[time-nuts] More ES100 WWVB Measurements
Brooke Clarke
brooke at pacific.net
Wed Jan 2 21:51:01 UTC 2019
Hi Wayne:
The problem is that when and how DST is implemented is a political decision at the state level. When those rules that
apply today are implemented in firmware (easy to do) the product tells the wrong time when those rules change.
In the case of the Heathkit GC-1000 the DST firmware changed the time when Colorado changed, but for me in California
that clock was wrong twice a year for a couple of hours.
https://www.prc68.com/I/HeathkitGC1000.shtml
--
Have Fun,
Brooke Clarke
https://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.
-------- Original Message --------
> > GPS has no bits for Daylight Savings
>
> It isn't that hard to compute when DST changes and GPS has the advantage that, since it also knows position, a wall
> clock could also automatically set the timezone, much as our cellphones do.
>
> > Has anybody looked into how much code it takes to implement DST?
>
> In my WWVB generator for Arduino it took me about about 15 lines of C code and a small table (daysToMonth[]). The main
> function is getNthSundayOfMonth() which, in turn, use two other functions, getDayOfYear() and isLeapYear(). The
> daysToMonth[] table is used by getDayOfYear(). Then, the main code uses getNthSundayOfMonth() to get the 2nd Sundays
> of MARCH and NOVEMBER.
>
> Wayne
>
> On Tue, Jan 1, 2019 at 12:34 PM Brooke Clarke <brooke at pacific.net <mailto:brooke at pacific.net>> wrote:
>
> Hi Wayne:
>
> DST.
>
> GPS has no bits for Daylight Savings. As far as I know only WWV and WWVB have those bits.
> So for a clock displaying local time WWVB is the way to go.
>
> --
> Have Fun,
>
> Brooke Clarke
> https://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> axioms:
> 1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
> 2. Everybody, with no exceptions, holds false beliefs.
>
> -------- Original Message --------
> > While reading this thread and pondering whether to buy and fool around with
> > an ES100-based module from Universal Solder, I suddenly found myself
> > wondering if there was any advantage to using the time received from WWVB
> > vs just using an inexpensive GPS receiver. The ES100 module costs about
> > $70, but I can get a GPS receiver, with antenna, for far less than that and
> > I've had no trouble receiving GPS signals indoors with most modern receiver
> > modules.
> >
> > I suppose the low power requirements of the ES100 might be an advantage
> > when building battery powered clocks to mount on the wall, but it seems
> > like some of the newer, ultra low power GPS modules intended for use in
> > smart watches could also work in a battery-powered wall clock, especially
> > if the receiver was only powered on a few times a day to update the time.
> >
> > And, finally, if GPS modules are (or will some become) a suitable
> > replacement for WWVB receiver modules, do we really need WWVB in the modern
> > age? Perhaps there's some critical advantage to using WWVB to get the time
> > but, offhand, I cannot think of it. What am I missing?
> >
> > Wayne
> >
> > On Mon, Dec 31, 2018 at 4:30 PM Brooke Clarke <brooke at pacific.net <mailto:brooke at pacific.net>> wrote:
> >
> >> Hi Joseph:
> >>
> >> Thanks for the patent link. I've added it to my WWVB phase modulation
> >> info at:
> >> https://prc68.com/I/Loop.shtml#La_Crosse_UltrAtomic
> >>
> >> --
> >> Have Fun,
> >>
> >> Brooke Clarke
> >> https://www.PRC68.com
> >> http://www.end2partygovernment.com/2012Issues.html
> >> axioms:
> >> 1. The extent to which you can fix or improve something will be limited by
> >> how well you understand how it works.
> >> 2. Everybody, with no exceptions, holds false beliefs.
> >>
> >> -------- Original Message --------
> >>> On Mon, 31 Dec 2018 12:00:02 -0500, time-nuts-request at lists.febo.com <mailto:time-nuts-request at lists.febo.com>
> >>> wrote:
> >>>
> >>>> time-nuts Digest, Vol 173, Issue 44
> >>>> Message: 7
> >>>> Date: Mon, 31 Dec 2018 04:04:22 -0800
> >>>> From: "Tom Van Baak" <tvb at LeapSecond.com>
> >>>> To: "Discussion of precise time and frequency measurement"
> >>>> <time-nuts at lists.febo.com <mailto:time-nuts at lists.febo.com>>
> >>>> Subject: Re: [time-nuts] More ES100 WWVB Measurements
> >>>> Message-ID: <96BB388753294278A9CDE96C1EA7D9AE at pc52>
> >>>> Content-Type: text/plain; charset="UTF-8"
> >>>>
> >>>> Hi Graham,
> >>>>
> >>>> That's very nice work. And you have uncovered several unusual effects
> >>>> in the ES100. Bugs? Features? If we time nuts keep up the good work
> >>>> to evaluate this chip, we are likely at some point to get an
> >>>> informative response from the guys who designed it. They read
> >>>> time-nuts.
> >>> I didn't see this mentioned, but I think I have found the relevant US
> >>> patent application: US20130051184A1, Real-time clock integrated circuit
> >>> with time code receiver, method of operation thereof and devices
> >>> incorporating the same, Oren Eliezer et al, Oren Eliezer et al, filed
> >>> 2013-02-28.
> >>>
> >>> .<https://patents.google.com/patent/US20130051184>
> >>>
> >>> Found this by chasing stuff from the EverSet website:
> >>> .<
> >> http://everset-tech.com/wp-content/uploads/2014/11/ReceiverRadioClocks.pdf
> >>> .
> >>>
> >>> Joe Gwinn
> >>>
> >>>
> >>>> So now both you and Tim have observed the off-by-one-second (or
> >>>> off-by-N-seconds) effect in the ES100. I wonder if this explains why
> >>>> some of my ES100-based La Crosse 1235UA Ultratomic wall clocks are
> >>>> off by a second sometimes.
> >>>>
> >>>> My main question: in your "Time Plot.PNG" plot, what is the cause of
> >>>> the sawtooth pattern? The points are almost all on a clear negative
> >>>> slope, though bounded by roughly +/- 75ms. Looking on the far left, I
> >>>> see a time drift of +50 ms to -25 ms over an hour, which is
> >>>> equivalent to a -20 ppm frequency offset; about -2 seconds/day.
> >>>>
> >>>> Do you think this is due to the 16 MHz onboard xtal? If so, how about
> >>>> changing the temperature of the eval board by a lot (say, several
> >>>> tens of degrees) for an extended time (say, 4 hours) and see if the
> >>>> sawtooth slope changes convincingly.
> >>>>
> >>>> Also, just to be sure, can you put a known independent timing signal
> >>>> (e.g., GPS/1PPS) into your complex BeagleBone Black / Debian 9.4 /
> >>>> ntpd time server / Python 3 / Excel stack to establish the validity
> >>>> of your measurement methodology? Very likely you did it right, but I
> >>>> always cringe when I hear "Linux" or "NTP" and "precise time" in the
> >>>> same sentence. Yes, sorry, forgive me; I grew up in the "trust, but
> >>>> verify" generation [1]. It applies pretty well to metrology also ;-)
> >>>>
> >>>> /tvb
> >>>>
> >>>> [1] https://en.wikipedia.org/wiki/Trust,_but_verify
> >>>>
> >>>>
> >>>> End of time-nuts Digest, Vol 173, Issue 44
> >>>> ******************************************
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