Edit: I've noticed a lot of people are hating on the excessive control used in this project so I just wanted to clarify a few things:
1. This instructable was also meant to be a lite introduction to actual AVR programming for those people who are used to only Arduino programming. I had a bit of trouble finding useful information when I was learning so I figured it would be nice to help out some others. That is why I posted the basic tutorials along with my AVR code.
2. Yes I'm aware I could have simply used a reed switch to switch the LEDs when the door opened and closed. I wanted to leave room open for myself to add different light modes, maybe using more wires and pins to create nice fading effects, possibly a remote control sensor, and maybe even an auto-shutoff routine.
Step 1: Gather materials
The usual tools:
1. Soldering Iron/Solder
2. Electrical tape
1. Hall Effect Sensor-(one used can be found here: http://www.sparkfun.com/commerce/product_info.php?products_id=9312
2. Attiny85-(any micro can be used, mainly just for quick and easy digital input readings)
3. Led's of any color
4. Cases for the lights,
5. Wire and Wall wart
6. Resistors (1k and 3x33Ohm used in mine)
Note: A microcontroller isn't necessary for this to work. If you can get the sensor to successfully switch a transistor to saturation, you should be able to skip the whole controller and coding part.