Introduction to DS1307 RTC Module

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The DS1307 RTC module is a time tracking device that gives the current time and date. The word RTC is meant Real Time Clock. The RTC module made of clock chip DS1307. This module is generally used in computers, laptops, mobiles, embedded system applications devices, etc. to provide time and date. RTC module works on the I2C protocol. The module provides details such as second, minute, hour, day of the week, day of the month, month, and year including correction for leap year. One more interesting thing It can operate either in 12 Hours or in 24 Hours format. It’s can be used in projects like containing data-logging, clock-building, time stamping, timers, and alarms.

DS1307 RTC Module Pin Diagram

DS1302 Real Time Clock (RTC) Module Pin Diagram/Pinout/Pin Configuration
DS1302 Real Time Clock (RTC) Module Pin Diagram/Pinout/Pin Configuration
Pin NameDescription
SQWThe SQW pin has a cool feature, it can produce outputs one of four square-wave frequency 1 Hz, 4 kHz, 8 kHz, or 32 kHz and can be possible programmatically.
DSThis pin is used to read Output from the DS18B20 temperature sensor if the RTC module has a DS18B20 temperature sensor installed.
SCLThis is a clock input I2C serial communication pin. It is used to synchronize data movement on the serial interface.
SDAThis pin is used for the data input/output for the I2C serial interface.
VCCIt is a positive power input pin of the module in range 3.3V to 5.5V.
GNDGND is a negative(ground) power input pin
BATBAT pin is a backup supply input for any standard 3V lithium cell or other energy sources to maintain accurate timekeeping when the main power to the device is interrupted.

DS1307 RTC Module Hardware Overview

The DS1307 RTC module is consists of mainly 5 key components. These are DS1307 RTC chip, 32kHz crystal oscillator, 24C32 EEPROM chip, battery holder, and soldering place for DS18B20 temperature sensor

DS1302 Real Time Clock (RTC) Module Hardware Overview
DS1302 Real Time Clock (RTC) Module Hardware Overview

DS1307 RTC chip

The DS1307 RTC chip is a low power, full binary-coded decimal (BCD) clock/calendar RTC (Real Time Clock) IC with 56 bytes of SVRAM that communicates through I2C Protocol. The DS1307 is 8 pin IC. The IC is operated on low power consumption when it operated on a battery then it consumes less than 500 nA power. It manages all timekeeping functions.

This IC clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The clock can provide time in the format of 24-hour or 12-hour with AM/PM indicator. The most interesting things are it can automatically adjust the end date of a month, like 31 or 28 days in a month. Also, it can corrections for leap year.

32kHz Crystal Oscillator

This module also consists of a 32kHz crystal oscillator. It is connected between the DS1302 IC pin1 and pin2. crystal oscillator provides frequency to the IC to operate time-keeping functions.

But the external temperature can affect the oscillation frequency of these crystals. This change in the oscillation frequency can be negligible but it surely adds up.

24C32 EEPROM chip

Also, the RTC module comes with a 32 bytes Atmel 24C32 EEPROM chip, which having limited read-write cycles. This EEPROM chip can be used to save settings or clock/calendar. It uses the I2C interface for communication and shares the same I2C bus as DS1307.

Battery Holder

The bottom side of the module has a battery holder for a 20mm 3V lithium coin cell. Any CR2032 battery can fit in the battery holder. The DS1307 incorporates a battery input and maintains accurate timekeeping when the main power to the device is interrupted.

The built-in power-sense circuit continuously monitors the status of the input (VCC) power supply to detect power failures and automatically switches to the backup supply. So, it can continue to maintain the time and date while device power is incorrect.

Soldering Place for DS18B20

One more interesting feature of the module is it has a Soldering place to install a DS18B20 temperature sensor. The module has the 3 holes in the corner left next to the battery holder where we can solder the temperature sensor. if you will install it you can be able to get temperature readings from the DS pin. It can be used in temperature based time drift projects.

Sensor Specifications

Range of Operating Voltage3.3V – 5V
Typical voltage supply5V
Real Time lock chipDS1307 I2C
EEPROM ChipAT24C32 32K I2C EEPROM memory
Battery typeLIR2032 rechargeable lithium battery
Power consumptionIt operated on a battery then it consumes less than 500 nA power.
Clock ProvideHour, Minutes, Seconds, AM/PM.
Calendar providesDay, Date, Month, Year.
PCB Size27mm * 28mm * 8.4mm (L*W*H)


  • To design real time clock.
  • DIY projects.
  • Robotics projects.
  • Arduino projects.
  • Raspberry-Pi projects.
  • Electrical/Electronic projects.

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