Robot Line Tracker
Builder: Jan MalasekThis was my first robot, which followed a 2-inch white line on a black background. I made the chassis from a few rectangles of plywood. The motors came from an Edmund Scientific catalog, and the wheels came off of a broken radio control toy. They kept coming off of the robot, too!
The ball caster was originally a ping-pong ball in a toilet paper tube. I was very happy to get my hands on the metal ball caster (out of a Harbor Freight catalog) since I was generally limited to a local Ace Hardware store and a Radio Shack 40 miles away, where I got most of the electronics components.
I used three pairs of infrared LEDs and phototransistors for the sensors. I didn't know about programming or microcontrollers, so the electronics consisted of some inverters and a few transistors and relays to control the motors (forward only, no speed control).
The extra board on the front of the robot was for a counter circuit that used the middle sensor to count small black lines across the line (about 1/8" wide). The idea was that bar codes could be integrated in the lines the robot followed to provide information about upcoming line conditions (such as intersections). The counter did show how many little black lines were crossed, but I did not get to the point of having the robot do anything in response to the count.
Jan's Robot Line Tracker
The bottom view shows the ball caster and three LED/phototransistor pairs.
Here we see the main PCB, nicely labeled!
The red rectangle on the bottom of the "bar code reader" is a single-digit display that shows how many lines were crossed.
