DC Motor RPM Display On Smartphone Using Arduino

The DC Motor RPM Display system relies on a closed-loop arrangement of sensing, processing, and wireless telemetry hardware centered around the Arduino Uno. At the heart of the mechanical sensing setup is a DC motor outfitted with a coded disc encoder that rotates alongside the motor shaft. Positioned relative to this slotted disc is an opto-coupler speed sensor module, specifically the FC-03. As the motor spins, the alternating solid sections and slots of the encoder disc pass through the FC-03's optical slot, interrupting an infrared light beam. This interruption generates a train of digital pulses where the frequency of the pulses is directly proportional to the rotational speed of the motor. The Arduino Uno captures these digital pulses using its general-purpose input/output pins. By utilizing internal timing functions, the microcontroller counts the number of optical interruptions over a fixed time window, translates this pulse count into rotations per minute (RPM), and formats the final mathematical output into a serial data string. To make this data accessible without a tethered computer monitor, the Arduino interfaces with an HC-05 or HC-06 Bluetooth module via its serial UART pins. The Bluetooth module wirelessly transmits the calculated RPM values to a nearby Android smartphone running the Arduino Bluetooth Controller application. Once received by the mobile app, the real-time speed data is displayed directly on the screen, allowing users to remotely monitor the operational performance of the DC motor.