The BM25S2621-1 is a capacitive soil temperature and humidity sensor module that provides real-time data on soil moisture and temperature levels. It communicates via RS485 and supports the Modbus RTU protocol, making it ideal for integration into smart farming applications like automated irrigation and greenhouse monitoring.
Humidity is measured in RH (Relative Humidity), which indicates the percentage of water vapor in the soil compared to the maximum it can hold at a given temperature. For example, 50% RH means the soil holds half the water vapor it could potentially contain. The higher the RH, the more moisture in the soil.
Key Functions
- Real-time Monitoring: Retrieves temperature and humidity data every 13ms.
- Auto Sleep Mode: Automatically enters low-power mode if no data command is received within 5 seconds.
- Pre-calibrated: Each unit is factory-calibrated and ready to use out of the box.
- Multi-Module Support: Each sensor can be assigned a unique ID for large-scale or multi-point deployments.
The module uses a capacitive humidity sensor and a high-precision NTC temperature sensor. Combined with its waterproof and anti-rust design, it remains stable even during long-term deployment in the soil.
Setup Instructions
This product is pre-calibrated and ready to use.
1. Wiring: Connect power (3.3V~5.5V) and RS485 communication lines. Ensure correct polarity.
(Note: If your controller only supports UART, use the BMB22M301 RS485 Bridge module to convert.)
2. Initialization: Once powered, the module auto-starts. If no data is received within 5 seconds, it enters sleep mode.
3. Send Command: Use the host device to send Modbus RTU instructions to retrieve current humidity and temperature readings.
4. Calibration (Optional): For higher precision, perform temperature, humidity, or dry-point calibration via command.
5. Multi-Module Configuration (Advanced): For multiple modules, assign each a unique ID so the host can query them individually.
⬥ For detailed protocol and command formats, refer to the "Communication Protocol" section in the datasheet.
Recommended Accessory: RS485 Bridge Module BMB22M301
If your controller (e.g., Arduino, BMduino) only supports UART, the BMB22M301 RS485 Bridge module allows easy conversion to RS485, enabling seamless communication with the BM25S2621-1.
The BM25S2621-1 supports up to 1000kbps data transfer rates and can connect to up to 256 RS485 devices, making it perfect for long-distance data acquisition and multi-node sensor networks — ideal for large greenhouses or agricultural research projects.
