Build a Robot Car with Speed Sensors using Arduino Interrupts

This project integrates a mechanical robot car chassis with microcontroller electronics to achieve precise motion tracking. The physical build starts with an acrylic base housing two DC motors, wheels, a rear castor, and special encoder wheels that feature alternating slots. These encoder wheels spin alongside an H206 opto interrupter sensor module, which contains an infrared transmitter and receiver. As the encoder wheel rotates, its slots repeatedly break and complete the infrared light beam, generating a pulsed electrical signal. This signal is processed by an onboard LM393 comparator module to create clean digital square waves that the Arduino board can read. Because speed calculation requires capturing every single pulse without missing a beat, the Arduino uses hardware interrupts to instantly pause its main program loop whenever a pulse transition is detected, ensuring highly accurate counts. Power and movement are coordinated using an L298N motor driver, which takes low-current control signals from the Arduino and supplies the higher current needed to drive the DC motors from a separate battery holder. By programming this setup through the Arduino IDE, makers can command the motors while simultaneously counting the interrupt pulses to measure wheel rotation, track distance, and calculate real-time speed.