The battery is not included.
- Real-Time Clock (RTC) counts seconds, minutes, hours, date of the month, month, day of the week, and year with Leap-Year compensation valid up to 2100
- 56-Byte, Battery-Backed, Nonvolatile (NV)RAM for data storage
- I2C serial interface
- 5V DC supply
- Programmable Square-Wave output signal
- Automatic Power-Fail detect and switch circuitry
- Consumes less than 500nA in Battery-Backup Mode with Oscillator Running
Grove - DS1307 RTC is based on the clock chip DS1307 and supports I2C communication! Grove - DS1307 RTC uses a Lithium cell battery (CR1225). We choose to use the RTC based on DS1307 as it is low cost and also very energy efficient. It can run for years on a very small coin cell!
The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator.
What is an RTC (Real Time Clock), why do we need RTC for Arduino microcontroller?
An RTC (real-time clock) refers to a clock that tracks the current time and can be used to program actions at a specific time.
Arduino and almost all microcontrollers have built-in timers, they can run as long as there is power. However, once the power is turned off (either manually or due to a power failure), all timers will be reset to 0.
It is acceptable to use the internal timer for timing of simple projects if you don't mind when the timer resets to zero once there is no power. But for projects such as data loggers, clocks, alarms, which requires the timer to run independently of the external power supply, you need to use an RTC.
Almost all RTC are low-current built-in ICs and able to run on a single lithium battery for many years. Currently, RTC based on the DS1307 real-time clock is one of the most popular RTC modules.