Chronodots not working

[rvk]

We use the chronodots as a part of larger product. The most recent batch of Chronodots (Order # 964285-3653985996) are not working when tested in a circuit which works fine with a Chronodot from a previous order. We've used 30+ Chronodots in this same design previously without issue which is why we suspect a parts level defect.

Can we get these replaced? Is there a known issue with the Chronodot?

[adafruit2]

hmm thats odd. well, you can look for component level differences (e.g. one has a different valued resistor)
we dont manufacture these so the best way to get help is contacting macetech - designer & maker of the chronodots
http://macetech.com/store/index.php?mai ... contact_us

let us know what the response is, we're curious!

[rvk]

Sure, I can contact the manufacturer but can I also return these to Adafruit for credit? We purchased these non-working parts from you, not your supplier.

[adafruit2]

Sure, I can contact the manufacturer but can I also return these to Adafruit for credit? We purchased these non-working parts from you, not your supplier.

*maybe* they're nonworking...or they might be OK but something is not quite set up on your side the same. its really worth contacting them, they can advise!

[rvk]

This customer service approach hasn't been positive or constructive for me, but I hope it's at least been a nice time for your side of things.

We'll purchase a few more to see if we can get some working parts and also contact the manufacturer.

[rvk]

Just another update - we purchased three more units - of those one was also non-working and one worked fine. The third unit has not been used yet. So of the six most recently purchased, four are not working, one works perfect and one hasn't been tested yet.

Confirming, this is the correct channel for getting product support? I've also emailed Mactech as recommended.

[adafruit2]

product support for these is handled by macetech - we dont manufacture this product. have they replied?

if you post clear, detailed, non-blurry photos of your setup we can look at what could be the issue. also, explain clearly what 'isnt working' and what code you're using to test

[tn]

I have a ChronoDot V2.1 (purchased through Adafruit) in an alarm clock project with a Trinket and some mechanical relays for turning lights and such on and off. The project runs continually (power supply) and had been running fine for several months turning a light on and off every day.

Two times recently there has been a problem with timing. First time I thought it must have been a fluke and I just reprogrammed the uC and set the time on the RTC. This second time I was able to track down the problem to the RTC losing the correct date and time. The RTC somehow got reset back to year 2000.

The RTC has always had a battery in it and no programs were written to the uC prior to this happening.

I have contacted macetech. Has anyone heard of any other similar issues with the Chronodot? I will try to work through macetech for support but wanted to get comments here as well.

[Stripes9]

I have approx. 30 teensy devices running with Chronodots and often they will reset to the year 2000. We haven't figured out the solution yet it seems random although it is sometimes associated with us transporting the devices.

[Franklin97355]

@Stripes9, product support for these is handled by macetech - we don't manufacture this product. Have you tried contacting the maker?

[Stripes9]

Yes, I have contacted Macetech and am waiting for a reply just thought someone else here might have already solved the problem since it sounds like many people have the same problem. Thanks!

[Franklin97355]

No problem, just making sure you know all the options. Let's hope we get an answer as I have a few myself but have not used them in a while.

[macegr]

I'm talking with the above poster (posters?) and trying to track down the issue. Currently suspecting it may be related to batteries. Their project logs time and powerup events to an SD card, so we should be able to see if the time suddenly switched to year 2000, or if the reset was associated with a power cycle.

I'll note that their device has two gas sensors very close to the ChronoDot inside a small enclosure. Gas sensors use a heated catalytic element, and essentially this puts two 1-watt heaters next to the ChronoDot. While the DS3231 chip itself should be fine with this, the battery may react poorly to overheating (this remains to be tested). We have changed battery brands due to availability sometimes between production batches, so that could explain one batch working and followup batches exhibiting this problem.

The device PCB also does not have a ground plane and has very thin supply traces, so I am also concerned about susceptibility to external noise influence as well as power dropouts/brownouts. Power management may be something to check if anyone else is seeing this happen in their circuit.

The other poster above (tn) contacted us and we determined there were no pullup resistors in the circuit. They said they would try the pullup resistors and let us know if there were any more issues, we haven't heard anything since March so I assume that helped.

[tn]

**** MY PROBLEM SOLVED *****

I contacted macetech back in March 2016. They suggested I switch to the DS3231 specific library as I had been using the DS1307 one. "RTC_DS3231 rtc;” instead of “RTC_DS1307 rtc;” I was not aware of the library difference between the standard DS1307 and the more precise DS3231. Their second suggestion was to add external pull up resistors and I did not install these.

Since making this library change in March 2016, the project has been running continuously and up to today (November 2016) it has been keeping time perfectly. I wanted to get a good 6+ months of testing in before concluding that the problem has been fixed. This completely solved the problem I reported in my earlier post.

Adafruit: It would be great if you added a note on the Chronodot page of your website detailing the library issue.

macetech: Thank you again and for the others with issues, please be sure to give them everything you can (photos, your setup info, code) when requesting help. The fact that I see they linked up my request for help via email and my post on here is excellent customer service.

[macegr]

Another followup: The poster with the air quality sensors informed me that their sensors were not the type that used a high power heating element, so temperature was unlikely to be a problem. They did confirm that (since their application saves frequent logs) the ChronoDot reset events were all tied to power-loss events. More specifically, a ChronoDot wouldn't spontaneous reset in the middle of operation, but would rarely reset at the moment of an intentional or unintentional power cycle.

I found a small note in the DS3231 documentation describing a condition that could cause a loss of time data: application of -0.5V or lower to the device. It's not clear if this only applies to the power input, the data lines, or both. However, depending on how the power supply is designed, the specific arrangement of traces and filter components, etc, it seems possible that some circuits could apply -0.5V to the ChronoDot during a power-up cycle. There may be ringing on the power supply lines as power floods into the system and imbalances are gradually equalized (on the microsecond timescale of course).

Sticking to thick power traces and a star topology for power lines seems like it could help; minimizing power trace length to reduce inductance, and possibly using more power filtering capacitors and inrush limiting. Nothing new to successful PCB designs in any case. I plan to do some testing to see if I can trigger the ChronoDot memory reset intentionally, and make some specific design recommendations to prevent this occurrence.