LED basics: 12 LED important performance indicators

(1) LED color: The color of LED is a very important indicator. Every LED related lighting product must be marked. At present, the color of LED mainly includes red, green, blue, cyan, yellow, white, warm white. Amber and so on. This parameter must not be forgotten when we design and order (especially for beginners). Because of the different colors, the relevant parameters also vary greatly.

(B) LED current: LED forward limit (IF) current is more than 20MA, and LED light decay current can not be greater than IF / 3, about 15MA and 18MA. The luminous intensity of the LED is only proportional to the IF within a certain range. When IF>20MA, the enhancement of the brightness cannot be separated by the inner eye. Therefore, the operating current of the LED is generally chosen to be around 17-19MA. The front is aimed at the LED between the ordinary low-power LED (0.04-0.08W), except for some piranha LEDs (some are rated at around 40MA). value).

In addition to the continuous development of technology, high-power LEDs are also constantly appearing such as 0.5W LED (IF=150MA), 1W LED (IF=350MA), 3W LED (IF=750MA) and many more specifications, I am not one. As soon as you introduce it, you can check the LED manual yourself.

(3) LED voltage: Generally speaking, the LED is a forward voltage, that is, the positive pole of the LED is connected to the positive pole of the power supply, and the negative pole is connected to the negative pole of the power supply. The voltage is related to the color. The voltage of red, yellow and yellow green is between 1.8 and 2.4V. The voltages of white, blue and emerald green are between 3.0 and 3.6v. Here, I would like to remind you that there will be some differences in the LED voltage produced in the same batch. According to the manufacturer's specifications, when the external temperature rises, VF will drop.

(4) Reverse voltage of LED VRm: Maximum reverse voltage allowed to increase. Above the value, the LED may be damaged by breakdown.

(5) Color temperature of LED: It is expressed by absolute temperature K, which is a standard black body heating. When the temperature rises to a certain extent, the color begins to change from deep red to light red-orange-white-blue, and a certain light source and black body When the colors are the same, the absolute temperature of the black body at that time is called the color temperature of the light source.

Since the correlated color temperature is actually the black body radiation approaching the light source color, the evaluation value of the light source color performance is not an accurate color contrast, so the two light sources with the same color temperature value may still be in the light color appearance. There are some differences. Color temperature alone cannot understand the color rendering ability of the light source to the object, or how the color of the object is reproduced under the light source.

● Below are the correlated color temperatures for different light source environments. (for reference only)

● In addition, the color temperature of the light source is different, and the light color is different:

- The color temperature has a warm feeling below 3000k, reaching a steady atmosphere;
- The color temperature is between 3000k and 5000k as the intermediate color temperature, which has a refreshing feeling;
- The color temperature is above 5000k and it has a cold feeling.

(6) Luminous intensity (I, Intensity): unit candela, ie cd. The luminous flux emitted by the light source in a unit solid angle in a given direction is defined as the light intensity (degree) of the light source in that direction, the luminous intensity is for the point source, or the size of the illuminant is compared with the illumination distance. Small occasions. This amount is indicative of the ability of the illuminator to converge in space. It can be said that the luminous intensity describes how much the light source is "bright" because it is a common description of the optical power and convergence ability. The greater the luminous intensity, the brighter the light source appears, and the brighter the object is illuminated by the light source under the same conditions. Therefore, this parameter was used earlier for the description of the flashlight.

Now LED is also described by this unit, for example, an LED is 15000, the unit is mcd, 1000mcd=1cd, so 15000mcd is 15cd. The reason why the LED is expressed in millicd (mcd) instead of cd is because the earliest LED is relatively dark. For example, the standard 5mm LED in 1984 has a luminous intensity of 0.005cd, so it is represented by mcd.

The disadvantage of using "luminance" to indicate "brightness" is that if the two LEDs have exactly the same die, the degree of convergence is good. Therefore, users should not only pay attention to the high I value when purchasing LEDs, but also the angle of illumination. Many high-value LEDs are not achieved by improving their own emission efficiency, but by narrowing the lens's longer illumination angle. Although useful for LED flashlights, the observable angle is also limited. In addition, the same die LED, the I value of 5mm in diameter is more than double the size of 3mm, but only 1/4 of the diameter of 10mm, because the larger the lens, the better the convergence characteristics.

(7) LED luminous flux (F, Flux): unit lumens, ie lm. The amount of light emitted by a light source per unit time is called the luminous flux of the light source. Again, this amount is for the light source, is the size of the total amount of light emitted by the light source, and is equivalent to the optical power. The greater the luminous flux of the light source, the more light is emitted.

For isotropic light (ie, the light of the source is emitted at the same density in all directions), then F = 4Ï€I. That is, if the I of the light source is 1 cd, the total luminous flux is 4Ï€ = 12.56 lm. Compared with the mechanical unit, the luminous flux is equivalent to the pressure, and the luminous intensity is equivalent to the pressure. If the spot to be illuminated looks brighter, we must not only increase the luminous flux, but also increase the means of convergence. In fact, it is to reduce the area so that we can get more intensity.

It is important to know that luminous flux is also artificial. It may not be the same for other animals, and it is not completely natural, because this definition is based entirely on the human eye's response to light.

The human eye feels differently for different colors of light, and this feeling determines the conversion relationship between luminous flux and optical power. For the most sensitive 555 nm yellow-green light of the human eye, 1W = 683 lm, that is, the power of 1W is all converted into light with a wavelength of 555 nm, which is 683 lumens. This is the maximum light conversion efficiency and is also the calibration value because the human eye is most sensitive to 555 nm light. For other colors of light, such as 650 nm red, 1 W of light is only equivalent to 73 lumens, which is because the human eye is not sensitive to red light. For white light, it depends on the situation, because the light of many different spectral structures is white. For example, white light from LEDs, white light on television, and daylight vary widely, with different spectra.

In terms of common white LED lumens, it is 0.06W→3-5LM, 0.2W→13-15LM, 1W→60-80LM. (for reference only)

(8) LED illumination (E, Illuminance): unit lux is lx (formerly known as lux). The luminous flux of 1 lumen is evenly distributed over the illuminance produced on a 1 square meter surface.

(9) Color rendering: The degree to which the light source appears to the color of the object itself is called color rendering, which is the degree of color fidelity; the color rendering of the light source is indicated by the color rendering index, which indicates the color of the object under the light. The deviation of the color when the light (sunlight) is illuminated can reflect the color characteristics of the light source more comprehensively. Light sources with high color rendering perform better for color, and the color we see is close to natural color. Light sources with low color rendering have poor color performance, and the color deviation we see is also large.

The International Commission on Illumination CIE sets the color rendering index of the sun to 100, and the color rendering index of each type of light source is different, such as: high-pressure sodium lamp color rendering index Ra=23, fluorescent tube color rendering index Ra=60-90.

● There are two types of color development:

- Faithful color development: It is necessary to use a light source with a high color rendering index (Ra) to accurately represent the original color of the material. The value is close to 100, and the color rendering is best.

- Effect color development: To emphasize the specific color clearly, the beauty of life can use the additive color method to enhance the color rendering effect.

(10) Glare: Objects with extremely high brightness or strong contrast in the field of view can cause visual discomfort called glare. Glare is an important factor affecting the quality of lighting.

(11) LED life: LEDs can be used for more than 50,000 hours in general instructions, and some manufacturers claim that their LEDs can operate for about 100,000 hours. The main problem in this regard is that LEDs are not simply no longer functioning, and their rated service life cannot be calculated using traditional luminaire measurements. In fact, when testing the life of an LED, no one stays aside waiting for it to stop working. However, there are other ways to measure the lifetime of the LED. LEDs last because they don't cause filaments to blow. The LED does not stop working directly, but it gradually degrades over time.

It is predicted that high-quality LEDs can maintain more than 60% of the initial brightness after 50,000 hours of continuous operation. Assuming the LED has reached its rated service life, it may actually be still emitting light, but the light is very weak. In order to extend the life of the LED, it is necessary to reduce or completely dissipate the heat generated by the LED chip. Thermal energy is the main reason why LEDs stop functioning.

(12) LED illumination angle: The diode illumination angle is also the light scattering angle. It is mainly controlled by the addition of scattering agent during diode production. There are three categories:

(1) High directivity. It is usually a pointed epoxy package or a metal reflective cavity package with no scattering agent. The illumination angle is 5°-20° or less, and it has high directivity. It can be used as a local illumination source or combined with a photodetector to form an automatic detection system.

(2) Standard type. Usually used as indicator light, its illumination angle is 20°-45°.

(3) Scattering type. This is an indicator light with a large viewing angle, the illumination angle is 45°-90° or more, and the amount of the scattering agent is large.

Long-span Cable Tray is one type of cable tray which has a longer span and a more 

dedicated structure design,
It is not only available in outdoor indoor cable overhead laying of industries
as oil refining,chemical engineering,textile,mechanical,metallurgy,electricity,tv,broadcast
but also in underground engineering project such as subway,cable trench of 
air defense project and trestles in cable tunnel.
Long-span cable tray has three types,tray,ladder,perforated.Width under 800mm long-span cable tray
has no weld.Length of reinforced long-span cable tray could reach 3 to 4 to 6 meters.Reinforced 
long-span cable tray's installation could use less connections and support points.
Three types of side height,100mm
150mm,200mm.Double-sided strengthing type could cope long-distance and large load installation

Large-span Cable Tray

Industrial Cable Tray,Fiberglass Large Span Cable Tray,Frp Large Span Cable Tray,Large Span Cable Tray

Jiangsu Loncin Electric Equipment Co.,Ltd , https://www.loncincabletray.com

Posted on