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I have two DS1307 I2C RTC Modules

Link: http://www.ebay.com/itm/190720534421?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

I hooked up the rtc to the mega and loaded the TimeRTCSet example from the Time examples

the sketch reports the time as 0:00:00  1 1 2000. I sent the command T1353540094 which is a valid unix time and the sketch starts reporting
23:20:00  21-11-2012 ... Ok seems fine.  I hit the reset button on the arduino and the sketch resets and the time is still valid.  I unplug the mega from the usb, plug it back in and start the serial monitor and the date defaults back to 0:00:00 1 1 2000.  I checked the battery and it has 3.93v, I checked to see if the rtc was actually talking on the i2c bus by adding a Serial.println(RTC.get()); to the main loop and I get incremented time as I would expect.  I disconnected the rtc from the arduion and the sketch stops so I can assume communications are working properly.  I do have 10k pull resistors installed on sda and scl as tutorials have shown.

I asked the guys in irc and one of them said that if I didnt see voltage on the VCC / GND pins then the battery wasnt working, and I thought that there would be some kind of mechanism to prevent voltage/current flow from the battery to the vcc pin, dont know what to think...

Any help would be appreciated

Thanks

Any ideas?
« Last Edit: November 21, 2012, 06:00:39 pm by NobleNoob » Logged

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Sounds like a bad connection to the battery.  The advertisement says that it is supposed to arrive with he time per-set. Check the solder connections.
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Note: I am giving up on these modules.  I have two of them and one of them keeps data on reset and not on no power and the other one doesn't keep data either way.  I don't have electrical knowledge to debug hardware so I say caution to those considering this product.
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Does sound like they are knock-off DS1307's - get a module from a reputable supplier.
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