A line-following robot for the classroom
The cheapest robot that teaches a full control loop. Under a hundred euros, no soldering required, and every part below is picked from current stock.
BeginnerTarget budget €90.00From €28.98 with the cheapest option at every step
1.Reflectance sensor array
Five to eight infrared emitter and phototransistor pairs in a row. More sensors give a finer position estimate, which lets the controller anticipate a curve rather than react to it. Three sensors is enough to follow a line and not enough to follow it smoothly.
Assembly
- Mount the array between 3 and 8 mm above the floor, which is the range most of these parts are characterised for.
- Calibrate on the actual tape and the actual floor before every session, since ambient light changes the readings.
- Compute a weighted average of the sensor values to get a continuous line position instead of a discrete one.
2.Chassis and gear motors
Two driven wheels and a caster. Gear ratio matters more than motor power here: a fast robot overshoots every curve and teaches the class that control loops do not work.
3.Motor driver
A dual H-bridge rated above the stall current of both motors together. On a robot this size the stall current is what flows every time a wheel hits the edge of the track.
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4.Controller and battery
Any microcontroller with enough analogue inputs for the array and two PWM outputs. Keep the motor supply separate from the logic supply, or the brownout at motor start will reset the controller mid-lap.
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