april 11
TRANSCRIPT
Major Project Report 2010-2011 MPPT Based Solar Powered Home
1 Electronics Department College of Engineering, Cherthala
ABSTRACT
The development of renewable energy has been an increasingly critical topic in the 21st century
with the growing problem of global warming and other environmental issues. Solar energy is a
renewable source of energy that has the capability of providing the energy for all the activities. The
second best attractive thing is that there is no environment hazard wastes are produced as its output
compared to any other energy sources like coal and petrol.
Our project aims to electrify a small home from the energy generated by solar panels. The solar panel
converts sunlight into electrical energy and this electrical energy is stored in a battery. The energy
stored is used to light up LEDs provided in the rooms where light is needed. Even though the major
intention is lighting, the energy stored can be used to power a radio and a small LED TV. The
designing involves, solar panel, battery charge controller, battery, LED drivers and suitable for low
power applications. In order to provide maximum efficiency we are using “Maximum Power Point
Tracking”(MPPT) algorithm Technique.
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ACKNOWLEDGEMENT
We thank Almighty God whole heartedly for all the grace and blessings that he has showered
on us. Without his unseen guidance this project wouldn’t have materialized.
We express our sincere gratitude to our Principal Prof. Dr .T .K. Mani for providing the right
ambiance to carry out our project work.
We would like to extend our hearty gratitude and deep indebtedness to our project guide,
prof. Rajesh M.V, H.O.D in Electronics Engineering, for his valuable guidance and encouragement.
We wish to extend our profound thanks to all our friends and all staff members especially Mr. Suresh
Kumar T.P, Mrs. Lekshmi V.R, Ms. Manju U and Mr. George C Karamel, for their whole hearted
cooperation and valuable assistance provided for the successful completion of the project.
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TABLE OF CONTENTS
CHAPTER NO: TITLE PAGE NO:
i. ABSTRACT…………………………………………………………….1
ii. ACKNOWLEDGEMENT……………………………………………..2
iii. TABLE OF CONTENTS………………………………………………3
iv. LIST OF TABLES …….………………………………………………5
vi. LIST OF FIGURES …….……………………………………….. …..6
vii. LIST OF SYMBOL …………………………………………….…..7
1. INTRODUCTION
OBJECTIVE …………………………….………………...….7
PROBLEM SPESIFICATION/NEED OF PROJECT……….8
2. SELECTION OF TECHNOLOGY/SPECIFIC REQUIREMENT ……...9
3. FEASIBILITY STUDY……………………………………………….….12
4. SOFTWARE AND HARDWARE REQUIREMENT
5.1 SOFTWARE……………………………………………….13
5.2 HARDWARE ………………………………………….14
5. DESIGN SPECIFICATIONS
6.1 SOLAR PANEL………………………………………….20
6.2 SEPIC…………………………………………………….20
6.3 CURRENT & VOLTAGE SENSING…………………...21
6.4 GATEDRIVING CIRCUIT……………………………...21
6.5 LOAD SPECIFICATION……………………………….22
6. HARDWARE DESIGN
7.1 BLOCK DIAGRAM…………………………………….…23
7.2 CIRCUIT DIAGRAM…………………………...………...23
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7.2.1 BATTERY CHARGING CIRCUIT…………....24
7.2.2 CURRENT SENSING……………… .………...25
7.2.3 MICROCONTROLLER………………………...26
7.2.4 LED DRIVER CIRCUIT……………………….26
7. SOFTWARE DESIGN
8.1 ALGORITHM………………………….…………….27
8.2 FLOWCHART………………………….……………28
8. IMPLEMENTATION OF TECHNOLOGICAL ENVIRONMENT…...30
9. CONCLUSION
10.1TESTING AND RESULT……………………………31
10.2ENHANCEMENT……………………………………31
10.3LIMITATIONS……………………….……………...31
APPENDIX
1. COMPONENT SPECIFICATION WITH COST……………….32
2. PCB LAYOUT ……………………………………………….…34
3. REFERENCE…………………………………………………….35
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LIST OF TABLES
TITLE PAGE NO:
1. LCD PIN DISCRIPTION…………………………………………………..20
2. LOAD SPECIFICATION…………………………………………………..22
3. COMPONENT SPECIFICATION…………………………………….,……32
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LIST OF FIGURES
TITLE PAGE NO:
1. BASIC BLOCK DIGARAM…………………………………… ………….7
2. MPPT CHARACTERISTICS ………………………………………………10
3. BLOCK DIGARAM OF HARDWARE……………………………………13
4. SOLAR CELL…………………………………………………………….…13
5. VI CHARA OF SOLAR PANEL…………………………………………..14
6. 12V,7Ah BATTERY…………………………………………………………15
7. MICROCONTROLLER……………………………………………………..15
8. SEPIC CONVERTER……………………………..……………...................16
9. SEPIC ON CONDITION CIRCUIT…………………………………………17
10. SEPIC OFF CONDITION CIRCUIT……………………………………….18
11. 5V POWER SUPPLY…………………………………..……………………19
12. LCD 2X16………………………………… ………………,………………..19
13. LCD INTERFACE…………………………………………………………...20
14. DETAILED BLOCK DIAGRAM…………………………..……………….23
15. BATTERY CHARGING CIRCUIT ……………………….………………. 24
16. CURRENT SENSING……………………………………….. …………….25
17. MICROCONTROLLER…………………………………..…………………25
18. LED DRIVER………………………………………………..……………...26
19. BASIC DRIVER IC…………………………………………………………26
20. FLOW CHART………………………………………………………………29
21. PCB LAYOUT OF CHARGING CIRCUIT……………………………….34
22. PCB LAYOUT OF LED DRIVER …………………………………………34
LIST OF SYMBOLS, ABBREVATIONS & NOMENCLATURE
1. MPPT –MAXIMUM POWER POINT TRACKING
2. SEPIC- SINGLE ENDED PRIMARY INDUCTANCE CONVERTER
3. LED-LIGHT EMITTING DIODE
4. LCD-LIQUID CRISTAL DISPLAY
5. PIC-PERIFERAL INTERFACE CONTROLLER
6. PWM-PULSE WIDTH MODULATION
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Solar
Array
MPPT
Power
Supply
Vin
Iin Iout
Vout
.
CHAPTER 1:INTRODUCTION
1.1 OBJECTIVE
Our project objective is to electrify a small home using solar energy .The simplified block
diagram is shown in the figure.
FIG 1: BASIC BLOCK OF MPPT BASED SOLAR POWERED HOME
The main part of the project is the solar panel. It converts light energy to electrical energy. It
provides a dc voltage and is used to charge the battery. The output voltage of solar panel depends on
the intensity of light.
The next part of the project is a SEPIC converter. The solar panel provides a higher or a lower
voltage than the voltage required to charge up the battery. When a voltage divider is used most of the
power will be lost. When a dc-dc converter is used, the voltage can be converted to required voltage.
For converting a higher voltage to lower voltage Buck converter and for the conversion of lower to
higher voltage Boost converter is used. Consider the battery charging voltage is 14V, the panel voltage
varies from 8V to 24V with the light intensity. So a buck-boost or SEPIC converter is required. In the
SEPIC converter the input voltage is converted to higher or lower voltage by taking a feedback from
the out -put portion .The feedback is taken by measuring the output voltage.
For the charging purpose an algorithm called MPPT algorithm is implemented. It works by
measuring the various parameters like panel voltage, panel current, battery voltage and battery current.
Consider when the panel supplies 18V and the charging voltage is 14V, when the ordinary charging
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process is used, 4V of input will be lost. So by using MPPT algorithm this can be overcome by
tracking the maximum current from the panel and thus improving the efficiency.
On looking the out- put voltage, the microcontroller provides a PWM and is used for the step
up or step down process. The various loads used in the system are an LED array as light source, a
radio and dc fan .All devices works on dc voltage so we can connect directly to the battery.
1.2 PROBLEM SPECIFICATIONS/NEED OF PROJECT
The problems faced by us are our main feedback. The main problems faced by us are at first
we introduced buck convert but we are not able to provide sufficient voltage at low light intensity.
Another problem faced is on the switching of MOSFET. Switching is first done by PUSH PULL
transistor circuit but its voltage is not able to provide switching. Next problem faced is on the current
sensing circuit at first we used high side current sensor whose voltage across it is difficult to measure.
In this century we need a large amount of energy requirements but we are less in energy
sources and majorly used natural resource of energy like petroleum and coal sources are at the stage of
verdict, at this stage the renewable resources have its importance. By using solar energy we are able to
provide energy till the end of universe. Our project can provide electrical energy to a poor family
which lies on a remote place where the normal supply of electricity is difficult. Since the system has a
large life time it has only the initial buying cost and its maintenance cost is low.
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CHAPTER 2: SELECTION OF TECHNOLOGY/SPECIFIC REQUIREMENTS
2.1MPPT:
The project success depends on how efficient is the system. Here in our project when we are
going through the articles and internet we came to know about a technology called MPPT by using it
we can increase the efficiency to a higher level. Maximum Power Point Tracking, frequently referred
to as MPPT, is an electronic system that operates the Photovoltaic (PV) modules in a manner that
allows the modules to produce all the power they are capable of. MPPT is not a mechanical tracking
system that “physically moves” the modules to make them point more directly at the sun. MPPT is a
fully electronic system that varies the electrical operating point of the modules so that the modules are
able to deliver maximum available power. Additional power harvested from the modules is then made
available as increased battery charge current. MPPT can be used in conjunction with a mechanical
tracking system, but the two systems are completely different.
To understand how MPPT works, let’s first consider the operation of a conventional (non-
MPPT) charge controller. When a conventional controller is charging a discharged battery, it simply
connects the modules directly to the battery. This forces the modules to operate at battery voltage,
typically not the ideal operating voltage at which the modules are able to produce their maximum
available power. The PV Module Power/Voltage/Current graph shows the traditional Current/Voltage
curve for a typical 75W module at standard test conditions of 25°C cell temperature and 1000W/m2 of
isolation. This graph also shows PV module power delivered vs. module voltage. For the example
shown, the conventional controller simply connects the module to the battery and therefore forces the
module to operate at 12V. By forcing the 75W module to operate at 12V the conventional controller
artificially limits power production to 53W. Rather than simply connecting the module to the battery,
the patented MPPT system in a Solar Boost charge controller calculates the voltage at which the
module is able to produce maximum power. In this example the maximum power voltage of the
module (VMP) is 17V. The MPPT system then operates the modules at 17V to extract the full 75W,
regardless of present battery voltage. A high efficiency DC-to-DC power converter converts the 17V
module voltage at the controller input to battery voltage at the output. If the whole system wiring and
all was 100% efficient, battery charge current in this example would be VMODULE ¸ VBATTERY x
IMODULE, or 17V ¸ 12V x 4.45A = 6.30A. A charge current increase of 1.85A or 42% would be
achieved by harvesting module power that would have been left behind by a conventional controller
and turning it into useable charge current. But, nothing is 100% efficient and actual charge current
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increase will be somewhat lower as some power is lost in wiring, fuses, circuit breakers, and in the
Solar Boost Charge controller.
FIG 2: MPPT CHARACTERISTICS
2.2SEPIC:
We also used single ended primary inductance converter (SEPIC) to convert the varying input
voltage to desired voltage level. SEPIC has advantage compared to other converters like BUCK,
BOOST and BUCK-BOOST converter is that it can convert both low level voltage and high level
voltage to desired voltage level and it has a non inverted output. In SEPIC the output voltage can be
controlled by the PWM switching provide by the controller IC.
2.3BATTERY:
The battery used in our project is Lead acid battery. The commercially available ones contain
either 6 or 12 cells connected together. In each cell, the anode and cathode plates are arranged
alternately and kept separated by separates made of sheets of insulating material. The anode plates
and cathode plates are contacted separately to each other .In a maximum we get 2v from each such
cells. The plates of each electrode are in the form of grids made of lead ore an alloy of lead and
antimony. The cathode plates are coated with red brown lead dioxide while the anode plates are
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coated with spongy lead. The plates are kept immersed in dilute sulfuric acid (specific gravity 1.15
at 25 degree Celsius and of concentration 20% approximately).
2.4 PHOTOVOLTAIC EFFECT:
A solar cell is a semiconducting device that absorbs light and converts it into electrical energy.
The p n junction silicon cell consists of moderately p doped base substrate and a thin heavily n doped
top layer. Thin metal contacts on the surface and a plain metal layer on the back connect this
photovoltaic element to the load. If exposed to radiation, electron hole pairs are created by photons
with an energy greater than the band gap energy of the semiconductor. This is called photovoltaic
effect. The newly created charge carriers in the depletion region are separated by the existing electric
field. This leads to a forward bias of the p n junction and builds up a voltage potential called the photo
voltage. As soon as a load is connected to a cell ,this voltage will cause a current to flow through the
load.
2.5LED DRIVER:
Led driver used in our project is a step-up switching regulator, which switch the lower voltage
into a desired value. In this IC MC34063A is used for the boosting of the voltage from the battery,
which is a monolithic control circuit containing all the active function for dc to dc converters. The
device contains an internal temperature compensated reference, comparator, an oscillator with an
active peak current limit circuit, driver and an output switch.
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CHAPTER 3: FEASIBILITY STUDY
The main purpose of feasibility study is to select the best system from group of similar
systems, which will work in the environment that can be afforded. Typical criteria for feasibility of a
product are accuracy, control easiness, easiness to set up manually and its total cost, which is both its
initial cost and maintenance cost. Feasibility of our project is mainly classified into,
3.1 Technical Feasibility.
3.2 Economic Feasibility.
3.3 Operational Feasibility.
3.1 Technical Feasibility.
The tracking of maximum charging current from solar panel is based on the embedded program
written on the PIC microcontroller which can be erased and used if any correction is to made on that.
The program is written on high level language so it became ease to write program.
3.2 Economic Feasibility
The project aims mainly on poor families so it must be economically feasible. The costlier part
of our project is solar panel which will cost about 160 Rs per watt, now days the government is
providing subsidies for buying solar panels. So our project becomes economically feasible.LED array
is used for the lighting purpose so it became lifelong and efficient which will decrease the usage of
current from the battery .Hence we can use a low cost battery for the use.
3.3 Operational Feasibility
User having a minimum knowledge can set up in his house. The only thing he has to look is the
position of the solar panel. It should be placed on an unshaded region. The loads attached to battery
can be controlled by simple on off switches. Loads are automatically shut off during the time of low
voltage level in the battery. These all things make our project feasible for a common man.
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CHAPTER 4: SOFTWARE & HARDWARE REQUIRMENT
4.1 SOFTWARE:
Operating system : Windows/LINUX
Development tool : orcad, micro-c
4.2 HARDWARE
FIG 3: BLOCK DIGARAM OF HARDWARE
4.2.1 SOLARPANEL
FIG 4 : SOLAR CELL
SOLAR PANEL
CONTROLLER
SEPIC CONVERTER
BATTERY
LOAD
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Photovoltaic cells are devices that absorb sunlight and convert that solar energy into electrical
energy. Solar cells are commonly made of silicon, one of the most abundant elements on Earth. Pure
silicon, an actual poor conductor of electricity, has four outer valence electrons that form tetrahedral
crystal lattices.
When photons (sunlight) hit a solar cell, its energy frees electron-holes pairs. The electric field
will send the free electron to the N side and hole to the P side. This causes further disruption of
electrical neutrality, and if an external current path is provided, electrons will flow through the path to
their original side (the P side) to unite with holes that the electric field sent there, doing work for us
along the way. The electron flow provides the current, and the cell's electric field causes a voltage.
With both current and voltage, we have power, which is the product of the two. By wiring solar cells
in series, the voltage can be increased; or in parallel, the current. Solar cells are wired together to form
a solar panel. Solar panels can be joined to create a solar array
I-V CHARACHTERISTIC OF SOLAR PANEL
Figure below shows the typical characteristics of a solar panel. Isc is a short-circuit current that flows
through the panel when the panel is short circuited. It is the maximum current that can be obtained from
the panel. Voc is the open-circuit voltage at the terminals of the panel. Vmp and Imp are the voltage
and current values at which maximum power can be obtained from the panel. As the sunlight reduces
the maximum current (Isc) which can be obtained, the maximum current from the panel also reduces.
FIG 5: VI CHARA OF SOLAR PANEL
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4.2.2 BATTERY
In a photovoltaic power supply system, batteries are used as an energy buffer. This buffer is
necessary because the sun is not consistently available due to a variety of factors: the weather, time of
the day, and for vehicles rapidly changing insulations due to vehicle motion. Using the batteries to
store the electrical power from the solar panels in the form of chemical energy makes the generated
Energy readily available whenever it is needed, independent of the current weather
Conditions and time.
FIG 6: 12V 7Ah, BATTERY
4.2.3. CONTROLLER
PIC MICROCONTROLLER 16F873A
FIG7: MICROCONTROLLER
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The microcontroller pic16f873 is a 28 pin package. It has 35 instruction set and 5 input channel 10bit
analog to digital module. It operates in frequency of dc 20 MHz and three input output ports. The
microcontroller used to provide PWM signal to SEPIC circuit. The microcontroller also interfaced
with the LCD module and the MPPT algorithm is programmed on microcontroller.
4.2.4. SEPIC CONVERTER
Single-ended primary-inductor converter (SEPIC) is a type of DC-DC converter allowing the electrical
potential (voltage) at its output to be greater than ,less than or equal to that at its input ; the output of
the SEPIC is controlled by the duty cycle of the control transistor.
A SEPIC is a similar to a traditional buck-boost converter, but has advantages of having non-inverted
output (the output voltage is of the same polarity as the input voltage), the isolation between its input
and output (provided by a capacitor in series), and true shutdown mode: when the switch is turned off,
its output drops to 0 V.
FIG 8: SEPIC CONVERTER BASIC CIRCUIT
The schematic diagram for a basic SEPIC is shown in Figure 5. As with other switched mode
power supplies (specifically DC-to-DC converters), the SEPIC exchanges energy between the
capacitors and inductors in order to convert from one voltage to another. The amount of energy
exchanged is controlled by a switch S1, which is typically a transistor such as a MOSFET; MOSFETs
offer much higher input impedance and lower voltage drop than bipolar junction transistors (BJTs),
and do not require biasing resistors (as MOSFET switching is controlled by differences in voltage
rather than a current, as with BJTs).
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Continuous mode
A SEPIC is said to be in continuous-conduction mode ("continuous mode") if the current through the
inductor L1 never falls to zero. During a SEPIC's steady-state operation, the average voltage across
capacitor C1 (VC1) is equal to the input voltage (Vin). Because capacitor C1 blocks direct current (DC),
the average current across it (IC1) is zero, making inductor L2 the only source of load current.
Therefore, the average current through inductor L2 (IL2) is the same as the average load current and
hence independent of the input voltage. Looking at average voltages, the following can be written:
VIN = VL1 + VC1 + VL2 ( 5.1)
Because the average voltage of VC1 is equal to VIN, VL1 = −VL2. For this reason, the two inductors can
be wound on the same core. Since the voltages are the same in magnitude, their effects of the mutual
inductance will be zero, assuming the polarity of the windings is correct. Also, since the voltages are
the same in magnitude, the ripple currents from the two inductors will be equal in magnitude. The
average currents can be summed as follows:
ID1 = IL1 − IL2 (5.2)
When switch S1 is turned on, current IL1 increases and the current IL2 increases in the negative
direction. (Mathematically, it decreases due to arrow direction.) The energy to increase the current IL1
comes from the input source. Since S1 is a short while closed, and the instantaneous voltage VC1 is
approximately VIN, the voltage VL2 is approximately −VIN. Therefore, the capacitor C1 supplies the
energy to increase the magnitude of the current in IL2 and thus increase the energy stored in L2. The
easiest way to visualize this is to consider the bias voltages of the circuit in a d. c. state, then close S1.
FIG9: SEPIC ON CONDITION CIRCUIT
When switch S1 is turned off, the current IC1 becomes the same as the current IL1, since
inductors do not allow instantaneous changes in current. The current IL2 will continue in the negative
direction, in fact it never reverses direction. It can be seen from the diagram that a negative IL2 will
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add to the current IL1 to increase the current delivered to the load. Using Kirchhoff’s Current Law, it
can be shown that ID1 = IC1 - IL2. It can then be concluded, that while S1 is off, power is delivered to
the load from both L2 and L1. C1, however is being charged by L1 during this off cycle, and will in
turn recharge L2 during the on cycle.
FIG 10: SEPIC OFF CONDITION CIRCUIT
Because the potential (voltage) across capacitor C1 may reverse direction every cycle, a non-
polarized capacitor should be used. However, a polarized tantalum or electrolytic capacitor may be
used in some cases, because the potential (voltage) across capacitor C1 will not change unless the
switch is closed long enough for a half cycle of resonance with inductor L2, and by this time the
current in inductor L1 could be quite large.
The capacitor CIN is required to reduce the effects of the parasitic inductance and internal
resistance of the power supply. The boost/buck capabilities of the SEPIC are possible because of
capacitor C1 and inductor L2. Inductor L1 and switch S1 create a standard boost converter, which
generate a voltage (VS1) that is higher than VIN, whose magnitude is determined by the duty cycle of
the switch S1. Since the average voltage across C1 is VIN, the output voltage (VO) is VS1 - VIN. If VS1 is
less than double VIN, then the output voltage will be less than the input voltage. If VS1 is greater than
double VIN, then the output voltage will be greater than the input voltage.
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4.2.5.POWER SUPPLY OF MICROCONTROLLER
12V provide from battery is converted to 5V for providing Vcc for Microcontroller. Here we are
using regulator IC 7805 .
FIG 11:5V POWER SUPPLY MICROCONTROLLER
4.2.6CURRENT SENSING
The circuit is used for the low side monitoring of current .Here the voltage difference across the series
resistor is amplified and the current through it is measured with the help of microcontroller. Care
should be taken that the resistor value should be lower as possible .High resistance values cause the
power source voltage to degrade through IR loss.
4.2.7LCDMODULE
FIG 12: LCD 2X 16 DISPLAYS
This is used to display the name of the project and the parameters which we have measured.
To do so we are using a LCD panel this is HD44780U compatible series display. It can display in two
lines, each line contains 16 characters. So we can say it 16x2 matrix LCD display. It has 8 data lines
along with an R/W and RS pins. Which make it work in the either in 4 bit mode and 8 bit mode. The
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contrast of the display can be controlled by the use of the potentiometer which gives the extent of the
brightness. The voltage of the third pin of the LCD used to adjusting contrast. Here we are connected
a variable resistor P1 for adjusting voltage of the 3rd
pin. The c3 and c7 are used to reject the noise
from the supply voltage. The same LCD works as 4 bit interfacing. Here this LCD work as 8bit LCD.
So we can connect D0-D7 pins of LCD connected.
FIG 13: LCD INTERFACE
LCD PIN DESCRIPTION
Table 1 : LCD PIN DISCRIPTION
PIN SYMBOL DESCRPTION
1 Vss Ground
2 Vcc +5V power supply
3 VEE Contrast adjust
4 RS RS=0 to select command register, RS=1 to
select data register
5 R/W R/W=0 for write, R/W=1 for read
6 E Enable
7 DB0 The 8-bit data bus
8 DB1 The 8-bit data bus
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PIN SYMBOL DESCRPTION
9 DB2 The 8-bit data bus
10 DB3 The 8-bit data bus
11 DB4 The 8-bit data bus
12 DB5 The 8-bit data bus
13 DB6 The 8-bit data bus
14 DB7 The 8-bit data bus
15 VLed Supply for back LED
16 VGnd Ground for Back LED
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CHAPTER 5: DESIGN SPECIFICATION
5.1. SOLAR PANEL
“Solar panel” provides varying voltage from 8V to 24V we require the maximum power point for
charging the battery .Solar panel is supposed to provide 1A at maximum solar intensity.
5.2. SEPIC
SEPIC is used to provide a maximum current for charging the battery. The output voltage of SEPIC
depends on the switching frequency of the PWM signal. The PWM switching is provided from the
PIC microcontroller. The switching frequency is 20khz is provided.
5.3. CURRENT & VOLTAGE SENSING
The current sensing is done by taking the voltage difference across the low value resistor. The
low value resistor is used in the range of .1ohms .The voltage across the low value resistor is provided
across the comparator IC 358. The output from the op-amp is a voltage value ranging from 0 to 5 volt.
The voltage to be sensed is taken across the voltage divider and the collected output voltage is
provided to ADC of PIC it range from 0 to 5 volt.
5.4. GATE DRIVER CIRCUIT.
The PWM from the PIC is only of 5V with this voltage the switching of the MOSFET is not
properly functioned so a transistor circuit is provide to increase the voltage level from lower value that
is from 5v to 12V in which the proper switching will be possible.
5.5. LOAD SPECIFICATION
Table 2 : LOAD USED IN OUR PROJECT
SLNO: COMPONENT SPECIFICATION CALCULATION
1 DC FAN 12V,.18A .18X4=.72A
2 RADIO 12V,.29A .29X1=.29
3 LED 3V,20mA .02X5=.1A
4 TOTAL LOAD CONSUMPTION 12V 1.11A
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CHAPTER 6: HARDWARE DESIGN
6.1 CIRCUIT DIAGRAM
6.1.1 BATTERY CHARGING CIRCUIT
6.1.2 CURRENT SENSING CIRCUIT
6.1.3 MICROCONTROLLER CIRCUIT
6.1.4 LOAD DRIVING CIRCUIT
FIG 14: DETAILED BLOCK DIAGRAM
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6.1.1BATTERY CHARGING CIRCUIT
FIG 15 : BATTERY CHARGING CIRCUIT
Choose a switching frequency, fs
Calculate Duty cycle
𝐷 = (𝑉𝑜𝑢𝑡 + 𝑉𝑑) ÷ (𝑉𝑖𝑛 + 𝑉𝑜𝑢𝑡 + 𝑉𝑑) (6.1.1)
Assuming 100% efficiency, the duty cycle D for a SEPIC converter operating in
CCM is given by D
Provide 12V for gate
Capacitor design.
𝐶𝑜𝑢𝑡 ≥ (𝐼out ×D)÷(Vripple×0.5×fsw) (6.1.2)
Inductor Design
𝐿1 = 𝐿2 = 𝐿 = 𝑉𝑖𝑛 𝑚𝑖𝑛 × 𝐷𝑀𝑎𝑥 ÷ (∇𝐼𝑙 × 𝑓𝑠𝑤)
J2
Battery
12
R15
47K
R16
10K
C100.1uF/16V
PWM
CS_IN
D3
1N4148
D4
GREEN LED
R20
10K
R172.2K
D7
1N4007
Q3BC548
J1
Solar Pannel
12
R26
D1
1N4148
D2
ORANGE LED
R112.2K
L1
500uH
F1
FUSE
D5
1N4007
F2
FUSE
C1
1000uF
/35V
C2
1000uF
/35V
C40.1uF/50V
VS_PV
VBAT
U6
L7805
VIN1
VOUT3
R25
47K
R19
10K
Q2
IRFZ44
C110.1uF/16V
VBAT
VS_BT
L2
500uH
C12
470uF/25V
LS2
RELAY SPDT
35
412
D8
1N4007
+12V
Q5BC548B
R36
1K
VBAT
LOAD
J4
LOAD
12
F3FUSE
VCC
C130.1uF/50V
C6
470uF
/25V
C7
470uF
/25V
C90.1uF/50V
D6 BA159
VBAT
D12
RED LED
R35
1K
R14
0.33 OHM
Major Project Report 2010-2011 MPPT Based Solar Powered Home
25 Electronics Department College of Engineering, Cherthala
6.1.2CURRENT SENSING CIRCUIT
FIG16: CURRENT SENSING
6.1.3MICROCONTROLLER CIRCUIT
FIG 17 : MICROCONTROLLER
0
R3
10k
R4
1k
-
+
U3A
LM358
3
21
84
VCC
CS_INCS_OUT
0R23
10k
C16
0.1uF
LOAD
CS_OUT
VS_PV PWM
R22
10K
13
2
16*2 LCD Module
D0
7
D1
8
D2
9
D3
10
D4
11
D5
12
D6
13
D7
14
RS
4
R/W
5
EN
6
VCC15
GND1 CON
3VCC2
GND16
VCC
U1
PIC16F73
MCLR/VPP/THV1
RA0/AN02
RA1/AN13
RA2/AN2/VREF-4
RA3/AN3/VREF+5
RA4/T0CKI6
RA5/SS/AN47
OSC1/CLKIN9
OSC2/CLKOUT10
RC0/T1OSO/T1CKI11
RC1/T1OSI/CCP212
RC2/CCP113
RC3/SCK/SCL14
RC4/SDI/SDA15
RC5/SDO16
RC6/TX/CK17
RC7/RX/DT18
VDD20
RB0/INT21 RB122 RB223 RB3/PGM24 RB425 RB526 RB6/PGC27 RB7/PGD28
Y1
20MHz Cry stal
MCLR
C2310uF
R1810K
R24
1K
C14
22pF
C15
22pF
VCC
VCC
VS_BT
Major Project Report 2010-2011 MPPT Based Solar Powered Home
26 Electronics Department College of Engineering, Cherthala
6.1.4 LED DRIVER CIRCUIT
FIG 18: LED DRIVER
It is basically derived from a basic step-up switching regulator, which is shown in figure14 .Energy stored
in the inductor during the time that transistor Q1 is in the “on” state. Upon turn- off, the energy is transferred in
series with Vin to the output filter capacitor and load.
FIG 19: BASIC STEPUP SWITCHING REGULATOR CIRCUIT
This configuration allows the output voltage to be set to any value greater than that of the input
by the following relationship:
Vout = Vin (ton/toff) + Vin or Vout = Vin (ton/toff+1) (6.1.4)
In our project the battery provides only 12 v, but we require 24 v to light up led lamp.
For this purpose we have to convert 12 v to 24 v. so we use a boost led driver circuit for the
conversion.
J1
CON2
12R24
200K
R25
10K
U7
MC34063A
COMP5
TCAP3
VCC6
GND4
DC8
PK7
SWC1
SWE2
C15100uF/63V
L2
1mH
C10100uF/63V
R260.47 ohm
R27
220 ohm
C11220pF
D7
1N5819 / BA159
C1247uF/63V
C130.1uF
BT2
12V BATTERY
Major Project Report 2010-2011 MPPT Based Solar Powered Home
27 Electronics Department College of Engineering, Cherthala
CHAPTER 7: SOFTWARE DESIGN
7.1 ALGORITHM
1. Start
2. Initialize ports of microcontroller , LCD and PWM
3. Track
4. Measure battery voltage and battery current.
5. Display on LCD
6. If panel voltage is changed more than a threshold, track again
7. If battery voltage is less than the lower limit switch of the load.
8. If battery voltage reached maximum, turn off charging
9. Go to line 4.
Track
1. Set PWM to zero
2. Measure panel voltage, battery voltage and battery current.
3. Display on LCD
4. If panel voltage is less than limit, stop charging
5. Save the maximum charging current
6. Increase PWM
7. Continue to line 2 until maximum PWM is reached.
8. Set pwm to maximum current value.
9. Return
Major Project Report 2010-2011 MPPT Based Solar Powered Home
28 Electronics Department College of Engineering, Cherthala
7.2 FLOW CHART
yes
YES
NO
NO YES
Switch off the load
Track
Measure battery
voltage and battery
current
start
Initialize ports of microcontroller, LCD
and PWM
Stop charging
Display on LCD
If panel
voltage is >
threshold
Track
Major Project Report Solar Powered Home
MAJOR PROJECT 2010-2011
SOLAR POWERED HOME
SUBMITTED BY: GROUP 7H
S8 EC
If battery
voltage is <
lower limit
If battery
voltage is >
upper limit
Measure panel voltage and
panel current
Switch on the load
Major Project Report 2010-2011 MPPT Based Solar Powered Home
29 Electronics Department College of Engineering, Cherthala
YES
NO
NO
YES
FIG 20: FLOW CHART SOLAR POWERED HOME
Set PWM =0
Stop charging
Save the maximum charging
current
Measure panel
voltage, battery
voltage and battery
current
Display on LCD
If panel
voltage is <
lower limit
Increase PWM
If PWM
Reaches
maximum
Set PWM to
maximum current value
RETURN
Track
Major Project Report 2010-2011 MPPT Based Solar Powered Home
30 Electronics Department College of Engineering, Cherthala
CHAPTER 8: IMPLEMENTATION/ TECHNOLOGICAL DEVELOPMENT
Our project is based on the electrical requirement of a financially poor family living in a remote
place this can also been useful for middle class family during the time of power failure. Since the
amount of output current from a solar panel depends directly on the amount of light falling on it so the
solar panel should be placed on where more intensity of sun light is supposed to fall. In normal case it
is placed on the roof of the house. Radio, DC fan and LED lamp should be placed on proper place to
provide maximum output. Solar panel is having a glass cover over it so care should be given on
placing it.
The technological development should be made on the dimming of LED lamp according to
the luminous inside the room this can be provided by using suitable PWM signals. New technological
advancement in LED light can cause better future in this field. By providing maximum tracking of
current from solar panel increases the efficiency of our project, hence improvement and more studies
on this technology may end up in a great success.
Major Project Report 2010-2011 MPPT Based Solar Powered Home
31 Electronics Department College of Engineering, Cherthala
CHAPTER 9: CONCLUSION
9.1TESTING AND RESULT
The designed hardware circuitry is implemented on a PCB and the software coding is done in
very efficient and fast embedded C language. The entire implementation is checked and it proves our
effort of a great success. We believe our project is very suitable for the next generation for solving the
electrical energy requirement. The design has to be tested for checking the performance, unless the
project is tested positive, nothing has been gained by doing it.
9.2 ENHANCEMENT
We can enhance this project by introducing lens frame in front of the solar panel to concentrate
the sun light intensity. By providing a suitable heat sink for the panel we can increase the efficiency
of the system. We can use this project in motor vehicles to provide the electrical requirement.
9.3 LIMITATIONS
One of the limitation in our system is that if there is no required amount of light intensity ,that is
in rainy days we are not able to provide charging current for the battery. The surface of solar panel
should be clean to have maximum efficiency so it is less efficient in desert areas where the dust
amount is very high. In order to provide voltage to run high load applications we require a large solar
panel, that is the output voltage from a solar panel is directly proportional to its area.The initial cost is
very high for the components like solar panel and battery. The voltage drop across the current sensing
circuit may reduce the efficiency of the system. The increases in temperature of the solar panel
reduces the efficiency . Solar panel provides an appropriate voltage up to 30 degree Celsius.
Major Project Report 2010-2011 MPPT Based Solar Powered Home
32 Electronics Department College of Engineering, Cherthala
APPENDIX 1
COMPONENT SPECIFICATION WITH COST
Table 3 COMPONENTS USED
SL.NO COMPONENTS SPECIFICA
TIONS
Rupees
1 RESISTORS
R11 2.2K 0.25
R12,R14 1R 0.5
R3,R7,R5,R26,R2
3,R22,R18,R19,R1
6
10K 2.25
R4,R6,R24,R21 1K 1.0
R15,R25 47K .5
2 CAPACITORS
C17,C16 .1 µF 1
C23 10MF .5
C14,C12,C15 22PF 1.5
C-in 47MF .5
C-out 100µF .5
C12 47MF/16V .5
C11 0.1µF .5
U1 PIC
16F873A
150
U2 LM358 15
4 LCD 16x2 150
5 SOLAR PANEL 10W,0.83A 2000
6 BATTERY 7AH 665
7 MOSFET IRFZ44 15
8 DIODE BA159 8
D1,D3 IN4148 2
D2 RED LED 3
Major Project Report 2010-2011 MPPT Based Solar Powered Home
33 Electronics Department College of Engineering, Cherthala
D4 GREEN LED 3
D5,D7 IN4007 2
9 INDUCTOR
L1,L2 526 µF 16
10 WHITE LED 3V 1.25 X 40 =50
11 LED BOX 40HOLE 72
12 DC FAN 12V,.18A 26X4=104
13 RADIO 12V 120
TOTAL 3390
Major Project Report 2010-2011 MPPT Based Solar Powered Home
34 Electronics Department College of Engineering, Cherthala
APPENDIX2
PCB LAYOUT
FIG 21:PCB LAYOUT OF CHARGING CIRCUIT
FIG 22: PCB LAYOUT OF LED DRIVER
Major Project Report 2010-2011 MPPT Based Solar Powered Home
35 Electronics Department College of Engineering, Cherthala
APPENDIX 3
REFERENCES
Basic for PIC microcontrollers,Nebojsa Matic
Power electronics circuits devices and applications.
C programming for Embedded systems, Kirk Zurell
Electronics Lab Manual, K.A.Navas,first edition
PIC microcontroller and embedded system Mazidi
www.mikroelectronica.com
www.onsemi.com