Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
SIM UNIVERSITY
SCHOOL OF ELECTRONICS
Design of Single Axis Solar Tracking System
STUDENT
: FOO SEY YAU (PI NO. Q0300044)
SUPERVISOR
: MR CHANDRAN AYYANARAPPAN
PROJECT CODE : JAN09/BEHE/06
A project report submitted to SIM University
in partial fulfilment of the requirements for the degree of
Bachelor of Engineering
NOV 2009
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
ACKNOWLEDGEMENTS
This Thesis submitted as part of Final Year Project, was completed with appreciation to
the generous collaboration and support from one person. He enabled the author to learn
more than the scholastic aspects of the project and developed various skills. The author
would like to acknowledge his supervisor, Mr. Chandran for his kind assistance
throughout the year and help in defining the thesis. His recommendations and support
have provided me with valuable insights and great improvement on my project.
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Author: Foo Sey Yau Course: ENG499
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TABLE OF CONTENTS
ACKNOWLEDGMENTS
LIST OF FIGURES
LIST OF TABLES
ABSTRACT
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1. INTRODUCTION
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1.1
1.2
1.3
1.4
PROJECT OBJECTIVE
OVERALL OBJECTIVE
APPROACHES AND METHODS TO BE EMPLOYED
1.3.1 Project requirement
1.3.2 Project Planning
1.3.3 Project conclusion
SKILLS REVIEW
1.4.1 Projects targets and criteria
1.4.2 Skills identifications
2. INVESTIGATION OF PROJECT BACKGROUND
2.1 MOTIVATION FOR THE RESEARCH
2.2 PROJECT BACKGROUND
2.2.1 Properties of solar cell
2.2.2 Different types of silicon solar cells
2.3 MOTORS REVIEW
2.4 SENSORS REVIEW
2.5 POSITION OF SOLAR PANEL VERSUS POWER
3. METHODOLOGIES AND DESIGN
3.1 INTRODUCTION
3.2 HARDWARE SELECTION
3.2.1 Choice of sensors
3.2.2 Choice of motors and motor drivers
3.2.3 Choice of Microcontroller chip
3.2.4 Voltage regulation
3.2.5 Choice of Axis
3.2.6 Solar battery charger
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PI no: Q0300044
3.3 SOFTWARE SELECTION
3.3.1 Choice of programming language and compiler
3.3.2 PIC programmer
3.3.3 Programmer software
3.2.4 Outline of the system
3.2.5 Automatic alignment
3.2.6 Manual alignment
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4. DESIGN ANALYSIS
4.1 INTRODUCTION
4.2 UNEXPECTED PROBLEMS WITH THE DESIGN
4.3 RESULTS OF COMPLETED DESIGN
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5. CONCLUSION
5.1 INTRODUCTION
5.2 CONCLUSIONS REGARDING THE SYSTEM
5.3 APPLICATIONS FOR THE SYSTEM
5.4 AREAS OF FURTHER RESEARCH
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BIBLIOGRAPHY
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APPENDICES:
APPENDIX A: PIC16F84A PINOUT DESCRIPTION
APPENDIX B: UCN5804B DATASHEET
APPENDIX C: SCHEMATIC DIAGRAM
APPENDIX D: SOURCE CODE
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
LIST OF FIGURES
Figure 2.01: Single-axis solar-tracker
Figure 2.02: Double-axis solar-tracker
Figure 2.03: Full-step, bipolar drive
Figure 2.04: Half-step, Uipolar drive
Figure 3.01: Block diagram
Figure 3.02: LDR sensor
Figure 3.03: LDR setup
Figure 3.04: Stepper-Motor
Figure 3.05: Motor with circuitry
Figure 3.06: Stepper motor with limit switch
Figure 3.07: PIC16F84A
Figure 3.08: PIC16F84A external-component
Figure 3.09: LM7805 voltage regulator
Figure 3.10: LM317T
Figure 3.11: Solar-batter-charger
Figure 3.12: Diode
Figure 3.13: LED
Figure 3.14: Current-limited-solar-batter-charger
Figure 3.15: Programming
Figure 3.16: PIC-basic-Pro
Figure 3.17: Vdd/Vss
Figure 3.18: Vpp/MCLR
Figure 3.19: Clock/data
Figure 3.20: Clock/data
Figure 3.21: ICSP
Figure 3.22:JDM2-components
Figure 3.23: RS232
Figure 3.24: Complete-JDM2
Figure 3.25: JDM2-schematic
Figure 3.26: Transistor-pin-configuration
Figure 3.27: WinPic800
Figure 3.28: Real-time-programming
Figure 3.29: Flow-chart
Figure 3.30: LCD showing LDR reading
Figure 3.31: NOT-gate
Figure 3.32: AND-gate
Figure 3.33: Manual drive sequence
Figure 3.34: Pull-up-resistor
Figure 3.35: 3PDT-toggle-switch
Figure 3.36: 3PDT-connections
Figure 3.37: Toggle switch and Push button
Figure 4.01: Modular sections of system
Figure 4.02: Different-points-on-solar-panel
Figure 4.03: Chart-of-voltages-on-different-points-on-solar-panel
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
LIST OF TABLES
Table 1.1: Gantt-chart
Table 2.1: Silicon-solar-cell
Table 2.2: Voltage-received-at-various-angles-of-incident
Table 3.1: Current-Vs-Resistance
Table 3.1: DB-9 Pin-table
Table 4.1: Voltages-received-at-various-positions-on-panel
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
ABSTRACT
To develop and design of a Microcontroller Unit (MCU) based solar tracker system with
a single-axis of freedom.
Solar tracker system is a hybrid of hardware and software prototype that automatically
provides best alignment of solar panel with the sun so as to get optimum output. A
single-axis automatic controlled solar tracker to follow the position of the sun is designed
and developed. According to the direction of beam propagation of sun’s radiation the
solar tracker is able to track solar Photovoltaic (PV) panels. This complete tracking
system will consists of sensors, motor with control circuitry, MCU with control software
and PV panel mounted on chassis. This tracker can only rotate the panels from East to
West axis and vice versa. This tracker system is operated automatically through a
software programmed single chip MCU. These components that are used in the system
are easily available, which are inexpensive and its simple design with its optimum solar
output collecting capability makes it even more beneficial. Therefore we can conclude
that, the solar tracking system is a flexible system which is inexpensive but high in
efficiency for trapping the sun’s incident energy.
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
1.
Introduction
1.1
PROJECT OBJECTIVE
Since the position of the sun changes both with seasons and the time of day, therefore a
solar tracker is needed so that it will detects the position where sunlight is strongest.
Solar powered equipment works best when pointed at or near the sun, meaning that we
can increase the effectiveness of a solar system by ensuring that the sun ray will always
fall perpendicular to the solar panel at any fixed position. The objective of the project
aims to design an economic software based single-axis solar tracking system using both
software and electromechanical mechanism that is software controlled.
1.2
OVERALL OBJECTIVE
Due to the depletion of fossil fuel and environmental protection issues, PV technology is
rapidly expanding as it offers safe and clean energy sources. Solar panel is the
fundamental energy conversion component of PV systems. Since the geographic
location of Singapore is near to the Equator, there is an abundance of solar energy
throughout the year. Furthermore solar energy is inexhaustible, free and non-polluting
which justifies why it is the most ideal source for generating electricity.
Literature review suggested that solar panels could achieve maximum illumination and
energy concentration if the panels are at all times perpendicular to the sun position.
However, the direction of the sunlight changes throughout the day from East to West,
direction also changes frequently with varying weather and seasons.
Conventionally, solar panels are fixed in a position to utilize the sun’s incident energy,
unable to rotate to follow the sun, hence limiting their area of exposure to the sun.
Therefore the solar energy collected by the convention solar panel is most of the time not
maximized. Understand that generating electricity by convention solar panel is inefficient,
so our overall project objective focuses on how to increase its efficiency.
To maximize the amount of sunlight falling on solar panels, we are going to design a
solar tracker system. Objective of this project is to design and develop software based
solar tracker with a single degree of freedom, achieved by using light sensor tracking
method and mechanical control system. This system is able to achieve the optimum
energy concentration and illumination and thus reduces the number of solar panels
required. Therefore, it has great significance for research and development.
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
1.3 APPROACHES AND METHODS EMPLOYED
1.3.1 PROJECT REQUIREMENT
Basically, the sun tracker that will be built has to be of moderate size and most
importantly it has to be relatively cheap. Firstly, the prototype requires solar cells panel
for the collection of solar energy. The prototype will also need 2 light sensors which will
be mounted on plastic or metal sheet about 2” apart with vertical 4” opaque barrier
between them. When the sun beam is directly perpendicular to both sensors, they will
produce the same resistance. However, once the sun moves from East to West during
the day, the vertical barrier will form a shadow that will fall on one of the light sensors. In
this case we are using Light Dependant Resistor (LDR) as the light sensor, this
imbalance will cause a difference in resistance which will be detected by a software base
MCU and in turns driving a motor to turn either clockwise or counter clockwise to
reposition the solar cells panel, so to ensure the solar panel is always perpendicular to
the sun.
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
1.3.2 PROJECT PLANNING
Gantt chart
Table1.1: Gantt-chart
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
The above Gantt chart was created to establish my project plan and also assist me in
monitoring my project progress. Due to time constraint, the schedule of this project plan
has to be followed closely for the project to progress smoothly throughout the year. In the
planning phase, it permits me to consider how long I need to focus between individual
tasks. It can be seen from the Gantt chart that individual tasks to be carried out are
arrange in order. In the monitoring phase, the Gantt chart permits me to perceive what
task should have been completed against the planed time. This will certainly help me in
managing the progress of my project such as purchasing parts, programming of
software, testing of hardware/software parts till the completion of the final year report and
project submission. Since the nature of the project is dynamic therefore the schedule
project plan must not be a rigid one. Should there be any unexpected problems; the
schedule will be amended in order to bring the project back on track.
The 3 areas which are very essential in the development of the project are research &
analysis, design & development and evaluation. All of these were carefully planned in the
Gantt chart. The research information that I gather includes online web resources,
reference book from National libraries and journals. Since this is not a funded project, all
expenses including the hardware components and software kit will be solely borne by
me. Therefore budget is another issue that I need to take into consideration.
As for the prototype requirements, I need to study and understand more from the actual
product perspectives. This can be done easier if hardware & software parts are broken
down into modular sections. Hardware parts that are match with the technical specs and
meet the cost budget will be considered. Selection of suitable software is also essential,
it must be compatible with the hardware and simple to configure.
1.3.3 PROJECT CONCLUSION
After much research and review the draft of the final project has come to an end. Low
cost, design simplicity and material readily available in market will make the project
easier with constraint time. However this is totally based on analysis and research, hard
work such as planning, trouble shooting and testing is needed in order for the end
product to work.
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
1.4 Skills Review
1.4.1 Project targets and Criteria
Below points denote the criteria that I have chosen to evaluate and follow closely
throughout the whole project:
1)
2)
3)
4)
5)
6)
To understand the fundamental principles of photovoltaic
To understand the performance and structures of different types of stepper
motors
To understand the operational principle of light sensors
To understand the structure and operation of voltage regulator
Collect data and analyze on the programme to be used
Compare different type of MCU and select the best choice
1.4.2 Skills identifications
Skills needed in this project are basically survey and analysis, hardware and circuit
design, programming, testing and trouble-shooting. During the intensive research done
on this project, I had acquired substantial knowledge regarding this field. As for the
hardware part, skills are needed in term of putting different modules of electromechanical
mechanism to work together. The skills of writing software to control the whole system is
also very critical, it enables the simplicity of the design. Troubleshooting and analytical
skills are also critical in both hardware and software.
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
2 Investigation of Project Background
2.1 Motivation for the Research
Solar energy has been used for the past few decades until now and surely in the future
especially with the depletion of the natural resources. However before it can be used as
the world’s alternative source of energy, we have to increase the efficiency of the solar
cells. There are quite a number of ways to increase the efficiency; one way is to increase
the size of the array but this is not very feasible due to their large size and weight. Other
way is to increase the performance of the cell itself either by increasing the efficiency of
the cell or by increasing the amount of the sun illumination falling on solar cell. However
for the past few decades the improvement in the efficiency of the cell has not progressed
substantially, therefore it is more beneficial and feasible to increase the amount of the
sun illumination falling on solar cell.
Below are the few methods that can be applied to increase the amount of solar energy
collect by a solar cell.
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By choosing a fixed angle panel that can gives the best energy for the day
By rotating the panel at a predetermined period distributed over the day
By a dynamic panel tracking the sun’s location using a sensory tracking system
Fix position method
This is the least efficient method among the three, as it does not take the rotation of the
sun into consideration. Since the sun keeps changing its position throughout the day
therefore sun power collect on the panel cannot be maximize.
Predetermined control method
This second method typically rotates the panels towards the sun throughout the day.
This can be done by using a programmed timer, rotating the panel at a predetermined
time distributed over the day. Although this method has improved the efficiency, there
are still some drawbacks as it does not take into consideration whereby the sun is block
by the cloud.
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
Dynamic method
The last method which is the dynamic method is apparently the best. It is a tracking
system that actually tracks the strongest position of the sun based on some sensory
input. Meaning that output of the light sensors actually gives a signal to the system,
either turning clockwise or counter clockwise depends on the location of the sun.
Generally, the dynamic method can be further classified into a few different kinds. The
two most common ones are the single-axis and double-axis solar tracking system.
Single-axis tracker is a single motor system that sets in one axis and tracks the daily
movement of the sun in the other axis. Normally, the single-axis tracker only tracks the
path of the sun from East to West and also reverse direction.
Figure2.01: Single-axis-solar-tracker (http://www.solar-tracking.com)
Advantages of single-axis:
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More stable system
Simpler mechanical system
Rotation angle can be easily adjusted
Energy needed for the mechanical movements is lesser
More economical due to lesser materials
Disadvantages of single-axis:
 Cannot rotate to all directions
 Receives slightly less energy than maximum[7]
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
The main difference between single and double-axis tracker is that the latter can tracks
the sun with varying weather and changing altitude. Usually this tracking system uses
two motors to keep the sun perpendicular to the centre of the four light detecting
sensors. The first motor is used to control the tilt of the panel, while the other motor
controls the rotation of the panel. Double-axis tracker tracks the sun both North to South
and East to West for additional sun energy.
Figure2.02: Double-axis-solar-tracker (http://www.solar-tracking.com)
Advantages of double axis:
 More robust system
 Receives maximum daytime energy.
 Can rotate to all directions
Disadvantages of double axis:
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Complex system requiring rotation to be more complicated
The adjustment of the panel involves complex mathematical algorithm
Higher material cost
Higher maintenance requirement
Life span of the system is reduced due to complex mechanical movements
Extra material is needed [7]
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
2.2 Project Background
2.2.1 Properties of solar cell
Currently, Photovoltaic (PV) cell is the most efficient method of converting solar energy
into usable resources which is the electricity. The term PV literally means light-voltage,
which is to produce electricity when exposed to light. Basically solar cell can be made-up
from a variety of semiconductor materials. Currently the most commonly used
semiconductor material is silicon. Single p-n junction silicon cell is the most popular cell
in mass manufactured with efficiency up to about 16.8% [1].
Basically the cell consists of a thin heavily n-doped top layer and a fairly p-doped base
substrate. A plain metal layer on the back and thin metal contacts on the surface connect
the photovoltaic element to the load. Then the cells will be wired either in parallel or in
series to get electrical currents and voltages.
PV effect is a process whereby light energy is converted into electrical energy by solar
cell. The process start when light is fallen on the 2-layered semiconductor material and
creates a voltage (Potential Difference) between them. Once sunlight is illuminated on
the p-n junction silicon cell, electron-hole pairs with energy greater than the
semiconductor band-gap energy will be created by the photons. The electric field will
then pushes the holes to one side and the electrons to another, thus moving the charge
carriers. The electrons can flow from the n-layer via the circuit and then back to the player if an external circuit is been attached. The charged carriers would simply collect at
the ends of the cell if there is no external circuit. [6]. Electrons will flow from the external
circuit to the rear contact of the solar cell and then back to the electric filed.
2.2.2 Different types of silicon solar cell
Generally there are a number of different types of solar cell available, the most common
types are Polycrystalline, Monocrystalline and Thin film. Comparisons of 3 different
types of silicon solar cell efficiencies are shown below. More solar cells are needed for
the same electricity output if its efficiency is lower. Efficiency here means output
electrical energy of the solar cell over the input of the light energy into the cell.
Table2.1: Silicon-soar-cell
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
2.3 Motors review
Introduction
All solar tracking systems need motor to control the position of the panel and a motor
control circuit to direct it. Below sections will discuss about various types of motors that
can be used for this kind of function.
DC motors
3 commonly used DC motors are the series motor, shunt motor, and the compound
motor. DC voltage is directly applied to the motor field winding and brushes. The field
and the armature of the motors are both shown as a coil of wire. A field resistor will be
placed in series with the field to control the speed of the motor. When DC voltage is
applied, current will flows through the field coil from the negative terminal to the positive
terminal. Finally, the current will return to the DC power source. The polarity of the
armature switch will then meets with the location of the armature's magnetic field. In
order for the armature to not lock up magnetically with the field, the switching action is
timed.
The magnetic fields will then build on each other and provide extra torque to maintain the
motor shaft rotating. When the motor’s voltage is de-energized, the magnetic fields in the
armature and the field winding will diminish and the armature shaft's speed will
eventually reduce to zero. When voltage is applied to the motor once more, this will
strengthen the magnetic fields and the armature will start to rotate again.
Servo motors
A servomotor is an assembly of a DC motor, a position-sensing device normally a
potentiometer, a gear reduction unit, and a control circuit. Its shaft can be positioned to
certain angular positions once it receives a coded signal. The servo will maintain the
angular position of the shaft so long as the coded signal exists at the input signal. The
angular position of the shaft changes once the coded signal changes.
A servo has built in control circuitry and a potentiometer which is very important. The
distance which a servo needs to travel is equivalent to the amount of power applied.
Hence if the shaft requires turning at a larger distance, the motor will run at optimum
speed. However, if it requires turning at a smaller amount, the motor will run at a slower
speed. The main disadvantage of servo motors is that it requires to be modified for
continuous rotation and also shaft encoders are needed.
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
Stepper motors
In order for the stepper motors to move in steps, pulse trains of varying polarity must first
be sent to its multiple windings. The direction of the motor is determined by the phasing
between the pulses being applied to the multiple windings while the speed of the motor is
determined by the frequency of the pulses. Therefore it is more precise control than DC
motors but requires more complex circuitry.
Permanent magnet stepper motors
There are a number of stepper motors available and the most common type is the
Permanent-Magnet stepper. It has a permanent magnet in the form of a rotor
magnetized in alternate polarity "stripes" parallel to the rotor shaft. The step size of a
given motor is entirely a function of the angular "width" of these magnetized stripes,
ranging from 7.5 to 30 degrees. The Permanent-Magnet stepper will then run into two
different wiring configurations, Unipolar and Bipolar. Unipolar drive supplies a ‘+ ‘positive
and’ –‘negative alternating magnetic flux to the windings developed from a pair of ‘+’
square waves applied to opposite ends of centre-tapped windings. Bipolar drive is
square waves alternating between ‘+’ and ‘-‘polarities. [3] [4]
Unipolar stepper motors
They are straightforward to control, able to generate stepping sequence just by using a
simple counter circuit. They normally have 6 leads, in 2 triplets, every triplet powering
up1 winding with a centre tap. However there are some with only 5 leads where the 2
"common" leads (centre taps) are connected internally. Normally Unipolar motors are
controlled by using its centre taps as a common point, to reverse coil polarity simply by
switching its drive voltage from one end of the winding to the other.
Bipolar stepper motors
They are constructed with exactly the same mechanism as used on the Unipolar. They
normally have 4 leads in 2 pairs, every pair powering up 1 winding. To rotate the motor,
we need to provide the 2 windings with a phase shifted pulse trains. They are simpler
than the Unipolar but their drive circuitry needed to reverse the polarity of each pair of
motor poles is more complicated. [5]
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
Full step drive
It provides more torque since both coils are energized concurrently. In the process the
rotor poles are attracted between the midway of the two field poles. Figure below shows
a full step bipolar drive.
Figure2.03: Full-step, bipolar drive
On the other hand, Unipolar drive will need a pair of Unipolar waveforms for each of the
above bipolar waveforms supply to the ends of a centre tapped winding. Unipolar drive
uses a less complicated and cheaper driver circuit. [4]
Half step drive
Step angle of the stepper motor geometry is reduced to a half step drive. Meaning there
will be twice as much of step pulses per revolution. Literally, half stepping offers better
degree in positioning of the motor shaft. Figure below shows a Unipolar waveforms for
half step drive. [4]
Figure2.04: Half-step, Uipolar drive
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
2.4 Sensors review
Another key module in this project is the light sensor, therefore a suitable and effective
sensor must be chosen. Light sensors are passive devices that convert light energy into
an electrical signal output. A few common types are Light Dependant Resistor (LDR), the
Phototransistor and Solar Cell.
The Light Dependant Resistor
The LDR is a resistive light sensor that varies its electrical resistance from few thousand
Ohms in the dark to only a several hundred Ohms when light falls on it. This means that
an increase in illumination causes a decrease in resistance. The most commonly use
materials for LDR is Cadmium Sulphide (Cds), since its spectral response curve very
much matches our eyes and can be controlled easily by light source from a torch.
Photo-junction Devices
Photo-junction Devices are PN-Junction light sensors made from silicon semiconductors
that can detect both visible light and infrared light. Examples of Photo-junction Devices
light sensors are Photodiode and the Phototransistor.
Photodiode
The outer casing of the Photodiode is transparent so that light can fall on the junction.
When light fall on the junction more electron pairs are formed thus causing the leakage
current to increase. Light intensity is directly proportional to Photodiode’s current
Phototransistor
Phototransistor is basically a photodiode with amplification and operates by exposing its
base region to the light source. Operations of Phototransistors are similar to Photodiodes
except that they are more sensitive and can provide current gain.
Photovoltaic Cells
Solar Cell is the most common type of photovoltaic light sensor that converts light energy
directly into electrical energy into current or voltage form. Single solar cell can be tied
together in parallel to increase its current or in series to form solar panels that increases
its output voltage. [1]
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2.5 Position of Solar Panel versus Power
By theory the maximum value of the voltage obtained from the solar panel is when the
panel is perpendicular to the sun incident ray. To prove this theory experimentally, a
static high power 1W LED light source is used to shine light onto a 15V solar panel. The
experiment was tested out in a dark room so that no other light source would affect the
results. The solar panel is positioned in a way that the angle of incidence of the light was
between 0 to 90 degrees. Below table shows the data collected for this test. By looking
at the data, it is proven that maximum voltage is obtained when the angle of incidence is
at 0 degree.
Table2.2: Voltage-received-at-various-angles-of-incident
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3 METHODOLOGIES AND DESIGN
3.1 Introduction
This proposed sun tracking system will mainly consists of two parts:
 Electromechanical mechanism
 Software
Since the aim of the project is to be cost-effective, the best solution is to use complete
software control system. By using a software control system no auxiliary translator circuit
external to the MCU is needed, hence reducing number of components used, results in
lower costs, power saving and simplicity.
The complete system can be shown in the block diagram below. Key components of the
control circuit are LDR, Stepper Motor with Driver circuits, software base MCU, Solar
Panel, and of course the Power supply. The following sections will deal with the
hardware and software design elements.
Figure3.01: Block-diagram
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3.2 Hardware selection
3.2.1 Choice of sensors
Since this project is based on a low cost simple sun tracking system, it seems
appropriate that the sensors be LDR. Even though other light sensors would have been
effective, comparatively LDR are cheaper, more reliable, easier to use and not so
sensitive towards voltage spikes.
Below are some added advantages of the LDR:
 LDR internal impedance decreases when the ambient light brightens.
 LDR have a photo-variable resistor that changes its impedance when the intensity of
light energy varies.
 LDR are easier to use since they have no polarity.
Figure3.02: LDR-sensor
The sensors are fixed on the solar panel to keep the panel perpendicular to the sun at all
times. The prototype will require 2 LDR which will be mounted on plastic or metal sheet
about 2” apart with vertical 4” opaque barrier between them. The LDR that is used has
approximately 100K resistance in complete darkness and a 500-ohms resistance when
totally saturated with light.[6] The LDR will show a resistance proportional to position of
the sun as resistance will increase when illumination is lesser. The 2 LDR sensors show
same resistance when they are both in perpendicular to the sun. If any unbalance in
resistance occurred due to changing position of sun, a signal will be send to the software
that triggers the MCU to reposition the solar panel. The figure below showing one of the
LDR been partially blocked when the sun rotates.
Figure3.03: LDR-setup sunenergyworld.blogspot.com/2006/04/knowing-sun-tracker.html
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Author: Foo Sey Yau Course: ENG499
PI no: Q0300044
3.2.2 Choice of Motor and Circuitry
As mention in section 1.3, a suitable motor is needed, therefore feasibility and the
degree of difficulty in implementation is taken into consideration. Several kinds of motors
are readily available in the market such as DC motors, Servo motors, Stepper motors
and etc. The main difference between DC motors and stepper motors is that the latter
cannot run freely by themselves. After much consideration of the above motors Unipolar
stepper motor was chosen because they are straightforward to control, able to generate
stepping sequence just by using a simple counter circuit. Stepper motors were chosen
instead of DC motors because they are better in situations where precise controlled
movement is needed. Furthermore, they also have a holding torque that produces the
highest torque at low speeds whereby servomotors do not have. It enables a stepper
motor to secure its position firmly while not moving. This is beneficial to my design
prototype as it is able to hold the solar panel in a firm position without the use of any
extra brake when it is not moving.
Figure3.04: Stepper-Motor
For the motor with circuitry, which is shown below, consists of a 12V Unipolar stepper
motor with driver (UCN5804B) that are used to turn the solar panel in steps from East to
West axis throughout the day. The software compares output differences of the LDR with
the reference value for perpendicular position with sun illumination and sends a signal to
motor driver to rotate the stepper motor. 4 external series diodes 1N4003 are used to
prevent substrate current from being sourced through the outputs.
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Figure3.05: Motor-with-circuitry http://www.avwd49.dsl.pipex.com/focusser.htm
3.2.3 Choice of Microcontroller Chip
Choosing of a suitable controller chip is the next decision to be made follow by selecting
a software control system. The chief purpose which is required of the controller chip
includes converting the analogue resistance of the 2
LDR sensors into digital values that can display on the
LCD and be compared. The controller chip not only
handles inputs from the sensors, but also outputs to the
stepper motors and inputs from the limit switches. The
stepper motor requires four data channels from the chip
to control its rotation and speed. The 2 limit switches
require two data channels to control the position of the
solar panel when in night mode and when it reaches its
position limit.
After taking consideration of all the necessary design specifications, MCU PIC16F84A
from Microchip technologies was chosen as the controller chip for this project.
PIC16F84A was a reasonable choice for this project
as this microcontroller contains:
i.
Pot function
ii.
EEPROM is 64 bytes
iii.
13 I/O pins
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iv.
RAM contains 68 bytes
v.
Reasonable price
vi.
10,000 erase/write cycles
The first four factors above had already covered the main functionality of this project.
The Pot function that is needed for converting the sensor readings from analogue to
digital, 13 I/O pins are required to handle the LCD, sensor, signals to motor and inputs
from the limit switches, further more the chip has program space sufficient for the code
files. In fact there are still quite a number of other factors that makes PIC16F84A the
most suitable choice for this project; however, the above 6 were the deciding factors.
External components
In order to get the PIC MCUs start running, some
external components of appropriate value are
connected to the MCU. Fist, the MCLR pin that is
connected to a 5V supply needs a 4.7K resistor
because if unconnected the MCU will float around.
Having the appropriate value capacitors and a good
crystal connected to the MCU is essential. The
oscillator will not start and run properly if the
capacitor values are out by too much. For
PIC16F84A, a 4MHz crystal and two 22pf (Pico
farad) ceramic disk capacitors is good enough.
Beside shows how a PIC16F84A is connected to its
external components.
3.2.4 Voltage Regulation
From the block diagram, the power supply provides power to the MCU, sensors and the
motor circuitry. A Voltage regulator LM7805 is intended to be used in this circuit
because the MCU and sensors need a constant flow of 5V supply. LM7805 is a common
solid state device that steps down DC voltage from 8V-40V down to 5V. The circuit
beside shows an unregulated supply to the input with connected ground and a regulated
5V made available at the
output which is used for
powering up the MCU. Power
filter
capacitors
are
connected to its Vcc source
to reduce voltage fluctuation
and elimination of noise.
Since the stepper motor
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requires a 12V supply for its operation, therefore this value can be used as the input
voltage to the regulator circuit. This in turns helps to maintain the number of power rails
to 2 in the design circuit. The stepper motor is robust enough running off with an
unregulated 12V supply.
3.2.5 Choice of Axis
After careful study and research, a single-axis tracking system is preferred instead of
double-axis. From a global analysis of the operational costs and potential operational
problems of each system’s configuration, we were led to conclude that a single EastWest axis tracking system presents the best overall compromise between the initial and
operating costs. [2]
3.2.6 Solar Battery Charger
To make this project more worthwhile an additional DIY solar battery charger was built
using a small 13V 100ma Photovoltaic (PV) solar panel, 10x 2000ma AA NiMH
rechargeable batteries, a voltage regulator and a zener diode. The objective is to have a
renewable power source input to the tracker circuitry, so that the tracker can traps the
maximum energy and again uses its own energy powering up the whole system.
Selecting a suitable Solar Panel is very crucial, as a rule of thumb the solar panel should
not have a current more than 10% of the charging batteries. For example, to charge a
2000ma battery, the solar panel should have a current of 200ma or lower.
The next stage is how to put all the components together to build the solar battery
charger. Firstly, the 13V solar panel which is made up of 2 smaller panels, a 5V and 7V
100ma solar panel were used. In order to produce a perfect 13V, the panels need to be
connected in series. But if the panels are connected in parallel, the current will increase
instead of the voltage.
The batteries will be charged as long as the voltage of the solar panel is greater than the
total voltage of the batteries when fully charged. Overcharged might happen if charged
too fast, causing the batteries lifetime being reduced. In order not to damage the
batteries even after they are fully charged, the charging current need to be low. To get a
right balance of charging speed, a current of around 10% of battery capacity should be
used.
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Limiting Current with an LM317T
LM317T is a voltage regulator chip that is used to regulate current with a suitable
resistor.
RESISTOR
INPUT
LM317T
OUTPUT
ADJ
Figure3.10: LM317T
LM317T can handle current up to 1.5A and usually do not have any problem with small
solar panels. By Ohm's Law, the value of the resistor needed is given as 1.25V
(LM317T’s ADJ regulated output) divided by the output current required. Since output
current of the LM317T is fixed, higher input current and voltage will cause the LM317T to
generate more heat.
Table3.1: current-Vs-resistance
The above table shows the resistor values available and the current required in an
LM317T current limiting circuit (I = current, R = resistance). From the table it can be seen
that to charge a 2000mah battery with a current of 200ma (10%), either a 6.8 or 5.6 Ohm
resistor will be more appropriate. Using a 6.8
Ohm resistor will speed up charging and increase
current while using a 5.6 Ohm resistor will slow
down charging and reduce the current.
From the right connection, a current limited solar
battery charger that will send a fixed amount of
current to the batteries was built and overcharging
is no longer an issue. To make it more ideal a
final enhancement will be to incorporate a battery
status monitor using a zener diode to turn on an
LED when the desired voltage level of the battery
is reached. [9] Every zener diode has a specified
zener voltage, an ideal way for determining
whether voltage is flowing or not is by its reverse
setting. No current will flow when the voltage in
the circuit is less than the zener voltage but if the
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voltage in the circuit is greater than the zener voltage, then the voltage drop across the
diode is equal to the zener voltage. For example, in a circuit when a reverse zener diode
is connected in series with an LED, the LED will only turn on if the circuit voltage is more
than voltage drop across the LED plus the voltage of the zener diode. [10]
In this project, 12.6V is used to indicate batteries under charge. To show that the
batteries are being charged by the renewable energy setup, an LED will turn on once the
voltage of the 12V batteries reaches 12.6V or higher. An 8.2V zener diode and an LED
with a voltage drop of 2.5V was used, therefore the total voltage drop across the LED
and the zener diode will be 10.7V. In order to prolong the life of the LED, a resistor is
used to prevent too much current getting to it. Since the voltage difference between
12.6V and 10.7V is = 1.9V, the 1.9V must be dropped across a suitable resistor with a
current lesser than 15mA. Using Ohm's Law, the resistance can be found by V/I = 1.9V /
0.015 Amps = 127 Ohms.
Cathode (Negative)
Anode (Positive)
Figure3.12: Diode
Figure3.13: LED
The figures below show the final stage of putting all the components together. Finally,
the LED of the complete battery status monitor will turn on once the charged batteries
voltage reaches 12.6V. [10]
Figure3.14: current-limited-solar-batter-charger
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3.3 Software selection
Figure3.15: Programming
Programming a MCU needs only 3 simple process steps. They are writing the code,
compiling the code and finally uploading the code into the MCU. For compiling the code,
first a compiler is needed. PICBasic pro compiler from Micro Engineering Labs is used in
this project. In addition to a compiler, a programmer kit and software are needed.
Uploading the machine code into the MCU is the job of the programmer and software.
These will be discussed in greater detail in the next few sections.
3.3.1 Choice of Programming Language and Compiler
An important issue that has to be addressed in this section is how the project will be
programmed. Using assembly or C languages are an adequate way of programming this
project but it was by no means the most efficient or easiest. In this project the system
code was developed using the Basic language. The main purpose for using Basic
language rather than assembly or C is because it has wider applicability and is more
flexible.
BASIC is designed as an easy to use language, its English-like language is much easier
to write and read than the assembly language. Another attractive feature of the Basic is
that its code size much smaller than the assembler. In other words, Basic has reduced in
debugging time, improved efficiency and thus faster development time. Last but not
least, Basic is easier to modify and understand, that is a continuing benefit in this project
for the past few months.
Below are some advantages and features of Basic language:
i.
Quicker and easier than C or assembler
ii.
Provides faster program execution and longer programs than BASIC interpreters
iii.
More user variables
iv.
Peek instruction to access any PIC MCU register from BASIC
v.
Serial speeds to 9600 baud
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vi.
In-line assembler
vii.
Can be used in DOS or Windows
The PICBasic Pro Compiler (PBPC) compiles the program source code that is saved
as text file to an equivalent machine code instruction listing that is in standard 8-bit Hex
file. The list of hexadecimal numbers that represents the Basic program is called the
machine code. The Hex file can then be programmed directly into the MCU. Once the
MCU started, its CPU will run through the programmed list of hexadecimal numbers.
The operation of the PBPC is as follows: First, the program source code was created
using word processor or text editor. Then choose the PIC MCU model that was used,
next, open the BASIC source code that was created for the program. The name of the
source code normally ends with .BAS extension. The BASIC source code must then be
open into the same location where the PBP.EXE file is. After all that have been done, the
PBPC can start to compile and process the file. If everything went smoothly, the
assembler will complete its task by creating an assembler source and the final code file.
However, when there is any error in the program, the compiler will issue a string of errors
that requires correction in the BASIC source file before another compile.
PBPC is a DOS command line compiler; however it can also be used in windows with
CodeDesigner. CodeDesigner is a robust visual Integrated Development Environment
(IDE) with In Circuit Debugging (ICD) capability designed specifically for PBPC. It
provides writing of code in a friendlier environment, where launching and compiling of
program can be done from the toolbar. Below figure shows the CodeDesigner converting
the Basic programme to Hex format.
Figure3.16: PIC-basic-Pro
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3.3.2 PIC Programmer
Since this is a software base MCU project it will be totally useless for a MCU without a
programmer to burn in firmware. A programmer is the key to getting firmware into a
MCU. Such device can physically connect the MCU to a PC. Programming happens
when copying of firmware from a PC into the flash memory of a MCU.
As this is a budget project, a DIY PIC programmer was built instead of buying one which
is far beyond budget costing about USD150. After spending some time on research one
suitable project was found online which is quite simple, straight forward and contains
schematic diagram. (http://www.diylife.com/2008/02/15/program-a-pic-microcontroller/).
A mere $8 SD investment had actually got this awesome programmer started. All the
parts are easily available at Sim Lim square. Each component cost less than $2; the
greatest expense was the 22uF/16 v Tantalum capacitor which cost $1.50 per piece.
Programmer connections
Prior to delving into the details of the programmer, let’s take a look at the 5 pin
connections (Vdd/Vss/Vpp/Clk/Data) which are essential for a PIC to wakeup running.
Vdd/Vss
Vss and Vdd are use by Microchip to dedicate the ground ‘-’ and positive supply ‘+’. Vss
is the ground that is always 0V while Vdd is basically a 5V positive supply (Vcc). From
the figure below C1 (0.1uf capacitor) is placed in the Vdd/Vss pins. In practice, it is
preferred to put a capacitor on every Vdd pin. C1 is called a decoupling capacitor as it
isolates the chip from any noise in the supply power. If left unchecked the noise might
create wild oscillation in the circuit.
Figure3.17: Vdd/Vss
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VPP/MCLR
Erratic behaviour or hanging of PIC might happen if there are spikes in the supply power.
To prevent this PIC has an MCLR/Master Clear and Reset function that will reset itself if
such event happens. In order for this function to work, a 10K resistor (R1) is placed
between the MCLR pin and the Vcc.
Another important function of the MCLR pin is to put the PIC into programming mode.
When Vpp is supplied from the programmer to the MCLR, the PIC opens itself for
firmware to be copied and it is not necessary to erase the PIC before programming it.
Different PIC models uses different Vpp, in this project the PIC16F84A uses a 13V Vpp.
There will be a great risk of ruining every component on the circuit board by the 13V
once the Vpp go through R1 and enter the circuit. To prevent this, a diode D1 (1n4148)
is placed between Vcc and R1, this 1-way valve is to maintain the high Vpp where it
should belongs.
Figure3.18: Vpp/MCLR
Clock and Data
Clock and data pins on the PIC are for the code to flows into. They are normally located
at pins 6 and 7 on PORTB of the PIC microcontrollers.
PIC code files are normally in .Hex extension that is represented by 1s or 0s on a disk.
From the figure below, in order to represent these bits, data is switched between ground0 and supply-1. The waveform of the clock toggles high and low again while proper
values are on the data pin. The values on the data pin (1 or 0) will be copied into the PIC
memory every time the clock pulse triggers it.
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Figure3.19: Clock/Data
To see how the PIC is programmed with Vpp, firstly the Vpp is raised to 13V in order to
put the PIC into programming mode. The data line is then changed to reflect the value of
1 or 0. Next, the clock pulse is supplied so that the PIC can copy the values of the data
pin. The Vpp will be removed once all the data has been transferred.
Figure3.20: Clock/Data
This programmer kit can connect a 5 pin connection from it to the circuit board and
allows programming of a PIC in circuit. This will eventually saves lots of time removing
chip from its sockets and also prevents subsequent bending of pins. This kind of
programming is called In-Circuit-Serial-Programming (ICSP). ICSP allows direct
download of code from a host PC to the target PIC.
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Figure3.21: ICSP
Building the JDM2
The programmer kit that was built was based on the JDM2 design. JDM2 programmer is
powered by the PC serial port (RS-232) itself and its circuit will then generate a 13V
programming voltage (Vpp), therefore no external power supply is needed.
Below are the lists of the components needed for the JDM2.
Resistors
10K ohm resistor 1/4 watt
1.5K ohm resistor 1/4 watt
Capacitors
100uf/25v electrolytic
22uF/16 v Tantalum (Tantalum is used because it requires high speed)
Diodes
8.2 volt zener diode ≥ 0.5 watt
5.1 volt zener diode ≥ 0.5 watt
4 x 1n4148 diode
Transistors
2 x BC547B
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Figure3.22: JDM2-components
The JDM2 is a great programmer but there are a few limitations in the design.
1.
In order to get a full positive 13V between Vpp and ground, it needs to use a
negative ground voltage. Any power source for the circuit need to be removed
before programming the JDM2. ( In actual practice, PIC is able to be programme
2.
3.
Not able to work well with Laptops due to their low serial port voltage.
Not able to work with a USB to serial converter due to similar reason.
with just 12.7V)
Serial port cable (DB9)
The figures below shows a DIY DB9 cable that cost only about SGD4. The pins that are
used by this connector are pin 3, 4, 5, 7 and 8. DB9 is used to supply power from PC
serial port to the JDM2. TxD and RxD are the data transmission lines while RTS, CTS,
DTR and DSR are the control lines. Voltage on the control line will be between 3 to 15V
when either one of the control signals is active.
Figure3.23: DIY-RS232
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Table3.2: DB-9 Pin-table
This picture shows the final product of the programmer kit.
Figure3.24: Complete-JDM2
The picture below shows the schematic diagram of the programmer kit.
Figure3.25: JDM2-schematic
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The pin configuration for the transistors is shown below.
Figure3.26: Transistor-pin-configuration
3.3.3 Programmer software
In order for the programmer to burn firmware to the chip we need a software
programmer. One of which that can be found online is the WinPic800. It is a PIC
microcontroller programming application for Windows that uses serial port to program the
PIC. WinPIC800 is chosen because it is free, stable, versatile and has latest updates for
the PIC chips. Below shows WinPic800 opening up the code files with .Hex extension
and burns it to the PIC.
Figure3.27: WinPic800
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Below are the steps on how to burn firmware to PIC using WinPic800
i.
ii.
iii.
iv.
v.
vi.
First connect programmer to the PIC.
Next, connect the serial port of the PC to the programmer.
Then launch the Winpic800.
Next, go to Navigate Device to check device. Winpic800 will automatically
detect the target PIC.
Next, go to Navigate File to open the Code file for the PIC that is a .hex file.
Finally, go to Device and select Program All to start copying to the PIC and
contents will be verified after finished copying.
The picture below shows the programmer interfacing with the PIC chip.
Figure3.28: Real-time-programming
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3.3.4 Outline of the System
Enabling the prototype to either run in manual or automatic mode is one of the thesis
objectives. The manual mode depends on the user input interface controlling the motor,
while the automatic mode depends on sensory input from the LDR to the MCU to track
the light. Combining these 2 modes into a single system enabled the system to run freely
in its automatic mode and also manual alignment override if any malfunction happens
with the software, sensors or MCU. The flowchart below outlines the steps that the
program will follow during operation. Refer to Appendix D for the source code.
Figure3.29: Flow-chart
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3.3.5 Automatic Alignment
The main objective of this thesis is to design an automatic solar tracker system. To
accomplish this, analogue sensors resistance need to be read into the input of the MCU.
Programmed MCU PIC16F84A from Microchip is designed to determine the optimum
position of the panel during the day .The evaluated values taken from the LDR are a
function of resistance which is converted to digital form by the MCU to control the
position of the panel.
The LDR used will have approximately 100K resistance in complete darkness and a 500ohms resistance when totally saturated with light.[6] The LDR will show a resistance
proportional to position of the sun as resistance will increase when illumination is lesser.
The 2 LDR sensors show same resistance when they are both in perpendicular to the
sun. The program was written in such a way that if any unbalance in resistance for 10
units or more, a signal will be sends to the MCU to reposition the solar panel.
An example of this will be that if LDR1 (Figure3.29) has a lower resistance reading than
LDR2, the motor will be required to rotate clockwise until both LDRs having the same
value.
Figure3.30: LCD showing LDR reading
For the motor with circuitry block, it consists of a Unipolar stepper motor with driver
(UCN5804B) that are used to turn the solar panel in steps from East to West axis
throughout the day. Half-step pattern was chosen to provide more accurate positioning
but at the expense of increasing position timing. An extra feature of the system is that if
both of the LDR reads more than 255 the system will return to the initial position and
enters into night mode. Night mode indicates that there is no more sun light to be
captured and therefore not necessary to track it. The initial position is to ensure that
whenever the sun rises, the system will always be able to track it.
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3.3.6 Manual Alignment
This prototype also incorporates a manual alignment feature that can be activated by a
9-pin 3PDT toggle switch. This manual interface that is connected to the MCU and motor
driver consists of a Manual/Auto toggle switch to switch between manual and auto mode,
a 555 timer to produce a constant pulse, and 2 push buttons (P1/P2) input signals to 2
logic gates IC (Integrate Circuit), AND (74LS08) and NOT (74LS04) gate controlling the
directions of the motor. An example of this will be that when either one of the push button
is pressed the motor driver will receive a high or low signal and subsequently rotate the
motor clockwise or counter-clockwise.
Figure3.31: NOT-gate
Figure3.32: AND-gate
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Figure3.33: Manual-drive-sequence
A pair of pull-up resistor is used, so the 2 input pin is almost 5V when both push-buttons
(P1/P2) are open, however when either of the push-button is closed, voltage drop across
the resistor will be 5V and the input pin will see a voltage that is almost 0V. The input pin
signal is then fed into the AND and OR gate shown above.
Figure3.34: Pull-up-resistor
(http://www.madsciencenotebook.com/node/4)
Figure3.35: 3PDT-toggle-switch
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Below shows the pin configuration for the 3PDT, the left column is connected to the
manual interface, the right column is connected to the MCU while the centre is
connected to the motor driver circuitry. Schematic diagram of the circuitry was drawn
using Protel in Appendix C.
Figure3.36: 3PDT-connections
Manual / Auto
Toggle switch
Push-Button
P1/P2
Figure3.37: Toggle-switch-and-Push-button
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4. DESIGN ANALYSIS
4.1
INTRODUCTION
During the design of the prototype, it is made as simple as possible so that development
and testing of prototype will be easier. It can be seen from the Gantt chart section 1.3.2
that a great amount of time was allocated for the troubleshooting of hardware/software
issues. The main reason for this planning is because development and testing of
hardware/software will not always goes on smoothly as planned. Another ingenious way
that was mention previously is to develop modular sections first, so that problems can be
located and fixed more easily. It is understandable that software control is the best
method for controlling such prototype.
Figure4.01: Modular-sections-of-system
4.2
UNEXPECTED PROBLEMS WITH THE DESIGN
The initial testing of the prototype went fairly well, however a few issues occur that need
to be addressed.
The first problem faced was during the building of the JDM2 hardware part. At that point
of time to produce the 13V for the MCLR was to no avail. After much research from the
internet, it was finally found that TD powers C2 to be 13V trough the base collector diode
of Q1. The voltage across C2 is limited by the zener D6 to be about 5.1V+8.2V = 13.3V
and hence the problem was solved.
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The next problem that needs to be addressed was during programming of the MCU.
During the programming of the MCU, the programmer keeps prompting “unable to detect
device”. It was impossible to initialise the programming without detecting the device.
Much time was spent troubleshooting for wrong connection and faulty components. The
root cause was finally found while measuring of the supply line that there was a glitch
occurring during the initialising of the programmer. The MCU itself does not consume
much of power; it was the MCU controlling devices that pull most of the current from the
power line. The main culprit was then found to be the blinking display LED that puts
enough glitch on the supply line causing the MCU momentarily to stop function properly.
After removing of the LED, the power of the supply line was once again fairly distributed.
4.3
RESULTS OF COMPLETED DESIGN
An experiment was tested out using a portable LED light source setup at various
positions above the solar panel so that data of different voltages could be collected. The
data for both the tracking and the static panel were then record down. The purpose of
this experiment was to simulate the sun at different positions and compared the outcome
between the 2 systems.
The LED light source was set up 10cm above the panel at 9 different positions (A-I). The
table and graph below shows the results of the experiment.
Figure4.02: Different-points-on-solar-panel
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Table4.1: Voltages-received-at-various-positions-on-panel
Figure4.03: Chart-of-voltages-on-different-points-on-solar-panel
It can be clearly seen from the above data that the sun-tracking system is more efficient
in receiving energy. Whereas the static system is only able to receive greatest amount of
energy when the light source is directly above (A-position), the data collected from
positions (F-I) are quite low. These sets of positions (F-I) correspond to the position of
the sun during rising and setting, so it is obvious that the static system will be less
efficient during these periods of time.
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5. CONCLUSION
5.1
INTRODUCTION
Prior to the commencement of this project a few important system specifications were
established and if adhered to, would definitely improve the overall system performance.
Below were the specifications that the system had adhered to:
I.
Track the locate of the sun via sensor input
II. Positioning of solar panel using motor and circuitry so that ray of light would
always fell perpendicular to the panel’s surface
III. System controlled by software program so to reduce the amount of hardware and
power used by the system.
Background investigation had been conducted on various sensors, motors and
positioning of solar panel so that a basic concept of the prototype could be theorised.
From then the system was developed and expanded part by part into a complete working
prototype. Upon devised, the prototype was tested alongside with a static system to
compare the amount of power received by each system.
Figure5.01: Complete-solar-tracker
5.2
CONCLUSIONS REGARDING THE SYSTEM
After comparing the results obtained from both the system, it was obvious that the
system with tracking method is more effective. The tracker system had already met all of
the required goals that had been set out. Although this prototype is not the best solar
tracker system that can be built, it is however the most efficient given the budget and
time constraints, within the context of undergraduate thesis.
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5.3
APPLICATIONS FOR THE SYSTEM
This prototype can be implemented into any application that collects energy from the sun
using stationary solar panels. Currently more and more people living in remote areas of
the world use solar energy for most of their daily requirements. To meet their needs large
solar panels are often required. Hence, using a sun-tracker will be highly beneficial in
such places, because panel size will be decreased while increasing energy received.
In household applications it will be beneficial in larger appliances such as refrigeration,
air-con and water heater system. A battery charger and a converter inside household are
required to convert power from DC to AC for appliances backup power usage.
In recent years solar water pump has gained popularity, tracking system offers better
benefits and gains which can greatly reduce system cost. Convention solar pumps
experience a disproportionate drop in performance during late afternoon and early
morning, and the centrifugal pump will not produce sufficient centrifugal force to achieve
the required lift. However by implementing the solar-tracker, daily yield can be doubled
as the pump able to run at full speed throughout a whole sunny day. [11]
5.4
AREAS OF FURTHER RESEARCH
The most practical further research in this field would be to design a more accurate and
efficient system, a new way for positioning the solar panel had to be designed. The new
design will utilise 2 motors, one is used to control tilt of the panel, while the other motor
controls the rotation of the panel. This design will allow greater freedom of movement
and accuracy compared to the current one.
END OF THESIS
(Total number of words excluding Appendices and Page I-VI= 9210 words)
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BIBLIOGRAPHY
http://www.electronics-tutorials.ws/io/io_4.html [1]
http://www.di.ubi.pt/~palmeida/Artigos/ICIIEM2005%20.pdf [2]
http://www.solarbotics.net/library/pieces/parts_mech_steppers.html [3]
http://electojects.com/motors/stepper-motors-2.htm [4]
Johnson, J., “Working with Stepper Motors”, 1998. [5]
John Iovine, “PIC Microcontroller Project Book”, 2004. [6]
http://bmf.hu/conferences/sisy2006/15_Elmer.pdf [7]
http://www.diylife.com/2008/02/15/program-a-pic-microcontroller [8]
http://www.reuk.co.uk/Solar-Battery-Charging.htm [9]
http://www.reuk.co.uk/Make-a-Simple-Battery-Status-Monitor.htm [10]
http://www.affordable-solar.com/solar.trackers.htm [11]
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APPENDICES
APPENDIX A: PIC16F84A PINOUT DESCRIPTION
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APPENDIX B: UCN5804B DATASHEET
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APPENDIX C: SCHEMATIC DIAGRAM
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APPENDIX D: SOURCE CODE
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Solar tracker system
LCD should be connected as follows:
LCD PIC
DB4 PortA.0
DB5 PortA.1
DB6 PortA.2
DB7 PortA.3
RS
PortA.4 (add 4.7K pullup resistor to 5 volts)
E
PortB.3
RW
Ground
Vdd 5 volts
Vss Ground
Vo
20K potentiometer (or ground)
DB0-3 No connect
output portb.0
output portb.4
output portb.5
input portb.6
input portb.7
LDR1 var byte
LDR2 var byte
DIFF var byte
Pause 500
' Wait 500ms for LCD to startup
loop:
low 4
Pot 1,245,LDR1
Pot 2,245,LDR2
' Read resistance from PortB Pin 1
' Read resistance from PortB Pin 2
Lcdout 254, 1
Lcdout "LDR1: ",#LDR1
' Clear LCD screen
' Display resistance from PortB Pin 1
Lcdout 254, 192
Lcdout "LDR2: ",#LDR2
Pause 500
' Display resistance from PortB Pin 2
' Wait 500ms
if LDR1 < LDR2 then lesser
if LDR1 > LDR2 then greater
if LDR1 and LDR2 > 255 then night
' If both sensor dark go to night mode
lesser:
DIFF = LDR2 - LDR1
if DIFF > 10 then L1
Goto loop
' If resistance difference 10 or more then rotate motor
' Do it forever
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greater:
DIFF = LDR1 - LDR2
if DIFF > 10 then L2
Goto loop
' If resistance difference 10 or more then rotate motor
' Do it forever
L1:
low 0
high portb.5
pulsout 4, 5000
if portb.6 = 0 then opposite
Goto loop
' Enable stepper motor
' Rotates clockwise
' Step input to stepper motor
' If reached right limit switch go to opposite
' Do it forever
L2:
low 0
low portb.5
pulsout 4, 5000
Goto loop
' Enable stepper motor
' Rotates counter-clockwise
' Step input to stepper motor
' Do it forever
opposite:
Lcdout 254, 1
Lcdout "Limit Reached"
pause 100
low 0
low portb.5
pulsout 4, 5000
if portb.7 = 0 then loop
Goto opposite
night:
Lcdout 254, 1
Lcdout "Enter Night Mode"
pause 100
Pot 1,245,LDR1
Pot 2,245,LDR2
if LDR1 and LDR2 < 200 then loop
if portb.7 = 0 then freeze
low 0
low portb.5
pulsout 4, 500
Goto night
freeze:
high portb.0
Goto night
' Clear LCD screen
' Enable stepper motor
' Rotates counter-clockwise
' Step input to stepper motor
' Continue to loop when left limit switch reached
' Clear LCD screen
' Read resistance from PortB Pin 1
' Read resistance from PortB Pin 2
' Continue to rotate until left limit switch reached
' Enable stepper motor
' Rotates counter-clockwise
' Step input to stepper motor
' Disable stepper motor
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