Presence detection for personal safety devices

Abstract

A device includes a circuit for receiving power from a power supply of a personal safety device and at least one control circuit powered by the circuit. In a calibration mode, the control circuit receives a signal from an ambient light sensor and establishes a baseline ambient light level based on this signal. In a presence detection mode, the control circuit receives another signal from the ambient light sensor, compares this signal to the baseline ambient light level, analyzes it to determine that a difference in ambient light compared to the baseline ambient light level indicates the presence of an object near the personal safety device, and issues a warning indicating, at least partially, the presence of the object near the personal safety device based on this analysis.