[time-nuts] Grandfather clock sync'd to 1PPS (from time-nuts Digest, Vol 200, Issue 4)
Philip Gladstone
pjsg-timenuts at nospam.gladstonefamily.net
Wed Mar 10 15:43:19 UTC 2021
I've been wanting to do this as well, but I feel that it is "cheating" to
actively drive the pendulum. I want to have a passive approach to
disciplining the clock so that the clock itself is keeping time.
One approach that I have seen was to put a magnet at the bottom of the
pendulum and then have a metal plate beneath it -- and the correction is
performed by adjusting the vertical position of the plate. This effectively
changes the local gravity and hence the tick period. However, I don't think
that this will look "nice". I'm hoping that I can do the same magnet trick,
but put it much higher on the pendulum so that it is hidden when you open
the clock case door. I envisage having the metal plate position being
controlled by a small stepper motor. I'd like to have a range of maybe
+/-50ppm with a resolution of around 1ppm. This seems doable....
Thoughts?
Philip
On Sat, Mar 6, 2021 at 2:12 PM Gerald Swann <gds32571 at gmail.com> wrote:
> Eamonn and all,
>
> You mentioned you hope to get your grandfather clock time synchronized
> to a 1PPS signal. That would be a very satisfying project, I can assure
> you. I did that with my own grandfather clock. My father built the clock
> quite a number of years ago from a kit, and used walnut wood from a tree
> that was harvested from somewhere in Indiana to build the actual clock
> body.
>
> On github at https://github.com/gds32571/gdsPendulum you can see the
> operating code for the Arduino-based controller that performs this feat.
> There are lots of comments within the code, but I don't want to leave that
> as the only info to help you understand, so some explanation follows.
> Within the README.md file are links to pictures and to a graph showing data
> regarding the pendulum swing.
>
> There were several interesting descriptions of how one might use a
> magnet to influence the swing of the pendulum. I took an approach not
> mentioned in the digest email. For a simple pendulum, only two factors
> affect the period: the length of the pendulum and the gravity field the
> pendulum is swinging in.
>
> I fastened a steel screw held in an alligator clip to the bottom of the
> pendulum, and then adjusted the pendulum weight so that the pendulum would
> swing a little slower than necessary to keep time. I took the coil from a
> 24v relay and mounted it on a cardboard rack sitting in the bottom of the
> clock cabinet such that the steel screw swings just above the core of the
> relay coil. This relay coil, when energized, has the effect of slightly
> increasing the attraction of the pendulum towards the center of earth -
> more gravity you might say.
>
> The same cardboard rack holds a blue LED and a phototransistor
> (TEPT5600) such that the light from the LED shines on the phototransistor.
> The weight attached to the end of the pendulum, blocks the light every
> swing. This generates a signal I use to measure the phase of the pendulum
> relative to the 1PPS signal.
>
> When I started thinking about this, I thought I could use some fancy
> timing to generate pulses that could speed up or slow down the pendulum, as
> I desired. That was not to be, at least within my ability, the pendulum
> can only be sped up. So I just measure the phase of the pendulum relative
> to the 1PPS and energize the coil if the pendulum is lagging behind. The
> arduino controller energizes the coil for a number of seconds each minute.
> In the graph, you can see that the magnetism time is 19 beats for this
> minute.
>
> I didn't notice before I started this project, the pendulum period is
> not 2 seconds as I would have expected. It actually swings 33 times in one
> minute, giving a period of 1.81818 seconds. This means that the phase
> measurement of the swing will line up with only one pulse from the GPS
> every ten seconds.
>
> The arduino outputs a text message once a minute with some control info
> including the phase, the time spent energizing the magnet, etc. This
> serial output from the arduino feeds a Raspberry Pi that generates the
> stats graph.
>
> The green plot line is the measured phase difference. You might think
> the clock was off by 800 milliseconds, but actually it is sync'd to the
> 1PPS pulse that occurs just before the top of the minute. So, right now,
> the clock time rolls over about 182 milliseconds before the top of the
> minute. That's also why the GPS time shows as one second before the GFC
> time. You can also see the clock phase has slipped somewhat when I wound
> the clock yesterday morning (27 hours ago). If I play with the setting of
> the clock, I can get the phase difference to within a few milliseconds.
> And it will stay there for weeks.
>
> The Arduino controller has been running for 37 days this time, since it
> was last reset. It is not super accurate compared to many GPS clocks, but
> it will be as correct as anyone can read the minute and hour hands. But,
> if I forget to wind the clock, the driving weight will hit the cardboard
> rack and stop the clock. So I get a chance to set it again.
>
> One more thing, the "Big Ben" style chiming mechanism built into the
> grandfather clock has some broken pins, so it skips some of the notes in
> the quarter hour and top of the hour chiming. To avoid this, I added a
> midi synthesizer to the controller. The clock now chimes electronically.
> There is also a PIR sensor to sense motion so that the clock can lower the
> chime volume if someone is in the same room as the clock.
>
> The grandfather clock face time is unaffected by any of the circuits I
> added, so it continues to display the time as you would expect. There is
> also a seven segment display connected to the Arduino controller that
> displays the time digitally, counting pendulum swings.
>
> I also have two more Arduino clocks on the same table. One displays the
> time extracted from the NMEA sentences sent from a second GPS. The other
> Arduino clock counts the 1PPS pulses from the first GPS and displays the
> accumulated time on its own display. I originally used a Motorola Oncore
> GPS UT+ I think it was, which was rock solid, never missing a pulse. Now,
> I am using an Adafruit GPS mounted in the middle of the room, not near a
> window. It will occasionally drop pulses which confuses the clock
> controller. So the Arduino program running this clock generates the missing
> 1PPS pulses to keep the GFC controller happy. Seems to work.
>
> The circuitry is very simple, but I do not have a schematic. It's just
> a couple of transistors and the Arduino. I hope to do a better job of
> documenting this project in the coming months I hope you found
> this interesting and I haven't taken up too much of your time.
>
> Thanks,
>
> Gerald
> AI4DE
>
> On Wed, Mar 3, 2021 at 12:00 PM <time-nuts-request at lists.febo.com> wrote:
>
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> > When replying, please edit your Subject line so it is more specific
> > than "Re: Contents of time-nuts digest..."
> >
> >
> > Today's Topics:
> >
> > 1. Re: Old Crystal. (Bob kb8tq)
> > 2. World's most precise.... wall clock (Eamonn Nugent)
> > 3. Re: World's most precise.... wall clock (Bill Beam)
> > 4. Re: World's most precise.... wall clock (ed breya)
> > 5. NPL courses on time and frequency measurement (Dr. David Kirkby)
> > 6. Re: World's most precise.... wall clock (Lux, Jim)
> > 7. Re: World's most precise.... wall clock (Tom Van Baak)
> > 8. Re: World's most precise.... wall clock (DM)
> > 9. Re: World's most precise.... wall clock (Hal Murray)
> > 10. Re: World's most precise.... wall clock (David Taylor)
> > 11. Re: World's most precise.... wall clock (Attila Kinali)
> > 12. Re: World's most precise.... wall clock (Edesio Costa e Silva)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Tue, 2 Mar 2021 12:37:09 -0500
> > From: Bob kb8tq <kb8tq at n1k.org>
> > To: Discussion of precise time and frequency measurement
> > <time-nuts at lists.febo.com>
> > Subject: Re: [time-nuts] Old Crystal.
> > Message-ID: <E982F541-5591-4E81-B7E0-5C875539047F at n1k.org>
> > Content-Type: text/plain; charset=utf-8
> >
> > Hi
> >
> > You don?t necessarily need to convert to a 12.5 ohm system. A lot
> depends
> > on
> > just what your objectives are.
> >
> > It a bit like needing a fancy Fluke Hart Chub thermometer if you are only
> > after
> > a couple of degree accuracy. The tools vary depending on the job.
> >
> > Bob
> >
> > > On Mar 1, 2021, at 3:23 PM, EB4APL <eb4apl at gmail.com> wrote:
> > >
> > > My response got lost in the Internet, so I repeat the info.
> > >
> > > If you have access to a Network Analyzer, either Scalar or Vector, you
> > can measure the crystal parameters. You need a test fixture (it could be
> > homemade) to convert the 50 Ohm analyzer impedance to 12.5 Ohm and you
> very
> > slowly sweep the crystal to obtain its serial resonance (frequency and
> > attenuation) the and the -3dB points frequencies. From these measurements
> > there are simple formulas to obtain the motional resistance, inductance
> and
> > capacitance, and the crystal Q.
> > >
> > > Some professional Network Analyzers seems not to be very adequate to do
> > this because they cannot sweep slowly enough, but some low cost hobby
> type
> > analyzers have a mode for measuring crystals with these calculations
> > integrated. One example being the Poor Ham Scalar Network Analyzer which
> > has a function for specifically measuring crystals using a step rate of 1
> > Hz and the nanoVNA, that can measure the resonance point and you do the
> > calculations. A program with the measurements and calculations integrated
> > is under development at this time.
> > >
> > > This an example of the PHSNA output:
> > >
> > > Crystal Id: 8 Mhz #3
> > > Peak Frec. (Hz): 7996356
> > > Bandwidth (Hz): 354,5
> > > Rs (Ohm): 24,3
> > > Lm (mH): 22,13353409
> > > Cm (pF): 0,01789803
> > > Q: 45763
> > >
> > > Regards,
> > >
> > > Ignacio EB4APL
> > >
> > >
> > > El 01/03/2021 a las 0:35, Dan Kemppainen escribi?:
> > >> Hi All,
> > >>
> > >> I've picked up a couple of old crystals. Mostly because they look
> neat.
> > They are 1Mhz, in a glass tube. The quartz is ~25mm dia, at about 1 mm
> > thick. Was able to get them to oscillate using a Colpitts circuit. They
> > will oscillate at 2.851Mhz (probably some strange mode) if given the
> > chance.
> > >>
> > >> I've been scouring my reference books here, and haven't had much luck
> > finding any details on how one would even guess at the parameters of a
> > quartz like this.
> > >>
> > >> There area few numbers on them, 33 stamped on the side, 1000 (KHz???)
> > on the top, 87 on the top, and hand written 501 (probably a SN). Digging
> on
> > line, I'd guess an AT cut based on thickness. I'm guessing the 33 is
> > capacitance in pF. 87, might be year.
> > >>
> > >> If any of you have any suggestions on where to find information on how
> > to get something like this to oscillate properly, guess at correct
> > parameters, or even measure any of the parameters I would really
> appreciate
> > it.
> > >>
> > >> I'm sure these are really nothing special, but it would be neat to
> give
> > them a fighting chance to show what they can or can't do without breaking
> > them!
> > >>
> > >> Thanks,
> > >> Dan
> > >
> > > --
> > > El software de antivirus Avast ha analizado este correo electr?nico en
> > busca de virus.
> > > https://www.avast.com/antivirus
> > >
> > >
> > > _______________________________________________
> > > time-nuts mailing list -- time-nuts at lists.febo.com
> > > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > > and follow the instructions there.
> >
> >
> >
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Tue, 2 Mar 2021 17:38:24 -0500
> > From: Eamonn Nugent <elg.nugent at gmail.com>
> > To: time-nuts at lists.febo.com
> > Subject: [time-nuts] World's most precise.... wall clock
> > Message-ID:
> > <CAPQA=
> > kH+B87DQQVTkWnrh+9y_d2udRh58-KpkdYha7zZamdnZg at mail.gmail.com>
> > Content-Type: text/plain; charset="UTF-8"
> >
> > Hi!
> >
> > I have a perhaps silly question. I want to take an inferior medium (our
> > eyes) and give it something attractively precise to look at. Is there
> such
> > a thing as a digital (wall) clock with a 1PPS/10MHz/etc. input? I see
> that
> > some clocks have GPS antenna inputs, but I want to take a GPSDO and hook
> it
> > up to a digital clock. Purely for fun, as a mini project for myself
> while I
> > build my bigger clocks.
> >
> > Maybe one day I'll make this work with a grandfather clock.
> >
> > Thanks,
> >
> > Eamonn
> >
> >
> > ------------------------------
> >
> > Message: 3
> > Date: Tue, 02 Mar 2021 15:16:58 -0900
> > From: "Bill Beam" <wbeam at gci.net>
> > To: "Eamonn Nugent" <elg.nugent at gmail.com>, "time-nuts at lists.febo.com"
> > <time-nuts at lists.febo.com>
> > Subject: Re: [time-nuts] World's most precise.... wall clock
> > Message-ID: <E9.43.19889.E75DE306 at smtp01.beryl.bos.sync.lan>
> > Content-Type: text/plain; charset="us-ascii"
> >
> > Hi,
> >
> > I had same question several years ago.
> >
> > You're gonna have to roll your own.
> >
> > Look here <https://hassam794.weebly.com/digital-clock-using-4026-ic.html
> >
> >
> >
> >
> > On Tue, 2 Mar 2021 17:38:24 -0500, Eamonn Nugent wrote:
> >
> > >Hi!
> >
> > >I have a perhaps silly question. I want to take an inferior medium (our
> > >eyes) and give it something attractively precise to look at. Is there
> such
> > >a thing as a digital (wall) clock with a 1PPS/10MHz/etc. input? I see
> that
> > >some clocks have GPS antenna inputs, but I want to take a GPSDO and hook
> > it
> > >up to a digital clock. Purely for fun, as a mini project for myself
> while
> > I
> > >build my bigger clocks.
> >
> > >Maybe one day I'll make this work with a grandfather clock.
> >
> > >Thanks,
> >
> > >Eamonn
> > >_______________________________________________
> > >time-nuts mailing list -- time-nuts at lists.febo.com
> > >To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > >and follow the instructions there.
> >
> >
> > Bill Beam
> > NL7F
> >
> >
> >
> >
> >
> >
> > ------------------------------
> >
> > Message: 4
> > Date: Tue, 2 Mar 2021 16:32:47 -0800
> > From: ed breya <eb at telight.com>
> > To: time-nuts at lists.febo.com
> > Subject: Re: [time-nuts] World's most precise.... wall clock
> > Message-ID: <603ED92F.1030009 at telight.com>
> > Content-Type: text/plain; charset=utf-8; format=flowed
> >
> > If you can open it up and get at and identify the crystal, you can
> > synthesize its ideal frequency from a GPSDO output, then run it in there
> > in place of the crystal.
> >
> > Ed
> >
> >
> >
> > ------------------------------
> >
> > Message: 5
> > Date: Wed, 3 Mar 2021 00:45:43 +0000
> > From: "Dr. David Kirkby" <drkirkby at kirkbymicrowave.co.uk>
> > To: "time-nuts at lists.febo.com" <time-nuts at lists.febo.com>
> > Subject: [time-nuts] NPL courses on time and frequency measurement
> > Message-ID:
> > <
> > CANX10hDyPo4mG2-LVCo7_NBzgQ4A4GAt9uWkkKjUdYVvGf71qg at mail.gmail.com>
> > Content-Type: text/plain; charset="UTF-8"
> >
> > It looks like NPL are in the process of creating some courses on this.
> > Introduction to Time and Frequency Measurement
> > https://elearning.npl.co.uk/enrol/index.php?id=53
> >
> > I think I read something on the NPL site to imply that was free, but I
> > can't see that now. Anyway, it's not available yet, but it is obvious
> they
> > intend producing some courses.
> >
> >
> > ------------------------------
> >
> > Message: 6
> > Date: Tue, 2 Mar 2021 17:17:38 -0800
> > From: "Lux, Jim" <jim at luxfamily.com>
> > To: time-nuts at lists.febo.com
> > Subject: Re: [time-nuts] World's most precise.... wall clock
> > Message-ID: <586e610a-b13f-4872-a26e-9930fd0df3aa at luxfamily.com>
> > Content-Type: text/plain; charset=utf-8; format=flowed
> >
> > On 3/2/21 4:32 PM, ed breya wrote:
> > > If you can open it up and get at and identify the crystal, you can
> > > synthesize its ideal frequency from a GPSDO output, then run it in
> > > there in place of the crystal.
> >
> >
> >
> > I did this for a 24hr Mars clock using a 3325 to generate 31947.2745 Hz
> >
> >
> >
> >
> >
> > ------------------------------
> >
> > Message: 7
> > Date: Tue, 2 Mar 2021 17:27:15 -0800
> > From: Tom Van Baak <tvb at LeapSecond.com>
> > To: time-nuts at lists.febo.com
> > Subject: Re: [time-nuts] World's most precise.... wall clock
> > Message-ID: <a88d22d6-4400-8725-fa7d-3961c41fcd60 at LeapSecond.com>
> > Content-Type: text/plain; charset=utf-8; format=flowed
> >
> > Eamonn,
> >
> > Here are a couple of ideas for you:
> >
> > 1) You may find some GPS / NTP / 1PPS / 10 MHz precise time friendly
> > professional clocks at:
> >
> > https://www.masterclock.com/
> >
> > 2) If you have a 50/60 Hz mains wall clock you can always use this trick:
> >
> > http://leapsecond.com/pages/atomic-nixie/
> >
> > 3) You can convert your perfect 10 MHz into perfect 32.768 Hz and inject
> > that into any cheap 32 kHz tuning fork clock. Sometimes it's as simple
> > as one wire. Watch one for one problem: some newer 32 kHz clocks use
> > cycle slipping in which case feeding in exactly 32768 Hz will result in
> > a very slight loss of time as far as the hands show.
> >
> > A $1 solution to converting 10 MHz to 32 kHz is:
> >
> > http://leapsecond.com/pic/src/pd30.asm
> > http://leapsecond.com/pic/picdiv.htm
> >
> > 4) You can convert your perfect GPS/1PPS into the bipolar stepper
> > signals used by the Lavet motor in almost all analog wrist / desk / wall
> > clocks:
> >
> > https://en.wikipedia.org/wiki/Lavet-type_stepping_motor
> > http://leapsecond.com/pages/32kHz/
> >
> > 5) If you want sidereal time, another $1 PIC solution, see PD28 and PD29
> > at:
> >
> > http://leapsecond.com/pic/src/
> >
> > This technique can be adapted to a wide range of frequencies.
> >
> > 6) Projects to hack / adapt display clocks to Rb or Cs or GPS/GPSDO
> > timing sources is not uncommon on sites like Hackaday.com so have a look
> > there as well.
> >
> > /tvb
> >
> > On 3/2/2021 2:38 PM, Eamonn Nugent wrote:
> > > Hi!
> > >
> > > I have a perhaps silly question. I want to take an inferior medium (our
> > > eyes) and give it something attractively precise to look at. Is there
> > such
> > > a thing as a digital (wall) clock with a 1PPS/10MHz/etc. input? I see
> > that
> > > some clocks have GPS antenna inputs, but I want to take a GPSDO and
> hook
> > it
> > > up to a digital clock. Purely for fun, as a mini project for myself
> > while I
> > > build my bigger clocks.
> > >
> > > Maybe one day I'll make this work with a grandfather clock.
> > >
> > > Thanks,
> > >
> > > Eamonn
> > > _______________________________________________
> > > time-nuts mailing list -- time-nuts at lists.febo.com
> > > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > > and follow the instructions there.
> > >
> >
> >
> >
> >
> > ------------------------------
> >
> > Message: 8
> > Date: Tue, 2 Mar 2021 21:41:47 -0500 (EST)
> > From: DM <dgminala at mediacombb.net>
> > To: Discussion of precise time and frequency measurement
> > <time-nuts at lists.febo.com>
> > Subject: Re: [time-nuts] World's most precise.... wall clock
> > Message-ID:
> > <684600294.21613154.1614739307850.JavaMail.zimbra at mediacombb.net
> >
> > Content-Type: text/plain; charset=utf-8
> >
> > Here are a few online projects for GPS-controlled clocks. Most (all?)
> have
> > a PIC or Arduino to run the clock and sync to GPS time.
> > [ http://w8bh.net/avr/clock2.pdf | http://w8bh.net/avr/clock2.pdf ]
> > https://www.elprocus.com/how-to-build-a-gps-clock-using-arduino/
> > https://learn.adafruit.com/arduino-clock
> > https://www.tindie.com/products/nsayer/gps-clock/
> > https://mitxela.com/shop/clock
> > https://www.sparkfun.com/tutorials/47
> >
> > DIY projects are easy to find with Google:
> > The search string I used was: gps digital clock kit OR diy OR build
> >
> > There are a number of clocks with Nixie tube displays also; just add
> > "nixie" to the Google search string.
> >
> > Good luck
> > Dave M
> >
> >
> >
> >
> > From: "Eamonn Nugent" <elg.nugent at gmail.com>
> > To: time-nuts at lists.febo.com
> > Sent: Tuesday, March 2, 2021 4:38:24 PM
> > Subject: [time-nuts] World's most precise.... wall clock
> >
> > Hi!
> >
> > I have a perhaps silly question. I want to take an inferior medium (our
> > eyes) and give it something attractively precise to look at. Is there
> such
> > a thing as a digital (wall) clock with a 1PPS/10MHz/etc. input? I see
> that
> > some clocks have GPS antenna inputs, but I want to take a GPSDO and hook
> > it
> > up to a digital clock. Purely for fun, as a mini project for myself while
> > I
> > build my bigger clocks.
> >
> > Maybe one day I'll make this work with a grandfather clock.
> >
> > Thanks,
> >
> > Eamonn
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
> >
> > ------------------------------
> >
> > Message: 9
> > Date: Tue, 02 Mar 2021 22:42:45 -0800
> > From: Hal Murray <hmurray at megapathdsl.net>
> > To: Discussion of precise time and frequency measurement
> > <time-nuts at lists.febo.com>
> > Cc: hmurray at megapathdsl.net
> > Subject: Re: [time-nuts] World's most precise.... wall clock
> > Message-ID:
> > <20210303064245.9FA6140605C at ip-64-139-1-69.sjc.megapath.net>
> > Content-Type: text/plain; charset=us-ascii
> >
> > > Maybe one day I'll make this work with a grandfather clock.
> >
> > Many years ago, Scientific American had an article describing adding a
> > magnet
> > to the pendulum and the circuitry to drive it.
> >
> > The basic idea is to mount a magnet on a stiff wire so that it sticks out
> > to
> > the side of the pendulum arm, then mount a coil so the magnet will swing
> > through it. Now pulse the coil to get the desired results.
> >
> > Scientific American, September 1974, Amateur Scientist
> > A venerable clock is made highly accurate by equipping it with
> > quartz-crystal works
> >
> > They want $8 for a pdf.
> >
> https://www.scientificamerican.com/article/the-amateur-scientist-1974-09/
> >
> >
> > --
> > These are my opinions. I hate spam.
> >
> >
> >
> >
> >
> >
> > ------------------------------
> >
> > Message: 10
> > Date: Wed, 3 Mar 2021 08:37:53 +0000
> > From: David Taylor <david-taylor at blueyonder.co.uk>
> > To: time-nuts at lists.febo.com
> > Subject: Re: [time-nuts] World's most precise.... wall clock
> > Message-ID: <1393578e-89cf-c8f1-434a-9c649e46dae5 at blueyonder.co.uk>
> > Content-Type: text/plain; charset=utf-8; format=flowed
> >
> > On 02/03/2021 22:38, Eamonn Nugent wrote:
> > > Hi!
> > >
> > > I have a perhaps silly question. I want to take an inferior medium (our
> > > eyes) and give it something attractively precise to look at. Is there
> > such
> > > a thing as a digital (wall) clock with a 1PPS/10MHz/etc. input? I see
> > that
> > > some clocks have GPS antenna inputs, but I want to take a GPSDO and
> hook
> > it
> > > up to a digital clock. Purely for fun, as a mini project for myself
> > while I
> > > build my bigger clocks.
> > >
> > > Maybe one day I'll make this work with a grandfather clock.
> > >
> > > Thanks,
> > >
> > > Eamonn
> > Eamonn,
> >
> > I built my own with a Raspberry Pi. As it's display-based you can make
> > it look just as you wish.
> >
> > https://www.satsignal.eu/raspberry-pi/DigitalClock.html
> >
> > Mine takes 1pps/NMEA deom a GPS.
> >
> > David
> > --
> > SatSignal Software - Quality software for you
> > Web: https://www.satsignal.eu
> > Email: david-taylor at blueyonder.co.uk
> > Twitter: @gm8arv
> >
> >
> >
> > ------------------------------
> >
> > Message: 11
> > Date: Wed, 3 Mar 2021 09:54:36 +0100
> > From: Attila Kinali <attila at kinali.ch>
> > To: Discussion of precise time and frequency measurement
> > <time-nuts at lists.febo.com>
> > Subject: Re: [time-nuts] World's most precise.... wall clock
> > Message-ID: <20210303095436.40523a874e437af353260c23 at kinali.ch>
> > Content-Type: text/plain; charset=US-ASCII
> >
> > On Tue, 02 Mar 2021 22:42:45 -0800
> > Hal Murray <hmurray at megapathdsl.net> wrote:
> >
> > > The basic idea is to mount a magnet on a stiff wire so that it sticks
> > out to
> > > the side of the pendulum arm, then mount a coil so the magnet will
> swing
> > > through it. Now pulse the coil to get the desired results.
> >
> > This is basically injection locking of a pendulum clock.
> > Pendulum clocks are very nice for injection locking, due
> > to their relatively low Q and because a magnetic field can
> > be easily adjusted in strength.
> >
> > You don't need to place the magnet at any one specific position.
> > It is enough that it is somewhere in the path of the pendulum.
> > My favorite position is right beneath the center.
> >
> > The injected pulses should be long enough to have an effect
> > with a reasonably weak magnetic field, but short enough to
> > be an impulse, from the point of view of the mechanical system.
> > I.e. the pulse length should be a fraction of the time it take
> > for the pendulum to pass the magnet. Somewhere between 1/2
> > and 1/10 should work in most cases.
> >
> > Start with getting the pendulum clock as close to the right
> > rate as possible. Place the magnet where it suits you best.
> > Then adjust the current through the magnet such that you can
> > barely feel some resistance when you move the pendulum through
> > the field with your hands. Set your electronics to inject pulses
> > at the appropriate rate. This does not have to be at every pass,
> > but can be, e.g., every 10th pass. Now let the clock run and see
> > whether you get proper synchronization/locking. If not, increase
> > the current through the magnet step wise until it is strong enough
> > for synchronization. Test over varying temperatures, air humidity
> > and pressure to ensure that changes of the natural frequency of
> > the pendulum don't get your clock unlocked.
> >
> > If you have trouble with keeping the clock locked and don't want
> > to increase the current any further, increase the pulse length.
> >
> > For additionaly time-nuttyness, you can add a sensor somewhere in
> > the path of the pendulum and measure its phase versus true
> > time. Suitable sensors are fork light barriers and Hal sensors.
> >
> >
> > Attila Kinal
> > --
> > The driving force behind research is the question: "Why?"
> > There are things we don't understand and things we always
> > wonder about. And that's why we do research.
> > -- Kobayashi Makoto
> >
> >
> >
> > ------------------------------
> >
> > Message: 12
> > Date: Wed, 3 Mar 2021 12:00:31 -0300
> > From: Edesio Costa e Silva <edesio at softaplic.com.br>
> > To: Discussion of precise time and frequency measurement
> > <time-nuts at lists.febo.com>
> > Cc: Hal Murray <hmurray at megapathdsl.net>
> > Subject: Re: [time-nuts] World's most precise.... wall clock
> > Message-ID: <20210303150030.GA3590 at softaplic.com.br>
> > Content-Type: text/plain; charset=iso-8859-1
> >
> > Hi!
> >
> > I found a copy at <
> > https://www.g8wrb.co.uk/useful-stuff/time/pdf/pendulum+quartz.pdf>
> >
> > Ed?sio
> >
> > On Tue, Mar 02, 2021 at 10:42:45PM -0800, Hal Murray wrote:
> > > > Maybe one day I'll make this work with a grandfather clock.
> > >
> > > Many years ago, Scientific American had an article describing adding a
> > magnet
> > > to the pendulum and the circuitry to drive it.
> > >
> > > The basic idea is to mount a magnet on a stiff wire so that it sticks
> > out to
> > > the side of the pendulum arm, then mount a coil so the magnet will
> swing
> > > through it. Now pulse the coil to get the desired results.
> > >
> > > Scientific American, September 1974, Amateur Scientist
> > > A venerable clock is made highly accurate by equipping it with
> > quartz-crystal works
> > >
> > > They want $8 for a pdf.
> > >
> >
> https://www.scientificamerican.com/article/the-amateur-scientist-1974-09/
> > >
> > >
> > > --
> > > These are my opinions. I hate spam.
> > >
> > >
> > >
> > >
> > > _______________________________________________
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> > > and follow the instructions there.
> >
> >
> >
> > ------------------------------
> >
> > Subject: Digest Footer
> >
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> >
> >
> > ------------------------------
> >
> > End of time-nuts Digest, Vol 200, Issue 4
> > *****************************************
> >
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