DS1307 Precision RTC Real Time Clock Memory Module
New Original I2C Real-Time Clock for Arduino
The DS1307 is the most popular and widelyused realtime clock (RTC) module for Arduino and 5V microcontroller projects. It keeps accurate time even when the main power is lost, using a backup battery.
BatteryBacked Timekeeping Maintains time for over 5 years on a coin cell
I2C Interface Easy 2wire connection to Arduino
Operating voltage is 4.5V to 5.5V - designed for 5V Arduino boards
Use the standard RTClib library for easy integration
For 3.3V systems, consider the PCF8523 or DS3231 instead
Technical Specifications
| Parameter | Value |
|---|
| Supply Voltage | 4.5V to 5.5V |
| Battery Backup Current | <500nA |
| I2C Interface | 2-Wire |
| Memory | 56 Bytes NV SRAM |
| Time Format | 12/24 Hour |
| Date Format | YYMMDD-dd |
| Programmable Output | Square-Wave Signal |
= Key Features =
+Automatic PowerFail Detection Switches to battery backup seamlessly
+Leap Year Compensation - Valid through year 2100
+56Byte NonVolatile RAM - Store data even during power loss
+Programmable Square Wave Output - Useful for timing signals
+Low Power Consumption - <500nA in battery mode
= Applications =
- Data logging and time-stamping
- Digital clocks and timers
- Automated irrigation systems
- Alarm and scheduling projects
- Industrial monitoring equipment
- Energy metering devices
Arduino Compatible - Works with standard RTC libraries
UL Recognized - Certified for reliable operation
√ CR2032 battery holder included
√ I2C pull-up resistors on board
√ Ready for immediate use
Connection Guide
Module to Arduino:
- VCC: 5V (not 3.3V)
- GND: Ground
- SDA: A4 (Uno/Nano)
- SCL: A5 (Uno/Nano)
For other boards:
- Mega: SDAD20, SCLD21
- Due/ESP32: SDA/SDA pins
- Use Wire library for communication
Use 2.2kΩ to 4.7kΩ pull-up resistors on SDA and SCL lines
If using SoftwareSerial, adjust pin assignments accordingly
This is a 5V device - level shifting needed for 3.3V logic
Battery must be installed for time retention during power loss
Programming Instructions
Install RTClib library via Arduino IDE Library Manager. The library provides simple functions for setting and reading time.
Basic setup:
- Initialize Wire library
- Call rtc.begin() to detect module
- Check rtc.isrunning() for battery status
- Use rtc.adjust() to set initial time
- Use rtc.now() to read current time
Time setting formats:
- rtc.adjust(DateTime(F(DATE), F(TIME)))
- rtc.adjust(DateTime(2026, 7, 17, 14, 30, 0))
- Reading returns hours, minutes, seconds, date
Software Library Support - RTClib and DS1307 libraries available
Simple Time Setting - Set once, runs for years
Over 5 years battery life with CR2032
Works with Arduino Uno, Mega, Nano
Troubleshooting
Module not responding:
- Verify 5V power connection
- Check I2C connections (SDA/SCL)
- Ensure battery is installed
- Add pull-up resistors if missing
- Avoid loose wiring
Time lost on power-off:
- Replace CR2032 battery
- Check battery holder contacts
- Verify battery voltage above 2.5V
- Avoid using without battery
Incorrect time reading:
- Set time again via software
- Check for I2C communication errors
- Avoid interference from other devices
