How to Adjust the Contrast of a HD44780 LCD

The contrast of the screen of the HD44780 LCD can be adjusted to make the screen brighter or darker.

The contrast pin of the HD44780 is pin 3, as shown below:

To allow for adjustable contrast, connect a 10KΩ from pin 3 to ground.

This is the full schematic of the HD44780 LCD wired up:

With the 10KΩ potentiometer, you can vary the contrast from dark to bright. When the potentiometer is near 0Ω, the screen will be very dark. As you turn the potentiometer up to 10KΩ, the screen will become brighter.

This is how contrast of a HD44780 LCD screen can be achieved.