A Low-Cost Single-Sided Timing System for Automated Performance Measurement in School Physical Education: Design Rationale and Technical Characterization

This study presents the design rationale and a bench-level technical characterization of a low-cost, single-sided Time-of-Flight (ToF) timing system intended for school physical education. The system integrates a ToF distance sensor, an ESP32-C3 microcontroller, Bluetooth Low Energy (BLE) communication, and a web-based user interface to detect passage events, compute elapsed time, and manage measurement records. The contribution lies in the integration of mature commercial components into a configuration matched to class-operation constraints, and not in a new sensing principle: the single-sided configuration removes the alignment step required by two-sided arrangements, and passage detection operates on a distance threshold of 1800 mm, set below the sensor module’s specified maximum range of approximately 2500 mm. Passage detection succeeded in every trial under three illuminance conditions (approximately 300, 1500, and 3000 lux) and three movement conditions, giving a detection rate of 100.0% for each set of 90 trials (exact 95% CI 96.0–100.0%); no false detections occurred during 30 min of no-passage monitoring per illuminance condition or during a further 8 h of continuous unattended monitoring. Across 30 shuttle trials, the mean difference from a 240 fps video reference was +0.008 s (95% CI −0.001 to +0.017 s), with 95% limits of agreement of −0.038 s and +0.055 s. All 300 BLE test events were received over a 10 m line-of-sight link, and total hardware cost was approximately USD 20. The observed timing variability was dominated by the sensor’s ranging period of approximately 50 ms. All trials were conducted indoors by a single operator on a same-line shuttle task, and end-to-end latency, the effect of the threshold on the trigger instant, and performance across users were not measured; these results therefore do not establish measurement performance in classroom use.