[time-nuts] iPhone keeping better time?
David J Taylor
david-taylor at blueyonder.co.uk
Wed Nov 16 16:18:22 UTC 2011
>> Yes, Miguel, someone did mention an NTP synched clock some time back,
>> and
>> I thought it might be a fun project. Based on an Arduino board IIRC?
>> Although I don't think it had Wi-Fi by default....
>
>
> I have it running at the moment. Have to build a case tough. See
> attached
> picture.
It looks very smart!
> It syncs at the 9th, 19th, 29th, ... second mark from a local GPS based
> NTP
> server.
>
> On every sync, the timestamp returned from the NTP server is on the 6 ms
> mark this means that the local clock of the Arduino drifts a lot.
6 ms per 10 s. Outside the 500 ppm allowed for NTP! <G>
> I am
> installing a realtime clock (Chronodot) this weekend that has an
> accuracy
> of +/- 3.5 ppm from -40C to 85C (I read somewhere that between 0 and 40C
> it
> is 2 ppm). This RTC can output a square wave signal at 1 Hz and Arduino
> can
> read that and use it to update the display at the exact second mark.
>
> With the RTC and synching every 10 minutes (9th, 19th, 29th, 39th, 49th
> and
> 59th of every hour) I expect a maximum error of 1.2 ms (based on 2 ppm).
> My
> eyes can't read that :-)
Nor mine! On my PC, the radio pips, and the hands on the analogue clock I
wrote, appear to be precisely in sync, but I expect that means within a
few tens of milliseconds.
> A neat feature I added is that when the clock can't synch it won't show
> a
> time. It will show -- : --.
Shouldn't that be the classic video recorder display? A flashing 00:00 or
whatever?
> I also have code that enables the user to telnet to the clock's IP
> address
> and change its setting which are saved in the Arduino EEPROM.
>
> If you are interested in a parts list and even the code I can send it to
> you next week as soon as I add the RTC
>
> The most interesting part is that buying a clock from Inova (
> http://www.inovasolutions.com/network-clocks/products/digital-network-clock.htm)
> would cost be 5 times more and it would not be as accurate as this one.
>
> Cheers,
> Miguel
Yes, I would be interested, but others might as well, so perhaps put it up
on the Web somewhere?
Cheers,
David
--
SatSignal software - quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk
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