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Strange behaviour in Real Time Clock sD2405


#1

Hi. Has anyone experienced strange behaviour in the RTC Module sD2405? I am using one of these modules to supply a real time and date in a gadgeteer project I have written to collect environmental data and then SMS (hopefully GPRS with a little more time) resulting data. I find the RTC sD2405 loses time - always in round hours and mostly 8 or 9 hours (although not exclusively). I am finding it hard to predict the loss in time and can’t seem to figure out why it happens. I use a simple c# script in Visual Studio to set the time on the sD2405 from an internet time server. I then power down the system I use to set the time, move the SD2405 to my logging set up and after a few power up/downs I then notice the RTC has lost time. Any thoughts/ideas would be most appreciated. Cheers. Matt


#2

Hi Matt,

what mainboard are you using? I assume you mean the DF Robot module http://www.dfrobot.com/index.php?route=product/product&product_id=842#.UwkcBY1WHIU ? @ Duke Nukem may have experience with his module to see if it’s maintaining the time to spec (within 2.5mins/year), but there may be very few others using this external device (as most mainboards do offer this).

When I hear someone say an RTC is losing time then I often think it’s something external to the RTC, like the battery or a corrupted signal being read - particularly when it’s “round hours” that it’s out. What timezone are you in, out of interest? If you can repro this reasonably easily (with just your few power up/down cycles) you might be able to have a simple test application that helps highlight this and understand it more.