TreeGuard — Open-Source Tree Protection with Soil Sensor + L

Story

The problem

Millions of saplings die every year — not from disease, but from inconsistent watering in their first two summers. Municipal irrigation is expensive and doesn't scale. Volunteer watering programs lose momentum after planting day.

The solution

TreeGuard is a small, cheap, solar-powered device that wraps around a young tree. A capacitive soil moisture sensor monitors root-zone humidity. When the soil drops below a species-specific threshold:

• Red slow pulse: the tree is thirsty — please pour ~1 liter of water
• Green breath: just watered, no more needed (auto-off after ~2 hours)
• Amber double-blink: battery low or sensor fault, needs maintenance

An 18-hour post-water lockout prevents overwatering when multiple people help throughout the day. LEDs suppress at night to avoid light pollution and wildlife disturbance.

Hardware

The device uses either an ESP32-C3 Super Mini (connected version with WiFi/BLE) or an ATtiny1614 (offline MVP, LED-only). Power comes from a 5V solar panel, TP4056 charge controller, and a reused 18650 Li-ion cell.

The frame is 3D-printed in PETG (not PLA — PLA fails outdoors). It uses a triangular hex-segment design, ground-staked so it never attaches to the tree trunk. Security Torx fasteners discourage tampering.

Full BOM: ~$11-14 per unit.

Key design decisions

• Capacitive sensor, not resistive — resistive probes corrode in weeks outdoors
• PETG filament, not PLA — PLA degrades under UV and cold; PETG survives outdoor conditions
• Solar + reused 18650 — no battery replacements, partners with e-waste recyclers
• 18-hour post-water lockout — prevents overwatering when multiple people help throughout the day
• Security Torx fasteners — nothing worth stealing, but discourages casual vandalism
• Ground stakes, never trunk-mounted — frame protects the tree without constraining its growth

Two firmware variants

• TreeGuard Mini — ATtiny1614, offline, LED-only, lowest cost and complexity
• TreeGuard Net — ESP32-C3, WiFi/BLE, OTA firmware updates, data logging to a PWA

Current status and what we need

The full design — firmware, schematics, BOM, 3D models, and documentation — is complete and open-source. We are at the pre-prototype stage and looking for contributors to:

• Fabricate the PCB and assemble the first physical unit
• 3D print and test the PETG frame outdoors
• Deploy on a real sapling and collect data
• Review firmware and hardware design
• Contribute species-specific moisture presets for local trees

This is a real open-source project (CERN-OHL-S v2 hardware, MIT software, CC BY-SA docs), not a class assignment. The goal is community-deployed tree protection at scale.

Get involved

• GitHub: https://github.com/commons-lab1/treeguard
• Open a Discussion or Issue on the repo
• Full BOM: https://github.com/commons-lab1/treeguard/blob/main/hardware/bom.csv

Components

• ESP32-C3 Super Mini (or ATtiny1614)
• Capacitive Soil Moisture Sensor v2.0
• 5V 0.5-1W Solar Panel (epoxy encapsulated)
• TP4056 + Protection Board (HW-107)
• 18650 Li-ion Cell (reused)
• WS2812B or 5mm Diffused LEDs (red + green)
• PETG Filament (~250g)
• M3 Brass Heat-Set Inserts + Security Torx Screws
• JST PH 2.0 Connectors