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GeocaSCH - Smart Geocache with GPS and Camera GeocaSCH - Smart Geocache with GPS and Camera

GeocaSCH - Smart Geocache with GPS and Camera

21 May 2023

Overview

GeocaSCH is a geocache that adds an optional photo and a cloud-based logbook to the classic geocaching experience. The idea is that finders don’t just sign the log, they can capture the moment too. The hardware has to stay reliable outdoors in any weather, while the software written by my friend Péter Mikulás takes care of robustness and thorough logging.

Technical implementation

Hardware design

  • Weatherproof build:
    • 3D-printed PETG enclosure: printed from 800 grams of plastic, optimized for mechanical load and impact resistance.
    • Water resistance (two layers of protection): an airtight electronics compartment with a plexiglass cover and a drip-proof design. The box as a whole is sealed by an IKEA food container lid.
    • Magnetic solar panel connector: easy maintenance and a watertight connection.
    • Brass threaded inserts and precision pin sockets: long-term mechanical stability.
  • Power management:
    • Solar power supply: self-sufficient power for long-term operation.
    • Custom PCB: an optimized circuit for driving the modules at low power.
    • Standby mode: only 278 µA in deep sleep (~1 year of runtime without charging!).
  • Communication and sensors:
    • ESP32-S3 microcontroller: I²C, UART, SCCB and DVP interfaces for the camera, the GNSS and the other modules.
    • GNSS positioning: keeps track of where the device is.
    • 4G/LTE connectivity: uploads images and telemetry to the server.

Software architecture

  • Firmware: written with the Arduino framework, using ESP32-S3 specific features (PSRAM, deep sleep).
  • Image handling:
    • Hardware JPEG compression: smaller images to keep 4G data usage down.
    • PSRAM buffering: images are stored temporarily in PSRAM to take load off the RAM.
  • Diagnostics:
    • Status shown on a loading screen while the modules initialize.
    • Error logging through the web admin interface.

Key features

  • Taking photos: images up to 5 MP, with the user’s consent.
  • Self-sufficient power: solar charging and ultra-low-power electronics.
  • Built for the outdoors: PETG enclosure, water- and impact-resistant design.
  • Web admin interface: image moderation, telemetry analysis and device status monitoring.

Technologies

  • Microcontroller: ESP32-S3
  • 4G/LTE GNSS module: SIMCOM SIM7080G
  • Battery chemistry: LiFePO4
  • Other modules: OV5640 camera, OLED display, SHT40 temperature and humidity sensor, LIS3DH accelerometer
  • PCB design: custom circuit for dual-input charging, battery protection and module control.
  • 3D printing: PETG and TPU, with heat-set threaded inserts
  • Communication: LTE, (GNSS), I²C, UART.
  • Data processing: hardware JPEG compression, PSRAM.
  • Cloud infrastructure: a custom admin panel built with PHP (phpMyAdmin), a MariaDB database and an Apache2 web server.
  • CAD tools: EasyEDA (PCB design), Fusion 360 (3D modeling), Cura (3D printing).

Results

  • First place at BME Kütyüpályázat 2023, a gadget competition at BME
  • 278 µA deep sleep consumption
  • ~150 mA active consumption
  • 1 year of standby runtime without solar charging.
  • 3.7 MP default image resolution, optionally up to 5 MP.
  • Automatic upload to the web interface over 4G.
  • Demo video
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