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LG Band: Wearable GPS Tracker
A battery-powered wearable GPS tracker with SOS alerts, redesigned for low power, small size and lower cost, and deployed in the field.
- Company
- Drishti Works, Mumbai
- Period
- May 2026 – present
- Role
- Hardware & firmware
- Platform
- ESP32 + LTE-M/GNSS modem
Overview
The LG Band is a battery-powered wearable GPS tracker with an SOS button, built for emergencies. It runs on an ESP32 with an LTE-M/NB-IoT and GNSS modem, and reports positions to the cloud over MQTT. I own both the hardware and the firmware.
Hardware
- Smaller board, same features. Redesigned the hardware from 40 × 49 mm to 34 × 34 mm (about 41% less area), packaged in a smartwatch-sized 40 × 37 × 8 mm device, while keeping every existing feature and adding new ones critical for an emergency tracker.
- 30% lower cost per board through BOM optimization and careful component selection.
- GNSS antenna evaluation. Designed evaluation boards to benchmark several antennas and select the best fit for the device.
Battery life
Battery life went from about 15 hours to more than 24 hours, using a battery half the size, through the hardware redesign combined with firmware power optimization.
Firmware
- Low power: ESP32 deep sleep, modem sleep via DTR, CPU scaling when needed, and a low-battery cut-off that prevents brownout reset loops.
- Positioning: AGPS-assisted multi-constellation GNSS (GPS, GLONASS, Galileo) with HDOP-weighted position averaging for faster, more accurate fixes.
- Reliable data: batched MQTT publishing with retry-until-confirmed delivery, dual-slot checksummed EEPROM backup for power-loss recovery, and automatic recovery from modem reboots.
- Updates and safety: secure HTTPS OTA updates with SHA-256 verification and automatic rollback, and a priority SOS alert path.
In the field
Deployed 40+ devices with an 88%+ success rate, leading a small embedded team on site for deployment management and device servicing.