Method for adjusting brightness and color of LED large screen
Sep 15, 2021
Each pixel combination has RGB diodes, which display full-color pictures of different colors by turning on and off each group of pixel lights. The adjustment method of brightness and color of LED large screen is roughly as follows:
When manufacturing a large screen, first select the LED or display module according to the brightness index, and then determine which color is the benchmark according to the brightness ratio of red, green and blue colors of the selected product. Generally, the one with low brightness ratio is used as the brightness benchmark. When one of the benchmarks has reached the maximum brightness, adjust the other (two-color) or two (full-color). When the LED large screen is two-color, in most cases, the working current of the red diode is adjusted based on green.
Generally, reduce the working current and take the balance color yellow as the adjustment standard, so as to reduce the brightness of the whole display screen. If the color of the LED large screen is adjusted to the best balance state, the brightness of the screen will be reduced. If the display screen reaches the maximum brightness of each color in order to meet the brightness requirements, the color balance will be lost, for example, the yellow color of the two-color screen is red or green.
TTL output low level is about 0.4V. If it is used as perfusion current input, the normal maximum perfusion current is 35mA. When this current is exceeded, the output low level rises. With the increase of current, the output low level rises continuously, that is, if the output voltage is greater than 0.4V, the circuit still works normally. In the display scanning circuit, the working current of 20mA can meet the requirements of controlling red, because the brightness of red LED is relatively high; The working current of the green LED is higher than 20mA, and the current is about 30 ~ 50mA. At this time, the output voltage of the 74HC595 also increases. The reason is that the 74HC595 has output resistance and changes nonlinearly.
The scanning circuit of LED electronic display screen works in the way of dynamic scanning and static driving. The scanning frequency of LED large screen is limited by the structure of display module, and each module has 8 × 8 LEDs. The row data of the whole display module are all connected in series, and it takes a long time to update the data once. When the scanning frequency is 100Hz, the brightness of the whole screen will be reduced. If the scanning frequency of the screen is reduced, the display brightness is reduced. Experiments show that the relationship between scanning frequency and color is better than.
