Overview
Add precise environmental sensing to your next project with the Adafruit Si7021 STEMMA QT Breakout. Built around the reliable Si7021 digital sensor from Silicon Labs, this board delivers accurate temperature and relative humidity readings over a simple I²C interface, making it ideal for weather stations, indoor air monitoring, HVAC logging, and IoT systems.
The Si7021 offers ±3% RH accuracy (0–80% RH range) and ±0.4°C temperature accuracy across –10°C to +85°C. With digital I²C output, you avoid analog calibration issues and can integrate directly with microcontrollers like Arduino, Raspberry Pi, and Feather boards.
Designed for Fast, Clean Integration
This breakout uses the STEMMA QT form factor with dual JST SH connectors, fully compatible with SparkFun Qwiic cables. That means you can plug it in without soldering and even daisy-chain multiple I²C devices in seconds.
For traditional prototyping, all pins are also broken out to 0.1" headers (included, soldering required).
Specification
Technical details for Adafruit Si7021 Temp Humidity Sensor Breakout Board.
| Specification | Details |
|---|---|
| Product Type | Temperature & Relative Humidity Sensor Breakout |
| Sensor IC | Silicon Labs Si7021 |
| Interface | I2C |
| Humidity Accuracy | ±3% RH |
| Humidity Measurement Range | 0% to 80% RH |
| Temperature Accuracy | ±0.4°C |
| Temperature Measurement Range | −10°C to +85°C |
| Operating Voltage | 3.3V / 5V compatible (onboard regulator + level shifting) |
| Connectors | 2x STEMMA QT (JST SH 4-pin), Qwiic-compatible |
| Header Breakout | 0.1" standard header pins (included; soldering required) |
| Protection | PTFE filter membrane over sensor |
| Compatibility | Raspberry Pi, Arduino, Feather, and most I2C microcontrollers |
| Included in Box | Si7021 breakout board, pin header |
| Not Included | STEMMA QT / Qwiic cable |
Pinout
| Pin | Description |
|---|---|
| Vin | Power input pin. Accepts 3–5V DC. Onboard regulator converts input to 3.3V for the Si7021 sensor. Use the same voltage as your microcontroller logic level (e.g., 5V for Arduino, 3.3V for Raspberry Pi). |
| 3V3 | 3.3V output from the onboard voltage regulator. Can supply up to 100mA for external circuitry if required. |
| GND | Common ground connection for power and logic. |
| SCL | I2C clock line. Connect to your microcontroller’s I2C clock pin. |
| SDA | I2C data line. Connect to your microcontroller’s I2C data pin. |
| STEMMA QT | Dual JST SH 4-pin connectors carrying Vin, GND, SDA, and SCL. Fully compatible with STEMMA QT and SparkFun Qwiic systems for solderless plug-and-play I2C connections and device chaining. |
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