Integrated Multi-Sensor Device for Police Firearm Real-Time Monitoring

Police firearm use is complex and potentially life-threatening. Real-time monitoring enhances operational effectiveness, officer safety, accountability, and force auditing. However, firearm mechanics and user interactions are intricate, and integrating sensors may face practical and legal constraints. This paper presents a non-invasive solution that combines a photoelectric infrared sensor with a piezoelectric vibration sensor to detect key events in semiautomatic firearm use, including firing, reloading, impacts, and possible malfunctions, while also tracking the number of remaining rounds in the magazine. The sensors are designed as single transducers, integrated electrically and mechanically into a small, portable, easy-to-install, and ergonomic device. A preprocessing algorithm and state machine optimize signal detection, while noise reduction and linearization techniques enhance the photoelectric sensor signal. Experimental data demonstrate that fusing the temporal signals from both sensors provides an effective method to identify the mechanical behavior of the firearm and indicates promising robustness under typical operational conditions. Power consumption analysis validates the low-power design, supporting battery life between annual officer trainings. The proposed design offers a low-cost, low-power solution that enables public administrations to effectively monitor and record firearm use, while also serving as a tool to enhance officer safety.