Text LCD -- RGB Backlight

Now here's a neat-o project, an LCD with an RGB backlight. I picked this guy up from Amazon for not too many bucks. With the red-green-blue elements, you can come up with just about any hue you want via phase-locked pulse width modulation. See the RGB LED project for additional details.

Apart from the aesthetics, this could also be of tremendous benefit in conveying information. For example, a green background might mean edit mode, while a blue background could indicate a run mode. And a red background might suggest an error condition.

The circuit is straightforward, depending upon the ideas developed in previous projects. Port B lines B.2 through B.7 control the LCD proper, while Port A lines A.0 through A.2 manipulate the RGB elements.

On the unit I used, current limiting resistors were already provided, so the collectors of the three 2N2222 transistors simply feed the LED lines directly. You should check to see if your LCD follows the same protocol.

This uses the PMP built-in LCD unit. Note that the display shows the current values of the color mix (from 0 to 15 for each color.)

Click to get the source code.
Click to get the schematic PDF.

Next Project: Graphic LCD

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