Arduino Forum

Using Arduino => Displays => Topic started by: Randcook on Jan 03, 2014, 12:36 pm

Title: Economic?? RTC from ebay
Post by: Randcook on Jan 03, 2014, 12:36 pm
Purchased from fleabay...http://www.ebay.co.uk/itm/DS3231-AT24C32-IIC-Module-Precision-Real-Time-Clock-Memory-Module-For-Arduino-/300938576118?
Works and keeps time when connected,  when on battery (new one) it loses time badly.
The  boards does not appear to have a crystal?.. For refernce?

Any feedback welcome


Cheers
Peter
Title: Re: Economic?? RTC from ebay
Post by: manek100 on Jan 03, 2014, 12:50 pm
Look at the DS3231 datasheet. The crystal is integrated.
Title: Re: Economic?? RTC from ebay
Post by: MarkT on Jan 03, 2014, 09:46 pm
The blue ink splodge on the case is likely a factory-reject mark.  Sometimes stuff from
china/hong kong on eBay is rubbish/knock-off, that's how it is.  I know of a firm
that bought an X-ray machine to tell if the expensive chips they use contain a die
or not - saves wasting whole PCBs in production, and the entire shipment can be
rejected without opening.
Title: Re: Economic?? RTC from ebay
Post by: fungus on Jan 04, 2014, 01:53 pm

The blue ink splodge on the case is likely a factory-reject mark.  Sometimes stuff from
china/hong kong on eBay is rubbish/knock-off, that's how it is.  I know of a firm
that bought an X-ray machine to tell if the expensive chips they use contain a die
or not - saves wasting whole PCBs in production, and the entire shipment can be
rejected without opening.


Some of the fake chips have fake dies in them: https://www.sparkfun.com/news/350  :)
Title: Re: Economic?? RTC from ebay
Post by: JChristensen on Jan 04, 2014, 02:07 pm

I know of a firm that bought an X-ray machine to tell if the expensive chips they use contain a die or not - saves wasting whole PCBs in production, and the entire shipment can be rejected without opening.


I'd think that firm's sourcing methods would be open to question.
Title: Re: Economic?? RTC from ebay
Post by: fungus on Jan 04, 2014, 03:37 pm


I know of a firm that bought an X-ray machine to tell if the expensive chips they use contain a die or not - saves wasting whole PCBs in production, and the entire shipment can be rejected without opening.


I'd think that firm's sourcing methods would be open to question.


Yep. If you're using 'expensive' chips then you should be buying from reputable places and have a quality control system to prevent big production runs using bad components.
Title: Re: Economic?? RTC from ebay
Post by: Randcook on Jan 04, 2014, 06:41 pm
OK caveat emptor
Title: Re: Economic?? RTC from ebay
Post by: JChristensen on Jan 04, 2014, 08:23 pm

Yep. If you're using 'expensive' chips then you should be buying from reputable places and have a quality control system to prevent big production runs using bad components.


If I were buying "expensive" chips (or any other kind, really), my expectation would be that the manufacturer would have sufficient QC in place that I would not need to do incoming inspection and they should, as a regular matter of course, be able to demonstrate this with appropriate statistical analysis. They should have a formal quality system based on ISO9001 or whatever the current craze is.
Title: Re: Economic?? RTC from ebay
Post by: K5CZ on Jan 05, 2014, 12:06 pm

Works and keeps time when connected,  when on battery (new one) it loses time badly.

I own two of these modules (not purchased on eBay). Both are in operation for several months. Works on both Vcc and the battery power. Accuracy is admirable, much better than in the datasheet (approximately less than a second per month). So I am very satisfied.

Your module must be defective. Do you have performed measurements, whether it is good contact between the battery and the chip / ground?
Title: Re: Economic?? RTC from ebay
Post by: cjdelphi on Jan 05, 2014, 12:10 pm
You know what, I have several of these and other ic's for time keeping and each day they would drift a minute or so...

So I connected a lithium (old samsung battery) and in 3 days it was  pretty much accurate!

I blame coin cell batteries!
Title: Re: Economic?? RTC from ebay
Post by: Randcook on Jan 05, 2014, 08:40 pm
I have replaced the battery, with a new one, but will investigate...
Title: Re: Economic?? RTC from ebay
Post by: MarkT on Jan 05, 2014, 09:21 pm


I know of a firm that bought an X-ray machine to tell if the expensive chips they use contain a die or not - saves wasting whole PCBs in production, and the entire shipment can be rejected without opening.


I'd think that firm's sourcing methods would be open to question.


I can ask again about the issues, I doubt they would have gone to these
lengths without good reason.
Title: Re: Economic?? RTC from ebay
Post by: dannable on Jan 05, 2014, 10:09 pm
I've got a 1307 based clock module (China, cheap) which has been laid around in the kitchen for the last nine months running off the battery. When I've tried it out today it has only gained about three minutes which came as a surprise. It doesn't have a regular watch crystal in a metal case, rather a white ceramic looking item.