Inconspicuous LED Graduation Hat
I'm graduating from high school on Saturday (6/18), but was dissapointed when they didn't allow anyone to decorate their graduation caps. So, I decided to take a creative and semi-invisble approach to this - infrared LEDs!
Infrared LEDs emit infrared light, which can not be seen by the human eye, but shows up decently on a video camera. By putting IR leds in my graduation cap, nobody in person would be able to tell, but when i walk across the stage the cameras will capture it - blinking out, through morse code, "Congratulations class of 2011!"
I managed to make all of this the night before graduation, so escuse the messyness!
An ATmega168 in dead-bug style controls the whole thing. A single sell lithium polymer battery provides the power - it's an unregulated 4.2 volts, not ideal but it was lightweight, flat, and worked well enough.
I coded the mega168 in Arduino. The beauty of it is that it took me about 1 minute to code the thing. I downloaded the morse library, and changed the example sketch to blink out my phrase. That's it, done. Load atmega168 into an arduino board, press upload, and it's in!
One problem I encountered was that in dead-bug format, the atmega should use its internal oscillator at 8mhz instead of an external crystal. To fix this, I hooked up my AVR ISP MKII programmer and used AVR Studio 4 to change the fuses to make the mega use its internal oscillator.
After that, it was a simple job of wiring up the LEDs and putting them in the hat. Build photos below!