SOLAR PV CONTROL SYSTEM.pdf

Solar PV Control System using an 

Arduino and Zigbee Communication 

Module for Street Light, Household & 

Off-Grid Applications 

FACULTY OF ENGINEERING 

B.Sc. TELECOMMUNICATION & 

INFORMATION ENGINEERING 

DAVID IRUNGU 

(E020-0140/07) 

5 th Year Project Report 

Project Report Submitted To: 

The Department of Electrical, Electronic Engineering (EEE) in 

Partial Fulfilment for the Award of a Bachelors of Science 

Degree in Telecommunication & Information Engineering 

SUPERVISOR: MR. HARRISON T. NGETHA 

CO-SUPERVISOR: ISAAC WARUTUMO 

2012

Declaration 

I do hereby solemnly and sincerely declare to the best of my knowledge and belief 

that this document truly corresponds to entire activities I was involved in this 

project. I affirm that the work in this report has never been submitted for awarding 

of degree at Kimathi University College of Technology or any other higher 

institution of learning. 

I make this solemn declaration, conscientiously believing that statements contained 

in this entire proposal are true in every particular manner. 

Signed 

……………………………………. 

DAVID IRUNGU: E020-0140/07 

This project, which has been submitted by the above named student, was under my 

supervision. 

Supervisor Name: MR: T NGETHA 

Signature: Date: 

Email: david.irungu@stu.kuct.ac.ke 

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Acknowledgement 

I must acknowledge and express my sincere gratitude and deep appreciation to Mr 

Stephen Karekezi the Director AFREPREN (Africa Energy Policy Research Network) 

whose company’s training, hospitality, knowledge, and wisdom has supported and 

enlightened on the core foundation of this project over the short but prosperous 

attachment period. Mr. Karekezi is also the Executive Secretary of the Foundation 

for Woodstove Dissemination (FWD) in Nairobi and also was a member of the 

Scientific and Technical Advisory Panel (STAP, 1995-2002) of the Global 

Environment Facility (GEF), co-managed by the World Bank, UNDP and UNEP. 

I am genuinely thankful to Mr. Aschalew Demeke Tigabu who is a PhD student in the 

department of Environmental Economics of IVM Institute for Environmental Studies 

at the VU University Amsterdam (Netherlands). He was working on the Innovation 

Systems of Renewable Energy Technologies in East Africa, part of RENEW project 

funded by the DGIS (Dutch Ministry of Foreign Affairs). His research experiences 

and program concentration in Renewable Energy helped cultivate this project which 

can be adapted in rural households, metropolitan towns (street lighting) as well as 

in off grid system as a whole. I adapted the Renewable energy concept which is the 

backbone of this project. 

Also my sincere gratitude goes to my supervisor; Mr. Harrison T. Ngetha, my Co- 

supervisor Mr. Isaac Warutumo for coordinating and guiding to the development of 

this project; and not forgetting all the staff members i.e. Mr. Asaph Mbugua, Mr. 

Mathenge, Mr. Luke Otieno; among others of KIMATHI UNIVERSITY COLLEGE OF 

TECHNOLOGY (Dept. EEE) who have willingly, taken the time to support towards 

our project process while we worked patiently alongside with them in finalising this 

report. 

Lastly I thank my Family and Friends and give everything to God the almighty 

because He is the source of my inspiration to the above personalities that made 

them stand firm for me at all the times I consulted, inquired and asked for support. 


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Abstract 

Solar PV (photovoltaic) control System with Zigbee module is an Intelligent Energy 

Solar tracking System which can be used in places of high altitudes or receive less 

light intensity such as Nyeri. The solar panel will be well illuminated with a lamp to 

show clearly how the solar tracking takes place. Also the temperature, position and 

energy generated can be read and data sent through the Zigbee module to the 

control centre and stored in database format for analysis. The system can monitor 

solar PV generation and grid export. This allows the calculation of how much of 

power is generated and how much is exported to the grid. The data can be logged to 

a remote server and also shown in real-time on a display. All these can be done 

through by Arduino microcontroller and Xbee Modules. 

As the sun (light source) moves, the system automatically moves the panel by use of 

the light sensor and activates the Arduino to move the motors. The temperature 

readings will be read by the Arduino with the help of temperature sensor. Also the 

light sensor detects the light intensity of the monitored area and data sent by 

Arduino to the Zigbee module. In this case also the energy generated can be read by 

the Arduino from the storage batteries and data sent in the same Zigbee module. 

By using this system I can promote the dissemination of green energy which is 

readily available as renewable energy and also improve efficiency as well as 

provision of data read from different nodes of the system be available globally for 

research, analysis and system monitoring. 

To display the readings, I require a P.C. at the control centre for analysing the data 

taken and an LCD display at the actual plant (system). This would be enabled via 

data communication and synchronization of the whole system thus improving the 

control systems using advanced communication (Zigbee Protocol) and information 

technologies via programming to manage and monitor energy usage more 

intelligently. 

Intelligent control can allow energy systems to respond to their environment and 

make operating decisions based upon achieving specific energy goals. 


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Contents 

Declaration ............................................................................................................... 1 

Acknowledgement .................................................................................................... 2 

Abstract ..................................................................................................................... 3 

List of Tables ............................................................................................................. 5 

List of Figures ........................................................................................................... 5 

Abbreviations ........................................................................................................... 6 

CHAPTER 1 ................................................................................................................ 8 

Introduction ....................................................................................................................8 

Statement of Problem .....................................................................................................8 

Justification .....................................................................................................................9 

The Innovation ................................................................................................................9 

Up-to-date scholarly knowledge ....................................................................................9 

Objectives ...................................................................................................................... 10 

CHAPTER 2 .............................................................................................................. 12 

LITERATURE REVIEW ................................................................................................... 12 

A. TRACKING CONTROL: MPPT (Max Peak Power Tracker) .................................... 13 

B. CHARGER CONTROL ............................................................................................... 27 

C. Street Light Review ................................................................................................ 28 

D. COMMUNICATION ............................................................................................... 32 

CHAPTER 3 .............................................................................................................. 52 

Methodology of Implementation ................................................................................. 52 

Operation of the Tracking System: .............................................................................. 52 

Block Diagram of Improved solar tracking system (STS) .......................................... 54 

Arduino as a Charger Controller .................................................................................. 55 

Street Light Implementation ........................................................................................ 56 

Communication System Methodology ......................................................................... 57 

Results & Analysis ......................................................................................................... 59 

Conclusion: - Possible Errors ............................................................................................. 64 

References ..................................................................................................................... 65 

APPENDIX: ................................................................................................................ 66 

Plan of Action ................................................................................................................ 66 

GANTT CHART ............................................................................................................... 66 

LM35 DATASHEET ........................................................................................................ 67 

COMBINED SOURCE CODE ............................................................................................ 67 


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List of Tables 

Table 1: Specifications of street lighting system .......................................................... 29 

Table 2: Specification of IEEE 802.15.4 .......................................................................... 44 

Table 3: Zigbee Comparison ........................................................................................... 51 

Table 4: Plan of action ...................................................................................................... 66 

Table 5: Gantt chart ......................................................................................................... 66 

List of Figures 

Figure 1: Arduino Microcontroller Board......................................................................... 14 

Figure 2: A DC Motor....................................................................................................... 16 

Figure 3: A Dismantled Servo Motor ............................................................................... 18 

Figure 4: A servo motor’s positioning pulses ................................................................... 19 

Figure 5: Stepper motors ................................................................................................... 20 

Figure 6: A unipolar stepper motor coils .......................................................................... 21 

Figure 7: H-Bridge driving a unipolar motor .................................................................... 21 

Figure 8: LED used as light sensor for a Robot ............................................................. 24 

Figure 9: Variation of LDR resistance as a function of Incident Light (Picture shows 

an example of LDR) ......................................................................................................... 26 

Figure 10: Variation of temperature of the NTC as a function of temperature. (Thermistor 

Picture) .............................................................................................................................. 27 

Figure 11: Solar Security light at Kimathi University with one solar panel ..................... 29 

Figure 12: Stand-alone system of Solar lighting at Kimathi University. .......................... 31 

Figure 13: Wi-Fi Operation .............................................................................................. 36 

Figure 14: Piconet Configuration...................................................................................... 39 

Figure 15: IEEE 802.15.4 protocol stack .......................................................................... 46 

Figure 16: IEEE 802.15.4 star and peer-to-peer ............................................................... 47 

Figure 17: ZigBee Network Model ................................................................................... 48 

Figure 18: Xbee Modules (One to act as a Coordinator and the other as the Router) ...... 49 

Figure 19: Principle Structure of the X-Bee System ........................................................ 49 

Figure 20: Reference Pin out (Xbee) ................................................................................ 50 


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Figure 21: Block Diagram ................................................................................................ 54 

Figure 22: Signal Flow diagram ....................................................................................... 55 

Figure 23: LM35, LCD connections to Arduino .............................................................. 58 

Figure 24: X-CTU Software ............................................................................................. 58 

Figure 25: XBee Connection - Coordinator and Router ................................................... 59 

Figure 26: LDRs connection on solar plate ...................................................................... 60 

Figure 27: XBee readings on the control Terminal .......................................................... 61 

Figure 28: HyperTerminal ................................................................................................ 62 

Figure 29: XBee Database - Mozilla & Spread sheet formats .......................................... 62 

Figure 31: Lux-LDR readings in Spread sheet ................................................................. 63 

Figure 30: LDR ................................................................................................................. 63 

Figure 32: Lux Analysis for the system ............................................................................ 64 

Abbreviations 

AM – Active Mode 

AP – Access Point 

ATIM – Announcement Traffic Indication Message 

AFH – Adaptive Frequency Hopping 

ACL–Asynchronous Connectionless Link 

CPV – Concentrated PV 

CSP – Concentrated Solar Power 

CSMA/CA – Carrier Sense Multiple Access / Collision Avoidance 

CCA–Clear Channel Assessment 

DCF – Digitally Controlled Filter 

ED – Energy Detection 

EEE – Electrical & Electronic Engineering 

FFD- Full Function Device 

GPS – Global Positioning Satellite 

GFSK – Gaussian Frequency shifting Key 


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ISM – Industrial Scientific and Medical 

IEEE – Institute of Electrical and Electronic Engineers 

LDR – Light Dependent Resistor 

LED – Light Emitting Diode 

MAC – Medium Access Control 

MPPT – Maximum Peak Power Tracking 

OSI – Open System Interconnection 

PHY – Physical Layer 

PAN – Personal Area Network 

PWM – Pulse Width Modulation 

PDA – Personal Digital Assistance 

Wi-Fi – Wireless Fidelity 

WSN – Wireless Sensor Network 

WLAN – Wireless Local Area Network 


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CHAPTER 1 

Introduction 

The Solar PV (photovoltaic) control System with Zigbee module, aim of the project is 

to utilize the solar energy, monitor the energy generated and incorporate its usage 

in the grid system. In this project I shall be using various sensors, controlling and 

display. 

However, in this project work the basic signal processing of various 

parameters are temperature, lux readings, panel position, and energy produced 

which are the key elements for the grid implementation. For measuring various 

parameters values, various sensors are used and the outputs of these sensors are 

converted to control the parameters of the panel and data analysis. The control 

circuit is designed using micro-controller (Arduino). The outputs of all the three 

parameters are fed to micro-controller. The output of the micro-controller is used to 

drive the PV panel. 

I shall be developing new control systems using advanced communication and 

information technologies to manage and use energy more intelligently. Intelligent 

control can allow energy systems to respond to their environment and make 

operating decisions based upon achieving specific energy goals. 

Statement of Problem 

Solar P.V systems are widely used in the world. In high altitudes (like Nyeri), receive 

minimal sunlight thus resulting to underutilization of P.V capabilities. It’s also hard 

to monitor the usage of the energy stored and its use in a household or institution 

thus reducing its efficiency. 

Reliable electricity in Kenya is an oxymoron. Blackouts have been a norm in Kenya 

due to inconsistent supply of energy (electricity) and high demands. Due to this, 

solar power can be implemented in the grid system for constant supply and energy 

efficiency. It is also a cheaper way to produce energy as solar energy is renewable. 


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Justification 

While solar energy use in Arctic and Antarctic countries has been stagnating for 

years, use of solar energy in Kenya has exploded. Why? Because solar energy 

delivers cheap, reliable energy and Kenya is located on the equator. Solar energy 

devices are cheap to produce, easy to use and require little maintenance. It is only 

during the rainy season (mainly March to September) that there may not always be 

enough sunlight to operate solar devices. The penetration of the Grid System in 

Kenya is 15% i.e. 85% don’t have access to electricity. 

A 2007 World Bank report said Kenya has annual solar energy resources equivalent 

to the discovery of roughly 70 million tons of oil. About 30 000 solar photovoltaic 

(PV) systems are sold annually. The industry is thriving, making the country one of 

the best examples of where solar energy technology has taken off in sub-Saharan 

Africa. But further investment is required especially in manufacturing of PV panels. 

Access to regular supplies of electricity has increased in Kenya: 44% of the 

population now have access, versus 23% in 1970. However, many rural 

communities may never get access as this is very expensive and requires heavy 

government subsidies. Fewer than 2% of Kenyans in rural areas are served by the 

national grid. In such a situation, solar energy in Kenya can be of help. [1] 

The Innovation 

Replacing the charge controller with the Arduino 

Introducing the Zigbee communication module 

Introducing the dimmer circuit 

Introducing a temperature and lux reading circuit 

Up-to-date scholarly knowledge 

A solar tracker is a generic term used to describe devices that orient various 

payloads toward the sun. Payloads can be photovoltaic panels, reflectors, lenses or 

other optical devices. In flat-panel photovoltaic (PV) applications trackers are used 

to minimize the angle of incidence between the incoming light and a photovoltaic 


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panel. This increases the amount of energy produced from a fixed amount of 

installed power generating capacity. In standard photovoltaic applications, it is 

estimated that trackers are used in at least 85% of commercial installations greater 

than 1MW from 2009 to 2012. 

In concentrated photovoltaic (CPV) and concentrated solar thermal 

(CSP) applications trackers are used to enable the optical components in the CPV 

and CSP systems. The optics in concentrated solar applications accepts the direct 

component of sunlight light and therefore must be oriented appropriately to collect 

energy. Tracking systems are found in all concentrator applications because such 

systems do not produce energy unless oriented closely toward the sun. [2] 

The greatest modification of this project is the addition of the Zigbee 

Communication Technology and the addition of the Arduino micro-controller 

functions with respect to tracking ability. 

Objectives 

Main Objective 

Improving solar PV efficiency (Automation & Intelligence) 

Specific-Objectives 

Figure: Block Diagram showing a Typical Solar Harvesting System 

To come up with the control tracking system 


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To come up with digital charger control system 

To implement an efficient street lighting control system – dimmer circuit 

Realisation of the Zigbee module communication – Temp, Lumens & Energy 

By introducing intelligence into the ways that our energy is generated, transmitted 

and consumed we can also achieve higher level goals – such as making energy from 

renewable sources more reliable and cost-effective. 

By making renewable energy more reliable we hope to encourage their use in the 

marketplace. Technologies under development are aimed for use in the home, in 

commercial buildings and in the energy distribution system to both make energy 

use more efficient and increase Kenya’s use of renewable generation. 


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CHAPTER 2 

LITERATURE REVIEW 

Renewable energy is any energy produced using methods that are considered to 

have little or no impact on the earth’s ability to renew the supply. Otherwise 

referred to as sustainable energy, renewable energy includes solar photovoltaic 

(PV) panels and wind turbines which are both considered as having the ability to 

produce energy without negatively affecting the environment. Harnessing of the sun 

and wind cannot exhaust their supply and running solar panel systems are literally 

maintenance free. Solar power generally refers to electricity generated by 

photovoltaic (PV) solar panels that utilize materials displaying the photovoltaic 

effect. [3] 

Photovoltaic (PV) 

Photovoltaic PV Energy or PV for short is technology that uses semiconductors to 

convert sunlight into direct current (DC) electricity. Photovoltaics can provide tiny 

amounts of power for watches, large amounts for the electric grid, and everything in 

between. Groups of PV cells can be combined to make a module, and groups of 

modules are configured to become an array. 

Photovoltaic (PV) systems are used for powering telecommunications networks; 

applied in small scale remote stand-alone power supplies for domestic use, game 

farms and household and community water pumping schemes. The installed PV 

capacity is estimated at 12 MW (DME, 2003). Off-grid systems include a wide range 

of applications and sizes. The majority of off-grid systems are small solar home 

systems. [4] 

Solar Panels can either be fixed in place or designed to track the movement of the 

sun. The simplest PV array consists of flat plate PV panels in a fixed position. 

Most solar lights use a small panel to keep the lights operating throughout the hours 

of darkness. 


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The advantages of fixed arrays are that they lack moving parts, so there is 

virtually no need for extra equipment, and they are relatively lightweight. These 

features make them suitable for many locations, including most residential roofs. 

Because the panels are fixed in place, their orientation to the sun is usually at an 

angle that practically speaking is less than optimal. Therefore, less energy per unit 

area of array is collected compared with that from a tracking array. However, this 

drawback must be balanced against the higher cost of the tracking system. 

PV technologies: 

The solar module is a number of solar cells connected together and encapsulated to 

give an electrical output. For larger systems, the modules can be connected in series 

and parallel to form a solar array. 

Monocrystalline: Made from cells cut from single silicon crystals. The energy 

conversion rate efficiency is 16% (Ideal Case) 

Multi-crystalline (also called Polycrystalline): Made from cells cut from 

several silicon crystals. . The energy conversion rate efficiency is between 

9%-13% (Ideal Case) [5] 

Amorphous: The energy conversion rate efficiency is less than 6% (Ideal 

Case) 

A. TRACKING CONTROL: MPPT (Max Peak Power Tracker) 

It has an operating point at which the power produced is at its maximum and 

any movement away from this point will progressively decrease the 

efficiency of the panel. 

In order to extract all the energy that a solar panel is capable of delivering, a 

fully electronic system called the Max Peak Power Tracker (MPPT) is 

required. 

The MPPT is a DC-to-DC converter that poses as an optimum load, allowing 

the panel to operate at its peak-power state. 


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Since the Max Peak Power Point (MPP) is dependent on the amount of 

radiant sunlight and temperature of the panel, the MPPT must constantly 

adapt to maximize the energy conversion. 

The DC-DC conversion topology used by the MPPT depends on the difference 

in operating voltage between PV panel and battery. 

Under normal charging conditions, if the panel voltage is greater than the 

battery, a buck topology is used. Conversely, if the panel voltage is lesser, a 

boost topology increases the charging voltage with a reduced current 

In either case, the goal of the MPPT is to maintain the current extracted from 

the PV panel at the peak point. [7] 

Arduino Microcontroller 

Arduino is an open-source electronics prototyping platform based on flexible, easy- 

to-use hardware and software. It’s intended for artists, designers, hobbyists, and 

anyone interested in creating interactive objects or environments. The 

microcontroller on the board is programmed using the Arduino programming 

language (based on Wiring) and the Arduino development environment (based 

on Processing). Arduino projects can be stand-alone or they can communicate with 

software on running on a computer. The Arduino, matched with a couple of photo- 

sensors and a gear motor, makes an inexpensive solar tracking system: [6] 


Figure 1: Arduino Microcontroller Board 

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Main points: 

Sensing energy in external environment 

Analysis and visualization of energy over periods of time to increase our 

understanding of energy flow 

Actuators respond to environment and also act as inputs via feedback loop 

Remote interaction also possible via internet or wireless links 

Software in micro-controller allows a wide range of adaptability in behaviour 

Open source hardware and software allows changes to be made easily 

MOTORS: 

without the reliance on closed proprietary systems. This allows 

maintainability and flexible integration in the long term. 

A motor is an actuator. An actuator is a mechanical device for moving or controlling 

a mechanism or system. It takes energy, usually transported by air, electric current, 

or liquid, and converts that into some kind of motion. A motor is a device that 

converts other forms of energy into mechanical energy hence imparting motion. An 

electric motor converts electrical energy into mechanical energy. 

An electric motor can be a direct current (d.c) or alternating current (a.c) motor. 

The reference to d.c or a.c refers to how current is transferred through and from the 

motor. D.C motors use a constant single current 

D.C MOTORS 

D.C motors are best used where 

1. Speed needs to be controlled or varied. Speed is directly proportional to 

armature voltage; the higher the armature voltage the faster the speed of 

rotation. 

2. Torque needs to be controlled. Output torque is proportional to current; if 

the current is limited, then the amount of torque that can be achieved by that 

motor is also limited. 


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3. Simple circuitry is desired. A very basic drive for controlling speed and 

torque would require a little more than a large enough potentiometer. 

4. D.C motors provide continuous current and would be appropriate for 

application like driving wheels. 

From the start, DC motors are quite simple, apply a voltage to both terminals, and it 

spins. If you want to control which direction the motor spins just reverse the wires. 


Figure 2: A DC Motor 

If you want the motor to spin at half that speed; then use less voltage. Some 

considerations when using D.C motors are: 

• Voltage: DC motors are non-polarized - meaning that one can reverse voltage 

without any damage. Typical DC motors are rated from about 6V-12V. The larger 

ones are often 24V or more. But for the purposes of a robot, you probably will stay 

in the 6V-12V range. Voltage is directly related to motor speed as current is related 

to motor torque i.e. the more the voltage, the higher the torque. A DC motor is rated 

at the voltage it is most efficient at running. If you apply too few volts, it just won’t 

work. If you apply too much, it will overheat and the coils will melt. So the general 

rule is, try to apply as close to the rated voltage of the motor as you can. Also, 

although a 24V motor might be stronger, consider that it will need a 24v battery 

which increases the initial load. Unless really high torque needs to be overcome it’s 

better to stick to the 6-12V motors. 

• Current: As with all circuitry, attention must be paid to current. Too little won’t 

work and too much, meltdown occurs. When buying a motor, there are two current 

ratings you should pay attention to. The first is operating current. This is the 

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average amount of current the motor is expected to draw under a typical torque. If 

multiplied by the rated voltage then one will get the average power draw required 

to run the motor. The other current rating to pay attention to is the stall current. 

This is when the motor is powered up, but enough torque is put on it to force it to 

stop rotating. This is the maximum amount of current the motor will ever draw, and 

hence the maximum power that will ever be drawn. 

• Torque: When buying a DC motor, there are two torque value ratings which must 

paid attention to. The first is operating torque. This is the torque the motor was 

designed to give. Usually it is the listed torque value. The other rated value is stall 

torque. This is the torque required to stop the motor from rotating. Normally design 

is done using only the operating torque value. If you are designing a wheeled robot, 

good torque means good acceleration. A good idea would be if there are two motors 

on the robot, to ensure the stall torque on each is enough to lift the weight of the 

entire robot times your wheel radius. 

• Velocity: Velocity is very complex when it comes to DC motors. The general rule is, 

motors run the most efficient when run at the highest possible speeds. Obviously 

however this is not possible as it greatly compromises torque plus there are times 

when it would be wished that the robot to run slowly. So one may consider gearing - 

this way the motor can run fast, yet you can still get good torque out of it however 

gearing automatically reduces efficiency. 

• Control methods: The most important of DC motor control techniques is the H- 

Bridge. The H-Bridge is the link between digital circuitry and mechanical action. 

The computer sends out binary commands, and high powered actuators do the 

actual work. Most often H-bridges are used to control rotational direction of DC 

motors. Unless one buys a potentially expensive motor-driver, a H-bridge is needed 

to control any robot with a motor. After you have your H-Bridge hooked up to your 

motor, to determine your wheel velocity/position you must use an encoder. 


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SERVO MOTORS 

Servos are DC motors with built in gearing and feedback control loop circuitry and 

no motor drivers required. Servos are extremely popular with robots. Most servo 

motors can rotate about 90 to 180 degrees while some rotate through a full 360 

degrees or more. However, servos are unable to continually rotate, meaning they 

can’t be used for driving wheels (unless modified), but their precision positioning 

makes them ideal for robot arms and legs, rack and pinion steering, and sensor 

scanners to name a few. Since servos are fully self-contained, the velocity and angle 

control loops are very easy to implement and affordable. 

Since servos contain DC motors, dc motors stall current and torque characteristics 

apply. A Servo has an output shaft that can be positioned to specific angular 

positions by sending the servo a coded signal. As long as the coded signal exists on 

the input line, the servo will maintain the angular position of the shaft. As the coded 

signal changes, the angular position of the shaft changes. 

Figure 3: A Dismantled Servo Motor 

Servo motors are small, have built in control circuitry, and are extremely powerful 

for their size and draw power proportional to the mechanical load. The servo motor 

has some control circuits and a potentiometer (a variable resistor, aka pot) that is 

connected to the output shaft. This pot allows the control circuitry to monitor the 

current angle of the servo motor. If the shaft is at the correct angle, then the motor 

shuts off. If the circuit finds that the angle is not correct, it will turn the motor the 

correct direction until the angle is correct. The output shaft of the servo is capable of 


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traveling somewhere around 180 degrees. A normal servo is used to control an 

angular motion of between 0 and 180 degrees. A normal servo is mechanically not 

capable of turning any farther due to a mechanical stop built on to the main output 

gear. The amount of power applied to the motor is proportional to the distance it 

needs to travel. So, if the shaft needs to turn a large distance, the motor will run at 

full speed. If it needs to turn only a small amount, the motor will run at a slower 

speed. This is called proportional control. The control wire is used to communicate 

the angle. The angle is determined by the duration of a pulse that is applied to the 

control wire. This is called Pulse Coded Modulation. 

The servo expects to see a pulse every 20 milliseconds (.02 seconds). The length of 

the pulse will determine how far the motor turns. A 1.5 millisecond pulse, for 

example, will make the motor turn to the 90 degree position (often called the 

neutral position). If the pulse is shorter than 1.5 ms, then the motor will turn the 

shaft to closer to 0 degrees. If the pulse is longer than 1.5ms, the shaft turns closer to 

180 degrees. 

Therefore, where somewhat continuous medium distances and positional and/or 

velocity accuracy is important servo motors would be highly appropriate for 

example moving the robot from one station to another when the distance between 

them is fixed and known. 


Figure 4: A servo motor’s positioning pulses 

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STEPPER MOTORS 

A stepper motor is a permanent magnet or variable reluctance dc motor that has the 

following performance characteristics: 

i. Rotation in both directions, 

ii. Precision angular incremental changes, 

iii. Repetition of accurate motion or velocity profiles, 

iv. A holding torque at zero speed 

v. Capability for digital control. 

A stepper motor can move in accurate angular increments known as steps in 

response to the application of digital pulses to an electric drive circuit from a digital 

controller. The number and rate of the pulses control the position and speed of the 

motor shaft. Generally, stepper motors are manufactured with steps per revolution 

of 12, 24, 72, 144, 180, and 200, resulting in shaft increments of 30, 15, 5, 2.5, 2, and 

1.8 degrees per step. 

Stepper motors are either unipolar or bipolar. The unipolar stepper motor has five 

or six wires and four coils (actually two coils divided by centre connections on each 

coil). The centre connections of the coils are tied together and used as the power 

connection. They are called unipolar steppers because power always comes in on 

this one pole. 

Figure 5: Stepper motors 

Stepper motors that are bipolar require two power sources or a switchable polarity 

power source. The bipolar stepper motor usually has four wires coming out of it. 

Unlike unipolar steppers, bipolar steppers have no common centre connection. They 


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have two independent sets of coils instead. They can be distinguished from unipolar 

steppers by measuring the resistance between the wires. You should find two pairs 

of wires with equal resistance. If you’ve got the leads of your meter connected to 

two wires that are not connected (i.e. not attached to the same coil), you should see 

infinite resistance (or no continuity). 

Feedback is not always required for control, but the use of an encoder or other 

position sensor can ensure accuracy when it is essential. The advantage of operating 

without feedback is that a closed loop control system is not required. Generally, 

stepper motors produce less than 1 horsepower (746 W) and are therefore 

frequently used in low-power position control applications. 

Like other motors, stepper motors require more power than a micro controller can 

give them, so a separate power supply is required. To control the stepper, voltage is 

applied to each of the coils in a specific sequence from the micro controller through 

a driver like the H-Bridge. 


Figure 6: A unipolar stepper motor coils 

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Motor Sizing 

To size an electric motor for a particular drive application, the designer must first 

analyse the mechanics of the drive application. The following must be determined: 

Friction of the bearings, or other mechanical elements. 

The weight or load to be driven by the electric motor. 

Inertia of the mass to be moved or controlled. Acceleration and deceleration 

forces should be analysed. 

Mechanical system type and number of linkages. 

Friction - The friction may be determined by estimation, component specification 

or by measuring by use of a torque reading device or mechanism. 

Weight or Mass - The mass may be calculated using 3D CAD, specification or direct 

measurement. 

Inertia - Inertia is the force required to accelerate or decelerate a mass. Inertia is 

used to calculate the motor torque required to operate the mechanical system. 


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Mechanical System - There are roughly four categories of mechanical drive 

systems 

Direct drive 

Gear drive 

Tangential drive 

Lead-screw or worm-gear 

The total torque due to the four items outlined above is determined and the motor 

chosen should have a torque that exceeds this calculated torque. The power and 

voltage ratings of the motor are supplied in the manufacturer’s data sheet. The 

torque of the motor depends on the desired linear velocity (V). For example a lead- 

screw drive: 

DN 

V = 

1000 

Where: 

• V is the linear velocity in m/min 

• D is the pitch diameter of the lead screw 

• N is the speed of motor in revolutions per minute (rpm) 

So, once linear speed required is known, the number of number of revolutions of the 

motor can be calculated as above. The power rating is a product of the speed and 

output torque. 

P T 

Where: 

• P is the power rating of the motor 

• T is the output torque of the motor 

• ω is the angular frequency 

It is this torque that should exceed the calculated initial torque of the robot system. 

The angular frequency ω is given by 

2 

N 

 

60 

[8] 


23 

2012

SENSORS 

LED as light sensor 

Figure 8: LED used as light sensor for a Robot 

An LED can be used as a photodiode used for light detection as well as emission. 

This capability has been demonstrated and used in a variety of applications 

including ambient light detection and bidirectional communications.This 

implementation of LEDs is important because functionality can be added to designs 

with only minor modifications, usually at little or no cost 

An LED is a diode specifically made for efficient light emission and has been 

packaged in a transparent case. If inserted into a circuit in the same way as a 

photodiode, which is essentially the same thing, the LED will perform the same 

function. As a photodiode, it is sensitive to wavelengths equal to or shorter than the 

predominant wavelength it emits. For example, a green LED will be sensitive to blue 

light and to some green light, but not to yellow or red light. Additionally, the LED can 

be multiplexed in such a circuit, such that it can be used for both light emission and 

sensing at different times. 

Applications for this technology range from simple ambient light sensors to full 

bidirectional communications using a single LED. Applications benefit from the cost 

reduction of using the same component for multiple functions. 

Ambient light sensors 

LEDs have been used as ambient light sensors. For example, a remote control 

keypad backlight would be turned on by capacitive proximity sensors only in the 


24 

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absence of ambient light. The LED used for the backlight was also used as the 

ambient light sensor. This resulted in increased functionality for no increase in 

manufacturing costs. 

Bidirectional communications 

LEDs can be used as both emitters and detectors of light, which means that a device 

having only a single LED can be used to achieve bidirectional communications with 

another device meeting these requirements. Using this technology, any of the 

ubiquitous LEDs connected to household appliances, computers and other 

electronic devices can be used as a bidirectional communications port. 

One application for bidirectional communication with a single LED is fibre optic 

communications. In typical plastic optical fibre communications, a single optical 

fiber is used only for communication in one direction. This is because a single LED 

transmitter is placed at one end of the fiber, and a photodiode receiver is placed at 

the other end. Thus, two fibers are needed for bidirectional communication. 

However, if a single LED is placed at each end of a fiber, then the optical fiber can 

carry information in both directions using half the number of components as a 

typical system. This reduces system weight, cost and complexity. 

Another application of this use of LEDs is a proposed alternative to RFID tags called 

the iDropper, developed by Mitsubishi Electric Research Laboratories in 2003. The 

iDropper is a small device that consists of a microcontroller, a battery, an LED, and a 

single push-button. The device records or transmits a small amount of data upon 

command from the user. Compared to RFID tags, the iDropper is more secure 

because the user must press a button to reveal personal information, and is similar 

in cost. 

A single LED can only operate as a half-duplex transceiver; it can either transmit or 

receive information at one time, not both simultaneously. Simultaneous two-way 

communication requires both a forward and reverse channel and a second LED. 


25 

2012

Photocells 

Photocells are sensors that allow you to detect light. They are small, inexpensive, 

low-power, easy to use and don't wear out. For that reason they often appear in 

toys, gadgets and appliances. They are often referred to as CdS cells (they are made 

of Cadmium-Sulphide), light-dependent resistors (LDR), and photo-resistors. [10] 

A light-dependent resistor (LDR) is used to detect light. The LDR is a semiconductor 

device whose resistance decreases with increasing incident light intensity. LDRs 

made of cadmium sulphide are cheap, but have poor response time. The following 

illustrations show the variation of LDR resistance as a function of incident light and 

some sample LDR devices.78 

Figure 9: Variation of LDR resistance as a function of Incident Light (Picture shows an example of LDR) 

Thermistor 

A thermistor is a temperature-dependent resistor. A thermistor is one of the 

cheapest temperature sensors. There are two types: negative temperature 

coefficient (NTC) and positive temperature coefficient (PTC). As the name suggests 

for the PTC thermistors, as the temperature raises the resistance of the thermistor 

increases. For the NTC thermistors, as the temperature rises, the resistance of the 

thermistor decreases. The only drawback of thermistors is the lack of linearity of the 

response of the thermistor, that is, the resistance variation as a function of 


26 

2012

temperature is not a straight line, but is actually a nonlinear curve. It is possible to 

use the thermistor with a linear approximation in a small temperature range; 

however, for proper use, the thermistor must be linearized, whether with external 

components or a software table -based approach or by a mathematical model based 

on the Steinhart-Hart equation. In spite of these complications, the thermistor is an 

excellent temperature sensor, with fast temperature response time, and is widely 

used in thermostat applications. The next illustration shows the variation of 

temperature of the NTC as a function of temperature, and the photograph shows 

various thermistors. 

Figure 10: Variation of temperature of the NTC as a function of temperature. (Thermistor Picture) 

Storage 

Banks of batteries are used as energy storage after harvesting. Battery rating is a 

vital parameter that assists in the choice of the battery to settle at. 

B. CHARGER CONTROL 

Charge Controllers 

A charge controller or regulator prevents overcharging by limiting the current 

flowing into the batteries. The key to extending battery life in a solar system is to 

protect batteries from a complete discharge / overcharge. A charge controller is a 

power system component whose functions include regulation of solar charge 

current and in some cases to provide low battery protection. 


27 

2012

Main functions Include 

PWM (Pulse Width Modulation) Charging 

Direct, boost and float auto-charging modes 

High precision control 

LED indication of system working status 

Over load and short circuit protections 

Temperature compensation 

Real time clock and display 

Digital LCD display of parameters 

Optimized control for intelligent adjustment of control parameters 

Based on actual charging/discharging rates 

DC 12V or DC 24V auto work 

Arduino microcontroller can function like a charger controller .This minimizes the 

resources as the microcontroller can be used to replace charger controller. [13] 

C. Street Light Review 

Increased efficiency of power collection is done by the tracker. Hence, efficiency in 

usage is fundamental and paramount. The LDR is used to turn the lamp on and off 

automatically at dusk and dawn this reduces power wastage in switching. Efficiency 

is increased by making the street light intelligent in the sense that it’s automated 

LED lamps are more efficient than HID lamps, hence led lamp is the choice to 

increase efficiency. MOSFET vast properties makes it a good choice , for this 

application MOSFET can used as a variable voltage resistor .The microcontroller 

used is ARDUINO where a PWM is produced to control the MOSFET. The MOSFET 

then controls the voltage and the intensity of light is varied. [14] 


28 

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Specifications: 

Figure 11: Solar Security light at Kimathi University with one solar panel 

Solar panel 140 W ,monocrystalline conversion efficiency 15%, 30W. 

Light source Individual CREE LEDS ,2175 lumens ,0.3 – 2.0 foot-candles on 

the ground 

Pole 16 feet high made of galvanized steel 

Controller 12V ,10A solar charger controller 

Battery 12V,120Ah ,gel cell deep cycle battery 

Working time 8 ~ 10 hours/day, 2 ~ 3 cloudy or rainy days backup 

Wind Resistance 80mph 

Light Power 15W, 18W, 21W, 30W, 42W, 48W 

Pole Height 10 feet, 11 feet, 12 feet, 13 feet, 16 feet, 20 feet, 23 feet 

Battery Gel cell deep cycle battery or standard deep cycle battery, 


50Ah, 80Ah, 100Ah, 150Ah 

Battery Position Under ground, at the foot of the pole 

Table 1: Specifications of street lighting system 

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Applications 

Street Lighting 

Pathway Lighting 

Ramp Lighting 

Sidewalk Lighting 

Private Road Lighting 

Standard Features 

Solar Panel: over 25 years of power generation capacity 

LED Light: CREE LEDs provide super-bright light from little power, need 

simple thermal management, and last up to 50,000 hours, LED wattage is 

equivalent to approximately half the wattage of high pressure sodium light. 

Controller: over 8 years of typical operating life, automatic operation from 

dusk to dawn or timed ON/OFF operation 

Pole: up to 25 years of long life time 

Battery: 5 ~ 7 years of maximum life 

Benefits 

No line voltage, trenching, or metering 

No power outages 

Battery backup for cloudy or rainy days 

Distributed light and power - no single point of failure for enhanced security 

Easy to install with quick connect plugs - less than 1 hour 

No scheduled maintenance for up to 5 years 

No cost of replacing concrete, asphalt or landscaping 

No cost of transformers or meters to be added for electric service 

Qualify for savings from various state and federal taxes and incentives 

No monthly electric bills 


30 

2012

Controlled charging to prolong battery service life 

Long-life PV modules with more than 25 years of power generation capacity 

Environmentally friendly - 100% powered by the sun, solar panels reduce 

fossil fuel consumption, eliminating pollution 

Self-contained solution - Light on/off controlled by automatic daylight 

sensing or hour preset, no running or maintenance cost 

Better light source - LED lights feature cool white light without flickering and 

higher brightness than sodium lights 

Safe 12 volt/24 volt circuit, no risk of electric shock [14] 

Improved Solar Street Lights Using Two Solar Panels 


31 

2012

D. COMMUNICATION 

Wireless technologies 

Before starting the design of the system that will be developed it is important to 

describe some of the technology that will be involved in this project. It is important 

to mention about different wireless sensor networks (WSN) and some existing 

protocols. 

Wireless sensor networks have very small and efficient power consumption nodes 

that transmit information from the environment. The information is sensed and 

sent wireless through the network to finally arrive to a management centre where 

all the information is displayed. The information is then analysed and appropriate 

decision would be taken to decide what needs to be done. Wireless Sensor Network 

(WSN) can be used for example in monitoring temperature, pressure, moisture, 

pollution, sound, vibration, and many other variables that need to be known. An 

important aspect of a WSN is the power management and the network which needs 

an appropriate protocol in order to take care of the energy consumption. This point 

is very important because a sensor network normally has a battery as a source of 

energy and needs to last as long as possible. 

IEEE 802.11(Wi-Fi) 

Introduction 

The fast growing of wireless communication has contributed to less usage of cables. 

The devices that are suitable for this technology are many and some of the examples 

are mobile phone, personal computer and personal digital assistant (PDA) that 

needs to interact in order to share documents. These documents can come from 

several places such as email, information displays for customers in a shop or driver 

who wants to get access to map and tourist information while driving on the motor 

way. All this conveniences has been developed through the technological point of 

view. 


32 

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Wi-Fi is derived from the decades old term Hi-Fi that stands for the output’s type 

produced by quality music hardware. Wi-Fi Technology is WIRELESS FIDELITY and 

stands for all those technologies that fall under the specifications of IEEE 802.11 

including 802.11a, 802.11b and 802.11g. The association of the term Wi-Fi with 

various technologies is merely because of the promotions made by the Wi-Fi 

Alliance. 

Wi-Fi is also associated with 802.11 networking. The reference is derived from IEEE 

– Institute of Electrical and Electronics Engineers uses the numbering system for 

classifying a range of technological protocols. 

802.11 

802.11 is the Wi-Fi standard set by the IEEE for WLANs. There are different variants 

of 802.11, the most common being: 802.11b (2.4GHz, max data rate 11Mbit/s), 

802.11g.(2.4GHz, max data rate 54Mbit/s) and 802.11a (5Ghz, max data rate 

54Mbit/s). 802.11n (5 GHz and/or 2.4 GHz, 74-600Mbits/s) is the next proposed 

standard and is currently still in draft specification (after 4 years). 

802.11 standards define rules for communication on wireless local area networks 

(WLANs). Popular 802.11 standards include 802.11a, 802.11g, and 802.11n. Many 

products conform to the 802.11a, 802.11b, 802.11g, or 802.11n wireless 

standards collectively known as Wi-Fi technologies 

802.11b uses the same unregulated radio signalling frequency (2.4 GHz) as the 

original 802.11 standard. Vendors often prefer using these frequencies to lower 

their production costs. Being unregulated, 802.11b gear can incur interference from 

microwave ovens, cordless phones, and other appliances using the same 2.4 GHz 

range. However, by installing 802.11b gear a reasonable distance from other 

appliances, interference can easily be avoided 

802.11a supports bandwidth up to 54 Mbps and signals in a regulated frequency 

spectrum around 5 GHz. This higher frequency compared to 802.11b shortens the 

range of 802.11a networks. The higher frequency also means 802.11a signals have 

more difficulty penetrating walls and other obstructions. 


33 

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802.11a has fast maximum speed; regulated frequencies prevent signal interference 

from other devices while it is of highest cost; shorter range signal that is more easily 

obstructed 

The newest IEEE standard in the Wi-Fi category is 802.11n. It was designed to 

improve on 802.11g in the amount of bandwidth supported by utilizing multiple 

wireless signals and antennas (called MIMO technology) instead of one. 

802.11n has fastest maximum speed and best signal range; more resistant to signal 

interference from outside sources whereas its standard is not yet finalized; costs 

more than 802.11g; the use of multiple signals may greatly interfere with nearby 

802.11b/g based networks 

Wi-Fi communication devices are extended forms of radios used for cell phones and 

walkie-talkies: they simultaneously transmit and receive radio waves and convert 

1s to 0s into the radio waves along with reconverting the radio waves into 1s and 0s, 

however the Wi-Fi radios enjoy some exceptional features. 

Basic operation 

Powered Wi-Fi station starts by scanning accessible channels to detect active 

networks in areas where beacons are located for transmitting. A network is then 

selected which will be in ad hoc mode. After this section it verifies itself with the 

access point (AP) and joins it. Several qualities of service (QoS) degrees are available 

in Wi-Fi network. Even though a station is already a part of a network it still tries to 

detect new networks and the reason for such behaviour depends on the willing to 

associate with the strongest signal and if this occurs the current network 

disconnects itself and joins the new network. This character is called roaming where 

networks share a common distribution system. Power in Wi-Fi stations can be saved 

by setting a station in to sleep mode. 

Power management 

The design of Wi-Fi connection is constructed mainly for long range communication, 

which then leads to higher absorbing of current. The absorbing range for Wi-Fi 

devices is around 100-350 Am. Wi-Fi devices can be at two different state and those 


34 

2012

are awake or doze. When a station is located in doze state it cannot transmit or 

receive. The power consumption is then reduced at this state. The power 

management is handled by two modes in Wi-Fi devices and these are active mode 

(AM) and power save (PS) mode. PS mode is handled in different ways depending 

on the type of topology the network is based on. 

Infrastructure Network- A station in AM which wants to pass in PS must signal the 

AP by using the power management bit in the header of its packets. The AP stores all 

the traffic addressed to stations that are in PS mode; when transmitting the periodic 

beacon, the AP sends the list of stations in PS mode and whether it has traffic 

queued for them at regular and configurable time intervals, the stations in PS switch 

to AM in order to receive the beacon. If there is traffic addressed to them, the 

stations can receive it and then return to PS. 

Ad Hoc Network- Stations can use the PS mode, but the task of storing the traffic 

addressed to them is distributed among all the active stations since no AP exists. All 

stations in PS mode switch to awake state in a temporal window (ATIM window) 

during which the stations that have traffic stored for others send special frames 

(ATIM frames). If a station receives an ATIM frame addressed to it, it remains in 

AWAKE state in order to receive its traffic; otherwise, the station returns to PS 

mode until the next ATIM window is started. Note that: “• Due to the absence of a 

reference station such as the AP, the instantaneous state of a station (awake or 

doze) can only be estimated by all other stations of the ad hoc network (e.g., 

according to the history of past transmissions). In this topology, the standard does 

not specify any methodology for estimating the power state of the stations. 

• The transmission and reception of the ATIM frames during the ATIM window 

occur according to DCF rules, i.e. according to the CSMA/CA access method. It means 

that a station could receive an ATIM frame addressed to it-self, wait for the data, and 

yet not receive them because of congestion on the shared channel. In conclusion, the 

Wi-Fi standard specifies only one low-power state, the Doze state. 


35 

2012

Advantage and disadvantage 

Wireless techniques provide many advantages, but leads to some disadvantage as 

well. The disadvantage of Wi-Fi network is the power consumption that is required 

before a transmission can be approved compares to Bluetooth which is extremely 

low in short ranges. But on the other hand Wi-Fi is more convenient when 

transmission of data is required for long range and power consumption is not an 

issue. 

Figure 13: Wi-Fi Operation 

Wireless Fidelity (Wi-Fi Technology) provides so much entertainment and 

information than before with because it enables all devices like PC, games, mp3 

player, smart phone, laptop, printer and other tangential. The uses of the Wi-Fi 

Technology contain any type of WLAN product support any of the 802.11 together 

with dual-band, 802.11a, 802.11b. Wi-Fi Technology is through accessible hot Spots 

like Home, Office, Airports, Hotels, Railway stations, Restaurants etc. 


36 

2012

Bluetooth (IEEE 802.15.1) 

Introduction 

Bluetooth is wireless technology where devices can communicate with each other 

within a short range. The specification is based upon the Radio Frequency (RF) 

operating in the unlicensed 2.4GHz ISM (Industrial, Scientific and Medical) band and 

the technique is based on low-cost, short-range radio link which makes it easy to ad- 

hoc connections for stationary and mobile communication environments. The 

specification is available for areas such as short-range, point-to-multipoint, voice 

and data transfer. 

Bluetooth technology is a wireless protocol that connects electronic devices while 

they are close to each another like computers, phones up to a distance of 100 

metres. There are three class categories of range - Class 1, Class 2 and Class 3, which 

the operation of the device depends on. The highest range of operation falls under 

Class 1 Radios, which is of 100 meters or 300 meters range. This category is 

specifically used in case of the industries and generally not for domestic purpose. 

The second highest range is Class 2 Radios, with an operation range of 10 meters or 

30 meters. This category has found its scope in case of the mobile devices. Lastly, the 

Class 3 Radios is used to operate the devices within a very short range of 1meter or 

3 feet. 

Bluetooth connects a device to the other through the latest network system - 

commonly called "Piconets". This technology smartly operates at 2.40 GHz to 2.485 

GHz ISM band, while only the former (i.e. 2.40 GHz) is unlicensed and easily 

available in most parts of the world. ISM, here, refers to Industrial, Scientific and 

Medical band, 

Bluetooth technology uses spread spectrum, frequency hopping and full-duplex 

signal at a rate -- as lower as - 1600 hops per second. AFH -- Adaptive Frequency 

Hopping is another supportive technology, which makes the Bluetooth interference 

tolerant. This enables Bluetooth to send and receive an interference free 


37 

2012

transmission. The latest version of Bluetooth technology is 2.0+ Enhanced Data 

Rate, which supports a data rate of 3 Mbps. 

You can use Bluetooth for the following: 

Connect to your PC or laptop to transfer files. 

Share data with other users - including contacts, diary entries, documents 

and photos 

Connect to the Internet for surfing or email, via a Bluetooth-enabled modem 

or access point 

Connect to a Bluetooth GPS unit for satellite navigation 


The functionality of Bluetooth communication is based on frequency hopping 

system with a nominal hopping rate of 1600 hops per second. The hops are divided 

into time slots, each 625 µsec long. The reason why Bluetooth uses frequency 

hopping is for low interference and fading. For full duplex transmission it uses TDD 

(Time Division Duplex) scheme and transmits by using GFSK (Gaussian Frequency 

Shift Keying) modulation. 

Bluetooth protocol uses a mixture of circuit and packet switching. The protocol 

stack can use an asynchronous connection–less (ACL) link for data and up to three 

simultaneous synchronous connection-oriented (SCO) links for voice or a mixture of 

asynchronous voice (DV packet type). When two or more application are connected 

to the same channel in Bluetooth network it creates a piconet, which contains a 

master device and up to seven active slave devices. Interference becomes greater in 

Bluetooth communication when the amount of piconet increases. This courses a 

packet collision that needs retransmission. The reason to this is because of the 

randomly frequency hopping system provided by the Bluetooth communication 

amongst a total of 79 frequencies. A Bluetooth device can function in either master 

or slave mode. The maximum number of device which a piconet can contain is eight 


38 

2012

devices seven active slaves plus one master see figure 12, which is the simplest 

configuration of a Bluetooth network. 

To be able to communicate among Bluetooth devices some kind of function for 

device discovery has to be implemented before any communication can occur for 

packets to transmit on the wireless link between master and slave devices and vice- 

versa. The function for device discovery contains inquiry and paging. Its purpose is 

to help find the destination address for devices with unknown source. The inquiry 

function can also be used to detect which other Bluetooth devices are within the 

range. Under an inquiring sub state the detecting device gathers the Bluetooth 

devices addresses and clocks of all units that respond to the inquiry message. It can 

then, if desired, make a connection to any one of them by means of the page 

procedure, where the paged device is contacted directly and invited to join a 

piconet. 


Figure 14: Piconet Configuration 

Power management is crucial aspect when it comes to wireless communication 

since it affects the battery lifetime. Conserving battery energy in mobile application 


39 

2012

is a hard challenge since consideration has to be taken in the entire protocol stack 

layers. The design of Bluetooth devices should be constructed in such way that it 

won’t be a burden on the battery lifetime. To avoid high power consumption in 

Bluetooth radio different levels of power conserving mode are included in the 

constructions and some of them are sniff, hold and park. Some other aspects that 

need to be considered too are base band mode and adaptive transmission power. 

The absorbing range for Bluetooth devices is around 1-35 Am. 


The main disadvantage with Bluetooth is the limitation of how far it can reach 

considering the range between devices communicating with each other. Another 

aspect that is also disadvantage for Bluetooth technology is the number of devices 

that can be connected simultaneously is only 7 devices. Now the positive side of 

Bluetooth is the power consumption since it consume very little power while active 

it give a beneficial of long time battery life compare to Wi-Fi which only last for 

couple of hours. 

Comparison between Wi-Fi and Bluetooth 

Both have lots of features of connectivity, printing and transferring of data. The 

technology of Bluetooth is functional when broadcasting of information among 

more than two devices exist near as headset, modem, printer etc. while Wi-Fi 

operating on full scale because it is a much faster than Bluetooth. No doubt Wi-Fi 

and Bluetooth is the basic need of modern age but have some differentiation as 

follow. 

The hardware requirements of Wi-Fi and Bluetooth are entirely different, Through 

Bluetooth adapter you can connect devices with each other. While in Wi-Fi network 

you need an adapter, router and access point to enable connection. The bandwidth 

required for Bluetooth is only 800 kbps and for Wi-Fi 11Mbps bandwidth require. 

Wi-Fi network come into existence in 1991 and Bluetooth in 1994.The specification 

of Bluetooth is SIG and Wi-Fi is IEEE, and WECA. 


40 

2012

The specification of Bluetooth are a lot as the usage is very simple and various 

devices can be connected at a time .You can also switch between devices via 

Bluetooth. In other hand Wi-Fi network is a complex network and hard to configure. 

You can use various devices with Bluetooth such as automation devices, mobile 

phones, keyboard, and mouse. While in Wi-Fi network server, desktop, and 

notebook computer can be used. The rising issue of Wi-Fi and Bluetooth is the range 

because the range of Bluetooth is 10 meters and as compared to Bluetooth Wi-Fi 

offering 100 meters range for user to make it more beneficial for user. 

The security level of both Bluetooth and Wi-Fi is also different from each other. 

Bluetooth has only 2 level of password to wrap little distance and escape user time. 

Wi-Fi is a risky network because when lots of network attached with each other, 

then a hacker may try to access toward connected user and if succeed your data may 

be stolen. The power used for Bluetooth is very low and for Wi-Fi it should be high 

because Wi-Fi has long range of connectivity and Bluetooth have low. The 

similarities in both are frequency because both technologies have same frequency 

which is 2.4 GHz. 

Bluetooth is non-resident tools while Wi-Fi is residential equipment and its 

purposes. Both technologies are wireless but for different purposes. Wi-Fi used to 

get access toward local area network in working areas while Bluetooth used to carry 

out personal application as smart energy. As we know Wi-Fi is an Ethernet network 

and a user should configure it to get quick access to internet .Through Wi-Fi 

transformation of files become easy. Users can also use hands-free and headset 

devices because it has a strong connection. Wi-Fi proves good because it provide full 

strength network to enable fast connection. Same as Bluetooth is also very efficient 

technology for transformation of data between next to devices as telephone, 

modem, headset etc. 

Both technologies are different because Bluetooth is a slow as compared to Wi-Fi 

because Wi-Fi is a fastest technology therefore Wi-Fi also unsuited with it. Wi-Fi 

enabled more and more user to connect with each other via wireless network. So 

Bluetooth and Wi-Fi have some resemblance but these both technologies 

complement each other due to their feature of connectivity, sharing, and speed. 


41 

2012

When we use these two technologies we can get better and battiest result of any 

project. Wi-Fi enabled you to connect with internet without any wires but when you 

are exist in the range of hotspot, because Wi-Fi works only in its specific range while 

Bluetooth offering quick exchanging of data and sharing opportunity of printer, 

laptop etc. In short the use of both technologies increasing day by day and both has 

something to looking forward. 

IEEE 802.15.4 and Zigbee 

Introduction 

IEEE 802.15.4 or Zigbee is a wireless personal area network (PAN) which can be 

used in several areas. Some basic areas where it can be utilize are building 

automation, control devices, personal healthcare, PC peripherals and consumer 

electronics. 

The main technology used to develop the wireless network for IEEE 802.15.4 and 

Zigbee is based on the same layers which are physical (PHY) and medium access 

control (MAC). The huge different between IEEE 802.15.4 and Zigbee is the ability of 

which kind of topology can be provided by the network. More over the security level 

in Zigbee is higher compare to IEEE 802.15.4. The IEEE 802.15.4 can provide point- 

to-point and point-to-multipoint topology, called star topology, while Zigbee can be 

used for the one’s mentioned above plus cluster tree and mesh topology. To achieve 

the functionalities which Zigbee can provide two more layers from the Open System 

Interconnection (OSI) is added and those are Network and Application layers. 

Zigbee is a technology of data transfer in wireless networks. It has low energy 

consumption and is designed for multi-channel control system, alarm systems and 

lighting control. It has also other various home and industry applications. Zigbee is 

more economical than WIFI while Bluetooth protocol also consumes more energy, 

and has the greatest scattering of parameters of conventional like compatible units. 

This is caused by the fact that Bluetooth does NOT have a unified data transfer 


42 

2012

standard. Still that does not mean that Zigbee is oriented towards autonomous use. 

Key links of Zigbee are network coordinators and routers. 

Moreover, Zigbee is the set of specs built around the IEEE 802.15.4 wireless 

protocol. The IEEE is the Institute of Electrical and Electronics Engineers, a non- 

profit organization dedicated to furthering technology involving electronics and 

electronic devices. The 802 group is the section of the IEEE involved in network 

operations and technologies, including mid-sized networks and local networks. 

Group 15 deals specifically with wireless networking technologies, and includes the 

now ubiquitous 802.15.1 working group, which is also known as Bluetooth®. The 

standard itself is regulated by a group known as the Zigbee Alliance, with over 150 

members worldwide. 

While Bluetooth® focuses on connectivity between large packet user devices, such 

as laptops, phones, and major peripherals; Zigbee is designed to provide highly 

efficient connectivity between small packet devices. As a result of its simplified 

operations, which are one to two full orders of magnitude less complex than a 

comparable Bluetooth® device, pricing for Zigbee devices is extremely competitive, 

with full nodes available for a fraction of the cost of a Bluetooth® node. 

Zigbee devices are actively limited to a through-rate of 250 Kbps, compared to 

Bluetooth’s much larger pipeline of 1Mbps, operating on the 2.4 GHz ISM band, 

which is available throughout most of the world. 

PHY layer 

The physical layer main purpose is to control the radio of the device to evaluate the 

energy detection (ED) inside the channel and thereby impose Clear Channel 

Assessment (CCA) for Carrier Sense Multiple Access with Collision Avoidance 

(CSMA/CA). This control has to be introduced to avoid failure in transmission of 

data within a channel. What consumes most power in devices containing the PHY 

layer is idle listening. The on-going consumption can be reduced by setting the 

Radio Frequency (RF) transceiver into sleep mode for a certain time and after that 

back to active mode. Three frequency bands is available in IEEE 802.15.4 with a 


43 

2012

total number of 27 channels, where 16 is applied to the 2.4 GHz, 10 for 915 MHz and 

finally 1 for 868 MHz Devices that are constructed with IEEE 802.15.4 protocol stack 

implemented in it uses Direct Sequence Spread Spectrum (DSSS) to raise the 

bandwidth of the transmitted signal for a reliable communication. The physical 

specifications are given in the table 1 below. 

The IEEE 802.15.4 MAC Layer 

Table 2: Specification of IEEE 802.15.4 

Applications for IEEE 802.15.4 wireless sensor networks are target for home 

automation, home networking, PC peripherals, and home security and so on. Several 

of those application demands only low-to-medium bitrates around some few 

hundreds of kbps. The physical layer provides different bitrates depending on which 

frequency range is applied by the device. The frequency also decides how many 

channels are available within the frequency range. MAC protocol uses only one of 

these channels at a time. Since it is the MAC layer that is used to link communication 

between devices a general description of how device get associated and 

disassociated on the network follows below, which is according to the book: 

Protocols and Architectures for Wireless Sensor Networks. 

• A Full Function Device (FFD) can operate in three different roles: it can be a 

PAN coordinator, a simple coordinator or a device 

• A Reduced Function Device can operate only as a device A device must be 

associated to a coordinator node (which must be a FFD) and communicate 

only with this way forming a star network. Coordinator can operate in peer- 

to-peer fashion and multiple coordinators can form Personal Area Network 


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(PAN). The PAN is identified by a 16-bit PAN Identifier and one of its 

coordinators is designed as a PAN coordinator. 

A coordinator handles among others the following task: 

• It manages a list of associated devices. Devices are required to explicitly 

associate and disassociate with a coordinator using certain signalling 

packets. 

• It allocates short addresses to it devices. All IEEE 802.15.4 nodes have a 64- 

bit device address. When a device associates with a coordinator, it may 

request assignment of a 16-bit short address to be subsequently in all 

communications between device and coordinator. The assigned address is 

included in the association response packet issued by the coordinator. 

• In the beaconed mode of IEEE 802.15.4, it transmits regularly frame beacon 

packets announcing the PAN identifier, a list of outstanding frames, and other 

parameters. Furthermore, the coordinator can accept and process requests 

to reserve fixed time slots to nodes and the allocation are indicated in the 

beacon. 

• It exchanges data packets with devices and with peer coordinators. 


The main focus of IEEE 802.15.4 protocol is its ability to deliver low power 

consumption and low-rate wireless communication devices. The following numbers 

of channels can be used in IEEE 802.15.4, which is 16 channels for ISM 2.4GHz, 10 

channels for ISM 900 MHz and 1 channel for 868 MHz The PHY-layer used in IEEE 

802.15.4 provides Link Quality Indicator (LQI) for the communication that occurs 

between transmitter and receiver in order to maintain good quality of signals 

transmitted between nodes. The MAC layer which is utilized in IEEE 802.15.4 for 

communication is based on Carrier Sense Multiple Access with Collision Avoidance 

(CSMA/CA) mechanism to get admission of the channels. Devices that are supported 

by IEEE 802.15.4 are Full Function Device (FFD) and Reduced Function Device 

(RFD). A device which is constructed as FFD can be used for both FFD and RFD in 


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communication. FFD can also be set as PAN Coordinator, Router or End Device, 

while RFD is only suitable as End Device. Communication for RFD can only occur 

with FFD. An overview of how the protocol stack is defined for IEEE 802.15.4 is 

shown in the figure below. 

There are two types of communication mode process available in IEEE 802.15.4 for 

avoiding interference in an environment where several system are running on the 

same frequency band. The modes which help to reduce the disturbance are beacon 

mode and non-beacon mode. 


Figure 15: IEEE 802.15.4 protocol stack 

The beacon mode is used with Star-type networks that are configured with the 

network management node, referred to also as the “PAN coordinator”, at the core. 

The PAN coordinator sends off a beacon signal at fixed intervals, while other nodes 

synchronize with this beacon signal and perform communications during allotted 

periods. Since only the node that has been singularly assigned by the coordinator 

gains exclusive use of the channel, it becomes possible to conduct communications 

in which no collisions can occur. This mode, therefore, is used for communications 

46 

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equiring low delay levels. The non-beacon mode, on the other hand, is a mode 

wherein the channel is accessed constantly with the CSMA-CA. When this mode is 

used in a mesh link, with which direct communications are conducted with 

peripheral nodes, each node can directly communicate with any other mode at any 

time, while each node can also be ready to receive data addressed to that node, at all 

times. This need for each node to constantly remain in a reception standby 

condition makes it impossible to conserve energy by conducting intermittent 

operations as in the case of the beacon mode. 

Energy conserving process is available in End Devices by introducing non-beacon 

mode in a Star-link situation where the master unit is set as constant reception in a 

standby condition. To achieve this behaviour the End Devices are set to interrupt 

periodically in suspended or standby condition. Introducing this function in the End 

Device will enable request to receive data is periodically sent to master unit from 

End Devices. This is the main flow pattern for data in sensor networks. The figure 

below is an example of two types of topology that is available in IEEE 802.15.4. 

Figure 16: IEEE 802.15.4 star and peer-to-peer 


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The main focus for power management for IEEE 802.15.4 is based on low cost, low 

consumption and low data rate. Implying all this aspect together gives us a 

significant protocol that consumes extremely low power. 


There are several reasons for why it is convenient to impose IEEE 802.15.4 protocol 

for wireless sensor network in areas where the need for transmission of data-rate is 

low and requirement of energy conserving is a huge concern. First of all it provide 

long battery life, due to it low transmission speed which is about 250kbs/s. 

Secondly it is easy to imply in systems and quite simple to use for development of 

networks. IEEE 802.15.4 sensor networks can handle up to 64000 devices 

simultaneously compare to Bluetooth which can only support 7 devices at the same 

time. The only disadvantage that is provided by IEEE 802.15.4 protocol is it data 

transfer ability. [11] 

Figure 17: ZigBee Network Model 


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Figure 18: Xbee Modules (One to act as a Coordinator and the other as the Router) 

An important requirement for the wireless network is the plug & play functionality. 

XBee is the RF-module which provides the wireless communication and collection of 

information from the sensor nodes, for supervising of the water fluid, electricity or 

temperature, see figure 1. The server transmits further the information from the 

customer to the host system through internet connection. 

Figure 19: Principle Structure of the X-Bee System 


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Figure 20: Reference Pin out (Xbee) 

The DTR, RTS, RESET and RX pins (going into the Xbee) pass through a level 

converter chip that brings the levels to 3.3V. You can use pretty much anywhere 

between 2.7 to 5.5V data to communicate with the XBee. The breakout pins on the 

bottom of the board are not level shifted and you should try to keep data going 

directly into the XBee pins under 3.3V [12] 

Description of ZigBee technology 

ZigBee is a protocol that uses the 802.15.4 standard as a baseline and adds 

additional routing and networking functionality. 

The ZigBee protocol was developed for a network protocol that can be used in a 

variety of commercial and industrial low data rate applications. ZigBee is designed 

to add mesh networking to the underlying 802.15.4 radio. It is a technology for 

implementing low-cost, low-power wireless control networks requiring high 

flexibility in node placement. 


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It is designed for low power applications, it fits well into embedded systems and 

those markets where reliability and versatility are important but a high bandwidth 

is not required. 

The table below shows the comparison between the various wireless technologies 

and their application 

FOCUS 

APPLICATION 

Zigbee and 

802.15.4 

Monitoring 

and Control 


GSM/GPRS/CDMA 802.11 BLUETOOTH 

Wide area voice 

and data 

High speed 

internet 

Device 

connectivity 

BATTERY LIFE years 1week 1 week 1 week 

BANDWIDTH 250 kbps Up to 2 mbps Up to 54 

TYPICAL 

RANGE 

ADVANTAGES Low power 

mbps 

100+ meters Several kilometres 50-100 

cost 

Table 3: Zigbee Comparison 

Existing 

infrastructure 

meters 

Speed 

ubiquity 

Reason for the application of Xbee module in this system 

a. Large number of nodes/sensors 

b. Very low system/node costs 

c. Operation for years on inexpensive batteries 

d. Reliable and secure links between network nodes 

e. Easy deployment and configuration 

f. Global solutions 

720 kbps 

51 

10-100 meters 

Convenience 

g. ZigBee technology protocol has proven that NO message is lost on transfer of data. 

2012

CHAPTER 3 

Methodology of Implementation 

Equipment: - 

Bread Board 

Arduino Micro controller 

5V, 12V Dc Power supply 

Light Sensor 

Lamp (Light Source) 

Temperature Sensor 

Servo Motor 

Zigbee Technology (Two XBee Modules) 

Computer (Control Centre) 

Solar Panel 

Control grid 

Relays 

Operation of the Tracking System: 

First control grid was designed, which composed of a stand, servo motor and the 

solar panel surface. Two LDR’s were placed at the both ends of the control grid 

adjacent to each other. The LDR’s were used to sense the solar light intensity; 

important for the solar panel orientation, the output signal was read by the 

analogue inputs of the Arduino Microcontroller. The microcontroller was 

programmed such that, according to the input signal it controlled the servo motor 

by sending a signal via the digital pins. I wished to use the Mono-Crystalline solar 

module which is made from cells cut from single silicon crystals but replaced that 

with an adjustable DC power supply from the LAB 4 – K.U.C.T. The energy 

conversion rate efficiency for a mono – crystalline solar panel is 16% (Ideal Case). 


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The Solar Panel, temperature sensor, motor and light sensor were connected as a 

unit to the Arduino microcontroller and the source code saved separately. The servo 

motor rotated the panel in the X coordinates with respect to the position of the 

source of light (X-axis only since Nyeri town relies only on the equatorial axis). The 

Arduino reads the position of the light source via the deviation of the electrical 

readings from the 2 LDR sensors and carries out signal conditioning according to 

the program that was wrote and outputs the signal via the PWM port outputs of the 

Arduino (N.O 9) to rotate the servo motor. The Arduino reads the temperature from 

the temperature sensor and the energy stored in the battery. 

When the source of the light intensity is changed, the control grid tracks the source 

of light. This is achieved through the feedback loop of the sensors. The servo motor 

receives a signal from the microcontroller and adjusts so as to achieve the tracking 

mechanism. The servo motor can rotate 180 degrees (but 360 degrees in other 

types of servo motors) but in this case I intend to move it from East to West (0 – 180 

degrees) since Nyeri is located along the equator where we don’t have much 

equinox variation. 


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Block Diagram of Improved solar tracking system (STS) 

Figure 21: Block Diagram 


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Signal Flow Diagram 

ACTUATORS 

Stepper Motors 

Mechanical System 

SENSORS 

Light Sensor 

Temperature Sensor 

Energy Sensor 

OUTPUT SIGNAL CONDITIONING AND 

INTERFACE 

Digital to Analogue Converter 

Figure 22: Signal Flow diagram 

Arduino as a Charger Controller 

The Arduino Microcontroller acts as a Charger Controller normally used in solar 

system circuitry. It has a total of 5 nodes connected to the Arduino of which I 

specifically chose two of them to connect to the Zigbee module via Java based 

programming so as to monitor energy usage. 


55 

INPUT SIGNAL CONDITIONING AND 

CIRCUIT INTERFACE 

Analogue to Digital Converter 

DIGITAL CONTROL ARCHITECTURE 

Arduino Microcontroller 

Xbee Module 

Router 

Xbee Module 

Coordinator 

Computer 

(Control Centre) 

2012

Street Light Implementation 

Increased efficiency of power collection is done by the tracker. Hence, efficiency in 

usage is fundamental and paramount. The dimmer circuit is used to control the 

energy harvested in a more efficient way. A day – night circuit was designed which 

would switch between the tracking system (day) and Dimmer circuit (night) 

systems. An LDR was used to detect light intensity between day and night and this 

would turn the lamp on and off automatically at dusk and dawn thus reduces power 

wastage in switching. Efficiency is increased by making the street light intelligent in 

the sense that it’s automated LED lamps used are more efficient than HID lamps, 

hence led lamp is the choice to increase efficiency. The dimmer circuit varied from 

6v to 12v and down to 6v according to the program written to the Arduino 

microcontroller. This period of switching was designed to take place between 

6.00PM and 6.00AM East African Time. Also in this circuit, nodes connecting to each 

relay switch of the dimmer circuit were connected to the Arduino as well as the 

node from the DAY-NIGHT switch which was also displayed in the X-CTU (Zigbee 

display terminal). 

Thus the Arduino (2560) shall perform the following functions due to its vast 

applications, i.e.: 

PWM (Pulse Width Modulation) Charging & Tracking system 

Direct, boost and float auto-charging modes 

High precision control 

LED indication of system working status 

Over load and short circuit protections 

Temperature compensation via LM35 sensor used 

Real time clock and display via 16 x 2 LCD display 

Optimized control for intelligent adjustment of control parameters 

Based on actual charging/discharging rates 

DC 12V or DC 24V auto work (Charger controller) 

Tx and Rx for Zigbee Protocol (Transmission and Receiver capability for 

advanced low cost low power communication) 


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Communication System Methodology 

Zigbee Technology is a communication protocol, where an X-Bee device is used for 

the protocol. At the end point device I used an LCD display for monitoring 

temperature and system process. After each of the system components was 

established and worked, the remaining bit was to interconnect them and have a 

single program to run it. I need to take readings from all nodes and transfer the data 

from a remote area to a central destination (Control centre). The data read is then 

sent from the Xbee module router and sent wirelessly to the other Xbee Coordinator 

and information is displayed on the Computer. I programmed the Xbee modules 

needed for the system Point to Point communication. I would have rather designed a 

Point to Multipoint communication but for our prototype system a P2P was more 

preferable. 

Xbee Module: It is a very small piece of hardware that can connect wirelessly with 

another using the Zigbee communication protocols. There are many different 

models, including aerial types and power outputs for which my case I am using an 

XB24 Series 2 model which can transmit 10m indoor or 100m outdoor which I have 

tested and experienced. Other models of XBee can transmit up to 1.6km outdoor, 

and that is interesting owing to the low power low cost and maintenance. 

Temperature Connection: I used an LM35 sensor device which is calibrated to 

record voltage deviation analogously and read via the Arduino pins. Since the 

readings vary between 0 -1023, I needed to change them to voltage and temperature 

(Celsius) using the following arithmetic equations: 

val = analogRead(analogPin); // Reading hexadecimal inputs from 0 - 1023 

volt = (val/1023)*5; // Converting Hexadecimal inputs to voltage by 

mapping 0-1023 to 0-5v of the voltage peaks of the Arduino. 

temp= volt*100; // Converts voltage read to Temperature in Celsius 


57 

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Figure 23: LM35, LCD connections to Arduino 

Control Unit (Computer): Data graphing, analysis and storage, monitoring of 

energy production from on-site renewable solar energy, was used to help in 


58 

assessing feasibility study of 

renewable energy systems and 

grid distribution. I used my 

personal laptop for this project. I 

downloaded software – X-CTU 

with interface shown below so as 

to configure and monitor XBee 

data. I used the X-CTU software to 

configure one of the XBee chip as 

Coordinator and the other as 

Router. 

Figure 24: X-CTU Software 

2012

Figure 25: XBee Connection - Coordinator and Router 

Results & Analysis 

The system behaves automatically in such a way that the solar panel follows the 

position of the sun light to enable full utilization of the sun rays (energy). 

For the street light application, the intensity of the LED Lamp was varied via the 

dimmer circuit configuration hence the efficient utilization of the stored energy. 

More to that data is collected from the available nodes: LDR’s, charge of the battery, 

and the temperature outside (via LM35 sensor) etc. and transferred via the Zigbee 

technology which is a more secure gateway than IR and Bluetooth. 


59 

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Thus basically the figure shown below shows LDR-Resistor connections on the 

Panel Grid which are used for automatic Tracking control system where the solar 

panel (Photovoltaic-PV system) follows the position of the sun and sends data 

(secure) via Zigbee technology 

Alongside shows the X-CTU data received after the router sends the node signals 

and received by the 

Coordinator. Shown are the two LDRs readings in hexadecimal, the voltage read, 

values read from LM35 temperature sensor as well as the Day-Night Switch which 

switches between day and night. 

Figure 26: LDRs connection on solar plate 


60 

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Figure 27: XBee readings on the control Terminal 

Then by using a hyperterminal module, I was able to export and upload data got to 

various file formats: Spreadsheets, Word documents, Text file and most importantly 

in HTML format for the website. Thus with the last format I can be able to upload 

the data and it can be accessed by anyone doing analysis, research and system 

monitoring around the globe. The hyperterminal is not usually in Windows 7 & 8 

systems but only in XP operating systems thus I had to download and install the 

application 


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Figure 28: HyperTerminal 

Figure 29: XBee Database - Mozilla & Spread sheet formats 


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LUX Analysis: This project uses a light dependent resistor (LDR) as a sensor of the 

light, to track as shown in the connection above. I used the two LDRs so as to 

calibrate them against the lux meter (scale of 0 – 2000 lux). By using the Lux and the 

average LDRs outputs, the relationship between the light and the resistance is 

found. Since the tracking control system was already in place, all I had to do was 

simply get the average readings of the two LDRs and compare with the behaviour of 

the LUX meter. Thus the relationship is as shown in the figure below: 

(A number of readings for the output voltage was taken with the corresponding lux 

values and a relationship with the least resolution between them was found using 

excel program). A photo resistor or LDR is an electronic component whose 

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

to as a light-dependent resistor (LDR), photoconductor, or photocell. 

Figure 31: Lux-LDR readings in Spread sheet 


Figure 30: LDR 

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Conclusion: - Possible Errors 

1. Systematic error 

2. Inaccuracy in resistors ,in power supply 

3. Environmental error like temperature 

4. Personal error 

5. Error in the instrument used ( lux meter ,multi-meter) 

6. Random error 

7. Unknown noise 

8. Loose Connections 

9. Common grounding: This proved to be a major problem while grounding the 

system and led to impromptu readings especially with the temperature 

sensor and Zigbee nodes. The grounding essence was revealed when there 

was presence of grounding from Arduino and from D.C Power supply used to 

run the dimmer circuit in this project. 


Figure 32: Lux Analysis for the system 

64 

2012

References 

1. Stephen Karekezi, John Kimani and Albert Waudo. "Annotated Bibliography of 

Photovoltaics and Solar Water Heaters". Working Paper No. 175, 

AFREPREN/FWD, Nairobi, 1998. 

2. Tobias Jonsson, Gabriel Acquaye. 2008. Application of IEEE 802.15.4 for home 

network. THESIS WORK 2008, Electrical Engineering 

3. Stephen Karekezi and Timothy Ranja. "Renewables in Kenya". Working Paper No. 

177, AFREPREN/FWD, Nairobi, 1998. 

4. Stephen Karekezi. “The Potential of Renewable Energy Technologies in Africa”. 

Working Paper No. 273, AFREPREN/FWD, Nairobi, 2001. 18pp.Australian 

National University – http://solar.anu.edu.au/ 

5. B.L, A.K Theraja. A Textbook of Electrical Technology. Volume II. AC & DC 

Machines. Chapter 39. 

6. Dhananjay V. Gadre, NehulMalhotra. Tiny AVR Microcontroller. Projects for the 

Evil Genius. Chapter 5. (Page 129) 

7. Sollatek. Solar Street Lighting. www.sollatek.com 

8. Arduino. www.arduino-windows.com 

9. www.en.wikipedia.org/wiki/Maximum_power_point_tracking 

10. www2.tech.purdue.edu/Eet/courses/ecet483/.../L21.pdf - United State 

11. http://www.wisegeek.com/what-is-zigbee.htm 

12. Arduino. www.arduino-ArduinoXbeeShield.com , http://www.ladyada.net/ 

13. www.windsun.com/ChargeControls/ChargeCont.htm 

14. www.sollatek.com 


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APPENDIX: 

Plan of Action 

Table 4: Plan of action 

GANTT CHART 

26-Dec-2012 

26-Nov-2012 

27-Oct-2012 

27-Sep-2012 

28-Aug-2012 

29-Jul-2012 

29-Jun-2012 

30-May-2012 

30-Apr-2012 

31-Mar-2012 

1-Mar-2012 

31-Jan-2012 

1-Jan-2012 

Table 5: Gantt chart 


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LM35 DATASHEET 

COMBINED SOURCE CODE 

#include // initialize the library with the numbers of LCD interface pins 

LiquidCrystal lcd(12, 11, 5, 4, 3, 2); 

int nightpin = 5; // analogue pin 5 for DAY – NIGHT switch 

int nightpin_val =0; 

int analogPin = 4; // analogue input from temperature sensor – LM35 

double val ; 

double volt,temp;// variable to store the value read 

#include // initialize the library with Servo motor 

Servo myservo; // create servo object to control a servo 

int leftLDR=2; 

int rightLDR=3; 

int leftLDR_value=0; // variable to store the value read 

int rightLDR_value=0; 

int controlpin=6; 

int servov=0; 

int swpin6v = 22; // switching system 

int swpin8v = 24; 



int voltage_in=0; //Analog pin for charger controller 

int voltage_out=1;//Analog pin 


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int LED1=40; // Digitalpin 

int LED2=42; // Digital pin 

int charge_enable=44; // Digital pin 

int x; 

int y; 

int chon = 5000; // charge on time 

int choff = 2000; // charge off time 

int CP = 389; // CP: Charge Point sets the battery charge voltage level. Vary from 346 - 410. 

void setup() 

{ 

Serial.begin(9600); 

pinMode(controlpin, OUTPUT); 

pinMode (swpin6v, OUTPUT); 




pinMode (nightpin, INPUT); 

pinMode(LED1, OUTPUT); 

pinMode(LED2, OUTPUT); 

pinMode(charge_enable, OUTPUT); 

digitalWrite(LED1, LOW); // Global 

digitalWrite(LED2, LOW); 

digitalWrite(charge_enable, LOW); 

} 

void loop() 

{ 

nightpin_val = digitalRead(nightpin);//night =1 

Serial.println(nightpin_val); 

if(nightpin_val==0 )//if daytime 

{ 

int i=0;//initiate for timing 

do { // necessary for running two systems simultaneously with delay 

myservo.attach(9); 

leftLDR_value=analogRead(leftLDR); 

rightLDR_value=analogRead(rightLDR); 

Serial.print("left LDR reading="); 

Serial.println(leftLDR_value); //printing of vaues to serial monitor 

Serial.print("right LDR reading="); 

Serial.println(rightLDR_value); 

//digitalWrite(controlpin, HIGH); 

if (rightLDR_value>leftLDR_value) 

{ 

servov = ++servov; 

} 

else if (rightLDR_value

myservo.write(servov); 

delay(50); //dealy for 50 ms before the next read 

i=++i; 

} while (i CP) digitalWrite(LED2, HIGH); 

else if (y y) & (y < CP) & (x > CP)) { // check input voltage and voltage on battery 

digitalWrite(charge_enable, HIGH); // turn on voltage to battery 

chon = (CP - y) * 1000; 

delay(chon); // ON wait 

digitalWrite(charge_enable, LOW); // turn off charge enable 

delay(choff); // OFF wait 

} // end if 

} 

else 

{ 

digitalWrite (swpin6v, HIGH); 

digitalWrite (swpin8v, LOW); 



delay (5000); 






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delay (5000); 





delay (5000); 





delay (5000); 





} 

} 


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