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BIOMECHANICAL ENERGY HARVESTER USING E-WASTE

ABSTRACT

This project is about a biomechanical energy harvester that is used to collect power while

walking and use it for powering Night Lamps.The main reason of going for biomechanical energy harvesting i.e., energy

production from physical movements is as an alternative to conventional energy sources.

Arm swing, shoe power, back pack power are most widely used bio mechanical

harvesters other than knee brace.

The main principle of operation of leg brace generative braking", analogous to the

braking systems found in hybrid-electric cars. Hybrid electric cars take advantage of

stop-and-go driving using so-called "regenerative braking" where the energy normally

dissipated as heat is used to drive a generator.

Within each stride muscles are continuously accelerating and decelerating the

body. Leg brace works on the same principle as these cars. Using a series of gears, the

knee brace assists the hamstring in slowing the body just before the foot hits the ground,

whilst simultaneously generating electricity. Sensors on the device switch the generator

off for the remainder of each step. In this way, the device puts less strain on the wearer

than if it was constantly producing energy.

Night lamp usingLed 1 watt

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Leg Brace Jig of the 2kg device produced an average of 1

to3 watts of electricity from a slow walk. Wearing a device

on each leg, an individual can generate up to 3 watts of

electricity with little additional physical effort. Walking

quickly, however, generates as much as 5 watts. Producing

substantial electricity with little extra effort makes this

method well-suited for many applications which include

lighting of night lamps, mobile charging and powering

radio sets.

The cost of harvesting the additional metabolic

power required to produce 1 watt of electricity is less than

one-eighth of that for conventional human power

generation

The so called zero watt bulbs which are used as night lamps require about 12

watts of energy. This energy if produced at home can save around 30 units every month

which if not much can save some amount of the conventional energy consumption.

Hence this project aims

Building a device called knee brace

Saving of dissipated energy using the knee brace

Using the energy stored for powering of night lamps

INTRODUCTION

ENERGY CRISIS

An energy crisis is any great bottleneck (or price rise) in the supply of energy resources

to an economy. In popular literature though, it often refers to one of the energy sources

used at a certain time and place.

What Constitutes an Energy Crisis?

Energy crisis is a situation in which the nation suffers from a disruption of energy

supplies (in our case, oil) accompanied by rapidly increasing energy prices that threaten

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economic and national security. The threat to economic security is represented by the

possibility of declining economic growth, increasing inflation, rising unemployment, and

losing billions of dollars in investment. The threat to national security is represented by

the inability of the US government to exercise various foreign policy options, especially

in regard to countries with substantial oil reserves. For example, the recent disruption of

Venezuelan oil supplies may limit the US policy options toward Iraq.

Causes

Market failure is possible when monopoly manipulation of markets occurs. A crisis can

develop due to industrial actions like union organized strikes and government embargoes.

The cause may be over-consumption, aging infrastructure, choke point disruption or

bottlenecks at oil refineries and port facilities that restrict fuel supply. An emergency may

emerge during unusually cold winters due to increased consumption of energy. Pipeline

failures and other accidents may cause minor interruptions to energy supplies. A crisis

could possibly emerge after infrastructure damage from severe weather. Attacks by

terrorists or militia on important infrastructure are a possible problem for energy

consumers, with a successful strike on a Middle East facility potentially causing global

shortages. Political events, for example, when governments change due to regime change,

monarchy collapse, military occupation, and coup may disrupt oil and gas production and

create shortages.

Historical crises

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1970s Energy Crisis - Cause: peaking of oil production in major industrial nations

(Germany, U.S., Canada, etc.) and embargoes from other producers

1973 oil crisis - Cause: an OPEC oil export embargo by many of the major Arab oil-

producing states, in response to western support of Israel during the Yom Kippur War

1979 oil crisis - Cause: the Iranian revolution

1990 spike in the price of oil - Cause: the Gulf War

The 2000±2001 California electricity crisis - Cause: failed deregulation, and business

corruption.

The UK fuel protest of 2000 - Cause: Raise in the price of crude oil combined with

already relatively high taxation on road fuel in the UK.

North American natural gas crisis

Argentine energy crisis of 2004

North Korea has had energy shortages for many years.

Zimbabwe has experienced a shortage of energy supplies for many years due to financial

mismanagement.

Social and economic effects

The macroeconomic implications of a supply shock-induced energy crisis are large,

because energy is the resource used to exploit all other resources. When energy markets

fail, an energy shortage develops. Electricity consumers may experience intentionallyengineered rolling blackouts which are released during periods of insufficient supply or

unexpected power outages, regardless of the cause. Industrialized nations are dependent

on oil, and efforts to restrict the supply of oil would have an adverse effect on the

economies of oil producers. For the consumer, the price of natural gas, gasoline (petrol)

and diesel for cars and other vehicles rises. An early response from stakeholders is the

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call for reports, investigations and commissions into the price of fuels. There are also

movements towards the development of more sustainable urban infrastructure.

Crisis management

An electricity shortage is felt most by those who depend on electricity for their heating,

cooking and water supply. In these circumstances a sustained energy crisis may become a

crisis. If an energy shortage is prolonged a crisis management phase is enforced by

authorities. Energy audits may be conducted to monitor usage. Various curfews with the

intention of increasing energy conservation may be initiated to reduce consumption. To

conserve power during the Central Asia energy crisis, authorities in Tajikistan ordered bars and cafes to operate by candlelight.[10] Warnings issued that peak demand power

supply might not be sustained. In the worst kind of energy crisis energy rationing and fuel

rationing may be incurred. Panic buying may beset outlets as awareness of shortages

spread. Facilities close down to save on heating oil; and factories cut production and lay

off workers. The risk of stagflation increases.

Mitigation of an energy crisis

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Nuclear power in Germany

The Hirsch report made clear that an energy crisis is best averted by preparation. In 2008,

solutions such as the Pickens Plan and the satirical in origin Paris Hilton energy plan

suggest the growing public consciousness of the importance of mitigation. Energy may

be reformed leading to greater energy intensity, for example in Iran with the 2007 Gas

Rationing Plan in Iran, Canada and the National Energy Program and in the USA with the

Energy Independence and Security Act of 2007. In Europe the oil phase-out in Sweden is

an initiative a government has taken to provide energy security. Another mitigation

measure is the setup of a cache of secure fuel reserves like the United States Strategic

Petroleum Reserve, in case of national emergency. Chinese energy policy includes

specific targets within their 5 year plans.

World energy usage

Future and alternative energy sources

In response to the petroleum crisis, the principles of green energy and sustainable living

movements gain popularity. This has led to increasing interest in alternate power/fuel

research such as fuel cell technology, liquid nitrogen economy, hydrogen fuel, methanol,

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biodiesel, Karrick process, solar energy, geothermal energy, tidal energy, wave power,

and wind energy, and fusion power. To date, only hydroelectricity and nuclear power

have been significant alternatives to fossil fuel. Hydrogen gas is currently produced at a

net energy loss from natural gas, which is also experiencing declining production in

North America and elsewhere. When not produced from natural gas, hydrogen still needs

another source of energy to create it, also at a loss during the process. This has led to

hydrogen being regarded as a 'carrier' of energy, like electricity, rather than a 'source'.

The unproven dehydrogenating process has also been suggested for the use water as an

energy source. Efficiency mechanisms such as Megawatt power can encourage

significantly more effective use of current generating capacity. It is a term used to

describe the trading of increased efficiency, using consumption efficiency to increase

available market supply rather than by increasing plant generation capacity. As such, it is

a demand-side as opposed to a supply-side measure.

Coal as an alternative to wood

Historian Norman F. Cantor describes how in the late medieval period, coal was the new

alternative fuel to save the society from overuse of the dominant fuel, wood:"Europeans

had lived in the midst of vast forests throughout the earlier medieval centuries. After

1250 they became so skilled at deforestation that by 1500 AD they were running short of

wood for heating and cooking... By 1500 Europe was on the edge of a fuel and nutritional

disaster, [from] which it was saved in the sixteenth century only by the burning of soft

coal and the cultivation of potatoes and maize." Whale oil was the dominant form of

lubrication and fuel for lamps in the early 19th century, but by mid century and the

depletion of the whale stocks, whale oil prices were skyrocketing and could not compete

with the newly discovered source of cheap petroleum from Pennsylvania in 1859.

Alcohol as an alternative to fossil fuels

In 1917, Alexander Graham Bell advocated ethanol from corn and other foodstuffs as an

alternative to coal and oil, stating that the world was in measurable distance of depleting

these fuels. For Bell, the problem requiring an alternative was lack of renewability of

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orthodox energy sources. Since the 1970s, Brazil has had an ethanol fuel program which

has allowed the country to become the world's second largest producer of ethanol (after

the United States) and the world's largest exporter. Brazil¶s ethanol fuel program uses

modern equipment and cheap sugar cane as feedstock, and the residual cane-waste

(biogases) is used to process heat and power. There are no longer light vehicles in Brazil

running on pure gasoline. By the end of 2008 there were 35,000 filling stations

throughout Brazil with at least one ethanol pump. Cellulosic ethanol can be produced

from a diverse array of feedstocks, and involves the use of the whole crop. This new

approach should increase yields and reduce the carbon footprint because the amount of

energy-intensive fertilizers and fungicides will remain the same, for a higher output of

usable material. As of 2008, there are nine commercial cellulosic ethanol plants which

are either operating, or under construction, in the United States.

Coal gasification as an alternative to petroleum

In the 1970s, President Jimmy Carter's administration advocated coal gasification as an

alternative to expensive imported oil. The program, including the Synthetic Fuels

Corporation was scrapped when petroleum prices plummeted in the 1980s.

Renewable energy vs. non-renewable energy

Renewable energy is energy generated from natural resources²such as sunlight, wind,

rain, tides and geothermal heat²which are renewable (naturally replenished). When

comparing the processes for producing energy, there remain several fundamental

differences between renewable energy and fossil fuels. The process of producing oil,

coal, or natural gas fuel is a difficult and demanding process that requires a great deal of

complex equipment, physical and chemical processes. On the other hand, alternative

energy can be widely produced with basic equipment and naturally basic processes.

Wood, the most renewable and available alternative energy, burns the same amount of

carbon it would emit if it degraded naturally.

Ecologically friendly alternatives

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Renewable energy sources such as biomass are sometimes regarded as an alternative to

ecologically harmful fossil fuels. Renewable are not inherently alternative energies for

this purpose. For example, the Netherlands, once leader in use of palm oil as a biofuel,

has suspended all subsidies for palm oil due to the scientific evidence that their use "may

sometimes create more environmental harm than fossil fuels´. The Netherlands

government and environmental groups are trying to trace the origins of imported palm

oil, to certify which operations produce the oil in a responsible manner. Regarding

biofuels from foodstuffs, the realization that converting the entire grain harvest of the US

would only produce 16% of its auto fuel needs, and the decimation of Brazil's CO2

absorbing tropical rain forests to make way for biofuel production has made it clear that

placing energy markets in competition with food markets results in higher food prices

and insignificant or negative impact on energy issues such as global warming or

dependence on foreign energy. Recently, alternatives to such undesirable sustainable

fuels are being sought, such as commercially viable sources of cellulosic ethanol.

Relatively new concepts for alternative energy

Algae fuel

Algae fuel is a biofuel which is derived from algae. During photosynthesis, algae andother photosynthetic organisms capture carbon dioxide and sunlight and convert it into

oxygen and biomass.

Biomass briquettes

Biomass briquettes are being developed in the developing world as an alternative to

charcoal. The technique involves the conversion of almost any plant matter into

compressed briquettes that typically have about 70% the calorific value of charcoal.

There are relatively few examples of large scale briquette production. One exception is in

North Kivu, in eastern Democratic Republic of Congo, where forest clearance for

charcoal production is considered to be the biggest threat to Mountain Gorilla habitat.

The staff of Virunga National Park have successfully trained and equipped over 3500

people to produce biomass briquettes, thereby replacing charcoal produced illegally

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inside the national park, and creating significant employment for people living in extreme

poverty in conflict affected areas.

Biogas digestion

Biogas digestion deals with harnessing the methane gas that is released when waste

breaks down. This gas can be retrieved from garbage or sewage systems. Biogas digesters

are used to process methane gas by having bacteria break down biomass in an anaerobic

environment. The methane gas that is collected and refined can be used as an energy

source for various products.

Biological Hydrogen Production

Hydrogen gas is a completely clean burning fuel; its only by-product is water. It also

contains relatively high amount of energy compared with other fuels due to its chemical

structure.

2H2 + O2 ² 2H2O + High Energy

High Energy + 2H2O ² 2H2 + O2

This requires a high-energy input, making commercial hydrogen very inefficient. Use of

a biological vector as a means to split water, and therefore produce hydrogen gas, would

allow for the only energy input to be solar radiation. Biological vectors can include

bacteria or more commonly algae. This process is known as biological hydrogen

production. It requires the use of single celled organisms to create hydrogen gas through

fermentation. Without the presence of oxygen, also known as an anaerobic environment,

regular cellular respiration cannot take place and a process known as fermentation takes

over. A major by-product of this process is hydrogen gas. If we could implement this on a

large scale, then we could take sunlight, nutrients and water and create hydrogen gas to

be used as a dense source of energy. Large-scale production has proven difficult. It was

not until 1999 that we were able to even induce these anaerobic conditions by sulfur

deprivation. Since the fermentation process is an evolutionary back up, turned on during

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stress, the cells would die after a few days. In 2000, a two-stage process was developed to

take the cells in and out of anaerobic conditions and therefore keep them alive. For the

last ten years, finding a way to do this on a large-scale has been the main goal of

research. Careful work is being done to ensure an efficient process before large-scale

production, however once a mechanism is developed, this type of production could solve

our energy needs.

Floating wind farms

Floating wind farms are similar to a regular wind farm, but the difference is that they

float in the middle of the ocean. Offshore wind farms can be placed in water up to 40

meters (131 feet) deep, whereas floating wind turbines can float in water up to 700 meters

(2,297 feet) deep. The advantage of having a floating wind farm is to be able to harness

the winds from the open ocean. Without any obstructions such as hills, trees and

buildings, winds from the open ocean can reach up to speeds twice as fast as coastal

areas. A Norwegian energy company, Statoil Hydro, will launch the first test period for

the floating wind farms in autumn 2009.

Investing in alternative energy

Over the last three years publicly traded alternative energy have been very volatile, with

some 2007 returns in excess of 100%, some 2008 returns down 90% or more, and peak-

to-trough returns in 2009 again over 100%.[citation needed ] In general there are three sub

segments of ³alternative´ energy investment: solar energy, wind energy and hybrid

electric vehicles. Alternative energy sources which are renewable, free and have lower

carbon emissions than what we have now are wind energy, solar energy, geothermal

energy, and bio fuels. Each of these four segments involves very different technologies

and investment concerns. For example, photovoltaic solar energy is based on

semiconductor processing and accordingly, benefits from steep cost reductions similar to

those realized in the microprocessor industry (i.e., driven by larger scale, higher module

efficiency, and improving processing technologies). PV solar energy is perhaps the only

energy technology whose electricity generation cost could be reduced by half or more

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over the next 5 years. Better and more efficient manufacturing process and new

technology such as advanced thin film solar cell is a good example of that helps to reduce

industry cost. The economics of solar PV electricity are highly dependent on silicon

pricing and even companies whose technologies are based on other materials (e.g., First

Solar) are impacted by the balance of supply and demand in the silicon market.[citation

needed ] In addition, because some companies sell completed solar cells on the open market

(e.g., Q-Cells), this creates a low barrier to entry for companies that want to manufacture

solar modules, which in turn can create an irrational pricing environment. In contrast,

because wind power has been harnessed for over 100 years, its underlying technology is

relatively stable. Its economics are largely determined by sitting (e.g., how hard the wind

blows and the grid investment requirements) and the prices of steel (the largest

component of a wind turbine) and select composites (used for the blades). Because

current wind turbines are often in excess of 100 meters high, logistics and a global

manufacturing platform are major sources of competitive advantage. These issues and

others were explored in a research report by Sanford Bernstein. Some of its key

conclusions are shown here

Alternative energy in transportation

Due to steadily rising gas prices in 2008 with the US national average price per gallon of

regular unleaded gas rising above $4.00 at one point, there has been a steady movement

towards developing higher fuel efficiency and more alternative fuel vehicles for

consumers. In response, many smaller companies have rapidly increased research and

development into radically different ways of powering consumer vehicles. Hybrid and

battery electric vehicles are commercially available and are gaining wider industry and

consumer acceptance worldwide.

Making Alternative Energy Mainstream

Before alternative energy becomes main-stream there are a few crucial obstacles that it

must overcome: First there must be increased understanding of how alternative energies

work and why they are beneficial; secondly the availability components for these systems

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must increase and lastly the pay-off time must be decreased. For example, emergency of

Electric vehicle (EV) and Plug-in Hybrid Electric Vehicle (PHEV) are on the raise. These

vehicles depend heavily on an effective charging infrastructure such as a smart grid

infrastructure to be able to implement electricity as mainstream alternative energy for

future transportations.

ADVANTAGES AND DISADVANTAGES OF ENERGY SOURCES

NATURAL GAS

Advantages

y Burns clean compared to cola, oil (less polluting)

y 70% less carbon dioxide compared to other fossil fuels

y helps improve quality of air and water (not a pollutant)

y does not produce ashes after energy release

y has high heating value of 24,000 Btu per pound

y inexpensive compared to coal

y no odor until added

Drawbacks

y not a renewable source

y finite resource trapped in the earth (some experts disagree)

y Inability to recover all in-place gas from a producible deposit because of

unfavorable economics and lack of technology (It costs more to recover the

remaining natural gas because of flow, access, etc.)

Other information

y 5,149.6 trillion cubic feet of natural gas reserve left (more than oil but less than

coal)

y 23.2% of total consumption of natural gas is in the United States

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WATER POWER

Pros

y

Provides water for 30-30% of the world¶s irrigated landy Provides 19% of electricity

y Expands irrigation

y Provides drinking water

y Supplies hydroelectric energy (falling water used to run turbines)

y Easier for third world countries to generate power (if water source is available)

y It is cheaper

Cons

y Destabilizes marine ecosystems

y Water wars (up river and down river; e.g., the water war between Georgia,

Alabama, and Florida is ongoing)

y Dam building is very costly

y People have to relocate

y Some dams have to be torn down (Some older ones are not stable.)

y Restricted to areas with flowing water

y Pollution affects water power

y Flooding of available land that could be used for agriculture

CRUDE OIL

Advantages

y Oil is one of the most abundant energy resources

y Liquid form of oil makes it easy to transport and use

y Oil has high heating value

y Relatively inexpensive

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y No new technology needed to use

Disadvantages

y

Oil burning leads to carbon emissionsy Finite resources (some disagree)

y Oil recovery processes not efficient enough²technology needs to be developed to

provide better yields

y Oil drilling endangers the environment and ecosystems

y Oil transportation (by ship) can lead to spills, causing environmental and

ecological damage (major oil spill near Spain in late Fall 2002)

Issues

y The world consumes more than 65 billion barrels of petroleum each day. By 2015

the consumption will increase to 99 billion barrels per day.

y Fossil fuels such as oil take billions of years to form.

y In 1996, the Energy Information Administration estimates of crude oil reserves

were 22 billion barrels. In 1972, the estimate was 36.3 billion barrels.

y Cost of oil has dropped since 1977. It was $15 per barrel then. It was $5 at the

time the authors wrote the book.

NUCLEAR POWER

Pros

y Clear power with no atmospheric emissions

y Useful source of energy

y Fuel can be recycled

y Low cost power for today¶s consumption

y Viable form of energy in countries that do not have access to other forms of fuel

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Cons

y Potential of high risk disaster (Chernobyl)

y Waste produced with nowhere to put it

y Waste produced from nuclear weapons not in use

y Earthquakes can cause damage and leaks at plants

y Contamination of the environment (long term)

y Useful lifetime of a nuclear power plant

y Plant construction is highly politicized

WIND POWER

Advantages

y Continuous sources of energy

y Clean source of energy

y No emissions into the atmosphere

y Does not add to thermal burden of the earth

y Produces no health-damaging air pollution or acid rain

y Land can be sued to produce energy and grow crops simultaneously

y Economical

y Benefits local communities (jobs, revenue)

Disadvantages

y For most locations, wind power density is low

y Wind velocity must be greater than 7 mph to be usable in most areas

y Problem exists in variation of power density and duration (not reliable)

y Need better ways to store energy

y Land consumption

COAL

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Pros

y One of the most abundant energy sources

y Versatile; can be burned directly, transformed into liquid, gas, or feedstock

y Inexpensive compared to other energy sources

y Good for recreational use (charcoal for barbequing, drawing)

y Can be used to produce ultra-clean fuel

y Can lower overall amount of greenhouse gases (liquification or gasification)

y Leading source of electricity today

y Reduces dependence on foreign oil

y By-product of burning (ash) can be used for concrete and roadways

Cons

y Source of pollution: emits waste, SO2 , Nitrogen Oxide, ash

y Coal mining mars the landscape

y Liquification, gasification require large amounts of water

y Physical transport is difficult

y Technology to process to liquid or gas is not fully developed

y Solid is more difficult to burn than liquid or gases

y Not renewable in this millennium

y High water content reduces heating value

y Dirty industry²leads to health problems

y Dirty coal creates more pollution and emissions

OBJECTIVE

Electronic waste

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Defective and obsolete electronic equipment.

Electronic waste, e-waste, e-scrap, or Waste Electrical and Electronic Equipment

(WEEE) describes loosely discarded, surplus, obsolete, or broken electrical or electronic

devices. Environmental groups claim that the informal processing of electronic waste in

developing countries causes serious health and pollution problems. Some electronic scrap

components, such as CRTs, contain contaminants such as lead, cadmium, beryllium,

mercury, and brominate flame retardants. Activists claim that even in developed

countries recycling and disposal of e-waste may involve significant risk to workers and

communities and great care must be taken to avoid unsafe exposure in recycling

operations and leaching of material such as heavy metals from landfills and incinerator

ashes. Scrap industry and USA EPA officials agree that materials should be managed

with caution, but that environmental dangers of unused electronics have been exaggerated

by groups which benefit from increased regulation.

Problems

Rapid change in technology, low initial cost, and planned obsolescence have resulted in a

fast-growing surplus of electronic waste around the globe. Dave Kruch, CEO of Cash for

Laptops, regards electronic waste as a "rapidly expanding" issue. Technical solutions are

available, but in most cases a legal framework, a collection system, logistics, and other

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services need to be implemented before a technical solution can be applied. An estimated

50 million tons of E-waste is produced each year. The USA discards 30 million

computers each year and 100 million phones are disposed of in Europe each year. The

Environmental Protection Agency estimates that only 15-20% of e-waste is recycled, the

rest of these electronics go directly into landfills and incinerators.[citation needed ]In the

United States, an estimated 70% of heavy metals in landfills comes from discarded

electronics, while electronic waste represents only 2% of America's trash in landfills. The

Environmental Protection Agency (EPA) states that unwanted electronics totaled 2

million tons in 2005, and 3 million tons in 2006. They also estimate that e-waste is

growing at two to three times the rate of any other waste source. Discarded electronics

represented 5 to 6 times as much weight as recycled electronics. The Consumer

Electronics Association says that U.S. households spend an average of $1,400 annually

on an average of 24 electronic items, leading to speculations of millions of tons of

valuable metals sitting in desk drawers. The U.S. National Safety Council estimates that

75% of all personal computers ever sold are now gathering dust as surplus electronics.

While some recycle, 7% of cell phone owners still throw away their old cell phones.

Surplus electronics have extremely high cost differentials. A single repairable laptop can

be worth hundreds of dollars, while an imploded cathode ray tube (CRT) is extremely

difficult and expensive to recycle. This has created a difficult free-market economy.

Large quantities of used electronics are typically sold to countries with very high repair

capability and high raw material demand, which can result in high accumulations of

residue in poor areas without strong environmental laws. Trade in electronic waste is

controlled by the Basel Convention. The Basel Convention Parties have considered the

question of whether exports of hazardous used electronic equipment for repair or

refurbishment are not considered as Basel Convention hazardous wastes unless they are

discarded. The burden of proof that the items will be repaired and not discarded rest on

the exporter, and any ultimate disposal of non-working components is subject to controls

under that Convention. In the Guidance document produced on that subject, that question

was left up to the Parties. Like virgin material mining and extraction, recycling of

materials from electronic scrap has raised concerns over toxicity and carcinogenicity of

some of its substances and processes. Toxic substances in electronic waste may include

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trammel screens are employed to separate glass, plastic, and ferrous and nonferrous

metals, which can then be further separated at a smelter. Leaded glass from CRTs is

reused in car batteries, ammunition, and lead wheel weights, or sold to foundries as a

fluxing agent in processing raw lead ore. Copper, gold, palladium, silver, and tin are

valuable metals sold to smelters for recycling. Hazardous smoke and gases are captured,

contained, and treated to mitigate environmental threat. These methods allow for safe

reclamation of all valuable computer construction materials. Hewlett-Packard product

recycling solutions manager Renee St. Denis describes its process as: "We move them

through giant shredders about 30 feet tall and it shreds everything into pieces about the

size of a quarter. Once your disk drive is shredded into pieces about this big, it's hard to

get the data off."

An ideal electronic waste recycling plant combines dismantling for component recovery

with increased cost-effective processing of bulk electronic waste. Reuse is an option to

recycling because it extends the lifespan of a device. Devices still need eventual

recycling, but by allowing others to purchase used electronics, recycling can be

postponed and value gained from device use.

Electronic waste substances

Some computer components can be reused in assembling new computer products, while

others are reduced to metals that can be reused in applications as varied as construction,

flatware, and jewelry. Substances found in large quantities include epoxy resins,

fiberglass, PCBs, PVC (polyvinyl chlorides), thermosetting plastics, lead, tin, copper,

silicon, beryllium, carbon, iron and aluminium.Elements found in small amounts include

cadmium, mercury, and thallium. Elements found in trace amounts include americium,

antimony, arsenic, barium, bismuth, boron, cobalt, europium, gallium, germanium, gold,

indium, lithium, manganese, nickel, niobium, palladium, platinum, rhodium, ruthenium,

selenium, silver, tantalum, terbium, thorium, titanium, vanadium, and yttrium. Almost all

electronics contain lead and tin (as solder) and copper (as wire and printed circuit board

tracks), though the use of lead-free solder is now spreading rapidly.

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TECHNOLOGIES USED

Light-emitting diode

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as

indicator lamps in many devices, and are increasingly used for lighting. Introduced as a

practical electronic component in 1962, early LEDs emitted low-intensity red light, but

modern versions are available across the visible, ultraviolet and infrared wavelengths,

with very high brightness. The LED is based on the semiconductor diode. When a diode

is forward biased (switched on), electrons are able to recombine with holes within the

device, releasing energy in the form of photons. This effect is called electroluminescence

and the color of the light (corresponding to the energy of the photon) is determined by the

energy gap of the semiconductor. An LED is usually small in area (less than 1 mm2), and

integrated optical components are used to shape its radiation pattern and assist in

reflection.LEDs present many advantages over incandescent light sources including

lower energy consumption, longer lifetime, improved robustness, smaller size, faster

switching, and greater durability and reliability. However, they are relatively expensive

and require more precise current and heat management than traditional light sources.

Current LED products for general lighting are more expensive to buy than fluorescent

lamp sources of comparable output. They also enjoy use in applications as diverse as

replacements for traditional light sources in aviation lighting, automotive lighting

(particularly indicators) and in traffic signals. The compact size of LEDs has allowed new

text and video displays and sensors to be developed, while their high switching rates are

useful in advanced communications technology. Infrared LEDs are also used in the

remote control units of many commercial products including televisions, DVD players,

and other domestic appliances.

Technology

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I-V diagram for a diode an LED will begin to emit light when the on-voltage is exceeded.

Typical on voltages are 2-3 Volt

Efficiency and operational parameters

Typical indicator LEDs are designed to operate with no more than 30±60 milliwatts

[mW] of electrical power. Around 1999, Philips Lumileds introduced power LEDs

capable of continuous use at one watt .These LEDs used much larger semiconductor die

sizes to handle the large power inputs. Also, the semiconductor dies were mounted onto

metal slugs to allow for heat removal from the LED die. One of the key advantages of

LED-based lighting is its high efficiency, as measured by its light output per unit power

input. White LEDs quickly matched and overtook the efficiency of standard incandescent

lighting systems. In 2002, Lumileds made five-watt LEDs available with a luminous

efficacy of 18±22 lumens per watt [lm/W]. For comparison, a conventional 60±100 W

incandescent light bulb produces around 15 lm/W, and standard fluorescent lights

produce up to 100 lm/W. A recurring problem is that efficiency will fall dramatically for

increased current. This effect is known as droop and effectively limits the light output of

a given LED; increasing heating more than light output for increased current. In

September 2003, a new type of blue LED was demonstrated by the company Cree, Inc. to

provide 24 mW at 20 milliamperes [mA]. This produced a commercially packaged white

light giving 65 lm/W at 20 mA, becoming the brightest white LED commercially

available at the time, and more than four times as efficient as standard incandescent. In

2006 they demonstrated a prototype with a record white LED luminous efficacy of 131

lm/W at 20 mA. Also, Seoul Semiconductor has plans for 135 lm/W by 2007 and 145

lm/W by 2008, which would be approaching an order of magnitude improvement over

standard incandescent and better even than standard fluorescents. Nichia Corporation has

developed a white LED with luminous efficacy of 150 lm/W at a forward current of 20

mA. High-power (� 1 W) LEDs are necessary for practical general lighting applications.

Typical operating currents for these devices begin at 350 mA.Note that these efficiencies

are for the LED chip only, held at low temperature in a lab. In a lighting application,

operating at higher temperature and with drive circuit losses, efficiencies are much lower.

United States Department of Energy (DOE) testing of commercial LED lamps designed

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to replace incandescent lamps or CFLs showed that average efficacy was still about 46

lm/W in 2009 (tested performance ranged from 17 lm/W to 79 lm/W). Cree issued a press

release on February 3, 2010 about a laboratory prototype LED achieving 208 lumens per

watt at room temperature. The correlated color temperature was reported to be 4579 K.

Lifetime and failure

Solid state devices such as LEDs are subject to very limited wear and tear if operated at

low currents and at low temperatures. Many of the LEDs produced in the 1970s and

1980s are still in service today. Typical lifetimes quoted are 25,000 to 100,000 hours but

heat and current settings can extend or shorten this time significantly. The most common

symptom of LED (and diode laser) failure is the gradual lowering of light output and loss

of efficiency. Sudden failures, although rare, can occur as well. Early red LEDs were

notable for their short lifetime. With the development of high-power LEDs the devices

are subjected to higher junction temperatures and higher current densities than traditional

devices. This causes stress on the material and may cause early light output degradation.

To quantitatively classify lifetime in a standardized manner it has been suggested to use

the terms L75 and L50 which is the time it will take a given LED to reach 75% and 50%

light output respectively. Like other lighting devices, LED performance is temperature

dependent. Most manufacturers¶ published ratings of LEDs are for an operating

temperature of 25°C. LEDs used outdoors, such as traffic signals or in-pavement signal

lights, and that are utilized in climates where the temperature within the luminaire gets

very hot, could result in low signal intensities or even failure. LEDs maintain consistent

light output even in cold temperatures, unlike traditional lighting methods. Consequently,

LED technology may be a good replacement in areas such as supermarket freezer lighting

and will last longer than other technologies. Because LEDs do not generate as much heat

as incandescent bulbs, they are an energy-efficient technology to use in such applications

such as freezers. On the other hand, because they do not generate much heat, ice and

snow may build up on the LED luminaire in colder climates. This has been a problem

plaguing airport runway lighting, although some research has been done to try to develop

heat sink technologies in order to transfer heat to alternative areas of the luminaire.

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Types

LEDs are produced in a variety of shapes and sizes. The 5 mm cylindrical package (red,

fifth from the left) is the most common, estimated at 80% of world production.[citation

needed ] The color of the plastic lens is often the same as the actual color of light emitted,

but not always. For instance, purple plastic is often used for infrared LEDs, and most bluedevices have clear housings. There are also LEDs in SMT packages, such as those found

on blinkies and on cell phone keypads .The main types of LEDs are miniature, high

power devices and custom designs such as alphanumeric or multi-color.

Miniature LEDs

Different sized LEDs. 8 mm, 5 mm and 3 mm, with a wooden match-stick for scale.

These are mostly single-die LEDs used as indicators, and they come in various-sizes from

2 mm to 8 mm, through-hole and surface mount packages. They are usually simple in

design, not requiring any separate cooling body. Typical current ratings range from

around 1 mA to above 20 mA. The small scale sets a natural upper boundary on power

consumption due to heat caused by the high current density and need for heat sinking.

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STEPPER MOTORS

Stepper motors are most commonly controlled by microprocessors or custom controller

ICs and the current is often switched by stepper motor driver ICs or power transistors.

Precise motion is possible but the complexity usually lands the hobbyist's stepper motors

in the "maybe someday" parts bin. But steppers may be used for a variety of applications

without complex circuitry or programming. At first glance the stepper motor looks a bit

intimidating since there are at least four wires and often there are six. Most steppers have

two independent windings and some are center-tapped, hence the four or six wires. A

quick ohmmeter check will determine which wires belong together and the center-tap

may be identified by measuring the resistance between the wires; the center-tap will

measure 1/2 the total winding resistance to either end of the coil. Tie the wires that belong together in a knot and tie another knot in the center-tap wire for easy

identification later. Stepper motors have become quite abundant and are available in all

shapes and sizes from many surplus dealers. Experimenters can also salvage excellent

steppers from old office and computer equipment. Steppers move in small increments

usually indicated on the label in degrees. To make a stepper motor spin in one direction

current is passed through one winding, then the other, then through the first winding with

the opposite polarity, then the second with flipped polarity, too. This sequence is repeated

for continuous rotation. The direction of rotation depends upon which winding is the

"leader" and which is the "follower". The rotation will reverse if either winding is

reversed. The center-tapped versions simplify the reversal of current since the center-tap

may be tied to Vcc and each end of the coil may be alternately pulled to ground. Non-

tapped motors require a bipolar drive voltage or a bit more switching circuitry. If current

is applied to both windings, the stepper will settle between two steps (this is often called

a "half-step"). Taking the half-step idea to the extreme, one could apply two quadrature

sine waves to the windings and get very smooth rotation. This technique would not be

particularly efficient since the controller would be dissipating at least as much power as

the motor but, if smooth motion is required, it might be worth a try! Or, for those who

don't mind complexity, the sine waves could be efficiently approximated by using

variable duty-cycle pulses. But the purpose here is to get those motors out of the junk

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minimum reluctance occurs with minimum gap, hence the rotor points are attracted

toward the stator magnet poles. Hybrid stepper motors are named because they use a

combination of PM and VR techniques to achieve maximum power in a small package

size.

There are two basic winding arrangements for the electromagnetic coils in a two phase

stepper motor: bipolar and unipolar.

Unipolar motors

A unipolar stepper motor has two windings per phase, one for each direction of magnetic

field. Since in this arrangement a magnetic pole can be reversed without switching the

direction of current, the commutation circuit can be made very simple (e.g. a single

transistor) for each winding. Typically, given a phase, one end of each winding is madecommon: giving three leads per phase and six leads for a typical two phase motor. Often,

these two phase commons are internally joined, so the motor has only five leads.

A microcontroller or stepper motor controller can be used to activate the drive transistors

in the right order, and this ease of operation makes unipolar motors popular with

hobbyists; they are probably the cheapest way to get precise angular movements.

Unipolar stepper motor coils

(For the experimenter, one way to distinguish common wire from a coil-end wire is by

measuring the resistance. Resistance between common wire and coil-end wire is always

half of what it is between coil-end and coil-end wires. This is because there is twice the

length of coil between the ends and only half from center (common wire) to the end.) A

quick way to determine if the stepper motor is working is to short circuit every two pairsand try turning the shaft, whenever a higher than normal resistance is felt, it indicates that

the circuit to the particular winding is closed and that the phase is working.

Bipolar motor

Bipolar motors have a single winding per phase. The current in a winding needs to be

reversed in order to reverse a magnetic pole, so the driving circuit must be more

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complicated; typically with an H-bridge arrangement (however there are several off the

shelf driver chips available to make this a simple affair). There are two leads per phase,

none are common.

Static friction effects using an H-bridge have been observed with certain drive

topologies...

Because windings are better utilized, they are more powerful than a unipolar motor of the

same weight. This is due to the physical space occupied by the windings. A unipolar

motor has twice the amount of wire in the same space, but only half used at any point in

time, hence is 50% efficient (or approximately 70% of the torque output available).

Though bipolar is more complicated to drive, the abundance of driver chips means this is

much less difficult to achieve.

An 8-lead stepper is wound like a unipolar stepper, but the leads are not joined tocommon internally to the motor. This kind of motor can be wired in several

configurations:

Unipolar.

Bipolar with series windings. This gives higher inductance but lower current per

winding.

Bipolar with parallel windings. This requires higher current but can perform better

as the winding inductance is reduced.

Bipolar with a single winding per phase. This method will run the motor on only

half the available windings, which will reduce the available low speed torque but

require less current.

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BLOCK DIAGRAM

DESCRIPTION

OPERATION

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CIRCUIT DIAGRAM

OBSERVATIONS

CONCLUSION

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Documents

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