Join Date: Sep 2005
Bikes: Windsor Fens, Giant Seek 0 (2014, Alfine 8 + discs)
I don't know what your level of electronics tinkering is, you probably already know thist, but just in case, you are going to need driver transistors, or better yet MOSFETs, to drive more than a couple of LEDs off an Arduino/atmel CPU.
I normally just use the chip itself, not a full arduino board, since I'm going to have to add circuitry anyway and piggybacking a whole arduino, even one of the little ones, just takes up more space when all you need is the chip itself.
Work: the 8 hours that separates bike rides.