Adafruit
Adafruit DS3231 Precision RTC - STEMMA QT
The Adafruit DS3231 Precision RTC with STEMMA QT connectors is a highly accurate I2C real-time clock featuring an integrated temperature-compensated crystal ...
The Adafruit DS3231 Precision RTC with STEMMA QT connectors is a highly accurate I2C real-time clock featuring an integrated temperature-compensated crystal oscillator (TCXO). Unlike standard RTCs that rely on an external 32 kHz crystal, the DS3231 houses the crystal internally alongside a temperature sensor that continuously compensates for frequency drift, delivering accuracy of ±2 ppm (about ±1 minute per year).
This version adds STEMMA QT / Qwiic connectors for solderless I2C connections, making it easy to daisy-chain with other I2C sensors and accessories. It works with both 3.3V (Feather, Raspberry Pi) and 5V (Arduino, Metro) logic levels. With a CR1220 coin cell on the back, the DS3231 maintains precise timekeeping for years even when main power is lost.
Key Features
- Integrated TCXO – On-chip crystal and temperature sensor for automatic drift compensation
- ±2 ppm Accuracy – Approximately ±1 minute per year, far superior to standard RTCs
- STEMMA QT / Qwiic – Dual I2C connectors for solderless daisy-chaining
- Battery Backup – CR1220 coin cell holder on board for uninterrupted timekeeping during power loss
- 3.3V and 5V Compatible – On-board level shifting for broad platform support
- I2C Interface – Simple two-wire communication with standard I2C addressing
- Breadboard-Friendly – Compact breakout with included header strip
Also Available
- DS3231 Precision RTC Breakout (standard header version)
- DS1307 RTC Breakout (basic, lower cost)
- PCF8523 RTC Breakout (3.3V compatible)
Ideal For
- Precision data logging with accurate timestamps
- Clocks and timers requiring minimal drift
- IoT devices needing reliable timekeeping through power cycles
- Solderless prototyping with STEMMA QT ecosystem
Package Contents
- 1× Adafruit DS3231 Precision RTC – STEMMA QT (fully assembled and tested)
- 1× Header strip
Jargon buster
Plain-language definitions for the technical terms used above.
- breakout
- A breakout is a small circuit board that makes a tiny or hard-to-solder component easier to connect to with standard pins. It matters because this OLED module can be wired into a microcontroller project without needing to solder directly to the display’s fine contacts.
- 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.
- IoT
- Short for Internet of Things, meaning physical devices that connect to networks or the internet to send data or be controlled remotely. It matters if you want projects such as connected sensors, remote controls or classroom data-logging activities.
- ppm
- ppm means parts per million, a common way to express very small gas concentrations in air. For CO₂ sensors, the ppm range tells you what levels the sensor can measure, such as normal indoor air through to poorly ventilated spaces.
- Qwiic
- Qwiic is a plug-in connector system for I2C devices that uses small 4-pin cables, so you can connect compatible sensors without soldering. It matters because your controller or adapter also needs Qwiic, or you will need a cable or breakout to wire it up.
- RTC
- A Real-Time Clock keeps track of time even when the main processor is asleep or powered down, usually with a small backup battery. It matters for data logging and tracking projects that need accurate timestamps.
- 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.
- STEMMA QT
- A small plug-in connector system for I2C boards that lets you connect compatible sensors and controllers without soldering. It matters because it can make wiring faster and less error-prone, especially when adding several small modules to a project.
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