Display the color combinations of color LEDs without using a microprocessor.
Using a single logic chip which costs under 50-cents, you can make a simple color cycle display for RGB LEDs. The multiple taps along the top are used to 'program' the display for sequence and brightness.
Step 1: The parts
RGB LED - I used one purchased here. This is a common anode version, so if you have a different configuration, you must adjust the connections.
1 x 74HC04 Hex Inverter IC chip (p/n 771-74HC04N, by NXP is 30-cents at Mouser)
3 x 0.1uF capacitors
R1 - 10M-ohm resistor
R2 - 6.8M-ohm
R3 - 3.3M-ohm
R - 12 pcs of 100-ohm resistor for the Programming tree. I used 120-ohm resistors which I got free.
2 x "AA" batteries and suitable holder.
Perfboard, wire, supplies, etc.
I've also used sockets for the IC and the LED, which I've found to be quite sensitive to heat.