In order to provide accurate and reliable information to users in the cockpit, the display used in the cockpit must have high reliability. At the same time, because the pilots of the aircraft must operate the instrument, and improve the readability of the cockpit display and alleviate the visual fatigue. The light intensity of the display should also be automatically and manually adjusted according to the surrounding environment and user needs, to avoid the user not seeing the display content when the ambient light is strong, or to feel glare when the ambient light is very dark. The brightness of the backlight of the liquid crystal display directly determines the average brightness of the display, and the brightness of the display is adjusted by adjusting the brightness of the backlight of the liquid crystal display. The author uses the domestic STC12C5624AD MCU to design a LCD backlight module driving and adjusting circuit, which can accurately measure the illumination of ambient light, and automatically and manually adjust the backlight brightness according to the ambient light. 1 Principle of display backlight adjustment Because of the particularity of the cockpit, there is a higher requirement for the reliability, accuracy and intelligence of the cockpit display. It is necessary to automatically adjust the brightness of the backlight according to the change of ambient light, which makes the human eye look more comfortable, and can also manually adjust the screen. Brightness to meet user requirements. The relationship between the ambient light xt and the brightness yt of the backlight screen can be obtained by research. When the ambient light is xt, the automatically adjusted brightness is: Yt=kxt+b (1) Where b is the minimum brightness required by the driver to see the displayed information on the screen when the ambient light is 0; k is a proportional constant that can be modified according to the user's habits, in response to the human being seeing the screen in a bright environment The ratio of brightness to ambient light required for the information on. When the user is not satisfied with the brightness of the auto-adjustment, manually adjust the brightness to yt' to call the following formula: The obtained b' and k' are checked to replace the b and k in the formula (1) to obtain a new calculation formula, in order to prevent The driver over-adjusts and sets bmin and bmax. Only b' is used to replace b with b'. When the factory sets the initial value bs, the user can restore b to bs by button. Kmin, kmax, and ks are also set for k. 2 circuit The circuit schematic diagram of the LCD backlight module is shown in Figure 1. It mainly includes two PN23CV type silicon photocells, single chip microcomputer, button circuit, LED backlight driving circuit with DD313 as the core and auxiliary circuit. The PN23CV type silicon photocell senses the illumination of the ambient light and the brightness of the backlight of the LCD screen. After the amplification process, the signal is transmitted to the single chip microcomputer, and the single chip calculates the theoretical brightness of the backlight of the liquid crystal screen, and compares with the actual brightness of the backlight of the liquid crystal screen to determine whether the liquid crystal needs to be adjusted. The brightness of the screen backlight. If necessary, the signal is sent to the backlight driving circuit with DD313 as the core. The pins 13, 11, and 6 of DD313 are respectively connected with red, green and blue LEDs to control the brightness of the LED, thereby adjusting the actual brightness of the backlight module of the liquid crystal panel. When the user is not satisfied with the result of the automatic adjustment, the signal can be sent to the single-chip microcomputer through the button circuit, and the single-chip microcomputer determines whether it is necessary to adjust the brightness of the backlight of the liquid crystal screen. After the LCD backlight brightness is adjusted, delay the time and modify the b and k values. The circuit program flow chart is shown in Figure 2 and Figure 3. When the user manually adjusts the display brightness, the buttons SW1 and SW2 are respectively connected to the interrupt 0 and the interrupt 1 of the single chip STC12C5624AD. Press the button output voltage to VCC, release the button, the output voltage is 0, press SW1 to indicate that the user requests to increase the display brightness, press SW2 to indicate that the user requests to reduce the display brightness, SW1, SW2 are pressed to return to the original factory b and The setting value of k and bs and ks, SW1 and SW2 are respectively connected to the pins 8 and 9 of the single chip microcomputer. 3 software programming The circuit function is realized by software programming. The STC microcontroller timer and interrupter are used to scan whether there is a button press, and then corresponding processing. 4 Conclusion In this paper, the 51-single-chip with superior performance and mature technology is used to realize the manual and automatic adjustment of the backlight of the cockpit display through the design of the peripheral circuit of the single-chip microcomputer and the programming of its timer and interrupt, so as to achieve the comfortable screen brightness that the user is satisfied with, so that the cockpit display The backlight adjustment is precise and reliable, and it is more intelligent and user-friendly.
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October 31, 2019