Data logger shield not keeping time (sort of)

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ncarlie
 
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Data logger shield not keeping time (sort of)

Post by ncarlie »

So recently put together a data logger shield, and I'm getting odd behavior. I got the library installed fine and copied the code from the website that serial prints the date and time. It prints it fine, but the time and date it prints do not change so long at the board is powered on. If I remove DC power and then re-connect it, the same time still does not change. If I re-upload the program the time STILL does not change... but if I remove DC power and THEN re-upload the program, it changes to the new time before repeating as usual.


I have a feeling this is related to the coin cell battery and/or the resonator somehow. Is there any way I can check it?

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adafruit_support_bill
 
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Re: Data logger shield not keeping time (sort of)

Post by adafruit_support_bill »

Did you remember to put a blob of solder under the battery holder? It is required for good contact. Make sure that your battery is making good contact and is giving you about 3v.

If you have access to a scope or frequency counter, you can check that the crystal is oscillating as well.

ncarlie
 
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Re: Data logger shield not keeping time (sort of)

Post by ncarlie »

FWIW, I just checked the battery and it's dead (10mV). Not sure if it came that way or not. I also looked at the battery holder. Solder joints are fine, but there is only 734 ohms between the + and - terminals of the holder. Not sure if that's a normal value... the CR1220 is only a 40mAh battery so that would last like 10 hours.... guess maybe it's a partial short or something.

ncarlie
 
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Re: Data logger shield not keeping time (sort of)

Post by ncarlie »

Just got a new battery, and same result, but did not do the solder blob thing... I'll go try it.

ncarlie
 
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Re: Data logger shield not keeping time (sort of)

Post by ncarlie »

Nope, same result with solder blob. I read 0.4V between the + and - terminals on the back of the board.

ncarlie
 
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Re: Data logger shield not keeping time (sort of)

Post by ncarlie »

Actually, I can report one change. I cannot change the time at all now, even by re-uploading, unless I remove the battery.

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adafruit_support_bill
 
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Re: Data logger shield not keeping time (sort of)

Post by adafruit_support_bill »

Nope, same result with solder blob. I read 0.4V between the + and - terminals on the back of the board.
With a fresh battery, that is not normal. You may have a short somewhere. Post photos of the front & back of your board & we'll take a look for any assembly problems.

ncarlie
 
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Re: Data logger shield not keeping time (sort of)

Post by ncarlie »

Back of Board
Back of Board
Back.JPG (192.22 KiB) Viewed 1403 times
Front of board
Front of board
Front.JPG (241.89 KiB) Viewed 1403 times

The back is a bit out of focus... can't seem to get the camera to focus on it right.

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adafruit_support_bill
 
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Re: Data logger shield not keeping time (sort of)

Post by adafruit_support_bill »

there is only 734 ohms between the + and - terminals of the holder.
Are you measuring with the battery removed? Remove both the battery and the RTC chip and measure again. That is not right.

I don't see any obvious shorts in the photos.

ncarlie
 
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Re: Data logger shield not keeping time (sort of)

Post by ncarlie »

I did re-check it and get something like 30k ohms. I put it all back together and like magic it started working. No real idea why, but I'll take it.

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