A light-emitting diode, usually called an LED (pronounced /ˌɛliːˈdiː/),is a semiconductor diode that emits incoherent narrow-spectrum light when electrically biased in the forward direction of the p-n junction, as in the common LED circuit. This effect is a form of electroluminescence.
A LED is usually a small area light source, often with optics added to the chip to shape its radiation pattern and assist in reflection.LEDs are often used as small indicator lights on electronic devices and increasingly in higher power applications such as flashlights and area lighting. The color of the emitted light depends on the composition and condition of the semiconducting material used, and can be infrared, visible, or ultraviolet. LEDs can also be used as a regular household light source. Besides lighting, interesting applications include sterilization of water and disinfection of devices.
Discovery and development
The first known report of a light-emitting solid-state diode was made in 1907 by the British experimenter H. J. Round of Marconi Labs. Russian Oleg Vladimirovich Losev independently created the first LED in the mid 1920s; his research, though distributed in Russian, German and British scientific journals, was ignored,and no practical use was made of the discovery for several decades. Rubin Braunstein of the Radio Corporation of America reported on infrared emission from gallium arsenide (GaAs) and other semiconductor alloys in 1955. Braunstein observed infrared emission generated by simple diode structures using GaSb, GaAs, InP, and Ge-Si alloys cooled by liquid nitrogen to 77 K. Experimenters at Texas Instruments, Bob Biard and Gary Pittman, found in 1961 that gallium arsenide gave off infrared radiation when electric current was applied. Biard and Pittman were able to establish the priority of their work and received the patent for the infrared light-emitting diode.
The first practical visible-spectrum (red) LED was developed by Nick Holonyak Jr. in 1962, then of the General Electric Company and later with the University of Illinois at Urbana-Champaign and is seen as the "father of the light-emitting diode".Holonyak's former graduate student, M. George Craford, invented in 1972 the first yellow LED and 10x brighter red and red-orange LEDs.
Shuji Nakamura of Nichia Corporation of Japan demonstrated the first high-brightness blue LED based on InGaN, borrowing on critical developments in GaN nucleation on sapphire substrates and the demonstration of p-type doping of GaN which were developed by I. Akasaki and H. Amano in Nagoya. In the 1995 Alberto Barbieri at the Cardiff University Laboratory (GB) investigated the Efficiency and Reliability of high-brightness LED demonstrating very high result by using a transparent contact made by indium tin oxide (ITO) on (AlGaInP/GaAs) LED. The existence of the blue LED and high efficiency quickly carried to the first white LED, which employed a Y3Al5O12:Ce, or "YAG", phosphor coating to mix yellow (down-converted) light with blue to produce light that appears white. Nakamura was awarded the 2006 Millennium Technology Prize for his invention.
Practical use
The first commercial LEDs were commonly used as replacements for incandescent indicators, and in seven-segment displays, first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as TVs, radios, telephones, calculators, and even watches. These red LEDs were bright enough only for use as indicators, as the light output was not enough to illuminate an area. Later, other colors became widely available and also appeared in appliances and equipment. As the LED materials technology became more advanced, the light output was increased, while maintaining the efficiency and the reliability to an acceptable level, causing LEDs to become bright enough to be used for illumination.
Most LEDs were made in the very common 5 mm T1³⁄₄ and 3 mm T1 packages, but with higher power, it has become increasingly necessary to shed excess heat in order to maintain reliability, so more complex packages adapted for efficient heat dissipation are becoming common. Packages for state-of-the-art high power LEDs bear little resemblance to early LEDs (see, for example, Philips Lumileds).
Physical principles:-
Like a normal diode, the LED consists of a chip of semiconducting material impregnated, or doped, with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. Charge-carriers—electrons and holes—flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon.
The wavelength of the light emitted, and therefore its color, depends on the band gap energy of the materials forming the p-n junction. In silicon or germanium diodes, the electrons and holes recombine by a non-radiative transition which produces no optical emission, because these are indirect band gap materials. The materials used for the LED have a direct band gap with energies corresponding to near-infrared, visible or near-ultraviolet light.
LED development began with infrared and red devices made with gallium arsenide. Advances in materials science have made possible the production of devices with ever-shorter wavelengths, producing light in a variety of colors.
LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on its surface. P-type substrates, while less common, occur as well. Many commercial LEDs, especially GaN/InGaN, also use sapphire substrate.
Light extraction
Substrates that are transparent to the emitted wavelength, and backed by a reflective layer, and light spreading layer, increase the LED efficiency. The refractive index of the package material should match the index of the semiconductor, otherwise the produced light gets partially reflected back into the semiconductor, where it may be absorbed and turned into additional heat, thus lowering the efficiency. This type of reflection also occurs at the surface of the package if the LED is coupled to a medium with a different refractive index such as a glass fiber or air. The refractive index of most LED semiconductors is quite high, so in almost all cases the LED is coupled into a much lower-index medium. The large index difference makes the reflection quite substantial (per the Fresnel coefficients), and this is usually one of the dominant causes of LED inefficiency. Often more than half of the emitted light is reflected back at the LED-package and package-air interfaces. The reflection is most commonly reduced by using a dome-shaped (half-sphere) package with the diode in the center so that the outgoing light rays strike the surface perpendicularly, at which angle the reflection is minimized. An anti-reflection coating may be added as well. The package may be cheap plastic, which may be colored, but this is only for cosmetic reasons or to improve the contrast ratio; the color of the packaging does not substantially affect the color of the light emitted. Other strategies for reducing the impact of the interface reflections include designing the LED to reabsorb and reemit the reflected light (called photon recycling) and manipulating the microscopic structure of the surface to reduce the reflectance, by introducing random roughness, creating programmed moth eye surface patterns. Recently Photonic crystal have also been used to minimize back-reflections.In December 2007, scientists at Glasgow University claimed to have found a way to make Light Emitting Diodes brighter and use less power than energy efficient light bulbs currently on the market by imprinting holes into billions of LEDs in a new and cost effective method using a process known as nanoimprint lithography.
Materials
Conventional LEDs are made from a variety of inorganic semiconductor materials, producing the following colors:
Aluminium gallium arsenide (AlGaAs) — red and infrared
Aluminium gallium phosphide (AlGaP) — green
Aluminium gallium indium phosphide (AlGaInP) — high-brightness orange-red, orange, yellow, and green
Gallium arsenide phosphide (GaAsP) — red, orange-red, orange, and yellow
Gallium phosphide (GaP) — red, yellow and green
Gallium nitride (GaN) — green, pure green (or emerald green), and blue also white (if it has an AlGaN Quantum Barrier)
Indium gallium nitride (InGaN) — 450–470 nm — near ultraviolet, bluish-green and blue
Silicon carbide (SiC) as substrate — blue
Silicon (Si) as substrate — blue (under development)
Sapphire (Al2O3) as substrate — blue
Zinc selenide (ZnSe) — blue
Diamond (C) — ultraviolet
Aluminium nitride (AlN), aluminium gallium nitride (AlGaN), aluminium gallium indium nitride (AlGaInN) — near to far ultraviolet (down to 210 nm)
With this wide variety of colors, arrays of multicolor LEDs can be designed to produce unconventional color patterns.
Monday, July 14, 2008
Friday, June 20, 2008
LED
A LED lamp is a type of solid state lighting (SSL) that utilizes light-emitting diodes (LEDs) as a source of illumination rather than electrical filaments or gas.
LED lamps (also called LED bars or Illuminators) are usually clusters of LEDs in a suitable housing. They come in different shapes, including the standard light bulb shape with a large E27 Edison screw and MR16 shape with a bi-pin base. Other models might have a small Edison E14 fitting, GU5.3 (Bipin cap) or GU10 (bayonet socket). This includes low voltage (typically 12 V halogen-like) varieties and replacements for regular AC mains (120-240 V AC) lighting. Currently the latter are less widely available but this is changing rapidly.
A single LED die can produce only a limited amount of light, and only a single color at a time. To produce the white light necessary for SSL, light spanning the visible spectrum (red, green, and blue) must be generated in approximately correct proportions. To achieve this, three approaches are used for generating white light with LEDs: wavelength conversion, color mixing, and most recently Homoepitaxial ZnSe.
Wavelength conversion involves converting some or all of the LED’s output into visible wavelengths. Methods used to accomplish this feat include:
Blue LED & yellow phosphor – Considered the least expensive method for producing white light. Blue light from an LED is used to excite a phosphor which then re-emits yellow light. This balanced mixing of yellow and blue lights results in the appearance of white light, but produces poor color rendition (i.e., has low CRI).
Blue LED & several phosphors – Similar to the process involved with yellow phosphors, except that each excited phosphor re-emits a different color. Similarly, the resulting light is combined with the originating blue light to create white light. The resulting light, however, has a richer and broader wavelength spectrum and produces a higher color-quality light, albeit at an increased cost.
Ultraviolet (UV) LED & red, green, & blue phosphors – The UV light is used to excite the different phosphors, which are doped at measured amounts. The colors are mixed resulting in a white light with the richest and broadest wavelength spectrum.
Blue LED & quantum dots – A process by which a thin layer of nanocrystal particles containing 33 or 34 pairs of atoms, primarily cadmium and selenium, are coated on top of the LED. The blue light excites the quantum dots, resulting in a white light with a wavelength spectrum similar to UV LEDs.
Color mixing involves using multiple colors of LEDs in a lamp to produce white light. Such lamps contain a minimum of two LEDs (blue and yellow), but can also have three (red, blue, and green) or four (red, blue, green, and yellow). As no phosphors are used, there is no energy lost in the conversion process, thereby exhibiting the potential for higher efficiency.
Homoepitaxial ZnSe is a technology developed by Sumomito Electric where a LED is grown on a ZnSe substrate, which simultaneously produces blue light from the active region and yellow emission from the substrate. The resulting white light has a wavelength spectrum on par with UV LEDs. No phosphors are used, resulting in a higher efficiency white LED.
To be considered SSL, however, a multitude of LEDs must be placed close together in a lamp to add their illuminating effects. This is because an individual LED produces only a small amount of light, thereby limiting its effectiveness as a replacement light source. In the case where white LEDs are utilized in SSL, this is a relatively simple task, as all LEDs are of the same color and can be arranged in any fashion. When using the color-mixing method, however, it is more difficult to generate equivalent brightness when compared to using white LEDs in a similar lamp size. Furthermore, degradation of different LEDs at various times in a color-mixed lamp can lead to an uneven color output. Because of the inherent benefits and greater number of applications for white LED based SSL, most designs focus on utilizing them exclusively.
Driving LEDs
LEDs have very low dynamic resistance, with the same voltage drop for widely varying currents. Consequently they can not connect direct to most power sources without causing self destruction. A current control ballast is normally used, which is sometimes constant current.
Indicator LEDs
Miniature indicator LEDs are normally driven from low voltage DC via a current limiting resistor. Currents of 2mA, 10mA and 20mA are common. Some low current indicators are only rated to 2mA, and should not be driven at higher current.
Sub-mA indicators may be made by driving ultrabright LEDs at very low current. Efficacy tends to reduce at low currents, but indicators running on 100uA are still practical. The cost of ultrabrights is higher than 2mA indicator LEDs.
LEDs have a low max repeat reverse voltage rating, ranging from apx 2v to 5v, and this can be a problem in some applications. Back to back LEDs are immune to this problem. These are available in single color as well as bicolor types. There are various strategies for reverse voltage handling.
In niche applications such as IR therapy, LEDs are often driven at far above rated current. This causes high failure rate and occasional LED explosions. Thus many parallel strings are used, and a safety screen and ongoing maintenance are required.
Alphanumeric LEDs
These use the same drive strategy as indicator LEDs, the only difference being the larger number of channels, each with its own resistor. 7 segment and starburst LED arrays are available in both common anode or common cathode forms.
Lighting LEDs on mains
A CR dropper (capacitor & resistor) followed by full wave rectification is the usual ballast with mains driven series-parallel LED clusters.
A single series string would minimise dropper losses, but one LED failure would extinguish the whole string. Parallelled strings increase reliability. In practice usually 3 strings or more are used.
Operation on square wave and modified sine wave (MSW) sources, such as many inverters, causes heavily increased resistor dissipation in CR droppers, and LED ballasts designed for sine wave use tend to burn on non-sine waveforms. The non-sine waveform also causes high peak LED currents, heavily shortening LED life. An inductor & rectifier makes a more suitable ballast for such use, and other options are also possible.
Lighting LEDs on low voltage
LEDs are normally operated in parallel strings of series LEDs, with the total LED voltage typically adding up to around 2/3 of the supply voltage, and resistor current control for each string.
In resistor-drive devices, LED current is then proportional to power supply (PSU) voltage minus total LED string voltage. Where battery sources are used, the PSU voltage can vary widely, causing large changes in LED current and therefore color and light output. For such applications, a constant current regulator is preferred to resistor control. Low drop-out (LDO) constant current regs also allow the total LED string voltage to be a higher percentage of PSU voltage, resulting in improved efficiency and reduced power use.
Torches run one or more lighting LEDs on a low voltage battery. These usually use a resistor ballast.
In disposable coin cell powered keyring type LED lights, the resistance of the cell itself is usually the only current limiting device. The cell should not therefore be replaced with a lower resistance type, such as one using a different battery chemistry.
Finally, an LED can be run from a single cell by use of a constant current switched mode inverter. While adding additional expense, this method provides a high level of color and brightness control, and ensures longer LED lifetime.
Comparison to other lighting technologies
Incandescent lamps (light bulbs) create light by running electricity through a thin filament, thereby heating the filament to a very high temperature and producing visible light. The incandescing process, however, is highly inefficient, as over 98% of its energy input is emitted as heat.[citation needed] Incandescent lamps, however, are relatively inexpensive to produce. The typical lifespan of a mains incandescent lamp is around 1,000 hours.[citation needed]
Fluorescent lamps (light bulbs) work by passing electricity through mercury vapor, which in turn produces ultraviolet light. The ultraviolet light is then absorbed by a phosphor coating inside the lamp, causing it to glow, or fluoresce. While the heat generated by fluorescent lamps is much less than its incandescent counterpart, energy is still lost in generating the ultraviolet light and converting this light into visible light. In addition, and should the lamp break, exposure to mercury can occur, though the levels involved are not considered hazardous. Linear fluorescent lamps are typically five to six times the cost of incandescent lamps[citation needed], but have life spans around 10,000 and 20,000 hours. Lifetime varies from 1,200 hours to 20,000 hours for compact fluorescent lamps.
Neon lamp (light bulbs) used like night-lamp in children's room. Typically a 230 V (in Europe) is rated 0.5 W of power.
SSL/LEDs LEDs come in multiple colors, which are produced without the need for filters. A white SSL can be comprised of a single high-power LED, multiple white LEDs, or from LEDs of different colors mixed to produce white light. The inherent advantages and disadvantages of SSL are currently the same as those of a LED. Advantages include:
High efficiency - LEDs are now available that reliably offer over 100 lumens from a one-watt device, or much higher outputs at higher drive currents
Small size - provides design flexibility, arranged in rows, rings, clusters, or individual points
High durability - no filament or tube to break
Life span - in properly engineered lamps, LEDs can last 50,000 - 60,000 hours
Full dimmability – unlike fluorescent lamps, LEDs can be dimmed using pulse-width modulation (PWM - turning the light on and off very quickly at varying intervals). This also allows full color mixing in lamps with LEDs of different colors.
Mercury-free - unlike fluorescent and most HID technologies, LEDs contain no hazardous mercury or halogen gases.
Challenges
The current manufacturing process of white LEDs has not matured enough for them to be produced at low enough cost for widespread use. There are multiple manufacturing hurdles that must be overcome. The process used to deposit the active semiconductor layers of the LED must be improved to increase yields and manufacturing throughput. Problems with phosphors, which are needed for their ability to emit a broader wavelength spectrum of light, have also been an issue. In particular, the inability to tune the absorption and emission, and inflexibility of form have been issues in taking advantage of the phosphors spectral capabilities.
More apparent to the end user, however, is the low Color Rendering Index (CRI) of current LEDs. The current generation of LEDs, which employs mostly blue LED chip + yellow phosphor, has a CRI around 70, which is much too low for widespread use in indoor lighting. (CRI is used to measure how accurately a lighting source renders the color of objects. Sunlight and some incandescent lamps have a perfect CRI of 100, while white fluorescent lamps have CRI varying from the 50s to 95.) Better CRI LEDs are more expensive, and more research & development is needed to reduce costs. End user costs are still too high to make it a viable option, for instance, Maplin's website quotes comparable LED spots at £9.99 GBP against the standard Halogen lamp twin pack which comes in at £6.49 GBP(or roughly £3.25 GBP each).
Variations of CCT (color correlated temperature) at different viewing angles present another obstacle against widespread use of white LED. It has been shown, that CCT variations can exceed 500 K, which is clearly noticeable by human observer, who is normally capable of distinguishing CCT differences of 50 to 100 K in range from 2000 K to 6000 K, which is the range of CCT variations of daylight.
LEDs also have limited temperature tolerance and falling efficiency as temperature rises. This limits the total LED power that can practically be fitted into lamps that physically replace existing filament & compact fluorescent types. R&D is needed to improve thermal characteristics.
Applications:-
Traffic lights
Automotive lighting
Stage lighting
Bicycle lighting
Electric torches (flashlights)
Domestic lighting
Billboard displays
Floodlighting of buildings
Display lighting in art galleries to achieve a low heating effect on pictures etc.
Train lights (Now common on nearly all modern and most older MU's and Loco's in the UK)
LED lamps (also called LED bars or Illuminators) are usually clusters of LEDs in a suitable housing. They come in different shapes, including the standard light bulb shape with a large E27 Edison screw and MR16 shape with a bi-pin base. Other models might have a small Edison E14 fitting, GU5.3 (Bipin cap) or GU10 (bayonet socket). This includes low voltage (typically 12 V halogen-like) varieties and replacements for regular AC mains (120-240 V AC) lighting. Currently the latter are less widely available but this is changing rapidly.
A single LED die can produce only a limited amount of light, and only a single color at a time. To produce the white light necessary for SSL, light spanning the visible spectrum (red, green, and blue) must be generated in approximately correct proportions. To achieve this, three approaches are used for generating white light with LEDs: wavelength conversion, color mixing, and most recently Homoepitaxial ZnSe.
Wavelength conversion involves converting some or all of the LED’s output into visible wavelengths. Methods used to accomplish this feat include:
Blue LED & yellow phosphor – Considered the least expensive method for producing white light. Blue light from an LED is used to excite a phosphor which then re-emits yellow light. This balanced mixing of yellow and blue lights results in the appearance of white light, but produces poor color rendition (i.e., has low CRI).
Blue LED & several phosphors – Similar to the process involved with yellow phosphors, except that each excited phosphor re-emits a different color. Similarly, the resulting light is combined with the originating blue light to create white light. The resulting light, however, has a richer and broader wavelength spectrum and produces a higher color-quality light, albeit at an increased cost.
Ultraviolet (UV) LED & red, green, & blue phosphors – The UV light is used to excite the different phosphors, which are doped at measured amounts. The colors are mixed resulting in a white light with the richest and broadest wavelength spectrum.
Blue LED & quantum dots – A process by which a thin layer of nanocrystal particles containing 33 or 34 pairs of atoms, primarily cadmium and selenium, are coated on top of the LED. The blue light excites the quantum dots, resulting in a white light with a wavelength spectrum similar to UV LEDs.
Color mixing involves using multiple colors of LEDs in a lamp to produce white light. Such lamps contain a minimum of two LEDs (blue and yellow), but can also have three (red, blue, and green) or four (red, blue, green, and yellow). As no phosphors are used, there is no energy lost in the conversion process, thereby exhibiting the potential for higher efficiency.
Homoepitaxial ZnSe is a technology developed by Sumomito Electric where a LED is grown on a ZnSe substrate, which simultaneously produces blue light from the active region and yellow emission from the substrate. The resulting white light has a wavelength spectrum on par with UV LEDs. No phosphors are used, resulting in a higher efficiency white LED.
To be considered SSL, however, a multitude of LEDs must be placed close together in a lamp to add their illuminating effects. This is because an individual LED produces only a small amount of light, thereby limiting its effectiveness as a replacement light source. In the case where white LEDs are utilized in SSL, this is a relatively simple task, as all LEDs are of the same color and can be arranged in any fashion. When using the color-mixing method, however, it is more difficult to generate equivalent brightness when compared to using white LEDs in a similar lamp size. Furthermore, degradation of different LEDs at various times in a color-mixed lamp can lead to an uneven color output. Because of the inherent benefits and greater number of applications for white LED based SSL, most designs focus on utilizing them exclusively.
Driving LEDs
LEDs have very low dynamic resistance, with the same voltage drop for widely varying currents. Consequently they can not connect direct to most power sources without causing self destruction. A current control ballast is normally used, which is sometimes constant current.
Indicator LEDs
Miniature indicator LEDs are normally driven from low voltage DC via a current limiting resistor. Currents of 2mA, 10mA and 20mA are common. Some low current indicators are only rated to 2mA, and should not be driven at higher current.
Sub-mA indicators may be made by driving ultrabright LEDs at very low current. Efficacy tends to reduce at low currents, but indicators running on 100uA are still practical. The cost of ultrabrights is higher than 2mA indicator LEDs.
LEDs have a low max repeat reverse voltage rating, ranging from apx 2v to 5v, and this can be a problem in some applications. Back to back LEDs are immune to this problem. These are available in single color as well as bicolor types. There are various strategies for reverse voltage handling.
In niche applications such as IR therapy, LEDs are often driven at far above rated current. This causes high failure rate and occasional LED explosions. Thus many parallel strings are used, and a safety screen and ongoing maintenance are required.
Alphanumeric LEDs
These use the same drive strategy as indicator LEDs, the only difference being the larger number of channels, each with its own resistor. 7 segment and starburst LED arrays are available in both common anode or common cathode forms.
Lighting LEDs on mains
A CR dropper (capacitor & resistor) followed by full wave rectification is the usual ballast with mains driven series-parallel LED clusters.
A single series string would minimise dropper losses, but one LED failure would extinguish the whole string. Parallelled strings increase reliability. In practice usually 3 strings or more are used.
Operation on square wave and modified sine wave (MSW) sources, such as many inverters, causes heavily increased resistor dissipation in CR droppers, and LED ballasts designed for sine wave use tend to burn on non-sine waveforms. The non-sine waveform also causes high peak LED currents, heavily shortening LED life. An inductor & rectifier makes a more suitable ballast for such use, and other options are also possible.
Lighting LEDs on low voltage
LEDs are normally operated in parallel strings of series LEDs, with the total LED voltage typically adding up to around 2/3 of the supply voltage, and resistor current control for each string.
In resistor-drive devices, LED current is then proportional to power supply (PSU) voltage minus total LED string voltage. Where battery sources are used, the PSU voltage can vary widely, causing large changes in LED current and therefore color and light output. For such applications, a constant current regulator is preferred to resistor control. Low drop-out (LDO) constant current regs also allow the total LED string voltage to be a higher percentage of PSU voltage, resulting in improved efficiency and reduced power use.
Torches run one or more lighting LEDs on a low voltage battery. These usually use a resistor ballast.
In disposable coin cell powered keyring type LED lights, the resistance of the cell itself is usually the only current limiting device. The cell should not therefore be replaced with a lower resistance type, such as one using a different battery chemistry.
Finally, an LED can be run from a single cell by use of a constant current switched mode inverter. While adding additional expense, this method provides a high level of color and brightness control, and ensures longer LED lifetime.
Comparison to other lighting technologies
Incandescent lamps (light bulbs) create light by running electricity through a thin filament, thereby heating the filament to a very high temperature and producing visible light. The incandescing process, however, is highly inefficient, as over 98% of its energy input is emitted as heat.[citation needed] Incandescent lamps, however, are relatively inexpensive to produce. The typical lifespan of a mains incandescent lamp is around 1,000 hours.[citation needed]
Fluorescent lamps (light bulbs) work by passing electricity through mercury vapor, which in turn produces ultraviolet light. The ultraviolet light is then absorbed by a phosphor coating inside the lamp, causing it to glow, or fluoresce. While the heat generated by fluorescent lamps is much less than its incandescent counterpart, energy is still lost in generating the ultraviolet light and converting this light into visible light. In addition, and should the lamp break, exposure to mercury can occur, though the levels involved are not considered hazardous. Linear fluorescent lamps are typically five to six times the cost of incandescent lamps[citation needed], but have life spans around 10,000 and 20,000 hours. Lifetime varies from 1,200 hours to 20,000 hours for compact fluorescent lamps.
Neon lamp (light bulbs) used like night-lamp in children's room. Typically a 230 V (in Europe) is rated 0.5 W of power.
SSL/LEDs LEDs come in multiple colors, which are produced without the need for filters. A white SSL can be comprised of a single high-power LED, multiple white LEDs, or from LEDs of different colors mixed to produce white light. The inherent advantages and disadvantages of SSL are currently the same as those of a LED. Advantages include:
High efficiency - LEDs are now available that reliably offer over 100 lumens from a one-watt device, or much higher outputs at higher drive currents
Small size - provides design flexibility, arranged in rows, rings, clusters, or individual points
High durability - no filament or tube to break
Life span - in properly engineered lamps, LEDs can last 50,000 - 60,000 hours
Full dimmability – unlike fluorescent lamps, LEDs can be dimmed using pulse-width modulation (PWM - turning the light on and off very quickly at varying intervals). This also allows full color mixing in lamps with LEDs of different colors.
Mercury-free - unlike fluorescent and most HID technologies, LEDs contain no hazardous mercury or halogen gases.
Challenges
The current manufacturing process of white LEDs has not matured enough for them to be produced at low enough cost for widespread use. There are multiple manufacturing hurdles that must be overcome. The process used to deposit the active semiconductor layers of the LED must be improved to increase yields and manufacturing throughput. Problems with phosphors, which are needed for their ability to emit a broader wavelength spectrum of light, have also been an issue. In particular, the inability to tune the absorption and emission, and inflexibility of form have been issues in taking advantage of the phosphors spectral capabilities.
More apparent to the end user, however, is the low Color Rendering Index (CRI) of current LEDs. The current generation of LEDs, which employs mostly blue LED chip + yellow phosphor, has a CRI around 70, which is much too low for widespread use in indoor lighting. (CRI is used to measure how accurately a lighting source renders the color of objects. Sunlight and some incandescent lamps have a perfect CRI of 100, while white fluorescent lamps have CRI varying from the 50s to 95.) Better CRI LEDs are more expensive, and more research & development is needed to reduce costs. End user costs are still too high to make it a viable option, for instance, Maplin's website quotes comparable LED spots at £9.99 GBP against the standard Halogen lamp twin pack which comes in at £6.49 GBP(or roughly £3.25 GBP each).
Variations of CCT (color correlated temperature) at different viewing angles present another obstacle against widespread use of white LED. It has been shown, that CCT variations can exceed 500 K, which is clearly noticeable by human observer, who is normally capable of distinguishing CCT differences of 50 to 100 K in range from 2000 K to 6000 K, which is the range of CCT variations of daylight.
LEDs also have limited temperature tolerance and falling efficiency as temperature rises. This limits the total LED power that can practically be fitted into lamps that physically replace existing filament & compact fluorescent types. R&D is needed to improve thermal characteristics.
Applications:-
Traffic lights
Automotive lighting
Stage lighting
Bicycle lighting
Electric torches (flashlights)
Domestic lighting
Billboard displays
Floodlighting of buildings
Display lighting in art galleries to achieve a low heating effect on pictures etc.
Train lights (Now common on nearly all modern and most older MU's and Loco's in the UK)
Friday, June 13, 2008
Flashlight
A flashlight (also called an electric torch or torch) is a portable electric spotlight which emits light from a small incandescent lightbulb, or from one or more light-emitting diodes (LEDs). The light source is mounted in a housing which contains a parabolic reflector, a clear protective lens, a power source (typically electric batteries), and an electric power switch.
While most flashlights are intended to be held in the hand, there are also helmet-mounted flashlights designed for miners and campers. Some types of flashlights can be powered by hand-cranked dynamos or electromagnetic induction. It is known as a flashlight mainly in the United States and Canada and as a torch or electric torch in most Commonwealth countries.
A typical flashlight consists of a small incandescent lightbulb with associated parabolic reflector, powered by electric batteries, and with an electric power switch. The components are mounted in a housing that contains the necessary electric circuit and provides ease of handling, a means of access to the batteries for replacement, and a clear covering over the lightbulb for its protection.
Although a relatively simple device, its invention did not occur until the late 19th century because it depended upon the earlier invention of the electric battery and incandescent light bulb.Incandescent flashlights use bulbs that contain a heated-up coil of tungsten wire, which gives off light energy as well as heat.The bulbs are filled with gas (usually argon perhaps with a trace of a Halogen,in higher quality models, Xenon is used.) A popular example of an incandescent flashlight is the Maglite by Mag Instrument. and are capable of producing upwards of 4,000 lumens.Flashlight hobbyists often modify Maglites by replacing the bulb, reflector, switch, and batteries with more powerful options, producing much more light than a stock Maglite.
Recently, flashlights which use light-emitting diodes (LEDs) instead of conventional lightbulbs have become available. LEDs have existed for decades, mainly as low-power indicator lights. In 1999, Lumileds Corporation of San Jose, CA, introduced the Luxeon LED, a high-power white-light emitter. For the first time this made possible LED flashlights with power and running time better than some incandescent lights. The first Luxeon LED flashlight was the Arc LS in 2001.
LEDs can be significantly more efficient at lower power levels, hence use less battery energy than normal lightbulbs. Such flashlights have longer battery lifetimes, in some cases hundreds of hours, although the LED efficiency advantage diminishes at higher power levels. LEDs also survive sharp blows that often break conventional lightbulbs.
LED flashlights are often electronically regulated to maintain constant light output as the batteries fade. By contrast a non-regulated flashlight becomes progressively dimmer, sometimes spending much of the total running time below 50 percent brightness level.
A common misconception about LED-based flashlights is that they generate no heat. While lower-power LED flashlights generate little heat, more powerful LED lights do generate significant amounts of heat – although not as radiant energy – as the semiconductor junction inherently dissipates heat. For this reason higher-powered LED flashlights usually have aluminum bodies and can become quite warm during use. The use of aluminum is largely due to its thermal properties, acting as a heatsink for the high-power LED. Very few high-output LED flashlights use a plastic body due to plastic being a thermal insulator rather than a conductor.
Another less common type of flashlight is an HID flashlight, or High Intensity Discharge. It works by passing an electric current through a ball of ionized gas, which glows very brightly.
Some advantages of this design are that they produce more light than an incandescent flashlight using the same amount of electricity, and the bulb will last a longer time and is more shock resistant than a regular incandescent bulb. However, they are more expensive and are usually rather bulky. An example of an HID flashlight is the Surefire Hellfire Weaponlight.
High-end flashlights:-
High end lights often go for as much as several hundreds of pounds/euros/dollars. Using metals such as titanium, steel, or even silver, and often being limited in production they often end up as collector's items trading at many times their original sales price. Such flashlights are very advanced, using special batteries, have adjustable brightness levels, waterproof ratings, and are very bright. As a unique example of a high end manufacturer, with non-cylindrical, unique design, Lumencraft was one of the first manufacturer to create designs that cater more towards a higher end design and art-conscious market rather than the tactical military and law enforcement markets.
A headlamp is a flashlight worn on the head for hands-free operation. Powerful headlamps mounted on helmets have been used in mining for decades, but general-purpose ones with fabric straps are now also available.
Sometimes a light is mounted to a handgun or rifle.See also Streamlight and SureFire.
Most flashlights are cylindrical in design, with the lamp assembly attached to one end. However, early designs came in a variety of shapes. Many resembled lanterns of the day, consisting largely of a box with a handle and the lamp attached to the front. Some others were made to have a similar appearance to candles. It is possible that future developments of battery and LED technology will bring interesting new designs. For instance, one very small light consists of a few LEDs with a switch, designed to be an endcap for a 9-volt battery.
While most flashlights are intended to be held in the hand, there are also helmet-mounted flashlights designed for miners and campers. Some types of flashlights can be powered by hand-cranked dynamos or electromagnetic induction. It is known as a flashlight mainly in the United States and Canada and as a torch or electric torch in most Commonwealth countries.
A typical flashlight consists of a small incandescent lightbulb with associated parabolic reflector, powered by electric batteries, and with an electric power switch. The components are mounted in a housing that contains the necessary electric circuit and provides ease of handling, a means of access to the batteries for replacement, and a clear covering over the lightbulb for its protection.
Although a relatively simple device, its invention did not occur until the late 19th century because it depended upon the earlier invention of the electric battery and incandescent light bulb.Incandescent flashlights use bulbs that contain a heated-up coil of tungsten wire, which gives off light energy as well as heat.The bulbs are filled with gas (usually argon perhaps with a trace of a Halogen,in higher quality models, Xenon is used.) A popular example of an incandescent flashlight is the Maglite by Mag Instrument. and are capable of producing upwards of 4,000 lumens.Flashlight hobbyists often modify Maglites by replacing the bulb, reflector, switch, and batteries with more powerful options, producing much more light than a stock Maglite.
Recently, flashlights which use light-emitting diodes (LEDs) instead of conventional lightbulbs have become available. LEDs have existed for decades, mainly as low-power indicator lights. In 1999, Lumileds Corporation of San Jose, CA, introduced the Luxeon LED, a high-power white-light emitter. For the first time this made possible LED flashlights with power and running time better than some incandescent lights. The first Luxeon LED flashlight was the Arc LS in 2001.
LEDs can be significantly more efficient at lower power levels, hence use less battery energy than normal lightbulbs. Such flashlights have longer battery lifetimes, in some cases hundreds of hours, although the LED efficiency advantage diminishes at higher power levels. LEDs also survive sharp blows that often break conventional lightbulbs.
LED flashlights are often electronically regulated to maintain constant light output as the batteries fade. By contrast a non-regulated flashlight becomes progressively dimmer, sometimes spending much of the total running time below 50 percent brightness level.
A common misconception about LED-based flashlights is that they generate no heat. While lower-power LED flashlights generate little heat, more powerful LED lights do generate significant amounts of heat – although not as radiant energy – as the semiconductor junction inherently dissipates heat. For this reason higher-powered LED flashlights usually have aluminum bodies and can become quite warm during use. The use of aluminum is largely due to its thermal properties, acting as a heatsink for the high-power LED. Very few high-output LED flashlights use a plastic body due to plastic being a thermal insulator rather than a conductor.
Another less common type of flashlight is an HID flashlight, or High Intensity Discharge. It works by passing an electric current through a ball of ionized gas, which glows very brightly.
Some advantages of this design are that they produce more light than an incandescent flashlight using the same amount of electricity, and the bulb will last a longer time and is more shock resistant than a regular incandescent bulb. However, they are more expensive and are usually rather bulky. An example of an HID flashlight is the Surefire Hellfire Weaponlight.
High-end flashlights:-
High end lights often go for as much as several hundreds of pounds/euros/dollars. Using metals such as titanium, steel, or even silver, and often being limited in production they often end up as collector's items trading at many times their original sales price. Such flashlights are very advanced, using special batteries, have adjustable brightness levels, waterproof ratings, and are very bright. As a unique example of a high end manufacturer, with non-cylindrical, unique design, Lumencraft was one of the first manufacturer to create designs that cater more towards a higher end design and art-conscious market rather than the tactical military and law enforcement markets.
A headlamp is a flashlight worn on the head for hands-free operation. Powerful headlamps mounted on helmets have been used in mining for decades, but general-purpose ones with fabric straps are now also available.
Sometimes a light is mounted to a handgun or rifle.See also Streamlight and SureFire.
Most flashlights are cylindrical in design, with the lamp assembly attached to one end. However, early designs came in a variety of shapes. Many resembled lanterns of the day, consisting largely of a box with a handle and the lamp attached to the front. Some others were made to have a similar appearance to candles. It is possible that future developments of battery and LED technology will bring interesting new designs. For instance, one very small light consists of a few LEDs with a switch, designed to be an endcap for a 9-volt battery.
Thursday, May 22, 2008
Prepaid "credit" cards
A prepaid credit card is not a credit card,as no credit is offered by the card issuer: the card-holder spends money which has been "stored" via a prior deposit by the card-holder or someone else, such as a parent or employer. However, it carries a credit-card brand (Visa, MasterCard, American Express or Discover) and can be used in similar ways just as though it were a regular credit card.
After purchasing the card, the cardholder loads it with any amount of money, up to the predetermined card limit and then uses the card to make purchases the same way as a typical credit card. Prepaid cards can be issued to minors (above 13) since there is no credit line involved. The main advantage over secured credit cards (see above section) is that you are not required to come up with $500 or more to open an account.With prepaid credit cards you are not charged any interest but you are often charged a purchasing fee plus monthly fees after an arbitrary time period. Many other fees also usually apply to a prepaid card.
Prepaid credit cards are sometimes marketed to teenagers for shopping online without having their parents complete the transaction.
Because of the many fees that apply to obtaining and using credit-card-branded prepaid cards, the Financial Consumer Agency of Canada describes them as "an expensive way to spend your own money".The agency publishes a booklet, "Pre-paid cards",which explains the advantages and disadvantages of this type of prepaid card.As well as convenient, accessible credit, credit cards offer consumers an easy way to track expenses, which is necessary for both monitoring personal expenditures and the tracking of work-related expenses for taxation and reimbursement purposes. Credit cards are accepted worldwide, and are available with a large variety of credit limits, repayment arrangement, and other perks (such as rewards schemes in which points earned by purchasing goods with the card can be redeemed for further goods and services or credit card cashback).
Some countries, such as the United States, the United Kingdom, and France, limit the amount for which a consumer can be held liable due to fraudulent transactions as a result of a consumer's credit card being lost or stolen.The low security of the credit card system presents countless opportunities for fraud. This opportunity has created a huge black market in stolen credit card numbers, which are generally used quickly before the cards are reported stolen.
The goal of the credit card companies is not to eliminate fraud, but to "reduce it to manageable levels".This implies that high-cost low-return fraud prevention measures will not be used if their cost exceeds the potential gains from fraud reduction.
Most internet fraud is done through the use of stolen credit card information which is obtained in many ways, the simplest being copying information from retailers, either online or offline. Despite efforts to improve security for remote purchases using credit cards, systems with security holes are usually the result of poor implementations of card acquisition by merchants. For example, a website that uses SSL to encrypt card numbers from a client may simply email the number from the webserver to someone who manually processes the card details at a card terminal. Naturally, anywhere card details become human-readable before being processed at the acquiring bank, a security risk is created. However, many banks offer systems where encrypted card details captured on a merchant's webserver can be sent directly to the payment processor.
Controlled Payment Numbers are another option for protecting one's credit card number: they are "alias" numbers linked to one's actual card number, generated as needed, valid for a relatively short time, with a very low limit, and typically only valid with a single merchant.
The Federal Bureau of Investigation and U.S. Postal Inspection Service are responsible for prosecuting criminals who engage in credit card fraud in the United States, but they do not have the resources to pursue all criminals. In general, federal officials only prosecute cases exceeding US $5000 in value. Three improvements to card security have been introduced to the more common credit card networks but none has proven to help reduce credit card fraud so far. First, the on-line verification system used by merchants is being enhanced to require a 4 digit Personal Identification Number (PIN) known only to the card holder. Second, the cards themselves are being replaced with similar-looking tamper-resistant smart cards which are intended to make forgery more difficult. The majority of smartcard (IC card) based credit cards comply with the EMV (Europay MasterCard Visa) standard. Third, an additional 3 or 4 digit code is now present on the back of most cards, for use in "card not present" transactions. See CVV2 for more information.
The way credit card owners pay off their balances has a tremendous effect on their credit history. All the information is collected by credit bureaus. The credit information stays on the credit report, depending on the jurisdiction and the situation, for 1, 2, 5, 7 or even 10 years after the debt is repaid.Credit card security relies on the physical security of the plastic card as well as the privacy of the credit card number. Therefore, whenever a person other than the card owner has access to the card or its number, security is potentially compromised. Merchants often accept credit card numbers without additional verification for mail order purchases. They however record the delivery address as a security measure to minimise fradulent purchases. Some merchants will accept a credit card number for in-store purchases, whereupon access to the number allows easy fraud, but many require the card itself to be present, and require a signature. Thus, a stolen card can be cancelled, and if this is done quickly, no fraud can take place in this way. For internet purchases, there is sometimes the same level of security as for mail order (number only) hence requiring only that the fraudster take care about collecting the goods, but often there are additional measures. The main one is to require a security PIN with the card, which requires that the thief have access to the card, as well as the PIN.
An additional feature to secure the credit card transaction and prohibit the use of a lost credit card is the MobiClear solution. Each transaction is authenticated through a call to the user mobile phone. The transaction is released once the transaction has been confirmed by the cardholder pushing his/her pincode during the call.
The PCI DSS is the security standard issued by The PCI SSC (Payment Card Industry Security Standards Council). This data security standard is used by acquiring banks to impose cardholder data security measures upon their merchants.
After purchasing the card, the cardholder loads it with any amount of money, up to the predetermined card limit and then uses the card to make purchases the same way as a typical credit card. Prepaid cards can be issued to minors (above 13) since there is no credit line involved. The main advantage over secured credit cards (see above section) is that you are not required to come up with $500 or more to open an account.With prepaid credit cards you are not charged any interest but you are often charged a purchasing fee plus monthly fees after an arbitrary time period. Many other fees also usually apply to a prepaid card.
Prepaid credit cards are sometimes marketed to teenagers for shopping online without having their parents complete the transaction.
Because of the many fees that apply to obtaining and using credit-card-branded prepaid cards, the Financial Consumer Agency of Canada describes them as "an expensive way to spend your own money".The agency publishes a booklet, "Pre-paid cards",which explains the advantages and disadvantages of this type of prepaid card.As well as convenient, accessible credit, credit cards offer consumers an easy way to track expenses, which is necessary for both monitoring personal expenditures and the tracking of work-related expenses for taxation and reimbursement purposes. Credit cards are accepted worldwide, and are available with a large variety of credit limits, repayment arrangement, and other perks (such as rewards schemes in which points earned by purchasing goods with the card can be redeemed for further goods and services or credit card cashback).
Some countries, such as the United States, the United Kingdom, and France, limit the amount for which a consumer can be held liable due to fraudulent transactions as a result of a consumer's credit card being lost or stolen.The low security of the credit card system presents countless opportunities for fraud. This opportunity has created a huge black market in stolen credit card numbers, which are generally used quickly before the cards are reported stolen.
The goal of the credit card companies is not to eliminate fraud, but to "reduce it to manageable levels".This implies that high-cost low-return fraud prevention measures will not be used if their cost exceeds the potential gains from fraud reduction.
Most internet fraud is done through the use of stolen credit card information which is obtained in many ways, the simplest being copying information from retailers, either online or offline. Despite efforts to improve security for remote purchases using credit cards, systems with security holes are usually the result of poor implementations of card acquisition by merchants. For example, a website that uses SSL to encrypt card numbers from a client may simply email the number from the webserver to someone who manually processes the card details at a card terminal. Naturally, anywhere card details become human-readable before being processed at the acquiring bank, a security risk is created. However, many banks offer systems where encrypted card details captured on a merchant's webserver can be sent directly to the payment processor.
Controlled Payment Numbers are another option for protecting one's credit card number: they are "alias" numbers linked to one's actual card number, generated as needed, valid for a relatively short time, with a very low limit, and typically only valid with a single merchant.
The Federal Bureau of Investigation and U.S. Postal Inspection Service are responsible for prosecuting criminals who engage in credit card fraud in the United States, but they do not have the resources to pursue all criminals. In general, federal officials only prosecute cases exceeding US $5000 in value. Three improvements to card security have been introduced to the more common credit card networks but none has proven to help reduce credit card fraud so far. First, the on-line verification system used by merchants is being enhanced to require a 4 digit Personal Identification Number (PIN) known only to the card holder. Second, the cards themselves are being replaced with similar-looking tamper-resistant smart cards which are intended to make forgery more difficult. The majority of smartcard (IC card) based credit cards comply with the EMV (Europay MasterCard Visa) standard. Third, an additional 3 or 4 digit code is now present on the back of most cards, for use in "card not present" transactions. See CVV2 for more information.
The way credit card owners pay off their balances has a tremendous effect on their credit history. All the information is collected by credit bureaus. The credit information stays on the credit report, depending on the jurisdiction and the situation, for 1, 2, 5, 7 or even 10 years after the debt is repaid.Credit card security relies on the physical security of the plastic card as well as the privacy of the credit card number. Therefore, whenever a person other than the card owner has access to the card or its number, security is potentially compromised. Merchants often accept credit card numbers without additional verification for mail order purchases. They however record the delivery address as a security measure to minimise fradulent purchases. Some merchants will accept a credit card number for in-store purchases, whereupon access to the number allows easy fraud, but many require the card itself to be present, and require a signature. Thus, a stolen card can be cancelled, and if this is done quickly, no fraud can take place in this way. For internet purchases, there is sometimes the same level of security as for mail order (number only) hence requiring only that the fraudster take care about collecting the goods, but often there are additional measures. The main one is to require a security PIN with the card, which requires that the thief have access to the card, as well as the PIN.
An additional feature to secure the credit card transaction and prohibit the use of a lost credit card is the MobiClear solution. Each transaction is authenticated through a call to the user mobile phone. The transaction is released once the transaction has been confirmed by the cardholder pushing his/her pincode during the call.
The PCI DSS is the security standard issued by The PCI SSC (Payment Card Industry Security Standards Council). This data security standard is used by acquiring banks to impose cardholder data security measures upon their merchants.
the creditcard
A credit card is a system of payment named after the small plastic card issued to users of the system. In the case of credit cards, the issuer lends money to the consumer (or the user) to be paid later to the merchant. It is different from a charge card, which requires the balance to be paid in full each month. In contrast, a credit card allows the consumer to 'revolve' their balance, at the cost of having interest charged. Most credit cards are issued by local banks or Credit Unions, and are the same shape and size, as specified by the ISO 7810 standard.Credit cards are issued after an account has been approved by the credit provider, after which cardholders can use it to make purchases at merchants accepting that card.
When a purchase is made, the credit card user agrees to pay the card issuer. The cardholder indicates his/her consent to pay, by signing a receipt with a record of the card details and indicating the amount to be paid or by entering a Personal identification number (PIN). Also, many merchants now accept verbal authorizations via telephone and electronic authorization using the Internet, known as a 'Card/Cardholder Not Present' (CNP) transaction.
Electronic verification systems allow merchants to verify that the card is valid and the credit card customer has sufficient credit to cover the purchase in a few seconds, allowing the verification to happen at time of purchase. The verification is performed using a credit card payment terminal or Point of Sale (POS) system with a communications link to the merchant's acquiring bank. Data from the card is obtained from a magnetic stripe or chip on the card; the latter system is in the United Kingdom and Ireland commonly known as Chip and PIN, but is more technically an EMV card.
Other variations of verification systems are used by eCommerce merchants to determine if the user's account is valid and able to accept the charge. These will typically involve the cardholder providing additional information, such as the security code printed on the back of the card, or the address of the cardholder.
Each month, the credit card user is sent a statement indicating the purchases undertaken with the card, any outstanding fees, and the total amount owed. After receiving the statement, the cardholder may dispute any charges that he or she thinks are incorrect (see Fair Credit Billing Act for details of the US regulations). Otherwise, the cardholder must pay a defined minimum proportion of the bill by a due date, or may choose to pay a higher amount up to the entire amount owed. The credit provider charges interest on the amount owed (typically at a much higher rate than most other forms of debt). Some financial institutions can arrange for automatic payments to be deducted from the user's bank accounts, thus avoiding late payment altogether as long as the cardholder has sufficient funds.Credit card issuers usually waive interest charges if the balance is paid in full each month, but typically will charge full interest on the entire outstanding balance from the date of each purchase if the total balance is not paid.
For example, if a user had a $1,000 transaction and repaid it in full within this grace period, there would be no interest charged. If, however, even $1.00 of the total amount remained unpaid, interest would be charged on the $1,000 from the date of purchase until the payment is received. The precise manner in which interest is charged is usually detailed in a cardholder agreement which may be summarized on the back of the monthly statement. The general calculation formula most financial institutions use to determine the amount of interest to be charged is APR/100 x ADB/365 x number of days revolved. Take the Annual percentage rate (APR) and divide by 100 then multiply to the amount of the average daily balance (ADB) divided by 365 and then take this total and multiply by the total number of days the amount revolved before payment was made on the account. Financial institutions refer to interest charged back to the original time of the transaction and up to the time a payment was made, if not in full, as RRFC or residual retail finance charge. Thus after an amount has revolved and a payment has been made, the user of the card will still receive interest charges on his statement after paying the next statement in full (in fact the statement may only have a charge for interest that collected up until the date the full balance was paid...i.e. when the balance stopped revolving).
The credit card may simply serve as a form of revolving credit, or it may become a complicated financial instrument with multiple balance segments each at a different interest rate, possibly with a single umbrella credit limit, or with separate credit limits applicable to the various balance segments. Usually this compartmentalization is the result of special incentive offers from the issuing bank, either to encourage balance transfers from cards of other issuers. In the event that several interest rates apply to various balance segments, payment allocation is generally at the discretion of the issuing bank, and payments will therefore usually be allocated towards the lowest rate balances until paid in full before any money is paid towards higher rate balances. Interest rates can vary considerably from card to card, and the interest rate on a particular card may jump dramatically if the card user is late with a payment on that card or any other credit instrument, or even if the issuing bank decides to raise its revenue.Because of intense competition in the credit card industry, credit card providers often offer incentives such as frequent flyer points, gift certificates, or cash back (typically up to 1 percent based on total purchases) to try to attract customers to their programs.
Low interest credit cards or even 0% interest credit cards are available. The only downside to consumers is that the period of low interest credit cards is limited to a fixed term, usually between 6 and 12 months after which a higher rate is charged. However, services are available which alert credit card holders when their low interest period is due to expire. Most such services charge a monthly or annual fee.A credit card's grace period is the time the customer has to pay the balance before interest is charged to the balance. Grace periods vary, but usually range from 20 to 30 days depending on the type of credit card and the issuing bank. Some policies allow for reinstatement after certain conditions are met.
Usually, if a customer is late paying the balance, finance charges will be calculated and the grace period does not apply. Finance charges incurred depend on the grace period and balance; with most credit cards there is no grace period if there is any outstanding balance from the previous billing cycle or statement (i.e. interest is applied on both the previous balance and new transactions). However, there are some credit cards that will only apply finance charge on the previous or old balance, excluding new transactions.For merchants, a credit card transaction is often more secure than other forms of payment, such as checks, because the issuing bank commits to pay the merchant the moment the transaction is authorized, regardless of whether the consumer defaults on his credit card payment (except for legitimate disputes, which are discussed below, and can result in charge backs to the merchant). In most cases, cards are even more secure than cash, because they discourage theft by the merchant's employees and reduce the amount of cash on the premises.
For each purchase, the bank charges the merchant a commission (discount fee) for this service and there may be a certain delay before the agreed payment is received by the merchant. The commission is often a percentage of the transaction amount, plus a fixed fee. In addition, a merchant may be penalized or have his ability to receive payment using that credit card restricted if there are too many cancellations or reversals of charges as a result of disputes. Some small merchants require credit purchases to have a minimum amount (usually between $5 and $10) to compensate for the transaction costs, though this is not always allowed by the credit card consortium.
In some countries, like the Nordic countries, banks guarantee payment on stolen cards only if an ID card is checked and the ID card number/civic registration number is written down on the receipt together with the signature. In these countries merchants therefore usually ask for ID. Non-Nordic citizens, who are unlikely to possess a Nordic ID card or driving license, will instead have to show their passport, and the passport number will be written down on the receipt, sometimes together with other information. Some shops use the card's PIN code for identification, and in that case showing an ID card is not necessary.A secured credit card is a type of credit card secured by a deposit account owned by the cardholder. Typically, the cardholder must deposit between 100% and 200% of the total amount of credit desired. Thus if the cardholder puts down $1000, he or she will be given credit in the range of $500–$1000. In some cases, credit card issuers will offer incentives even on their secured card portfolios. In these cases, the deposit required may be significantly less than the required credit limit, and can be as low as 10% of the desired credit limit. This deposit is held in a special savings account. Credit card issuers offer this as they have noticed that delinquencies were notably reduced when the customer perceives he has something to lose if he doesn't repay his balance.
The cardholder of a secured credit card is still expected to make regular payments, as he or she would with a regular credit card, but should he or she default on a payment, the card issuer has the option of recovering the cost of the purchases paid to the merchants out of the deposit. The advantage of the secured card for an individual with negative or no credit history is that most companies report regularly to the major credit bureaus. This allows for building of positive credit history.
Although the deposit is in the hands of the credit card issuer as security in the event of default by the consumer, the deposit will not be debited simply for missing one or two payments. Usually the deposit is only used as an offset when the account is closed, either at the request of the customer or due to severe delinquency (150 to 180 days). This means that an account which is less than 150 days delinquent will continue to accrue interest and fees, and could result in a balance which is much higher than the actual credit limit on the card. In these cases the total debt may far exceed the original deposit and the cardholder not only forfeits their deposit but is left with an additional debt.
Most of these conditions are usually described in a cardholder agreement which the cardholder signs when their account is opened.
Secured credit cards are an option to allow a person with a poor credit history or no credit history to have a credit card which might not otherwise be available. They are often offered as a means of rebuilding one's credit. Secured credit cards are available with both Visa and MasterCard logos on them. Fees and service charges for secured credit cards often exceed those charged for ordinary non-secured credit cards, however, for people in certain situations, (for example, after charging off on other credit cards, or people with a long history of delinquency on various forms of debt), secured cards can often be less expensive in total cost than unsecured credit cards, even including the security deposit.
When a purchase is made, the credit card user agrees to pay the card issuer. The cardholder indicates his/her consent to pay, by signing a receipt with a record of the card details and indicating the amount to be paid or by entering a Personal identification number (PIN). Also, many merchants now accept verbal authorizations via telephone and electronic authorization using the Internet, known as a 'Card/Cardholder Not Present' (CNP) transaction.
Electronic verification systems allow merchants to verify that the card is valid and the credit card customer has sufficient credit to cover the purchase in a few seconds, allowing the verification to happen at time of purchase. The verification is performed using a credit card payment terminal or Point of Sale (POS) system with a communications link to the merchant's acquiring bank. Data from the card is obtained from a magnetic stripe or chip on the card; the latter system is in the United Kingdom and Ireland commonly known as Chip and PIN, but is more technically an EMV card.
Other variations of verification systems are used by eCommerce merchants to determine if the user's account is valid and able to accept the charge. These will typically involve the cardholder providing additional information, such as the security code printed on the back of the card, or the address of the cardholder.
Each month, the credit card user is sent a statement indicating the purchases undertaken with the card, any outstanding fees, and the total amount owed. After receiving the statement, the cardholder may dispute any charges that he or she thinks are incorrect (see Fair Credit Billing Act for details of the US regulations). Otherwise, the cardholder must pay a defined minimum proportion of the bill by a due date, or may choose to pay a higher amount up to the entire amount owed. The credit provider charges interest on the amount owed (typically at a much higher rate than most other forms of debt). Some financial institutions can arrange for automatic payments to be deducted from the user's bank accounts, thus avoiding late payment altogether as long as the cardholder has sufficient funds.Credit card issuers usually waive interest charges if the balance is paid in full each month, but typically will charge full interest on the entire outstanding balance from the date of each purchase if the total balance is not paid.
For example, if a user had a $1,000 transaction and repaid it in full within this grace period, there would be no interest charged. If, however, even $1.00 of the total amount remained unpaid, interest would be charged on the $1,000 from the date of purchase until the payment is received. The precise manner in which interest is charged is usually detailed in a cardholder agreement which may be summarized on the back of the monthly statement. The general calculation formula most financial institutions use to determine the amount of interest to be charged is APR/100 x ADB/365 x number of days revolved. Take the Annual percentage rate (APR) and divide by 100 then multiply to the amount of the average daily balance (ADB) divided by 365 and then take this total and multiply by the total number of days the amount revolved before payment was made on the account. Financial institutions refer to interest charged back to the original time of the transaction and up to the time a payment was made, if not in full, as RRFC or residual retail finance charge. Thus after an amount has revolved and a payment has been made, the user of the card will still receive interest charges on his statement after paying the next statement in full (in fact the statement may only have a charge for interest that collected up until the date the full balance was paid...i.e. when the balance stopped revolving).
The credit card may simply serve as a form of revolving credit, or it may become a complicated financial instrument with multiple balance segments each at a different interest rate, possibly with a single umbrella credit limit, or with separate credit limits applicable to the various balance segments. Usually this compartmentalization is the result of special incentive offers from the issuing bank, either to encourage balance transfers from cards of other issuers. In the event that several interest rates apply to various balance segments, payment allocation is generally at the discretion of the issuing bank, and payments will therefore usually be allocated towards the lowest rate balances until paid in full before any money is paid towards higher rate balances. Interest rates can vary considerably from card to card, and the interest rate on a particular card may jump dramatically if the card user is late with a payment on that card or any other credit instrument, or even if the issuing bank decides to raise its revenue.Because of intense competition in the credit card industry, credit card providers often offer incentives such as frequent flyer points, gift certificates, or cash back (typically up to 1 percent based on total purchases) to try to attract customers to their programs.
Low interest credit cards or even 0% interest credit cards are available. The only downside to consumers is that the period of low interest credit cards is limited to a fixed term, usually between 6 and 12 months after which a higher rate is charged. However, services are available which alert credit card holders when their low interest period is due to expire. Most such services charge a monthly or annual fee.A credit card's grace period is the time the customer has to pay the balance before interest is charged to the balance. Grace periods vary, but usually range from 20 to 30 days depending on the type of credit card and the issuing bank. Some policies allow for reinstatement after certain conditions are met.
Usually, if a customer is late paying the balance, finance charges will be calculated and the grace period does not apply. Finance charges incurred depend on the grace period and balance; with most credit cards there is no grace period if there is any outstanding balance from the previous billing cycle or statement (i.e. interest is applied on both the previous balance and new transactions). However, there are some credit cards that will only apply finance charge on the previous or old balance, excluding new transactions.For merchants, a credit card transaction is often more secure than other forms of payment, such as checks, because the issuing bank commits to pay the merchant the moment the transaction is authorized, regardless of whether the consumer defaults on his credit card payment (except for legitimate disputes, which are discussed below, and can result in charge backs to the merchant). In most cases, cards are even more secure than cash, because they discourage theft by the merchant's employees and reduce the amount of cash on the premises.
For each purchase, the bank charges the merchant a commission (discount fee) for this service and there may be a certain delay before the agreed payment is received by the merchant. The commission is often a percentage of the transaction amount, plus a fixed fee. In addition, a merchant may be penalized or have his ability to receive payment using that credit card restricted if there are too many cancellations or reversals of charges as a result of disputes. Some small merchants require credit purchases to have a minimum amount (usually between $5 and $10) to compensate for the transaction costs, though this is not always allowed by the credit card consortium.
In some countries, like the Nordic countries, banks guarantee payment on stolen cards only if an ID card is checked and the ID card number/civic registration number is written down on the receipt together with the signature. In these countries merchants therefore usually ask for ID. Non-Nordic citizens, who are unlikely to possess a Nordic ID card or driving license, will instead have to show their passport, and the passport number will be written down on the receipt, sometimes together with other information. Some shops use the card's PIN code for identification, and in that case showing an ID card is not necessary.A secured credit card is a type of credit card secured by a deposit account owned by the cardholder. Typically, the cardholder must deposit between 100% and 200% of the total amount of credit desired. Thus if the cardholder puts down $1000, he or she will be given credit in the range of $500–$1000. In some cases, credit card issuers will offer incentives even on their secured card portfolios. In these cases, the deposit required may be significantly less than the required credit limit, and can be as low as 10% of the desired credit limit. This deposit is held in a special savings account. Credit card issuers offer this as they have noticed that delinquencies were notably reduced when the customer perceives he has something to lose if he doesn't repay his balance.
The cardholder of a secured credit card is still expected to make regular payments, as he or she would with a regular credit card, but should he or she default on a payment, the card issuer has the option of recovering the cost of the purchases paid to the merchants out of the deposit. The advantage of the secured card for an individual with negative or no credit history is that most companies report regularly to the major credit bureaus. This allows for building of positive credit history.
Although the deposit is in the hands of the credit card issuer as security in the event of default by the consumer, the deposit will not be debited simply for missing one or two payments. Usually the deposit is only used as an offset when the account is closed, either at the request of the customer or due to severe delinquency (150 to 180 days). This means that an account which is less than 150 days delinquent will continue to accrue interest and fees, and could result in a balance which is much higher than the actual credit limit on the card. In these cases the total debt may far exceed the original deposit and the cardholder not only forfeits their deposit but is left with an additional debt.
Most of these conditions are usually described in a cardholder agreement which the cardholder signs when their account is opened.
Secured credit cards are an option to allow a person with a poor credit history or no credit history to have a credit card which might not otherwise be available. They are often offered as a means of rebuilding one's credit. Secured credit cards are available with both Visa and MasterCard logos on them. Fees and service charges for secured credit cards often exceed those charged for ordinary non-secured credit cards, however, for people in certain situations, (for example, after charging off on other credit cards, or people with a long history of delinquency on various forms of debt), secured cards can often be less expensive in total cost than unsecured credit cards, even including the security deposit.
Thursday, April 24, 2008
ATM machine
An automated teller machine (ATM) is a computerized telecommunications device that provides the customers of a financial institution with access to financial transactions in a public space without the need for a human clerk or bank teller. On most modern ATMs, the customer is identified by inserting a plastic ATM card with a magnetic stripe or a plastic smartcard with a chip, that contains a unique card number and some security information, such as an expiration date or CVC (CVV). Security is provided by the customer entering a personal identification number (PIN).
Using an ATM, customers can access their bank accounts in order to make cash withdrawals (or credit card cash advances) and check their account balances. ATMs are known by various casual terms including automated banking machine, money machine, bank machine, cash machine, hole-in-the-wall, cashpoint or Bancomat (in
Europe and Russia).
Using an ATM, customers can access their bank accounts in order to make cash withdrawals (or credit card cash advances) and check their account balances. ATMs are known by various casual terms including automated banking machine, money machine, bank machine, cash machine, hole-in-the-wall, cashpoint or Bancomat (in
Europe and Russia).A mechanical cash dispenser was developed and built by Luther George Simjian and installed in 1939 in New York City by the City Bank of New York, but removed after 6 months due to the lack of customer acceptance.
The ATM got smaller, faster and easier over the years. Thereafter, the history of ATMs paused for over 25 years, until De La Rue developed the first electronic ATM, which was installed first in Enfield Town in North London, United Kingdomon 27 June 1967 by Barclays Bank. This instance of the invention is credited to John Shepherd-Barron, although various other engineers were awarded patents for related technologies at the time.Shepherd-Barron was awarded an OBE in the 2005 New Year's Honours List.The first person to use the machine was the British variety artist and actor Reg Varney.The first ATMs accepted only a single-use token or voucher, which was retained by the machine. These worked on various principles including radiation and low-coercivity magnetism that was wiped by the card reader to make fraud more difficult.The machine dispensed pre-packaged envelopes containing ten pounds sterling. The idea of a PIN stored on the card was developed by the British engineer James Goodfellow in 1965.
However, the modern, networked ATM was invented in Dallas, Texas, by Don Wetzel in 1968. Wetzel was a department head at an automated baggage-handling company called Docutel. In 1995 the Smithsonian's National Museum of American History recognized Docutel and Wetzel as the inventors of the ATM.[citation needed]
ATMs first came into wide UK use in 1973; the IBM 2984 was designed at the request of Lloyds Bank. The 2984 CIT (Cash Issuing Terminal) was the first true Cashpoint, similar in function to today's machines; Cashpoint is still a registered trademark of Lloyds TSB in the U.K. All were online and issued a variable amount which was immediately deducted from the account. A small number of 2984s were supplied to a USA bank. Notable historical models of ATMs include the IBM 3624 and 473x series, Diebold 10xx and TABS 9000 series, and NCR 5xxx series.
The ATM got smaller, faster and easier over the years. Thereafter, the history of ATMs paused for over 25 years, until De La Rue developed the first electronic ATM, which was installed first in Enfield Town in North London, United Kingdomon 27 June 1967 by Barclays Bank. This instance of the invention is credited to John Shepherd-Barron, although various other engineers were awarded patents for related technologies at the time.Shepherd-Barron was awarded an OBE in the 2005 New Year's Honours List.The first person to use the machine was the British variety artist and actor Reg Varney.The first ATMs accepted only a single-use token or voucher, which was retained by the machine. These worked on various principles including radiation and low-coercivity magnetism that was wiped by the card reader to make fraud more difficult.The machine dispensed pre-packaged envelopes containing ten pounds sterling. The idea of a PIN stored on the card was developed by the British engineer James Goodfellow in 1965.
However, the modern, networked ATM was invented in Dallas, Texas, by Don Wetzel in 1968. Wetzel was a department head at an automated baggage-handling company called Docutel. In 1995 the Smithsonian's National Museum of American History recognized Docutel and Wetzel as the inventors of the ATM.[citation needed]
ATMs first came into wide UK use in 1973; the IBM 2984 was designed at the request of Lloyds Bank. The 2984 CIT (Cash Issuing Terminal) was the first true Cashpoint, similar in function to today's machines; Cashpoint is still a registered trademark of Lloyds TSB in the U.K. All were online and issued a variable amount which was immediately deducted from the account. A small number of 2984s were supplied to a USA bank. Notable historical models of ATMs include the IBM 3624 and 473x series, Diebold 10xx and TABS 9000 series, and NCR 5xxx series.
ATMs are placed not only near or inside the premises of banks, but also in locations such as shopping centers/malls, airports, grocery stores, petrol/gas stations, restaurants, or any place large numbers of people may gather. These represent two types of ATM installations: on and off premise. On premise ATMs are typically more advanced, multi-function machines that complement an actual bank branch's capabilities and thus more expensive. Off premise machines are deployed by financial institutions and also ISOs (or Independent Sales Organizations) where there is usually just a straight need for cash, so they typically are the cheaper mono-function devices. In Canada, when an ATM is not operated by a financial institution it is known as a "White Label ATm".
In North America, banks often have drive-through lanes providing access to ATMs.
Many ATMs have a sign above them indicating the name of the bank or organization owning the ATM, and possibly including the list of ATM networks to which that machine is connected. This type of sign is called a topper.
In North America, banks often have drive-through lanes providing access to ATMs.
Many ATMs have a sign above them indicating the name of the bank or organization owning the ATM, and possibly including the list of ATM networks to which that machine is connected. This type of sign is called a topper.
Most ATMs are connected to interbank networks, enabling people to withdraw and deposit money from machines not belonging to the bank where they have their account or in the country where their accounts are held (enabling cash withdrawals in local currency). Some examples of interbank networks include PLUS, Cirrus, Interac and LINK.
ATMs rely on authorization of a financial transaction by the card issuer or other authorizing institution via the communications network. This is often performed through an ISO 8583 messaging system.
Many banks charge ATM usage fees. In some cases, these fees are charged solely to users who are not customers of the bank where the ATM is installed; in other cases, they apply to all users. Many people oppose these fees because ATMs are actually less costly for banks than withdrawals from human tellers.[citation needed]
In order to allow a more diverse range of devices to attach to their networks, some interbank networks have passed rules expanding the definition of an ATM to be a terminal that either has the vault within its footprint or utilizes the vault or cash drawer within the merchant establishment, which allows for the use of a scrip cash dispenser.ATMs typically connect directly to their ATM Transaction Processor via either a dial-up modem over a telephone line or directly via a leased line. Leased lines are preferable to POTS lines because they require less time to establish a connection. Leased lines may be comparatively expensive to operate versus a POTS line, meaning less-trafficked machines will usually rely on a dial-up modem. That dilemma may be solved as high-speed Internet VPN connections become more ubiquitous. Common lower-level layer communication protocols used by ATMs to communicate back to the Bank include SNA over SDLC, TC500 over Async, X.25, and TCP/IP over Ethernet.
In addition to methods employed for transaction security and secrecy, all communications traffic between the ATM and the Transaction Processor may also be encrypted via methods such as SSL.There are no hard international or government-compiled numbers totaling the complete number of ATMs in use worldwide. Estimates developed by ATMIA place the number of ATMs in use at over 1.5 million as of August 2006.
For the purpose of analyzing ATM usage around the world, financial institutions generally divide the world into seven regions, due to the penetration rates, usage statistics, and features deployed. Four regions (USA, Canada, Europe, and Japan) have high numbers of ATMs per million peopleand generally slowing growth rates.Despite the large number of ATMs,there is additional demand for machines in the Asia/Pacific area as well as in Latin America.ATMs have yet to reach high numbers in the Near East/Africa.
The world's most northerly installed ATM is located at Longyearbyen, Svalbard, Norway.
The world's most southerly installed ATM is located at McMurdo Station, Antarctica.
While ATMs are ubiquitous on modern cruise ships, ATMs can also be found on some US Navy ships.
In the United Kingdom, an ATM may be colloqually referred to as a "Cashpoint", named after the Lloyds Bank ATM brand, or hole-in-the-wall.Security, as it relates to ATMs, has several dimensions. ATMs also provide a practical demonstration of a number of security systems and concepts operating together and how various security concerns are dealt with.Early ATM security focused on making the ATMs invulnerable to physical attack; they were effectively safes with dispenser mechanisms. A number of attacks on ATMs resulted, with thieves attempting to steal entire ATMs by ram-raiding.Since late 1990s, criminal groups operating in Japan improved ram-raiding by stealing and using a truck loaded with a heavy construction machinery to effectively demolish or uproot an entire ATM and any housing to steal its cash.Another attack method is to seal all openings of the ATM with silicone and fill the vault with a combustible gas or to place an explosive inside, attached, or near the ATM. This gas or explosive is ignited and the vault is opened or distorted by the force of the resulting explosion and the criminals can break in.
Modern ATM physical security, per other modern money-handling security, concentrates on denying the use of the money inside the machine to a thief, by means of techniques such as dye markers and smoke canisters.
Transactional secrecy and integrity
The security of ATM transactions relies mostly on the integrity of the secure cryptoprocessor: the ATM often uses commodity components that are not considered to be "trusted systems".
Encryption of personal information, required by law in many jurisdictions, is used to prevent fraud. Sensitive data in ATM transactions are usually encrypted with DES, but transaction processors now usually require the use of Triple DES.Remote Key Loading techniques may be used to ensure the secrecy of the initialization of the encryption keys in the ATM. Message Authentication Code (MAC) or Partial MAC may also be used to ensure messages have not been tampered with while in transit between the ATM and the financial network.
ATMs rely on authorization of a financial transaction by the card issuer or other authorizing institution via the communications network. This is often performed through an ISO 8583 messaging system.
Many banks charge ATM usage fees. In some cases, these fees are charged solely to users who are not customers of the bank where the ATM is installed; in other cases, they apply to all users. Many people oppose these fees because ATMs are actually less costly for banks than withdrawals from human tellers.[citation needed]
In order to allow a more diverse range of devices to attach to their networks, some interbank networks have passed rules expanding the definition of an ATM to be a terminal that either has the vault within its footprint or utilizes the vault or cash drawer within the merchant establishment, which allows for the use of a scrip cash dispenser.ATMs typically connect directly to their ATM Transaction Processor via either a dial-up modem over a telephone line or directly via a leased line. Leased lines are preferable to POTS lines because they require less time to establish a connection. Leased lines may be comparatively expensive to operate versus a POTS line, meaning less-trafficked machines will usually rely on a dial-up modem. That dilemma may be solved as high-speed Internet VPN connections become more ubiquitous. Common lower-level layer communication protocols used by ATMs to communicate back to the Bank include SNA over SDLC, TC500 over Async, X.25, and TCP/IP over Ethernet.
In addition to methods employed for transaction security and secrecy, all communications traffic between the ATM and the Transaction Processor may also be encrypted via methods such as SSL.There are no hard international or government-compiled numbers totaling the complete number of ATMs in use worldwide. Estimates developed by ATMIA place the number of ATMs in use at over 1.5 million as of August 2006.
For the purpose of analyzing ATM usage around the world, financial institutions generally divide the world into seven regions, due to the penetration rates, usage statistics, and features deployed. Four regions (USA, Canada, Europe, and Japan) have high numbers of ATMs per million peopleand generally slowing growth rates.Despite the large number of ATMs,there is additional demand for machines in the Asia/Pacific area as well as in Latin America.ATMs have yet to reach high numbers in the Near East/Africa.
The world's most northerly installed ATM is located at Longyearbyen, Svalbard, Norway.
The world's most southerly installed ATM is located at McMurdo Station, Antarctica.
While ATMs are ubiquitous on modern cruise ships, ATMs can also be found on some US Navy ships.
In the United Kingdom, an ATM may be colloqually referred to as a "Cashpoint", named after the Lloyds Bank ATM brand, or hole-in-the-wall.Security, as it relates to ATMs, has several dimensions. ATMs also provide a practical demonstration of a number of security systems and concepts operating together and how various security concerns are dealt with.Early ATM security focused on making the ATMs invulnerable to physical attack; they were effectively safes with dispenser mechanisms. A number of attacks on ATMs resulted, with thieves attempting to steal entire ATMs by ram-raiding.Since late 1990s, criminal groups operating in Japan improved ram-raiding by stealing and using a truck loaded with a heavy construction machinery to effectively demolish or uproot an entire ATM and any housing to steal its cash.Another attack method is to seal all openings of the ATM with silicone and fill the vault with a combustible gas or to place an explosive inside, attached, or near the ATM. This gas or explosive is ignited and the vault is opened or distorted by the force of the resulting explosion and the criminals can break in.
Modern ATM physical security, per other modern money-handling security, concentrates on denying the use of the money inside the machine to a thief, by means of techniques such as dye markers and smoke canisters.
Transactional secrecy and integrity
The security of ATM transactions relies mostly on the integrity of the secure cryptoprocessor: the ATM often uses commodity components that are not considered to be "trusted systems".
Encryption of personal information, required by law in many jurisdictions, is used to prevent fraud. Sensitive data in ATM transactions are usually encrypted with DES, but transaction processors now usually require the use of Triple DES.Remote Key Loading techniques may be used to ensure the secrecy of the initialization of the encryption keys in the ATM. Message Authentication Code (MAC) or Partial MAC may also be used to ensure messages have not been tampered with while in transit between the ATM and the financial network.
Monday, April 21, 2008
Avometer & magger
The Avometer was a British brand multimeter (USA), still in production today in the form of the Model 8 Mk 7 by Megger. It is often called simply an AVO and derives its name from the first letter of the words amperes, volts, ohms. It was by far the best instrument of its kind in the UK from the 1930s to at least the 1960s. Almost uniquely for a radio repairman's multimeter it measures alternating current up to 10 A as well as the standard AC and DC voltages up to 1000 V; as an ohmeter it measures from 0.1 Ω up to 200 kΩ in three ranges. The instrument had an accuracy of ±1% of FSD on DC ranges and ±2% on AC ranges. Its maximum current consumption was 50 μA (corresponding to 20,000 ohms per volt), which was sufficient (in most circuits) to reduce the voltage measurement error, caused by connection of the meter, to an acceptable level. A pair of rotary switches are used to select the range to be measured, being arranged in such a way as to minimise the risk of damage to the instrument should the wrong range be selected. Further protection is provided by an overload cut-out. It was a superb example of British radio engineering in its heyday and was found in virtually every radio repair workshop throughout the country and can still be found in regular use.A megger (or sometimes meggar) is often used as an alternate term for an insulation tester - a circuit tester which puts a very high voltage at a very low current across two conductors to make sure that they are properly insulated. The word is short for megohm-meter.
It is in fact the registered trade mark of Megger Group Ltd who have manufactured insulation testers since 1889.
Older types of insulation testers have a small built-in generator turned by the handle. Modern types work with batteries and circuitry to generate the voltage required, typically 500V DC.
It is in fact the registered trade mark of Megger Group Ltd who have manufactured insulation testers since 1889.
Older types of insulation testers have a small built-in generator turned by the handle. Modern types work with batteries and circuitry to generate the voltage required, typically 500V DC.
Wednesday, April 2, 2008
Electromechanics
Electromechanical devices are those that combine electrical and mechanical parts. These include electric motors, loudspeakers, some fire alarms and mechanical devices powered by them, such as calculators and adding machines; switches, solenoids, relays, crossbar switches and stepping switches.Early on, "repeaters" originated with telegraphy and were electromechanical devices used to regenerate telegraph signals. The telephony crossbar switch is an electromechanical device for switching telephone calls. They were first widely installed in the 1950s in both the United States and England, and from there quickly spread to the rest of the world. They replaced most earlier designs like the Strowger switch in larger installations. Nikola Tesla, one of the great engineers, pioneered the field of electromechanics.
Paul Nipkow proposed and patented the first electromechanical television system in 1885. Electrical typewriters developed, up to the 1980s, as "power-assisted typewriters." They contained a single electrical component in them, the motor. Where the keystroke had previously moved a typebar directly, now it engaged mechanical linkages that directed mechanical power from the motor into the typebar. This was also true of the forthcoming IBM Selectric. At Bell Labs, in the 1940s, the Bell Model V computer was developed. It was an electromechanical relay-based monster with cycle times in seconds. In 1968 Garrett Systems were invited to produce a digital computer to compete with electromechanical systems then under development for the main flight control computer in the US Navy's new F-14 Tomcat fighter.
Today, though, common items which would have used electromechanical devices for control, today use, less expensive and more effectively, a standard integrated circuit (containing a few million transistors) and write a computer program to carry out the same task through logic. Transistors have replaced almost all electromechanical devices, are used in most simple feedback control systems, and appear in huge numbers in everything from traffic lights to washing machines.
Paul Nipkow proposed and patented the first electromechanical television system in 1885. Electrical typewriters developed, up to the 1980s, as "power-assisted typewriters." They contained a single electrical component in them, the motor. Where the keystroke had previously moved a typebar directly, now it engaged mechanical linkages that directed mechanical power from the motor into the typebar. This was also true of the forthcoming IBM Selectric. At Bell Labs, in the 1940s, the Bell Model V computer was developed. It was an electromechanical relay-based monster with cycle times in seconds. In 1968 Garrett Systems were invited to produce a digital computer to compete with electromechanical systems then under development for the main flight control computer in the US Navy's new F-14 Tomcat fighter.
Today, though, common items which would have used electromechanical devices for control, today use, less expensive and more effectively, a standard integrated circuit (containing a few million transistors) and write a computer program to carry out the same task through logic. Transistors have replaced almost all electromechanical devices, are used in most simple feedback control systems, and appear in huge numbers in everything from traffic lights to washing machines.
Thursday, March 20, 2008
Marble
Marble is a nonfoliated metamorphic rock resulting from the metamorphism of limestone, composed mostly of calcite (a crystalline form of calcium carbonate, CaCO3). It is extensively used for sculpture, as a building material, and in many other applications. The word "marble" is colloquially used to refer to many other stones that are capable of taking a high polish.
Faux marble or faux marbling is a wall painting technique that imitates the color patterns of real marble (not to be confused with paper marbling). Marble dust can be combined with cement or synthetic resins to make reconstituted or cultured marble.
Places named after the stone include Marble Arch, London; the Sea of Marmara; India's Marble Rocks; and the towns of Marble, Minnesota; Marble, Colorado; and Marble Hill, Manhattan, New York. The Elgin Marbles are marble sculptures from the Parthenon that are on display in the British Museum. They were brought to Britain by the Earl of Elgin.
Marble is a metamorphic rock resulting from regional or rarely contact metamorphism of sedimentary carbonate rocks, either limestone or dolostone, or metamorphism of older marble. This metamorphic process causes a complete recrystallization of the original rock into an interlocking mosaic of calcite, aragonite and/or dolomite crystals. The temperatures and pressures necessary to form marble usually destroy any fossils and sedimentary textures present in the original rock.
Pure white marble is the result of metamorphism of very pure limestones. The characteristic swirls and veins of many colored marble varieties are usually due to various mineral impurities such as clay, silt, sand, iron oxides, or chert which were originally present as grains or layers in the limestone. Green coloration is often due to serpentine resulting from originally high magnesium limestone or dolostone with silica impurities. These various impurities have been mobilized and recrystallized by the intense pressure and heat of the metamorphism.
In the construction, specifically the dimension stone trade, the term "marble" is used for any crystalline calcitic rock (and some non-calcitic rocks) useful as building stone. For example, "Tennessee marble" is really a highly fossiliferous gray to pink to maroon Ordovician dolostone that geologists call the Holston Formation.
Faux marble or faux marbling is a wall painting technique that imitates the color patterns of real marble (not to be confused with paper marbling). Marble dust can be combined with cement or synthetic resins to make reconstituted or cultured marble.
Places named after the stone include Marble Arch, London; the Sea of Marmara; India's Marble Rocks; and the towns of Marble, Minnesota; Marble, Colorado; and Marble Hill, Manhattan, New York. The Elgin Marbles are marble sculptures from the Parthenon that are on display in the British Museum. They were brought to Britain by the Earl of Elgin.
Marble is a metamorphic rock resulting from regional or rarely contact metamorphism of sedimentary carbonate rocks, either limestone or dolostone, or metamorphism of older marble. This metamorphic process causes a complete recrystallization of the original rock into an interlocking mosaic of calcite, aragonite and/or dolomite crystals. The temperatures and pressures necessary to form marble usually destroy any fossils and sedimentary textures present in the original rock.
Pure white marble is the result of metamorphism of very pure limestones. The characteristic swirls and veins of many colored marble varieties are usually due to various mineral impurities such as clay, silt, sand, iron oxides, or chert which were originally present as grains or layers in the limestone. Green coloration is often due to serpentine resulting from originally high magnesium limestone or dolostone with silica impurities. These various impurities have been mobilized and recrystallized by the intense pressure and heat of the metamorphism.
In the construction, specifically the dimension stone trade, the term "marble" is used for any crystalline calcitic rock (and some non-calcitic rocks) useful as building stone. For example, "Tennessee marble" is really a highly fossiliferous gray to pink to maroon Ordovician dolostone that geologists call the Holston Formation.
Thursday, March 6, 2008
Motorcycle
A motorcycle or motorbike is a single-track, two-wheeled motor vehicle powered by an engine. Styles of motorcycles vary depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions. In many parts of the world, motorcycles are among the least expensive and most widespread forms of motorised transport.
History
The inspiration for arguably the first motorcycle was designed and built by the German inventors Gottlieb Daimler and Wilhelm Maybach in Bad Cannstatt (since 1905 a city district of Stuttgart) in 1885.The first petroleum-powered vehicle, it was essentially a motorised bicycle, although the inventors called their invention the Reitwagen ("riding car"). However, if one counts two wheels with steam propulsion as being a motorcycle, then the first one may have been American. One such machine was demonstrated at fairs and circuses in the eastern U.S. in 1867, built by Sylvester Howard Roper of Roxbury, Massachusetts.
In 1894, Hildebrand & Wolfmüller became the first motorcycle available for purchase. In the early period of motorcycle history, many producers of bicycles adapted their designs to accommodate the new internal combustion engine. As the engines became more powerful, and designs outgrew the bicycle origins, the number of motorcycle producers increased.Until the First World War, the largest motorcycle manufacturer in the world was Indian, producing over 20,000 bikes per year. By 1920, this honour went to Harley-Davidson, with their motorcycles being sold by dealers in 67 countries, until 1928 when DKW took over as the largest manufacturer.
After the Second World War, the BSA Group became the largest producer of motorcycles in the world, producing up to 75,000 bikes a year in the 1950s. The German company NSU Motorenwerke AG held the position of largest manufacturer from 1955 until the 1970s.
From the 1960s through the 1990s, small two-stroke motorcycles were popular worldwide, partly as a result of East German Walter Kaaden's engine work in the 1950s.Today, the Japanese manufacturers, Honda, Kawasaki, Suzuki, and Yamaha dominate the motorcycle industry, although Harley-Davidson still maintains a high degree of popularity in the United States. Recent years have also seen a resurgence in the popularity of several other brands sold in the U.S. market, including BMW, KTM, Triumph, Aprilia, Moto Guzzi and Ducati.
Outside of the USA, these brands have enjoyed continued and sustained success, although Triumph, for example, has been re-incarnated from its former self into a modern world-class manufacturer. In overall numbers, however, the Chinese currently manufacture and sell more motorcycles than any other country and exports are rising. The quality of these machines is asserted to be somewhat lower than their Japanese, European and American counterparts[citation needed].
Additionally, the small-capacity scooter is very popular through most of the world. The Piaggio group of Italy, for example, is one of the world's largest producers of two-wheeled vehicles. The scooter culture has, as yet, not been adopted widely in North America.
Social aspects,Subcultures
Around the world, motorcycles have historically been associated with subcultures. Some of these subcultures have been loose-knit social groups such as the cafe racers of 1950s Britain, and the Mods and Rockers of the 1960s. A few are believed to be criminal gangs.
Social motorcyclist organisations are popular and are sometimes organised geographically, focus on individual makes, or even specific models. Example motorcycle clubs include: American Motorcyclist Association, Harley Owners Group, Moto Guzzi National Owners Club, Gold Wing Road Riders (GWRRA), and BMW MOA.
Many motorcycle organisations raise money for charities through organised events and rides. Some organisations hold large international motorcycle rallies in different parts of the world that are attended by many thousands of riders.
Some other motorcycle organisations exist only for the direct benefit of others. Bikers Against Child Abuse (BACA) is one example. BACA assigns members to individual children to help them through difficult situations, or even stay with the child if the child is alone or frightened.In recent decades, motorcyclists have formed political lobbying organisations in order to influence legislators to introduce motorcycle-friendly legislation. One of the oldest such organisations, the British Motorcycle Action Group, was founded in 1973 specifically in response to helmet compulsion, introduced without public consultation.In addition, the British Motorcyclists Federation (BMF), originally founded in 1960 as a reaction to the public perception of motorcyclists as leather-jacketed hooligans, has itself moved into political lobbying.
Likewise, the U.S. has ABATE, which, like most such organisations, also works to improve motorcycle safety, as well as running the usual charity fund-raising events and rallies, often for motorcycle-related political interests. Some other lobbying organisations are listed in Category:Motorcyclists organizations.
Mobility
While the reasons for people choosing to ride motorcycles are many and varied, those reasons are increasingly practical, with riders opting for a powered two-wheeler as a cost-efficient alternative to infrequent and expensive public transport systems, or as a means of avoiding or reducing the effects of urban congestion.In places where it is permitted, lane splitting, also known as filtering, allows motorcycles to use the space between vehicles to move through stationary or slow traffic.
In the UK, motorcycles are exempt from the £8 per day London congestion charge other vehicles must pay to enter the city during the day. Motorcycles are also exempt from toll charges at some river crossings, such as the Severn Bridge, Dartford Crossing, and Mersey Tunnels. Some cities, such as Bristol, allow motorcycles to use bus lanes and provide dedicated free parking. In the United States, those states that have high-occupancy vehicle lanes also allow for motorcycle travel in them. Other countries have similar policies.
In many cultures motorcycles are the primary means of motorised transport. According to the Taiwanese government, for example, "the number of automobiles per ten thousand population is around 2,500, and the number of motorcycles is about 5,000."
Safety
Motorcycles have a higher rate of fatal accidents than automobiles. United States Department of Transportation data for 2005 from the Fatality Analysis Reporting System show that for passenger cars, 18.62 fatal crashes occur per 100,000 registered vehicles. For motorcycles this figure is higher at 75.19 per 100,000 registered vehicles – four times higher than for cars.The same data show that 1.56 fatalities occur per 100 million vehicle miles travelled for passenger cars, whereas for motorcycles the figure is 43.47 – 28 times higher than for cars. Furthermore for motorcycles the accident rates have increased significantly since the end of the 1990s, while the rates have dropped for passenger cars.
The two major causes of motorcycle accidents in the United States are: motorists pulling out or turning in front of motorcyclists and violating their rights-of-way and motorcyclists running wide through turns. The former is sometimes called a SMIDSY, an acronym formed from the motorists' common response of "Sorry mate, I didn't see you". The latter is more common when motorcyclists mix drinking with riding.Motorcyclists can anticipate avoid these crashes with proper training, increasing their conspicuousness to other traffic, and separating alcohol and riding.The United Kingdom has a number of organisations which are dedicated to improving motorcycle safety by providing advanced rider training over and above what is necessary to pass the basic motorcycle test. These include the Institute of Advanced Motorists (IAM) and the Royal Society for the Prevention of Accidents (RoSPA). Along with increased personal safety, riders with these advanced qualifications often benefit from reduced insurance costs.
Motorcycle Safety Education is offered throughout the United States by a number of organisations ranging from state agencies to non-profit organisations to corporations. The courses, designed by the Motorcycle Safety Foundation (MSF), include a Basic Rider Course, an Intermediate Rider Course and an Advanced Rider Course.
In the UK and some Australian jurisdictions, such as New South Wales, the Australian Capital Territory and the Northern Territory, it is compulsory to undertake a rider training course before being issued a Learners Licence.
In Canada, motorcycle rider training is compulsory in Quebec and Manitoba only, but all provinces and territories have Graduated Licensing programs which place restrictions on new drivers until they have gained experience. Eligibility for a full motorcycle license or endorsement for completing a Motorcycle Safety course varies from province to province. The Canada Safety Council (CSC), a non-profit safety organisation, offers the Gearing Up program across Canada and is endorsed by the Motorcycle and Moped Industry Council.Training course graduates may qualify for reduced insurance premiums.
History
The inspiration for arguably the first motorcycle was designed and built by the German inventors Gottlieb Daimler and Wilhelm Maybach in Bad Cannstatt (since 1905 a city district of Stuttgart) in 1885.The first petroleum-powered vehicle, it was essentially a motorised bicycle, although the inventors called their invention the Reitwagen ("riding car"). However, if one counts two wheels with steam propulsion as being a motorcycle, then the first one may have been American. One such machine was demonstrated at fairs and circuses in the eastern U.S. in 1867, built by Sylvester Howard Roper of Roxbury, Massachusetts.
In 1894, Hildebrand & Wolfmüller became the first motorcycle available for purchase. In the early period of motorcycle history, many producers of bicycles adapted their designs to accommodate the new internal combustion engine. As the engines became more powerful, and designs outgrew the bicycle origins, the number of motorcycle producers increased.Until the First World War, the largest motorcycle manufacturer in the world was Indian, producing over 20,000 bikes per year. By 1920, this honour went to Harley-Davidson, with their motorcycles being sold by dealers in 67 countries, until 1928 when DKW took over as the largest manufacturer.
After the Second World War, the BSA Group became the largest producer of motorcycles in the world, producing up to 75,000 bikes a year in the 1950s. The German company NSU Motorenwerke AG held the position of largest manufacturer from 1955 until the 1970s.
From the 1960s through the 1990s, small two-stroke motorcycles were popular worldwide, partly as a result of East German Walter Kaaden's engine work in the 1950s.Today, the Japanese manufacturers, Honda, Kawasaki, Suzuki, and Yamaha dominate the motorcycle industry, although Harley-Davidson still maintains a high degree of popularity in the United States. Recent years have also seen a resurgence in the popularity of several other brands sold in the U.S. market, including BMW, KTM, Triumph, Aprilia, Moto Guzzi and Ducati.
Outside of the USA, these brands have enjoyed continued and sustained success, although Triumph, for example, has been re-incarnated from its former self into a modern world-class manufacturer. In overall numbers, however, the Chinese currently manufacture and sell more motorcycles than any other country and exports are rising. The quality of these machines is asserted to be somewhat lower than their Japanese, European and American counterparts[citation needed].
Additionally, the small-capacity scooter is very popular through most of the world. The Piaggio group of Italy, for example, is one of the world's largest producers of two-wheeled vehicles. The scooter culture has, as yet, not been adopted widely in North America.
Social aspects,Subcultures
Around the world, motorcycles have historically been associated with subcultures. Some of these subcultures have been loose-knit social groups such as the cafe racers of 1950s Britain, and the Mods and Rockers of the 1960s. A few are believed to be criminal gangs.
Social motorcyclist organisations are popular and are sometimes organised geographically, focus on individual makes, or even specific models. Example motorcycle clubs include: American Motorcyclist Association, Harley Owners Group, Moto Guzzi National Owners Club, Gold Wing Road Riders (GWRRA), and BMW MOA.
Many motorcycle organisations raise money for charities through organised events and rides. Some organisations hold large international motorcycle rallies in different parts of the world that are attended by many thousands of riders.
Some other motorcycle organisations exist only for the direct benefit of others. Bikers Against Child Abuse (BACA) is one example. BACA assigns members to individual children to help them through difficult situations, or even stay with the child if the child is alone or frightened.In recent decades, motorcyclists have formed political lobbying organisations in order to influence legislators to introduce motorcycle-friendly legislation. One of the oldest such organisations, the British Motorcycle Action Group, was founded in 1973 specifically in response to helmet compulsion, introduced without public consultation.In addition, the British Motorcyclists Federation (BMF), originally founded in 1960 as a reaction to the public perception of motorcyclists as leather-jacketed hooligans, has itself moved into political lobbying.
Likewise, the U.S. has ABATE, which, like most such organisations, also works to improve motorcycle safety, as well as running the usual charity fund-raising events and rallies, often for motorcycle-related political interests. Some other lobbying organisations are listed in Category:Motorcyclists organizations.
Mobility
While the reasons for people choosing to ride motorcycles are many and varied, those reasons are increasingly practical, with riders opting for a powered two-wheeler as a cost-efficient alternative to infrequent and expensive public transport systems, or as a means of avoiding or reducing the effects of urban congestion.In places where it is permitted, lane splitting, also known as filtering, allows motorcycles to use the space between vehicles to move through stationary or slow traffic.
In the UK, motorcycles are exempt from the £8 per day London congestion charge other vehicles must pay to enter the city during the day. Motorcycles are also exempt from toll charges at some river crossings, such as the Severn Bridge, Dartford Crossing, and Mersey Tunnels. Some cities, such as Bristol, allow motorcycles to use bus lanes and provide dedicated free parking. In the United States, those states that have high-occupancy vehicle lanes also allow for motorcycle travel in them. Other countries have similar policies.
In many cultures motorcycles are the primary means of motorised transport. According to the Taiwanese government, for example, "the number of automobiles per ten thousand population is around 2,500, and the number of motorcycles is about 5,000."
Safety
Motorcycles have a higher rate of fatal accidents than automobiles. United States Department of Transportation data for 2005 from the Fatality Analysis Reporting System show that for passenger cars, 18.62 fatal crashes occur per 100,000 registered vehicles. For motorcycles this figure is higher at 75.19 per 100,000 registered vehicles – four times higher than for cars.The same data show that 1.56 fatalities occur per 100 million vehicle miles travelled for passenger cars, whereas for motorcycles the figure is 43.47 – 28 times higher than for cars. Furthermore for motorcycles the accident rates have increased significantly since the end of the 1990s, while the rates have dropped for passenger cars.
The two major causes of motorcycle accidents in the United States are: motorists pulling out or turning in front of motorcyclists and violating their rights-of-way and motorcyclists running wide through turns. The former is sometimes called a SMIDSY, an acronym formed from the motorists' common response of "Sorry mate, I didn't see you". The latter is more common when motorcyclists mix drinking with riding.Motorcyclists can anticipate avoid these crashes with proper training, increasing their conspicuousness to other traffic, and separating alcohol and riding.The United Kingdom has a number of organisations which are dedicated to improving motorcycle safety by providing advanced rider training over and above what is necessary to pass the basic motorcycle test. These include the Institute of Advanced Motorists (IAM) and the Royal Society for the Prevention of Accidents (RoSPA). Along with increased personal safety, riders with these advanced qualifications often benefit from reduced insurance costs.
Motorcycle Safety Education is offered throughout the United States by a number of organisations ranging from state agencies to non-profit organisations to corporations. The courses, designed by the Motorcycle Safety Foundation (MSF), include a Basic Rider Course, an Intermediate Rider Course and an Advanced Rider Course.
In the UK and some Australian jurisdictions, such as New South Wales, the Australian Capital Territory and the Northern Territory, it is compulsory to undertake a rider training course before being issued a Learners Licence.
In Canada, motorcycle rider training is compulsory in Quebec and Manitoba only, but all provinces and territories have Graduated Licensing programs which place restrictions on new drivers until they have gained experience. Eligibility for a full motorcycle license or endorsement for completing a Motorcycle Safety course varies from province to province. The Canada Safety Council (CSC), a non-profit safety organisation, offers the Gearing Up program across Canada and is endorsed by the Motorcycle and Moped Industry Council.Training course graduates may qualify for reduced insurance premiums.
Saturday, February 23, 2008
Electric vehicle
An electric vehicle, or EV, is a vehicle with one or more electric motors for propulsion. The motion may be provided either by wheels or propellers driven by rotary motors, or in the case of tracked vehicles, by linear motors.
The energy used to propel the vehicle may be obtained from several sources, some of them more ecological than others:from an on-board rechargeable energy storage system (RESS), called Full Electric Vehicles (FEV):
from chemical energy stored on the vehicle in on-board batteries: Battery electric vehicle (BEV)
from static energy stored on the vehicle in on-board supercapacitors
from rotational storage: flywheels
from a direct connection to land-based generation plants, as is common in electric trains and trolley buses (See also : overhead lines, third rail and conduit current collection)
from both an on-board rechargeable energy storage system and a direct continuous connection to land-based generation plants for purposes of on-highway recharging with unrestricted highway range.
from both an on-board rechargeable energy storage system (RESS) and a fueled propulsion power source (internal combustion engine): hybrid vehicle (as in a diesel-electric locomotive), including plug-in hybrid
from renewable sources such as wind and solar
generated on-board using a fuel cell: fuel cell vehicle
generated on-board using nuclear energy, on nuclear submarines and aircraft carriers
Electric vehicles can include electric airplanes, electric boats, and electric motorcycles and scooters.
Electric motive power started with a small railway operated by a miniature electric motor, built by Thomas Davenport in 1835. In 1838, a Scotsman named Robert Davidson built an electric locomotive that attained a speed of four miles an hour. In England a patent was granted in 1840 for the use of rails as conductors of electric current, and similar American patents were issued to Lilley and Colten in 1847.
Between 1832 and 1839 (the exact year is uncertain), Robert Anderson of Scotland invented the first crude electric carriage, powered by non-rechargeable Primary cells.
By the 20th century, electric cars and rail transport were commonplace, with commercial electric automobiles having the majority of the market. Over time their general-purpose commercial use reduced to specialist roles, as platform trucks, forklift trucks, tow tractors and urban delivery vehicles, such as the iconic British milk float.
Electrified trains were used for coal transport as the motors did not use precious oxygen in the mines. Switzerland's lack of natural fossil resources forced the rapid electrification of their rail network. One of the earliest rechargeable batteries - the Nickel-iron battery - was favored by Edison for use in electric cars.
Electric vehicles were among the earliest automobiles, and before the preeminence of light, powerful internal combustion engines, electric automobiles held many vehicle land speed and distance records in the early 1900s. They were produced by Baker Electric, Columbia Electric, Detroit Electric, and others and at one point in history out-sold gasoline-powered vehicles.
In the 1930s, National City Lines, which was a partnership of General Motors, Firestone, and Standard Oil of California purchased many electric tram networks across the country to dismantle them and replace them with GM buses. The partnership was convicted for this conspiracy, but the ruling was overturned in a higher court. Electric tram line technologies could be used to recharge BEVs and PHEVs on the highway while the user drives, providing virtually unrestricted driving range. The technology is old and well established (see : Conduit current collection, Nickel-iron battery). The infrastructure has not been built.
In January of 1990, General Motors' President introduced its EV concept two-seater, the "Impact," at the Los Angeles Auto Show. That September, the California Air Resources Board mandated major-automaker sales of EVs, in phases starting in 1998. From 1996 to 1998 GM produced 1117 EV1s, 800 of which were made available through 3-year leases.
Chrysler, Ford, GM, Honda, Nissan and Toyota also produced limited numbers of EVs for California drivers. In 2003, upon the expiration of EV1 leases, GM crushed them. The crushing has variously been attributed to 1) the auto industry's successful Federal Court challenge to California's Zero-emissions vehicle mandate, 2) a federal regulation requiring GM to produce and maintain spare parts for the few thousands EV1s and 3) the success of the Oil and Auto industries' media campaign to reduce public acceptance of electric vehicles.A movie made on the subject in 2005-2006 was titled Who Killed the Electric Car? and released theatrically by Sony Pictures Classics in 2006. The film explores the roles of automobile manufacturers, oil industry, the US government, batteries, hydrogen vehicles, and consumers, and each of their roles in limiting the deployment and adoption of this technology.
Honda, Nissan and Toyota also repossessed and crushed most of their EVs, which, like the GM EV1s, had been available only by closed-end lease. After public protests, Toyota sold 200 of its RAV EVs to eager buyers; they now sell, five years later, at over their original forty-thousand-dollar price.Chemical energy is a common independent energy source. Chemical energy is converted to electrical energy, which is then regulated and fed to the drive motors. Chemical energy is usually in the form of diesel or petrol (gasoline). The liquid fuels are usually converted into electricity by an electrical generator powered by an internal combustion engine or other heat engine. This approach is known as diesel-electric or gasoline-electric hybrid locomotion. These engines still produce greenhouse gases, though typically less than conventional petroleum vehicles, and can be combined with regenerative braking systems for more efficiency.
Nowadays batteries, supercapacitors and flywheel energy storage are on-board rechargeable energy storage system (RESS). By avoiding an intermediate mechanical step, the energy conversion efficiency is dramatically improved over the chemical-thermal-mechanical-electrical-mechanical process already discussed. This is due to the higher carnot efficiency through directly oxidizing the fuel and by avoiding several unnecessary energy conversions. Furthermore, electro-chemical batteries conversions are easy to reverse, allowing electrical energy to be stored in chemical form.
Another form of chemical to electrical conversion is fuel cells, projected for future use.
For especially large electric vehicles, such as submarines, the chemical energy of the diesel-electric can be replaced by a nuclear reactor. The nuclear reactor usually provides heat, which drives a steam turbine, which drives a generator, which is then fed to the propulsion. See Nuclear Power.
Between 1832 and 1839 (the exact year is uncertain), Robert Anderson of Scotland invented the first crude electric carriage, powered by non-rechargeable Primary cells.
By the 20th century, electric cars and rail transport were commonplace, with commercial electric automobiles having the majority of the market. Over time their general-purpose commercial use reduced to specialist roles, as platform trucks, forklift trucks, tow tractors and urban delivery vehicles, such as the iconic British milk float.
Electrified trains were used for coal transport as the motors did not use precious oxygen in the mines. Switzerland's lack of natural fossil resources forced the rapid electrification of their rail network. One of the earliest rechargeable batteries - the Nickel-iron battery - was favored by Edison for use in electric cars.
Electric vehicles were among the earliest automobiles, and before the preeminence of light, powerful internal combustion engines, electric automobiles held many vehicle land speed and distance records in the early 1900s. They were produced by Baker Electric, Columbia Electric, Detroit Electric, and others and at one point in history out-sold gasoline-powered vehicles.
In the 1930s, National City Lines, which was a partnership of General Motors, Firestone, and Standard Oil of California purchased many electric tram networks across the country to dismantle them and replace them with GM buses. The partnership was convicted for this conspiracy, but the ruling was overturned in a higher court. Electric tram line technologies could be used to recharge BEVs and PHEVs on the highway while the user drives, providing virtually unrestricted driving range. The technology is old and well established (see : Conduit current collection, Nickel-iron battery). The infrastructure has not been built.
In January of 1990, General Motors' President introduced its EV concept two-seater, the "Impact," at the Los Angeles Auto Show. That September, the California Air Resources Board mandated major-automaker sales of EVs, in phases starting in 1998. From 1996 to 1998 GM produced 1117 EV1s, 800 of which were made available through 3-year leases.
Chrysler, Ford, GM, Honda, Nissan and Toyota also produced limited numbers of EVs for California drivers. In 2003, upon the expiration of EV1 leases, GM crushed them. The crushing has variously been attributed to 1) the auto industry's successful Federal Court challenge to California's Zero-emissions vehicle mandate, 2) a federal regulation requiring GM to produce and maintain spare parts for the few thousands EV1s and 3) the success of the Oil and Auto industries' media campaign to reduce public acceptance of electric vehicles.A movie made on the subject in 2005-2006 was titled Who Killed the Electric Car? and released theatrically by Sony Pictures Classics in 2006. The film explores the roles of automobile manufacturers, oil industry, the US government, batteries, hydrogen vehicles, and consumers, and each of their roles in limiting the deployment and adoption of this technology.
Honda, Nissan and Toyota also repossessed and crushed most of their EVs, which, like the GM EV1s, had been available only by closed-end lease. After public protests, Toyota sold 200 of its RAV EVs to eager buyers; they now sell, five years later, at over their original forty-thousand-dollar price.Chemical energy is a common independent energy source. Chemical energy is converted to electrical energy, which is then regulated and fed to the drive motors. Chemical energy is usually in the form of diesel or petrol (gasoline). The liquid fuels are usually converted into electricity by an electrical generator powered by an internal combustion engine or other heat engine. This approach is known as diesel-electric or gasoline-electric hybrid locomotion. These engines still produce greenhouse gases, though typically less than conventional petroleum vehicles, and can be combined with regenerative braking systems for more efficiency.
Nowadays batteries, supercapacitors and flywheel energy storage are on-board rechargeable energy storage system (RESS). By avoiding an intermediate mechanical step, the energy conversion efficiency is dramatically improved over the chemical-thermal-mechanical-electrical-mechanical process already discussed. This is due to the higher carnot efficiency through directly oxidizing the fuel and by avoiding several unnecessary energy conversions. Furthermore, electro-chemical batteries conversions are easy to reverse, allowing electrical energy to be stored in chemical form.
Another form of chemical to electrical conversion is fuel cells, projected for future use.
For especially large electric vehicles, such as submarines, the chemical energy of the diesel-electric can be replaced by a nuclear reactor. The nuclear reactor usually provides heat, which drives a steam turbine, which drives a generator, which is then fed to the propulsion. See Nuclear Power.
Battery electric vehicle:-
The battery electric vehicle, or BEV, is a vehicle that utilizes chemical energy stored in rechargeable battery packs, and electric motors and motor controllers instead of internal combustion engines (ICEs). Some confusion arises because the industry often refers to BEVs when it means electric cars.
Vehicles using both electric motors and ICEs (hybrid electric vehicles) are examples of hybrid vehicles, and are not considered pure BEVs because they operate in a charge-sustaining mode. Hybrid vehicles with batteries that can be charged externally to displace some or all of their ICE power and gasoline fuel are called plug-in hybrid electric vehicles (PHEV), and are pure BEVs during their charge-depleting mode. BEVs include automobiles, light trucks, and neighborhood electric vehicles.
Vehicles using both electric motors and ICEs (hybrid electric vehicles) are examples of hybrid vehicles, and are not considered pure BEVs because they operate in a charge-sustaining mode. Hybrid vehicles with batteries that can be charged externally to displace some or all of their ICE power and gasoline fuel are called plug-in hybrid electric vehicles (PHEV), and are pure BEVs during their charge-depleting mode. BEVs include automobiles, light trucks, and neighborhood electric vehicles.
Sunday, January 13, 2008
The power Subaru EJ engine
The Subaru EJ engine is a series of automotive engines manufactured by Subaru, a division of Fuji Heavy Industries introduced mid 1989 for the 1st generation Legacy. The engine was designed by Masayuki Kodama, Takemasa Yamada and Shuji Sawafuji of FHI Ltd. Engines of this series are 16 valve flat-4 horizontal, with configurations available for SOHC and DOHC, natural aspiration and turbocharged.A 10-digit engine code is used by Subaru: the first 2 characters identify the engine series. The 3rd & 4th identify displacement volume in liters. The 5th digit is a sub-series identifier and fuel system flag. The 6th digit identifies emissions regulations it conforms to, while the 7th digit shows the intended transmission it was mated with. The final 3 digits are minor production change codes.
- EJ15:1.5 Litre SOHC
Usage:
Impreza (JDM only, though often seen in gray market exports to eastern Europe and Russia.) - EJ16:1.6 Litre SOHC, 90 hp @ 5600 rpm.
Usage:
Impreza 93-94 (JDM only)
Impreza 93-06 (Europe & Middle East) - EJ18:1.8 Litre SOHC 110 hp @ 5600 rpm.
Usage:
Impreza 93-96
Legacy (non-USDM) 90-96 - EJ20:2.0 Litre SOHC or DOHC
- EJ20T
This is not actually a valid code from Subaru, but is mostly used by enthusiasts (and can be seen in such context on webforums such as NASIOC)& also mechanics to describe the entire line of 2.0 litre turbocharged engines that have been available over time. When referring to the EJ20T, one is speaking of one of the following: - EJ20G
EJ20G fall in to 2 categories -early engines 1989-9/1996 -late wagon and automatic sedans from 9/1996 and later
to identify an early EJ20G
Coil on plug
Divorced idle air controller
Upturned inlet in turbo
Air to water or slated intercooler
Late model EJ20Gs are the same general design as the EJ20K
Usage:
Legacy RS 89-93
Legacy RS-RA 89-93
Legacy GT 89-93
Impreza WRX 92~96
Impreza WRX Wagon 92~98
Impreza WRX STi 94~96 - EJ20K
to identify an EJ20K
Wasted spark coil pack on center of manifold
Inlet under manifold
Divorced idle air controller
Usage:
Impreza WRX & STi 9/96~9/98 - EJ205
This engine series is used for non-Japanese marketed WRX models in the world market as of 1999. The Japanese WRX models use the EJ207 from 1999~2001, except the 5-door wagon which also uses the EJ205. After 2001, all WRXs use the EJ205. to identify an EJ205:
Coil on plug
idle air integrated into throttle body
Usage: Impreza WRX 99~current - EJ207
to identify an 9/99-9/2000 EJ207
Wasted spark coil pack off center of manifold
Inlet under manifold
Red manifold
Usage:
Impreza WRX STi 9/98~00 (JDM, specifically Homologation models for World_Rally_Championship) - EJ20TT
This can refer to one of the 2.0 Litre DOHC Sequential Twin Turbo and intercooled engines (EJ20H/EJ20R), used in specialty Legacy's. Yet like EJ20T, it is not actually a valid code used by Subaru themselves.
Usage:
Legacy GT & B4 (JDM) - EJ20H
Usage:
Legacy BD/BG5 JDM GT's (183 kW manual & auto) and GTB's (190 kW auto) - EJ20R
Usage:
Legacy BD/BG5 JDM RSB and GTB's (205 kW Manual)
B4 Legacy 280bhp - EJ22:2.2 Litre SOHC
Subaru EJ22
Usage:
Impreza 95-01
Legacy 90-99 
EJ22E
2.2 litre:135 bhp @ 5800 rpm 140 ft·lbf @ 4800 rpm
Australian model - 100kW @ 6000 rpm 189Nm @ 4800 rpm
Usage:
Legacy 89-96
Liberty 89-96- EJ22T
2.2 Litre SOHC Turbo, no intercooler
Also known affectionately by enthusiasts as Subaru's bulletproof engine.
Legacy 89-94 (USDM only from 1991) - EJ22K
Usage:
Impreza WRX STi 22B (JDM) - EJ25:2.5 Litre,EJ251
The EJ251 is a 2.5 L (2457 cc) Horizontally Opposed SOHC Engine with a bore of 99.5 mm and a stroke of 79.0 mm. Compression ration is 10.0: 1. Firing order is 1 - 3 - 2 - 4.
121kW and 226Nm
Usage:
Impreza RS 00-05 (US)
Impreza Outback 00-05 (US)
Forester 00-05
Outback 00-05 (US) - EJ252
SOHC
Usage:
Legacy 00 - EJ253
SOHC - 165 HP @ 5600 RPM RPM, 166 .lb-ft torque @ 4000 RPM
Impreza 99/05+
Legacy 00+
Forester 99/05+
Baja 05+ - EJ25D
DOHC - 125kW @ 6000 RPM 238Nm at 2800
Usage
Impreza 98
Legacy 96~99
Forester 98~99 - EJ25E
SOHC 16 valve
Usage:
Impreza RS 99~01
Forester 99~00
Legacy 00~01 - EJ255
2.5 litre DOHC AVCS turbocharged, with sodium-filled valves originally designed for North American market, now sees usage in some European Imprezas and Legacies destined for Australia and South Africa.
Usage in North America:
Impreza: 2006 - present
Forester: 2004 - present
Legacy: 2005 - present
Baja: 2004 - 2006
Usage in the rest of the world:
Legacy: 2005 - present
Impreza: 2006 - present - EJ257
DOHC 16 valve turbo
Usage:
US Market Impreza WRX STi MY04~present (300 hp)
Asian, European Market Impreza WRX STi 05~present (280 hp, 40KGh/m)
An unexpected contract with Subaru, the automobile branch of Fuji Heavy Industries, brought substantial monetary backing and additionally an exclusive "works" engine for free. The Japanese took over 51% of Coloni formula, paid the debts and supported the new alliance with a brand new, unique engine. It was a flat-12 engine which in fact was penned by Carlo Chiti. Chiti's Motori Moderni company at Novara had supplied V6 Turbo engines for the Minardi Formula One team from 1985 to 1987, and in 1988 Chiti had penned a normally aspirated V12 engine that attracted Subaru. In late 1988, the Japanese commissioned Chiti to design a new Formula One engine with a "flat" layout - as used in their road cars - that was ready in the Summer of 1989. The engine - now with a Subaru badge - was tested in a Minardi M188 chassis but due to a severe lack of power Minardi very soon lost interest. After a few months of searching, Subaru found the Coloni team. Eventually, the "Subaru Coloni" Team was founded with Enzo Coloni staying on board as the man for operational business.
By the beginning of 1990, the "Subaru" flat engine was not producing more than 500 bhp, so the Coloni Subaru was by far the least competitive machine regularly competing in Formula One in 1990. Subaru and Chiti agreed to build a new V12 engine for Summer 1990 together with a completely new chassis, but in the meantime the flat engine should be used by the "Coloni Subaru" Team in a carry-over chassis. Early in 1990, a handful of Enzo Coloni's mechanics worked on a single C3 and tried to put the Subaru engine in it. The work was not done until the day the FIA started shipping the Formula One material to Phoenix. In the pits at Phoenix, the car was assembled for the very first time, and a short private "practice" took place on a parking area of an American supermarket. On prequalification day of Phoenix the world saw Coloni's "new" model C3B which wore a white, red and green livery. Without an airbox but with wide, long sidepods, it looked like a tank, was overweight by 300 pounds and nearly impossible to handle. Neither at Phoenix nor at any other event, did Bertrand Gachot, Coloni's new driver, manage to prequalify the car. As the season went on, improvements were few and results stayed nowhere. Meanwhile, no success could be seen at Coloni's plant in Perugia where obviously nobody worked seriously on a new car. In May, Enzo Coloni was sacked by Subaru, but no improvement came. In June, the Japanese company withdrew completely and sold the team back to Enzo Coloni, debt free, but with no sponsors and no engines. By the German Grand Prix Coloni had arranged a supply of Cosworth engines, prepared by Langford & Peck. An improved car also appeared in Germany. The "new" Coloni C3C was simply a 1989 C3 with minor changes in aerodynamics. The car was quicker, but not enough to achieve any serious results. Gachot was usually able to prequalify his car, but the "main" qualification was still out of reach. By the end of the season, Coloni had not taken part in a single Grand Prix.Subaru 2.5-liter Turbo Boxer Engine won 'best engine' in the 2.0-2.5 litre category in the 2006 International Engine of the Year awards.
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