Light Bot

Materials list
1) Cerebellum dev board (1)
2) Photo Resistors (2)
3) Resistors (2) - Value should be about the same as your photo resistors at ambient light (1K is good)
4) Servos (2) - Modify to be continuous rotation
5) Robot frame - Either buy one or make something

Design details
You might want to visit my previous tutorial to see how get the Cerebellum dev board working. You also need to get my C project for the CSS compiler even if you'll be using a different compiler or assembly because the comments contain valuable information.

The way the photo resistor sensors are hooked up is a voltage divider using the standard resistors. To do this you put bot resistors in parallel and hook up power and ground. Then you put an analog to digital pin from the micro controller between the standard and photo resistors. The only real problem I ran into was I tried to use the same battery pack as power source for the servos and the micro controller. This resulted in the micro controller rebooting every time the servos changed direction. The fix was to add another battery pack to supply power to just the servos. Other than this minor glitch I had no problems.

Overall this robot was a good first robot because it taught me a lot, but quite frankly only having photo resistors for sensors sucks. I wanted this robot to seek out a light source but because of ambient light in a room most of the time there isn't much of a difference between dark and light areas. Sure if there is a shadow this robot avoids it, but otherwise it just jitters around in a random pattern in the room often getting stuck on chairs and walls.

Here are some pictures: Pic 0, Pic 1, Pic 2, Pic 3

Please email any questions/comments/errors to