Low-power ESP32-based soil and environmental monitoring firmware built with ESPHome.
Designed for battery or solar-powered operation with intelligent sleep cycles and Home Assistant telemetry integration.
This project measures and reports environmental conditions using a Sensirion SHT31 sensor.
It includes advanced power management through ADC-based voltage monitoring and adaptive sleep scheduling.
Key features:
- Temperature and humidity sensing via SHT31 (I²C)
- Battery and 5 V input voltage measurement using ADC
- Battery percentage estimation with nonlinear calibration
- Automatic day/night deep sleep control
- Home Assistant event logging for voltage and sleep cycles
- OTA updates and encrypted API communication
| Component | Pin(s) | Function |
|---|---|---|
| SHT31 Sensor | 21 / 22 | I²C SDA / SCL |
| Battery Voltage | 32 | ADC input (LiPo) |
| 5 V Sense | 36 | ADC input (USB) |
| Wake-up Trigger | 39 | Deep sleep wake-up |
Board: ESP32 Devkit
Framework: Arduino
CPU Frequency: 80 MHz
The firmware uses deep sleep to conserve energy.
Wake periods last about 1 minute, allowing sensor readings and network updates before returning to sleep.
- Daytime sleep: 10 minutes
- Nighttime sleep: 8 hours
- Automatically decides based on Home Assistant’s reported time
- Sends a telemetry event (
esphome.battery_sleep) with:- Reason (
dayornight) - Duration
- Battery voltage
- Timestamp
- Reason (
When external 5 V power is lost, the device enters deep sleep immediately to protect the battery.
- SHT31 provides temperature and humidity readings.
- ADC inputs measure:
- 5 V presence
- Battery voltage
- Battery percentage is calculated using a nonlinear curve approximating LiPo discharge behavior.
- Readings are smoothed using a sliding average to minimize noise.
- Static Wi-Fi configuration with fallback AP for recovery
- Encrypted ESPHome API for Home Assistant integration
- OTA updates enabled with password protection
- Real-time logging via the ESPHome
loggercomponent (debug level)
The device integrates directly with Home Assistant through the native ESPHome API.
It exposes:
- Temperature and humidity sensors
- Battery voltage and percentage
- Internal “Voltage Present” status
- Custom telemetry events for each sleep cycle
These events can be used for automation or historical analysis of battery health and uptime.
You can modify the following:
- Sleep intervals to optimize battery performance
- ADC multipliers to match your resistor divider ratios
- Nighttime cutoff hour (default: after 21:00)
- Static IP configuration for Wi-Fi stability
All parameters are defined through YAML substitutions and can be adjusted without altering logic flow.
Ideal for:
- Remote soil and environment monitoring
- Solar-powered IoT setups
- Battery-powered outdoor sensors
- Long-term deployments with minimal maintenance
- ESPHome ≥ 2023.11
- Home Assistant (optional for telemetry)
- SHT31 I²C sensor
This project is licensed under the GNU General Public License v3.0 (GPL-3.0).
See the LICENSE file for full text.