Projects / Portfolio
STM32L476RG Integrated Outdoor Safety System
2024 · Course grade 94/100
A wearable device that continuously monitors health and location outdoors and can send a distress signal in an emergency. Data is uploaded to a cloud server over 4G for real-time monitoring.
- Sensors
- 5
- GPS deviation
- <50m
- PCB layers
- 2
- Location history
- 24h
- Course grade
- 94/100
Why I built it
Outdoor activities are increasingly popular, but traditional equipment has limitations: radios depend on signal range, and reading maps takes experience. In an emergency, two things matter: alerting others and identifying the person’s location.
System overview
The device obtains its location via GPS and uploads collected data to a cloud server over 4G. The dashboard can be accessed from a computer or phone.
Monitoring dashboard
The backend runs on an Alibaba Cloud server with Nginx and PHP. Leaflet.js displays the current position and location history. Four panels show GPS coordinates, heart rate and blood oxygen, steps and calories, and temperature and humidity, refreshing once per second. Location records are retained for 24 hours before automatic removal.
Hardware
Five modules are used: MAX30102 for heart rate and blood oxygen, AHT20 for temperature and humidity, MPU6050 for steps and motion, ATGM336H for positioning, and e27v for 4G transmission. Sensors communicate over I²C; GPS and 4G use serial ports. Two stacked PCBs organise the assembly, and all data is output in a common JSON format.
Enclosure design
The enclosure was modelled in SolidWorks with rounded edges and a battery compartment, then 3D-printed and assembled.
Future improvements
Data cannot be uploaded without coverage, so SOS functionality is unavailable in those areas; satellite communication is a possible future addition. The device is relatively large and lacks water and dust protection.
Further improvements include local buffering during outages, a unified I²C sensor interface, and a smaller STM32 minimum-system board.