ProtoCentral AS6221 Wearable Body Temperature Sensor – QWIIC Compatible

The ProtoCentral AS6221 Wearable Body Temperature Sensor is a QWIIC-compatible, skin-contact temperature probe built around the ams OSRAM AS6221 — a factory-calibrated digital temperature sensor that delivers ±0.09 °C accuracy across the 20 °C–42 °C body-temperature band. It is the higher-accuracy, lower-voltage successor to our MAX30205 wearable thermometer.

Because the AS6221 is a digital I²C sensor, no external ADC or calibration is needed — read the temperature directly over two wires. The sensor head is a small, gold-plated thermally-conductive disc that sits flat against the skin, epoxy-potted on the reverse for moisture resistance, and joined to a flexible cable. The cable terminates in a 4-pin JST SH (QWIIC) connector, dropping it straight into the QWIIC / STEMMA QT ecosystem.

Getting started: Install the ProtoCentral AS6221 Arduino library — search for “ProtoCentral AS6221” in the Arduino IDE Library Manager, or download it from GitHub — then run the bundled example to stream temperature over I²C. A MicroPython library is also available for Raspberry Pi Pico, ESP32 and other MicroPython boards.

Open hardware: The complete KiCad design — schematic, PCB layout and the exported schematic PDF — lives in the AS6221 hardware repository, released under the CERN-OHL-P v2 licence.

Features

• ams OSRAM AS6221 — factory-calibrated digital temperature sensor, no calibration required
• High accuracy: ±0.09 °C over the 20 °C–42 °C body-temperature range
• 16-bit temperature resolution (0.0078125 °C per LSB)
• Wide supply range: 1.7 V – 3.6 V, with accuracy held across the full range
• Low power: ~6 µA typical operating current (at 4 Hz)
• Standard I²C 2-wire interface with 8 selectable addresses for multi-sensor buses
• Gold-plated thermally-conductive contact face for fast, accurate skin readings
• Epoxy-potted head for moisture resistance
• Flexible cable for wearable skin-contact use
• Solder-free QWIIC / STEMMA QT integration
• Open-source hardware (CERN-OHL-P v2)

Applications

• Wearable and continuous body / skin temperature monitoring
• Clinical and consumer thermometry
• Fever screening and fitness / wellness wearables
• Research data logging and patient-monitoring prototypes

Specifications

• Sensor: ams OSRAM AS6221 (WLCSP, 1.5 × 1 mm)
• Accuracy: ±0.09 °C (20 °C – 42 °C)
• Operating temperature range: 0 °C – 125 °C
• Resolution: 16-bit (0.0078125 °C / LSB)
• Interface: I²C, 8 selectable addresses
• Supply: 1.7 V – 3.6 V
• Operating current: ~6 µA typical (4 Hz)
• Connector: 4-pin JST SH (QWIIC / STEMMA QT)