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Abstract
Photovoltaic or in short term PV is one of the renewable energy resources that recently has become
broader in nowadays technology. The demand or future work is looking for high efficiency, more
reliable and economical price PV charge controller which is come in portable size has become
very popular in PV system. In general, PV system consists of a PV array, charge controller,
rechargeable battery and dc load. PV charge controller is very important in PV system. In this
project, a PV Charge Controller is designed based on microcontroller (PIC 16F690) which reduced
complexity in the number of electronic components and increased monitoring and regulative
functions. This project used dc-dc buck converter circuit which has been simulated using software
of PROTEUS. Pulse width modulation (PWM) will be implemented on a PIC 16F886 to control
duty cycle, voltage and current in the PV system and is programmed using software of MPLAB.
Liquid Crystal Display (LCD) is used to display the voltage and current from rechargeable battery.
The benefit of this project is an improvement of efficiency depend on duty cycle and voltage
change.
CHAPTER 1
INTRODUCTION
1.1 Background of study
Crisis of electricity is a major problem in the present era[1]. This problem is even more critical for
a densely populated poverty corrupted developing third world country like ours. Many of our
people live here without the basic facility of electricity[2]. In some area outside the city side, there
is general electricity service called „PALLI BIDYUT‟ which can supply a very limited amount of
electricity in those area that is unable cover up the basic demand of people from those area[2]. Day
by day crisis of electricity is increasing whereas no other solution is left for us without using the
solar power or wind turbine to generate electricity. Again, not only we face electricity crisis but
also day by the cost of gas and other natural resources like fuel, diesel, petroleum etc. are rising
up that is going beyond the availably of general people. Thereby such a system that can not only
reduce the electricity crisis but also the crisis of petroleum or other natural resources for driving
vehicles is desirable[3]. We have designed a whole Central Solar Battery Charging Station
(CSBCS) along with the successful implementation of hardware and software to represent all
activities not only visually but also can be monitored and controlled from remote region.
Implementation of SBCS for also includes designing of a smart charge controller with a view to
decrease the battery charging time, making it capable of charging more than one battery at a time
and getting the desired current from the load[4].
Photovoltaic or in short term PV is one of the renewable energy resources that recently has become
broader in nowadays technology[5]. PV has many benefits especially in environmental, economic
and social[6]. In general, a PV system consists of a PV array which converts sunlight to direct-
current electricity, a control system which regulates battery charging and operation of the load[7],
energy storage in the form of secondary batteries and loads or appliances. A charge controller is
one of functional and reliable major components in PV systems. A good, solid and reliable PV
charge controller is a key component of any PV battery charging system to achieve low cost and
the benefit that user can get from it[8]. The main function of a charge controller in a PV system is
to regulate the voltage and current from PV solar panels into a rechargeable battery[9]. The
minimum function of a PV charge controller is to disconnect the array when the battery is fully
charged and keep the battery fully charged without damage[10]. A charge controller is important
to prevent battery overcharging, excessive discharging, reverse current flow at night and to protect
the life of the batteries in a PV system[7]. A power electronics circuit is used in a PV charge
controller to get highest efficiency, availability and reliability. The use of power electronics
circuits such as various dc to dc converters topologies like buck converter, boost converter, buckboost converter and others converter topology as power conditioning circuitry to provide a desired
current to charge battery effectively[11].
1.2 Motivation
Ours is a tropical country where the amount of sunlight is mostly available to meet up the demand
of producing electricity. This type of project is not new but for our country of this can be
implemented successfully for commercial purpose, it can bring a revolutionary change in the
lifestyle and the economical prospectus that also can increase the GDP of Nigeria. As ours is a
massively power-deficient country with peak power shortages of around 25%. More than 60% of
its people do not have access to the power grid. The country only produces 3500-4200 MW of
electricity against a daily demand for 4000-5200 MW on average, according to official estimates.
Solar energy is an ideal solution as it can provide griddles power and is totally clean in terms of
pollution and health hazards. Since it saves money on constructing electricity transmission lines,
it’s economical as well. The solar panel providers in Nigeria are now expecting the price of
batteries and accessories to drastically reduce. Moreover, after the current budget of 2012 the price
for per unit electricity will be amplified more. It is flattering tougher for ordinary mass to cope up
with the mounting price of per unit electricity of PDB. So, the best alternative is to development
of SBCS in our country effectively.
Considering all these we are motivated to do this project as it will help our people in several ways.
Our people are not too much efficient in monitoring. We can make use of software available too.
Through monitoring we can control our system from remote areas thereby efficiently that paves
us to do the development of software implementation thereby.
1.3 Problem Statement
Most of the PV charge controller nowadays just uses LED to indicate the operating status of the
rechargeable battery. It is hard to know the values of the rechargeable battery that have been used
such as voltage, current and others. Besides most of PV charge controller is expensive depends on
the total cost of PV system that has been used.
1.4 Aim and Objectives
The aim of this project is to design and construct a 12/24V charge controller.
1. To design a smart solar charge controller circuit
2. To design an automatic LED brightness controlling circuit according to the light intensity
of the outside atmosphere
3. Implement these designs in simulation software
4. Test the simulation results
5. Construct the above two circuits using a microcontroller on a printed board
6. Test for its functionality
1.5 Scope of Project
I.
The PV charge controller that designed in this project will be implement PIC microcontroller
in it.
II.
III.
This project concentrates on DC-DC Converter.
This project will use PIC microcontroller to control the voltage and current at certain values
that have been set which are act as input of the rechargeable battery and displays all the results
of voltage, current, power and percentage remaining rechargeable battery on the LCD.
1.6 Report Outline
This Photovoltaic Charge Controller final thesis is arranged into following chapter:
Chapter 1: Basically, is an introduction of the project. In this chapter, provides the background of
the project, objectives, scope of the project, problem statement, and also the thesis outline.
Chapter 2: Focuses on literature reviews of this project based on journals and other references.
Chapter 3: Mainly focused on methodologies for the development of Photovoltaic Charge Controller.
Details on the progress of the project are explained in this chapter.
Chapter 4: Presents the results obtained and the limitation of the project. All discussions are
concentrating on the result and performance of Photovoltaic Charge Controller.
Chapter 5: Concludes overall about the project. Obstacle faces and future recommendation are also
discussed in this chapter.
CHAPTER 2
Literature Review
2.1 Introduction
A charge controller is needed in photovoltaic system to safely charge sealed lead acid battery. The
most basic function of a charge controller is to prevent battery overcharging. If battery is allowed
to routinely overcharge, their life expectancy will be dramatically reduced. A charge controller
will sense the battery voltage, and reduce or stop the charging current when the voltage gets high
enough. This is especially important with sealed lead acid battery where we cannot replace the
water that is lost during overcharging. Unlike Wind or Hydro System charge controller, PV charge
controller can open the circuit when the battery is full without any harm to the modules. Most PV
charge controller simply opens or restricts the circuit between the battery and PV array when the
voltage rises to a set point. Then, as the battery absorbs the excess electrons and voltage begins
dropping, the controller will turn back on. Some charge controllers have these voltage points
factory-preset and nonadjustable, other controllers can be adjustable.
2.2 Theoretical Analysis
2.2.1 Solar energy:
The solar revolution of the last two decades has made solar energy an increasingly powerful force
in the energy arena. Solar Panels use arrays of solar photovoltaic cells to convert photons into
usable electricity. With solar panels, we are provided with clean, renewable energy from the sun.
Energy from the sun is caused from thermonuclear explosions deep within the sun. These
explosions fuse atoms of hydrogen into atoms of helium. A tremendous amount of energy is
released during the thermonuclear reaction and the sun releases that energy as radiation. This
radiation travels through space at the speed of light, and solar panels can make practical use of it.
Our sun generates an enormous amount of energy, and potentially, had we the technology to
harvest that sunlight with solar arrays across the solar system; we could harvest huge amounts of
energy[12].
The Earth receives 174,000 terawatts (TW) of incoming solar radiation at the upper atmosphere.
Approximately 30% is reflected back to space while the rest is absorbed by clouds, oceans and
land masses. The spectrum of solar light at the Earth's surface is mostly spread across the visible
and near-infrared ranges with a small part in the near ultraviolet. Most of the world's population
lives in areas with solar radiation levels of 150300 watts/m², or 3.5-7.0 kWh/m² per day.
The total solar energy absorbed by Earth's atmosphere, oceans and land masses is approximately
3,850,000 EJ per year. In 2002, this was more energy in one hour than the world used in one
year[13].
Figure 2.1 Average solar radiation on earth’s surface
2.2.2 Solar cell, solar panel, solar array:
A solar cell or photovoltaic cell is an electrical device that converts the energy of light
directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.
It is a form of photoelectric cell, defined as a device whose electrical characteristics, such as
current, voltage, or resistance, vary when exposed to light. Solar cells are the building blocks of
photovoltaic modules, otherwise known as solar panels. Solar cells are described as being
photovoltaic irrespective of whether the source is sunlight or an artificial light. They are used as a
photo-detector, detecting light or other electromagnetic radiation near the visible range, or
measuring light intensity. When several solar panels are working together, they can be termed as
a solar array. This is illustrated in the following figure.
Figure 2.2 solar cell, solar panel, solar array
2.2.3 Working principle of a PV cell:
A typical silicon PV cell is composed of a thin wafer consisting of an ultra-thin layer of
phosphorus-doped (N-type) silicon on top of a thicker layer of boron-doped (P-type) silicon.
Figure 2.3 Working principle of a PV cell
An electrical field is created near the top surface of the cell where these two materials are in
contact, called the P-N junction. When sunlight strikes the surface of a PV cell, this electrical field
provides momentum and direction to light-stimulated electrons, resulting in a flow of current when
the solar cell is connected to an electrical load regardless of size, a typical silicon PV cell produces
about 0.5 – 0.6 volt DC under open-circuit, no-load conditions. The current (and power) output of
a PV cell depends on its efficiency and size (surface area), and is proportional to the intensity of
sunlight striking the surface of the cell. For example, under peak sunlight conditions, a typical
commercial PV cell with a surface area of 160 cm2 (~25 in2) will produce about 2 watts peak
power. If the sunlight intensity were 40 percent of peak, this cell would produce about 0.8
watts[14].
2.2.4 PV system and its working:
PV systems are like any other electrical power generating systems; just the equipment used is
different than that used for conventional electromechanical generating systems. However, the
principles of operation and interfacing with other electrical systems remain the same, and are
guided by a well-established body of electrical codes and standards.
Although a PV array produces power when exposed to sunlight, a number of other components
are required to properly conduct, control, convert, distribute, and store the energy produced by the
array[14].
Depending on the functional and operational requirements of the system, the specific components
required may include major components such as a DC-AC power inverter, battery bank, system
and battery controller, auxiliary energy sources and sometimes the specified electrical load
(appliances). In addition, an assortment of balance of system (BOS) hardware, including wiring,
over current, surge protection and disconnect devices, and other power processing equipment.
Figure 2.1 show a basic diagram of a photovoltaic system and the relationship of individual
components[14].
Figure 2.4 Major Components of a PV system
Figure 2.5 Block diagram representation of how a PV system works
2.2.5 Why PV system requires battery?
Batteries are often used in PV systems for the purpose of storing energy produced by the PV array
during the day, and to supply it to electrical loads as needed (during the night and periods of cloudy
weather). Other reasons batteries are used in PV systems are to operate the PV array near its
maximum power point, to power electrical loads at stable voltages, and to supply surge currents to
electrical loads and inverters. In most cases, a battery charge controller is used in these systems to
protect the battery from overcharge and over-discharge[15].
2.2.6 Basics of charge controller:
A charge controller, or charge regulator is basically a voltage and/or current regulator to
keep batteries from overcharging. One of the most common problems of batteries is that they
cannot be discharged excessively or recharged too often. A charge controller controls the charge
by managing properly the battery voltage and current. It prevents overcharging and may prevent
against overvoltage, which can reduce battery performance or lifespan, and may pose a safety risk.
The terms "charge controller" or "charge regulator" may refer to either a standalone device, or to
control circuitry integrated within a battery pack, battery-powered device, or battery recharger. In
its simplest form, a charge controller’s job is to make sure the power source (such as a solar panel)
plays nice with the load (such as a battery). The simplest implementation of this is a single diode
placed in between a solar panel and a battery. This ensures that the battery does not discharge into
the solar panel at night. A more sophisticated implementation would be adding the ability for the
charge controller to disconnect the solar panel when the batteries are fully charged - in order to
prevent over-charging damage to the batteries[16].
2.2.6.1 Function of charge controller:
The main function of solar charge controller is to regulate the amount of charge coming from the
panel that flows into the battery bank in order to avoid the batteries being overcharged.
Solar charge controller has three basic functions: Overcharge protection:
It limits the energy supplied to the battery by the PV array when the battery becomes fully charge.
In a 12 V battery system the voltage varies between 10.5 volts and 14.4 volts. Battery voltage is
about 12.0 to 12.7 volts at normal full loaded condition when no charging or discharging current
is flowing. when charging current is flowing the voltages jump to a higher level e.g. 13.7 V
(depending on the current), when loads are switched on the voltage drops down to a lower lever
e.g. 12.0volts or 11.8 volts (also depending on the current). As PV panel produce large energy,
current flowing through battery can increase its voltage above 14.4 volts[17].
In this condition charge controller disconnects the battery with the solar panel.
Figure 2.6 Overcharge protection by charge controller
Over-discharge protection:
Charge controller disconnects the battery from electrical loads when the battery reaches low state
of charge. When the battery goes below 10.8 volts then the charge controller disconnects all the
loads with battery. If the battery voltage increases above 11.5 volts than the controller again
connects the loads with battery again and thus protects the battery from over discharging[17].
Figure 2.7 Over-discharge protection by charge controller
Load control functions:
A charge controller is used to maintain the proper charging voltage on the batteries. This is the
most important issue related to battery performance and life. The regulation circuit in a PV system
continuously monitors and compares the state of charge of the battery with predetermined
reference value and takes decision regarding turning on and off of the battery and charging or
trickle of charging the battery[18].
There are three types of regulation for charge controller:
a) Self-regulation
b) Shunt regulation
c) Series regulation
Self-regulation:
The principle of self-regulation is to size the photovoltaic generator so that its voltage sensitive
region coincides with the battery critical region; for example, 90-95% state of charge as shown in
Figure 2.8
Figure 2.8 Self-regulation of charge controller
If 12V lead acid battery has a charge voltage that ranges from 12.8V at 60% depth of discharge to
14.4V at full charge. The voltage operating point of the array that would transfer maximum power
from the array is 14.4V plus the voltage drop across blocking diode or a total of (14.4+0.7) =
15.1V.The PV array is thus maintained at open circuit by reverse biasing the diode until the battery
voltage falls and charging is needed once again.
Shunt regulation:
Since photovoltaic cells are current-limited by design (unlike batteries), PV modules and arrays
can be short-circuited without any harm. The ability to short-circuit modules or an array is the
basis of operation for shunt controllers. Shunt regulation is preferred in solar field. In this
regulation, the control circuitry allows the charging current (even in mA) to flow into the battery
and stop charging once the battery is fully charged. At this stage, the charging current is wasted
by converting into heat (current is passed through low-value, high-wattage resistor); this part of
the regulation dissipates a lot of heat.
Figure 2.9 Shunt regulation for charge controller
Figure 2.9 shows an electrical design of a typical shunt type controller. The shunt controller
regulates the charging of a battery from the PV array by short-circuiting the array internal to the
controller. All shunt controllers must have a blocking diode in series between the battery and the
shunt element to prevent the battery from short-circuiting when the array is regulating. Because
there is some voltage drop between the array and controller and due to wiring and resistance of the
shunt element, the array is never entirely short-circuited, resulting in some power dissipation
within the controller. For this reason, most shunt controllers require a heat sink to dissipate power,
and are generally limited to use in PV systems with array currents less than 20 amps.
Series regulation:
Series regulator works in series between the array and battery. They use some type of control or
regulation element in series between the array and the battery. While this type of controller is
commonly used in small PV systems, it is also the practical choice for larger systems due to the
current limitations of shunt controllers. Figure 2.2.5 shows a typical series type controller. In a
series controller, a relay or solid-state switch is used either opens the circuit between the array and
the battery for discontinuing charging, or limits the current in a series-linear manner to hold the
battery voltage to the high value. In the simpler series circuit design, the controller reconnects the
array to the battery once the battery falls to the array reconnect voltage set point. As these on-off
charge cycles continue, the ‘on’ time becoming shorter and shorter as the battery becomes fully
charged. Because the series controller open-circuits rather than short-circuits the array as in shunt
controllers,
Figure 2.10 Series regulation for charge controller
no blocking diode is needed to prevent the battery from short-circuiting when the controller
regulates
2.2.6.2 Charge controller set points:
Set points are the battery voltage levels at which a charge controller performs regulation and
control functions. And these are the critical parameters affecting battery life and system
performance.

Charge regulation set points protect a battery from overcharge and optimize charging.
Voltage regulation (VR)
Array voltage reconnect (AVR)

Load control set points limit allowable battery depth of discharge by disconnecting system
loads.
Low voltage disconnects (LVD)
Load reconnect voltage (LRV)
Figure 2.11 Charge controller set points
Voltage regulation (VR) set point:
The voltage regulation set point is defined as the maximum voltage that the charge controller
allows the battery to reach, limiting the overcharge of the battery. Once the controller senses that
the battery reaches the voltage regulation set point, the controller will either discontinue battery
charging or begin to regulate (limit) the amount of current delivered to the battery.
Array reconnect voltage (ARV) set point:
The battery voltage will begin to decrease when the PV module or array is disconnected from the
battery at voltage regulation set point. The rate of discharge depends on many factors such as the
charge rate prior to disconnect or the discharge rate dictated by electrical load. When the battery
voltage decreases to a predefined voltage, the array is again reconnected to the battery to resume
charging. This voltage at which the array is reconnected is defined as the array reconnect voltage
(ARV) set point.
Low voltage disconnects (LVD) set point:
If battery voltage drops too low, loads are disconnected from the battery to prevent over discharge.
This can be done using a low voltage load disconnect (LVD) device connected between the battery
and loads. A relay or solid-state switch can be used for interrupting current from battery to the
loads. The proper LVD set point will maintain good battery health while providing the maximum
available battery capacity to the system.
Load reconnect voltage (LRV) set point:
When the battery voltage rises enough, the controller allows the load to reconnect with the battery
and that level of voltage is called load reconnect voltage. At low voltage disconnect (LVD) set
point, controller disconnects the load from the battery, the battery voltage rises to its open circuit
voltage. When additional charge is provided by the array, the battery voltage rises even more. At
some point, the controller senses that the battery voltage and state of charge are high enough to
reconnect the load, called the load reconnect voltage set point.
Voltage Regulation Hysteresis (VRH):
The voltage difference between the voltage regulation set point and the array reconnect voltage is
often called the voltage regulation hysteresis (VRH). If the hysteresis is too great, the array current
remains disconnected for long periods, effectively lowering the array energy utilization and
making it very difficult to fully recharge the battery. If the regulation hysteresis is too small, the
array will cycle on and off rapidly, perhaps damaging controllers which use electro-mechanical
switching elements.
Low Voltage Load Disconnect Hysteresis (LVDH):
The voltage difference between the low voltage load disconnect set point and the load reconnect
voltage set point is called the low voltage load disconnect hysteresis (LVDH). If the LVDH is too
small, the load may cycle on and off rapidly at low battery state-of-charge (SOC), possibly
damaging the load or controller, and extending the time it takes to fully charge the battery. If the
LVDH is too large, the load may remain off for extended periods until the array fully recharges
the battery. With a large LVDH, battery health may be improved due to reduced battery cycling,
but with a reduction in load availability.
2.2.6.3 Multi stage of charge controller:
The main function of charge controller is to regulate the flow of electricity from the photovoltaic
panels to the batteries. In PV systems with batteries, the batteries must be protected from
overcharging and be maintained at fully charged state. The PV Charge Controller uses the MicroProcessor and PWM (Pulse Width Modulation) to give optimal and safe charging. Most quality
charge controller units have what is known as a 3-stage charge cycle that goes like this:
1. Bulk stage: During the Bulk phase of the charge cycle, the voltage gradually rises to the Bulk
level (usually 14.4 to 14.6 volts) while the batteries draw maximum current. When Bulk level
voltage is reached the absorption, stage begins.
2. Absorption stage: During this phase the voltage is maintained at Bulk voltage level for
specified times (usually an hour) while the current gradually tapers off as the batteries charge
up.
3. Float stage: After the absorption time passes the voltage is lowered to float level (usually 13.4
to 13.7 volts) and the batteries draw a small maintenance current until the next cycle.
Figure 2.12 Three stage of charging
2.2.7 MICRO CONTROLLER:
A microcontroller (or MU, short for microcontroller unit) is a small computer (SoC) on a single
integrated circuit (IC) containing a processor core, memory, and programmable I/O peripherals.
Program memory can be in the form of Ferroelectric RAM, NOR flash or OTP ROM in the same
chip, as well as a typically small amount of RAM. Microcontrollers are designed for embedded
applications.
Microcontrollers are used in automatically controlled products and devices, such as automobile
engine control systems, implantable medical devices, remote controls, office machines,
appliances, power tools, toys and other embedded systems. By reducing the size and cost compared
to a design that uses a separate microprocessor, memory, and input/output devices,
microcontrollers make it economical to digitally control even more devices and processes[19].
Usually a microcontroller consists of the following three parts: -
Figure 2.13 Fundamental components of a microcontroller
2.2.7.1 Basic structure of a Microcontroller:
1. CPU – Microcontrollers brain is named as CPU. CPU is the device which is employed to fetch
data, decode it and at the end complete the assigned task successfully. With the help of CPU
all the components of microcontroller are connected into a single system. Instruction fetched
by the programmable memory is decoded by the CPU.
2. Memory – In a microcontroller memory chip works same as microprocessor. Memory chip
stores all programs & data. Microcontrollers are built with certain amount of ROM or RAM
(EPROM, EEPROM, etc.) or flash memory for the storage of program source codes.
3. Input/output ports – I/O ports are basically employed to interface or drive different
appliances such as- printers, LCD’s, LED’s, etc.
4. Serial Ports – These ports give serial interfaces amid microcontroller & various other
peripherals such as parallel port.
5. Timers – A microcontroller may be in-built with one or more timer or counters. The timers &
counters control all counting & timing operations within a microcontroller. Timers are
employed to count external pulses. The main operations performed by timers are- pulse
generations, clock functions, frequency measuring, modulations, making oscillations, etc.
6. ADC (Analog to digital converter) – ADC is employed to convert analog signals to digital
ones. The input signals need to be analog for ADC. The digital signal production can be
employed for different digital applications (such as- measurement gadgets).
7. DAC (digital to analog converter) – this converter executes opposite functions that ADC
perform. This device is generally employed to supervise analog appliances like- DC motors,
etc.
8. Interpret Control - This controller is employed for giving delayed control for a working
program. The interpret can be internal or external.
9. Special Functioning Block – Some special microcontrollers manufactured for special
appliances like- space systems, robots, etc., comprise of this special function block. This
special block has additional ports so as to carry out some special operations.
Figure 2.14 Basic structure of a microcontroller
2.2.7.2 Advantages of using Microcontroller:

Low cost, small packaging

Low power consumption

Programmable, re-programmable

Lots of I/O capabilities

Easy integration with circuits

For applications where cost, power and space are critical

Single purpose
2.2.7.3 Types of Microcontroller:
Microcontrollers are divided into categories according to their memory, architecture, bits and
instruction sets. This is shown in figure2.3.7. There can be different families of microcontrollers.
Among them some of the families are discussed here8051 Microcontroller:
The most universally employed set of microcontrollers come from the 8051 family. 8051
Microcontrollers persist to be an ideal choice for a huge group of hobbyists and experts. In the
course of 8051, the humankind became eyewitness to the most ground-breaking set of
microcontrollers. The original 8051 microcontroller was initially invented by Intel.
Figure 2.15 8051 microcontroller architecture
The two other members of this 8051 family are-

8052 – This microcontroller has 3 timers & 256 bytes of RAM. Additionally, it has all the
features of the traditional 8051 microcontroller. 8051 microcontrollers are a subset of 8052
microcontroller.

8031 – This microcontroller is ROM less, other than that it has all the features of a
traditional 8051 microcontroller. For execution an external ROM of size 64K bytes can be
added to its chip.
8051 microcontroller brings into play 2 different sorts of memory such as- NV-RAM, UV-EPROM
and Flash.
PIC Microcontroller:
Peripheral Interface Controller (PIC) provided by Micro-chip Technology to categorize its solitary
chip microcontrollers. These appliances have been extremely successful in 8-bit microcontrollers.
The foremost cause behind it is that Micro-chip Technology has been constantly upgrading the
appliance architecture and included much required peripherals to the microcontroller to go well
with clientele necessities. PIC microcontrollers are very popular amid hobbyists and industrialists;
this is only cause of wide availability, low cost, large user base & serial programming
capability[20].
Figure 2.16 A PIC microcontroller IC and its architecture
AVR Microcontroller:
AVR also known as Advanced Virtual RISC, is a customized Harvard architecture 8-bit RISC
solitary chip micro-controller. It was invented in the year 1966 by Atmel. Harvard architecture
signifies that program & data are amassed in different spaces and are used simultaneously. It was
one of the foremost micro-controller families to employ on-chip flash memory basically for storing
program, as contrasting to one-time programmable EPROM, EEPROM or ROM, utilized by other
micro-controllers at the same time. Flash memory is a non-volatile (constant on power down)
programmable memory[20].
Figure 2.17 AVR microcontroller and its architecture
ARM Microcontroller:
ARM is the name of a company that designs micro-processors architecture. It is also engaged in
licensing them to the producers who fabricate genuine chips. In actuality ARM is a 32-bit genuine
RISC architecture. It was initially developed in the year 1980 by Acorn Computers Ltd. This ARM
base microprocessor does not have on-board flash memory. ARM is particularly designed for
micro-controller devices, it is simple to be trained and make use of, however powerful enough for
the most challenging embedded devices. It has 32-bit ARM instruction set and 16-bit Thumb
compressed instruction set. So many on-chip peripherals are there and on chip debugger, on-chip
boot loaders, on-chip RTC, DAC also available[20].
Figure 2.18 An ARM microcontroller IC and its architecture
Figure 2.19 Different types of microcontrollers
2.2.7.4 Why PIC Microcontroller?
PIC Microcontrollers are quickly replacing computers when it comes to programming robotic
devices. These microcontrollers are small and can be programmed to carry out a number of tasks
and are ideal for school and industrial projects. A simple program is written using a computer; it
is then downloaded to a microcontroller which in turn can control a robotic device. Click on the
sections below to view a detailed explanation. PIC is a family of Harvard architecture
microcontrollers made by Microchip Technology, derived from the PIC1640 originally developed
by General Instrument’s Microelectronics Division. The name PIC initially referred to "Peripheral
Interface Controller".
PICs are popular with both industrial developers and hobbyists alike due to their low cost, wide
availability, large user base, extensive collection of application notes, availability of low cost or
free development tools, and serial programming (and re-programming with flash memory)
capability.
PIC is preferred over other microcontrollers because its Core architecture. The PIC architecture is
characterized by its multiple attributes:
=>Separate code and data spaces (Harvard architecture) for devices other than PIC32, which has
Von Neumann architecture.
=>A small number of fixed length instructions.
=>Most instructions are single cycle execution (2 clock cycles), with one delay cycle on branches
and skips.
=>One accumulator (W0), the use of which (as source operand) is implied (i.e. is not encoded in
the op-code).
=>All RAM locations function as registers as both source and/or destination of math and other
functions.
=>A hardware stack for storing return addresses.
=>A fairly small amount of addressable data space (typically 256 bytes), extended through
banking.
=>Data space mapped CPU, port, and peripheral registers.
=>The program counter is also mapped into the data space and writable (this is used to implement
indirect jumps).
This powerful (200 nanosecond instruction execution) yet easy-to-program (only 35 single word
instructions) CMOS FLASH-based 8-bit microcontroller packs Microchip’s powerful PIC
architecture into 28-pin package and is upwards compatible with the PIC16C5X, PIC12CXXX
and PIC16C7X devices. The PIC16F73 features 5 channels of 8-bit Analog-to-Digital (A/D)
converter with 2 additional timers, 2 capture/compare/PWM functions and the synchronous serial
port can be configured as either 3-wire Serial Peripheral Interface (SPI™) or the 2-wire
Interlineated Circuit (I²C™) bus and a Universal Asynchronous Receiver Transmitter (USART).
All of these features make it ideal for more advanced level A/D applications in automotive,
industrial, appliances and consumer applications. There is no distinction between memory space
and register space because the RAM serves the job of both memory and registers, and the RAM is
usually just referred to as the register file or simply as the registers.
2.2.7.4.1 Criteria for choosing Microcontroller:
1. Meeting the computing needs of the task at hand efficiency and cost effectively:
a)
Determine its type, 8-bit,16-bit or 32-bit
b)
Speed
c)
Packaging (40-Pin or QFP)
d)
Power consumption
e)
The amount of RAM and ROM\
f)
The number of I/O pins and the timer
g)
Cost per unit
h)
Ease of upgrade.
2. Availability:
Availability of SW and HW development tools:
a)
Compilers
b)
Assemblers
c)
Debuggers
d)
Emulators
3. Wide availability and reliable source:
Having multiple sources for a given part means one is not hostage to one supplier.
More importantly, competition among suppliers brings about lower cost for that product.
In this project we have used pic16f876a microcontroller IC.
2.2.8 LEAD ACID BATTERY:
A lead-acid battery is an electrical storage device that uses a reversible chemical reaction to store
energy. It uses a combination of lead plates or grids and an electrolyte consisting of a diluted
sulfuric acid to convert electrical energy into potential chemical energy and back again[21].
2.2.8.1 Battery construction:
Lead acid battery consists of flat lead plates for two electrodes which are immersed in a pool of
electrolyte. Lead acid battery used in various applications usually consists of two 6-volt batteries
in series, or a single 12-volt battery. This battery is constructed of several single cells connected
in series each cell produces approximately 2.1 volts. A six-volt battery has three single cells, which
when fully charged produce an output voltage of 6.3 volts. A twelve-volt battery has six single
cells in series producing a fully charged output voltage of 12.6 volts. A battery cell consists of two
lead plates a positive plate covered with a paste of lead dioxide and a negative made of sponge
lead, with an insulating material (separator) in between. The plates are enclosed in a plastic battery
case and then submersed in an electrolyte consisting of water and sulfuric acid[22]. Each cell is
capable of storing 2.1 volts shown in Figure 2.20
Figure 2.20 Single cell of lead acid battery
Lead acid battery does not generate voltage on its own. It only stores charge from another source.
This is the reason lead acid battery is called storage battery, because it only stores charge. The size
of the battery plates and amount of electrolyte determines the amount of charge lead acid battery
can store. The size of this storage capacity is described as the amp hour (AH) rating of a battery.
Six single 2.1-volt cells have been connected in series to make the typical 12-volt battery, which
when fully charged will produce a total voltage of 12.6-volts shown in Figure 2.21
Figure 2.21 12V lead acid battery
2.2.8.2 Battery types:
Lead-acid batteries can be divided according two basic criteria – purpose and construction.
According to purpose they are divided into:

Starter battery

Deep cycle battery
1. Starter battery:
The starter battery is designed to deliver quick bursts of energy (such as starting engines) and
therefore has a greater plate count. Starter batteries have a very low internal resistance, and the
manufacturer achieves this by adding extra plates for maximum surface area. The plates are thin
and the lead is applied in a sponge-like form that has the appearance of fine foam. This method
extends the surface area of the plates to achieve low resistance and maximum power.
2. Deep cycle battery:
The deep cycle battery has less instant energy, but greater long-term energy delivery. Deep
cycle batteries have thicker plates and can survive a number of discharge cycles.
Deep-cycle lead acid battery is built for maximum capacity and high cycle count. The
manufacturer achieves this by making the lead plates thick
[11]
. Although the battery is designed
for cycling, full discharges still induce stress, and the cycle count depends on the depth-of
discharge (DOD).
According to construction lead acid batteries are subdivided into three categories:
1. Flooded or wet:
Flooded or wet cells are most common lead acid battery type in use today. They are not sealed so
the user can replenish any electrolyte. The plastic container is used for flooded cells which is not
sealed so special care has to be taken to ensure safety.
2. Gel:
Gel cells use a thickening agent like fumed silica to immobilize the silica. As the gel cells are
sealed and cannot be re-filled with electrolyte, controlling the rate of charge is important otherwise
there is a serious chance of damaging the battery.
3. AGM:
Absorbed glass mat (AGM) batteries are the latest step of the evolution of lead acid batteries.
Instead of using gel, an AGM uses fiberglass like separator to hold the electrolyte in place. An
AGM can do anything a gel cell can, but better. As they are also sealed, charging need to be
controlled carefully.
2.2.8.3 Charging of lead acid battery:
The lead acid battery uses the constant current constant voltage charge method. Charge time of a
lead acid battery is 12 to 16 hours. With higher charge currents and multi-stage charge methods,
charge time can be reduced to 10 hours or less. Lead acid batteries should be charged in three
stagesa)
Constant-current charge
b)
Topping charge and
c)
Float charge
The constant-current charge applies the bulk of the charge and takes up roughly half of the required
charge time. The topping charge continues at a lower charge current and provides saturation. And
the float charge compensates for the loss caused by self-discharge. During the constant-current
charge, the battery charges to about 70 percent in 5–8 hours; the remaining 30 percent is filled
with the slower topping charge that lasts another 7–10 hours. The topping charge is essential for
the well-being of the battery. If the battery is not completely saturated, the battery will eventually
lose its ability to accept a full charge and the performance of the battery is reduced. The third stage
is the float charge, which compensates for the self-discharge after the battery has been fully
charged. Three stages of charging are shown in Figure 2.22
Figure 2.22 : Charge stages of lead acid battery
2.3 Review of Past Work
In journal [3]. Solar panels-the vital element of this SBCS makes use of exhausted energy.
Compared to all other energy solar energy is abundant and free that can be used to charge batteries
used for any module or electrical kits which are obvious for daily usage. The Smart Charge
Controller will be designed such, so that the solar battery does not get over charged thereby
ensuring no reduction of durability of the battery. This kind of system requires sensors to sense
whether the battery is fully charged or not. After fully charged, detection safety can be achieved
by designing a logic system in the charger, which will automatically disconnect or cut power to
the battery when it is fully charged. When the solar batteries come into account, they get charged
in a very short time period considering of the solar/sun/light hours per day, which is 5 hours in
Bangladesh; whereas Diesel Battery Charging Stations (DBCS) take 1-2 days.
In journal [4], Bangladesh being an over-populated country needs to produce huge amount
of energy to meet its people’s demands. On the other hand, it is quite impossible for her to provide
them with sufficient energy with the conventional way of producing energy due to her being a
developing third world country. Only 62% of her people have the privilege of using electricity. So
apart from finding cost effective ways to harness energy we should also look forward to using the
produced energy efficiently. In this project we look to find a way to reduce the pressure on grid
energy by empowering the street lights using solar panels. In this regard we also focus on having
a smart solar charge controller circuit for ensuring battery longevity. In this project PIC16F876A
microcontroller has been used to sense different voltages and make some decision according to
them. The CCP module of the microcontroller has been used for a variable duty cycle PWM signal
to adjust the brightness of the LED street lights. By the use of LED street lights the reduction of
the consumption of energy was ensured. Apart from this, it can also be used for the electrification
of remote places using solar energy as the smart solar charge controller is cost effective and easy
to implement.
In journal [11]. Photovoltaic or in short term PV is one of the renewable energy resources
that recently has become broader in nowadays technology. The demand or future work is looking
for high efficiency, more reliable and economical price PV charge controller which is come in
portable size has become very popular in PV system. In general, PV system consists of a PV array,
charge controller, rechargeable battery and dc load. PV charge controller is very important in PV
system. In this project, a PV Charge Controller is designed based on microcontroller (PIC
16F877A) which reduced complexity in the number of electronic components and increased
monitoring and regulative functions. This project used dc-dc buck converter circuit which has been
simulated using software of OrCAD PSPICE. Pulse width modulation (PWM) will be
implemented on a PIC 16F877A to control duty cycle, voltage and current in the PV system and
is programmed using software of Microcode Studio. Liquid Crystal Display (LCD) is used to
display the voltage and current from rechargeable battery. The benefit of this project is an
improvement of efficiency depend on duty cycle and voltage change.
In journal [1]. The main aim of this research is to design and construct a 30amp solar charge
controller using Maximum Power Point Tracking (MPPT) to maximize the photovoltaic array
output power, irrespective of the temperature, irradiation conditions and electrical characteristics
of the load. There are two charging stages for the proposed PV charger. At the beginning of the
charging process, a continuous MPPT-charging scheme is adopted. When the State of Charge
(SOC) of battery reaches its set given condition, a pulse-current-charging scheme with an adaptive
rest period is applied to obtain an average charging current with an exponential profile. During the
charging period, the MPPT function is retained to achieve high charging efficiency. The result
gotten from this research adopted using the MPPT system and other techniques used in the past,
are that the PV array output power is used to directly control the synchronous buck converter, thus
reducing the complexity of the system and also protect the battery from repetitive overcharges.
Based on the work reviewed so far, the common weakness seen is that the level of charging
and battery percentage are displayed using an LED indicator, hence in this project, will add an
LCD display for displaying the state of charge and percentage.
CHAPTER 3
METHODOLOGY
3.1 Introduction
This chapter explains about hardware development such as equipment’s, procedures and method
design for the photovoltaic (PV) charge controller. The relevant information is gathered through
literature review from previous chapter. This chapter also will cover about designing the buck
converter, software interface, part by part circuits and complete circuit. Before looking at the
details of all methods below, it is best to begin with brief review of the system design.
3.2 Hardware Development
3.2.1 System Design
The photovoltaic (PV) charge controller was designed to protect the rechargeable battery. To
design this PV charge controller, it consists of seven parts where the first part is a buck converter
circuit, second part is a microcontroller circuit, third part is a driver circuit, four part is
rechargeable battery, five part is voltage sensor, six part is current sensor and seven part is liquid
crystal display, LCD.
Figure 3.1 System design of Photovoltaic Charge Controller
Figure 3.2 Circuit Diagram of 12/24v charger controller
3.1 Resistor: R2 and R3 are the voltage divider resistor that breaks down the voltage from the
source into a level which the ADC input of the microcontroller can handle and measure with
respect with the voltage source value, given bellow is the derivative of R2 and R3:
For resistor R2, R3
V(peak) = 38v
Scaled down voltage = 𝐕(𝐩𝐞𝐚𝐤)
𝑹𝟑
𝑹𝟑+𝑹𝟐
Scaled down voltage = 5V maximum
Assuming R3 = 1.5k
𝑽𝒑𝒆𝒂𝒌 ∗ 𝑹𝟑
R2 = 𝑺𝒄𝒂𝒍𝒆𝒅 𝒅𝒐𝒘𝒏 𝒗𝒐𝒍𝒕𝒂𝒈𝒆 − 𝑹𝟑 =
𝟑𝟖𝒗 ∗ 𝟏.𝟓𝒌
𝟓𝒗
− 𝟏. 𝟓𝒌
R2 = 9.9k
R2 = 10k
3.2 Regulator: L7805 voltage controller which is utilized to control up the framework, it is 5V in
light of the fact that microcontroller can't acknowledge more than 5V supply voltage.
3.3 Capacitor: C1, C2, are channel capacitor which engages us to get a smooth signal for the
microcontroller. C1, C2, regard is picked subject to the datasheet of the microcontroller.
3.4 Capacitor input filter: C3 is the input filter capacitor used to filter the DC ripples from the
input voltage.
3.5 Microcontroller: The Pic16f690 is the hearth of the system, it is responsible for storing the
data and controls the operation of the entire system.
3.6 LCD: 16x2 LCD monitors the operation of the system and displays respective information for
the user so as to have an idea of what is going on in the microcontroller.
3.7 Resistor R1: pull up resistors which will enable the reset pins of the microcontroller to be at a
state of 1 before its being used.
Figure 3.3 Pull up resistor
The most common method of ensuring that the inputs of digital logic gates and circuits cannot
self-bias and float about is to either connect the unused pins directly to ground (0V) for a constant
low “0” input, (OR and NOR gates) or directly to Vcc (+5V) for a constant high “1” input (AND
and NAND gates).
Figure 3.4 Pull-up Resistor Application
By using these two pull-up resistors, one for each input, when switch “A” or “B” is open (OFF),
the input is effectively connected to the +5V supply rail via the pull-up resistor. The result is that
as there is very little input current into the input of the logic gate, very little voltage is dropped
across the pull-up resistor so nearly all the +5V supply voltage is applied to the input pin creating
a HIGH, logic “1” condition.
When switches “A”, or “B” are closed, (OFF) the input is shorted to ground (LOW) creating a
logic “0” condition as before at the input. However, this time we are not shorting out the supply
rail as the pull-up resistor only passes a small current (as determined by Ohms law) through the
closed switch to ground.
By using a pull-up resistor in this way, the input always has a default logic state, either “1” or “0”,
high or low, depending on the position of the switch, thus achieving the proper output function of
the gate at “Q” and therefore preventing the input from floating about or self-biasing giving us
exactly the switching condition we require.
While the connection between Vcc and an input (or output) is the preferred method for using a
pull-up resistor, the question arises as how do we calculate the value of the resistance requires to
ensure the correct operation of the input.
3.8 Calculating Pull-up Resistor Value
All digital logic gates, circuits and micro-controllers are limited not only by their operating
voltage, but in the current sinking and sourcing ability of each input pin. Digital logic circuits
operate using two binary states which are normally represented by two distinct voltages: a high
voltage VH for logic “1” and low voltage VL for logic “0”. But within each of these two voltage
states, there is a range of voltages which define the upper and lower voltages of these two binary
states.
Figure 3.5 TTL input voltage level
So, for example, for the TTL series of digital logic gates, the voltage ranges representing a logic
level “1” and a logic level “0” are shown.
Where: VIH (min) = 2.0V is the minimum input voltage guaranteed to be recognized as a logic
“1” (high) input and VIL (max) = 0.8V is the maximum input voltage guaranteed to be recognized
as a logic “0” (low) input.
In other words, TTL input signals between 0 and 0.8V are considered “LOW”, and input signals
between 2.0 and 5.0V are considered “HIGH”. Any voltage in-between 0.8 and 2.0 volts is not
recognised as a logic “1” or logic “0”.
When logic gates are connected together, the current flows between the output of one logic gate
and the input of another. The amount of current required by a basic TTL logic gate input depends
on whether the input is a logic “0” (LOW) or a logic “1” (HIGH) as this creates a current-sourcing
action for a logic “0” and a current-sinking action for a logic “1”.
When the input of the logic gate is HIGH, a current flow into the TTL input as the input acts
basically as a path connected directly to ground. This input current, IIH (max) is positive in value
as it flows “into” the gate and for most TTL 74LSxxx inputs have a value of 20µA.
Likewise, when the input of the logic gate is LOW, the current flows out of the TTL input as the
input acts basically as a path connected directly to Vcc. This input current, IIL (max) is negative
in value as it flows “out of” the gate and for most TTL 74LSxxx inputs, has a value of -400μA, (0.4mA).
Note that the values of HIGH and LOW voltages and currents differ between TTL logic families
and is also much, much lower for CMOS logic families. Also, the input voltage and current
requirements for micro-controllers, PIC, Arduino, Raspberry Pie, etc will also be different so
please consult their data sheets first.
By knowing the information above, we can calculate the maximum pull-up resistor value required
for a single TTL series logic gate as:
3.8.1 Pull-up Resistor Value
Where
VCC = supply voltage
VIH = High level input voltage
VIL = Low level input voltage
IIH = High level input current
IIL = Low level input current
According to the datasheet of the pic16f690
Vcc = 5V
VIH = 2V
IIH = 100uA
𝑹𝒎𝒂𝒙 =
𝑽𝒄𝒄−𝑽𝒊𝒉
𝑰𝒊𝒉
𝟓−𝟐
= 𝟎.𝟎𝟎𝟎𝟏 = 𝟑𝟎𝐤Ω…………………………………………………………. (14)
The maximum pulls up resistor we can use is 30kΩ for a voltage drop of 3v
Hence, we require 4v as our logic HIGH, resistor value for dropping 1 volt from Vcc is given as:
𝑹=
𝑽𝒄𝒄−𝑽𝒊𝒉
𝑰𝒊𝒉
𝟓−𝟒
= 𝟎.𝟎𝟎𝟎𝟏 = 𝟏𝟎𝐤Ω………………………………………………………………. (15)
The pull-up resistance required to drop 1 volt for a TTL series logic gate would be 10kΩ. While
this calculated value would work, it leaves no room for error as the voltage drop across the resistor
is at its maximum while the input current is at its minimum.
Ideally, we would want a logic “1” to be as close to Vcc as possible to guarantee 100% that the
gate sees a HIGH (logic-1) input through the pull-up resistor. Reducing the resistive value of this
pull-up resistor would give us a greater error margin should the tolerance of the resistor or the
supply voltage not be as calculated. However, we do not want the resistor value to be too low as
this would increases current flow into the gate increasing power dissipation.
So, if we assume a voltage drop of only one volt, (1.0V) across the resistor giving double the input
voltage at 4 volts, a quick calculation would give us a single pull-up resistor value of 50kΩ.
Reducing the resistive value further, will produce a smaller voltage drop but increase the current.
Then we can see that while there may be a maximum allowable resistive value, the resistance value
for pull-up resistors is not usually that critical with resistance values ranging from between 10k to
100k ohms acceptable.
This simple example above gives us the maximum value of the pull-up resistor required to bias a
single TTL gate. But we can also use the same resistor to bias multiple inputs to a logic “1” value.
For example, let’s assume we have constructed a digital circuit and that there are ten unused logic
gate inputs. As a single standard TTL 74LS gate, has an input current, IIH (max) of 20μA (also
called a fan-in of 1), then ten TTL logic gates would require a total current of: 10 x 20μA = 200μA
representing a fan-in of 10.
3.9 Resistor: R4, R5 are biasing resistor that provides proper voltage and current to Q4, Q3, so as
to prevent it from being damaged.
3.9.1 For resistor R8
β = 100
Ic = 100mA
Vcc = 5V
IB =
𝑰𝒄
𝛃
Vcc = IBRB + VBE
RB =
𝑽𝒄𝒄−𝑽𝒃𝒆
𝑰𝒃
since VBE is generally quite small as compared to VCC, it can be neglected with little error.
According to the datasheet of bc547, in other to attain the maximum gain at output of the transistor,
say Ic = 100mA,
Then,
IB = 5.0mA
RB =
𝑽𝒄𝒄
𝐈𝐛
=
𝟓
𝟎.𝟎𝟎𝟓
RB = 1kΩ
3.10 Mosfet Transistor: transistor Q1, Q2, works as a switch and controls the charging of the
battery, the two mosfet opens and closes with respect to the PWM signal from CCP1 pin of the
microcontroller, as the battery voltage approaches 14.4v or 28.4v the mosfet drain to source will
start opening up gradually and vice versa.
3.11 Transistor: Q3 and Q4 are the mosfet drivers, the signal from the CCP1 pin of the
microcontroller is very low to power the gate of the MOSFETS, since the Vth of IRF3205 is 2.4v
according to the datasheet and the voltage the CCP1 is 1.6v, hence this transistor helps to step up
the PWM signal voltage.
3.11.1 MOSFETS Ratings
With the input voltage supply from sources (Vmax) = 38V supply
Charging current = 10Amps
Hence, we a MOSFET that can 15Amps collector current and 45v VCE
According to the datasheet of IRF3205
VCE is 50v
ID is 105Amps
Figure 3.6 Flow chart
3.2.2 Program code:
We have used MPLAB software to compile the program. The code which was burned in the
microcontroller is given bellow:
unsigned int v1;
void main () {
TRISA=0xFF;
TRISB=0X00;
PORTB=0X00;
ADCON0=0x00;
//0b00010101;
ADCON1=0b00000000;
pwm1_init (40000);
ADC_Init ();
while (1)
{
pwm1_start ();
delay_us (50);
v1=ADC_read (0);
if(v1<=396) {// DISCONNECTED (if battery is DEAD)
pwm1_set_duty (0);
}
else if(v1>396 && v1<=436) {// v>=396: if the battery already has charge, but less than 50%
(for normal battery) or 30% (for solar battery) of its capacity.
pwm1_set_duty (230);
}
else if(v1>436 && v1<=473) {// BULK CHARGE pwm1_set_duty (230);
}
if(v1>473 && v1<=513) {// ABSORPTION CHARGE
pwm1_set_duty (30);
}
else if(v1>513 && v1<534) {// FLOAT CHARGE pwm1_set_duty (30);
}
else if(v1>=534) {// DISCONNECTED (if battery is fully charged or DEAD) pwm1_set_duty
(0);
}
}
}
CHAPTER 4
4.1 Test and Results
The actual translation of the circuit of the burglar alarm system in a printed circuit board pattern
as carried out using EasyEDA PCB software. First the circuit was compiled and check for errors
before the transfer to a PCB layout for onward processing as a PCB file. On the layout the different
component foot points were carefully placed on a dimension of (80X 100mm). The placement was
done to ensure the shortest possible distance between related components. An electrical rules
violation check (ERC) was performed on the design and the placed footprints before processing
with the routing. The entire component electrical connection was then auto routed using the routing
component of easyeda software. The actual implementation of the PCB design was achieved using
the tonner.
4.2 Simulation result:
Figure 4.1 Bulk stage charging
Figure 4.2 Absorption stage
Figure 4.3 Float state charging
4.3 Experimental results:
Not Charging:
Figure 4.4 No charge wave shape
Bulk Charge:
40% Ah to be used. It is when voltage is between 10.6 V to 12.6V.
Duty cycle used: 90 %
Figure 4.5 Bulk charging wave shape
Float Charge:
5 percent of Ah to be used. It is when voltage is between 12.6 V to 14.3V. Duty cycle used: 10
percent.
Figure 4.6 Float charging wave shape
Full Charge (HVD):
Duty cycle used:0 %
When the battery voltage is 14.4V, circuit is open, the charging current is 0 A
Figure 4.7 Full charge wave shape
CHAPTER 5
5.1 Conclusion
In this project we have successfully implemented the smart charge controller. The smart charge
controller is fairly accurate and cost effective as well as energy efficient. The switching needed for
different voltages for the smart charge controller is also responding according to the design. The
use of a microcontroller has made the charge controller more efficient and less costly. The only
loss occurring in this circuit is due to the MOSFET (0.5 volts). There is a diode also in the forward
path of charging which will also be responsible for some loss. Other than this the project is both
cost and energy efficient and thus it is very much acceptable for commercial use.
5.2 Recommendation
There are many opportunities ahead. The project can be a great prototype project in near future.
Only some modifications can make great changes.
•
Making it more efficient so that it can resist burnout and current overflow.
•
Building larger solar charging station connected to the national grid system to meet up
increasing demand of load
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E. I. Okhueleigbe, J. O. Oviri, and A. O. Okhueleigbe, “Design and Construction of A 30
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1–6,
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