After observing my son’s interest in the glowy buttons on my Rigol DS1102E, I decided to design an interactive toy for him utilizing that type of button.

SparkFun sells 2 x 2 and 4 x 4 translucent silicone button pads that accommodate a standard 5 mm through-hole LED.  Adafruit now sells a smaller dimension 4 x 4 button pad, but it can only accommodate 3 mm LEDs.  I’m not aware of any RGB LEDs that come in that package size, but I may see how well it works with surface-mount RGB LEDs in a future project.

My requirements are:

• 4 x 4 translucent button pad
• 5 mm through-hole diffused lens RGB LEDs
• N-key rollover to prevent jamming and ghosting
• Arduino compatible micro-controller for easy programming
• AA battery powered
• DC boost circuit to extend useful battery life, inspired by projects like Ray’s AA Saver
• Individual on/off control of LEDs through shift registers or LED drivers
• Single 2-layer PCB
• Buzzer capable of playing musical notes spanning a few octaves