MICROCONTROLLER BASED SINGLE
AXIS SOLAR TRACKER
Prepared by
Sl Name ID. No.
1 Ms. Rehana Akter ID: 102-296-511
2 Mir Md Emam Uddin ID: 102-168-511
3 Md. Jamil Uddin ID: 102-085-511
4 Md. Mahbub Mehedi ID: 102-049-511
5 MD. Shariful Amran ID: 102-102-511
A thesis submitted in partial fulfillment for the degree of B.sc. in
Electrical and Electronics Engineering
Course Code: EEE – 499
Atish Dipankar University of Science &
Technology (ADUST)
i
MICROCONTROLLER BASED SINGLE AXIS SOLAR TRACKER
An internship report submitted to the department of EEE, Atish Dipankar University of Science and Technology for partial fulfillment of the degree of B.Sc. in Electrical and Electronic Engineering.
Submitted by:
Sl Name ID. No.
1 Ms. Rehana Akter ID: 102-296-511 2 Mir Md Emam Uddin ID: 102-168-511 3 Md. Jamil Uddin ID: 102-085-511 4 Md. Mahabub Mehedi ID: 102-049-511 5 MD. Shariful Amran ID: 102-102-511
Supervised By:
Marzia Hoque Tania Signature: _______________ Lecturer Date:
Department of Electrical & Electronic Engineering
CERTIFICATE
This is to certify that the B.Sc. thesis entitled “Microcontroller based single
axis solar tracker” submitted by this group (Ms. Rehana Akter, ID No:
296-511. Mir Imam Uddin, ID No: 168-511. Md Jamil Uddin, ID No: 102-085-511. Md. Mahbub Mehedi, ID No: 102-049-511. Md Shariful Amran, ID No: 102 102-511)
The thesis represents an independent and original work on the part of the candidates. The research work has not previously formed the basis for the award of any degree, diploma, fellowship or any other discipline.
The whole work of this thesis has been planned and carried out by this group under supervision and guidance of the faculty members of Atish Dipankar University of Science & Technology, Dhaka, Bangladesh.
____________________ Marzia Hoque Tania
Lecturer
iii
ABSTRACT
The work we present is a microcontroller based single axis solar tracking device which enables the solar panel. To face with the sunlight to increase the output of the solar PV systems. It is an automatic tracking device which aims to maximize in harvesting solar power. When the intensity of the light, decries, the system automatically changes its direction to get the maximize intensity of sunlight. Light depended resisters are used as sensor. Data received by the sensors is processed by the microcontroller. Signal from the microcontroller in send to the DC gear motor. The clockwise and anticlockwise rotation of the motor is conducted by the relays. This prototype might be implemented is residential uses. Due to low power consumption this prototype would be very hungry is real life application.
ACKNOWLEDGEMENT
At first we would like to thank our supervisor, Marzia Hoque Tania, Lecturer, ADUST. for giving us the opportunity to work under his supervision, the endless hours of help, suggestions, advice and support to keep us on track during the development of this thesis.
Last, but not least, we would like to thank our parents and family for making it possible for us to study and for their constant help and support.
The Authors Dhaka
v
DEDICATION
Table of Contents
Abstract ………... Acknowledgement ……… Dedication ……….. Figure ………... Table ………. iii iv v x-xii xiiiChapter- 1:
Introduction and overview ………..
1.1. Renewable energy ……….. 1.2. Use of Renewable Energy ……….... 1.3. Types of renewable energy ……… 1.3.1 Solar energy ……….. 1.3.2 Wind energy ……….. 1.3.3 Geothermal energy ……….. 1.3.4 Bio energy ……….. 1.3.5 Hydropower ………... 1.3.6 Ocean energy ……… 1.3.7 Hydrogen energy ……….. 1.4 Importance of renewable energy ……….. 1.4.1 Environmental Benefits ……….. 1.4.2 Energy for our children's ………. 1.4.3 Jobs and the Economy ……… 1.4.4 Energy Security ……… 1.5 Necessary of solar tracker ………. 1.6 Global technical potential of solar energy ………
01-09 01 02-03 03 03 03 04 04 05 06 06 07 07 07 07-08 08 08 08-09
Chapter-2:
Solar photovoltaic (PV) system ………..
2.1 Photovoltaic (PV) system ……… 2.2 Work of solar photovoltaic (PV) system ………...
09-16 10 11-12
vii
2.3 Types of photovoltaic (PV) systems ………. 2.3.1 Single-crystalline or mono crystalline ……… 2.3.2 Polycrystalline cells ………. 2.3.4 Amorphous Silicon ……… 2.4 Components of a solar photovoltaic (PV) ……… 2.4.1 Charge controller ……….. 2.4.2 Batteries ………. 2.4.3 Inverter ……… 2.5 Advantages of photovoltaic (PV) ………... 2.6 Disadvantage of photovoltaic (PV) ……… 2.7 Photovoltaic (PV) applications and market ………..
11-12 12 13 13 14 14 15 15 15-16 16 16
Chapter-3:
Solar path of the sun ……….
3.1 Basic of solar radiation ……… 3.2 Solar Constant and "Sun Value" ………. 3.3 Extraterrestrial and Terrestrial Spectra………. 3.3.1 Extraterrestrial Spectra ……… 3.3.2 Terrestrial Spectra ……… 3.4 The Changing Terrestrial Solar Spectrum ………... 3.5 Standard Spectra ………. 3.6 Geometry of Solar Radiation ……….. 3.7 Dirunal and Annual Variation ………. 3.8 Solar Motion ……….. 17-25 17 17 18 18 18-19 19-20 20-23 23 24 25
Chapter-4:
Solar tracking system ………...
4.1 Solar tracker ………. 4.2 Types of solar tracker ………. 4.2.1 Single axis solar tracker ……….. 4.2.1.1 Types of single axis solar tracker ………...
26-33 27 27 28 28
4.2.1.2 Horizontal single axis tracker (HSAT) ………. 4.2.1.3 Vertical single axis tracker (VSAT) ……….. 4.2.1.4 Tilted single axis tracker (TSAT) ………. 4.2.1.5 Polar aligned single axis trackers (PASAT) ………
4.2.2 Dual axis solar tracker ………. 4.2.2.1 Types of duel axis solar tracker ……….
4.2.2.2 Tip–tilt dual axis tracker ………. 4.2.2.3 Azimuth-altitude dual axis tracker (AADAT) ………...
28-29 29 30 30-31 31 32 32 33
Chapter-5:
Construction of microcontroller based single
axis solar tracker ……….
5.1 Single axis solar trackers ………... 5.2 Mechanical System ………. 5.3 Methodology ………. 5.4 Working principle ………. 5.5 Description of the component ……… 5.5.1 Microcontroller ……….. 5.5.1.1 Use of microcontroller ……….. 5.5.2 Gear-motor ……… 5.5.2.1 Gear-motor Benefits ………. 5.5.2.2 Application of Gear-motor ………... 5.5.3 Voltage regulator ……….. 5.5.4 Definition of relay ……… 5.5.4.1 Types of relay ……… 5.5.4.2 Application of relay ………... 5.5.5 Resistor ……….… 5.5.6 Capacitor ………... 5.5.7 Transistor ……….. 5.5.7.1 Types of Transistor ………..…… 34-52 34 35 35-38 39 39 39 39-40 44 44 44 45 45 46 46 46-47 48 48 49
ix
5.5.8 Push button switch ………..………… 5.5.9 Oscillator ……… 5.5.9.1 Application of oscillators ……….. 5.5.10 Light depended resistor (LDR) ……… 5.5.10.1 Operation of LDR 49 50 50 51 51-52 Chapter-6:
Conclusion ………
6.1 Accuracy requirements.……….. 6.2 Advantages of solar tracker ………... 6.3 Scope of future work of solar trackers ……….Summary ………
Reference ………...
53-55 53 54-55 55 56 57Figure
Figure 1.1 solar energy ………. Figure 1.2 wind energy ………. Figure 1.3 Geothermal energy ………. Figure 1.4 Bio-energy ……… Figure 1.5 Hydropower energy ……… Figure 1.6 Ocean energy ……….. Figure 1.7 Hydrogen energy ……… Figure 2.1 Solar photovoltaic (V) system ………... Figure 2.2 Single-crystalline or mono crystalline ……….. Figure 2.3 Multi- or poly-crystalline ………. Figure 2.4 Amorphous silicon ……….. Figure 2.5 Block diagram of a typical solar PV system ……… Figure: 3.1 Spectrum of the radiation outside the earth’s atmosphere compared to spectrum of a 5800 K blackbody………. Figure: 3.2 The total global radiation on the ground has direct, scattered and reflective components……… Figure: 3.3 Normally incident solar spectrum at sea level on a clear day. The dotted curve shows the extrarrestrial spectrum……… Figure: 3.4 The path length in units of Air Mass, changes with the zenith Angle ……….. Figure: 3.5 Standard spectra ……… Figure: 3.6 Actual scan of a simulator with resolute on under 2 nm; high resolution doesn’t enhance these Doppler broadened lines. Middle: Scan of same simulator with 10 nm resolution. Bottom: Smoothed
03 04 04 05 05 06 07 11 12 13 13 14 17 19 19 20 21
xi
version of top curve. We used repeated Savitsky-Golay smoothing ……. Figure: 3.7 Comparison of the UV portion of the WMO measured solar spectrum and the modeled CIE AM 1 direct spectrum. All the modeled spectra, CIE or ASTM, used as standards, omit the fine details seen in measured spectrum……… Figure: 3.8 The solar disk subtends a 1/2° angle at the earth ……… Figure: 3.9 Diurnal variations of global solar radiative flux on a sunny day……… Figure: 3.10 Diurnal variations of global solar radiative flux on a cloudy day……….. Figure: 3.11 The global solar irradiance at solar noon measured in
Arizona, showing the annual variation………. Figure: 3.12 Solar Motion ………. Figure 4.1 PV array fixed tilt ………. Figure 4.2 Single axis tracking system ………... Figure 4.3 Dual axis tracking system ……….. Figure 4.4 Single axis solar tracker ………. Figure: 4.5 Horizontal single axis trackers ………
Figure: 4.6 Vertical single axis trackers ……….
Figure: 4.7Tilted single axis trackers ……….
Figure: 4.8 Polar aligned single axis trackers ………...
Figure 4.9 Dual axis solar trackers ………. Figure: 4.10 Tip–tilt dual axis trackers ………
Figure: 4.11 Azimuth-altitude dual axis trackers ………..
Figure: 5.1 Final solar tracker prototypes ………. Figure: 5.2 Block diagram of the project (single axis solar tracker)………
22 23 23 24 24 25 25 26 27 27 28 29 30 30 31 31 33 33 34 36
Figure: 5.3 Flow chart of the project (single axis solar tracker)………….. Figure: 5.4 Circuit diagram of the project (single axis solar tracker)…….. Figure: 5.5 Pin Diagram of Microcontroller (PIC 16F84A)……… Figure: 5.6 Block Diagram of microcontroller (PIC 16F84A)……… Figure: 5.7 Gear-motor ………. Figure: 5.8 Voltage regulator ……… Figure: 5.9 Relay ……… Figure: 5.10 Symbol of resistor ……… Figure: 5.11 Picture of resistor ………. Figure: 5.12 Symble of capacitor ………. Figure: 5.13 Picture of Capacitor ………. Figure: 5.14 Symble of Transistor ………... Figure: 5.15 Push button switch ……….. Figure: 5.16 Circuit diagram of Oscillator ……….. Figure: 5.17 Picture of LDR ……….. 37 38 40 42 45 45 46 47 47 48 48 49 50 51 52
xiii
Table
Table 2.1 Efficiency of different types of solar cell ……… Table: 3.1 Power Densities of Published Standards………. Table: 5.1 Specification of solar tracking system ……….. Table: 5.2 List of Equipments ………... Table: 5.3 Description of pin number of Microcontroller (PIC 16F84A)….. Table: 6.1 Accuracy direct powers lost ………...
14 21 35 36 41 54
Chapter-1
Introduction and overview
Solar energy is being used as an alternative energy source years. But the efficiency of solar panel, battery and the overall system efficiency are point of concerns to use the solar PV system as means of power generation. The sunlight is sufficient enough to overcome the power crisis of the world but is till date it is not possible to capture and utilized the full range of the sun energy of the sunlight.
This thesis book presents a solar tracking system to enhance the output power of a solar PV system. This project helps to increases the power generation by setting the equipment to get maximum sunlight automatically. This system is tracking the sunlight. When there is a decrease in the intensity of light, this system automatically changes its direction of the solar panel to get maximum intensity of sunlight.
We are using three sensors in three directions to sense the direction of maximum intensity of sunlight. The difference between the outputs of the sensors is given to the microcontroller unit.
Here we are using the microcontroller for tracking the sunlight. It will process the input voltage from the oscillator circuit and control the direction in which the motor has to be rotated so that it will receive maximum intensity of light from the sun.
1.1 Renewable Energy:
Renewable energy uses energy sources that are continually replenished by nature—the sun, the wind, water, the Earth’s heat, and plants. Renewable
energy technologies turn these fuels into usable forms of energy—most often electricity, but also heat, chemicals, or mechanical power.
1.2 Use of Renewable Energy:
Today we primarily use fossil fuels to heat and power our homes and fuel our cars. It’s convenient to use coal, oil, and natural gas for meeting our energy needs, but we have a limited supply of these fuels on the Earth. We’re using them much more rapidly than they are being created. Eventually, they will run out. And because of safety concerns and waste disposal problems, the United States will retire much of its nuclear capacity by 2020. In the meantime, the nation’s energy needs are expected to grow by 33 percent during the next 20 years. Renewable energy can help fill the gap. Even if we had an unlimited supply of fossil fuels, using renewable energy is better for the environment. We often call renewable energy technologies “clean” or “green” because they produce few if any pollutants. Burning fossil fuels, however, sends greenhouse gases into the atmosphere, trapping the sun’s heat and contributing to global warming. Climate scientists generally agree that the Earth’s average temperature has risen in the past century. If this trend continues, sea levels will rise, and scientists predict that floods, heat waves, droughts, and other extreme weather conditions could occur more often. Other pollutants are released into the air, soil, and water when fossil fuels are burned. These pollutants take a dramatic toll on the environment—and on humans. Air pollution contributes to diseases like asthma. Acid rain from sulfur dioxide and nitrogen oxides harms plants and fish. Nitrogen oxides also contribute to smog.
Renewable energy will also help us develop energy independence and security. The United States imports more than 50 percent of its oil, up from 34 percent in 1973. Replacing some of our petroleum with fuels made from plant matter, for example, could save money and strengthen our energy security. Renewable energy is plentiful, and the technologies are improving all the time. There are
many ways to use renewable energy. Most of us already use renewable energy in our daily lives.
1.3 Types of renewable energy:
1.3.1 Solar energy:
Most renewable energy comes either directly or indirectly from the sun. Sunlight, or solar energy, can be used directly for heating and lighting homes and other buildings, for generating electricity, and for hot water heating, solar cooling, and a variety of commercial and industrial uses.
Figure 1.1 Solar energy
1.3.2 Wind energy:
We have been harnessing the wind's energy for hundreds of years. From old Holland to farms in the United States, windmills have been used for pumping water or grinding grain. Today, the windmill's modern equivalent - a wind turbine - can use the wind's energy to generate electricity.
Figure 1.2 Wind energy
1.3.3 Geothermal Energy:
Geothermal energy is the heat from the Earth. It's clean and sustainable. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma.
Figure 1.3 Geothermal energy
1.3.4 Bio-energy:
We have used biomass energy or bioenergy the energy from organic matter -for thousands of years, ever since people started burning wood to cook food or to keep warm. Even the fumes from landfills can be used as a biomass energy source.
Figure 1.4 Bio-energy
1.3.5 Hydropower:
Flowing water creates energy that can be captured and turned into electricity. This is called hydroelectric power or hydropower. The most common type of hydroelectric power plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. But hydroelectric power doesn't necessarily require a large dam. Some hydroelectric power plants just use a small canal to channel the river water through a turbine.
1.3.6 Ocean energy:
The Ocean can produce two types of energy: thermal energy from the sun's heat, and mechanical energy from the tides and waves. Oceans cover more than 70% of Earth's surface, making them the world's largest solar collectors. The sun's heat warms the surface water a lot more than the deep ocean water, and this temperature difference creates thermal energy. Just a small portion of the heat trapped in the ocean could power the world.
Figure 1.6 Ocean energy
1.3.7 Hydrogen energy:
Hydrogen is the simplest element. An atom of hydrogen consists of only one proton and one electron. It's also the most plentiful element in the universe. Despite its simplicity and abundance, hydrogen doesn't occur naturally as a gas on the Earth - it's always combined with other elements. Water, for example, is a combination of hydrogen and oxygen (H2O).
Figure 1.7 Hydrogen energy
1.4 Importance of renewable energy:
Renewable energy is important because of the benefits it provides. The key benefits are:
1.4.1 Environmental Benefits
Renewable energy technologies are clean sources of energy that have a much lower environmental impact than conventional energy technologies.
1.4.2 Energy for our children's
Renewable energy will not run out Ever. Other sources of energy are finite and will someday be depleted.
1.4.3 Jobs and the Economy
Most renewable energy investments are spent on materials and workmanship to build and maintain the facilities, rather than on costly energy imports. Renewable energy investments are usually spent within the United States, frequently in the same state, and often in the same town. Meanwhile, renewable
energy technologies developed and built in the United States are being sold overseas, providing a boost to the U.S. trade deficit.
1.4.4 Energy Security
After the oil supply disruptions of the early 1970s, our nation has increased its dependence on foreign oil supplies instead of decreasing it. This increased dependence impacts more than just our national energy policy.
1.5 Necessary of solar tracker:
Many standard PV systems in residential areas do not have solar trackers. For their purposes, having the stand-alone system is sufficient and meets the needs and goals of the customer.
Whether solar trackers are beneficial and recommended is dependent on various factors, including weather, location, obstruction, and cost. In some cases, solar trackers can potentially make solar panels 25-35% more efficient, which means that more power can be generated with less space and less panels.
However, if the location of the installation does not allow the trackers to work effectively, then the cost of purchasing the solar trackers can lead to money wasted. So, it’s important to discuss your goals with your installer and have them give you a full on-site analysis of your particular project.
1.6 Global technical potential of solar energy:
The amount of solar energy that could be put to human use depends significantly on local factors such as land availability and meteorological conditions and demands for energy services. The technical potential varies over the different regions of the Earth, as do the assessment methodologies. As described in a comparative literature study (Krewitt et al.,2009) for the German Environment Agency, the solar electricity technical potential of PV and CSP depends on the available solar irradiance, land use exclusion factors and the future development of technology improvements. Note that this study used different assumptions for the land use factors for PV and CSP. For PV, it assumed that 98% of the technical potential comes from centralized PV power plants and that the suitable land area in the world for PV deployment averages 1.67% of total land area. For CSP, all land areas with high direct-normal irradiance (DNI)—a minimum DNI of 2,000 kWh/m2/yr (7,200 MJ/m/yr)—were
defined as suitable, and just 20% of that land was excluded for other uses. The resulting technical potentials for 2050 are 1,689 EJ/yr for PV and 8,043 EJ/yr for CSP.
Analyzing the PV studies (Hofman et al., 2002; Hoogwijk, 2004; de Vries et al., 2007) and the CSP studies (Hofman et al., 2002; Trieb, 2005; Trieb et al., 2009a) assessed by Krewitt et al. (2009), the technical potential varies signifi cantly between these studies, ranging from 1,338 to 14,778 EJ/yr for PV and 248 and 10,791 EJ/yr for CSP. The main difference between the studies arises from the allocated land area availabilities and, to some extent, on differences in the power conversion efficiency used.
The technical potential of solar energy for heating purposes is vast and difficult to assess. The deployment potential is mainly limited by the demand for heat. Because of this, the technical potential is not assessed in the literature except for REN21 (Hoogwijk and Graus, 2008) to which Krewitt et al. (2009) refer. In order to provide a reference, REN21 has made a rough assessment of the technical potential of solar water heating by taking the assumed available rooftop area for solar PV applications from Hoogwijk (2004) and the irradiation for each of the regions. Therefore, the range given by REN21 is a lower bound only.
Chapter-2
Solar photovoltaic (PV) system
2.1 Photovoltaic (PV) system
The increasing demand for energy, the continuous reduction in existing sources of fossil fuels and the growing concern regarding environment pollution, have pushed mankind to explore new technologies for the production of electrical energy using clean, renewable sources, such as solar energy, wind energy, etc. Among the non-conventional, renewable energy sources, solar energy affords great potential for conversion into electric power, able to ensure an important part of the electrical energy needs of the planet. The conversion of solar light into electrical energy represents one of the most promising and challenging energetic technologies, in continuous development, being clean, silent and reliable, with very low maintenance costs and minimal ecological impact. Solar energy is free, practically inexhaustible, and involves no polluting residues or greenhouse gases emissions. The conversion principle of solar light into electricity, called Photo-Voltaic or PV conversion, is not very new, but the efficiency improvement of the PV conversion equipment is still one of top priorities for many academic and/or industrial research groups all over the world.
2.2 Work of solar photovoltaic (PV) system:
The sun delivers its energy to us in two main forms: heat and light. There are two main types of solar power systems, namely, solar thermal systems that trap heat to warm up water, and solar PV systems that convert sunlight directly into electricity.
When the PV modules are exposed to sunlight, they generate direct current (“DC”) electricity. An inverter then converts the DC into alternating current (“AC”) electricity, so that it can feed into one of the building’s AC distribution boards (“ACDB”) without affecting the quality of power supply.
Figure: 2.1 solar photovoltaic (PV) systems
In the summary, the PV solar system consists of three parts: i) Solar panels or solar arrays,
ii) Balance of system, iii) Load.
2.3 Types of photovoltaic (PV) systems:
PV systems can provide clean power for small or large applications. They are already installed and generating energy around the world on individual homes, housing developments, offices and public buildings. Today, fully functioning solar PV installations operate in both built environments and remote areas where it is difficult to connect to the grid or where there is no energy
infrastructure. PV installations that operate in isolated locations are known as standalone systems. In built areas, PV systems can be mounted on top of roofs (known as Building Adapted PV systems – or BAPV) or can be integrated into the roof or building facade (known as Building Integrated PV systems – or BIPV). Modern PV systems are not restricted to square and flat panel arrays. They can be curved, flexible and shaped to the building’s design. Innovative architects and engineers are constantly finding new ways to integrate PV into their designs, creating buildings that are dynamic, beautiful and provide free, clean energy throughout their life. With the growing demand of solar power new technologies are being introduced and existing technologies are developing. There are three main types of solar PV cells:
Single crystalline or mono crystalline
Multi- or poly-crystalline
Amorphous silicon
2.3.1 Single-crystalline or mono crystalline:
It is widely available and the most efficient cells materials among all. They produce the most power per square foot of module. Each cell is cut from a single crystal. The wafers then further cut into the shape of rectangular cells to maximize the number of cells in the solar panel.
2.3.2 Polycrystalline cells:
They are made from similar silicon material except that instead of being grown into a single crystal, they are melted and poured into a mold. This forms a square block that can be cut into square wafers with less waste of space or material than round single-crystal wafers.
Figure: 2.3 Multi- or poly-crystalline
2.3.3 Amorphous Silicon:
Amorphous silicon is newest in the thin film technology. In this technology amorphous silicon vapor is deposited on a couple of micro meter thick amorphous films on stainless steel rolls. Compared to the crystalline silicon, this technology uses only 1% of the material.
Table 2.1 Efficiency of different types of solar cells
Cell type Efficiency, %
Mono crystalline 12 – 18 Polycrystalline 12 – 18 Amorphous Silicon 6 – 8
2.4 Components of a solar photovoltaic (PV) system:
A typical solar PV system consists of solar panel, charge controller, batteries, inverter and the load. Shows the block diagram of such a photovoltaic (PV) system
Solar
panel Charge controller
Battery
System Inverter AC power
DC power
Figure 2.5 Block diagram of a typical solar PV system
2.4.1 Charge controller:
When battery is included in a system, the necessity of charge controller comes forward. A charge controller controls the uncertain voltage build up. In a bright sunny day the solar cells produce more voltage that can lead to battery damage. A charge controller helps to maintain the balance in charging the battery.
2.4.2 Batteries:
To store charges batteries are used. There are many types of batteries available in the market. But all of them are not suitable for solar PV technologies. Mostly used batteries are nickel/cadmium batteries. There are some other types of high energy density batteries such as- sodium/sulphur, zinc/bromine flow batteries. But for the medium term batteries nickel/metal hydride battery has the best cycling performance. For the long term option iron/chromium redox and zinc/manganese batteries are best. Absorbed Glass Mat (AGM) batteries are also one of the best available potions for solar PV use.
2.4.3 Inverter:
Solar panel generates dc electricity but most of the household and industrial appliances need ac current. Inverter converts the dc current of panel or battery to the ac current. We can divide the inverter into two categories. They
are- Stand alone and
Line-tied or utility-interactive
2.5 Advantages of photovoltaic (PV):
• Environmentally friendly • No noise, no moving parts • No emissions
• No use of fuels and water
• Minimal maintenance requirements • Long lifetime, up to 30 years
• Electricity is generated wherever there is light, solar or artificial • PV operates even in cloudy weather conditions
• Modular or “custom-made” energy, can be designed for any application from watch to a multi-megawatt power plant
2.6 Disadvantage of photovoltaic (PV):
• PV cannot operate without light
• High initial costs that overshadow the low maintenance costs and lack of fuel costs
• Large area needed for large scale applications
• PV generates direct current: special DC appliances or inverters are needed in off-grid applications energy storage is needed, such as batteries.
2.7 Photovoltaic (PV) applications and market:
An overview of the different solar cell technologies that are used or being developed for two main solar cell applications, namely space and terrestrial applications. The conversion efficiency of solar cells used in space applications is the initial efficiency measured before the solar cells are launched into the space. This conversion efficiency is also referred to as the begin-of-life efficiency. Today's commercial PV systems in terrestrial applications convert sunlight into electricity with efficiency ranging from 7% to 17%. They are highly reliable and most producers give at least 20 years guarantee on module performance. In case of the thin-film solar cells the best conversion efficiency that has been achieved in laboratory is shown together with the conversion efficiency that is typical for commercial solar cells.
CHAPTER-3
SOLAR PATH OF THE SUN
3.1 Basics of Solar Radiation:
Radiation from the sun sustains life on earth and determines climate. The energy flow within the sun results in a surface temperature of around 5800 K, so the spectrum of the radiation from the sun is similar to that of a 5800 K blackbody with fine structure due to absorption in the cool peripheral solar gas.
3.2 Solar Constant and "Sun Value":
The irradiance of the sun on the outer atmosphere when the sun and earth are spaced at 1 AU - the mean earth/sun distance of 149,597,890 km - is called the solar constant. Currently accepted values are about 1360 W m-2(the NASA value given in ASTM E 490-73a is 1353 ±21 W m-2). The World Metrological Organization (WMO) promotes a value of 1367 W m-2. The solar constant is the total integrated irradiance over the entire spectrum (the area under the curve in Fig. 1 plus the 3.7% at shorter and longer wavelengths.
The irradiance falling on the earth's atmosphere changes over a year by about 6.6% due to the variation in the earth/sun distance. Solar activity variations cause irradiance changes of up to 1%.
For Solar Simulators, it is convenient to describe the irradiance of the simulator in “suns.” One “sun” is equivalent to irradiance of one solar constant.
Figure: 3.1 Spectrum of the radiation outside the earth’s atmosphere compared to spectrum of a 5800 K blackbody.
3.3 Extraterrestrial and Terrestrial Spectra: 3.3.1 Extraterrestrial Spectra:
Fig. 1 shows the spectrum of the solar radiation outside the earth's atmosphere. The range shown, 200 - 2500 nm, includes 96.3% of the total irradiance with most of the remaining 3.7% at longer wavelengths. Many applications involve only a selected region of the entire spectrum. In such a case, a "3 sun unit" has three times the actual solar irradiance in the spectral range of interest and a reasonable spectral match in this range.
Example
The model 91160 Solar Simulator has a similar spectrum to the extraterrestrial spectrum and has an output of 2680 W m-2. This is equivalent to 1.96 times 1367 W m-2so the simulator is a 1.96 sun unit.
3.3.2 Terrestrial Spectra
The spectrum of the solar radiation at the earth's surface has several components (see Fig. 2). Direct radiation comes straight from the sun, diffuse radiation is scattered from the sky and from the surroundings. Additional radiation reflected from the surroundings (ground or sea) depends on the local "albedo." The total ground radiation is called the global radiation. The direction of the target surface must be defined for global irradiance. For direct radiation
the target surface faces the incoming beam. All the radiation that reaches the ground passes through the atmosphere, which modifies the spectrum by absorption and scattering. Atomic and molecular oxygen and nitrogen absorb very short wave radiation, effectively blocking radiation with wavelengths <190 nm. When molecular oxygen in the atmosphere absorbs short wave ultraviolet radiation, it photodissociates. This leads to the production of ozone. Ozone strongly absorbs longer wavelength ultraviolet in the Hartley band from 200 - 300 nm and weakly absorbs visible radiation. The widely distributed stratospheric ozone produced by the sun's radiation corresponds to approximately a 3 mm layer of ozone at STP. The "thin ozone layer" absorbs UV up to 280 nm and (with atmospheric scattering) shapes the UV edge of the terrestrial solar spectrum. Water vapor, carbon dioxide, and to a lesser extent, oxygen, selectively absorb in the near infrared, (as indicated in Fig. 3). Wavelength dependent Rayleigh scattering and scattering from aerosols and other particulates, including water droplets, also change the spectrum of the radiation that reaches the ground
(and make the sky blue). For a typical cloudless atmosphere in summer and for zero zenith angle, the 1367 W m-2reaching the outer atmosphere is reduced to ca. 1050 W m-2direct beam radiation, and ca. 1120 W m-2global radiation on a horizontal surface at ground level.
Figure: 3.2 The total global radiation on the ground has direct, scattered and reflective components.
Figure: 3.3 Normally incident solar spectrum at sea level on a clear day. The dotted curve shows the extrarrestrial spectrum.
3.4 The Changing Terrestrial Solar Spectrum:
Absorption and scattering levels change as the constituents of the atmosphere change. Clouds are the most familiar example of change; clouds can block most of the direct radiation. Seasonal variations and trends in ozone layer thickness have an important effect on terrestrial ultraviolet level. The ground level spectrum also depends on how far the sun's radiation must pass through the atmosphere. Elevation is one factor. Denver has a mile (1.6 km) less atmosphere above it than does Washington, and the impact of the time of year on solar angle is important, but the most significant changes are due to the earth's rotation (see Fig. 4). At any location, the length of the path the
radiation must take to reach ground level changes as the day progresses. So not only are there the obvious intensity changes in ground solar radiation level during the day, going to zero at night, but the spectrum of the radiation changes through each day because of the changing absorption and scattering path length.
With the sun overhead, direct radiation that reaches the ground passes straight through the entire atmosphere, all of the air mass, overhead. We call this radiation "Air Mass 1 Direct" (AM 1D) radiation, and for standardization purposes we use a sea level reference site. The global radiation with the sun overhead is similarly called "Air Mass 1 Global" (AM 1G) radiation. Because it passes through no air mass, the extraterrestrial spectrum is called the "Air Mass
0" spectrum.
The atmospheric path for any zenith angle is simply described relative to the overhead air mass (Fig. 4). The actual path length can correspond to air masses of less than 1 (high altitude sites) to very high air mass values just before sunset. Our Oriel Solar Simulators use filters to duplicate spectra corresponding to air masses of 0, 1, 1.5 and 2, the values on which most comparative test work is based.
Figure: 3.4 The path length in units of Air Mass, changes with the zenith angle.
3.5 Standard Spectra:
Solar radiation reaching the earth's surface varies significantly with location, atmospheric conditions including cloud cover, aerosol content, and ozone layer condition, and time of day, earth/sun distance, solar rotation and activity. Since the solar spectra depend on so many variables, standard spectra have been developed to provide a basis for theoretical evaluation of the effects of solar radiation and as a basis for simulator design. These standard spectra start from a simplified (i.e. lower resolution) version of the measured extraterrestrial spectra, and use sophisticated models for the effects of the atmosphere to
calculate terrestrial spectra.
The most widely used standard spectra are those published by The Committee Internationale d'Eclaraige (CIE), the world authority on radiometeric and
photometric nomenclature and standards. The American Society for Testing and Materials (ASTM) publish three spectra - the AM 0, AM 1.5 Direct and AM 1.5 Global for a 37° tilted surface. The conditions for the AM 1.5 spectra were chosen by ASTM "because they are representative of average conditions in the 48 contiguous states of the United States". Fig. 5 shows typical differences in standard direct and global spectra. These curves are from the data in ASTM Standards, E 891 and E 892 for AM 1.5, a turbidity of 0.27 and a tilt of 37° facing the sun and a ground albedo of 0.2.
Figure: 3.5 Standard spectra
Table: 3.1 Power Densities of Published Standards
Solar Condition Standard Power Density (Wm-2) Total 250 - 2500 nm 250 - 1100 nm WMO Spectrum 1367 AM 0 ASTM E 490 1353 1302.6 1006.9
AM 1 CIE Publication 85, Table 2 969.7 779.4
AM 1.5 D ASTM E 891 768.3 756.5 584.7 AM 1.5 G ASTM E 892 963.8 951.5 768.6 AM 1.5 G CEI/IEC* 904-3 1000 987.2 797.5
** Integration by modified trapezoidal technique CEI = Commission Electro technique International IEC = International Electro technical Commission
The appearance of a spectrum depends on the resolution of the measurement and the presentation. Fig. 6 shows how spectral structure on a continuous background appears at two different resolutions. It also shows the higher resolution spectrum smoothed using Savitsky-Golay smoothing. The solar spectrum contains fine absorption detail that does not appear in our spectra. Here shows the detail in the ultraviolet portion of the World Metrological Organization's (WMO) extraterrestrial spectrum. Fig. 7 also shows a portion of the CEI AM 1 spectrum. The modeled spectrum shows none of the detail of the WMO spectrum, which is based on selected data from many careful measurements.
Figure: 3.6 Actual scan of a simulator with resolution under 2 nm; high resolution doesn’t enhance these Doppler broadened lines. Middle: Scan of same simulator with 10 nm resolution. Bottom: Smoothed version of top curve. We used repeated Savitsky-Golay smoothing.
Figure: 3.7 Comparison of the UV portion of the WMO measured solar spectrum and the modeled CIE AM 1 direct spectrum. All the modeled spectra, CIE or ASTM, used as standards, omit the fine details seen in measured spectrum.
3.6 Geometry of Solar Radiation:
The sun is a spherical source of about 1.39 million km diameter, at an average distance (1 astronomical unit) of 149.6 million km from earth. The direct portion of the solar radiation is collimated with an angle of approximately 0.53° (full angle), while the "diffuse" portion is incident from the hemispheric sky and from ground reflections and scatter. The "global" irradiation, the sum of the direct and diffuse components, is essentially uniform. Since there is a strong forward distribution in aerosol scattering, high aerosol loading of the atmosphere leads to considerable scattered radiation appearing to come from a small annulus around the solar disk, the solar aureole. This radiation mixed with the direct beam is called circumsolar radiation.
3.7 Dirunal and Annual Variation:
Figs. 9 and 10 show typical diurnal variations of global solar radiative flux. Actual half width and peak position of the curve shape depend on latitude and time of year. Fig. 9 shows a cloudless atmosphere. Fig. 10 shows the impact of clouds. Fig. 10 shows the global solar irradiance at solar noon measured in Arizona, showing the annual variation.
Figure: 3.9 Diurnal variations of global solar radiative flux on a sunny day.
Figure: 3.11 The global solar irradiance at solar noon measured in Arizona, showing the annual variation.
3.8 Solar Motion:
Solar motion is defined as the calculated motion of the Sun with respect to a specified reference frame. In practice, calculations of solar motion provide information not only on the Sun’s motion with respect to its neighbors in the Galaxy but also on the kinematic properties of various kinds of stars within the system.
Chapter-4
Solar tracking system
Tracking system for solar panels follow the path of the sun to maximize the exposure of the panels to solar radiation in order to convert sunlight to energy. In the case of a fixed solar collector the projection of the collector area into the plane perpendicular to the radiation direction, is given by the cosine of the angle of incidence (Fig. 1). The higher is the angle of incidence, the lower is the power. The solar tracker, a device that keeps photovoltaic or photo thermal panels in an optimum position perpendicular to the incident solar radiation during daylight hours, can increase the collected energy by up to 57%. Theoretical calculation of the energy surplus in the case of tracking collectors is as follows: assuming the maximum radiation intensity is I=1100 W-m falling on the area which is oriented perpendicularly to the direction of radiation. It is assumed, the day lengths t=12h=43000s as well as the night length and it is compared, the tracking collector which is all the time optimally oriented to the sun with the fixed collector which is oriented perpendicularly to the direction of radiation only at noon.
Figure 4.2 Single axis tracking system
Figure 4.3 Dual axis tracking system
4.1 Solar tracker:
A solar tracker is a device onto which solar panels are fitted which tracks the motion of the sun across the sky, thus ensuring that the maximum amount of sunlight strikes the panels throughout the day. There are many types of solar trackers, of varying costs, sophistication, and performance.
4.2 Type of solar tracker:
There are many types of solar trackers, of varying costs, sophistication, and performance. The two basic categories of trackers are single axis and dual axis.
4.2.1 Single axis solar tracker:
Solar trackers can either have a horizontal or a vertical axis. The horizontal type is used in tropical regions where the sun gets very high at noon, but the days are short. The vertical type is used in high latitudes where the sun does not get very high, but summer days can be very long. In concentrated solar power applications, single axis trackers are used with parabolic and linear Fresnel mirror designs.
Figure 4.4 Single axis solar tracker
4.2.1.1 Types of single axis solar tracker:
There are four types of single axis solar tracker:
4.2.1.2 Horizontal single axis tracker (HSAT):
The axis of rotation for horizontal single axis tracker is horizontal with respect to the ground. The posts at either end of the axis of rotation of a horizontal single axis tracker can be shared between trackers to lower the installation cost.
Field layouts with horizontal single axis trackers are very flexible. The simple geometry means that keeping all of the axes of rotation parallel to one another is all that is required for appropriately positioning the trackers with respect to one another.
Appropriate spacing can maximize the ratio of energy production to cost, this being dependent upon local terrain and shading conditions and the time-of-day value of the energy produced. Backtracking is one means of computing the disposition of panels.
Horizontal trackers typically have the face of the module oriented parallel to the axis of rotation. As a module tracks, it sweeps a cylinder that is rotationally symmetric around the axis of rotation.
In single axis horizontal trackers, a long horizontal tube is supported on bearings mounted upon pylons or frames. The axis of the tube is on a north-south line. Panels are mounted upon the tube, and the tube will rotate on its axis to track the apparent motion of the sun through the day.
Figure: 4.5Horizontal single axis trackers
4.2.1.3 Vertical single axis tracker (VSAT):
The axis of rotation for vertical single axis trackers is vertical with respect to the ground. These trackers rotate from East to West over the course of the day. Such trackers are more effective at high latitudes than are horizontal axis trackers.
Field layouts must consider shading to avoid unnecessary energy losses and to optimize land utilization. Also optimization for dense packing is limited due to the nature of the shading over the course of a year.
Vertical single axis trackers typically have the face of the module oriented at an angle with respect to the axis of rotation. As a module tracks, it sweeps a cone that is rotationally symmetric around the axis of rotation.
Figure: 4.6 Vertical single axis trackers
4.2.1.4 Tilted single axis tracker (TSAT):
All trackers with axes of rotation between horizontal and vertical are considered tilted single axis trackers. Tracker tilt angles are often limited to reduce the wind profile and decrease the elevated end height.
Field layouts must consider shading to avoid unnecessary losses and to optimize land utilization.
With backtracking, they can be packed without shading perpendicular to their axis of rotation at any density. However, the packing parallel to their axes of rotation is limited by the tilt angle and the latitude.
Tilted single axis trackers typically have the face of the module oriented parallelto the axis of rotation. As a module tracks, it sweeps a cylinder that is rotationally symmetric around the axis of rotation.
Figure: 4.7Tilted single axis trackers
4.2.1.5 Polar aligned single axis trackers (PASAT):
This method is scientifically well known as the standard method of mounting a telescope support structure. The tilted single axis is aligned to the polar star. It is therefore called a polar aligned single axis tracker (PASAT). In this particular
implementation of a tilted single axis tracker, the tilt angle is equal to the site latitude. This aligns the tracker axis of rotation with the earth’s axis of rotation.
Figure: 4.8Polar aligned single axis trackers
4.2.2 Dual axis solar tracker:
Solar trackers have both a horizontal and a vertical axis and thus they can track the sun's apparent motion virtually anywhere in the world. CSP applications using dual axis tracking include solar power towers and dish (Stirling engine) systems. Dual axis tracking is extremely important in solar tower applications due to the angle errors resulting from longer distances between the mirror and the central receiver located in the tower structure.
4.2.2.1 Types of duel axis solar tracker:
There are four types of single axis solar tracker:
4.2.2.2 Tip–tilt dual axis tracker (TTDAT):
A tip–tilt dual axis tracker is so-named because the panel array is mounted on the top of a pole. Normally the east-west movement is driven by rotating the array around the top of the pole. On top of the rotating bearing is a T- or H-shaped mechanism that provides vertical rotation of the panels and provides the main mounting points for the array. The posts at either end of the primary axis of rotation of a tip–tilt dual axis tracker can be shared between trackers to lower installation costs.
Other such TTDAT trackers have a horizontal primary axis and a dependent orthogonal axis. The vertical azimuthally axis is fixed. This allows for great flexibility of the payload connection to the ground mounted equipment because there is no twisting of the cabling around the pole.
Field layouts with tip–tilt dual axis trackers are very flexible. The simple geometry means that keeping the axes of rotation parallel to one another is all that is required for appropriately positioning the trackers with respect to one another. Normally the trackers would have to be positioned at fairly low density in order to avoid one tracker casting a shadow on others when the sun is low in the sky. Tip-tilt trackers can make up for this by tilting closer to horizontal to minimize up-sun shading and therefore maximize the total power being collected.
The axes of rotation of many tip–tilt dual axis trackers are typically aligned either along a true north meridian or an east west line of latitude.
Given the unique capabilities of the Tip-Tilt configuration and the appropriated controller totally automatic tracking is possible for use on portable platforms. The orientation of the tracker is of no importance and can be placed as needed.
Figure: 4.10Tip–tilt dual axis trackers
4.2.2.3 Azimuth-altitude dual axis tracker (AADAT):
An azimuth–altitude dual axis tracker has its primary axis vertical to the ground. The secondary axis is then typically normal to the primary axis. They are similar to tip-tilt systems in operation, but they differ in the way the array is rotated for daily tracking. Instead of rotating the array around the top of the pole, AADAT systems typically use a large ring mounted on the ground with the array mounted on a series of rollers. The main advantage of this arrangement is the weight of the array is distributed over a portion of the ring, as opposed to the single loading point of the pole in the TTDAT. This allows AADAT to support much larger arrays. Unlike the TTDAT, however, the AADAT system cannot be placed closer together than the diameter of the ring, which may reduce the system density, especially considering inter-tracker shading.
Chapter-5
Construction of microcontroller
based single axis solar tracker
5.1 Single axis solar trackers:
Single axis trackers have one degree of freedom that acts as an axis of rotation. The axis of rotation of single axis trackers is typically aligned along a true North meridian. It is possible to align them in any cardinal direction with advanced tracking algorithms.
There are several common implementations of single axis trackers. These include horizontal single axis trackers (HSAT), vertical single axis trackers (VSAT), tilted single axis trackers (TSAT) and polar aligned single axis trackers (PSAT). The orientation of the module with respect to the tracker axis is important when modeling performance.
5.2 Mechanical System:
As mentioned earlier, two separate prototypes were built and modified. The first prototype was constructed mainly from wood board, with a few metal pieces used as shafts and bearings. The wooden prototype used a DC motor to drive the system, then it was modified with a 50:1 worm gear drive. Finally, the acrylic prototype was built and was driven by a 180:1 worm gear drive. For each prototype the azimuth axis was designed and modified first, followed shortly by the altitude axis.
Table: 5.1 Specification of solar tracking system
Sl Design Aspect Specification
1 Weight 2.4 Kg (including the panel)
2 Watt 5-10 w
3 Size 40cm x 24cm x 15 cm
4 Material Bases- PVC pipe (20MM 3/4") Panel chassis - Plastic board
- (.55inch x .55inch)
5.3 Methodology:
This project is divided into two parts, hardware development and programming development. Figure 3.4 shows block diagram of the project.
Voltage regulator
Sensor Microcontroller Driver
DC Geared Motor
Solar panel Frame Axis Figure: 5.2 Block diagram of the project (single axis solar tracker)
Table: 5.2 List of Equipments:
Sl Name Capacity 1 Microcontroller PIC 16F84A
2 Oscillator 10 m-Hz
3 Transistor NPN BCF47
4 Resistor 56 k-ohm, 10 k-ohm, 1 k-ohm
5 Capacitor 22 PF
6 Relay 6 volt
7 Voltage regulator LM7805
8 Gear-motor
Yes Yes No No No Yes
Figure: 5.3 Flow chart of the project (single axis solar tracker)
Start
Take input from 1stand 2ndsensors
Rotate 80 degree forward (East to West)
Stop processing until LDR3>LDR2
Take input from 2ndand 3rdsensors
LDR3>LDR2 ?
Rotate 80 degree forward (East to West)
Get interrupt stop forward rotation
Reverse to initial stage
Stop processing until getting the input LDR2>LDR1 ?
5.4 Working principle:
The project is built using a balanced concept which is three signals from the different sensors are compared. Light Dependent Resistor (LDR) as a light sensor has been used. The three light sensors are separated by divider which will create shadow on one side of the light sensor if the solar panel is not perpendicular to the sun. For the controlling circuit, microcontroller PIC16F84A acts as a brain that controls the movement of the motor via relay. Data received from the sensors and processed by the microcontroller. The microcontroller will send a data to the Bi-directional DC-geared motor via relay to ensure solar panel is perpendicular towards the Sun. Relay controls the rotation of the motor either to rotate clockwise or anticlockwise. The solar panel that attached to the motor will be reacted according to the direction of the motor.
5.5 Description of the component:
5.5.1 Microcontroller:
A microcontroller is a compact standalone computer, optimized for control applications. Entire processor, memory and the I/O interfaces are located on a single piece of silicon so, it takes less time to read and write to external devices.
5.5.1.1 Use of Microcontroller:
Following are the reasons why microcontrollers are incorporated in control systems:
a) Cost: Microcontrollers with the supplementary circuit components are
much cheaper than a computer with an analog and digital I/O
b) Size and Weight: Microcontrollers are compact and light compared to
c) Simple applications: If the application requires very few number of I/O
and the code is relatively small, which do not require extended amount of memory and a simple LCD display is sufficient as a user interface, a microcontroller would be suitable for this application.
d) Reliability: Since the architecture is much simpler than a computer it is
less likely to fail.
e) Speed: All the components on the microcontroller are located on a
single piece of silicon. Hence, the applications run much faster than it does on a computer.
Table: 5.3 Description of pin number of Microcontroller (PIC 16F84A)
Pin Number Description
1 RA2 - Port A
2 RA3 - Port A
3 RA4/TOCK1 - Port A 4 MCLR - Master Clear Input
5 Vss - Ground 6 RB0/INT - Port B 7 RB1 - Port B 8 RB2 - Port B 9 RB3 - Port B 10 RB4 - Port B 11 RB5 - Port B 12 RB6 - Port B 13 RB7 - Port B
14 Vdd - Positive Power Supply 15 OSC2/CLKOUT - Oscillator Output 16 OSC1/CLKIN - Oscillator Input 17 RA0 - Port A
Figure: 5.6 Block Diagram of microcontroller (PIC 16F84A)
The PIC16F84 has a RISC architecture compared to Von-Neumann. In Harvard architecture, data bus and address bus are separate. Thus a greater flow of data is possible through the central processing unit, and of course, a greater speed of work. Separating a program from data memory makes it further possible for instructions not to have to be 8-bit words. PIC16F84 uses 14 bits for instructions which allows for all instructions to be one word instructions. It is also typical for Harvard architecture to have fewer instructions than von-Neumann's, and to have instructions usually executed in one cycle. Microcontrollers with Harvard architecture are also called "RISC microcontrollers". RISC stands for Reduced Instruction Set Computer. Microcontrollers with von-Neumann's architecture are called 'CISC microcontrollers'. Title CISC stands for Complex Instruction Set Computer
Since PIC16F84 is a RISC microcontroller, that means that it has a reduced set of instructions, more precisely 35 instructions. All of these instructions are executed in one cycle except for instructions where the Program Counter does not move to the next address (e.g. GOTO, RETURN etc).
The PIC16F84 belongs to a class of 8-bit microcontrollers of RISC architecture. Its general structure is shown in the following diagram, representing basic blocks.
Program memory (FLASH) for storing a written program
Since memory made in FLASH technology can be programmed and cleared more than once, it makes this microcontroller suitable for device development.
EEPROM data memory that needs to be saved when there is no supply.
It is usually used for storing important data that must not be lost if power supply suddenly stops. For instance, one such data is an assigned temperature in temperature regulators. If during a loss of power supply this data was lost, we would have to make the adjustment once again upon return of supply.
Thus our device looses on self-reliance.
RAM data memory used by a program during its execution. In RAM are stored
all inter results or temporary data during run time.
PORTA and PORTB are physical connections between the microcontroller and
the outside world. Port A has five, and port B has eight pins.
FREE-RUN TIMER is an 8-bit register inside a microcontroller that works
independently of the program. On every fourth clock of the oscillator it increments its value until it reaches the maximum (255), and then it starts counting over again from zero.
As we know the exact timing between each two increments of the timer contents, timer can be used for measuring time which is very useful with some devices.
CENTRAL PROCESSING UNIT has a role of connective element between
other blocks in the microcontroller. It coordinates the work of other blocks and executes the user program.
5.5.2 Gear-motor:
A small motor (ac induction, permanent magnet dc, or brushless dc) designed specifically with an integral (not separable) gear reducer (gearhead). The end shield on the drive end of the motor is designed to provide a dual function. The side facing the motor provides the armature/rotor bearing support and a sealing provision through which the integral rotor or armature shaft pinion passes. The other side of the end shield provides multiple bearing supports for the gearing itself, and a sealing and fastening provision for the gearhousing. This construction provides many benefits for a user and eliminates the guesswork of sizing a motor and gear reducer on your own.
5.5.2.1 Gear-motor Benefits:
Using the right sized motor and gear head combination for an application helps to prolong gear motor life and allows for optimum power management and power utilization. Traditionally, design engineers oversized motors and gear heads to add “safety factors” — Bodine “factory matched” gear motors consistently deliver rated performance.
Gear motors eliminate the need for motor/gear head couplings and eliminate any potential bearing alignment problems, common when a motor and gear head are bolted together by an end-user (separable gear heads). Misalignment can result in bearing failure due to fretting corrosion.
5.5.2.2 Application of Gear-motor:
What power can openers, garage door openers, stair lifts, rotisserie motors, timer cycle knobs on washing machines, power drills, cake mixers and electromechanical clocks have in common is that they all use various integrations of gear motors to derive a large force from a relatively small electric motor at a manageable speed. In industry, gear motor applications in jacks, cranes, lifts, clamping, robotics, conveyance and mixing are too numerous to count.
Figure: 5.7 Gear-motor
5.5.3 Voltage regulator
A circuit which is connected between the power source and a load, which provides a constant voltage despite variations in input voltage or output load
Figure: 5.8 Voltage regulator
5.5.4 Definition of relay:
A relay is an electromechanical device that uses an electromagnet to open or close a switch. The circuit that powers the electromagnet’s coil is completely separate from the circuit that is switched on or off by the relay’s switch, so it's
possible to use a relay whose coil requires just a few volts to turn a line voltage circuit on or off. 5.5.4.1 Types of relay: 1) Latching Relay 2) Reed Relay 3) Polarized Relay 4) Mercury-wetted Relay 5) Machine Tool Relay 6) Contactor Relay 7) Solid-state Relay
8) Overload Protection Relays
5.5.4.2 Application of relay:
Relays are remote control electrical switches that are controlled by another switch, such as a horn switch or a computer as in a power train control module. Relays allow a small current flow circuit to control a higher current circuit. Several designs of relays are in use today 3-pin, 4-pin, 5-pin and 6-pinsingle switch or duel switches.
Figure: 5.9 Relay
5.5.5 Resistor
Resistor is an electrical component that reduces the electric current. The resistor's ability to reduce the current is called resistance and is measured in
units of ohms (symbol: Ω). If we make an analogy to water flow through pipes, the resistor is a thin pipe that reduces the water flow.
.
Figure: 5.10 Symbol of resistor
5.5.6 Capacitor
Capacitor is an electronic component that stores electric charge. The capacitor is made of 2 close conductors (usually plates) that are separated by a dielectric material. The plates accumulate electric charge when connected to power source. One plate accumulates positive charge and the other plate accumulates negative charge. The capacitance is the amount of electric charge that is stored in the capacitor at voltage of 1 Volt. The capacitance is measured in units of Farad (F). The capacitor disconnects current in direct current (DC) circuits and short circuit in alternating current (AC) circuits.
Figure: 5.12 Symble of capacitor
Figure: 5.13 Picture of Capacitor
5.5.7 Transistor
A transistor is a basic electrical component that alters the flow of electrical current. Transistors are the building blocks of integrated circuits, such as computer processors, or CPUs. Modern CPUs contain millions of individual transistors that are microscopic in size.
Most transistors include three connection points, or terminals, which can connect to other transistors or electrical components. By modifying the current between the first and second terminals, the current between the second and third terminals is changed. This allows a transistor to act as a switch, which can turn a signal on or off. Since computers operate in binary, and a transistor's "on" or "off" state can represent a 1 or 0, transistors are suitable for performing
mathematical calculations. A series of transistors may also be used as alogic gate when performing logical operations.
5.5.7.1 Type of Transistor
Transistors are classified as either NPN or PNP according to the arrangement of their N and P materials. Their basic construction and chemical treatment is implied by their names, "NPN" or "PNP." That 2-3 is, an NPN transistor is formed by introducing a thin region of P-type material between two regions of N-type material. On the other hand, a PNP transistor is formed by introducing a thin region of N-type material between two regions of P-type material. Transistors constructed in this manner have two PN junctions, as shown in figure 2-2. One PN junction is between the emitter and the base; the other PN junction is between the collector and the base. The two junctions share one section of semiconductor material so that the transistor actually consists of three elements.
Figure: 5.14 Symble of Transistor
5.5.8 Push button switch:
A manual control device that opens or closes a circuit when pressed pushbuttons can be normally open or normally closed
Figure: 5.15 Push button switch
5.5.9 Oscillator:
An oscillator is a mechanical or electronic device that works on the principles of oscillation: a periodic fluctuation between two things based on changes in energy. Computers, clocks, watches, radios, and metal detectors are among the many devices that use oscillators.
In a computer, a specialized oscillator, called the clock, serves as a sort of pacemaker for the microprocessor. The clock frequency (or clock speed) is usually specified in megahertz (MHz), and is an important factor in determining the rate at which a computer can perform instructions.
5.5.9.1 Application of oscillators:
An oscillator is a circuit which produces a continuous output signal; thus it is called a signal generator. When the signal produced is a sine wave of constant amplitude and frequency, the oscillator circuit is called a sine wave generator. The oscillator can produce a square wave signal in digital logic families such as TTL, CMOS, or ECL.