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Adafruit

$15.05 |
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The Adafruit DS1307 Real Time Clock breakout keeps accurate time even when your microcontroller loses power or is reprogrammed. This battery-backed I2C RTC i...

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The Adafruit DS1307 Real Time Clock breakout keeps accurate time even when your microcontroller loses power or is reprogrammed. This battery-backed I2C RTC is one of the most widely used clock chips, making it a reliable choice for datalogging, alarms, timers, and clock projects.

The DS1307 requires 5V power but has been successfully used with 3.3V logic levels. It comes fully assembled with headers, ready to plug into a breadboard. A CR1220 coin cell battery (not included) provides backup power for 5+ years of timekeeping.

Key Features

  • Battery-Backed Timekeeping – Maintains time through power loss and reprogramming
  • I2C Interface – Simple two-wire communication
  • 5+ Year Battery Life – With CR1220 coin cell (not included)
  • Fully AssembledPCB and headers included, breadboard-ready
  • Two Mounting Holes – For permanent installations

Also Available

Ideal For

  • Datalogging with timestamps
  • Clock and alarm projects
  • Scheduled automation and timers
  • Any project needing persistent timekeeping

Package Contents

  • 1× DS1307 RTC breakout board (fully assembled with headers)
Note: CR1220 coin cell battery not included. The DS1307 requires 5V power. It may lose or gain up to 2 seconds per day — for higher precision, consider the DS3231.

Jargon buster

Plain-language definitions for the technical terms used above.

breakout
A breakout board carries a small or fine-pitched component and brings its connections out to standard, breadboard- and header-friendly pins. Describing a part as a breakout means it can be wired into a project without soldering directly to the component's tiny contacts.
Headers
Rows of connector contacts on a fixed pitch (commonly 2.54 mm) used to link a board to a breadboard, jumper wires, or another board. They come as male pin headers and female socket headers; when a module ships with pre-soldered headers it can be used straight away, whereas bare pads require soldering the pins yourself.
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.
microcontroller
A microcontroller is a small computer on a single chip that runs a stored program and controls connected inputs and outputs such as buttons, sensors, displays and communication interfaces. In a device built around one, it is the part that executes the code and coordinates the device's behaviour.
PCB
A printed circuit board (PCB) is a board, usually rigid, with etched copper tracks that connect electronic components together without loose wiring. Components are mounted on the board and signals route between them through the copper layout.
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.
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.
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