1. Make a 3V DC power supply convenient for connecting light-emitting diodes by yourself, which is made of batteries. Two button batteries can be used, which are installed in a small plastic tube and lead out two probes as positive and negative output. The tail end is directly made into a switch with shrapnel. When in use, the positive and negative probes correspondingly contact the positive and negative pins of the LED, press and hold the switch at the tail end, and the LED is powered on.
2. Take an LED and light it with more than 3V DC. The light emitting head is facing and close to the photosensitive surface of the connected photosensitive resistor. At this time, the multimeter will read to distinguish the luminous brightness of the LED.
The gray level of LED display screen is very high, which can reach 256 to 1024. However, due to the limited sensitivity of human eyes to brightness, these gray levels can not be recognized. In other words, many people with adjacent gray levels may look the same. And eye discrimination varies from person to person. For the display screen, the more the human eye recognition level, the better, because the displayed image is for people to see after all. The more brightness levels that human eyes can distinguish, the larger the color space of the display screen, and the greater the potential to display rich colors. The brightness identification level can be tested with special software. Generally, the display screen can reach more than level 20, which is a better level.
The brightness of indoor full-color LED display screen should be more than 800cd / m2, and that of outdoor full-color display screen should be more than 1500cd / m2, so as to ensure the normal operation of the display screen, otherwise the displayed image will not be seen clearly because the brightness is too low. The brightness is mainly determined by the quality of LED die. The size of the visual angle directly determines the audience of the LED display screen, so the larger the better. The viewing angle is mainly determined by the die package. It is necessary to determine the brightness of LED display screen. At present, the brightness requirements of urban bright LED display screen, or new regulations are issued. If the brightness of LED screen is too high, it will cause trouble to nearby residents. In order to avoid adverse reactions, businesses need to have product related knowledge when customizing and maintaining LED displays
