This article is brought to you by MonkeyLectric and the Monkey Light bike light
Step 1: The circuit board
I've attached below the Eagle CAD (http://www.cadsoft.de/) files for the circuit board, the C source code for the microcontroller, and the Gerber files of the circuit board to get it manufactured. Eagle CAD is free for small-size boards like this one.
Atmel mega8L microcontroller - digikey ATMEGA8L-8AC-ND
6-pin .1" spacing pid header - digikey WM6806-ND
1206-size surface mount LED's in color of your choice - digikey 160-1406-1-ND, 160-1404-1-ND, 160-1402-1-ND
150 ohm resistor array: digikey EXB-V8V150JV
10uF 0805 size capacitor: digikey 587-1299-1-ND
switch: digikey CKN4081CT-ND
lithium-ion battery: from batteriesamerica.com (http://www.batteriesamerica.com/newpage8.htm)
Step 2: Programming the microcontroller
The C code supplied does not include on/off button functionality, this should not be hard to add. you could also add a battery-voltage tester to sense when the battery is dead (this is important for lithium-ion, they are permanently damaged by discharging too much). to make a battery-voltage tester, you could (i think!) use a 3.0V zener diode and 220k resistor across the battery, and use the a-to-d converter on the mega8 to compare when the battery voltage falls below the zener reference voltage.
Step 4: Do some dancing!
how well does this device work? it is a bit hard to notice at walking speed, mostly because if you look straight at it the effect is reduced. if you look away at a fixed object it is much clearer. at running speed or dancing it works nicely.
Step 5: Buy a kit