Brightness Adjustment

The context is adjusting the brightness of an LCD panel that has an LED backlight. There are two aspects to this topic:

• User backlight adjustment methods
• System level design for adjusting the backlight

User Adjustment Methods

There are several ways the user can adjust the backlight brightness:

• OSD: Through the OSD (On Screen Display) menu system. This might by using physical OSD buttons or using an IR remote control.
• RS-232: Via RS-232 commands. So this might involve connection to a control PC or to a small board, for example with a pic processor, to control the backlight brightness. Digital View LCD controller boards have extensive RS-232 command sets.
• Autonomously: The system can be set up to automatically adjust the backlight brightness, for example using a light sensor.

System Level Design

The following is a brief guide to show how you can use a variable resistor, such as a dial or a slider potentiometer, to adjust the backlight brightness of an LCD panel that uses PWM (Pulse Width Modulation). The usual way to adjust the backlight brightness on a monitor is with +/- type buttons or as part of the on screen menu commands, however a dial or slider can be faster or more intuitive in some installations.

In simple terms this method uses a small analog to PWM adaptor board to convert the voltage from the variable resistor to a PWM signal. The PWM signal is then passed to the LCD panel backlight as usual. Here is an example diagram:

The example is shown using an ALR-1920 but the connection is the same with any Digital View LCD controller board. For a full list of controllers see: https://www.digitalview.com/controllers/lcd-controllers-home.html

For more on LCD panel backlights and brightness see: https://www.digitalview.com/blog/lcd-panels-backlights-brightness/

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