Choosing The Right RTC For Your Project

When it comes to measuring time on microcontrollers, there’s plenty of ways to go about things. For most quick and dirty purposes, such as debounce delays or other wait states, merely counting away a few cycles of the main clock will serve the purpose.  Accurate to the tens of milliseconds, they get the average utility jobs done without too much fuss.

However, many projects are far more exacting in their requirements. When you’re building a clock, or a datalogger, or anything that relies on a stable sense of passing time for more than a few minutes, you’ll want a Real Time Clock. So called due to their nature of dealing with real time, as we humans tend to conceive it, these devices take it upon themselves to provide timekeeping services with a high degree of accuracy. We’ve compiled a guide to common parts and their potential applications so you can get things right the first time, every time.

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Prototyping The New Office Clock

[Damage] was tapped to build a new clock to hang on the wall at the office. He got a hold of some 6.5 inch seven segment displays for the hours and minutes, as well as some 4.5 inch modules for the date and month. Rather than jump right in with the large hardware (especially because he’s waiting for the PCB order to arrive)  he built this prototype with more commonly sized displays.

His build is Arduino powered. In the video after the break he mentions the temperature compensated crystal oscillator that keeps the time. We’d wager that’s the DS3234 based RTC module that Sparkfun sells. This is the same chip family as the Chronodot and it was our choice for the Ping Pong Clock.

The finished clock will hang high on wall, out of reach when you need to set the time. This shouldn’t need to be done much – if ever – since that RTC includes a backup battery. But [Damage] took the time to develop a remote programming device anyway. Using another Arduino, an LCD display, and an Xbee pair he whipped up a remote that can be used to navigate and change the main unit’s settings.

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