Adafruit PCF8523 Real Time Clock (RTC) Assembled Breakout Board

by Adafruit

This is a great battery-backed real time clock (RTC) that allows your microcontroller project to keep track of time even if it is reprogrammed, or if the power is lost.

Perfect for datalogging, clock-building, time stamping, timers and alarms, etc. Equipped with PCF8523 RTC - it can run from 3.3V or 5V power & logic!

Works great with an Arduino using this RTC library, with CircuitPython or with a Raspberry Pi (or similar single board linux computer)

  • PCB & header are included
  • Plugs into any breadboard, or you can use wires
  • Two mounting holes
  • Will keep time for 5 years or more

Note: This product does not come with a CR1220 coin cell battery. We recommend you purchase a coin cell battery to use with this product.

The PCF8523 is simple and inexpensive but not a high precision device. It may lose or gain up to 2 seconds a day. For a high-precision, temperature compensated alternative, please check out the DS3231 precision RTC.

Check out this detailed guide for code, libraries, schematics, Fritzing object and more!

Technical Details

Check out this detailed guide for code, libraries, schematics, Fritzing object and more!

Revision History:

  • As of March 25, 2022, this board now may come with a PCB version that has HVSON or SOIC-8 chip package depending on what chip is available in the market. Both are identical functionality!
  • As of Aug 30, 2017 we have updated the design to have an RC filter on the power supply to reduce accidental resetting if power drops too fast!
  • Mounting holes are 2.2mm (0.086in) diameter, 25mm (0.98in) apart
  • This board/chip uses I2C 7-bit address 0x68

Product Dimensions: 25.5mm x 21.7mm x 4.8mm / 1.0" x 0.9" x 0.2"

Product Weight: 1.2g / 0.0oz

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