Adafruit
Adafruit STEMMA Soil Sensor - I2C Capacitive Moisture Sensor
The Adafruit STEMMA Soil Sensor uses capacitive measurement to detect soil moisture — a more durable approach than resistive sensors that corrode over time. ...
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The Adafruit STEMMA Soil Sensor uses capacitive measurement to detect soil moisture — a more durable approach than resistive sensors that corrode over time. With a single probe and no exposed metal, it avoids oxidation issues and won't introduce DC currents into your plants.
The ATSAMD10 microcontroller provides capacitive touch readings ranging from approximately 200 (very dry) to 2000 (very wet), plus an ambient temperature reading (±2 °C). Connect via a 4-pin JST-PH STEMMA cable to any 3–5V microcontroller over I2C — no soldering required.
Key Features
- Capacitive Moisture Sensing – No exposed metal, no corrosion, no DC current in soil
- Moisture Range – ~200 (very dry) to ~2000 (very wet)
- Temperature Sensor – Built-in ambient reading (±2 °C)
- I2C Interface – 4-pin JST-PH STEMMA connector for plug-and-play wiring
- 3–5V Compatible – Works with any microcontroller or single-board computer
- ATSAMD10 Chip – Onboard microcontroller handles all measurements
Ideal For
- Automated plant watering systems
- Garden and greenhouse monitoring
- Soil moisture data logging
- Educational science projects
Package Contents
- 1× STEMMA Soil Sensor board
Jargon buster
Plain-language definitions for the technical terms used above.
- CircuitPython
- A beginner-friendly version of Python designed to run directly on microcontroller boards. If a product supports CircuitPython, you can often program it by copying code files onto the board rather than setting up a more complex toolchain.
- DC
- DC means direct current, where electricity flows in one constant direction, as supplied by batteries, USB ports and many plug-pack power supplies. When a product specifies DC, it runs from a DC supply rather than mains AC, so you need to provide the correct voltage and polarity.
- Grove
- Grove is a standardised 4-pin plug-in connector system for sensors and modules that avoids soldering and jumper wires, with different cable types carrying I2C, UART, analogue or digital signals. When a product is Grove-compatible it can be quicker to connect supported modules, provided the connector type, signal and voltage all match.
- I2C
- I2C is a two-wire communication bus used by many sensors and small modules. It matters because several I2C devices can share the same two wires, but each device needs a compatible address and your controller must support I2C.
- microcontroller
- A microcontroller is a small computer on a single chip that runs a stored program and controls connected inputs and outputs such as buttons, sensors, displays and communication interfaces. In a device built around one, it is the part that executes the code and coordinates the device's behaviour.
- pH
- A measure of how acidic or alkaline a liquid is, on a scale where 7 is neutral. For a water monitoring kit, pH tells you about water chemistry and whether the included probe matches the range and accuracy your project needs.
- single-board computer
- A complete computer built onto one circuit board, usually including the processor, memory, ports, and connectors. This matters because accessories like heatsinks must match the board’s layout and mounting holes to fit properly.
- STEMMA
- A plug-and-cable connection system used on some maker electronics boards to make wiring simpler. If a product uses STEMMA, you need the matching cable or connector type to plug it in without soldering.
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Sensors & Input
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