This robot is also in the Robot Contest for the age 12-18 category.
In this instructable I will write out the basic ideas which I used to make a wall following robot without any microcontroller. The robot in these instructions was originally used in the Trinity Firefighting contest , and was supposed to be the first robot (that I know of) to compete without a microcontroller. However it did not successfully blow out the candle.
Recently, my friend informed me of the 555 contest and encouraged me to enter the robot. However, I do not have time to remake the robot frame and whatnot, so I will give this instructable using the original frame with the firefighting parts removed. Also, I used some specific parts in this build like Vex motors, and I haven't tested if one can substitute in other continuous rotation servos and have the same effect. As a result of all this, I will not tell you how to replicate my robot, but instead give the ideas (and circuit) that its based on and leave it to you to determine the frame and parts to use in your build.
Also, this is my first instructable. I will update it or redo it with proper instructions if I have time later maybe.