LCD contrast adjustment and temperature compensation
Contrast, or more appropriately, the contrast ratio of an LCD is the ratio of the light area to the dark area of the display. When the ambient temperature increases or decreases, the contrast changes. For most applications, this change in contrast is tolerable in the "normal" temperature range of 0°C to + 50°C. Most Sichuan Airlines LCD modules offer an extended temperature range option that allows the display to operate in a temperature range from -20°C to + 70°C. In general, contrast changes over such a wide temperature range cannot be ignored, which means that the contrast voltage should be adjusted according to changes in ambient temperature.
LCD contrast adjustment
During product development, the potentiometer is connected to the LCD's power rail, the potentiometer's head is connected to Vo, and the pot is adjusted for the best LCD appearance. Now you can leave the potentiometer there or replace it with a suitable pair of resistors. All modules produced by Sichuan Airlines are preset for optimal contrast at room temperature.
Contrast adjustment and temperature compensation
The relationship between liquid crystal fluid properties, contrast, voltage, and temperature determines that the LCD drive voltage may need to be compensated. Especially in the case of a wide operating temperature range of the display.
There are many ways to compensate the LCD drive voltage, such as manual adjustment by the user, or the product microprocessor provides the appropriate voltage to the LCD based on the measured ambient temperature. These methods are neither practical nor economical.
A common method of temperature compensation is to provide a circuit as shown below to automatically adjust the drive voltage.
The thermistor of the RTH should be pressed against the LCD module to detect the ambient temperature. The resistor R1 is adjusted to select a suitable initial voltage (or two fixed divider resistors can be used). R2 is used as the minimum bias resistor.
Many LCD modules produced by Sichuan Airlines have a built-in PWM function, and users can easily adjust the contrast of the LCD according to their needs.
