HerShield — Intelligent Emergency Response & Personal Safety Hardware
Discreet IoT wearable integrating cellular telemetry, GPS tracking, and silent distress state-machines
An embedded personal safety device engineered for ultra-reliable emergency alerting, geo-coordinate transmission, and silent trigger verification under low-power hardware constraints.
The Fundamental Engineering Problem
Mobile safety apps frequently fail in critical moments due to locked phone screens, drained smartphone batteries, or the inability of a user in danger to overtly retrieve a phone.
Critical Engineering Constraints:
Wearable safety devices cannot rely on bulky batteries. The microcontroller and cellular module must remain in sub-10μA deep sleep until a mechanical emergency trigger wakes the system.
Accidental button presses in bags or pockets must be filtered out without creating a cumbersome multi-step activation that compromises emergency usability.
Acquiring satellite lock from cold start can take over 45 seconds in urban canyons. Hardware assisted-GPS (A-GPS) and cell-tower triangulation fallbacks are vital.
Hardware & Telemetry Architecture
Designed a dedicated embedded wearable system with tactile multi-tap validation logic to prevent false alarms, immediate GPS triangulation, and cellular SMS/GPRS telemetry bursts to emergency response circles.
My Specific Contribution to this System
Architected the micro-firmware state machine in C++, managed power-saving sleep modes, and implemented cellular AT command handshake routines.
Profiled standby and burst current consumption of various cellular modules, selecting an optimized low-power modem architecture.
Programmed an embedded C++ state machine implementing a cadence verification algorithm (e.g. 3 rapid pulses within 2.5 seconds) to confirm valid distress events.
Implemented lightweight circular buffer serial parsing to extract latitude, longitude, and speed from raw NMEA `$GPGGA` sentences without dynamic memory allocation.
Configured emergency SMS and HTTP endpoint dispatch transmitting precise Google Maps links to designated contacts within 3 seconds of activation.
Empirical Findings & Registered Outcomes
- Successful bench prototype demonstration with verified GPS coordinate transmission over GSM/LTE.
- Emergency sequence confirmation achieved in < 3 seconds from initial physical trigger.
- Standby power consumption minimized to achieve multi-day deployment readiness on a compact 400mAh LiPo cell.
- •Dependent on cellular network coverage; in deep subterranean areas or remote wilderness without GSM reception, SMS alerts queue until network connection restores.
- •GPS fix indoors can degrade accuracy, requiring fallback to coarse cell-tower ID approximations.
- •Integration of Bluetooth Low Energy (BLE) beaconing for dense indoor micro-location tracking.
- •Custom miniaturized 4-layer PCB design replacing prototype perfboard wiring.
- •Development of an intuitive mobile dashboard for emergency circle management.