[time-nuts] GPS for Nixie Clock

Vlad time at patoka.org
Tue Jul 12 13:50:59 EDT 2016

In addition, even MCU has not enough resources to handle TCP/IP, DHCP 
and NTP, it is some solutions available to outsource it to dedicated 
chips. I was using WIZ5100 (assembled as a modules) with great success.


On 2016-07-12 12:01, Chris Albertson wrote:
> What kind of micro processor are you using to run the Nixie tube clock? 
>  If
> that processor could run NTP you would not need GPS.   But of course 
> you
> could always do both.   GPS requires a view of the sky and maybe that 
> is
> not available in a multi story building unless near a window.  NTP 
> would be
> available any place there is WiFi.     Even without network connection, 
> is a good way to interface the GPS as it knows how to talk to most 
> GPSes
> made. can handle GPS outages (like when the clock is moved away from a
> window)
> That said, you are likely not using a uP big enough to run NTP as a 
> setup
> like that is about $40 vs. using a bare AVR chip for about $3.  But 
> even
> with the smaller uP you might think about having the chip keep it's own
> internal time and using GPS to discipline that internal time, much like 
> the
> way NTP works.   Basically the uP has a flywheel and GPS regulates it's
> speed.  Let's you handle holdover gracefully.
> If using NMEA sentences from GPS, remember that the NMEA standard 
> allows
> those senates to come out at any time during the second to which they
> apply.  In other words the sentence itself can be up to almost a second
> "off".
> If you are looking for a GPS for use indoors I think you don't care 
> about
> anything other then receiver sensitivity.  Without that you have 
> nothing,
> no signal.  It is more important than a few less nanoseconds of 
> uncertainty
> in the time solution.   So those ublox receivers look good.   I'm 
> looking
> to buy some for another application, mobile robots, I'll use GPS for 
> gross
> level navigation and it would be nice if it still worked indoors
> On Sun, Jul 10, 2016 at 10:24 PM, Mark Sims <holrum at hotmail.com> wrote:
>> The Jupiter receiver defaults to Motorola output, but can be switched 
>> to
>> Zodiac.  It talks at 9600:8:N:1
>> Frankly, it is the wrong receiver to use, particularly with an indoor
>> antenna.  I would go with a modern GPS receiver with standard NMEA 
>> output
>> and a 1PPS signal.   They are MUCH more sensitive and usually work 
>> indoors
>> and can be had for dirt cheap.   Most have an on-board ceramic patch
>> antenna.  Ublox receivers seem to work well indoors.
>> NAVSPARK makes a tiny little GPS board with 1PPS output.  6 for $36 or 
>> one
>> free for $10 shipping (no antenna supplied, has a U.FL connector).  It
>> speaks NMEA at 115,200:8:N:1  or can be setup for 9600 baud.
>> The delay between message and 1PPS is receiver dependent.  Usually it 
>> is
>> small enough to not be noticeable.  Some receivers send the message 
>> before
>> the 1PPS, others after it.   You can compensate for the 
>> differences/delays
>> in software.
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