Affects eyesight: 0603 blue light and UV violet light are the most unbearable to human eyes. The ability of blue light to kill human eye active cells is about 10 times that of green light, and UV violet light kills human eye active cells 10 times of blue light. Temporary exposure Low-wavelength blue light can kill a small amount of human eye active cells, and eventually become cancerous and form plaques. The main reason for the white light composition of the LED is to excite the phosphor by the blue light of 450-455NM wavelength. The lower the wavelength, the stronger the firing ability. Usually the wavelength of the LED is controlled within 500NM, that is, 450-455NM, or 455-460NM, which is the most damaged. In the strong section, if the wavelength becomes larger, the ability to excite the phosphor will decrease and the efficiency will decrease. In order to pursue brightness, people usually increase the blue light intensity of LED 0603. The longer the lamp is lit, the faster the phosphor decays, and the more intense the light in the blue band that human eyes come into contact with, thus causing certain damage to human eyes.
Some people have the following misunderstandings when choosing direct plug-in LED lights
Misunderstanding one is that the expectations of the practical service life are too high.
The LED manufacturer expects the life of the in-line LED lamp to reach 100,000 hours MTBF
(Average error-free time, a specification used by traditional lamp manufacturers to measure the life of a light source). However, like all fundamental light sources, the luminous flux of LEDs also decays over time. So although the light-emitting time of LED can be very long, MTBF is not the only consideration for certain service life.
The attenuation of LED lumens is affected by many environmental conditions such as ambient temperature, humidity and ventilation. Lumen decay is also affected by control, thermal management, current levels, and many other electrical design considerations.
Many salespersons may provide customers with vague information for some reasons when purchasing LEDs, which may lead to misleading. For example, the service life of LEDs is about 100,000 hours. The 100,000 hours here refers to the manufacturer’s expectations.
The service life of the LED. As the light source of lighting, the brightness of the lamp has a gradual attenuation and dimming process (such as fluorescent lamps, energy-saving lamps), this process is referred to as light decay. On application-level LEDs, when the light decay exceeds 50%, human eyes can clearly perceive the brightness change. At this time, the product brightness is not suitable for lighting. Many manufacturers and engineering companies have been using low-priced LEDs for about three months to six months, and often find that the brightness of the LEDs is obviously not as bright as when they were installed, or even almost nothing, because they did not think about the reason for the light decay of the LED. To sum up, what we should pay attention to when buying LED is its light decay speed, not the use time.
Misunderstanding two, regard the practical luminous angle as an effective angle.
The light-emitting angle of LED is divided into effective angle and practical light-emitting angle. The angle between the direction where the luminous intensity value is half of the axial intensity value and the luminous axis (normal) is the effective angle. The viewing angle (or half-power angle) twice the half-value angle is the actual light-emitting angle. Angles other than half of the axial intensity are not counted as effective angles in practical applications because the light is too weak. (The picture below is the side view of the piranha pellet, the angle between the solid line and the dotted line is not included in the effective angle)
Therefore, when choosing products, we should pay attention to the actual luminous angle of the product. When calculating the number of products used in the project, the actual luminous angle shall prevail, and the effective luminous angle can be used as a reference value.
Misunderstanding three, the greater the power, the higher the brightness.
The brightness of the LED is weighed by the luminous intensity. The luminous intensity refers to the luminous intensity in the direction of the normal line (the axis of the cylindrical luminous tube), that is, the luminous flux emitted per unit plane angle, and the unit is candlelight. Since the luminous intensity of ordinary LEDs is small, the luminous intensity is often used as a unit of millicandela (mcd). Generally speaking, a light source emits its luminous flux with different intensities in different directions. The intensity of visible light emitted per unit plane angle in a specific direction is called light intensity, or axial brightness for short.
Introduce the concept of electric power from the number of forces that do work in the same time. The faster the current does work, the greater the electric power; the slower the current does, the smaller the electric power, or in the same time, the more work the current does, the greater the electric power. On the LED, it is not that the greater the power, the higher the brightness of the product. Take the three-lamp red LED of Yimei Electronics as an example, when the axial brightness is 1200mcd, the current is 40ma and the power is 0.48W; under the same brightness, the current of the three-lamp white LED is 18ma, and the power is only 0.24W; it can be seen The power of the two kinds of light is different under the same brightness. So what we should pay attention to when buying LED is its axial brightness, not power.
Misunderstanding four, regarding the purchase of white LED modules.
1. High-brightness (blue-green) white LEDs are very sensitive to static electricity, which is determined by the characteristics of the LED itself. When it exceeds the allowable forward DC current and reverse voltage, it may cause damage or breakdown of the LED. For example, a three-lamp LED module, each lamp will have an anti-static resistor, plus the resistor for current limiting, a total of four. The anti-static resistor can effectively inhibit the damage caused by static electricity to the LED.
The current-limiting resistor is mainly used to limit the amount of current that the entire module passes through. This design can effectively improve the anti-overload capability of the in-line LED and enhance the stability of the product. At the same time, the completeness of the four resistor marks is also a sign that can easily identify whether the quality of the module is stable or not.
