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i
EXERCISE EQUIPMENT
FOR ELECTRICAL
ENERGY GENERATION
ii
ABSTRACT
The intention of this project is to design a renewable energy source based
around a piece of exercise equipmen...
iii
TABLE OF CONTENTS
CHAPTER NO: TITLE PAGE NO.
ABSTRACT v
LIST OF FIGURES ix
LIST OF TABLE xi
LIST OF GRAPH xii
1 INTROD...
iv
2.6 RECTIFIER 22
2.6.1 THREE PHASE DIODE RECTIFIER 23
2.6.2 RECTIFIER OUTPUT SMOOTHING 25
2.6.3 RECTIFIER OPERATION 27
...
v
4 IMPLEMENTATION AND RESUSLT 53
4.1 KEY REQUIREMENTS 53
4.2 ELECTRICAL SCHEMATIC DIAGRAM 54
4.3 ELEMENT SPECIFICATION 55...
vi
LIST OF FIGURES
FIGURE NO: TITLE PAGE NO.
1.1 PICTORIAL REPRESENTATION OF
OVERALL DESIGN 4
2.1 BLOCK DIAGRAM OF OVERALL...
vii
2.18 OPERATION DURING NEGATIVE HALF CYCLE 43
2.19 FULL WAVE BRIDGE RECTIFIER WITH
CAPACITOR FILTER 44
4.1 SCHEMATIC DI...
viii
LIST OF TABLES
TABLE NO. TITLE PAGE NO.
3.1 ENERGY CONSUMPTION RATES OF COMMON
HUMAN ACTIVITIES 48
3.2 MAXIMUM POWER ...
ix
LIST OF GRAPHS
GRAPH NO. TITLE PAGE NO.
1.1 FOSSIL FUEL CONSUMPTION OF DIFFERENT
COUNTRIES 3
4.1 VOLTAGE Vs SPEED 56
4....
1
CHAPTER - 1
INTRODUCTION
The field of energy conservation is becoming an increasingly
notable subject of research among ...
2
energy of the machine and converted it to electrical energy using a
generator-based system. The exercise equipment will ...
3
In terms of meeting the energy demand, data shows the high
dependence the world has overall on fossil fuels. Fossil fuel...
4
Statistics shown here illustrate how the world on average depends
majorly on fossil fuels to supply energy. The trend in...
5
electricity and charge a 12 volt battery, we obtain an output power of
approximately 60 watts – plenty of power for ligh...
6
CHAPTER- 2
LITERATURE REVIEW
2.1 A BRIEF HISTORY OF HUMAN POWER GENERATION
In 1817 Baron von Drais invented a walking ma...
7
of the '50s through the '70s, the 10-speed derailleur bikes which were
popular in the '70s (the derailleur had been inve...
8
Cranks and pedal power became one of the most efficient means
of coupling human power to applications. In the 19th centu...
9
Table 2:1 Energy Consumption Rates of Common Human Activities
Activity Power Consumed (w)
Sleeping 81
Sitting 116
Swimmi...
10
The obvious impracticality of this figure shows why the scope
thus far in human power generation has been limited to lo...
11
you provide pedal power to a 100 Watt television for one hour. Since
one Joule is equal to one Watts X Seconds you perf...
12
powered flight. The end goal of this initiative is to qualify such an
endeavor to be a competitive sport, possibly a pa...
13
Further, small-scale electromagnetic generators are a little harder to
manufacture but can produce power in the order o...
14
CHAPTER -3
DESIGN OF OVERALL PROJECT
3.1 BLOCK DIAGRAM
A simple block diagram of the overall project design is shown in...
15
inverter is made is made with MOSFET and driver circuit. The output of
the inverter is 12V AC supply with a frequency o...
16
DC voltage is not in pure form some A.C. components are in
there so for purification of it, Shunt capacitor filter circ...
17
available in scrap yards, they also tend to be less efficient in the output
of DC power compared to a dynamo.
Another d...
18
necessary to change the varying DC voltages produced from the varying
bicycle speed to a constant DC voltage for certai...
19
and electric motors are considered low-speed prime movers. The type of
prime mover plays an important part in the desig...
20
The bicycle is an efficient and robust method to convert between
the two types of energy. It is an efficient design tha...
21
power generation set-up. This factor comes into play further when
developing the motor for the bicycle design.
A pulley...
22
3.4.1 ALTERNATOR COMPONENTS
A typical rotating-field ac generator consists of an alternator and a
smaller dc generator ...
23
The exciter is a dc, shunt-wound, self-excited generator. The
exciter shunt field (2) creates an area of intense magnet...
24
Fig 3.4 Types of rotors used in alternators
The salient-pole rotor shown in figure 3.4, view B, is used in low-
speed a...
25
3.4.2 CHARACTERISTICS AND LIMITATIONS
Alternators are rated according to the voltage they are designed to
produce and t...
26
3.5 VOLTAGE REGULATOR
A voltage regulator circuit for an alternator includes voltage
responsive circuitry having a zene...
27
equalize only the voltage between dc generators, synchronizing forces
are required to equalize both voltage and speed (...
28
The DC output voltage from the half or full-wave rectifiers
contains ripple superimposed onto the DC voltage and that a...
29
condition. Resistor RS is selected so to limit the maximum current
flowing in the circuit.
With no load connected to th...
30
current. The zener voltage regulator consists of a current limiting
resistor RS connected in series with the input volt...
by a battery). In these applications the output of the rectifier is smoothed
by an electronic filter
Rectifier circuits ma...
Fig 3.8 Three phase AC input, half and full
For a three-phase full
average output voltage is
32
phase AC input, half and f...
3.6.2 RECTIFIER OUTPUT SMOOTHING
Rectifiers are normally used in circuits that require a steady
voltage to be supplied.To ...
34
For a given load, a larger capacitor reduces ripple but costs more
and creates higher peak currents in the transformer ...
35
filtering as well as the regulator, but this is not a common strategy. The
extreme of this approach is to dispense with...
36
• Two diodes are connected to each stator lead. One positive the
other negative.
• Because a single diode will only blo...
37
socket. It is pertinent to state that lead-acid batteries used in automobiles
are very good for this purpose as they pr...
38
or anode. Electrolytes allow ions to move between the electrodes and
terminals, which allows current to flow out of the...
39
controlled over-charging is typically as quickly as possible. To maintain
capacity on a fully charged battery, a consta...
40
charging time must be considered as one of the issues to this design.
Constant current charging is another simple yet e...
41
Inverter is a small circuit which will convert the direct current
(DC) to alternating current (AC). The power of a batt...
Fig 3.13
This circuit will provide a very stable Output AC Voltage.
Frequency of operation is determined by a pot and is n...
43
capable of quickly charging the input capacitance of the MOSFET
quickly before the potential difference is reached, cau...
44
inputs and 1 output. Working voltage range of IC is from 5V to 15V. It
can deliver approx.10mA at 12V but this can be r...
45
The battery supply is connected to the IC SG 3524 through the
inverter ON/OFF switch. The flip-flop converts the incomi...
46
The change over section is used to switch ON the inverter when
the AC mains supply is OFF and to switch OFF the inverte...
47
Thus a 12 V AC output voltage is transferred to the primary of
transformer; it is stepped up to 230V.
3.9 STEP-UP TRANS...
48
domain”, and transformers get their name from the fact that they
“transform” one voltage or current level into another....
3.10 ADDITIONAL SOURCE FOR THE BATTERY
When the exercise machine is not in use, the main supply is used
to charge the batt...
50
however, contains ripples, which can be smoothened by a filter circuit.
Power supplies can be ‘regulated’ or ‘unregulat...
51
3.10.2 SINGLE PHASE FULL-WAVE RECTIFIER
In many power supply circuits, the bridge rectifier is used. The
bridge rectifi...
52
The load and ground connections are removed because we are
concerned with the diode conditions only. In this circuit, d...
53
CHAPTER-4
IMPLEMENTATION AND RESULT
4.1 KEY REQUIREMENTS
The safety test is the most crucial aspect of the test plan an...
54
55
4.2.1 DIAGRAM EXPLANATION
The circuit consist of a bicycle powered 120VA alternator
and then when the bicycle is pedale...
56
4.3 ELEMENT SPECIFICATIONS
Our design will provide all of the following:
 Bicycle: A stationary bicycle with belt and ...
57
Fig 4.2 Voltage Vs Speed
The fig 4.2 shows the relation between speed and the voltage The
voltage coming out of the alt...
58
Fig 4.3 Current Vs Speed
The current of the alternator with the speed of the cycle (similar to
alternator speed) is sho...
59
CHAPTER 5
CONCLUSION
We design and implement an innovative exercise equipment
(stationary bicycle) to generate electric...
60
REFERENCES
[1] ABS Alaskan. (2006). DC to AC Power Inverters. Retrieved
December4, 2006, from http://www.absak.com/basi...
61
[11] Hutchison, F. H., 2007 “Facts About Electricity,” Clean- Energy.us:
News and Facts about Coal Gasification. http:/...
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Exercise equipment for electrical energy generation- A Report

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A report on the project topic Exercise equipment for electrical energy generation which may be helpful for engineering students

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Exercise equipment for electrical energy generation- A Report

  1. 1. i EXERCISE EQUIPMENT FOR ELECTRICAL ENERGY GENERATION
  2. 2. ii ABSTRACT The intention of this project is to design a renewable energy source based around a piece of exercise equipment. The energy expended in a typical workout at the gym is usually wasted in the mechanics of the equipment. This project harnessed the mechanical energy of the machine and converted it to electrical energy using a generator-based system. The exercise equipment, attached to the shaft of the generator. Thus produced electrical energy is used in powering a piece of equipment such as lamp or a computer while exercising. This report will introduce the project and present all applicable information regarding the design, development, and the final product. This project will help one develop engineering skills while learning about a clean way of generating electricity. The modern challenge faced with the global energy situation is the growing energy demand and the strong dependence on unsustainable fossil fuels. Another concurrent issue is the adverse health and socio-economic implications of adult obesity. This Human Power Generation project, which uses metabolized human energy to generate electrical power, could potentially address both these challenges.
  3. 3. iii TABLE OF CONTENTS CHAPTER NO: TITLE PAGE NO. ABSTRACT v LIST OF FIGURES ix LIST OF TABLE xi LIST OF GRAPH xii 1 INTRODUCTION 1 1.1 THE ENERGY CHALLENGE 2 1.2 SYSTEM DESIGN OVERVIEW 4 2 DESIGN OF OVERALL PROJECT 6 2.1 BLOCK DIAGRAM 6 2.2 PROJECT METHODS 9 2.3 PRIME MOVER 10 2.3.1 BICYCLE AND PULLEY 11 2.4 ALTERNATOR 13 2.4.1 ALTERNATOR COMPONENTS 14 2.4.2 CHARACTERSISTICS AND LIMITATION 17 2.5 VOLTAGE REGULATOR 18 2.5.1 ZENER DIODE REGULATOR 20
  4. 4. iv 2.6 RECTIFIER 22 2.6.1 THREE PHASE DIODE RECTIFIER 23 2.6.2 RECTIFIER OUTPUT SMOOTHING 25 2.6.3 RECTIFIER OPERATION 27 2.7 BATTERY 28 2.7.1 BATTERY CHARGER 30 2.7.2 CHARGING AND DISCHARGING PROCESS OF BATTERY 31 2.8 INVERTER 32 2.8.1 MOSFET POWER INVERTER 33 2.8.2 WORKING OF MOSFET POWER INVERTER 36 2.9 STEP-UP TRANSFORMER 39 2.10 ADDITIONAL SOURCE FOR THE BATTERY 41 2.10.1 DIODE RECTIFIER FOR POWER SUPPLY 41 2.10.2 SINGLE PHASE FULL WAVE RECTIFIER 43 3 LITERATURE REVIEW 45 3.1 A BRIEF HISTORY OF HUMAN POWER GENERATION 45 3.2 THE POTIENTIAL OF HUMAN POWER 47 3.3 CALORIES TO WATTS 49 3.4 MODERN APPLICATIONS 50
  5. 5. v 4 IMPLEMENTATION AND RESUSLT 53 4.1 KEY REQUIREMENTS 53 4.2 ELECTRICAL SCHEMATIC DIAGRAM 54 4.3 ELEMENT SPECIFICATION 55 4.4 PROJECT ANALYSIS 55 4.5 RESULT 57 5 CONCLUSION 58 REFERENCES
  6. 6. vi LIST OF FIGURES FIGURE NO: TITLE PAGE NO. 1.1 PICTORIAL REPRESENTATION OF OVERALL DESIGN 4 2.1 BLOCK DIAGRAM OF OVERALL PROJECT DESIGN 6 2.2 PRIME MOVER SETUP FOR ALTERNATOR 11 2.3 AC GENERATOR PICTORIAL AND SCHEMATIC DRAWING 14 2.4 TYPES OF ROTORS USED IN ALTERNATOR 16 2.5 ALTERNATOR WITH VOLTAGE REGULATOR 18 2.6 ZENER DIODE REGULATOR 20 2.7 THREE PHASE AC FULL WAVE RECTIFIER 23 2.8 THREE PHASE AC INPUT, HALF AND FULL WAVE RECTIFIED DC OUTPUT WAVEFORMS 24 2.9 RECTIFIER OUTPUT SMOOTHING GRAPH 25 2.10 RC FILTER RECTIFIER 25 2.11 RECTIFICATION CIRCUIT 27 2.12 BLOCK DIAGRAM OF INVERTER 33 2.13 SCHEMATIC DIAGRAM OF MOSFET INVERTER 33 2.14 STEP-UP TRANSFORMER 39 2.15 SINGLE-PHASE FULL WAVE RECTIFIER WITH FILTER CAPACITOR 41 2.16 BLOCK DIAGRAM OF REGULATED POWER SUPPLY 42 2.17 OPERATION DURING POSITIVE HALF CYCLE 43
  7. 7. vii 2.18 OPERATION DURING NEGATIVE HALF CYCLE 43 2.19 FULL WAVE BRIDGE RECTIFIER WITH CAPACITOR FILTER 44 4.1 SCHEMATIC DIAGRAM OF OVERALL DESIGN 54
  8. 8. viii LIST OF TABLES TABLE NO. TITLE PAGE NO. 3.1 ENERGY CONSUMPTION RATES OF COMMON HUMAN ACTIVITIES 48 3.2 MAXIMUM POWER GENERATION CAPABILITY FOR SOME HUMAN ACTIVITIES 48
  9. 9. ix LIST OF GRAPHS GRAPH NO. TITLE PAGE NO. 1.1 FOSSIL FUEL CONSUMPTION OF DIFFERENT COUNTRIES 3 4.1 VOLTAGE Vs SPEED 56 4.2 CURRENT Vs SPEED 57
  10. 10. 1 CHAPTER - 1 INTRODUCTION The field of energy conservation is becoming an increasingly notable subject of research among the scientific community today. The intention of this project is to build a straight forward human powered generator from a used bicycle and to use it to power light bulbs, blenders, cell phones, laptops, and other small appliances. This project will help one develop engineering skills while learning about a clean way of generating electricity. Over the past decade, scientists and engineers around the world have been designing unprecedented energy-harvesting systems, drawing power from a variety of sources. One of the most creative and unlimited sources available is the kinetic energy produced from human exercise. Although recent designs of energy-harvesting exercise equipment have been introduced into the market, these systems are costly and do not produce a noticeable output of power. These systems need to be improved and designed for maximum power output, cost-efficiency, and marketability. Engineered to be used for retrofitting an existing exercise machine, this project includes an efficient yet controllable power storage and distribution system. The objective of this project is to design a renewable energy source based around a piece of exercise equipment. Also, people who are interested in minimizing environmental impacts and those who want to preserve the environment will use this type of electrical energy generation thereby reducing the emission of CO2 to the atmosphere.The energy expended in a typical workout at the gym is usually wasted in the mechanics of the equipment. This project harnessed the mechanical
  11. 11. 2 energy of the machine and converted it to electrical energy using a generator-based system. The exercise equipment will be attached to the shaft of the generator. Thus produced electrical energy is used in powering a piece of equipment such as lamp or a computer while exercising. 1.1 THE ENERGY CHALLENGE The world’s energy consumption is at an all time high with the demand continuously increasing. This situation brings up several challenges that need to be addressed.  Depletion due to finite availability of non-renewable energy sources, e.g. fossil fuels  Environmental pollution, e.g. with coal use in power plants  Increasing population, especially in developing countries which lack resources for clean energy.  Global warming with the related climate changes and adverse implications These challenges have been reason for much controversy in the developed world; however, recent investigations have also shown a much more basic challenge of availability in the less developed parts of the world. Data from the World Bank obtained as recently as 2014 estimated that about 25.9% of the world’s population (greater than 1.81 billion people) has no access to electricity. Larger numbers include those that have very limited access to electricity. Further, most countries with the lowest values for percent of population with electricity also have low values of urban population percentage.
  12. 12. 3 In terms of meeting the energy demand, data shows the high dependence the world has overall on fossil fuels. Fossil fuels are known to be non-renewable, having formed over millions of years of decomposition of prehistoric biological forms such as plant matter and the dinosaurs. The rate at which modern society is consuming these resources is far quicker, however, risking the depletion of this resource. Furthermore, the manner in which the resource is consumed is known to produce pollutants (e.g. Carbon Monoxide (CO)) and green house gases (e.g. Carbon Dioxide (CO2)) in our environment. Carbon Dioxide emissions have been steadily growing through the combustion of fossil fuels as needed in transportation, power generation and otherwise. One of the main reasons why this is a critical problem is that the world heavily depends on these fossil fuels currently to feed its energy demands. Fig 1.1 illustrates the level and trends of fossil fuel use as compared to total energy consumption over time in a few countries and the world overall . Fig 1.1 Fossil fuel consumption of different countries
  13. 13. 4 Statistics shown here illustrate how the world on average depends majorly on fossil fuels to supply energy. The trend in this parameter is also of concern as the value has been stable around 80% for the past 15 years. The United States shows a slow decline but is still above the world average. The trend of the most populous countries, China and India, can also cause distress as the fossil fuel dependence is increasing at a rapid rate over time. In the case of China, the value has superseded that of the United States as of 2006. Therefore, it is established that with the various energy challenges faced today, renewable energy sources must be seriously investigated. Particularly, the feasibility of low-cost, low maintenance and simple methods of providing energy to remote areas should be studied. Such technology could not only help provide an alternative to fossil fuel in developed countries, but also serve the growing needs of developing countries in a responsible way. 1.2 SYSTEM DESIGN OVERVIEW Fig 1.2 Pictorial representation of overall design We designed and constructed an entirely unique electric generation system that fuses both form and function into a cost-effective and convenient solution. Using a stationary bicycle to generate
  14. 14. 5 electricity and charge a 12 volt battery, we obtain an output power of approximately 60 watts – plenty of power for lights, an amplifier, an iPod charger, and any unforeseen additional loads the student group may attach later. The system provides about 5 hours of fully-loaded use, and requires the equivalent for charging. The system is comprised of several subsystems that will work collectively to efficiently produce the desired 50 to 150 watts of power.  The first subsystem is the mechanical connection which is will transfer the kinetic energy from pedaling to the generator.  The second subsystem is the electrical generator. This subsystem transfers the rotational movement created when bicycle is in use to the rotor of a generator which will in turn output an AC voltage.  The third subsystem is the rectifier, which convert AC power to DC. The fourth subsystem,thebattery and the battery charger.  The Charge Controller adjusts the output to a single lead acid battery to optimize the use of the generated energy. This component will play a major factor in the efficiency of the system.  The fifth subsystem is the inverter which convert the 12V DC to 12 V AC.  A sixth subsystem is the step up transformer which step up the 12V AC to 230V AC supply.  The seventh and final subsystem is the additional power supply for the battery when bicycle is not in use, which consistsof single phase AC supply, rectifier and a step down transformer.
  15. 15. 6 CHAPTER- 2 LITERATURE REVIEW 2.1 A BRIEF HISTORY OF HUMAN POWER GENERATION In 1817 Baron von Drais invented a walking machine that would help him get around the royal gardens faster: two same-size in-line wheels, the front one steerable, mounted in a frame which you straddled. The device was propelled by pushing your feet against the ground, thus rolling yourself and the device forward in a sort of gliding walk. The machine became known as the Draisienne or hobby horse The next appearance of a two-wheeled riding machine was in 1865, when pedals were applied directly to the front wheel. This machine was known as the velocipede ("fast foot"), but was popularly known as the bone shaker, since it was also made entirely of wood, then later with metal tires, and the combination of these with the cobblestone roads of the day made for an extremely uncomfortable ride. In 1870 the first all metal machine appeared. (Previous to this metallurgy was not advanced enough to provide metal which was strong enough to make small, light parts out of.) The pedals were still attached directly to the front wheel with no freewheeling mechanism. Solid rubber tires and the long spokes of the large front wheel provided a much smoother ride than its predecessor. The front wheels became larger and larger as makers realized that the larger the wheel, the farther you could travel with one rotation of the pedals. Pedaling History has on display even the recent history of the bicycle in America that we are more familiar with: the "English 3-speed"
  16. 16. 7 of the '50s through the '70s, the 10-speed derailleur bikes which were popular in the '70s (the derailleur had been invented before the turn of the century and had been in more-or-less common use in Europe since), and of course the mountain bike of right now. There are also many oddball designs that never quite made it, including the Ingo. 1980-1991 A Los Angeles based company called Luz Co. produced 95% of the world's solar-based electricity. They were forced to shut their doors after investors withdrew from the project as the price of non-renewable fossil fuels declined and the future of state and federal incentives were not likely. The chairman of the board said it best: "The failure of the world's largest solar electric company was not due to technological or business judgment failures but rather to failures of government regulatory bodies to recognize the economic and environmental benefits of solar thermal generating plants”. Solar energy history played a big part in the way society evolved and will continue to do so. There is a renewed focus as more and more people see the advantages of solar energy and as it becomes more and more affordable. Human power has been instrumental in helping solve problems since ancient times. For example, all tools have historically been human powered. It is believed that the first human powered device to generate rotary motion was the potter’s wheel, around 3,500 B.C.E. Later, devices such as Archimedes screw allowed efficient transfer of water from one level to another. The Chinese, after 200 C.E., were found to use hand cranks to aid in textile manufacturing, metallurgy and agriculture. After the mid-15th century, the technique of incorporating flywheels to produce smooth motion proliferated, allowing devices such as the spinning wheel to gain popularity in Europe.
  17. 17. 8 Cranks and pedal power became one of the most efficient means of coupling human power to applications. In the 19th century, the bicycle’s use of pedals allowed an efficient means of self-transportation. In parallel with the invention of the electric dynamo in the 19th century, it is speculated that pedal power was used to generate electric power as early as then. However, with the burgeoning of the industrial revolution in the 19th century and forward, human society found other ways of powering their engineered applications. Particularly, the availability of cheap and plentiful electricity, powerful motors and disposable batteries can be attributed to the decrease in popularity of using human strength. Also, the ethical implications of having humans produce energy as punishment, as seen in some prison mills, further diminished the popularity of human sourced power. It would take until the latter half of the 20th century for science to seriously reinvestigate this resource. 2.2 THE POTENTIAL OF HUMAN POWER When the energy intake of humans is considered, a large potential seems apparent. Considering the standard 2000kcal of daily consumption (97W of power in, on average), humans take in about 8.368MJ or 2324Wh of energy every single day. This is approximately the same amount of energy stored in the typical car battery (2400Wh) . However, the expenditure of energy for common tasks is relatively high as well as seen in Table 2.1 Also; Table 2.2 shows some values for maximum power that can be captured as a result of human activity.
  18. 18. 9 Table 2:1 Energy Consumption Rates of Common Human Activities Activity Power Consumed (w) Sleeping 81 Sitting 116 Swimming 582 Sprinting 1630 Table 2.2 Maximum Power Generation Capability for some Human Activities Activity Maximum Human Power (w) Pushing button 0.64 Squeezing handle 12 Rotating crank 28 Riding bike 100 Hence, the available energy that can be captured over a short period of time is in reality quite limited. To replace just one of the largest capacity coal power plants in the United States (Arizona Public Service Co, Palo Verde, AZ) would require approximately the population of 2 New York City metro areas to be riding human power generating bicycle :
  19. 19. 10 The obvious impracticality of this figure shows why the scope thus far in human power generation has been limited to lower power applications such as consumer electronics Producing 1800 watts for a few seconds should be within the range of the best power lifters and perhaps for up to a minute. Remember 1 watt means applying a force of 1 newton through a distance of 1 meter in 1 second. So if you lifted 1 kg, that's 9.8 newtons of force, about 10newtons, for 1 meter in 1 second, that would be 10 watts. So lifting 180 kg, 1 meter high in 1 second would be 1800 watts. The best power lifters can do squats of several times their body weight for 1 rep. Let's say the power lifter weighed 100 kg, about 220 lbs. He might be able to do 3 times his weight for a single rep. That would be 300 kg. But remember he's actually raising his own weight as well. So he's actually lifting 4 times his weight, 400 kg for this one rep. For a male of average height, he might be raising this over a distance of 1 meter. So doing 1800 watts of power for one minute would be like giving this power lifter a weight of only 60 kg (for a total weight of 180 kg) and doing squats with this light weight for the high number of reps of 1 per second over one minute. This would be possible for a weight so much lighter than their usual 1 rep maximum weight. 2.3 CALORIES TO WATTS First keep in mind that Watts and Calories are two different units of measurement that can't be directly converted back and forth. However if you use Watt-Hours instead of just Watts you then have a way to convert to calories. Here are the steps: Convert Watt-Hours to Watt- Seconds (Joules), then convert Joules to Calories, then adjust Calories with human body efficiency factor. So for this example let's assume that
  20. 20. 11 you provide pedal power to a 100 Watt television for one hour. Since one Joule is equal to one Watts X Seconds you perform dimensional analysis and get: 100Watt-hours X (3600 seconds / 1 Hour) = 360,000 J Now use the conversion factor: 1 cal = 4.184 J to convert Joules to Calories 360,000 J / 4.184 = 86,042 Calories When you look at the label of Oreo cookies or other food items at the store, the term Calories is really (kilo-Calories). So you divide by 1000 to get 86 Calories. Assuming that your body is about 25% efficient when cycling you divide by 0.25: Calories burned running a 100 Watt Television for 1 hour = 86 / 0.25 = 344 which is about equivalent to one piece of pizza. 2.4 MODERN APPLICATIONS Today, human power has made sort of a comeback with many applications where it can be of use and the reason to investigate alternative energy. A novel feeling of empowerment is recognized when people are able to do things for which they had to rely on machines previously. So much so, that the idea of powering solely from human energy exists as a technical challenge. For example, the American Society of Mechanical Engineers (ASME) holds the Human Powered Vehicle Challenge (HPVC) competition annually for encouraging higher education students to construct and compete with single-driver prototypes power by the driver alone. Further, the Royal Aeronautical Society has various challenges for the Kramer’s prizes in human
  21. 21. 12 powered flight. The end goal of this initiative is to qualify such an endeavor to be a competitive sport, possibly a part of the Olympics. Human power has also been found to be uniquely good at providing energy generation in isolated situations. For example, the development of hand-operated axial flux generators which can be useful for dismounted soldiers, search and rescue operation in case of natural disasters, relief workers in remote regions and field scientists. The study demonstrates how 60W can be maintained from the generator for different applications while maintaining a lightweight design for portability. Further, provides a good example of applying human power in remote areas of developing countries. In 1991, at the time of the study, many rural parts of India lacked any access to electricity. Further, fossil fuel or solar/wind energy generation required skill in operation and maintenance along with monetary resources that were unavailable. Human energy was determined to be simple, dependable, required low capital, and reliable for the application of desalinating local water. The successful implementation of a pedal powered system in the rural area produced a sustainable 100W to power the desalination system. This let clean water be available to the people locally, avoiding the need to walk 2km daily as done previously. This localized generation of electricity has also made human power an excellent method for micro- power generation. Theoretical analyses have been done to show that brisk walking motion can produce up to 5-8W, adequate for basic wearable computing. Recent research shows the performance of three methods to perform this extraction. Summary of current progress in piezoelectric generator technology shows power generation capabilities of up to 8400μW.
  22. 22. 13 Further, small-scale electromagnetic generators are a little harder to manufacture but can produce power in the order of mW. The development of a electrostatic generator which uses microball movement induced by low frequency human motion to generate at least 40μW. Such output power may seem relatively negligible but it has potential in partially or completely removing the need for batteries, making portable designs lighter, smaller and longer lasting. This is especially promising for applications such as implantable and wearable electronics, ambient intelligence, condition monitoring devices, and wireless sensor networks. Hence, it is seen that human power generation has multiple applications in modern society. It can be useful when users are isolated as possible with natural disaster, military deployment or being in a remote area. It also provides for an intuitive, easy to implement and relatively low cost design which is particularly useful in rural areas of developing nations where skill in operating equipment and investment capital is limited. Acquisition of energy via no deliberate human effort is also possible which could be useful for various novel portable electronics applications. Furthermore, it can allow for power generation to be done socially, removing the feeling of deliberate effort while increasing the power output significantly. The thought of using human energy as an alternative and renewable energy source is gaining popularity to the level that businesses have formed around converting exercise equipment such as stationary bikes and ellipticals to electricity generators.
  23. 23. 14 CHAPTER -3 DESIGN OF OVERALL PROJECT 3.1 BLOCK DIAGRAM A simple block diagram of the overall project design is shown in Fig 3.1 Fig 3.1 Block diagram of overall project design The basic design for the bicycle powered generator is to have a bicycle on a fixed stand, and then when the bicycle is pedaled, the spinning motion of the rear tire is used to produce mechanical energy directly into a generator. The kinetic energy from the exercising machine is given to the alternator through chain and belt drive. The belt is directly coupled to the alternator, so while exercising alternator also rotate. DC supply is given to the alternator using a battery, thus the rotor produce flux. While exercising, the alternator starts to rotate and produce three phase AC supply. The three phase AC supply is convert into DC through a three phase bridge rectifier. The rectified DC supply is given to the voltage regulator. Voltage regulator regulates the voltage to 12V. This 12V is used to charge battery and the same DC supply is fed to an inverter. The
  24. 24. 15 inverter is made is made with MOSFET and driver circuit. The output of the inverter is 12V AC supply with a frequency of 50 Hz. This AC supply is step up to 230 V by using step up transformer. When the exercise machine is not used, the main supply is used to charge the battery. For that charging step down transformer and bridge rectifier is used. The output of the transformer is 12V AC. This 12 V AC is converted to DC by using diode bridge rectifier. The output from the diode rectifier is directly connected to the battery. So the battery also charges while the exercise machine is not in use. In our project, we are using a 40 W incandescent lamp as load. This project has various different design paths to complete our product while meeting the majority objectives. This means we will have to implement and compare our different designs to insure the best product based on our set of objectives. These paths have changed as we progressed through our project, and there were a few foreseen methods that we expand upon in the design section. The basic design for the bicycle powered generator is to have a bicycle on a fixed stand, and then when the bicycle is pedaled, the spinning motion of the rear tire is used to produce mechanical energy directly into a generator. Alternator is the device by which mechanical energy is converted into electrical energy. It is D.C. generator for generating D.C. voltage at output. Rectifier circuit It is a device which converts A.C. voltage into D.C. voltage. Some A.C. harmonics produced by D.C. generator with pulsating modulation of waves which is not in regular modulation, so for getting regular modulation of waves, rectifier circuit is used Filter circuit at the output of rectifier.
  25. 25. 16 DC voltage is not in pure form some A.C. components are in there so for purification of it, Shunt capacitor filter circuit is used. Filter is a circuit which minimizes of removed the undesirable A.C. component of the rectifier output allows only the D.C. component to reach at output. Charging circuit It is the circuit which is used for charging the discharged battery. Voltage limiting circuit:- It is also called as voltage regulator circuit. Here, for voltage regulation of output voltage, zener diode is used. Voltage regulator is the circuit which eliminates or reduced variations in the D.C. output voltage or rectifier and filter circuit are called Voltage Regulator. Battery It is the source of D.C. voltage. It is the device where we want to store the D.C. voltage or it gives the D.C. source whenever we want. Inverter we are using electronic inverter. The function of electronic inverter is to convert D.C. to A.C. In our project we are generating 12 volt D.C. supply to convert 12 volt D.C. to 230 volt A.C. with the help of electronic inverter unit. The function of inverter is to take the 12 volt D.C. and switching the 12 volt D.C. and give the step-up transformer convert 12 volt switching supply to 230 volt A.C. supply. It is most common part of inverter. If an AC voltage is produced, a full bridge rectifier will be necessary to produce the DC voltage. This DC voltage can then be used immediately or stored via a battery array. The first decision is selecting a bill of materials for each design path. This will help determine the ultimate product affordability. We must decide whether to use an alternator or dynamo to convert the bicycles mechanical energy to AC or DC, respectively. While an alternator is easier to find and purchase with many functioning units
  26. 26. 17 available in scrap yards, they also tend to be less efficient in the output of DC power compared to a dynamo. Another design factor that must be implemented and compared is the coupling of the bicycle wheel to either the alternator or dynamo rotor. One option is to use two contacting wheels to connect the two components. This option is a bit simpler to implement and take very little upkeep to maintain; however, the efficiency of the contact is relatively low due to slippage losses and frictional losses. A more efficient yet expensive design would be to have the wheel and the alternator/dynamo be connected via a rotary belt, similar to a car belt system. There are bound to be various other obstacles and design methods to be implemented as the project progresses, and will be observed and recorded as they occur. 3.2 PROJECT METHODS This project has various different design paths to complete our product while meeting the majority objectives. This means we will have to implement and compare our different designs to insure the best product based on our set of objectives. These paths have changed as we progressed through our project, and there were a few foreseen methods that we expand upon in the design section. The basic design for the bicycle powered generator is to have a bicycle on a fixed stand, and then when the bicycle is pedaled, the spinning motion of the rear tire is used to produce mechanical energy directly into a DC voltage. If an AC voltage is produced, a full bridge rectifier will be necessary to produce the DC voltage. This DC voltage can then be used immediately or stored via a battery array. If a constant DC voltage is required by the using a voltage regulator may be
  27. 27. 18 necessary to change the varying DC voltages produced from the varying bicycle speed to a constant DC voltage for certain utilities or battery array. The first decision is selecting a bill of materials for each design path. This will help determine the ultimate product affordability. We must decide whether to use an alternator or dynamo to convert the bicycles mechanical energy to AC or DC, respectively. While an alternator is easier to find and purchase with many functioning units available in scrap yards, they also tend to be less efficient in the output of DC power compared to a dynamo. Another design factor that must be implemented and compared is the coupling of the bicycle wheel to either the alternator or dynamo rotor. One option is to use two contacting wheels to connect the two components. This option is a bit simpler to implement and take very little upkeep to maintain; however, the efficiency of the contact is relatively low due to slippage losses and frictional losses. A more efficient yet 15 expensive design would be to have the wheel and the alternator/dynamo be connected via a rotary belt, similar to a car belt system. There are bound to be various other obstacles and design methods to be implemented as the project progresses, and will be observed and recorded as they occur. 3.3 PRIME MOVER All generators, large and small, ac and dc, require a source of mechanical power to turn their rotors. This source of mechanical energy is called a prime mover. Prime movers are divided into two classes for generators-high-speed and low-speed. Steam and gas turbines are high-speed prime movers, while internal-combustion engines, water,
  28. 28. 19 and electric motors are considered low-speed prime movers. The type of prime mover plays an important part in the design of alternators since the speed at which the rotor is turned determines certain characteristics of alternator construction and operation. Fig 3.2 Prime Mover Setup for Alternator 3.3.1 BICYCLE AND PULLEY A bicycle is designed to convert human energy into mechanical energy for transportation purposes. The mechanical energy is then translated into electrical energy through the use of a drive train turning a motor. To maximize the efficiency of both conversions is essential to obtaining the maximum power output. The first conversion is from human energy or muscle energy into mechanical energy.
  29. 29. 20 The bicycle is an efficient and robust method to convert between the two types of energy. It is an efficient design that provides seating for the user as well as pedals and drive train that are easily activated. There are few moving parts and the simplicity of design is proven. Pedaling is the most efficient way of utilizing power from human muscles. Pedal power enables a person to drive devices at the same or higher rate as that achieved by hand cranking, but with far less effort and fatigue. The human musculature is concentrated in our legs and the bicycle set-up allows for harnessing the maximum output. The stationary power generation on bicycles has been skipped over in past research but with the rising cost of other power generation, reliance on human power generation will become more important; furthermore, the bicycle is a universal symbol of transportation in all types of countries especially developing ones. We can find bicycles everywhere and the robustness of the simple mechanical system makes the learning curve essentially zero. The rotational nature of the bicycle drive train or more specifically the pedals is a steady style of movement. The constant driving of the pedals become more constant when reaching the drive train since there is rotational inertia to smooth out any subtle changes in the speed. The rear wheel therefore becomes an ideal prime mover for electrical generation; we would need to connect an alternator and rear wheel though either direct contact or a belt system. The user is able to start softly and increase the resistance as momentum is gained. When the bicycle stabilizes and gains more speed, then the user down-shift thereby increasing perceived resistance and outputs more power. The same approach can be used by the user of our stationary
  30. 30. 21 power generation set-up. This factor comes into play further when developing the motor for the bicycle design. A pulley is a wheel on an axle that is designed to support movement of a cable or belt along its circumference. Pulleys are used in a variety of ways to lift loads, apply forces, and to transmit power. Round belts Round belts are a circular cross section belt designed to run in a pulley with a 60 degree V-groove. Round grooves are only suitable for idler pulleys that guide the belt, or when (soft) O-ring type belts are used. 3.4 ALTERNATOR Here the alternator is used to charge the battery and to power the electrical system when the bicycle is pedaling. The last practical option to implement for the bicycle system was to use a standard car alternator. This seems to be the most reasonable motor for the design, as car alternators are widely available worldwide for relatively low costs when purchased as a used part. An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature. Occasionally, a linear alternator or a rotating armature with a stationary magnetic field is used. In principle, any AC electrical generator can be called an alternator, but usually the term refers to small rotating machines driven by automotive and other internal combustion engines. An alternator that uses a permanent magnet for its magnetic field is called a magneto. The alternator consists of two main parts, rotor and the stator.
  31. 31. 22 3.4.1 ALTERNATOR COMPONENTS A typical rotating-field ac generator consists of an alternator and a smaller dc generator built into a single unit. The output of the alternator section supplies alternating voltage to the load. The only purpose for the dc exciter generator is to supply the direct current required to maintain the alternator field. This dc generator is referred to as the exciter. A typical alternator is shown in fig 3.3 view A; figure 3.3, view B, is a simplified schematic of the generator. Fig 3.3 AC generator pictorial and schematic drawings.
  32. 32. 23 The exciter is a dc, shunt-wound, self-excited generator. The exciter shunt field (2) creates an area of intense magnetic flux between its poles. When the exciter armature (3) is rotated in the exciter-field flux, voltage is induced in the exciter armature windings. The output from the exciter commutator (4) is connected through brushes and slip rings (5) to the alternator field. Since this is direct current already converted by the exciter commutator, the current always flows in one direction through the alternator field (6). Thus, a fixed-polarity magnetic field is maintained at all times in the alternator field windings. When the alternator field is rotated, its magnetic flux is passed through and across the alternator armature windings (7). The armature is wound for a three-phase output, which will be covered later in this chapter. Remember, a voltage is induced in a conductor if it is stationary and a magnetic field is passed across the conductor, the same as if the field is stationary and the conductor is moved. The alternating voltage in the ac generator armature windings is connected through fixed terminals to the ac load. There are two types of rotors used in rotating-field alternators. They are called the turbine-driven and salient-pole rotors. As you may have guessed, the turbine-driven rotor shown in Fig 3.4 , view A, is used when the prime mover is a high-speed turbine. The windings in the turbine-driven rotor are arranged to form two or four distinct poles. The windings are firmly embedded in slots to withstand the tremendous centrifugal forces encountered at high speeds.
  33. 33. 24 Fig 3.4 Types of rotors used in alternators The salient-pole rotor shown in figure 3.4, view B, is used in low- speed alternators. The salient-pole rotor often consists of several separately wound pole pieces, bolted to the frame of the rotor. If you could compare the physical size of the two types of rotors with the same electrical characteristics, you would see that the salient- pole rotor would have a greater diameter. At the same number of revolutions per minute, it has a greater centrifugal force than does the turbine-driven rotor. To reduce this force to a safe level so that the windings will not be thrown out of the machine, the salient pole is used only in low-speed designs.
  34. 34. 25 3.4.2 CHARACTERISTICS AND LIMITATIONS Alternators are rated according to the voltage they are designed to produce and the maximum current they are capable of providing. The maximum current that can be supplied by an alternator depends upon the maximum heating loss that can be sustained in the armature. This heating loss (which is an I2 R power loss) acts to heat the conductors, and if excessive, destroys the insulation. Thus, alternators are rated in terms of this current and in terms of the voltage output - the alternator rating in small units is in volt-amperes; in large units it is kilovolt-amperes. Once the finger poles and shaft are removed, the coil of the rotor can be rewound with thinner wire more times. From Farraday’s equation, , we find that as N (number of turns) increases, ε (electromagnetic force) increases proportionally. With the higher EMF, we produce more power from less rotor rotations. In other words, with a rewrapped rotor we can produce more power with lower RPMs. While more current will be produced at lower RPMs this is because the EMF is much bigger, which in turn will give the users another problem, the EMF-produced resistance. An EMF in a motor is not a problem until you are the one actually supplying the rotation of the shaft. A higher EMF means the user will experience a higher resistance in their pedaling. This ―inductance hump of starting to pedal will tire the user greatly if a full field is being produced by the stator. To resolve this issue a few different ideas were implemented to reduce the pedaling resistance in the alternator.
  35. 35. 26 3.5 VOLTAGE REGULATOR A voltage regulator circuit for an alternator includes voltage responsive circuitry having a zener diode. The regulator will maintain a pre-determined charging system voltage level. When the system voltage decreases the regulator strengthens the magnetic field and thereby increases the alternator output voltage. When the system voltage increases the regulator weakens the magnetic field and thereby decreases the alternator output voltage. Fig 3.5 Alternator with voltage regulator Zener diodes are especially used on applications with sensitive electronic components. These can prevent major damage caused by voltage peaks due to sudden discharges. In 12V systems, Zener diodes with a voltage range 24V - 32V are used and in 28V systems the range is 36V - 44V. When ac generators are operated in parallel, frequency and voltage must both be equal. Where a synchronizing force is required to
  36. 36. 27 equalize only the voltage between dc generators, synchronizing forces are required to equalize both voltage and speed (frequency) between ac generators. On a comparative basis, the synchronizing forces for ac generators are much greater than for dc generators. When ac generators are of sufficient size and are operating at unequal frequencies and terminal voltages, serious damage may result if they are suddenly connected to each other through a common bus. To avoid this, the generators must be synchronized as closely as possible before connecting them together. The output voltage of an alternator is best controlled by regulating the voltage output of the dc exciter, which supplies current to the alternator rotor field. This is accomplished as shown in Fig 2.5, by a zener diode regulator of a 28 volt system connected in the field circuit of the exciter. The zener diode regulator controls the exciter field current and thus regulates the exciter output voltage applied to the alternator field. The only difference between the dc system and the ac system is that the voltage coil receives its voltage from the alternator line instead of the dc generator. In this arrangement, a three phase, step down transformer connected to the alternator voltage supplies power to a three phase, full wave rectifier. The 28 volt, dc output of the rectifier is then applied to the zener diode voltage regulator. Changes in alternator voltage are transferred through the transformer rectifier unit to the zener diode. This controls the exciter field current and the exciter output voltage. The exciter voltage antihunting or damping transformer is similar to those in dc systems and performs the same function.
  37. 37. 28 The DC output voltage from the half or full-wave rectifiers contains ripple superimposed onto the DC voltage and that as the load value changes so to does the average output voltage. By connecting a simple zener stabilizer circuit as shown below across the output of the rectifier, a more stable output voltage can be produced. 3.5.1 ZENER DIODE REGULATOR Zener Diodes can be used to produce a stabilized voltage output with low ripple under varying load current conditions. By passing a small current through the diode from a voltage source, via a suitable current limiting resistor, the zener diode will conduct sufficient current to maintain a voltage drop of output voltage. Fig 3.6 Zener Diode Regulator In the Fig 3.6, the resistor, RS is connected in series with the zener diode to limit the current flow through the diode with the voltage source, VS being connected across the combination. The stabilized output voltage Vout is taken from across the zener diode. The zener diode is connected with its cathode terminal connected to the positive rail of the DC supply so it is reverse biased and will be operating in its breakdown
  38. 38. 29 condition. Resistor RS is selected so to limit the maximum current flowing in the circuit. With no load connected to the circuit, the load current will be zero, ( IL = 0 ), and all the circuit current passes through the zener diode which in turn dissipates its maximum power. Also a small value of the series resistor RS will result in a greater diode current when the load resistance RL is connected and large as this will increase the power dissipation requirement of the diode so care must be taken when selecting the appropriate value of series resistance so that the zener’s maximum power rating is not exceeded under this no-load or high- impedance condition. The load is connected in parallel with the zener diode, so the voltage across RL is always the same as the zener voltage, ( VR = VZ ). There is a minimum zener current for which the stabilization of the voltage is effective and the zener current must stay above this value operating under load within its breakdown region at all times. The upper limit of current is of course dependent upon the power rating of the device. The supply voltage VS must be greater than VZ. One small problem with zener diode stabilizer circuits is that the diode can sometimes generate electrical noise on top of the DC supply as it tries to stabilize the voltage. Normally this is not a problem for most applications but the addition of a large value decoupling capacitor across the zener’s output may be required to give additional smoothing. Then to summarize a little. A zener diode is always operated in its reverse biased condition. A voltage regulator circuit can be designed using a zener diode to maintain a constant DC output voltage across the load in spite of variations in the input voltage or changes in the load
  39. 39. 30 current. The zener voltage regulator consists of a current limiting resistor RS connected in series with the input voltage VS with the zener diode connected in parallel with the load RL in this reverse biased condition. The stabilized output voltage is always selected to be the same as the breakdown voltage VZ of the diode. 3.6 RECTIFIER Rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification. Physically, rectifiers take a number of forms, including vacuum tube diodes, mercury-arc valves, copper and selenium oxide rectifiers, semiconductor diodes, silicon-controlled rectifiers and other silicon-based semiconductor switches. Historically, even synchronous electromechanical switches and motors have been used. Early radio receivers, called crystal radios, used a cat's whisker of fine wire pressing on a crystal of galena (lead sulfide) to serve as a point- contact rectifier or crystal detector. Rectifiers have many uses, but are often found serving as components of DC power supplies and high-voltage direct current power transmission systems. Rectification may serve in roles other than to generate direct current for use as a source of power. Because of the alternating nature of the input AC sine wave, the process of rectification alone produces a DC current that, though unidirectional, consists of pulses of current. Many applications of rectifiers, such as power supplies for radio, television and computer equipment, require a steady constant DC current (as would be produced
  40. 40. by a battery). In these applications the output of the rectifier is smoothed by an electronic filter Rectifier circuits may be single the most common number of phas domestic equipment are single very important for industrial applications and for the transmission of energy as DC (HVDC 3.6.1 THREE PHASE DIODE RECTIFIER Single-phase rectifiers are commonly used for power supplies for domestic equipment. However, for most industrial and high applications, three-phase phase rectifiers, three circuit, a full-wave circuit using a center wave bridge circuit. Fig 3.7 31 ). In these applications the output of the rectifier is smoothed electronic filter (usually a capacitor) to produce a steady current. Rectifier circuits may be single-phase or multi-phase (three being the most common number of phases). Most low power rectifiers for domestic equipment are single-phase, but three-phase rectification is very important for industrial applications and for the transmission of HVDC). HREE PHASE DIODE RECTIFIER phase rectifiers are commonly used for power supplies for domestic equipment. However, for most industrial and high phase rectifier circuits are the norm. As with single phase rectifiers, three-phase rectifiers can take the form of a half wave circuit using a center-tapped transformer, or a full 7 Three phase AC full-wave rectifier ). In these applications the output of the rectifier is smoothed (usually a capacitor) to produce a steady current. phase (three being es). Most low power rectifiers for phase rectification is very important for industrial applications and for the transmission of phase rectifiers are commonly used for power supplies for domestic equipment. However, for most industrial and high-power rectifier circuits are the norm. As with single- phase rectifiers can take the form of a half-wave tapped transformer, or a full- rectifier
  41. 41. Fig 3.8 Three phase AC input, half and full For a three-phase full average output voltage is 32 phase AC input, half and full-wave rectified DC output waveforms phase full-wave diode rectifier, the ideal, no average output voltage is ......(2.1) wave rectified DC output the ideal, no-load
  42. 42. 3.6.2 RECTIFIER OUTPUT SMOOTHING Rectifiers are normally used in circuits that require a steady voltage to be supplied.To provide a steady DC output. The raw rectified DC requires a smoothing be smoothed so that it can be used to power electronics circuits without large levels of voltage variation. Fig 3 Producing steady DC from a rectified AC supply requires a smoothing circuit or a reservoir capacitor the rectifier. There is still an supply frequency for a half where the voltage is not completely smoothed. 33 RECTIFIER OUTPUT SMOOTHING Rectifiers are normally used in circuits that require a steady voltage to be supplied.To provide a steady DC output. The raw rectified DC requires a smoothing capacitor circuit to enable the rectified DC to be smoothed so that it can be used to power electronics circuits without large levels of voltage variation. Fig 3.9 Rectifier Output Smoothing Graph roducing steady DC from a rectified AC supply requires a filter. In its simplest form(Fig 3.10) this can be just reservoir capacitor or smoothing capacitor, placed at the DC output of the rectifier. There is still an AC ripple voltage component at the power supply frequency for a half-wave rectifier, twice that for full where the voltage is not completely smoothed. Fig 3.10 RC-Filter Rectifier Rectifiers are normally used in circuits that require a steady voltage to be supplied.To provide a steady DC output. The raw rectified capacitor circuit to enable the rectified DC to be smoothed so that it can be used to power electronics circuits without roducing steady DC from a rectified AC supply requires a this can be just or smoothing capacitor, placed at the DC output of voltage component at the power rectifier, twice that for full-wave,
  43. 43. 34 For a given load, a larger capacitor reduces ripple but costs more and creates higher peak currents in the transformer secondary and in the supply that feeds it. The peak current is set in principle by the rate of rise of the supply voltage on the rising edge of the incoming sine-wave, but in practice it is reduced by the resistance of the transformer windings. In extreme cases where many rectifiers are loaded onto a power distribution circuit, peak currents may cause difficulty in maintaining a correctly shaped sinusoidal voltage on the ac supply. To limit ripple to a specified value the required capacitor size is proportional to the load current and inversely proportional to the supply frequency and the number of output peaks of the rectifier per input cycle. The load current and the supply frequency are generally outside the control of the designer of the rectifier system but the number of peaks per input cycle can be affected by the choice of rectifier design. A half-wave rectifier only gives one peak per cycle, and for this and other reasons is only used in very small power supplies. A full wave rectifier achieves two peaks per cycle, the best possible with a single- phase input. For three-phase inputs a three-phase bridge gives six peaks per cycle. Higher numbers of peaks can be achieved by using transformer networks placed before the rectifier to convert to a higher phase order. To further reduce ripple, a capacitor-input filter can be used. This complements the reservoir capacitor with a choke (inductor) and a second filter capacitor, so that a steadier DC output can be obtained across the terminals of the filter capacitor. The regulator serves both to significantly reduce the ripple and to deal with variations in supply and load characteristics. It would be possible to use a smaller reservoir capacitor and then apply some
  44. 44. 35 filtering as well as the regulator, but this is not a common strategy. The extreme of this approach is to dispense with the reservoir capacitor altogether and put the rectified waveform straight into a choke-input filter. The advantage of this circuit is that the current waveform is smoother and consequently the rectifier no longer has to deal with the current as a large current pulse, but instead the current delivery is spread over the entire cycle. The disadvantage, apart from extra size and weight, is that the voltage output is much lower – approximately the average of an AC half-cycle rather than the peak. 3.6.3 RECTIFIER OPERATION Fig 3.11 rectification circuit
  45. 45. 36 • Two diodes are connected to each stator lead. One positive the other negative. • Because a single diode will only block half the the AC voltage. • Six or eight diodes are used to rectify the AC stator voltage to DC voltage. • Diodes used in this configuration will redirect both the positive and negative polarity signals of the AC voltage to produce DC voltage. This process is called ‘Full - Wave Rectification’. At first you can see current pass through to the rectifier as it goes to the battery. In the second, you can see the return path. Now, current passes through to the rectifier however, this time current has the opposite polarity. In second circuit you can see the new return path. Even though it enters the rectifier at a different location, current goes to the battery in the same direction. 3.7 BATTERY Battery is essential to supply DC power for the alternator rotor and for the storage of generated power. An electric battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. Each cell contains a positive terminal, or cathode, and a negative terminal, or anode. Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to perform work. Battery we used is 12V, 10 Ah rating. The battery is a two-terminal device that provides DC supply to the inverter section when the AC mains are not available. This DC is then converted into 220V AC supply and output at the inverter output
  46. 46. 37 socket. It is pertinent to state that lead-acid batteries used in automobiles are very good for this purpose as they provide good quality power for a long duration and can be recharged once the power stored in them are consumed. The backup time provided by the inverter depends on the battery type and its current capacity Primary (single-use or disposable) batteries are used once and discarded; the electrode materials are irreversibly changed during discharge. Common examples are the alkaline battery used for flashlights and a multitude of portable devices. Secondary (rechargeable batteries) can be discharged and recharged multiple times; the original composition of the electrodes can be restored by reverse current. Examples include the lead-acid batteries used in vehicles and lithium ion batteries used for portable electronics. The battery was selected based on the amount of time we wanted to operate the system at full load. As mentioned in the specifications, we wanted to be able to power the lights. Fulfilling the 12 V DC battery requirements, we found a unit from Universal Battery with 18 Ah. If the battery is discharged to 50% at most, this battery leaves us with 9 Ah. Our load of lighting, music, and an iPod charger uses about 20 watts, but with an alternative appliance connected (e.g. phone), the total power consumed could be estimated at 25 watts. With a 12 VDC battery and a 25 W load, we have about 2 A of current, which gives us about 4.5 hours of use at full load – this is consistent with our design specifications. The exact battery we selected is UB12180 (12V 10Ah). An electric battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. Each cell contains a positive terminal, or cathode, and a negative terminal,
  47. 47. 38 or anode. Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to perform work. A lead-acid battery charger is most popular though it will very large size than others battery type. But them have advantage are : cheap, easy to buy and long life if correctly uses. 3.7.1 BATTERY CHARGER A battery charger is a device used to put energy into a cell or (rechargeable) battery by forcing an electric current through it. Lead- acid battery chargers typically have two tasks to accomplish. The first is to restore capacity, often as quickly as practical. The second is to maintain capacity by compensating for self discharge. In both instances optimum operation requires accurate sensing of battery voltage. When a typical lead-acid cell is charged, lead sulphate is converted to lead on the battery’s negative plate and lead dioxide on the positive plate. Over-charge reactions begin when the majority of lead sulphate has been converted, typically resulting in the generation of hydrogen and oxygen gas. At moderate charge rates, most of the hydrogen and oxygen will recombine in sealed batteries. In unsealed batteries however, dehydration will occur. The onset of over-charge can be detected by monitoring battery voltage. Over charge reactions are indicated by the sharp rise in cell voltage. The point at which over-charge reactions begin is dependent on charge rate, and as charge rate is increased, the percentage of returned capacity at the onset of over-charge diminishes. For overcharge to coincide with 100% return of capacity, the charge rate must typically be less than 1/100 amps of its amp- hour capacity. At high charge rates,
  48. 48. 39 controlled over-charging is typically as quickly as possible. To maintain capacity on a fully charged battery, a constant voltage is applied. The voltage must be high enough to compensate for self discharge, yet not too high as to cause excessive over-charging. 3.7.2 CHARGING AND DISCHARGING OF BATTERY Charging a lead acid battery is a matter of replenishing the depleted supply of energy that the battery had lost during use. This replenishing process can be accomplished with several different charger implementations: “constant voltage charger”, “constant current charger” or a “multistage constant voltage/current charger. Each of these approaches has its advantages and disadvantages that need to be compared and weighed to see which one would be the most practical and realistic to fit with our requirements. Constant voltage charging is one of the most common charging methods for lead acid batteries. The idea behind this approach is to keep a constant voltage across the terminals of the battery at all times. Initially, a large current will be drawn from the voltage source, but as the battery charges and increases its internal voltage, the current will slowly fold and decays exponentially. When the battery is brought up to a potential full charge, which is usually considered around 13.8V, the charging voltage is dropped down to a lower value that will provide a trickle charge to maintain the battery as long as it is plugged into the charger. The best characteristic of this method is that it provides a way to return a large bulk of the charge into the battery very fast. The drawback is that to complete a full charge would take a much longer time since the current is exponentially decreased as the battery charges. A prolonged
  49. 49. 40 charging time must be considered as one of the issues to this design. Constant current charging is another simple yet effective method for charging lead acid batteries. A current source is used to drive a uniform current through the battery in a direction opposite of discharge. This can be analogous to pouring water into a bucket with a constant water flow, no matter how full the bucket is. Constant current sources are not very hard to implement; therefore, the final solution would require a very simple design. There is a major drawback to this approach. Since the battery is always being pushed at a constant rate, when it is close to being fully charged, the charger would force extra current into the battery, causing overcharge. The ability to harness this current is the key to a successful charger. By monitoring the voltage on the battery, the charge level can be determined, and at a certain point, the current source would need to be folded back to only maintain a trickle charge and prevent overcharging. When the battery is connected to the external load, the chemical changes take place in reverse direction, during which the absorbed energy is released as electrical energy and supplied to the load. Thus the 12V DC output of the battery is fed to the MOSFET inverter. 3.8 INVERTER The inverter should be chosen so that its input voltage matches that of the storage battery. Fortunately, most inverters are designed to operate at about 12V in order to function with standard lead-acid batteries.
  50. 50. 41 Inverter is a small circuit which will convert the direct current (DC) to alternating current (AC). The power of a battery is converted in to ‘main voltages’ or AC power. This power can be used for electronic appliances like television, mobile phones, computer etc. the main function of the inverter is to convert DC to AC and step-up transformer is used to create main voltages from resulting AC. Fig 3.12 Block diagram of inverter In the block diagram battery supply is given to the MOSFET driver where it will convert DC to AC and the resulting AC is given to the step up transformer from the step up transformer we will the get the original voltage. 3.8.1 MOSFET POWER INVERTER This is the power inverter circuit based MOSFET RFP50N06. It is a simple circuit inverter that converts DC current into AC current, from 12V DC to 220V AC with output power of 100W. Inverter circuit is typically used for emergency lighting, since the power output is small, which is about 5W only. The following diagram is an inverter circuit which will give you 220V AC 50Hz with maximum power of 100W. The inverter capable to handle loads up to 100 W, it’s depended on your power inverter transformer.
  51. 51. Fig 3.13 This circuit will provide a very stable Output AC Voltage. Frequency of operation is determined by a pot and is normally set to 50 Hz. The RFP50N06 FETs are rated at 10 Amps and 12 is required for coo parallel connection to get more power. It is recommended to have a “Fuse” in the Power Line and to always have a “Load connected”, while power is being applied be approximately 10 Amps per 100 watts of output. The Power leads must be heavy enough wire When utilizing N across a load, the drain terminals of the high side MOSFETs are often connected to the highest voltage in the system. This creates a difficulty, as the gate terminal must be approximately 10V higher than the drain terminal for the MOSFET to conduct. Often, integrated circuit devices known as MOSFET drivers are utilized to achieve this difference through charge pumps or bootstrapping techniques. These chips are 42 Schematic diagram of MOSFET inverter This circuit will provide a very stable Output AC Voltage. Frequency of operation is determined by a pot and is normally set to 50 FETs are rated at 10 Amps and 12 Volts. Heat sink is required for cooling the MOSFETs. Add some MOSFETs with parallel connection to get more power. It is recommended to have a “Fuse” in the Power Line and to always have a “Load connected”, while power is being applied. The Fuse should be rated at 32 volts and should oximately 10 Amps per 100 watts of output. The Power leads must be heavy enough wire to handle this high current draw. When utilizing N Channel MOSFETs to switch a DC voltage across a load, the drain terminals of the high side MOSFETs are often connected to the highest voltage in the system. This creates a difficulty, as the gate terminal must be approximately 10V higher than the drain minal for the MOSFET to conduct. Often, integrated circuit devices known as MOSFET drivers are utilized to achieve this difference through charge pumps or bootstrapping techniques. These chips are Schematic diagram of MOSFET inverter This circuit will provide a very stable Output AC Voltage. Frequency of operation is determined by a pot and is normally set to 50 Volts. Heat sink d some MOSFETs with parallel connection to get more power. It is recommended to have a “Fuse” in the Power Line and to always have a “Load connected”, while The Fuse should be rated at 32 volts and should oximately 10 Amps per 100 watts of output. The Power leads Channel MOSFETs to switch a DC voltage across a load, the drain terminals of the high side MOSFETs are often connected to the highest voltage in the system. This creates a difficulty, as the gate terminal must be approximately 10V higher than the drain minal for the MOSFET to conduct. Often, integrated circuit devices known as MOSFET drivers are utilized to achieve this difference through charge pumps or bootstrapping techniques. These chips are
  52. 52. 43 capable of quickly charging the input capacitance of the MOSFET quickly before the potential difference is reached, causing the gate to source voltage to be the highest system voltage plus the capacitor voltage, allowing it to conduct. There are many MOSFET drivers available to power N Channel MOSFETs through level translation of low voltage control signals into voltages capable of supplying sufficient gate voltage. Advanced drivers contain circuitry for powering high and low side devices as well as N and P Channel MOSFETs. In this design, all MOSFETs are N Channel due to their increased current handling capabilities. To overcome the difficulties of driving high side N Channel MOSFETs, the driver devices use an external source to charge a bootstrapping capacitor connected between Vcc and source terminals. The bootstrap capacitor provides gate charge to the high side MOSFET. As the switch begins to conduct, the capacitor maintains a potential difference, rapidly causing the MOSFET to further conduct, until it is fully on. The name bootstrap component refers to this process and how the MOSFET acts as if it is “pulling itself up by its own boot strap”. Main components are: IC LT4013 is basically made up of two D-type flip flop modules and set/reset asynchronous toggle inputs. As the name suggests, the IC is primarily used as a bistable for toggling the output stage of a particular circuit, and it is fundamentally incorporated in most electronic circuits. IC 4001is the most commonly used Complementary Metal Oxide Semiconductor (CMOS) chip. It comes in a 14 pin Dual Inline Package (DIP). It has small notch on one side which is identified as pin 1.It consists of 4 independent NOR gate in a single chip. Each gate has 2
  53. 53. 44 inputs and 1 output. Working voltage range of IC is from 5V to 15V. It can deliver approx.10mA at 12V but this can be reduced as power supply voltage reduces. IC LM4001 along with IC4013 and the transistor form a voltage controlled oscillator of which the frequency is adjusted with the 25Kohmpot. The 13 volt Zener stabilize supply voltages and limit signals, while the 36 volt Zener limit spikes from the transformer. 3.8.2 WORKING OF MOSFET POWER INVERTER The AC input supplies a 220V AC, 50Hz from the public supply. This is connected to the charger circuit where it is rectified to DC voltage and through the relay switch to the output of the inverter to bypass the inverter when there is public electric power supply while the battery is charging. This inverter uses a 0 – 12 V/1Amp triggering transformer and a regulator to sense the AC mains supply. When the AC mains supply is available, this supply is given to the primary winding of the triggering transformer to give 12V AC supply at the secondary winding. It is then rectified by bridge rectifier and input to filter capacitors which convert the 18V supply to 12V DC supply. The 12V supply stays constant even when there is a change in the AC mains supply and the inverter is informed about the availability of the AC mains supply. The Oscillator, a pulse width modulator PMW IC SG 3524 to generate the 50Hz frequency required to generate AC supply by the inverter.
  54. 54. 45 The battery supply is connected to the IC SG 3524 through the inverter ON/OFF switch. The flip-flop converts the incoming signal into signals with changing polarity such that in a two-signal with changing polarity, the first is positive while the second is negative and vice versa. This process is repeated 50times per second to give an alternating signal with 50Hz frequency at the output of SG3524. This alternating signal is known as MOS Drive Signal . The MOS drive signals are given to the base of MOS driver transistor which results in the MOS drive signal getting separated into two different channels. The transistors amplify the 50Hz MOS drive signal at their base to a sufficient level and output them from the emitter. The 50Hz signal from the emitter of each of the transistor is connected to the gate G of all the MOSFETS in each of the MOSFET channel, through the appropriate resistance. The battery charger hen the inverter section receives AC mains supply, it stops operation but the charger section in the inverter starts its operation. In this mode, the inverter transformer works as a step down transformer and output 12V at its secondary winding. During the charging, MOSFET transistors at the output section works as rectifier with the drain working as the cathode while the source works as the anode. The center-tapping of the transformer receives positive supply and the MOSFET source 'S' receives negative supply from the battery. The center-tapping is connected to the positive terminal of the battery and the MOSFET source S is connected to the negative terminal with a shunt resistance. Thus, when the inverter receives AC mains supply, inverter transformer and MOSFET together work as a charger and charge the battery.
  55. 55. 46 The change over section is used to switch ON the inverter when the AC mains supply is OFF and to switch OFF the inverter when the AC mains supply returns (ON). During changeover, when the inverter receives AC mains supply, it stops drawing the battery supply and the AC mains supply at the inverter input is directly sent to the inverter output socket. This is done using a one, two-pole relay. The AC output gives a 220V AC, 50Hz either directly from the input when the AC mains supply is available or from the inverter circuit action on the battery when the AC mains supply is not available. Computers and other household appliances are connected to this output. The AC input to this device was fused with a 5A fuse to protect the transformer as well as the rectifying circuit in case of over voltage, and high current which could flow into the transformer. This AC is given to the step up transformer of the secondary coil from this coil only we will get the increased AC voltage , this AC voltage is so high; from step up transformer we will get the max voltage. Zener diode will help avoid the reverse current. The generated AC is not equal to the normal AC mains or house hold current. You cannot use this voltage for pure electric appliances like heater, electric cooker etc. Because of the fast switching of MOSFETs heat is dissipated which will effect the efficiency, use heat sink to remove this problem. The output voltage of the inverter was a square wave, filtered by a 2µF/400V capacitor connected across the output terminals to remove the unwanted harmonics and leaving smooth sine waveform output voltage.
  56. 56. 47 Thus a 12 V AC output voltage is transferred to the primary of transformer; it is stepped up to 230V. 3.9 STEP-UP TRANSFORMER The output of the inverter is 12V ac supply with a frequency of 50 Hz . This Ac supply is step up to 230 V by using step-up transformer. The Voltage Transformer can be thought of as an electrical component rather than an electronic component. Fig 3.14 Step-Up Transformer A transformer basically is very simple static (or stationary) electro-magnetic passive electrical device that works on the principle of Faraday’s law of induction by converting electrical energy from one value to another. On a step-up transformer there are more turns on the secondary coil than the primary coil. The transformer does this by linking together two or more electrical circuits using a common oscillating magnetic circuit which is produced by the transformer itself. A transformer operates on the principals of “electromagnetic induction”, in the form of Mutual Induction. Mutual induction is the process by which a coil of wire magnetically induces a voltage into another coil located in close proximity to it. Then we can say that transformers work in the “magnetic
  57. 57. 48 domain”, and transformers get their name from the fact that they “transform” one voltage or current level into another. Transformers are capable of either increasing or decreasing the voltage and current levels of their supply, without modifying its frequency, or the amount of electrical power being transferred from one winding to another via the magnetic circuit. A single phase voltage transformer basically consists of two electrical coils of wire, one called the “Primary Winding” and another called the “Secondary Winding”. We will define the “primary” side of the transformer as the side that usually takes power and the “secondary” as the side that usually delivers power. In a single-phase voltage transformer the primary is usually the side with the higher voltage. These two coils are not in electrical contact with each other but are instead wrapped together around a common closed magnetic iron circuit called the “core”. This soft iron core is not solid but made up of individual laminations connected together to help reduce the core’s losses. The two coil windings are electrically isolated from each other but are magnetically linked through the common core allowing electrical power to be transferred from one coil to the other. When an electric current passed through the primary winding, a magnetic field is developed which induces a voltage into the secondary winding .The output of the transformer is 230 V, 50 Hz ,single phase AC, which is fed to the load.
  58. 58. 3.10 ADDITIONAL SOURCE FOR THE BATTERY When the exercise machine is not in use, the main supply is used to charge the battery. bridge rectifier is used Fig 3.15: Single phase f The power supply consists of a Step down transformer (230V, 50Hz/12V) which steps down the voltage to 12V AC. This is converted to DC using a Bridge rectifier. The ripples are removed using a capacitive filter and it is then regulated to +12 V us setup. 3.10.1 DIODE RECTIFIER FOR POWER SUPPLY The purpose of a power supply is to take electrical energy in one form and convert it into another. There are many types of power supply. Most are designed to convert high voltage AC mains elect suitable low voltage supply for electronic circuits and other devices such as computers, fax machines and Singapore, supply from 230V, 50Hz AC mains is converted into smooth DC using AC-DC power supply. A power s into a series of blocks, each of which performs a particular function. A transformer first steps down high voltage AC to low voltage AC. A rectifier circuit is then used to convert AC to DC. This DC, 49 TIONAL SOURCE FOR THE BATTERY When the exercise machine is not in use, the main supply is used to charge the battery. For that step down transformer and single phase bridge rectifier is used. Single phase full-wave rectifier with filter The power supply consists of a Step down transformer (230V, 50Hz/12V) which steps down the voltage to 12V AC. This is converted to DC using a Bridge rectifier. The ripples are removed using a capacitive filter and it is then regulated to +12 V using a resistor diode DIODE RECTIFIER FOR POWER SUPPLY The purpose of a power supply is to take electrical energy in one form and convert it into another. There are many types of power supply. Most are designed to convert high voltage AC mains elect suitable low voltage supply for electronic circuits and other devices such as computers, fax machines and telecommunication equipment. In Singapore, supply from 230V, 50Hz AC mains is converted into smooth DC power supply. A power supply can by broken down into a series of blocks, each of which performs a particular function. A transformer first steps down high voltage AC to low voltage AC. A rectifier circuit is then used to convert AC to DC. This DC, When the exercise machine is not in use, the main supply is used For that step down transformer and single phase wave rectifier with filter capacitor The power supply consists of a Step down transformer (230V, 50Hz/12V) which steps down the voltage to 12V AC. This is converted to DC using a Bridge rectifier. The ripples are removed using a ing a resistor diode The purpose of a power supply is to take electrical energy in one form and convert it into another. There are many types of power supply. Most are designed to convert high voltage AC mains electricity to a suitable low voltage supply for electronic circuits and other devices such telecommunication equipment. In Singapore, supply from 230V, 50Hz AC mains is converted into smooth upply can by broken down into a series of blocks, each of which performs a particular function. A transformer first steps down high voltage AC to low voltage AC. A rectifier circuit is then used to convert AC to DC. This DC,
  59. 59. 50 however, contains ripples, which can be smoothened by a filter circuit. Power supplies can be ‘regulated’ or ‘unregulated’. A regulated power supply maintains a constant DC output voltage through ‘feedback action’. The output voltage of an unregulated supply, on the other hand, will not remain constant. It will vary depending on varying operating conditions, for example when the magnitude of input AC voltage changes. Main components of a regulated supply to convert 230V AC voltage to 12V DC are shown below. Fig 3.16 Block diagram of regulated power supply Power supplies are designed to produce as little ripple voltage as possible, as the ripple can cause several problems. For Example  In audio amplifiers, too much ripple shows up as an annoying 50 Hz or 100 Hz audible hum.  In video circuits, excessive ripple shows up as “hum” bars in the picture.  In digital circuits it can cause erroneous outputs from logic circuits.
  60. 60. 51 3.10.2 SINGLE PHASE FULL-WAVE RECTIFIER In many power supply circuits, the bridge rectifier is used. The bridge rectifier produces almost double the output voltage as a full wave center-tapped transformer rectifier using the same secondary voltage. The advantage of using this circuit is that no center-tapped transformer is required. During the positive half cycle (Fig 3.17), both D3 and D1 are forward biased. At the same time, both D2 and D4 are reverse biased. Note the direction of current flow through the load. During the negative half cycle (Fig 3.18) D2 and D4 are forward biased and D1 and D3 are reverse biased. Again note that current through the load is in the same direction although the secondary winding polarity has reversed. Fig 3.17 Operation during positive half cycle Fig 3.18 Operation during negative half cycle
  61. 61. 52 The load and ground connections are removed because we are concerned with the diode conditions only. In this circuit, diodes D1 and D3 are forward biased and act like closed switches. They can be replaced with wires. Diodes D2 and D4 are reverse biased and act like open switches. We can see that both diodes are reverse biased, in parallel, and directly across the secondary winding. The peak inverse voltage is therefore equal to Vm. The voltage obtained across the load resistor of the full-wave bridge rectifier described above has a large amount of ripple. A capacitor filter may be added to smoothen the ripple in the output, as shown below. Fig 3.19 Full wave Bridge rectifier with capacitor filter The rectifier circuits discussed above can be used to charge batteries and to convert AC voltages into constant DC voltages. Full- wave and bridge rectifier are more commonly used than half-wave rectifier.
  62. 62. 53 CHAPTER-4 IMPLEMENTATION AND RESULT 4.1 KEY REQUIREMENTS The safety test is the most crucial aspect of the test plan and each stage of the design must pass the safety test before moving on. The safety is important to three elements of the design. The project is designed for people who use this on a daily basis and safety evaluations need to ensure nothing will compromise the user’s safety. After all, something healthy such as exercising should not turn into something unhealthy. The second element of the safety test is for the servicing of the design. This means that the project should not discharge or bring harm to the person working on the design. This project is being developed to save the user energy and money.. The efficiency of each component needs to be as high as possible. The method of determining efficiency was different for each subsystem. For the generator, it requires high conversion efficiency from mechanical energy into electrical energy. The microprocessor needs to have the least amount of processing time as possible and this means streamlining the code as much as possible but maintaining the basic functional requirements. A high efficiency is required for each component to get the maximum result from the entire design which will translate into more energy and more money saved. The implementation capabilities apply mainly to the aesthetics and marketability of the design. The design needs to be compact enough to be used at home next to the elliptical but also durable enough to be used regularly at popular fitness centers.
  63. 63. 54
  64. 64. 55 4.2.1 DIAGRAM EXPLANATION The circuit consist of a bicycle powered 120VA alternator and then when the bicycle is pedaled, the spinning motion of the rear tire is used to produce mechanical energy directly into a alternator. DC supply is given to the alternator using a battery, thus the rotor produce flux. While exercising, the alternator starts to rotate and produce three phase AC supply. The output is connected to the rectifier. The three phase AC supply is convert into DC through a three phase diode bridge rectifier. Diode used is IN4007.The rectified DC supply is given to the voltage regulator. Voltage regulator regulates the voltage to 12V. Zener diode is used as voltage regulator. This 12V is used to charge battery and the same DC supply is fed to an inverter. The inverter is made is made with MOSFET and driver circuit. The output of the inverter is 12V AC supply with a frequency of 50 Hz. This AC supply is step up to 230 V by using step up transformer. Secondary of the transformer is directly connected to the load. When the exercise machine is not used, the main supply is used to charge the battery. For that charging step down transformer and bridge rectifier is used. The output of the transformer is 12V AC. This 12 V AC is converted to DC by using diode bridge rectifier. Filter circuit also provided for eliminating ripples. The output from the diode rectifier is directly connected to the battery. So the battery also charges while the exercise machine is not in use. In our project, we are using a 40 W incandescent lamp as load.
  65. 65. 56 4.3 ELEMENT SPECIFICATIONS Our design will provide all of the following:  Bicycle: A stationary bicycle with belt and pulley arrangement  Alternator: 120VA, 12V, 10A, 300 rpm alternator  Rectifier: Three phase bridge rectifier. Diode used IN4007  Battery: 10Ah 12VDC deep cycle lead acid battery for compatibility, convenience, and cost.  Single phase 230V AC supply, step down transformer and rectifier provide additional source for the battery.  Step down transformer : 230V to 12V AC single phase transformer  Rectifier: Single phase full wave rectifier. Diode use In4007  Inverter: 100W MOSFET inverter with 12V AC output.  Step-up transformer: 12V to 230V AC single phase transformer  Load : 40W 230V incandescent bulb is connected as load. 4.4 PROJECT ANALYSIS The time the light takes to turn on is dependent on both speed of the bicycle and the voltage the regulator is adjusted. The initial generated light has a blinking behavior, which stabilizes to an unwavering beam as more power is generated and available to the regulator and light.
  66. 66. 57 Fig 4.2 Voltage Vs Speed The fig 4.2 shows the relation between speed and the voltage The voltage coming out of the alternator depends on two variables: the amount of current flowing through the field coil (i.e. the strength of the magnetic field) and the speed at which the alternator’s field is rotating. The alternator has a regulator that tries to keep the voltage across the battery at a steady 12.8V (the optimal voltage to recharge 12V batteries). It does this by regulating the amount of current flowing to the field coil. Once the alternator is self-sustaining, the only current flowing to the field originates from the alternator itself. If the output voltage is too high, the regulator lowers the current flowing to the field coil. If the output voltage is too low, the regulator increases the current flowing to the field coil. Simply put, as long as the alternator can maintain at least 12.8 V across the battery, making the pulley spin faster or slower will have absolutely no effect on the power output. The output voltage of the alternator with the RPM proves to be completely unchanging as expected, due to the regulation of the alternator’s controller. The zener diode was connected to the alternator which regulated the output voltage to 12.8 V, shown in Fig 4.2 0 2 4 6 8 10 12 14 50 100 150 200 250 300 Voltage(V) Speed (rpm) VOLTAGE Vs SPEED
  67. 67. 58 Fig 4.3 Current Vs Speed The current of the alternator with the speed of the cycle (similar to alternator speed) is shown in the Fig 4.3 .The output current is minimum until around 300 rpm. Once that rpm rate is surpassed, the output current increase according to the load connected 4.5 RESULT We construct innovative exercise equipment for generating electricity. By using bicycle, alternator, inverter, battery, step up and step down transformer, rectifier circuit and incandescent lamp. We successfully take the 230 V single phase 50 Hz output supply and it is used to light 40W incandescent lamp. When the exercise machine is not used, the main supply is used to charge the battery. So the battery also charges while the exercise machine is not in use. So provide a continuous supply. 0 2 4 6 8 10 12 50 100 150 200 250 300 Current(A) Speed (rpm) CURRENT Vs SPEED
  68. 68. 59 CHAPTER 5 CONCLUSION We design and implement an innovative exercise equipment (stationary bicycle) to generate electrical power for the house appliances. Energy storage is deemed necessary and important within renewable energy systems to ensure stability of the system. Coupling pedal driven generation and storage will drastically increase reliability of the smart system. These models vary in complexity and accuracy and therefore the model chosen must match the application for which it is needed. It will be very helpful for the rural areas. In this day where the world is challenged to be more responsible in its sourcing of electrical power, the method of human power generation could be a solution that also helps mitigate the issue of obesity and overweight. If additional design and study of this concept proves it effective in energy use reduction, localized energy delivery and sustainability education, it could efficiently answer the three great challenges; source of electrical power, reducing the emission of CO2 to the atmosphere and the issue of obesity
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