This tutorial shows how to explore an inexpensive DS1307 Real Time Clock module with Arduino using the DS1307RTC and Time libraries.
The RTC module can be purchased on eBay at very low cost (<$3), and is an ideal educational project for the budding Arduino practitioner.
It is an ideal low cost project for a first exploration of explore I2C.
The project uses the DS1307RTC and Time library modules in Arduino, and the v1.05 Arduino IDE is used for the project. The DS1307RTC library package contains example code to set and read the RTC, they are used here with small modification.
The source code is modified in both examples to put Vcc and Gnd on a3 and a2 to power the RTC module (without using jumper leads).