What is RTC (Real Time Clock) ?

It is Similar Clock in Real analog and digital Clock which is continues working until Battery Power is loss.But in Computer and Laptop we shutdown and dissconnect power but here next time we start time is not lost.here the small Real-time clock (RTC) that keeps runs the current time with small Battery Cmos Cell.RTCs are present in almost any electronic device which needs to keep accurate time.

Number of Real Time Clock ICs.

  • DS1307 – 64 x 8, Serial, I2C Real-Time Clock.
  • DS3234 – Extremely Accurate SPI Bus RTC with Integrated Crystal and SRAM
  • DS3231 – Extremely Accurate I2C-Integrated RTC/TCXO/Crystal
  • DS1302 – Trickle-Charge Timekeeping Chip
  • DS1308 – Low-Current I²C RTC with 56-Byte NV RAM
  • PCF8563 – Real-time clock/calendar
  • MCP79400 – Real-Time Clock/Calendar with SRAM and Protected EEPROM

RTC Modules online Available in Amazon

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Making Own RTC

Understanding Real Time Clock

Understanding Real Time Clock
List of Components used in Circuit

  • DS1307 RTC chip
  • 32.768 Khz generic quartz watch crystal
  • 100nF Ceramic Capacitor
  • 10K Resistors
  • 12mm 3V Lithium Coin Cell (CR2032)
  • 12mm Coin Cell Holder
  • 5-Pin Male Header
  • Circuit Board

Working of RTC

Every RTC use an external 32kHz timing crystal that is used to keep time with low current draw.but some ic we not need crystal.This is the same frequency used in quartz clocks and watches,32khz is equal 215 cycles per second this is best why to use a binary counter which trigger control rigisters update values.there internal memory which maintains seconds, minutes, hours, day, date, month, and year information.The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections of leap year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. Two programmable time-of-day alarms. To hold memory data a 12mm coin-cell battery for battery backup to avoid data loss. To Read or Set time with Serial interface I2C allow inside ic memory.

Understanding Real Time Clock
Block Diagram

Wiring / Connection with Arduino

Understanding Real Time Clock

Programming with Arduino to Set Time Without Library


RTC Setting Without Library
RTC Setting Without Library

Programming with Arduino to Read Time Without Library


Read Time From RTC
Read Time From RTC

Programming with Arduino to Set Time With Library

These Programs use a Library : RTClib


RTC Setting Using library
RTC Setting Using library

Programming with Arduino to Read Time With Library


Read Time From RTC With Library
Read Time From RTC With Library


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Understanding Real Time Clock

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Arvind Ahir

Im Arvind Ahir Student Study Btech CSE , Skills Web Developer,Networking ,Arduino .

One thought on “Understanding Real Time Clock

  • 20/08/2018 at 1:57 am

    This is truly useful, thanks.


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