Arduino Workshop, 2nd Edition

20 Real-Time Clocks

In this chapter you will

• Set and retrieve the time and date from a real-time clock module
• Discover new ways to connect devices to an Arduino
• Create a digital clock
• Build an employee RFID time clock

A real-time clock (RTC) IC module is a small timekeeping device that opens up all sorts of possibilities for Arduino projects. Once set with the current time and date, an RTC provides accurate time and date data on request.

You’ll find many different RTC ICs on the market, some more accurate than others. In this chapter, we’ll use the Maxim DS3231; it doesn’t require any external circuitry other than a backup battery, and it’s incredibly accurate and quite robust in module form. The DS3231 is available as a breakout board ...