Knowledge

The application of infrared LED

daisy.chen — Wed, 20 Aug 2008 08:41:17 +0000

Common infrared LED that emits infrared rays has the same appearance with visible light LED. Its appropriate operating voltage is around 1.4v and the current is generally smaller than 20mA. Current limiting resistances are usually connected in series in the infrared LED circuits to adjust the voltages, helping the LEDs to be adapted to different operating voltages.

When using infrared rays to control correspondent unit, the controlling distance is in direct ratio with the emitting power. In order to lengthen its controlling distance, infrared LED should be operated under pulse state as the effective transmitting distance of the pulsed light (modulated light) is in proportion with the wind-induced current of the pulses. Thus, by increasing the peak value (Ip) of the pulses, the emitting distance of the infrared LED can also be lengthened. One way to increase Ip is to diminish the duty ratio of the pulse; that is to reduce the width of the pulse (T). The duty ratios of the working pulses for some color TV’s infrared remote controllers are around 1/3-1/4; and for some other electronic products, the duty ratios of the infrared remote controllers can even be as small as 1/10. Through reducing the duty ratio of the pulses, the emitting distance for small power infrared LED can also be increased in a large extent. Ordinary infrared LEDs can be divided into the following three types: small power one (1mW-10mW), medium power LED (10mW-50mW) and large power LED (50mW-100mW and above). The modulated light can be generated by adding pulse voltage with specific frequency on the driving diode.

The controller with infrared LED can emit infrared rays to take control of correspondent unit, and at the controlled unit end, there is also a receiving device to turn the infrared light into electricity, such as infrared light receiving diode, photoelectric triode and so on. Emitting and receiving matched infrared diode has also been applied in practical use.

There are two emitting-receiving modes for infrared LED and the controlled unit, one is direct light emitting mode, and the other is reflecting light mode. In the direct light emitting mode, the emitting diode and the receiving diode are installed in the emitting end and the controlled unit end respectively, with a certain distance between them. As to the reflecting light mode, the lighting diode and the receiving diode are in parallel. Only when the infrared rays emitted by the diode were reflected by something can the receiving diode get the infrared rays, thereby stimulate the controlled unit to operate. Besides, infrared emitting circuit with double diodes bears higher power and longer functional distance.

Infrared LED chips with different wavelengths can be applied in extensive devices, for example:

1. Infrared LED chip with wavelength of 940nm: suitable to be used in remote controller, such as remote controllers for household appliances.

2. 808nm: suitable to be used in medical treatment appliances, space optical communication, infrared illumination and the pumping sources of the solid-state lasers.

3. 830nm: suitable to be used in the automated card reader system in freeway.

4. 840nm: suitable to be used in colored zoom infrared waterproof video camera.

5. 850nm: suitable to be used in video cameras that are applied in digital photography, monitoring system, door phone, theftproof alarm and so on.

6. 870nm: suitable to be used in video cameras in marketplace and crossroad.

Advantages of LED fluorescent lamps

daisy.chen — Fri, 08 Aug 2008 07:16:46 +0000

LED fluorescent lamp is the newest product line in the fluorescent family and is considered to be the final replacement for traditional fluorescent lamp. It is made up of white LED chip modules. Provided with the advantages of long life-span, radiation-free, energy saving, environmental friendly and stroboflash-free, LED fluorescent lamp is superior to other kinds of lamps.

Besides, the installation of LED fluorescent lamp is quite easy. Just to replace the original fluorescent lamp with the new LED one, and to take out the starter. What’s more, the electricity saving efficiency can reach as high as 50% compared to ordinary fluorescent lamp and the life span is more than 10 times than that of ordinary one, almost totally free of maintenance. LED fluorescent lamp is adaptive to be used in offices, factories, marketplaces, schools and houses and so on indoor spaces.

The following passages are going to sum up the advantages of LED fluorescent lamp.

1. Environmental friendly

Traditional fluorescent lamp contains large amount of mercury vapor which will do harm to the environment if the lamp is broken up and the vapor volatilize into the atmosphere. On the contrary, LED fluorescent lamp does not contain mercury or lead, doing no harm to the environment. So, LED products are recognized to be the green lighting lamps in the 21st century.

2. Low heat

Compared to traditional lamps which will generate a large amount of heat, LED lamps can directly make electric energy into light energy, causing less heat and no waste of the energy.

3. Noise-free

LED lamp will not produce any noise, enabling it to be a good choice for illumination application in high precision electrical instrument. It is also fit to be used in occasions like libraries, offices and so on.

4. Soft light beams and stroboflash-free

Traditional fluorescent lamp uses alternating current, which will generate 100-120 times of stroboflash per second. As to LED fluorescent lamp, it can directly switch the alternating current into direct current, without causing any flickering, helpful to protect the eyes.

5. Free of ultraviolet radiation

Traditional lamps will generate ultraviolet radiation, thus will attract mosquitoes to fly around the lamps. LED lamp doesn’t have this disadvantage, thus the indoor space will become cleaner.

6. Wide-range of adjustable voltage

Traditional fluorescent lamp should recur to rectifier to release high voltage to get brighten up. If the voltage fell, the lamp will went out. However, LED lamps can be lighted within a certain voltage range (80V-245V) and its brightness can be adjusted.

7. Energy-saving, long life-span and low cost

The power consumption for LED fluorescent lamp is lower than 1/3 of the traditional lamp’s consumption, and the life span for it is 10 times longer than that of traditional one. So there is no need to change the lamp for a long period of time, reducing the manpower and other costs.

8. Rigid and safe

LED lamp body is made by epoxy resin instead of glasses like other traditional lamps. So it is more rigid and safe. Even if falling to the floor, LED lamp will not be broken easily. Users can set their heart at rest when using LED lamps.

On causes of LED lumen attenuation

daisy.chen — Thu, 31 Jul 2008 06:51:54 +0000

LED lumen attenuation is the weakening of the light signal during transmission. LED products made by global leading manufacturers at the present stage have lumen attenuation in different grades after used for a period of time and this phenomenon also exists in high power LEDs. Then, what causes LED attenuation? Lumen attenuation is directly related to the temperature, and is mainly determined by the chip, phosphor used and the packaging technology. At present, lumen attenuation has become the chief problem for white LED to march into civil lighting field. There are two main problems that cause LED lumen attenuation:

Ⅰ The quality of the LED product itself

1. The brightness of LED will attenuate quickly if the quality of the adopted LED chip is not good.

2. The production technology has some defects. If the heat generated by LED chips can not be exported out of the chip smoothly by the PINs, LED chips may be over heated and thus causing chip attenuation more serious.

Ⅱ The operating condition

1. LED should be drove by constant current, if drove by voltage, LED lumen attenuation will be caused.

2. If the driving current is larger than the rated value, LED lumen may easily get attenuated.

Among the various causes of LED products lumen attenuation, “heat” is the pivotal one. Many manufacturers pay little attention to the heat dissipation of the products, leading to a much more serious lumen attenuation compared to those products that dissipate heat properly. Besides, thermal resistance of the LED chip itself, silver colloid, the heat dissipation effect of the substrate and golden wire problems are also related closely to LED lumen attenuation.

Common problems in the use of LED luminous letters and corresponding solutions

daisy.chen — Fri, 25 Jul 2008 09:51:25 +0000

LED luminous letter (or caption machine) adopts light emitting diode as lighting source. It is usually installed on the top of buildings or on wall surface in the shape of given letters or signs. LED luminous letter chooses high brightness LED chips and uses specific system to take control of the dynamic video of the letters or signs. The unique designed LED luminous letter surpasses the traditional outdoor advertisement in function. Its abundance colors make it much superior than traditional neon light and make break through in application variety. Meanwhile, the power-saving trait and long life-span of LED reduce maintenance and other cost for LED luminous letter in a large extent.

However, users will frequently be confronted with some problems in practical use. The following passage is going to sum up common problems in the use of LED luminous letters and the corresponding solutions for your reference.

Problem 1: Short life-span.
Although the theoretic life-span for LEDs produced by normal manufacturers can reach as long as 80,000 hours, a large number of LED luminous letters have to replace its LED modules frequently even less than one year’s usage. This will bring a lot of troubles and economic losses to customers and advertisement manufacturers.

Solutions:
To buy qualified LED single lamp grains from normal manufacturers (which provide quality parameter for the grain) and make modules yourself. Never to buy cheap LED single lamp grain or finished modules in the electronic products market. If it is necessary to buy modules, you should check how many resistance the module have. The module with only one resistance had better not to be used because resistors will easily get heated and broken after long time durative operating. Once the resistor is burned out, the module will be light-off. Generally, LED lamps are unlikely to be broken, so if the module is broken, just change the resistor with another one that have the same resistance value. Choosing modules with two resistors will leave out this trouble and cut more expenses. In addition, buyers had better get some knowledge of the module makers’ facilities before the purchasing to see whether they have anti-static equipment. Those LED modules produced without anti-static facilities are easily damaged in use.

Problem 2: Quick fade out of the brightness.
The color of the pure and bright LED luminous letters will fade out obviously even after less then one year’s use, making the letters ill-looking.

Solution:
Safe operating current for LED lamp to is around 20 mA. If the current exceed this number, the brightness for the LED will be brighter, but its color attenuation will be quickened obviously. So, before buying the LED module, you should test its output current, making sure the value stay between 20mA and 22mA.(LED module with operating current less than 20mA will be not bright enough; while LED module with operating current exceeding 22mA will attenuate quickly).

Problem 3: Irregular color and obvious color difference.
This problem mainly showed when pure white LEDs are made into large size of luminous letters. The problem is not obvious in the fabricating of single module, but when the whole luminous letter sign is assembled, the color difference will be quite evident. The whole letter surface will be looking like a map with various colors.

Solution:
Color separating process should be undertaken before the white LED lamps are put into the market because white LED will emit light with diverse colors like pure white, blue or yellow. Most small factories don’t have color separating machine as it is expensive. So the white LEDs produced by these factories will be sent to larger factories to be separated. Careless color separating always happens under such circumstance. Some manufacturers even neglect this important process. When buying white LED, buyers should not blindly attracted only by the price, instead should buy qualified products and use identical batch of LED chips or modules with the same color number produced by identical maker.

Problem 4: Sudden light-off or occasional light-off of the whole or part of the letters.
After being used for a period of time, the whole or part of the luminous letters start to flicker, then occasionally light-off and finally completely went out. Most luminous LED modules in the market use plug-in connector, enabling the fixing of LED modules to be convenient for advertisement manufacturers. However, the plug-in connectors exposed in the air are easily eroded and get oxidated after being used for a period of time, leading to the happening of bad contact.

Solutions:
1. Not to use plug-in connector when fabricating modules, instead, using tinned copper lead to connect them and then welding them firmly by active carbon soldering tin.
2. Adopting man-made agate to fabricate complete airtight tridimentional hollow luminous letters to isolate them from the air.

Problem 5: The power-saving trait is not obvious due to the comparative larger power output of the LED luminous letters.

Solution:
Better to adopt LED luminous modules with five lamps in one group. By doing so, the power consumption will be reduced by 40% without changing the number of the lamps.

Classification of LED products

daisy.chen — Wed, 16 Jul 2008 09:53:11 +0000

LED which is becoming widespread owns various kinds of product. LED products can be classified into different types according to light emitting colors, outer surface trait and structure of the diodes, luminous intensity, operating current, chip material, function and etc. This passage is going to introduce four types of LED products classification.

1. According to light emitting colors of the diode:

LEDs are available in red, orange, green (subdivide into yellow-green, standard green and pure green) and blue and so on.

Some light emitting diodes have chips that bear two or three colors. Besides, the package (the plastic body) of LED may have light scattering agent or not, be colored or colorless, thus, LED can also be classified into the following four types: colored transparent, colorless transparent, colored scattering and colorless scattering.

2. According to the outer surface (plastic body) traits of the diode, LED can be classified into round LED, square LED, rectangular LED, surface LED, side LED, surface mount subminiature LED and so on.

Round LED can be divided into following types according to its diameter: φ2mm、φ4.4mm、φ5mm、φ8mm、φ10mm and φ20mm and so on. Round LED with diameter of φ3mm is generally noted as T-1 in abroad, φ5mm noted as T-1(3/4) and φ4.4mm noted as T-1(1/4).

The angle distribution condition of round LED’s luminous intensity can be evaluated by the value of its viewing angle. The following three types are classified according to the angle distribution of the luminous intensity:

(1) High directivity LED: This kind of LED generally adopts sharp head epoxy packaging or metal reflection cavity packaging, usually without light scattering agent. The viewing angle of this kind of LED varies between 5° and 20° or even smaller. With high directivity, it can be used as local illumination source or to build up an automated detecting system together with a light detecting machine.

(2) Standard type: It is generally used as indicator lamp. The viewing angle varies between 20° and 45°.

(3) Scattering type: Its is usually applied as indicator lamp that has comparatively bigger viewing angle which varies between 45° and 90° or even larger. It has more light scattering agent than the other types.

3. According to the structure, LED can be classified into full epoxy resin packaging, metal base, ceramic base epoxy resin packaging and glass packaging.

4. According to the luminous intensity and operating current.

According to luminous intensity, there are standard brightness LED (with luminous intensity less than 10mcd), high brightness LED (with luminous intensity between 10mcd and 100mcd) and ultrahigh brightness LED (with luminous intensity larger than 100mcd).

LED can also be divided into two types according to its operating current: standard type which runs at an operating current from more than ten mA to tens mA; low current LED which runs at an operating current below 2mA (however, with the same brightness as standard LED).

How to improve the brightness of LED display

daisy.chen — Wed, 09 Jul 2008 09:12:05 +0000

LED brightness can be improved through the following two methods:

1. To increase the light output of the chip itself: light output can be increased through improving the luminescence efficiency of the chip’s active layer or improving the external light extraction efficiency by optimizing chips’ shape or making larger scale chips that run high density current.

2. To use the light effectively. In other words, to increase the amount of light that irradiate towards the needed direction. In this method, light wave control technology is used. Through a better design of the optical structure shaped by the packaged epoxy resin, the light can be controlled to shine towards expected direction, thereby improving the brightness of LED.

The above are the methods to improve LED brightness, if the brightness of LED display runs under expectation, methods listed below can be adopted:

1. To alter the current magnitude that runs through the LED. Generally, LEDs allow a 20 milliampere operating current continuously. Only red LED has saturation phenomenon, other LEDs’ brightness are in direct ratio with the current amount that runs through them.

2．To realize grey scale control through adopting PWM (Pulse-Width Modulation) method. That is to change the width of the light pulse (duty cycle) periodically. If the time for the relighting cycle is short enough (in other words, the refresh rate is high enough), the dithering of the luminescence pixel can not be felt by eyes thanks to the visual persistence trait. As it is more adaptive to adopt digital control to realize PWM, meanwhile, as microcomputer is widely used to provide the content to display in LED screens, nearly all of the LED control systems are composed by main controller, scanning board and display control device. Main controller firstly captures data of all colors’ brightness in one particular screen image from the display adapter, then to distribute the data to the scanning boards. Each scanning board takes charge of certain rows of the LED display and the LED display control signal in each row can be transmitted in serial mode. Currently, there are two serial modes to transmit display control signal. One way is to make centralized control of each pixel’s grey scale in the scanning board. More detailed steps: the scanning board analyzes the data of each row of pixel received from the controller (PWM process), then the board will transmit the open signal of each row to corresponding LED light, controlling each LED to be lit on or to keep off state. The signal is transmitted in serial mode and in the form of pulse (the pulse signal will be 1 if it indicates LED to turn on, contrary, the signal will be 0). The device used in this method is less, but the data amount being transmitted is comparatively larger. In every relighting cycle, the grey scale level is in direct ratio with its pulse amount for each pixel, that is to say, 16 grey scale levels need 16 pulses and 256 grey scale levels need 256 pulses. As in LED display, the working frequency for the devices is limited, only 16 grey scale levels is achieved generally.

3. The serial transmitting content for the scanning board is not the on or off signals of each LED, but an eight-bit binary brightness value. If every LED has its distinct PWM to control its lighting time, a pixel under 16 grey scale levels need only 4 pulses and 256 grey scale levels need only 8 pulses in one relighting cycle, reducing serial transmission frequency greatly. Through this grey scale decentralized control method, 256 grey scale levels control can be achieved easily.

A Brief Discussion on LED Packaging Technology

daisy.chen — Wed, 02 Jul 2008 06:52:20 +0000

LED is the acronym of Light Emitting Diode. It is a kind of semiconductor device that is commonly used in indicator light and display board. LED is capable of transforming electric energy into light energy directly in high efficiency and its life-span can reach as long as tens of thousands hours to one hundred thousand hours. Compared to traditional bulbs, LED also bears the advantages of non-friable and power-saving and so on.

However, only well-packaged LEDs can be applied as terminal products in practical use. And the packaging types should be designed according to the requirements of each distinct type of LED.

Firstly, we need to figure out why should LEDs be packaged?

Through packaging, outer leads can be linked to the electrode of LED chips, thereby to protect the chips and to improve its luminescence efficiency. More important than the electrical signal output function, packaging makes sure that the diode chips to operate normally and to export visible light successfully. So the packaging is not an easy job as electric parameters and optical parameters requirements should be count on at the same time when doing the design.

Secondly, the packaging equipments used will be introduced here.

The requirements for LED packaging are strict. It is essential to use high-precision crystal solid machine to package no matter Lamp-LED or Surface Mount Device LED (SMD-LED). If LED chips were not placed into the package precisely, the luminescence efficiency of the overall packaging device will be influenced directly. Any deviation from the established position will prevent LED light to be reflected fully from the reflective cup, affecting LED’s brightness. So an advanced crystal solid machine with a PR System should be used in order to weld LED chips into the package precisely, without considering the quality of the lead frame.

The latter part of this passage is going to introduce different kinds of LED packages

LEDs applied in different occasions and LEDs with different sizes, heat-dissipation methods and luminescence efficiency will have different types of LED packages. Currently, LED packages can be divided into the following types: Lamp-LED, TOP-LED, Side-LED, SMD-LED, High-Power-LED, Flip Chip-LED and so on.

1. Lamp-LED
Lamp-LED adopts potting process. Firstly to inject liquid epoxy resin into the LED molding cavity, then to insert LED stent which is well pressed and welded into the liquid, finally to put it into the drying oven to solidify the epoxy resin. LED pared from the cavity will be the final product. As the manufacturing technique for Lamp-LED is comparatively simple and its cost is lower, its market share is comparatively high.

2. SMD-LED
SMD-LED is mounted to the surface of the circuit board. SMT (Surface Mount Technology) is usually adopted. This type of LED can use reflow soldering, and problems related to luminance, visual angle, smoothness, reliability and consistency can be well solved in SMD-LED. Meanwhile, lighter PCB and reflector material is used in SMD-LED. What’s more, heavy carbon steel chip pins used in Lamp-LED is got rid of after improvement, enabling a less amount of epoxy resin to be required in the filling of the display reflector, thus the size and weight of the LED is reduced. Generally, SMD-LED can cut product’s weight by 50% easily, making terminal application perfectly.

3. Side-LED
Currently, one of the focused problems for LED packaging is related to side-emitting. It should be made sure that the side-emitting intensity is the same with that of the surface emitting when LED is used as the backlight source of LCD. Although side-emitting can be realized through the design of a lead frame, its heat dissipation effect is not ideal. Thus the invention of a specially designed reflector by Lumileds Company comes out. Using the reflector’s principle, surface emitting LED can radiate side light, thus high power LED can be applied to large size LCD backlight modules successfully.

4. TOP-LED
TOP-LED is a commonly seen surface mount light-emitting diode. It is mainly used as the backlight or status indicator light of multi-functional thin profile handsets and PDA.

5. High-Power-LED
In order to get high power, high brightness LED light sources, manufacturers is now making efforts to produce high power LED with proper packages. At present, LED packages that can endure W scale power have been invented, such as Norlux Series high power LED package. It is a multi-chip assembly with a hexagon aluminum base board that functions as heat sink at the same time. Base board’s diameter amounts to 31.75mm. The emitting zone is located in its central part, with diameter of about (0.375×25．4)mm. Forty LED chips can be contained in one package. Generally, the future outlook for high-power-LED package is promising due to its high density chip assembly, high luminescence efficiency, low thermal resistance and high output power under large current flow.

It is obvious that the thermal characteristics of power LED can directly influence its working temperature, luminescence efficiency, wavelength, life-span and other factors. So it is important to focus on the packaging design process, manufacturing technology of power LED chips.

6. Flip Chip-LED
There are couple numbers of perforation in the PCB base board in Flip Chip-LED. Every perforation in one side of the base board is set with a kind of conductive material that is spread on the surface of the base board. Then couple numbers of unpackaged LED chips are fixed on the perforations on the side that has conductive material. The anode and the cathode of every single LED chip are connected to the conductive material on the surface of the base board through a tin-ball. Meanwhile, LED chips are adhered with transparent sealing glue that is a hemisphere shape on the side that faces with the perforation.

Conclusion

According to the solid-state lighting principle, the luminescence efficiency of LEDs can reach approximately 100%. So, it is called the new light source in the 21st century, and is possible to become the fourth generation light source after incandescence lamp, fluorescent lamp and high-intensity discharge lamp. In the future, manufacturers should focus on the development of high-power, high brightness LED. As packaging is the process to link the preceding and the following parts in LED industry chain, attentions should be specially paid to it.

On Application of High Power LED to Signal Lamps

daisy.chen — Wed, 25 Jun 2008 03:24:18 +0000

Alone with the extensive application of LED in every trade, high power LED is widely adopted as light sources in traffic, railway and electronic equipment signal lamps. As defined by its name, high power LED is provided with higher power and heat, with larger lumen than ordinary LED, thus enable it to shine brighter. Strict requirements are posed on the selection of high power LEDs used in signal lamps. Ordinary LED can not be used as signal lamps at random for the following reasons:

1. Ordinary LED generally adopts epoxy resin as the fixing board; while high power LED needs to use MCPCB.

2. Ordinary LED can use wave soldering machine or handmade soldering, while high power LED needs to use surface mount technology (SMT) soldering machine.

3. Surface mounting devices (SMD) need to be used as matched electronic devices in high power LED.

4. As high power LED adopts surface mounting technology, realizing the highly integration of its electronic devices, thus the amount of lamps board and power supply can be small. This is what ordinary LED and its matched devices can not achieve.

5. Ordinary LED bears lower power and heat, but its heat tolerance performance and heat dissipation effect is not as good as high power LED. As to high power LED, although it is comparatively concentrated, its devices are fixed on MCPCB through surface mounting technology, making the adding of radiator easily.

6. The life span of high power LED is longer and its light beams are more concentrated than those of ordinary LED.

Generally speaking, high power LED circuit has smaller amount of diodes and branches, enabling it to use power supply that provides constant current in every branch to make sure that every LED has the same power supply environment. Even when one or two LED circuit goes wrong, the current for other branches will not be influenced. Meanwhile, as the heat dissipation performance is good for high power LED, node temperature is comparatively lower than ordinary LED, enabling it to have a longer life span. Moreover, high power LED can support much larger operating current, about more than ten folds compare to ordinary one. Hence, several milliamperes’ control wave current will not do any infection on high power LED but will possibly damage ordinary LEDs, so attentions should be paid when choosing proper LEDs for signal lamps. For the above stated advantages, the application of high power LED to signal lamps is prevalent.

Range of New and Potential New Applications of LEDs

Emma — Fri, 20 Jun 2008 08:13:22 +0000

Nowadays, LED products are being used in numeric displays and indicator lights to a range of new and potential new applications, including exit signs, accent lights, task lights, traffic lights, signage, cove lighting, wall sconces, outdoor lighting and downlighting.

The following is the list of LED applications:

•    Streetlights
•    Large scale video displays
•    Architectural lighting
•    Status indicators on all sorts of equipment
•    Traffic lights and signals
•    Light source for machine vision systems, requiring bright, focused, homogeneous and possibly strobed illumination.
•    Exit signs
•    Motorcycle and Bicycle lights
•    Toys and recreational sporting goods, such as the Flashflight
•    Railroad crossing signals
•    Continuity indicators
•    Flashlights, including some mechanically powered models.
•    Emergency vehicle lighting
•    Elevator Push Button Lighting
•    Thin, lightweight message displays at airports and railway stations and as destination displays for trains, buses, trams and ferries.
•    Red or yellow LEDs are used in indicator and alphanumeric displays in environments where night vision must be retained: aircraft cockpits, submarine and ship bridges, astronomy observatories, and in the field, e.g. night time animal watching and military field use.
•    Red, yellow, green, and blue LEDs can be used for model railroading applications
•    Remote controls, such as for TVs and VCRs, often use infrared LEDs.
•    The NintendoWii's sensor bar uses infrared LEDs.
•    In optical fiber and Free Space Optics communications.
•    In dot matrix arrangements for displaying messages.
•    Glowlights, as a more expensive but longer lasting and reusable alternative to Glowsticks.
•    Grow lights composed of LEDs are more efficient, both because LEDs produce more lumens per watt than other alternatives, and also because they can be tuned to the specific wavelengths plants can make the most use of.
•    Movement sensors, for example in optical computer mice
•    Because of their long life and fast switching times, LEDs have been used for automotive high-mounted brake lights and truck and bus brake lights and turn signals for some time, but many high-end vehicles are now starting to use LEDs for their entire rear light clusters. Besides the gain in reliability, this has styling advantages because LEDs are capable of forming much thinner lights than incandescent lamps with parabolic reflectors. The significant improvement in the time taken to light up (perhaps 0.5s faster than an incandescent bulb) improves safety by giving drivers more time to react. It has been reported that at normal highway speeds this equals one car length increased reaction time for the car behind. White LED headlamps are beginning to make an appearance.
•    Backlighting for LCD televisions and displays. The availability of LEDs in specific colors (RGB) enables a full-spectrum light source which expands the color gamut by as much as 45%.
•    New stage lighting equipment is being developed with LED sources in primary red-green-blue arrangements.
•    Lumalive, a photonic textile
•    LED-based Christmas lights have been available since 2002, but are only now beginning to gain in popularity and acceptance due to their higher initial purchase cost when compared to similar incandescent-based Christmas lights. For example, as of 2006, a set of 50 incandescent lights might cost US$2, while a similar set of 50 LED lights might cost US$10. The purchase cost can be even higher for single-color sets of LED lights with rare or recently-introduced colors, such as purple, pink or white. Regardless of the higher initial purchase price, the total cost of ownership for LED Christmas lights would eventually be lower than the TCO for similar incandescent Christmas lights [citation needed] since an LED requires much less power to output the same amount of light as a similar incandescent bulb. More to the point, LEDs have practically unlimited life and are hard-wired rather than using unreliable sockets as do replaceable bulbs. So a set of LED lights can be expected to outlive many incandescent sets, and without any maintenance.
•    LED phototherapy for acne using blue or red LEDs has been proven to significantly reduce acne over a 3 month period.[citation needed]
•    As a medium quality voltage reference in electronic circuits. The forward voltage drop (e.g., about 1.7 V for a normal red LED) can be used instead of a Zener diode in low-voltage regulators. Although LED forward voltage is much more current-dependent than a good Zener, Zener diodes are not available below voltages of about 3 V.
•    Some flatbed scanners use an array of red, green, and blue LEDs rather than the typical cold-cathode fluorescent lamp as the light source. Having independent control of three illuminant colors allows the scanner to calibrate itself for more accurate color balance, and there is no need for warm-up.
•    Light bulbs
•    Lanterns
•    Computers, for hard drive activity and power on. Some custom computers feature LED accent lighting to draw attention to a given component. Many computer manufactuers use LEDs to tell the user its current state. One example would be the Mac, which tells its user when it is asleep by fading the LED activity lights in and out, in and out.

Analysis of High Power LED Reading Lamps

Emma — Fri, 20 Jun 2008 07:12:38 +0000

At present, three kinds of reading lamps are commonly seen in market: the traditional incandescent reading lamp, the halogen reading lamp and fluorescent reading lamp.

The incandescent reading lamp and the halogen reading lamp are cheap and emit the light with good continuity, yet they consume much energy and produce heat. If the power is high, they shine too much to make people dazzle; if the power is too low, the intensity of illumination is lower than requested.

The fluorescent reading lamp has a larger light pane, thus the shadow of the object which is shed on by the light is very small, which causes little impact on our eyes. However, the color rendering index of fluorescent reading lamp is lower and its frequency-flicker effect is inclined to make our eyes feel tired.
Lumps which contain mercury should not be abandoned like daily trash when they are used up. They should be collected and handled according to the relevant regularity. Some countries have made the law regarding this issue.

Currently, the market of high power LED reading lamp is still a burgeoning one; the price is high and customers know little about it. Nevertheless, LED reading lamp enjoys a vast market prospect. LED reading lamp has many advantages, such as eye-friendly, power-efficient, environment-friendly and lasting.

Power-efficient

The high power LED reading lamp consumes less electricity and work well with 3W~4W power.

Environment-friendly

LED reading lamp uses LED as its light source which won’t produce waste and thermal radiation.

Eye-friendly

The light produced by LED is close to the natural light which is good to our eyes. It is the ideal light source indeed.

Long life span

The life span of a LED lamp is between 50000 hours and 100000 hours and it is resistant to shock.

High illuminance

Suppose the distance between the light source and the desk is 350~400mm, the illuminance on the desk may reach more than 500 lx.

When the cost of LED lamps is cutting down step by step, the breakthrough development of LED lamp market can be predicted. High power LED reading lamps will be seen in many families and serve us by then.