4 Misunderstandings When Choosing Led Flood Lights
Buy LED flood lights should pay attention to light efficiency, color temperature, color rendering index, light decay. The first three are common parameters for all luminaires, and the final light fading is a unique property of LEDs as a semiconductor.
In addition, some people have the following misunderstandings when choosing LED lights!
Misunderstanding 1, the expectation of the actual service life is too high.
LED manufacturers expect LED life to reach 100,000 hours MTBF
Luminous flux lumens also decay over time. So although the LED illumination time can be very long, MTBF is not the only consideration for determining the service life.
The attenuation of LED lumens is affected by many environmental conditions such as ambient temperature, humidity and ventilation. Lumen attenuation is also affected by control, thermal management, current levels, and many other electrical design considerations (cited by CK Corporation, USA).
Many salesmen may give customers some ambiguous information for some reason when selling LEDs, which is misleading. For example, the service life of LEDs is about 100,000 hours, and 100,000 hours here refers to manufacturers’ expectations.
LED life. As the light source of illumination, the brightness of the lamp has a process of gradually decaying and darkening (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%, the human eye can clearly feel the change in brightness. At this time, the brightness of the product is not suitable for illumination. Many manufacturers and contractors use low-cost LEDs for three months to half a year.
It is often found that the brightness of LEDs is not as bright as when they were installed, or even close to nothing. It is precisely because LED light is not considered. In summary, when we buy LEDs, we should pay attention to its light decay speed, not the use time.
Misunderstanding 2, the actual luminous angle is taken as an effective angle.
The illumination angle of the LED is divided into an effective angle and an actual illumination angle. The angle at which the luminous intensity value is half of the axial strength value and the angle of the luminous axis (normal) are effective angles. The angle of view of the half angle angle (or half power angle) is the actual light angle. Angles other than half of the axial strength are not considered effective angles in practical applications because the light is too weak. (The picture below shows the side view of the piranha particles. The angle between the solid line and the dotted line is not included in the effective angle.)
Therefore, we should pay attention to the actual illumination angle of the product when purchasing the product. When calculating the quantity of products used in the project, the actual illumination angle can be used as the reference value.
Misunderstanding 3, the higher the power, the higher the brightness.
The brightness of an LED is measured by the intensity of illumination, which is the luminous intensity in the direction of the normal (to the axis of the cylindrical luminous tube), that is, the luminous flux emitted by the unit solid angle, in units of candlelight (Candela,
Cd). Since the luminous intensity of a general LED is small, the luminous intensity is usually measured in millicald (mcd). Generally speaking, the light source emits its luminous flux with different intensity in different directions, and the visible light radiation intensity emitted by the solid angle in a specific direction is called light intensity, which is simply referred to as axial brightness.
The concept of electric power is introduced from the amount of work done by force in equal time. The current is fast and the electric power is large; the current is slow, the electric power is small, or the electric work is more in the same time, the electric power is larger. On the LED, the higher the power, the higher the brightness of the product. Taking Yimei Electronics’ three-lamp red LED as an example, when the axial brightness is 1200mcd, the current is 40ma and the power is 0.48W; the three-lamp white LED has the same brightness, the current is 18ma, and the power is only 0.24W; The power of the two lights at the same brightness is different. So what we pay attention to when buying LEDs is its axial brightness, not power.
Misunderstanding 4, about the purchase of white LED modules.
1. High-brightness (blue-green) white LED flood lights are sensitive to static electricity and are determined by the characteristics of the LED itself. Exceeding the maximum forward DC current and maximum reverse voltage it can allow can cause damage or breakdown of the LED. For example, a three-lamp LED module, each lamp will have an anti-static resistor, plus a resistor for current limiting, a total of four. The anti-static resistor can effectively suppress the damage caused by static electricity to the LED.