How to set the LED display brightness and color is often encountered problems, and now LED display technology has been relatively mature, each enterprise-made display of the structure, the principle is basically similar, the price is basically the same, but its performance difference is relatively large. Color ratio is different, resulting in the image effect is very different; module scanning frequency, operating current not only affect the brightness, but also related to the life of the problem.
How to set the LED display brightness and color
When manufacturing a large screen, first select the LED or display module according to the brightness index, followed by the selected product red, green, blue color ratio to determine which color as a benchmark, generally a low brightness ratio as a Brightness reference, when the benchmark has reached a maximum brightness, adjust the other (two-color) or two (full color). When the display screen is two colors, most of the case to green as the base, adjust the red diode operating current. Generally to reduce the operating current to balance the color yellow for the adjustment criteria, so it is necessary to reduce the brightness of the entire display screen. When the color of the display is adjusted to the best balance, the brightness of the screen is reduced. If the display screen in order to achieve the brightness requirements, each color will reach the maximum brightness, then lost the color balance, for example: two-color screen yellow color reddish, or green.
TTL output low level is about 0.4V, if the input current input, the normal maximum infusion current of 35mA, when more than this current, the output low rise, with the current increases, the output low High, that is, the output voltage is greater than 0.4V circuit is still working properly. In the display scan circuit, the working current of 20mA can meet the requirements of the control red, because the red LED brightness is relatively high; green LED operating current is higher than 20mA, the current is about 30 ~ 50mA, this time, 74HC595 output The voltage is also increased, the reason is 74HC595 output resistance, and is a nonlinear change.
The scanning circuit operates in a dynamic scan and a static drive. The scanning frequency of the display screen is limited by the structure of the display module. Each module has 8 × 8 LEDs. The line data of the entire display module are all connected in series. The data time is longer. When the scanning frequency is 100Hz, the brightness of the whole screen It will be reduced. If you reduce the scanning frequency of the screen, the display brightness decreases. Experiments show that the relationship between scanning frequency and color is relatively small.
Facts have proved that a reasonable analysis of the technical characteristics of the circuit, so that the circuit is in the best working condition, will be able to achieve the desired display. Choose a different company's 74HC595 circuit, the display is different, in a display, try to choose the same circuit, to avoid the impact of different parameters of the circuit display.