An RGB LED is a LED which has three LED's integrated in one packaging. These LED's has the colors red, green, and blue. Such a LED costs about 1 Euro. With these three colors you can mix to any color. When using 8-bit PWM a number of 256 * 256 * 256 combinations can be made, thus the LED can show 16.777 million colors, and 256 different brightness. When all the three LED is at full brightness the color will be white. When they are all off the color will be 'black' in the dark.
The RGB LED used here has four leads, one for each color an one for the common cathode (ground). The Red LED operates on a voltage of 2 V, Green needs 3.5 V, and the Blue LED needs also 3.5 V. Each LED draws 20mA current, so the maximum current consumption is 60mA. This is the figure of the circuit.
The circuit is very simple. The RGB LED is hooked up to the PWM outputs on PORTB1, PORTB2 and PORTB3 of the ATMega8. There is also a resistor between the LED and the ATM8 to limit the current to 20mA. There is also a link to the datasheet of the RGB LED that is used in this project.
