[time-nuts] RTC DS3231: how well can it be regulated?

[Kiwi Geoff]

MLewis wrote:
> It got me wondering. Between the DS3231's Aging Trim, insulating and
> perhaps a heater for some temperature control, does anyone know if the
> DS3231's PPS could be synced and stabilized into a reasonable PPS source
> through an opto-isolator?

Hi Michael,

Although not directly answering your question, I thought you may be
interested in some data I produced back in 2016.

At the time there were DS3231 based modules on aliexpress for a
ridiculous low price, so I bought quite a number of them. However I
was highly suspicious that they could be real or even work as a XO,
phony chips, broken or out of spec, etc etc.

So I powered one up, and compared the 1PPS to GPS, using room
temperature as the variable to see if they "worked".

I was pleasantly surprised to see YES my DS3231 modules were actual
TCXO's and they performed as I would expect. Note how the warming and
cooling rates follow slightly different paths, but you can clearly see
on the attached graph the TCXO changing to compensate for the room
temperature varying.

Readers on a higher pay scale than I, may see more than I see in the
attached graph.

It is on my long list of things to do, to play more with these modules
now my home has been rebuilt (hint - always pay your house insurance
;-)

Regards, Geoff , Christchurch, NZ
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