The line-follower robot is one of the most popular introductory robotics projects, moving automatically along a black (or white) line drawn on a light (or dark) surface, relying only on simple light-reflectance sensors with no camera or complex image processing.
Components needed
An Arduino Uno board, an L298N motor driver module, two geared DC motors with wheels plus a caster wheel, at least two IR reflectance sensors (or more in more precise designs), and a battery pack.
Wiring it up
The reflectance sensors (or more, in finer designs) are mounted at the front underside of the robot, one to the left of the expected line path and one to the right, with each output connecting to its own digital or analog pin. The L298N module connects to digital pins that control each motor's speed and direction.
How it works
A reflectance sensor works on the principle that dark surfaces absorb the light sent out by an infrared LED, while light surfaces reflect it back; the sensor's receiver reads the intensity of reflected light to determine whether it's over the line or off it. The code continuously compares the two sensors' readings: if both sensors are over the line, the robot moves straight forward at a constant speed on both motors; if the right sensor leaves the line (meaning the robot has drifted left off the path), the left motor slows down or briefly stops so the robot turns right and returns to the line, and vice versa when the left sensor leaves the line. This comparison repeats at very high speed, so the robot's motion appears to follow the line smoothly, even though it's really a rapid sequence of small corrections.
You can find IR reflectance sensors, the L298N driver module, and robot motors at Juthour Tech.
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