DESIGN AND CONSTRUCTION OF A SOLAR- POWERED

AUTOMATIC

STREET-LIGHTING SYSTEM

By

OKEKUNLE DAHUNSI JOHN

A Project Report submitted in the partial fulfillment

of the requirements for the degree of

Bachelor of Technology

(Electronic/Electrical Engineering)

in the Ladoke Akintola University of Technolgy, Ogbomoso, Oyo State,

Nigeria

2010

Supervised by:

Doctor Zachaeus K. Adeyemo

Engineer O. F. Oseni

© Okekunle Dahunsi John, 2010

To kind families and loyal friends.

ii

Acknowledgement

I am most grateful to God for the life, strength, diligence, and wisdom He has given

me to start and successfully complete this project work.

Much credit and deep appreciation must of necessity be given to my parents for their

financial and moral support.

My sincere gratitude goes the way of my supervisors, Dr. Z. K. Adeyemo and

Engineer O. F. Oseni for timely interventions in moments of difficulties, as well as their close

supervision and revisions. Thank you, sirs.

iii

Table of Content

Title page

Dedication……………………………………………………………………………………..ii

Acknowledgement…………..……………………………………………………………..…iii

Table of content………………………………………………………………………..……...iv

List of figures ………………………………………………………………………………..vii

Abstract…………………………………………………………………………………….viii

Chapter One

Introduction……………..……………………………………………………………………1

1.1 Preamble……...……………………………………………………………………….1

1.2 Aims and objectives……………………………………………………………….….2

1.2.1 Aims………………………………………………………….………………….……2

1.2.2 Objectives …………………………………………………………………………….2

1.3 Justification……………………………………………………………………………2

1.4 Scope of study…………………………………………………………………..……..3

Chapter Two

Literature Review ……………………………………………………………………………..4

2.1 Solar Energy……………………………………………………………………………….4

2.2 Solar panel……...……………………………………………...…………………………..5

2.3 Battery Type and Characteristics…………………………………...……………………..7

iv

2.4 Care and maintenance of Batteries………………………………………..……………….9

2.5 Operational Amplifiers…………………………………………………………………….9

2.6 Comparators…………………………………………………………………………..….12

2.7 Field Effect Transistors………………………………………………..…………………13

2.7.1 MOSFET………………………………………………………………...……………..15

Chapter Three

Design and Analysis………………………………………………………………...………..16

3.1 Solar Charging Controller Stage…………………………………………………………16

3.2 Dark Sensor Stage……………………………………………………………………..…18

3.3 The Oscillator Stage……………………………………………..……………………….21

Chapter Four

Construction and Testing…………………..………………………………………………....22

4.1 Construction…………………………………………………………………………...…22

4.2 Implementation……………………………………………………………………….….22

4.3 Soldering……………………………………………………………………………...….22

4.4 Casing and Boxing…………………………………………………...……….………….24

4.5 Testing……………………………………………………………………...…………….24

4.6 Problems Encountered…………………………………………………………...……….26

Chapter Five

v

21

Conclusions and Recommendations………..………………………………………….……28

5.1 Conclusion……………………………………………………………………...……….28

5.2 Recommendations…………………………………………………………...………….29

References …………………………………………………………………….……………30

vi

List of Figures

Fig 2.1: Picture of a typical solar panel ……………………………………………………….5

Fig 2.2: Basic op-amp………………………………………………………………………....9

Fig 2.3: Inverting constant gain amplifier ……………………………………………….........9

Fig 2.4: Unity follower…………………………………………………………………….....10

Fig 2.5: Summing amplifier………………………………………………………………….11

Fig 2.6: op-amp as a voltage comparator………………………………………………….…11

Fig 2.7: Circuit symbols of MOSFETs………………………………………………………15

Fig 3.1: Solar charging regulator…………………………………………………………..…18

Fig 3.2: Dark sensor stage……………………………………………………………………19

Fig 3.3: Light sensor……………………………………………………………………….…20

Fig 3.4: The oscillator stage of dark detector……………………………………………...…21

Fig 4.1a: Components layout on Vero-board 1………………………………………………24

Fig 4.1b: Component arrangement on Vero-board 2 ………………………………………..24

Fig 4.2: The isometric view of cased job…………………………………………………….25

Fig 4.3a: TL071 pin configuration…………………………………………………………...26

Fig 4.3b: BUZ100 pin configuration…………………………………………………………27

vii

Abstract

The scope of the project is to outline the procedures for the design and construction of

a solar powered automatic street lighting system.

A solar panel is an arrangement of photovoltaic cells in series for voltage output, (or

parallel for current output) to a dc battery. The solar power harnesses the power from the sun

during the day, and with its characteristic of photovoltaic conversion generates a voltage

which is used up in charging the battery for a later operation during the night. The amount of

charge is limited by a charger-controller circuit.

The effectiveness of the automation of the solar powered street lighting depends on a

light-detecting circuit which is made up of Light-Dependent Resistors (LDRs), Integrated

Circuits (ICs), and some common electronic components like resistors, capacitors and

transistors. The light detecting circuit cuts off the supply to the illuminating lamp during the

day and switches it on when it detects darkness.

The automatic solar-powered street lighting system provides an alternate means of

powering a street light and eliminates the use of a fifth wire, thereby reducing the load on the

supply grid. In addition to these advantages, the automatic solar-powered street lighting

system reduces the risk of electric shock and does not require personnel to switch on or off.

The initial cost is however quite exorbitant and poses a major challenge to a wider spread of

use.

viii

Chapter one

Introduction

1.1 Preamble

Nature, in its complexity, has always been harnessed and used by man to solve

problem either spontaneously or gradually. Chemical elements contained in man’s

surroundings have been extracted and turned into drugs, plastic and other complex

structures. The metallic ores buried in the soil have been extracted and refined by man to

give metals of different properties which suits comfortably into different purposes, the

non-metallic materials underneath the earth surface have been uncovered by man to make

important materials like fuel (fossil) and thee most stunning of all, solid state materials,

like GaAs and Graphene.

The sun provides for us visible light that enables vision. Once again, man has risen up

not only to harness the energy possessed by the light (photon), but to find ways of

utilizing it when the sun is no more. This energy possessed by the light produced by sun

rays is called solar energy. The solar energy will be used to generate voltage level that

will be used to power bulbs on our streets. This process incorporates other components

which shall be discussed in details in the body of the project.

Nigeria a few years back had witnessed the issue of street lighting going to the falls as

inadequate maintenance and dwindling power generation has greatly affected the system.

Monitored by the Power Authority, the street lights got their supplies from the grid and

each electric street lights used a sodium pressure bulb of at least 200W, therefore electric

street lighting was substantially affecting the household power consumption; the bulky

network of wires and cables, flying and running underground in between each pole

1

employed in the construction of those lights was the reason for very high cost of

construction and maintenance of the lights. Moreover, no automatic system of switching

on or off was employed and the yellow light from has a poorer color rendition than the

white lights from LED bulbs.

The fore mentioned de merits in electric street lighting have called the attention of

communities to be shifted to solar electric lighting. Making use of solar cells or

photovoltaic cells (PV) as they may be interchangeably used, has made street lighting an

environmental system.

1.2 Aims and Objectives

1.2.1 Aim

The aim of this project is to comprehensively outline the procedures for the design

and construction of solar powered automatic street lighting system.

1.2.2 Objectives

The objectives of this project are:

1. To identify the various components, devices and processes that could suitably be

adopted for this purpose.

2. To study the characteristics of the devices to be employed.

3. To design and construct an automatic dark detector switching for the dusk-to-

dawn lighting

4. To analyze what the project will bring to the society.

1.3 Justification

In these times of heightened environmental awareness when issues like global

warming, accidents and energy conservation are burning, the energy sector is going

through a fire test! Energy loss needs to be reduced (energy loss in heat), systems giving

2

out hazardous needed to be re engineered and most importantly the energy consumed by

systems needs to be minimized. Electric street lighting is rightly regarded as an enormous

consumer of electricity, at a vast financial and environmental cost. However, because of

the safety and security benefits which result from a good lighting system, communities

everywhere are keen to implement cost effective, low power consuming and

environmental friendly lights.

The situation now is that streetlights powered by solar energy can be simply and

rapidly installed, giving the potential of many years of trustworthy use, with a minimum

of maintenance required. The solar cell converts energy received from sunlight to dc

voltage which is directly stored in a battery and a dark-detector circuit closes the dc LED

bulb to the battery when it is dark and remove it when it is dawn.

1.4 Scope of Study

The project design can be used on streets only and will therefore not incorporate the use

of sun-tracker system.

Its limitation is for use on perimeter lighting only is a function of its simplicity because

home lighting systems are more complex and expensive than the street lighting system due to

the introduction of devices like inverters and circuit breakers. Therefore the project will only

make use of a dark detector switch to control the cutting in and out of the battery since the

goal is to provide a lasting dusk-to-dawn lighting.

3

Chapter Two

Literature review

2.1 Solar Energy

Solar energy, energy directly from the sun, is one of the most important non-

conventional energy sources available for man’s use. Solar energy is incident on the earth at

the rate of about2.0 × 1015𝑘𝑊𝑕/𝑑𝑎𝑦. Nigeria is in the high solar radiation belt of the world.

It receives an annual average of about 3.5𝑘𝑊𝑕/𝑚2 a day in the coastal latitudes and about

7.0𝑘𝑊𝑕/𝑚2 a day in the far north of the country.

This is a vast amount of energy. It is clean, renewable, inexhaustible and non-

polluting. Man can harness the energy for useful purpose by means of some active and

passive devices such as flat plate connectors, concentrators, photo-thermals, photocells, etc.

Solar energy is captured by being converted to other forms of energy. This can be done either

by thermal technology or photovoltaic system. Of these alternatives, photovoltaic system has

received the most attention and development. In solar thermal technology, solar energy as

electromagnetic waves is first converted into heat energy. The heat energy may then be used

either directly as heat or converted into other forms of energy. Typical applications are in

drying, cooking, cooling etc.

In solar photovoltaic technology, the solar energy is directly converted to electricity

using semiconductor devices called solar cells. The photovoltaic technology is an internal

form of photoelectric effect, in that pairs of charge carriers (electrons and holes) are liberated

within the bulk of a semiconductor material (solar cells) by the absorption of sufficient

energetic photons. Photovoltaic systems are made up of a number of solar cells as the

smallest unit. Solar cells are made of various shapes and form different materials. Common

solar cells are circular in shape, about 0.1mm diameter. Almost all solar cells have been of

4

the p-n junction silicon variety about 250µm thick. Depending on the material used, the area

of the cell and the brightness of the sun (incident solar intensity), a typical solar cell in full

sun generates a direct voltage of about 0.45V and direct current of approximately 0.28A. This

gives a nominal power of 126W on a clean sunny day.

2.2 Solar Panels

Using solar panels is a great way to generate clean and renewable electricity to power

remote appliances, or even the average home. Solar (or photovoltaic) cells, are a very useful

way of providing electricity to remote areas (as mentioned earlier), where the use of

electricity may be important, yet the laying of high voltage cable may not be viable. The best

example of the importance of solar energy to provide electricity in remote locations can be

found on satellites. For many years, satellites have been using solar panels to catch the sun’s

rays, in order to provide power to the equipment on board.

Figure 2.1: picture of a typical solar panel

Photovoltaic cells can be aligned as an array, as shown in figure 2.1. There are many

advantages of using a solar cell array, with various panels fitted along a mounting system.

One of the main advantages is that we are able to combine various numbers of cells to

provide a greater output of electricity, and this method makes solar electricity a viable option

to power small homes and businesses.

5

The increasing efficiency of solar energy technologies means we are able to purchase and

install panels, knowing we are likely to receive an efficient way of harnessing energy from

the sun’s rays to turn into electricity for use in our homes.

It is quite possible for a household to run completely off photovoltaic electricity from the use

of solar panels, yet this is unlikely in most cases. The costs involved with supplying a whole

house with electricity from solar energy would be quite high for the average homeowner.

However, the use of solar electricity in the average home is still able to provide a substantial

amount of electricity, reducing future energy bills.

2.3 Battery Type and Characteristics

The battery being the sole energy source is a critical aspect of the design, hence a very

reliable battery charger is required to enable proper charge and discharge cycles. Though the

battery is a bought out part in every sense of it, yet selecting a good one for the solar powered

automatic street light requires a lot of technical considerations. For proper selection and

maintenance of the battery to take place, the factors affecting battery reliability have to be

considered. These include;

1. Temperature: The natural problems that cause battery ageing are strongly affected by

temperature. Manufacturing data indicates that the battery life is reduced by 10% of every

additional 100F. For this reason it is not only necessary that the solar powered automatic

street light design should be such that the batteries are kept as cool as possible at all time, but

also that a battery with wide operating temperature range should be selected.

2. Battery voltage: Batteries are made of individual cells. To make up a battery of voltage

higher than that of a cell, individual cell must be connected in series. When batteries are kept

7

on constant charge as they are in the solar powered automatic street light system, the

individual cells are charged in series. Slight manufacturing variation in battery cells can cause

some cell to take a larger percentage of charging voltage than the others. This causes

premature ageing of those cells. The series connected group of cells is only as strong as its

weakest link, so when any individual cell becomes weak the whole battery is weakened. It

has been proved that the magnitude of this ageing problem is directly related to the number of

cell in the string and therefore increases as the battery voltage increases.

3. Battery charger: The charging condition of a battery has a major effect on the battery life

span. The battery’s life span is maximized if the battery is always powered from a constant

voltage. This is because maintaining the battery under a continuous charge arrests some of

the battery’s natural ageing processes. Another important aspect of the battery is the battery

type. For use in electronic equipment, the possible choices are

(a) Nickel- Cadmium (Wet cell rechargeable battery)

(b) Sealed lead-acid battery

Nickel cell provide 1.2V, and generally available in the 100mAH – 200AH range and wok

down to 200C (and up to 45

0C). Lead- acid battery provides 2V per cell, and is generally built

to provide 1 – 20AH and work down to 650C (and up to 65

0C). Both types have relatively flat

discharge curves. Lead acid batteries have low self discharging rate and are claim to retain

two third of their charge after a quick storage at room temperature; NiCad batteries have

relatively poor charge retention, typically losing half their charge in four months.

There life span depend on their charge and discharge cycle both NiCad and lead acid

batteries claiming to be good for 250 – 1000 charge or discharge cycles (more if they are only

partially discharge each time; less if completely discharge or rapidly discharged). NiCad have

8

an overall life expectancy of 2 – 4 years if held at a constant trickle charge current, the

comparable life for sealed lead acid batteries is claimed to be 5 – 10 years.

Due to obvious fewer advantages of lead acid batteries over the NiCad in terms of ampere

hour rating, life expectance, charge retention, operating temperature and number of cells in

series for a given voltage, the sealed lead acid battery is often recommended for battery

performance.

2.4 Care and Maintenance of Batteries

For maximum performance to be achieved, the battery has to be serviced from time to

time. Servicing the battery involves;

(a) Regular check and topping of the acid level.

(b) Cleaning of corroded terminals to ensure proper contact.

(c) Charging of acid when concentration falls below average level.

(d) Ensuring that the battery voltage is appropriate to prevent over charging of the

battery.

2.5 Operational Amplifiers.

An operational amplifier, or op-amp, is a very high gain differential amplifier with

high input impedance and low output impedance. Typical uses of the operational amplifier

are to improve voltage amplitude changes (amplitude and polarity), oscillators, filter circuits

and many types of instrumentation circuits. An op-amp contains a number of differential

amplifier stages to achieve a very high voltage gain.

Figure 2.2 shows a basic op-amp with two inputs and one output as would result using a

differential amplifier input stage. Each input results in either the same or opposite polarity (or

9

phase) output, depending on whether the signal is applied to the plus (+) or the minus (-)

input, respectively.

+

-

Input 1

Input 2

Output

VCC

GND

Fig 2.2: Basic op-amp

The op-amp can be connected in a large number of circuits to provide various operating

characteristics. Most common of these circuits connections include:

Inverting amplifier

This connection provides a constant gain amplifier circuit as shown in figure 2.3.

+

-

VCC

GND

RF

R1

V1

V0 = RF × V1

R1

Fig 2.3: inverting constant gain amplifier

10

The output is obtained by multiplying the input by a fixed or constant gain, set by the input

resistance R1 and feedback resistor Rf. The output obtained is inverted from the input. The

inverting amplifier connection is more widely used because it has better frequency stability.

Unity Follower

This circuit connection as shown in figure 2.4 provides an operational amplifier with

unity (1) gain without phase or polarity reversal.

+

-

VCC

GND

R1

V1V0

Fig 2.4 unity follower

With this circuit connection the output obtained is the same polarity and magnitude as the

input.

Mathematically,

V0 =V1

Summing Amplifier

This circuit connection provides the means of algebraic summing (adding) of signals.

Figure 2.5 shows a three-input summing amplifier circuit which provides a means of adding

three voltages, each multiplied by a constant-gain factor.

11

+

-

VCC

GND

R1

V1

V0

R2

R3

V2

V3

Figure 2.5: summing amplifier.

2.6 Comparators

In electronics, a comparator is a device which compares two voltages or currents,

and switches its output to indicate which is larger. More generally, the term is used to refer to

a device that compares two items of data.

A standard op-amp can be used as a comparator as indicated in the following diagram.

VS+

VS-

V+

V-

+

-

Vout

Fig 2.6: op amp as a voltage comparator

When the non-inverting input is at a higher voltage than the inverting input, the high gain of

the op-amp causes it to output the most positive voltage it can. When the non-inverting input

drops below the inverting, the op-amp outputs the most negative voltage it can. Since the

output voltage is limited by the supply voltage, for an op-amp that uses a balanced, split

supply, (powered by ±VS) this action can be written:

12

Vout = Vs sgn (V+- V-), Where sgn(x) is the signum function.

A dedicated voltage comparator chip, like the LM339, is designed to interface directly

to digital logic (such as TTL or CMOS), since the output is a binary state, and is often used to

interface real world signals to digital circuitry. The LM339 accomplishes this with an open-

collector output. When the inverting input is higher, the output of the comparator is

connected to the negative power supply. When the non-inverting input is higher, the output is

floating (has a very high impedance to ground). With a pull-up resistor and a 0 to +5 power

supply, for instance, the output takes on the 0 or +5, and can be interfaced to TTL logic.

When comparing a noisy signal to a threshold, the comparator may switch rapidly from state

to state as the signal crosses the threshold. If this is unwanted, a Schmitt trigger can be used

to provide a cleaner output signal. It uses hysteresis to increase the switching region from a

single point to a band.

2.7 Field Effect Transistors

The field-effect transistor (FET) is a transistor that relies on an electric field to control

the shape and hence the conductivity of a 'channel' in a semiconductor material. FETs are

sometimes used as voltage-controlled resistors. The concepts related to the field effect

transistor predated those of the bipolar junction transistor (BJT). Nevertheless, FETs were

implemented only after BJTs due to the simplicity of manufacturing BJTs over FETs at the

time.

All FETs except J-FETs have four terminals, which are known as the gate, drain,

source and body/base/bulk. Compare these to the terms used for BJTs: base, collector and

emitter. BJTs and J-FETs have no body. It is common in large FETs to connect the body and

source internally to simplify design. In most applications one would connect the source to the

13

body anyway. The voltage applied between the gate and source terminals modulates the

current between the source and drain terminals. A difference between the voltages of the

source and body will change the threshold voltage. This is known as the body effect and is

used primarily in digital circuits, although it is taken into account in high precision analog

circuits. There are two 'modes' of FET: enhancement, in which a voltage applied to the gate

increases the current flow from source to drain; and depletion, in which a voltage applied

decreases the current flow from source to drain. Thus enhancement FETs are normally off,

whereas depletion FETs are normally on.

Types of field-effect transistors

The FET is simpler in concept than the bipolar transistor and can be constructed from a wide

range of materials. The channel region of any FET is either doped to produce an N-type

semiconductor, giving an "N-channel" device, or with a P-type to give a "P-channel" device.

The doping determines the polarity of gate operation. The different types of field-effect

transistors can be distinguished by the method of insulation between channel and gate:

1. The MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) utilizes an

insulator (typically SiO2).

2. The JFET (Junction Field-Effect Transistor) uses a p-n junction as the gate.

3. The MESFET (Metal-Semiconductor Field-Effect Transistor) substitutes the p-n

junction of the JFET with a Schottky barrier; used in GaAs and other III-V

semiconductor materials.

4. Using band gap engineering in a ternary semiconductor like AlGaAs gives a HEMT

(High Electron Mobility Transistor), also called an HFET (heterostructure FET). The

fully depleted wide-band-gap material forms the isolation.

14

5. The MODFET (Modulation-Doped Field Effect Transistor) uses a quantum well

structure formed by graded doping of the active region.

2.7.1 MOSFET

The metal-oxide-semiconductor field-effect transistor (MOSFET) is by far the most common

field-effect transistor in both digital and analog circuits. MOSFET is composed of a channel

of n-type or p-type semiconductor material and is accordingly called an NMOSFET or a

PMOSFET.

Circuit symbols for MOSFETS

A variety of symbols are used for the MOSFET. The basic design is generally a line for the

channel with the source and drain leaving it at right angles and then bending back into the

same direction as the channel. Sometimes a broken line is used for enhancement mode and a

solid one for depletion mode, but the awkwardness of drawing broken lines means this

distinction is often ignored. Another line is drawn parallel to the channel for the gate.

N-type

enchancement

mode

P-type

enchancement

mode

S

D

G

S

D

G

N-type depletion

mode

P-type depletion

mode

G

S

DD

S

G

Figure 2.7: circuit symbols of MOSFETS

15

Chapter Three

Design and Analysis

3.1 Solar Charging Controller

In a self-contained solar power installation that can provide electrical energy even when the

weather is bad or it’s dark outside, an energy reservoir in the form of a lead-acid battery is

indispensable. In order to prevent the battery from being discharged via the solar panel when

the terminal voltage of the panel drops below the actual level of the battery voltage, reverse

current protection is necessary. In its most rudimentary form, such a ‘solar current valve’ is

just a simple diode. A Schottky diode, which has a low forward voltage drop, is normally

used to minimize losses.

Unfortunately, the terminal voltage of a 12-V solar panel is significantly higher than its

nominal rated voltage when it is illuminated by strong sunlight, so it is not possible to avoid

exceeding the fully-charged (terminal charge) voltage of the battery using only this single

diode. If the voltage applied to the battery is too high, it produces gas, which reduces the

lifetime of the battery and can also be dangerous, since the gas is explosive. A regulator

circuit is thus necessary, in addition to the reverse-current protection diode, to limit the

terminal charge voltage of the battery to 2.30 V per cell (equivalent to 13.8 V for a 12-V

battery). The regulator circuit presented here fulfils these two tasks — reverses current

protection and voltage regulation — in an elegant manner.

In the circuit diagram of the regulator, shown in Figure 2.8, it’s easy to identify the reverse-

current protection. If the terminal voltage of the battery is higher than that of the solar panel,

the Schottky diode D3 prevents any current from flowing from the positive terminal of the

battery to the positive terminal of the solar panel, independent of the state of the rest of the

circuit. In the reverse situation, the charging current has free access to the battery. The

voltage drop across the diode is 0.43 V at a current of 3 A.

16

However, the solar panel current can also flow through D4 and T2 when transistor T2 is

switched on. The transistor is driven by the op-amp IC1, which is wired as a comparator.

Transistor T1 and potentiometer P1 provide a reference voltage, which is filtered by capacitor

C1. This voltage is set to roughly half of the terminal charge voltage of the battery. The op-

amp compares the reference voltage to the voltage at the junction of R1 and R2, which is half

of the battery voltage less the 0.6-V drop of diode D2. The exact values are shown in the

circuit diagram. If the battery voltage is less than the terminal charge voltage, the output of

the op-amp remains low and T2 is cut off. Led D1 is thus off, which indicates that the full

solar panel current is flowing into the battery. If the battery voltage rises above the terminal

charge voltage, the comparator output changes to high (D1 on) and switches on T2, so that

the output of the solar panel is short circuited. Since a solar panel represents a current source,

which can deliver only a limited current even when it is strongly illuminated by the sun, this

otherwise brutal form of shunt regulation is fully acceptable. Nevertheless, an additional

measure is used to minimize the power dissipation in T2 and D4, and thus avoid the need for

a large heat sink. This is provided by capacitor C4, which produces a brief positive feedback

pulse (lasting around 4 ms) to the op-amp whenever it changes state. This significantly

improves the switching behavior of the op-amp, so that the edges of the output signal are

distinctly steeper.

The power dissipated by an n-channel MOSFET (such as the BUZ100) is the lowest when it

is either fully on or fully cut off, or in other words when it passes either a high current or no

current at all. In the ‘analogue’ region between these two extreme states, the power

dissipation is much greater. The edges of the drive signal should therefore be as steep (and

thus as short) as possible. This is precisely what C3 achieves. When the charging current to

the battery drops due the short-circuiting of the solar panel, the battery voltage also drops

17

slightly. This causes the comparator to switch states and allow the battery to be charged

again. In practice, this means that the fuller the battery is, the faster the LED blinks.

T1

T2

BF256B

BUZ10

D3

D4

PBYR745

PBYR745

D2

1N4148

R1

150kΩ

R2150kΩ

P1

500kΩ C1

2.2µF

C2

10nFC3

100nF

C4

100µF

R3

4.7kΩ

R4

4.7kΩ

R5

100kΩ

D1

TL071

3

2

4

7

6

BATT +ve

SOLARP +ve

BATT -ve

SOLARP -ve

13.8V13.2V

11.9V1

1.4

V

6.5V

6.6V

red

Figure 3.1: Solar charging regulator.

3.2 Dark Sensor Stage

The dark sensor stage employs a light dependent resistor (LDR) to detect when the

environment is dark. The dark sensor stage is shown in figure xxx

18

R1

R2

R3

R4

R5LDR1

VR1

NE555P

D1

Q1

V+

1

3

7

2

6

8 4

Q2

C1

1kΩ

1kΩ

4.7kΩ

2.2kΩ10kΩ

4.7kΩ

100µF

BC337

BC337

Figure 3.2: Dark sensor stage

The LDR is a device which changes its resistance according to the amount of light falling on

it. In bright sunlight it has a resistance of about 100 ohms or less. In total darkness its

resistance is more than 100 kilo-ohms. The LDR acts as a variable resistor, which alters its

resistance when the level of light alters. The LDR works thus:

Brightness = Low resistance

Darkness = High resistance

R1

LDR1

1kΩ

Vout

VR11kΩ

Figure 3.3: Light sensor

19

When in bright light,

The voltage output from the dark sensor stage,

𝑉𝑜𝑢𝑡 = 𝑉𝑖𝑛 𝑅2

𝑅1 + 𝑅2

𝑉𝑖𝑛 = 12𝑉,𝑅1 = 𝑅1 + 𝐿𝐷𝑅 = 1000 + 100 = 1100Ω, R2 = 1000Ω

𝑉𝑜𝑢𝑡 = 12 × 1000

1100 + 1000

𝑉𝑜𝑢𝑡 = 5.751𝑉

Here, the transistor employed is connected in the common emitter mode to amplify and invert

the Vout. Thereby the LOW signal is fed into the logic inverter which inverts it to a HIGH.

The high input to the oscillator stage would not trigger the oscillator and the switching stage

is not powered and the street lights won’t come on.

In the dark,

The voltage output from the dark sensor stage,

𝑉𝑜𝑢𝑡 = 𝑉𝑖𝑛 𝑅2

𝑅1 + 𝑅2

𝑉𝑖𝑛 = 12𝑉,𝑅1 = 𝑅1 + 𝐿𝐷𝑅 = 1000 + 100000 = 101000Ω, R2 = 1000Ω

𝑉𝑜𝑢𝑡 = 12 × 1000

101000 + 1000

𝑉𝑜𝑢𝑡 = 0.117𝑉

Here, a HIGH signal is fed into the logic inverter which inverts it to a LOW. The low input to

the oscillator stage would trigger the oscillator and the switching stage becomes powered and

the street lights would come on.

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3.3 The Oscillator Stage

The oscillator stage is employed to provide a switching signal that biases the

transistor every time the oscillator is triggered. The oscillator stage is implemented using the

popular NE555 timer/ oscillator IC.

NE555P

V+

1

3

7

2

6

8 4

R4

10kΩ

C1

100µF

From dark

sensor stage

To transistor

switching stage4.7kΩ

R5

Fig 3.4: The oscillator stage of the dark detector.

The oscillator output a timed pulse determined by

𝑇 = 1.1𝑅𝐶𝑠

𝑤𝑕𝑒𝑟𝑒,𝑅 = 10𝑘Ω,𝐶 = 100𝜇𝐹

𝑇 = 1.1 × 10,000 × 100 × 10−6

𝑇 = 0.1 sec (𝑓𝑜𝑟 𝑓𝑎𝑠𝑡 𝑠𝑤𝑖𝑡𝑐𝑕𝑖𝑛𝑔)

The fast switching time of 0.1s is used to ensure that the lamps are continually on as long as it

is dark.

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Chapter Four

Construction and Testing

4.1 Construction

The physical realization of the project is very vital. This is where the fantasy of the whole

idea meets reality. Here the paper work is transformed into a finished hardware. After

carrying out all the paper design and analysis, the project was implemented, constructed and

tested to ensure its working ability. The construction of this project was done in three

different stages.

1. The implementation of the whole project on a solder-less experiment board (bread

board).

2. The soldering of the circuits on Vero-boards.

3. The coupling of the entire project to the casing.

4.2 Implementation

The implementation of this project was done on the breadboard. The power supply

was first derived from a bench power supply in the school electronics lab to confirm the

workability of the stages in the design before the power supply stage was soldered. The

implementation of the project on bread board was successful and it met the desired design

aims with each stage performing as designed.

4.3 Soldering

The various circuits and stages of this project were soldered in tandem to meet desired

workability of the project. The solar charge controller was first soldered before the dark

sensor stage was done. The soldering of the project was done on a Vero- board, and was

soldered on two Vero boards.

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The first Vero board contains the solar charge controller circuit and the second Vero board

contains the dark sensor stage with the relay switching stage.

Figure 4.1a -b below shows the soldering and component arrangement on the various Vero

boards.

Vero-board 1 has solar charge controller circuit.

Figure 4.1a components layout on Vero-board 1.

Vero-board2 has the dark sensor stage with the relay switching stage.

Figure 4.1b component arrangement on veroboard2.

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4.4 Casing and Boxing

The third phase of the project construction is the casing of the project. This project was

coupled to a plastic casing. The casing material being plastic designed with special

perforation and vents and also well labeled to give ecstatic value.

Figure 4.2: shows the isometric view of cased job.

4.5 Testing

Stage by stage testing was done according to the block representation on the breadboard,

before soldering of circuit commenced on Vero board.

The process of testing and implementation involved the use of some test and measuring

equipments stated below.

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1. Bench Power Supply: This was used to supply voltage to the various stages of the

circuit during the breadboard test before the power supply in the project was soldered.

Also during the soldering of the project the power supply was still used to test various

stages before they were finally soldered.

2. Oscilloscope: The oscilloscope was used to observe the ripples in the power supply

waveform and to ensure that all waveforms were correct and their frequencies

accurate.

3. Digital Multi-meter: The digital multi-meter basically measures voltage, resistance,

continuity, current, frequency, temperature and transistor 𝑕𝑓𝑒 . The process of

implementation of the design on the board required the measurement of parameters

like, voltage, continuity, current and resistance values of the components and in some

cases frequency measurement. The digital multimeter was used to check the output of

the voltage regulators used in this project.

For proper understanding of how the project operates and to allow for troubleshooting, the

pin configuration of the ICs and other active components used are shown below.

Figure 4.3a shows the pin out of the TL071, op- amp which was used at the solar charging

controller stage in this project.

8

7

6

54

3

2

1 VCC

Invert input B

Output B

Non- invert input B

Output A

Invert input A

Non- invert input A

GND

TL071

Figure 4.2a: TL071 pin configuration.

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Figure 4.3b shows the pin out of the BUZ100 which was used at the solar charging controller

stage in this project.

BUZ100

1 2 3

1 = Gate

2 = Drain

3 = source

Figure 4.3b: BUZ100pin configuration.

4.6 Problems Encountered

Like every research and practical engineering work, diverse kinds of problems are often

encountered. The problems encountered in this project and how they were solved and

maneuvered are listed below.

1. At the implementation stage of this project, the dark sensor stage was not working

properly. This problem was traced to wrong connection at the comparator stage. The

connection was corrected and the stage started working.

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Chapter Five

Conclusion and Recommendations

5.1 Conclusion

The project which is the design and construction of a solar power street light was

designed considering some factors such as economic application, design economy,

availability of components and research materials, efficiency, compatibility and portability

and also durability. The performance of the project after test met design specifications.

Also the operation is dependent on how well the soldering is done, and the positioning of

the components on the Vero-board. If poor soldering lead is used the circuit might form dry

joint early and in that case the project might fail. Also if logic elements are soldered near

components that radiate heat, overheating might occur and affect the performance of the

entire system. Other factors that might affect performance include transportation, packaging,

ventilation, quality of components, handling and usage.

The construction was done in such a way that it makes maintenance and repairs an easy task

and affordable for the user should there be any system breakdown.

The project has really exposed me to digital and practical electronics generally which is one

of the major challenges I shall meet in my field now and in future. The design of the solar

power street light involved research in both digital and power electronics.

The project was quite challenging and tedious but eventually was a success.

I wish to thank the department, my supervisor and project co-coordinator for giving

me the opportunity to do this project. However, like every aspect of engineering there is still

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room for improvements and further research on the project as suggested in the

recommendations written out in the section that follows in the paragraph below

5.2 Recommendations.

For the purpose of the future research, the project work can be improved upon. The following

areas were highlighted for this purpose.

1. The whole circuitry can be reduced by making use of integrated circuit with higher

scale of integration.

2. Moreover, it is recommended that students should be enlightened on new areas of

technology that are yet to be addressed in order to bring solution to the various

problems faced by man in his day to day activities.

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References

1. Metha, V.K (2003); Principles of Electronics, S.Chand & Company Ltd (117-205,

transistors, and general references).

2. Boylestead, R L. and Nashelsky, L.(2002); Electronics Devices and Circuit Theory,

Prince-Hall. 8th Edition.

3. Maddock, R. J and Calcutt D. M, (1994); Electronics a course for engineers, Longman

Publishers (pages 341-349, IC timers, 249-263 counters, 290-293 decoder drivers).

4. Loveday, G. (1984); Essential Electronics (pages 241-244 transistors, general

references). Pitman

5. Hill, W. and Horowitz, P. (1989) The Art of Electronics, Second Edition, U.S.A.,

Cambridge University Press.

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