When new users embark upon the grand learning experience that is physical computing by way of Arduino, they will at some point run Blink. Blink is a simple program designed to show you that your board is working and that you now have the capability to control the world.... Or at least small parts of it.
Normally, people only watch for the on board light but I figured... "Hey why not something bigger?" I figured that if I was going to be presenting topics in physical computing that I would want to run this simple demo... but with one twist.
I'd use a full on real light bulb instead of a tiny LED.
And that's why I made this. http://welcometochrisworld.com/2009/04/16/blink-on-steroids/
It's pretty much the solenoid circuit from the playground but instead of a solenoid I used an automotive relay. And it hasn't caught fire yet.