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Comment by bubblethink | Hacker News Reader

Cool project, but with this sort of power and area budget, can't we use chip scale atomic clocks ? Also, the quartz accuracy is listed as 1000 seconds to drift 1 millisecond. So that's 31 secs a year ? That's less than HAQ quartz watches (+- 5 secs a year) and definitely less than Citizen 0100 (+-1 sec a year).

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The clock is synchronized to the GPS time signal. So the quartz accuracy is only for when you have no GPS signal, or between synchronizations.

Yes, I get that, but that is less interesting. Any clock can sync to GPS or NTP. It would be cooler to have an autonomous accurate clock if you are making a giant device with an ARM chip, flash storage etc.

I wouldn’t know how to obtain a clock that synchronizes to GPS. I’ve had situations in the past where it would have been useful to have such a clock for checking at a glance if the NTP server is screwing me up, or when you’re offline.

If you want a commercial GPS wall clock, Seiko makes several models. I have one - GP502W. They make others too. They are JDM models though, so you'll have to order one from Japan.

Thanks. Do you know if it automatically adjusts to the local time zone?

No, it doesn't. You need to set the offset to UTC manually. You also need to set the dates when daylight savings start and end if you live in a place that that uses daylight savings. But it runs on batteries that last for 3 years, so it's very low maintenance.

In the continental US it can be more convenient to get a clock that syncs to WWV, since it works without an external antenna. WWV is accurate to within 100ns, though you'll have propagation delays depending on your position in the US (I'm 50 miles from the station).

The reception of radio signals tends to be worse and more sensitive to your location. There was also talk of decommissioning them.

This is a good place to start: https://news.ycombinator.com/item?id=44145770

There is another project out there using a BeagleBone Black plus a small hardware RTC and a GPS module hooked up over GPIO/serial. The advantage there is that the BBB supports hardware PTP timestamping on its built-in NIC. I threw one together over a weekend, just need to design up a small box to hold it all in (though the cable mess of jumpers also made me want to design an interposer board to clean things up)

Aren't they significantly more expensive, $5k?

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