Datalogger Shield RTC not working.

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Garrex
 
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Datalogger Shield RTC not working.

Post by Garrex »

Using the tutorial code, my data logger shield's RTC works properly when I have it hooked to the usb.

However, when I run it off battery, the time logged becomes "2165/165/165 165:165:85".

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adafruit_support_mike
 
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Re: Datalogger Shield RTC not working.

Post by adafruit_support_mike »

Just to check, do you have the GPS or non-GPS version of the Data Logger?

If it's the non-GPS version, do you have a coin cell in the carrier? The RTC needs that to work properly.

Garrex
 
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Re: Datalogger Shield RTC not working.

Post by Garrex »

It is the non-gps version, and I have a coin cell (the one provided with a kit) in there.

I have another Adafruit datalogger, and that one's RTC works fine on battery.

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adafruit_support_mike
 
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Re: Datalogger Shield RTC not working.

Post by adafruit_support_mike »

That's a good cross-reference, thank you.

This sounds like an issue with the supply power. If the clock works from one supply, we can't just write it off as a bad chip.

Double-check the coin cell's voltage, and post a photo of the shield running from battery power please. Let's see if the physical hardware gives us any clues.

Garrex
 
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Re: Datalogger Shield RTC not working.

Post by Garrex »

I've pinpointed the problem.

I am using a DC-DC converter to step down my input voltage (12V) to 5V. It actually steps down to 4.92V minimum. In my setup, I feed this into the Vin pin. The date&time are the 165/165/165.... It seems like if the input voltage is too low, it won't read the date & time..

If I feed the 12V directly into Vin, the date&time are right.

However, my other datalogger shield doesn't seem to have this problem.

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adafruit_support_bill
 
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Re: Datalogger Shield RTC not working.

Post by adafruit_support_bill »

It actually steps down to 4.92V minimum. In my setup, I feed this into the Vin pin.
If you are powering via VIN, theminimum voltage for reliable operation is 7v. VIN feeds the on-board 5v regulator and it needs at least 2vof headroom to properly regulate. If your DC/DC converter has god regulation, you can feed directly to the 5v pin - bypassing the on-board regulator.

Garrex
 
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Re: Datalogger Shield RTC not working.

Post by Garrex »

The issue is that using the 5v pin consumes significantly more current than the Vin pin. Feeding the converter output to the Vin pin, the Arduino draws around 50mA, while feeding to the 5v pin, it draws 80mA. In my project, current consumption is an concern, since it runs off battery.

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adafruit_support_bill
 
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Re: Datalogger Shield RTC not working.

Post by adafruit_support_bill »

The Uno itself will draw about 16-20mA @5v. The RTC is probably a few mA more. SD card writes can be 80-100mA or more depending on the card.

Running your 5v through the VIN pin will probably result in only about 3 to 4v on the 5v pin, meaning that the Atmega processor and the RTC are underpowered. You will loose a little less power through the 3.3v regulator to the SD card. But running the processor and RTC under-spec is not guaranteed to work.

Garrex
 
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Re: Datalogger Shield RTC not working.

Post by Garrex »

I see.

Running the Arduino off the 5v pin does indeed have the RTC time recorded properly. This issue can be marked as resolved.

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timtom
 
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Re: Datalogger Shield RTC not working.

Post by timtom »

Hello

I'm having an issue with the RTC on the datalogger shield (no GPS version, recently bought) on an Arduino Uno (R3). My code seems to "hang" when trying to access the RTC.
Thinking the issue was in my code or circuit, I tried running the sample code again with only the shield on, and it isn't working either. Nothing comes out through the serial port. I tried adding some debugging output and apparently, the device hangs after the rtc.begin(); call. This is strange, because last night with the exact same shield and code, it was working fine.

I have checked all connections between my shield and the Arduino. I checked for shorts between connections. Nothing. Based on some other issues reported with the RTC on the forums, I even cleaned my boards to remove any excess flux. Didn't help. I also measured the voltage at V_bat (coin battery input), it is 3.17V, so above the nominal 3V, should be OK (the battery is the one that came with the set and I only started using it last night, so should be new). I tried removing the coin battery for 30 min then trying everything again. No luck.

What am I doing wrong? Can I have fried the crystal or the RTC somehow? How can I check? I've attached some pictures of my (poor but apparently good enough) soldering job.

The SD card reader works fine. And my Arduino seems OK because it runs other projects OK. Any ideas?

Thanks!!
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adafruit_support_bill
 
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Re: Datalogger Shield RTC not working.

Post by adafruit_support_bill »

Which Arduino are you using?

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timtom
 
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Re: Datalogger Shield RTC not working.

Post by timtom »

It's a genuine Arduino Uno R3.

And sorry about the images being upside down, they were fine when I uploaded them (?).

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adafruit_support_bill
 
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Re: Datalogger Shield RTC not working.

Post by adafruit_support_bill »

Your soldering looks fine. Can you post a shot of the top of the board as well?

When did you purchase the shield?

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timtom
 
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Re: Datalogger Shield RTC not working.

Post by timtom »

The shield was purchased together with a group order from my makerspace this spring. I can find out the exact dates and references if required. Due to multiple other projects, I only started working on this one since earlier this week. In the meantime, the shield was still in its unopened original packaging.

Here's a view from the top
IMG_3449.JPG
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Thanks for your help!

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adafruit_support_bill
 
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Re: Datalogger Shield RTC not working.

Post by adafruit_support_bill »

No visible manufacturing issues on the top-side either.
The shield was purchased together with a group order from my makerspace this spring.
Unfortunately, our replacement policy is 30 days. But if you contact [email protected] with a link to this thread we can offer a discount on a replacement shield.

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