Arduino internal clock inaccurate??

Question

Hello! I am a newbie here and fairly new with the Arduino. I am building a piece of art that has a 150 year old clock as the main subject. I am going to use an Arduino to drive a stepper that runs the clock, a DC motor for the Chime drive (For visual effect) and a solenoid for the escapement mechanism also for visual effect. I've heard that the internal clock on the Arduino is inaccurate from others. What will I need to make it have an accurate output?

shabaz · Accepted Answer

Hi Jon, Interesting project! Will it not damage the mechanism though? Maybe something like that is worth a lot of money. You didn't say how accurate you wanted : ) Anyway, the Arduino clock is ok, but not spectacular. It may not be precise, and you'll notice time drifting slightly (perhaps a minute per week or a bit more - enough to be irritating). A nice device is the DS3231, you could expect a minute or two of gain or loss per year; therefore in comparison the Arduino clock is an order of magnitude worse. In practice the Arduino clock is more worse than that, because it is affected by change in temperature (the DS3231 is temperature compensated, so affected less). Actually, after all that, you would have achieved a clock circuit that is still an order of magnitude poorer than the 250-year old Harrison clocks : ) which were only out by a second per month, but the DS3231 circuit costs a tiny fraction of course and doesn't take a lifetime to build. There are other ways to have precision clocks (e.g. GPS based or NTP based) depending on where you wanted to go with this. Information on how to use the DS3231 is here . One important point is that it has 3.3V logic, not 5V like the Arduino Uno. So you may wish to use a different board than the Uno. There are some 3.3V Arduinos, but I have not used them so I wouldn't be able to recommend any. There are Arduinos (and other single board computers such as Raspberry Pi - although this could be considered over-the-top for a clock) with network capability or with Ethernet shields, so NTP could be used with them. A google search on 'arduino ntp clock' revealed some hits.

Arduino internal clock inaccurate??

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