Solar Traffic Sign can be seen on most devices and circuits. What are the key parameters that need to be paid attention to when choosing the most basic LED traffic lights?
Parameter 1: Wavelength
Peak wavelength & dominant wavelength. The light that the human eye can see is not exactly the same as the light that the machine can see. Therefore, there are two wavelength indicators to represent: dominant wavelength and peak wavelength.
Peak wavelength: The wavelength corresponding to the place where the spectral luminous intensity or radiant power is maximum.
Dominant wavelength: the wavelength that the eye can see the color of the main light emitted by the light source is the main wavelength
Generally speaking, these two parameters are not much different. The choice mainly depends on the application. If it is used in an optical instrument, the instrument needs to identify the wavelength at this time, and the peak wavelength should be used in the selection. If it is used for instruction, because the recipient is a person, more consideration should be given to the dominant wavelength.
Color and wavelength. There is a one-to-one correspondence between color and wavelength. If you want to find the LED replacement material with the same color as before. The parameter wavelength can be directly compared. If the wavelength is the same, the color is the same. The following is the wavelength range of common colors.
Red (Red): R (610nm-640nm)
Yellow (Yellow): Y (580nm-595nm)
Blue (Blue): B (455nm-490nm)
Green (Green): G (501nm-540nm)
Purple (Purple): P (380nm-410nm)
Parameter 2: Luminous intensity
Luminous intensity (millicandle candela, unit mcd) is a measure of the amount of light emitted by the light source, that is, the brightness of the light that the instrument can receive.
In practical applications, the human eye's perception of different wavelengths of light is different. With the same radiant energy LED, we will feel that red light will be much brighter than green light. In actual design, sometimes different colors of LEDs are used at the same time. In order to ensure the consistency of the brightness of all LEDs, you can consider the appropriate selection of green LEDs with a higher luminous intensity.
Parameter 3: Forward voltage & forward current
LED is a kind of diode. In the case of forward conduction, the forward voltage Vf can be understood as the rated voltage required to make the LED emit light. The forward working current If can be understood as the rated current required to make the LED emit light. In general, the greater the forward operating current, the greater the LED brightness.
The greater the forward current If, the higher the temperature, the life will be affected. When the ambient temperature is high, for longer LEDs, it is recommended to reduce the forward current. Many manufacturers will list the corresponding curves of temperature and rated forward current in the data sheet.
Parameter 4: LED package
There are two main types of packaging: patch and in-line.
In general, the volume occupied by the patch will be smaller, and can also be selected by size.