Bike Buddy

Best ECE Project at the Fall 2025 Capstone Expo. A low-cost attachment that gives an ordinary bicycle the maintenance telemetry of a connected e-bike, from one Hall sensor, a magnet ring and a force sensor on the brake.

I owned the wheel subsystem. Sixteen magnets sit on an acrylic ring with alternating poles, so a single Hall-effect sensor on the fork sees a crest and a trough for every magnet. Position, speed and lateral wobble all come out of that one signal, with no IMU. On the ESP32-S3, core 0 samples the sensors and keeps their moving averages on a 1 ms period, while core 1 runs the filtering, the classifier and the BLE link, so radio traffic can never delay a sample. On core 1, a look-ahead steady-state velocity estimate sets the window of a bandpass filter that separates wobble from real changes in speed, and a weighted decision tree written as a finite state machine labels each window as braking, pedaling or noise with bounded memory and stack. A force sensor on the brake lever gives a brake-health metric from the fit of brake force against deceleration. The finished unit weighs about two pounds and costs roughly $35 in parts.