Smart Buoy
The smart buoy floats at the surface, serving as the communications relay between the submerged unit and the base station.
Core Hardware
Section titled “Core Hardware”Module: Heltec Wireless Tracker v1.1
- MCU: ESP32-S3 (dual-core 240MHz, 512KB SRAM, 8MB flash)
- LoRa: Semtech SX1262 (150MHz–960MHz, up to +22dBm TX)
- GNSS: Quectel L76K (GPS + BeiDou, L1/L5 dual-frequency)
- Display: 0.96” OLED (status display, optional)
LoRa Configuration
Section titled “LoRa Configuration”| Parameter | Value |
|---|---|
| Frequency | 915 MHz (US) / 868 MHz (EU) |
| Bandwidth | 125 kHz |
| Spreading Factor | SF10 (balanced range/throughput) |
| Coding Rate | 4/8 |
| TX Power | +20 dBm |
| Effective Range | 3–8 miles (line of sight over water) |
- Constellation: GPS + BeiDou (dual-system for reliability)
- Frequency: L1 + L5 (dual-frequency for sub-meter accuracy)
- Cold start: ~30 seconds
- Hot start: ~1 second
- Fix logged: Every telemetry transmission, stored in NVS for drift detection
Power System
Section titled “Power System”- 5V 1W mini solar panel (80×55mm)
- Charge controller integrated on the Heltec board
- Effective charging: 4–6 hours of direct sunlight per day
Wave Energy (Future Phase)
Section titled “Wave Energy (Future Phase)”- Linear electromagnetic generator driven by wave motion
- Target output: 50mW average in moderate seas
- Supplements solar for overcast/nighttime operation
Tether Power (PoE)
Section titled “Tether Power (PoE)”- MT3608 boost converter steps battery voltage (3.7V) up to 24V for the tether
- Current-limited to 150mA (3.6W max) to protect the cable and submerged unit
- The higher voltage reduces I2R losses over 10-20m cable by ~25x compared to direct 5V
- Power is cut automatically at the 10% battery threshold to preserve buoy operation
Battery
Section titled “Battery”- 3.7V 2000mAh LiPo
- Runtime without solar: ~7 days at 15-minute telemetry intervals
- Sleep current: 15µA (GNSS off, LoRa standby)
Power Budget
Section titled “Power Budget”| State | Current Draw | Duration |
|---|---|---|
| Deep sleep | 15µA | Between events |
| GNSS fix | 25mA | ~1–30s per fix |
| LoRa TX | 120mA | ~100ms per packet |
| LoRa RX window | 12mA | 500ms after TX |
| Tether power (24V boost) | 0–150mA | On demand |
Buoy Enclosure
Section titled “Buoy Enclosure”- Material: UV-stabilized HDPE
- Seal: O-ring compression seal, IP68
- Antenna: External SMA whip antenna (LoRa) + patch antenna (GNSS)
- Indicator: Single RGB LED visible through translucent top cap
- Green pulse: normal operation
- Blue pulse: transmitting
- Red pulse: alert condition
- Off: sleep mode