[SOLVED] Real time Clock DS3231 (mounted on shield) runs too slow

Based on the datasheet, I bought a (in principal) very accurate DS3231-shield.
I use the RTClib.h; all can use all functions.

But: Each day it runs 2 MINUTES TOO SLOW.

Has anyone experience wit this inaccuracy of the DS3231?
What can happen?

What are you comparing it too? Maybe the other device is two minutes fast?

I am compairing the time of my PC (connected to WLAN) with the time of the RTS3231-shield.

Yes, it was a bad part. I compared it to Universal Standard Time and the gain (in my case) was additive so it got worse every day by an incremental amount. Before you blame the part be sure your time standard is correct. In minutes like you are stating a cell phone would do just fine.

eBay fake perhaps?

I've been monitoring one of these for some time now, the temperature controlled crystal version, and check the time each day at exactly the same time either using an MSF clock or the phone.
There is a website called Time that will check the PC time against their standard.
I've never found a DS3231 that keeps anything like a second either way over a month or so, but 2-minutes a day, there's got to be something really amiss.
It really does pay when starting out with something like this to get either the chip or a breakout board from a reputable distributor or module supplier like Adafruit.
You'll pay a bit more, but you can have some confidence that it's a genuine chip.

I bought a couple of bare DS3231 (SOIC-8) chips from Ali and they have been pretty accurate, considering that I got it for about 1$ per chip. The same chips from Mouser costs about 7$ each.

It is possible to calibrate the ds3231 although 2 minutes per day may lie outside the adjustment range. For fine adjustment, you need some professional test equipment.
http://www.kerrywong.com/2014/07/19/ds3232-clock-frequency-calibration/

Assuming you are using it correctly and not, for example, simply seeing the Arduino system time, where such a drift would be expected, l’d throw that one away as a probable a reject.

hzrnbgy:
I bought a couple of bare DS3231 (SOIC-8) chips from Ali and they have been pretty accurate, considering that I got it for about 1$ per chip. The same chips from Mouser costs about 7$ each.

Clearly fakes then - the real ones are probably calibrated during manufacture, one reason for
a chip being more expensive than typical chips (laser trimmed opamps are another case where
the cost will higher due to the separate manufacturing step).

Must have been, but they are fairly accurate to what I need them for so I'm not complaining.

My old DS3231-shield (which ran too slow) was a bad one.

I put it away and changed it by another one: now it runs very accurate. Problem solved!

This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.