ESP32 Soil Monitoring

This guide will walk you through building a low-power ESP32-based soil monitor using a Soil sensor. The device uses deep sleep mode to conserve power, waking up at set intervals to collect a soil moister data and send it to your Telemetry Harbor instance for visualization and analysis.

Repo Link: https://github.com/TelemetryHarbor/harbor-esp32-soil-sensor

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Overview

This project wakes up periodically, reads soil moisture percentage from the 2-prong sensor, sends it to Telemetry Harbor, and returns to deep sleep for ultra-low-power operation. Ideal for gardens, potted plants, and soil monitoring projects.

Features

• Ultra-Low Power: Uses ESP32 Deep Sleep mode to extend battery life.
• 2-Prong Soil Sensor Support: Accurate analog readings from standard 2-prong sensors.
• Cloud Connectivity: Sends readings to Telemetry Harbor using the official SDK.
• Timestamped Data: Each reading is recorded with an ISO8601 UTC timestamp.
• Grafana Dashboards: Ready for visualization with Telemetry Harbor.

Hardware Requirements

Component	Description	Approximate Cost
ESP32	Development board (NodeMCU ESP32, WROOM, etc.)	$3.82 (AliExpress) / $9.90 (Amazon US)
2-Prong Soil Sensor	Capacitive or resistive soil moisture probe	$1.50–$3.00
Jumper wires	For connecting sensor	$0.42 (AliExpress) / $5.49 (Amazon US)
Micro USB cable	For power & programming	$3.00 (AliExpress) / $5.00 (Amazon US)
Battery (optional)	For standalone, low-power operation	Cost varies

Software Requirements

• Arduino IDE (1.8.13 or newer) or PlatformIO

• ESP32 board support package

• Required libraries:

  • Telemetry Harbor SDK
  • WiFi Library (built into ESP32 core)

• Telemetry Harbor account

Wiring Diagram

Connect the 2-prong soil sensor to the ESP32:

Soil Sensor Pin	ESP32 Pin	Function
VCC	3.3V	Power
GND	GND	Ground
Signal / Output	GPIO 34	Analog input

Notes:

• Ensure both sensor prongs share a common ground with ESP32.
• Capacitive sensors are recommended for long-term use; resistive sensors may corrode over time.
• Analog values can be noisy; consider averaging multiple readings.

Setup Instructions

1. Hardware Assembly

1. Connect the 2-prong soil sensor to the ESP32 according to the wiring diagram.
2. Connect the ESP32 to your computer via USB.

2. Software Setup

1. Install Arduino IDE.

2. Add ESP32 board support:

   • Preferences → Additional Boards Manager URLs:

     https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json

3. Install required libraries via Library Manager:

   • Telemetry Harbor SDK
   • WiFi Library (built-in)

3. Telemetry Harbor Configuration

1. Create a Telemetry Harbor account.
2. Create a new Harbor called "ESP32_Soil_Monitor" (or your preferred name).
3. Copy the API ENDPOINT and API Key from the Harbor details page.

4. Configure and Upload the Code

1. Open your soil sensor .ino file in Arduino IDE.

2. Update the following variables at the top of the file:

   • WiFi SSID and password
   • Telemetry Harbor API Endpoint URL and API Key
   • shipId (e.g., "Garden 1")

3. Select your ESP32 board and COM port.

4. Upload the code.

5. Visualize Your Data

1. Log in to your Telemetry Harbor account.
2. Navigate to the Harbor details page and Grafana dashboard.
3. Monitor soil moisture in real time and over time.

Customization

Sleep Interval

Change how often the ESP32 wakes up:

const int SLEEP_INTERVAL_SEC = 300; // 5 minutes

Sensor Calibration

Adjust offset for more accurate readings:

const float SOIL_OFFSET = 0.0; // +/- percentage for calibration

Debug Mode

Add Serial prints for testing:

Serial.printf("Raw ADC: %d, Moisture: %.2f%%\n", raw, moisture);

Disable deep sleep during debugging to view Serial output.

Troubleshooting

• Sensor gives constant values: Verify wiring, common ground, and analog output.
• WiFi connection fails: Check credentials; device retries on next wake cycle.
• Data not appearing in Telemetry Harbor: Verify API Key and Endpoint URL.