Keep track of time even when your project loses power or gets reprogrammed. The PCF8523 Real Time Clock breakout is a battery-backed RTC that communicates over I2C and works with both 3.3 V and 5 V power and logic. Perfect for datalogging, clock building, time stamping, timers, and alarms.

Works with Arduino (using the Adafruit RTC library), CircuitPython, and Raspberry Pi or other single-board Linux computers. For higher precision (temperature-compensated), see the DS3231 Precision RTC. For DS1307 compatibility, see the DS1307 RTC Breakout.

Key Features

• PCF8523 RTC Chip – Battery-backed real-time clock with I2C interface
• 3.3 V and 5 V Compatible – Works with both power and logic levels
• CR1220 Battery Backup – Keeps time for 5+ years on a coin cell (battery not included)
• Breadboard Friendly – PCB and header included, plugs straight into a breadboard
• Two Mounting Holes – For permanent installation

Compatibility

• Arduino (Adafruit RTClib library)
• CircuitPython / Python
• Raspberry Pi and other Linux SBCs
• Any microcontroller with I2C support

Ideal For

• Datalogging with accurate timestamps
• Clock and alarm projects
• Scheduled task execution
• Time-stamped sensor readings

Package Contents

• 1× Adafruit PCF8523 Real Time Clock Breakout, assembled with header

Resources

• PCF8523 RTC Learn Guide – Code, libraries, schematics, and wiring diagrams