A line following robot is a small mobile robot that can drive along a path marked on the floor, usually a dark line on a light surface. It matters because it shows how robots sense the world, make simple decisions, and control motion without a human steering them. Line followers are often a first robotics project because they combine sensors, motors, programming, and feedback in a clear way.
They are also similar to real systems used in factories, warehouses, and automated vehicles.
Key Facts
- A light or IR sensor measures how much light is reflected from the surface below it.
- A black line reflects less light than a white mat, so the sensor reading is lower on black and higher on white.
- Basic decision rule: both sensors see white = go straight.
- Basic decision rule: left sensor sees black = turn left, right sensor sees black = turn right.
- Wheel speed controls turning: left wheel slower and right wheel faster makes the robot turn left.
- Speed = distance / time, so a robot that travels 120 cm in 6 s has speed = 20 cm/s.
Vocabulary
- Line following robot
- A robot that uses sensors and programmed rules to follow a visible path on a surface.
- IR sensor
- An infrared sensor that sends out invisible light and measures how much light reflects back.
- Threshold
- A cutoff value used to decide whether a sensor reading means black line or white surface.
- Differential drive
- A drive system where two side wheels can spin at different speeds to make the robot move and turn.
- Feedback
- Information from sensors that the robot uses to adjust its behavior while it is moving.
Common Mistakes to Avoid
- Putting the sensors too far in front of the wheels, which is wrong because the robot may detect the curve too early and oversteer.
- Using the same threshold in every room, which is wrong because bright sunlight or dim lighting can change sensor readings.
- Making both wheels turn at the same speed during a turn, which is wrong because a differential drive robot needs unequal wheel speeds to rotate.
- Programming only one sensor condition, which is wrong because the robot must respond differently when the left sensor, right sensor, both sensors, or neither sensor sees the line.
Practice Questions
- 1 A robot travels 90 cm along a line in 5 s. What is its average speed in cm/s?
- 2 An IR sensor gives a reading of 820 on white and 260 on black. Choose a reasonable threshold halfway between them, then state whether a reading of 300 should be classified as black or white.
- 3 A two-sensor robot is drifting to the right side of the black line. Explain which sensor is likely seeing black and how the robot should change its wheel speeds to get back on track.