rotor and this is shown with an example in which four-step sequence is

considered. Four-step sequence means, after completing every four steps, the rotor moves

only one tooth pitch. In this example, the rotor has only 25 teeth and so it makes 100 steps

for one complete rotation.

Figure 1 illustrates one complete rotation of a stepper motor.  At position 1, we can

see that the rotor is beginning at the upper electromagnet, which is currently active (has

voltage applied to it).  To move the rotor clockwise (CW), the upper electromagnet is

deactivated and the right electromagnet is activated, causing the rotor to move 90 degrees

CW, aligning itself with the active magnet.  This process is repeated in the same manner at

the south and west electromagnets until we once again reach the starting position.

Fig 3.9 Principle of stepper motor

3.5.3.1 Illustration of Stepper motor

You may double the resolution of some motors by a process known as "half-

stepping".  Instead of switching the next electromagnet in the rotation on one at a time, with

half stepping you turn on both electromagnets, causing an equal attraction between, thereby

doubling the resolution. 

27

3.5.4 Types of stepper motor

There are basically two types of stepper motors depending on the arrangements of the

electromagnetic coils. They are unipolar and bipolar

3.5.4.1 Unipolar motors

In a unipolar stepper motor, there are four separate electromagnets. To turn the

motor, first coil "1" is given current, then it's turned off and coils 2 is given current, and then

coil 3, then 4, and then 1 again in a repeating pattern. Current is only sent through the coils

in one direction; thus the name unipolar.

A unipolar stepper motor will have 5 (or 6) wires coming out of it. Four of those

wires are each connected to one end of one coil. The extra wire (or 2) is called "common"

and is connected to the other ends of all four coils. To operate the motor, the "common" wire

is connected to the supply voltage, and the other four wires are connected to ground through

transistors, so the transistors control whether current flows or not. A microcontroller or

stepper motor controller is used to activate the transistors in the right order. These are the

cheapest way to get precise angular movements.

3.5.4.2 Bipolar motors

In a bipolar motor, there are only two coils, and current must be sent through a coil

first in one direction and then in the other direction; thus the name bipolar. Bipolar motors

need more than 4 transistors to operate them, but they are also more powerful than a unipolar

motor of the same weight. To be able to send current in both directions, engineers can use an

H-bridge to control each coil or a step motor driver chip. This type of motor is not regularly

used for robotics.

Bipolar controllers can switch between supply voltage, ground, and unconnected.

Unipolar controllers can only connect or disconnect a cable, because the voltage is already

hard wired. Unipolar controllers need center-tapped windings.

It is possible to drive unipolar stepper motors with bipolar drivers. The idea is to connect the

output pins of the driver to 4 transistors. The transistor must be grounded at the emitter and

28

the driver pin must be connected to the base. Collector is connected to the coil wire of the

motor.

3.6 stepper motor advantages and disadvantages

3.6.1 Advantages

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

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

Precision 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.

Excellent response to starting/stopping/reversing.

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

motor is simply dependent on the life of the bearing.

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

the motor simpler and less costly to control.

It is possible to achieve very slow speed synchronous rotation with a load that is

directly coupled to the shaft.

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

frequency of the input pulses.

3.6.2 Disadvantage

Resonances can occur if not properly controlled

Not easy to operate at extremely high speeds.

This motor can also be heated at standing because of the torque require to hold it in

position.

3.7 when to use stepper motors

29

Computer-controlled stepper motors are one of the most versatile forms of positioning

systems, particularly when digitally controlled as part of a servo system. Stepper motors can

be used to advantage where you need to control rotation angle, position and synchronism.

Stepper motors are used in floppy disk drives, flatbed scanners, typewriters, and printers, x-y

plotters, milling machines, valve actuators, medical equipment, fax machines, automotives

and many more devices.

3.8 Applications of stepper motor

Stepper motors are used for operation control in computer peripherals, textile

industry, IC fabrication and robotics etc. applications requiring incremental motion are

typewriters, line printers, tape drives, numerically-controlled machine tools, process control

systems and X-Y plotters.. Stepper motors also perform countless tasks outside the computer

industry. It includes commercial, military and medical applications where these motors

perform such functions as mixing, cutting, striking, metering, blending and purging. They

also take part in the manufacture of packed food stuffs, commercial end-products and even

the production of science fiction movies.

3.9 ULN Stepper motor driver

ULN is mainly suited for interfacing between low-level circuits and multiple

peripheral power loads. The series ULN20XX high voltage, high current darlington arrays

feature continuous load current ratings. The driving circuitry in- turn decodes the coding and

conveys the necessary data to the stepper motor, this module aids in the movement of the

arm through steppers.

30

3.10 Pin connection of ULN Steeper motor Driver

The driver makes use of the ULN2003 driver IC, which contains an array of 7 power

Darlington arrays, each capable of driving 500mA of current. At an approximate duty cycle,

depending on ambient temperature and number of drivers turned on, simultaneously typical

power loads totaling over 230w can be controlled.

The device has base resistors, allowing direct connection to any common logic family.

All the emitters are tied together and brought out to a separate terminal. Output protection

diodes are included; hence the device can drive inductive loads with minimum extra

components. Typical loads include relays, solenoids, stepper motors, magnetic print

hammers, multiplexed LED, incandescent displays and heaters.

Fig 3.11 Driving a Stepper Motor using ULN 2003

31

Note that the first pin (identified in the procedure shown above) is connected to D0 of the

parallel port (through the ULN2003, of course). Each successive pin of the stepper motor is

connected to successive data lines on the parallel port. If this order is not correct, the motor

will not rotate, but will wiggle around from side to side. The clamp circuit shown does not

connect the clamp directly to the supply voltage. Instead, it uses a zener diode. This ensures

that the decaying current in the coils are not abruptly cut off, which produces a lot of heat.

It is simple, it involves setting the bits on the port on and off in a specific sequence. The step

sequence is given below for full step and half steps. At any time only one pin is active in the

full step.

Table:3.1:Full step

Table:3.2:Half step

The difference between half step and full step is that for the same step rate, half-step

gives you half the speed, twice the resolution, and roughly twice the power consumption. It

32

Full Step

Step No. D0 D1 D2 D3

1 1 0 0 0

2 0 1 0 0

3 0 0 1 0

4 0 0 0 1

Half Step

Step No. D0 D1 D2 D3

1 1 0 0 0

2 1 1 0 0

3 0 1 0 0

4 0 1 1 0

5 0 0 1 0

6 0 0 1 1

7 0 0 0 1

8 1 0 0 1

also gives you twice the torque. To reverse the direction of the motor, send the sequence in

reverse order.

3.9.1 Features of ULN 2003

Seven Darlington per package.

Output current 500ma per driver (600ma peak).

Output voltage 50v.

Integrated suppression diodes for inductive loads.

Outputs can be paralleled for high current TTL/CMOS/DTL compatible inputs.

Inputs pinned opposite outputs to simplify layout.

Transient protected outputs.

Dual In-Line plastic package or small-Outline IC package.

3.10 Source Coding

#include<reg51.h>

//port0 for (load)::port1 for ldrs(sensors)::port2 for stepper motor::port3 for serial

sbit ldr1=P2^0;

sbit ldr2=P2^1; //sensors for light

delay(unsigned int);

clock();

anticlock();

main() //LDR : WHEN LIGHT FALLS IT ACTS AS

CONDUCTOR && WHEN LIGHT DOESENT FALLI IT ACTS AS RESISTOR

{

// WHEN NO LIGHT OUTPUT IS =1;

33

// WHEN LIGHT OUTPUT IS =0;

while(1)

{

///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

if(ldr1==1&&ldr2==0)

{ //MAKING THE LOAD ON BY

SOLAR

clock();

}

//////////////////////////////////////////////////////////////////////////////////////////////////

if(ldr1==0&&ldr2==1)

{

anticlock();

}

} //WHILE1

}//MAIN

clock()

{

P0=0X11;

delay(75);

P0=0X22;

delay(75);

P0=0X44;

delay(75);

P0=0X88;

delay(75);

}

34

anticlock()

{

P0=0X88;

delay(75);

P0=0X44;

delay(75);

P0=0x22;

delay(75);

P0=0X11;

delay(75);

}

delay(unsigned int time)

{

unsigned int i,j;

for(i=0;i<time;i++)

for(j=0;j<1275;j++);

}

35

3.11 Power supply

There are many types of power supply. Most are designed to convert high voltage

AC mains electricity to a suitable low voltage supply for electronics circuits and other

devices. A power supply can by broken down into a series of blocks, each of which performs

a particular function.

For example a 5V regulated supply can be shown as below

Fig 3.12 Block Diagram of a Regulated Power Supply System

Similarly, 12v regulated supply can also be produced by suitable selection of the

individual elements. Each of the blocks is described in detail below and the power supplies

made from these blocks are described below with a circuit diagram and a graph of their

output:

3.11.1 Transformer

A transformer steps down high voltage AC mains to low voltage AC. Here we are

using a center-tap transformer whose output will be sinusoidal with 36volts peak to peak

value.

Fig: 3.13 Output Waveform of transformer

36

The low voltage AC output is suitable for lamps, heaters and special AC motors. It is

not suitable for electronic circuits unless they include a rectifier and a smoothing capacitor.

The transformer output is given to the rectifier circuit.

3.11.2 Rectifier

A rectifier converts AC to DC, but the DC output is varying. There are several types

of rectifiers; here we use a bridge 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. 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 unidirectional.

Fig 3.14 The output waveform of the rectifier is shown as below

37

The varying DC output is suitable for lamps, heaters and standard motors. It is not

suitable for electronic circuits unless they include a smoothing capacitor.

3.11.3 Smoothing

The smoothing block smoothes the DC from varying greatly to a small ripple.

The ripple voltage is defined as the deviation of the load voltage from its DC value.

Smoothing is also named as filtering.

Filtering is frequently effected by shunting the load with a capacitor. The action of

this system depends on the fact that the capacitor stores energy during the conduction period

and delivers this energy to the loads during the no conducting period. In this way, the time

during which the current passes through the load is prolongated, and the ripple is

considerably decreased. The action of the capacitor is shown with the help of waveform.

Fig 3.15The waveform of the rectified output after smoothing is given below:

38

3.11.4 Regulator

Regulator eliminates ripple by setting DC output to a fixed voltage.Voltage regulator ICs are

available with fixed (typically 5, 12 and 15V) or variable output voltages. Negative voltage

regulators are also available

Many of the fixed voltage regulator ICs has 3 leads (input, output and high impedance).

They include a hole for attaching a heat sink if necessary. Zener diode is an example of fixed

regulator which is shown here.

3.10.1 REGULATOR

Transformer + Rectifier + Smoothing + Regulator:

39

3.12 FLOW CHART

V

CHAPTER -4

RESULTS AND PERFORMANCE ANALYSIS

40

start

Check the ldr states

IF LDR1=0&LDR2=1

IF LDR1=1&LDR2=0

TRACKINGTOWARDS(0-90)

MOTOR ROTATES

TRACKINGTOWARDS(0-90)

MOTOR ROTATES

TRACKINGTOWARDS(0-90)

MOTOR ROTATES

DISPLAYING THE STATES ON PC

4.1 Advantages

Simple

Low cost

Eco-Friendly

We can monitor directly using PC

Tracking accuracy is more

Reduce the usage of power from power grid

4.2 Applications

Day lighting:

The oldest solar application is day lighting, the use of windows and other means

allowing indirect sunlight to provide effective internal illumination inside buildings.

Thermal Applications:

Solar thermal, when used for space heating is needed mostly in the winter in cold

and temperate climates.

For process heat, which includes solar domestic hot water, as well as heat for

industrial processes, the active solar thermal systems shine because year round usage

can make these still relatively inexpensive systems easily economic. 

Solar parabolic trough systems are also sometimes used in large scale, high

temperature industrial applications

4.3 Result

41

Fig: 4.1 Implementation of Intelligent solar tracking system.

The result of our implementation is, power supply is given to 40-pin micro

controller, since micro controller having 40 pins. In that input and output pins are 32. LDR

outputs are given to the interrupt pins a as, mentioned above in the topics. 12 and 13 are the

42

interrupt pins and port 2 is given to ULN driver. It is maximizing the power because for the

rotation of the stepper motor. The stepper motor operates at 12v. As mentioned stepper

motor operates at 12v. Since, stepper motor having 6 windings, in that 4 windings are given

to the ULN driver and the remaining (2) rest of windings are given to the solar panel. LDR

positive are given to the solar panel positive. LDR negative to the micro controller. The

power supply given to the micro controller is 5v. Totally we use 4 LEDs. All this 4 LEDs

will glow in 16 combinations with the control of the PC. Here, LDRs are used as sensors.

Which sensor gets maximum intensity that correspondence interrupts becomes zero.

According to the program it rotates the stepper motor. Then, the panel absorbs the maximum

power. This power is stored in battery. This power can be utilized in various applications.

CHAPTER 5

43

SUMMARY AND CONCLUSION

5.1 Summary

The present invention resides in a solar tracking system having, a first set of solar

heat gain transducers that produce respective first output signals to drive a reversible first

motor for changing a vertical angle of a solar collector, and a second set of solar heat gain

transducers that produce respective second output signals to drive a reversible second motor

for changing a horizontal angle of the solar collector. Advantageously, the solar tracking

system is self-powered, by generating all of its power requirements to compensate for

changes in sun position, and to move the solar collector in a sun tracking mode. Further, the

solar tracking system has a solar collector with solar cells supplying output voltage to a

communications apparatus having input voltage requirements.

A further advantage of the present invention is that the solar heat gain transducers are

unaffected by ambient light conditions caused by artificial lights or lightning flashes.

Further, the transducers operate under a wide range of ambient temperatures, and they

operate to zero sum rapid changes in ambient temperature. Further, the solar tracking system

compensates for any location relative to the sun's directional rays.

According to an embodiment of the invention, each of the solar heat gain transducers

is a thermistor in thermal contact with a solar heated thermal mass.

According to a further embodiment of the invention, each of the first motor and

second motor are controlled by a reversible motor control circuit. Each said motor control

circuit has a corresponding set of thermistors supplying their output signals to a summing

amplifier and an inverter, respectively. The inverter output is supplied to the summing

amplifier. The amplifier output signal drives a corresponding first motor or second motor.

Other embodiments and modifications thereof are apparent by way of example with

reference to the following detailed description taken in conjunction with the accompanying

drawings.

44

5.2 Conclusion

A solar tracking system, comprising: a first set of solar heat gain transducers that

produce respective first electrical output signals to drive a reversible first motor for changing

a vertical angle of a solar collector; a second set of solar heat gain transducers that produce

respective second electrical output signals to drive a reversible second motor for changing a

horizontal angle of the solar collector; each of the transducers having a thermistor in thermal

contact with a thermal mass, wherein the thermal mass comprises a mass of conducting

material to elevate in temperature while illuminated by the sun, and wherein the thermistor

senses the temperature of the thermal mass and produces a corresponding one of the

electrical output signals proportional to the temperature; and each of the transducers having

the thermistor and the thermal mass contained in a solar energy collecting and heat

insulating enclosure that is solar energy transparent.

5.3 Future Expansion

By using real time clock we can adjust the panel directions according to the sun angle

without using sensors.

REFERENCES

The 8052 Micro Controller

Author-Kenneth Ayyala

45

The Micro Controller Idea Book

Author-Jan Axelson

Optimizing solar tracking system for solar cells

Zoltan KVasznicza

University of pecs

Boszokany v,2-h.7624 pecs, Hungary.

Automation of minimum torque- Based accurate solar tracking systems using micro

processors.

Anand M.Sharma & Manish Prateek

Memorial university of New Foundland,

Canada.

46