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led

LED, which converts the electrical energy into light energy, is made from compounds from gallium (Ga), arsenic (As), phosphorus (P) and nitrogen (N).


Category:

Led can be divided into ordinary monochromatic led, high brightness led, ultra high brightness led, allochroic led, flashing led, voltage control type led, infrared led and negative resistance led, etc. Led has two control mode: constant voltage and constant current. And there are many way to adjust the brightness, such as analog dimming and PWM dimming. Most of the LED is constant current control, so that we can maintain the stability of LED current and it is not easy to change by VF, which can prolong the lifespan of led.


1.Ordinary monochromatic led

Ordinary monochromatic led is small volume, low working voltage and current, uniform and stable light, fast response speed, long lifespan, available to all kinds of dc, ac, pulse, etc, power supply, It is a current-controlled semiconductor device, and it needs to be connected to a suitable current-limiting resistor when used. The luminescent color of an ordinary monochromatic led is related to the wavelength of the light, and the wavelength of the light is determined by the semiconductor materials. The wavelength of red led is commonly 650 ~ 700nm, the wavelength of amber led is 630 ~ 650nm, orange led is about 610 ~ 630nm, yellow led is about 585nm, the green is generally 555 ~ 570nm. The common monochromatic led in China are BT series, FG series and 2EF series. There are SLR series and SLC series from foreign countries.

2.High brightness monochromatic led

The semiconductor materials used in high luminance monochromatic led and ultra-high brightness monochromatic led are different from ordinary monochromatic led, so the intensity of luminescence are different. Usually, high brightness monochromatic led uses aluminum gallium arsenic materials, ultra-high brightness monochromatic led uses phosphorus indium gallium arsenide, and ordinary monochromatic led use gallium phosphide or phosphorus materials such as gallium arsenide.

3.Allochroic led

Allochroic led is led that can change the color of light. The allochroic led can be divided into two colors: two-colors led, three-colors led, and multi-colors (red, blue, green and white) led. The allochroic led also can be divided into two terminal color-changing led, three-terminal color-changing led, four-terminal color-changing led and six-terminal color-changing led. The commonly used two-color led has 2EF series and TB series, and the commonly used three-color led has 2EF302, 2EF312, 2EF322 and other models.


4. BTS

BTS is a special luminescent device composed of CMOS integrated circuit and led, which can be used for alarm indication, under-voltage and over-pressure indication. This led is not required to be connected to other components when used, so long as the appropriate dc working voltage (5V) is added at both ends of the pin.

5.BTV

The ordinary led is a current-controlled device, which needs to be connected with the current limiting resistance.The voltage controlled led (BTV) is a combination of led and current-limiting resistance, which can be directly connected to both ends of the power supply to led the common red led voltage can work at 3v -10v, such as YX503URC, YX304URC,YX503BRC led.

6. Infrared led.

Infrared led is one light-emitting device which can directly convert electrical energy into infrared light(not visible) and infrared radiation, mainly used in various kinds of optical and radio transmission circuit.The structure and principle of the infrared led is similar to that of ordinary led and the difference is just the semiconductor materials. The commonly used infrared led includes SIR series, SIM series, PLT series, GL series, HIR series and HG series.


Characteristics:

1.Voltage

LED uses the low voltage power supply, which is between 3 to 24 v dc, and there are a few DC36V, DC40V etc, so it is a safer than using high voltage power supply. It is especially suitable for public places.

2.Efficiency

The consumption of power is about 80% lower than that of incandescent bulbs and is about 40% less than energy-saving lamps.

3.Applicability

Small size. Each unit of LED chip is 3-5mm, so it can be made into various shapes of devices, and suitable for the changeable environment.

4.Stability

The lifespan of led is about 100, 000 hours and the light failure is 50% of the initial light failure.

5. Response time

The response time of the incandescent lamp is millisecond, and the response time of the LED lamp is nanosecond.

6. Environment pollution

Led doesn’t contain harmful metallic mercury and so on.



Reasons of light failure:

1. Quality of led:

1) The adopted led chip has a poor constitution and fast fading brightness.

2) There are defects in the production process. The heat dissipation of led chip from the PIN is not good, which leads to the high temperature of the led chip and accelerates the speed of light failure.

2. Application conditions:

1) Led is driven by constant current, and some led is driven by voltage, which accelerate the speed of light failure.

2) The driving current is bigger than the rated driving condition.


Advantages:

1. Small volume

The led is basically a small chip that is encapsulated in an epoxy resin, so it's very small and light.

2. Low voltage

Led power consumption is quite low, generally speaking, the working voltage of the led is 2-3.6v.It only requires a very weak current to work.

3. Long lifespan

Under the right current and voltage, led can last up to 100,000 hours.

4. High brightness and low heat

Led uses cold luminescence technology, the heat is much lower than the common lighting lamps with same power.

5. The environmental protection

Led is made of non-toxic materials, unlike fluorescent lights that cause pollution, and led can be recycled.



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