First and foremost I needed some LEDs. Of course the natural place to start looking was eBay. I found two lots of 100 5mm 7000 mcd auctions. 7000 mcd was the right balance of price and power. It is possible to find some that are a bit more powerful, but for this application 7000 mcd works best. The voltage requirements on these was great too, just right to put 3 in series with a small resistor (more on this later). The 5mm size is the right size for the application as well.

[TODO Picture of LED]

Now all these pretty LEDs don’t do anyone any good if you can’t make them light up. Of course I have a power source (car battery), but I also needed some circuit to make the LEDs flash in a nice warning pattern.

Time for design!