by T.SELVALAKSHMI, FINAL YEAR ECE DR.G.U.POPE COLLEGE OF ENGINEERING, SAWYARPURAM

1. Arduino Solar Tracker Using LDR
Sensor & Servo Motor
A PROJECT REPORT
Submitted by
T.SELVALAKSHMI
A comprehensive project report has been submitted in partial fulfillment
of the requirements for the degree of
Bachelor of Technology
In
ELECTRONICS & COMMUNICATION
ENGINEERING
DR.G.U.POPE COLLEGE OF ENGINEERING,
SAWYARPURAM

2. ABSTRACT
The aim ofthis projectis to consumethe maximum solar energy through solar panel.
A Solar Tracker is a device onto which solar panels are built-in which tracks the
motion of the sun ensuring that maximum amount of sunlight strikes the panels all
over the day. Power output from a solar cell will be maximum when it is facing the
sun i.e. the angle between its surfaceand sun rays is 90 degree. Solar tracking allows
more energy to be produced becausethe solar array is able to remain aligned to the
sun. The components used for its construction are servo motor, Arduino and LDR.
The active sensors continuouslymonitor the sunlight and alternate the panel towards
the direction where the intensity of sunlight is maximum. In this project, it’s divided
by two categories; hardware and software. In hardware part, 2 light dependent
resistor (LDR) has been used to trace the synchronize of sunlight by detecting
brightness level of sunlight. For rotation part, one standard servo motor has been
selected. In software part, the codeis constructed in C programming and inserted in
Arduino. This project is designed for low power and portable application.
Therefore, it’s suitable for rural area usage. Moreover, the effectiveness of output
power which collected by sunlight are increased.

3. CONTENTS
CERTIFICATE……………………………………………………………………1
DECLARATION.................................................................................................... 3
CERTIFICATEOF APPROVAL…………………………………………………4
ABSTRACT ………………………………………………………………........... 5
CONTENTS…….................................................................................................... 6
INTRODUCTION………………………………………………………………..10
1. RELATED WORK…………………………………………………….
1.1 Technology of Solar Panel …………………………………………………
1.2 Microcontroller Based Automatic Solar Tracker ………………………………
1.3 Evolution of Solar Tracker……………………………………………………
REQURED COMPONENTS………………………………………………………..
1. HAEDWARE REQUREMENT………………………………………………
2. SOFTWAREREQUREMENT……………………………………………….
BLOCK DIAGRAM………………………………………………………….

4. CIRCUIT DIAGRAM………………………………………………………….
WORKING…………………………………………………………………….
CODING……………………………………………………………………….
1. Coding Explanation…………………………………………………….
2. Calibration………………………………………………………………
Description of Components………………………………………………………
1. Arduino Nano……………………………………………………………..
2. H-Bridge Motor Driver…………………………………………………….
3. Light Dependent Resistor (LDR) ……………………………………….
4. Resistor…………………………………………………………………..
5. Servo Motor……………………………………………………………
6. ALUMINIUM WIRES …………………………………………………
7. PCB……………………………………………………………….
8. Battery……………………………………………………………..
9. Software………………………………………………………………….
ADVANTAGES………………………………………………
PROBLEMS ………………………………………………
RESULT AND DISCUSSION …………………………………………………..
APPLICATIONS………………………………………………
CONCLUSION ………………………………………………

5. INTRODUCTION
Renewable energy is energy which originates from natural sourcesuch as sunlight,
tides, wind rain, wave and etc. Solar Energy is the energy consequent from the sun
through the form ofsolar radiation. Solar energy is a very large, inexhaustible source
of energy. Today solar energy is the major eco-friendly & pollution less method of
producing the electricity. The power from the sun interrupted by the earth is
approximately 1.8*1011MW, which is many thousands of times larger than the
current consumption rate on the earth of all commercial energy sources. The main
objective of this paper is to improve solar tracker. Solar Tracker is a Device which
follows the movement of the sun as it rotates from the east to the west each day.
Using solar trackers upturns the amount of solar energy which is received by the
solar energy collector and develops the energy output of the heat/electricity which
is generated. The solar tracker can be used for more than a few applications such as
solar daylighting system, solar cells and solar thermal arrays. The commercial
persistence of solar tracker is rise solar panel output, maximum efficiency of the
panel, able to grap the energy throughout the day.
At the present time, clean renewable energy sources attract a great attention as an
essential mean for solving the energy crisis around the globe. Solar energy is

6. frequently offered free of charge all over the world although it is not a continuous
energy source. One of the most promising renewable energy sources characterized
bya huge potential ofconversion into electrical poweris the solar energy. The green
energy, also called renewable energy, has gained much attention now a day. Some
renewable energy types are solar energy, hydro potential energy, terrestrial heat,
wind energy, biomass energy, sea waves, temperature difference of sea, morning
and evening tides, etc. Among these, solar energy is one ofthe mostuseful resources
that can be used. However, so far the efficiency of generating electric energy from
solar radiation is relatively low.
The main objective of this paper is to improve solar tracker. The solar tracker can
be used for several applications; these are solar cells, solar thermal arrays and solar
day-lighting system. Nowadays, the highest efficiency of solar panel is 19%. So, the
efficiency can be enhancing by using solar tracker. Albeit, the price of various solar
tracker are still costly becausesolar tracker is still fresh and only a few countries use
it as South Korean and USA. Furthermore, this project is considered for rural area
which extreme from main supply and absolutely low cost.
1.RELATED WORK
The following is a brief description of the papers that were studied to understand
about solar tracker.
1.1 Technology of Solar Panel
Solar panels are defined as to convert light into electricity. They are called solar
after the sun because the sun is the best powerful source of the light obtainable for
use. They are sometimes called photovoltaic which means "light electricity". Solar
cells or PV cells depend on the photovoltaic effect to absorb the energy of the sun.
Each solar cell provides a comparatively small amount of power, a lot of solar cells

7. spread overa large area can provide enough power to be useful. To develop the most
power, solar panels have to be pointed directly next to the Sun. A solar panel is a
collection ofsolar cells. The development ofsolar cell technology begins with 1839
examination of French physicist Antoine-Cesar Becquerel and he observed the
photovoltaic effect while experimenting with a compactelectrode in an electrolyte
solution. Subsequently he saw a voltage developed when light fell upon the
electrode.
According to Encyclopedia Britannica the first honest for solar panel was built
around 1883 by Charles Frits. He used connections formed by coating selenium (a
semiconductor)with an extremely thin layer of gold. Crystalline silicon and gallium
arsenide are usual varieties of materials for solar panels. Gallium arsenide crystals
are grown especially for photovoltaic use, but silicon crystals are obtainable in less
expensive standard ingots, which are produced mostly for intake in the
microelectronics industry. Norway’s Renewable Energy Corporation has confirmed
that it will constructa solar developed plant in Singapore by 2010 - the largest in the
world. This plant will be able to produce products that can create up to 1.5 G w of
energy every year. That is enough to power several million households at any one
time. Last year the world as whole formed products that could generate just 2 GW
in total.
1.2 Microcontroller Based Automatic Solar Tracker
F. Huang et al. had aimed a microcontroller based automatic sun tracker combined
with a new solar energy conversion unit in 1998 .The automatic sun tracker was
implemented with a dc motor and a dc motor controller. The solar energy
transformation unit involved ofan array of solar panels, a step-up chopper, asingle-
phase inverter, an ac mains power source and a microcontroller based control unit.

8. High efficiency was achieved through the automatic sun tracker and the MPP
detector. In this system, the MPP finding and the power conversion were realized by
using the same hardware circuit. In the existed MPP detectors, the detection of the
MPP was achieved by using analog computing, comparing, and holding. In compare
to the existed ones, in the fresh system, the MPP was detected by software which
was embedded in a microcontroller [F. Huang et al., 1998].
1.3 Evolution of Solar Tracker
Since the sun transfers across the sky through the day, in order to receive the best
angle of exposure to sunlight for collection energy. A tracking mechanism is
frequently incorporated into the solar arrays to keep the array pointed in the direction
of the sun. A solar tracker is a device onto which solar panels are fixed which tracks
the motion of the sun across the sky ensuring that the extreme amount of sunlight
strikes the panels throughout the day. When relate to the price of the PV solar panels,
the cost of a solar tracker is comparatively low. Most photovoltaic solar panels are
fitted in a secure location- for example on the inclined roof of a house, or on
framework fixed to the ground. Since the sun moves across the sky and yet the day,
this is far from an ideal solution. Solar panels are usually set up to be in full direct
sunshine at the medium of the day in front of South in the Northern Hemisphere, or
North in the Southern Hemisphere. Consequently morning and evening sunlight
triumphs the panels at an acute angle decreasing the total amount ofelectricity which
can be generated each day.
REQURED COMPONENTS
In this project divided by two categories;
1. Hardware

9. 2. Software
1.HAEDWARE REQUREMENT
 Arduino Nano
 LDR
 Resistor
 9V Battery
 PCB
 Servo Motor
 H-Bridge Motor Driver
 ALUMINIUM WIRES
2.SOFTWAREREQUREMENT
 Arduino.cc Software
BLOCK DIAGRAM

10. CIRCUIT DIAGRAM
In the circuit two LDR (Light Dependent Resistors) sensors are used to sense the
light. Since LDR is an analogue sensorthey are connected to the analog pins A0 and
A1 of Arduino. The sensors are connected in series with 10 k ohm resistors.
A servomotor is also connected to the digital pin D10. D10 is a PWM (pulse width
modulation) pin. A momentary switch is also connected to digital pin D2, mainly for
calibration purposes. When the switch is pressed D2 pin will act as the ground
(GND). A 12-volt adapter or 9 volt battery, can be used to power this whole circuit.
RAW pin in Arduino Nano is the power pin.
WORKING
In this project an Arduino Nano is used, which works as a controlling unit. Two
LDR’s (Light Dependent Resistor)are also connected to analog pins ofthe Arduino.

11. A dummy solar plate is attached in parallel to the axis of servo motor and both the
sensors are kept on the dummy solar plate as shown in the figure below.
The arrangement is made in such a way that the movement of sun is from sensor 1
to sensor 2, as shown in the mage below.
LDR Sensor Movement

12. There are three conditions to be followed:-
Condition 1:
Sun is in left side– Light on sensor1is high becauseshadowofbarrier falls on sensor
2 so solar plate moves clockwise.
Condition 2:
Sun is in right Side – Light on sensor2 is high because shadow of barrier falls on
sensor1 so solar plate movie anticlockwise.
Condition 3:
Sun is in the middle – Light on both sensors are equal so, plate will not rotate in any
direction.
Output is shown in the demo video below. You can see that the plate moves in the
direction of light, but some fluctuation is visible in video because light is coming
from multiple sources. Fluctuation is automatically removed when system is placed
in direct sunlight.
Circuit Design
In this projects include design and construction of an Arduino based solar tracker.
This solar tracker system uses the Arduino board, a servomotor, 2 LDR and 2
resistors to rotate the solar panel towards the sun or a source of light. In this project
LDR was selected since it has no polarity, and easy to interface with circuit, cheap,
reliable and is described by high spectral sensitivity, so that difference in high

13. intensity is represented immediately by change in its resistance value. The block
diagram of proposed system as shown in figure 1.
Fig -1: Block Diagram of Project
In constructing the solar tracking system, LDRs are used to determine solar light
intensity. The 2 LDRs are connected to pin A0 and A1 on the board. One servo
motor is used for rotation part. Usually the servo has a yellow wire that is used to
control the cycle and it must be associated on pin 9 on the board. When light falls
on the LDR, its resistance differs and a potential divider circuit is used to obtain
correspondingvoltage value from the resistance of LDR. The voltage signal is send
to the microcontroller. Constructed on the voltage signal, a corresponding PWM
signal is send to the servo motor which origins it to rotate and finally attains a
position where intensity oflight falls on the solar panel is maximum. The schematic
diagram of proposed system as shown in figure 2.

14. Fig -2: Schematic Diagram of Project
In this project the angles are designed by finding which LDR is in shadow. For
example if high source is right with respect to right LDR will receive maximum
light and left LDR will be in shadow. The major components of this system are as
follows, Light dependent resistor, Arduino board, Servo motor, 10 k resistor.
CODING
#include <Servo.h>
//Servo Tanımları
Servo myServoEW;
Servo myServoNS;
//Değişken Tanımları

15. int farkNS;
int farkEW;
//Servo Motor Derece Değişkenleri
int degNS;
int degEW;
//LDRlerin ışık değerleri
int ldrN;
int ldrW;
int ldrS;
int ldrE;
void setup() {
// put your setup code here, to run once:
Serial.begin(115200);
//Servo motorları bağla

16. myServoNS.attach(5);
myServoEW.attach(4);
delay(500);
//Başlangıç pozisyonu al
degNS=90;
degEW=90;
myServoNS.write(degNS);
myServoEW.write(degEW);
}
void loop()
{
//LDR leri oku
ldrN=analogRead(A0);
ldrW=analogRead(A1);

17. ldrS=analogRead(A2);
ldrE=analogRead(A3);
//Bildirim yap
Serial.print("ldrN:");
Serial.print(ldrN);
Serial.print(" ldrW:");
Serial.print(ldrW);
Serial.print(" ldrS:");
Serial.print(ldrS);
Serial.print(" ldrE:");
Serial.print(ldrE);
//Bulunan açı değerlerini yazdır
Serial.print(" degEW");
Serial.print(degEW);

18. Serial.print(" degNS");
Serial.println(degNS);
delay(100);
/* Ldrlerin ışıkdeğerlerini karşılaştırarakyeniden pozisyon almak için karşılaştırma
yap*/
if (ldrN>ldrS) //ldrN değeri ldrS değerinden büyükse
{
farkNS=ldrN-ldrS;
if (farkNS>5)
{
degNS++;
myServoNS.write(degNS);
}
}

19. if (ldrS>ldrN) //ldrN değeri ldrS değerinden büyükse
{
farkNS=ldrS-ldrN;
if (farkNS>5)
{
degNS--;
myServoNS.write(degNS);
}
}
/* Ldrlerin ışık değerlerini karşılaştırarak yeniden pozisyon almak için
karşılaştırma yap*/
if (ldrW>ldrE) //ldrW değeri ldrE değerinden büyükse
{
farkEW=ldrW-ldrE;

20. if (farkEW>5)
{
degEW++;
myServoEW.write(degEW);
}
}
if (ldrE>ldrW) //ldrE değeri ldrW değerinden büyükse
{
farkEW=ldrE-ldrW;
if (farkEW>5)
{
degEW--;
myServoEW.write(degEW);
}

21. }
}
1.CODING EXPLANATON
We are using EEPROM and Servo Motor so two header files “EEPROM.h” and
“Servo.h”are used in the starting ofcode. Next a servo motor is defined by the name
“myservo”. Two integers are defined by names sensor1 and sensor2. Calibration
switch is connected to D2 pin so another integer is defined by “Cal switch”. Other
integers are defined by names val1, val2, pos, & error. All these states are used for
internal processes.
In the void setup sensor1, sensor2and Cal switch are defined as input. Now servo is
activated by “myservo.attach (10)” function.
In the void loop section first of all an “if” condition is used for calibration. When
momentary switch is pressed this “if” condition becomes true. In this condition servo
the motor is deactivated by function “myservo.detach (10)”. Next values of sensors
are assigned in integer “val1” and “val2”. According to the value of val1, val2 &
error, the state is saved in EEPROMusing function “EEPROM.write ()”, and a delay
of 1 second is used at the end of this loop. Now calibration process is done.
In else loop “myservo.attach” is used to activate the servo, val1 and val2 are read by
using “analogRead” function, after that state and error is read from EEPROM using
“EEPROM.read” function after that error is removed from val1 or val2.

22. Three conditions are described in working of project, these conditions are executed
in the code using “if else” conditions, in this way servo rotates clockwise or
anticlockwise according to sunlight.
The rotational movement of the solar panel should not should be confined between
o and 90 degrees. When “pos”becomes more then 90 degree an if condition is used
for making this 90 degree and same concept is used when it becomes less than 0
degree.
2.Calibration
This project is featured by self-calibration so it does not need any preset or variable
resistor for calibration; you just need to press a momentary switch. For calibration,
press and hold the switch, which is connected to pin D2 and rotate the solar plate in
direction ofsun and release after 2- 3 seconds. Byusing this simple process,Arduino
reads the value of sensors and saves the error state in EEPROM. This system needs
one time calibration.
Description of components
1. Arduino Nano Board
Arduino Nano is one type ofmicrocontroller board, and it is designed byArduino.cc.
It can be built with a microcontroller like Atmega328. This microcontroller is also
used in Arduino UNO. It is a small size board and also flexible with a wide variety
of applications. Other Arduino boards mainly include Arduino Mega, Arduino Pro
Mini, Arduino UNO, Arduino YUN, Arduino Lily pad, Arduino Leonardo, and
Arduino Due. And other development boards are AVR Development Board, PIC

23. Development Board, Raspberry Pi, Intel Edison, MSP430 Launchpad, and ESP32
board.
Arduino Nano 3.0 MCU Development Board A000005
This board has many functions and features like an Arduino Duemilanove board.
However, this Nano board is different in packaging. It doesn’thave any DC jack so
that the power supply can be given using a small USB port otherwise straightly
connected to the pins like VCC & GND. This board can be supplied with 6 to 20volts
using a mini USB port on the board.
1.1. Arduino Nano Features
The features of an Arduino Nano mainly include the following.
 ATmega328P Microcontroller is from 8-bit AVR family
 Operating voltage is 5V

24.  Input voltage (Vin) is 7V to 12V
 Input/output Pins are 22
 Analog I/p pins are 6 from A0 to A5
 Digital pins are 14
 Power consumption is 19 mA
 I/O pins DC Current is 40 mA
 Flash memory is 32 KB
 SRAM is 2 KB
 EEPROM is 1 KB
 CLK speed is 16 MHz
 Weight-7g
 Size of the printed circuit board is 18 X 45mm
 Supports three communications like SPI, IIC, & USART
1.2. Arduino Nano Pinout
Arduino Nano pin configuration is shown below and each pin functionality is
discussed below.

25. Power Pin (Vin, 3.3V, 5V, GND): These pins are power pins
 Vin is the input voltage of the board, and it is used when an external power
source is used from 7V to 12V.
 5V is the regulated power supply voltage of the Nano board and it is used to give
the supply to the board as well as components.
 3.3V is the minimum voltage which is generated from the voltage regulator on
the board.
 GND is the ground pin of the board
RST Pin( Reset): This pin is used to reset the microcontroller
Analog Pins (A0-A7): These pins are used to calculate the analog voltage of the
board within the range of 0V to 5V
I/O Pins (Digital Pins from D0 – D13):These pins are used as an i/p otherwise o/p
pins. 0V & 5V
Serial Pins (Tx, Rx): These pins are used to transmit & receive TTL serial data.
External Interrupts (2, 3): These pins are used to activate an interrupt.
PWM (3, 5, 6, 9, 11): These pins are used to provide 8-bit of PWM output.

26. SPI (10, 11, 12, & 13): These pins are used for supporting SPI communication.
Inbuilt LED (13): This pin is used to activate the LED.
IIC (A4, A5): These pins are used for supporting TWI communication.
AREF: This pin is used to give reference voltage to the input voltage
1.3. Difference between Arduino UNO and Arduino Nano
The Arduino Nano board is similar to an Arduino UNO board including similar
microcontroller like Atmega328p. Thus they can share a similar program. The main
difference between these two is the size. Because Arduino Uno size is double to
Nano board. So Uno boards use more space on the system. The programming of
UNO can be done with a USB cable whereas Nano uses the mini USB cable.
1.4. Arduino Nano Communication
The communication of an Arduino Nano board can be done using different sources
like using an additional Arduino board, a computer, otherwise using
microcontrollers. The microcontroller using in Nano board (ATmega328)
offers serial communication (UART TTL). This can be accessible at digital pins like
TX, and RX. The Arduino software comprises of a serial monitor to allow easy
textual information to transmit and receive from the board.
The TX & RX LEDs on the Nano board will blink whenever information is being
sent out through the FTDI & USB link in the direction of the computer. The library-
like Software Serial allows serial communication on any of the digital pins on the
board. The microcontroller also supports SPI & I2C (TWI) communication.
1.5. Arduino Nano Programming
The programming of an Arduino Nano can be done using the Arduino software.
Click the Tools optionand select the Nano board. Microcontroller ATmega328 over

27. the Nano board comes with preprogrammed with a bootloader. This bootloader lets
to upload new code without using an exterior hardware programmer. The
communication of this can be done with the STK500 protocol. Here the bootloader
can also be avoided & the microcontroller program can be done using the header of
in-circuit serial programming or ICSP with an Arduino ISP.
1.6. Applications of Arduino Nano
These boards are used to build Arduino Nano projects by reading inputs of a sensor,
a button, or a finger and gives an output by turning motor or LED ON, or and some
of the applications are listed below.
 Samples of electronic systems & products
 Automation
 Several DIY projects
 Control Systems
 Embedded Systems
 Robotics
 Instrumentation
Thus, this is all about an overview of Arduino Nano datasheet. From the above
information finally, we can conclude that for the beginners who are new to
electronics, this Nano board is extremely suggested to go for this board due to its
features like low cost and very simple to use in different applications. This board
can simply connect to any computer throughout its mini USB port.
2.H-Bridge Motor Driver
An H bridge is an electronic circuit that switches the polarity of a voltage applied to
a load. These circuits are often used in robotics and other applications to allow DC

28. motors to run forwards orbackwards. Most DC-to-AC converters (power inverters),
mostAC/AC converters, the DC-to-DC push–pullconverter, mostmotorcontrollers,
and many other kinds of power electronics use H bridges. In particular, a bipolar
stepper motor is almost invariably driven by a motor controller containing Two H
Bridges.
2.1. Relays
One way to build an H bridge is to use an array of relays from a relay board. A
"double pole double throw" (DPDT) relay can generally achieve the same electrical
functionality as an H bridge (considering the usual function of the device). However
a semiconductor-based H bridge would be preferable to the relay where a smaller
physical size, high speed switching, or low driving voltage (or low driving power)
is needed, or where the wearing out of mechanical parts is undesirable.
Another option is to have a DPDT relay to set the direction of current flow and a
transistor to enable the current flow. This can extend the relay life, as the relay will
be switched while the transistor is off and thereby there is no current flow. It also
enables the use of PWM switching to control the current level.
2.2. N and P channel semiconductors
H Bridge with N channel MOSFET's

29. A solid-state H bridge is typically constructed using opposite polarity devices, such
as PNP bipolar junction transistors (BJT) or P-channel MOSFETs connected to the
high voltage bus and NPN BJTs or N-channel MOSFETs connected to the low
voltage bus.
2.3. N channel-only semiconductors
The mostefficient MOSFET designs use N-channel MOSFETs onboththe high side
and low side because they typically have a third of the ON resistance of P-channel
MOSFETs. This requires a more complex design since the gates of the high side
MOSFETs must be driven positive with respect to the DC supply rail. Many
integrated circuit MOSFET gate drivers include a charge pump within the device to
achieve this.
Alternatively, a switched-mode power supply DC–DC converter can be used to
provide isolated ('floating') supplies to the gate drive circuitry. A multiple-output fly
back converter is well-suited to this application.
Another method for driving MOSFET-bridges is the use ofa specialized transformer
known as a GDT (gate drive transformer), which gives the isolated outputs for
driving the upper FETs gates. The transformer core is usually a ferrite toroid, with
1:1 or4:9 winding ratio. However, this method canonly be used with high frequency
signals. The design of the transformer is also very important, as the leakage
inductance should be minimized, or cross conductionmay occur. The outputs of the
transformer are usually clamped by Zener diodes, becausehigh voltage spikes could
destroy the MOSFET gates.
2.4. Variants
A common variation of this circuit uses just the two transistors on one side of the
load, similar to a class AB amplifier. Such a configuration is called a "half

30. bridge". The half bridge is used in some switched-mode power supplies that
use synchronous rectifiers and in switching amplifiers. The half-H bridge type is
commonly abbreviated to "Half-H" to distinguish it from full ("Full-H") H bridges.
Another common variation, adding a third 'leg' to the bridge, creates a three-phase
inverter. The three-phase inverter is the core of any AC motor drive.
A further variation is the half-controlled bridge, where the low-side switching device
on one side of the bridge, and the high-side switching device on the oppositeside of
the bridge, are each replaced with diodes. This eliminates the shoot-through failure
mode, and is commonly used to drive variable or switched reluctance machines and
actuators where bi-directional current flow is not required.
2.5. Commercial availability
There are many commercially available inexpensive single and dual H-bridge
packages, of which the L293x series includes the most commonones. Fewpackages,
like L9110, have built-in fly back diodes for back EMF protection.
2.6. Operation as an inverter
A commonuse of the H Bridge is an inverter. The arrangement is sometimes known
as a single-phase bridge inverter.
The H Bridge with a DC supply will generate a square wave voltage waveform
across the load. For a purely inductive load, the current waveform would be a
triangle wave, with its peak depending on the inductance, switching frequency, and
input voltage.
2.7. H-Bridge Working Principle

31. An H-bridge is built of four switches that controlthe flow of current to a load. In the
image above, the load is the M connecting the two sets ofswitches. Using onecurrent
source, you can drive current in two directions by closing two switches.
If Switch 1 and 4 are closed, then the current will flow from the left to right on this
image:
The H-bridge configured to have switch 1 and switch 4 closed.
If you close switch 1 and switch 4, the current will flow from the source, through
switch 1, and then through the load, then through switch 4, and then backto the load.

32. An H-bridge circuit with S2 and S3 closed.
In the image above, the circuit has Switch 2 and switch 3 closed. This will causethe
current to flow from the source, through switch 3, and then through the load, then
through switch 2, then back to the load.
One thing you have to be very cautious about when working with H-bridges is to
not create a short circuit. If you create a short circuit, that’s a sure way to burn out
your H-bridge. I may have burned out my very first H-bridge at Digi lent.
1.8. Motor Driver Circuit

33. 3.Light Dependent Resistor (LDR)
An LDR orlight dependent resistor is also known as photo resistor, photocell, photo
conductor. It is a one type of resistor whose resistance varies depending on the
amount of light falling on its surface. When the light falls on the resistor, then the
resistance changes. These resistors are often used in many circuits where it is
required to sense the presence of light. These resistors have a variety of functions
and resistance. Forinstance, when the LDR is in darkness, then it can beused to turn
ON a light or to turn OFF a light when it is in the light. A typical light dependent
resistor has a resistance in the darkness of1MOhm, and in the brightness a resistance
of a couple of k Ohm.
3.1. Working Principle of LDR
This resistor works on the principle of photo conductivity. It is nothing but, when
the light falls on its surface, then the material conductivity reduces and also the

34. electrons in the valence band of the device are excited to the conductionband. These
photons in the incident light must have energy greater than the band gap of the
semiconductor material. This makes the electrons to jump from the valence band to
conduction.
Working Principle of LDR
These devices depend on the light, when light falls on the LDR then the resistance
decreases, and increases in the dark. When a LDR is kept in the dark place, its
resistance is high and, when the LDR is kept in the light its resistance will decrease.

35. Variation of LDR Resistance with Variation in Light Intensity
If a constant“V’ is applied to the LDR, the intensity ofthe light increased and current
increases. The figure below shows the curve between resistance Vs illumination
curve for a particular light dependent resistor.

36. Light Intensity vs LDR Resistance
3.2. Types of light Dependent Resistors
Light dependent resistors are classified based on the materials used.
3.2.1. Intrinsic Photo Resistors
These resistors are pure semiconductordevices like silicon or germanium. When the
light falls on the LDR, then the electrons get excited from the valence band to the
conduction band and number of charge carriers increases.
3.2.2. Extrinsic Photo Resistors
These devices are doped with impurities and these impurities creates a new energy
bands above the valence band. These bands are filled with electrons. Hence this

37. decreasethe band gap and small amount ofenergy is required in moving them. These
resistors are mainly used for long wavelengths.
3.3. Circuit Diagram of a Light Dependent Resistor
3.3.1. LDR Pin Description
The Light Dependent Resistor (LDR) is just another special type of Resistor and
hence has no polarity. Meaning they can be connected in any direction. They are
breadboard friendly and can beeasily used on a perfboard also. The symbolfor LDR
is just as similar to Resistor but adds to inward arrows as shown above. The arrows
indicate the light signals.
3.3.2. LDR Features
 Can be used to sense Light
 Easy to use on Breadboard or Perf Board
 Easy to use with Microcontrollers or even with normal Digital/Analog IC
 Small, cheap and easily available
 Available in PG5 ,PG5-MP, PG12, PG12-MP, PG20 and PG20-MP series
3.3.3. Where to use a LDR
A photo resistor or LDR (Light Dependent Resistor), as the name suggests will
change it resistance based on the light around it. That is when the resistor is placed
in a dark room it will have a resistance of few Mega ohms and as we gradually
impose light over the sensorits resistance will start to decrease from Mega Ohms to
few Ohms.
This property helps the LDR to be used as a Light Sensor. It can detect the amount
of light falling on it and thus can predict days and nights. So if you are looking for a

38. sensorto sense light or to distinguish between days and nights then this sensoris the
cheap and modest solution for you.
3.3.4. How to use a LDR sensor
As said earlier a LDR is one of the different types of resistors, hence using it is very
easy. There are many ways and different circuit in which an LDR can be used. For
instance it can be used with Microcontroller Development platforms
like Arduino, PIC or even normal Analog IC’s like Op-amps. But, here we will use
a very simple circuit like a potential divider so that it can be adapted for most of the
projects.
A potential Divider is a circuit which has two resistors in series. A constant voltage
will be applied across the both the resistor and the output voltage will be measured
from the lower resistor. In our case, the lower resistor will be a LDR and the constant
voltage will be +5V. The set-up is shown below
A DC multi meter is used to monitor the voltage across the LDR. As the Lamp is
moved towards the resistor the resistance value of the LDR will decrease as a result

39. the voltage drop across it will decrease. The near you bring the Lamp the lower the
voltage will get and the farther you move away your Voltage value will increase.
The working simulation is shown below.
Now that we have understood how the LDR provides a variable voltage based on
Light, we can feed this voltage either to a Microcontroller and use ADC to convert
the Voltage to meaning full data or use a Op-amp as a Voltage comparator and
trigger an specific output like LED or Buzzer for a specific Voltage from the LDR.

40. 3.4. Applications
 Automatic Street Light
 Detect Day or Night
 Automatic Head Light Dimmer
 Position sensor
 Used along with LED as obstacle detector
 Automatic bedroom Lights
 Automatic Rear view mirror
4.RESISTOR
4.1. What is a Resistor?
The resistor is a component, designed to find the known values of resistance. The
resistors are also known as the passive components. The resistors are used for
reducing the current in the circuits. The basic symbol of the resistor is shown in the
below.
Basic Resistor
4.2. PROPERTIES OF RESISTOR

41.  The two main characteristics of a resistor are its resistance, R, in ohms
and its power rating, P, in Watts.
 The resistance, R, provides the required reduction in current or the
desired drop in voltage.
 The wattage rating indicates the amount ofpower the resistor can safely
dissipate as heat.
 The wattage rating is always more than the actual amount of power
dissipated by the resistor, as a safety factor.
4.3. Different Types of Resistors and its Applications
4.3.1. Types of Resistors
There are some different types of resistors in the electronic circuits. Depending upon
the manufacture and contraction the resistance has different properties. It makes the
difference in their applications. The resistors are available in different sizes and
shapes in the market. The different types of resistor are discussed in the following
section.
 Linear resistors.

42.  Non-linear resistors.
4.3.2. Linear Resistors
The resistorvalues are changed with the help ofthe temperature and applied voltages
are called linear resistors. If the resistance of the current value is directly
proportional to the applied voltage is called the linear resistance. The linear resistors
are two different types of resistor which are the following.
 Fixed resistors
 Variable resistor
4.3.3. Fixed Resistor
The name itself says that fixed resistor. So the values of the specific resistor cannot
change in the fixed resistor. There are different types of the resistor which are in the
following.
 Led arrangement
 Carbon composition
 Carbon Pile
 Carbon film
 Printed carbon resistor
 Thick and thin film
 Metal film
 Metal oxide film
 Wire wound
 Foil resistor
 Ammeter shunt

43.  Grid resistor
 Special verities
4.3.4. Carbon Composition Resistor
The carbon composition resistor is made from the mixer of granulated or graphite,
insulation filter and a resin binder. The actual resistance of the resistor is determined
by the ratio of the insulation material. The shape of the insulating binder is in the
shape of roads and there are two metal caps at both the end of the roads. At both
ends of the resistor it has two wire conductors foreasy to connectivity in the circuit
design. There are different colors which are printed on the resistor to find the value
of it and the road is covered with the plastic coat.
Carbon Composition Resistor
4.3.5. Applications
 The composition resistor is used in the high energy pulses.
 It has a relatively small size.
 High voltage power supplies
 Welding
 High power

44. 5. Servo Motor
Servo motor is a rotary actuator or linear actuator that allows for precise control
of angular or linear position, velocity and acceleration. It consists of a suitable
motor coupled to a sensor for position feedback. It also requires a relatively
sophisticated controller, often a dedicated module designed specifically for use
with servo motors. Servomotors are not a specific class motor although the term
servomotor is often used to refer to a motor suitable for use in a closed-loop
control system.
Figure: Servo Motor
5.1. Working Principle
3 pairs of IR is used in this project.2 pairs of IR is placed at the rail line in such
a distance that these IR pair can send signal to Arduino to open or close the gate
by servo motor. The third IR pair is placed under the gate .If there is any obstacle
this IR pair check and send signal to microcontroller to read it so that the gate

45. remain close. The gate becomeclose oropen by the rotation of servo motor. This
is the main operation principle of this project.
6.ALUMINIUM WIRES
The Al-steel conductors ACSR (Al Conductor Steel Reinforced) traditionally
applied in overhead lines are characterized by their permissible work temperature at
the level of 80◦C, which equals the existence of limits for the transmission capacity
of the electro energetic networks. A long-term excess of this temperature causes a
risk of irreversible degradation of the strength properties of the Al wires (EN AW
1370), which have both the conductive and carrying function in the lead.
7.PCB (Printed circuit board)
A PCB (Printed circuit board) is designed for this Solar Tracker Arduino. Using a
breadboard or Zero PCB are also other simpler options to create this solar tracker
circuit.

46. The circuit diagram shown below. This is useful for ZERO PCB or breadboard
circuit.
8.Battery
A 9V battery is required to supply the dc power to drive the Arduino Uno and other
components connected to the Arduino.

47. 9.Software
Arduino IDE is used to develop the prototype of the software. Arduino IDE is
available at the official website of Arduino. This is open source. So any one can
develop anything according to their choices.

48. Fig 11. Arduino IDE interface
RESULT AND DISCUSSION
Result of this project is, when light falls on the LDR, its resistance varies and a
potential divider circuit is used to obtain correspondingvoltage value (5v) from the
resistance of LDR. The voltage signal is send to the Arduino microcontroller.
Established on the voltage signal, a corresponding PWM signal is send to the servo
motor which causes it to rotate and to end with attains a position where intensity of
light falls on the solar panel is maximum.

49. CONCLUSIONS
An Arduino solar tracker was designed and constructed in the current work. LDR
light sensors were used to sense the intensity of the solar light occurrence on the
photo-voltaic cells panel. Conclusions of this project is summarized as ,The existing
tracking system successfully sketched the light sourceeven it is a small torch light,
in a dark room, or it is the sun light rays. The Arduino solar tracker with servo motor
is employed by means of Arduino ATmega328p microcontroller. The essential
software is developed via Arduino Uno. The costand reliability of this solar tracker
creates it suitable for the rural usage. The purpose of renewable energy from this
paper offered new and advanced idea to help the people.