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 <gds32...@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-requ...@lists.febo.com> wrote: > > > Send time-nuts mailing list submissions to > > time-nuts@lists.febo.com > > > > To subscribe or unsubscribe via the World Wide Web, visit > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > or, via email, send a message with subject or body 'help' to > > time-nuts-requ...@lists.febo.com > > > > You can reach the person managing the list at > > time-nuts-ow...@lists.febo.com > > > > 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 <kb...@n1k.org> > > To: Discussion of precise time and frequency measurement > > <time-nuts@lists.febo.com> > > Subject: Re: [time-nuts] Old Crystal. > > Message-ID: <e982f541-5591-4e81-b7e0-5c8755390...@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 <eb4...@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@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.nug...@gmail.com> > > To: time-nuts@lists.febo.com > > Subject: [time-nuts] World's most precise.... wall clock > > Message-ID: > > <CAPQA= > > kh+b87dqqvtkwnrh+9y_d2udrh58-kpkdyha7zzamd...@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" <wb...@gci.net> > > To: "Eamonn Nugent" <elg.nug...@gmail.com>, "time-nuts@lists.febo.com" > > <time-nuts@lists.febo.com> > > Subject: Re: [time-nuts] World's most precise.... wall clock > > Message-ID: <e9.43.19889.e75de...@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@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 <e...@telight.com> > > To: time-nuts@lists.febo.com > > Subject: Re: [time-nuts] World's most precise.... wall clock > > Message-ID: <603ed92f.1030...@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" <drkir...@kirkbymicrowave.co.uk> > > To: "time-nuts@lists.febo.com" <time-nuts@lists.febo.com> > > Subject: [time-nuts] NPL courses on time and frequency measurement > > Message-ID: > > < > > canx10hdypo4mg2-lvco7_nbzgq4a4gat9uwkkkjudyvvgf7...@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" <j...@luxfamily.com> > > To: time-nuts@lists.febo.com > > Subject: Re: [time-nuts] World's most precise.... wall clock > > Message-ID: <586e610a-b13f-4872-a26e-9930fd0df...@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 <t...@leapsecond.com> > > To: time-nuts@lists.febo.com > > Subject: Re: [time-nuts] World's most precise.... wall clock > > Message-ID: <a88d22d6-4400-8725-fa7d-3961c41fc...@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@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 <dgmin...@mediacombb.net> > > To: Discussion of precise time and frequency measurement > > <time-nuts@lists.febo.com> > > Subject: Re: [time-nuts] World's most precise.... wall clock > > Message-ID: > > <684600294.21613154.1614739307850.javamail.zim...@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.nug...@gmail.com> > > To: time-nuts@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@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 <hmur...@megapathdsl.net> > > To: Discussion of precise time and frequency measurement > > <time-nuts@lists.febo.com> > > Cc: hmur...@megapathdsl.net > > Subject: Re: [time-nuts] World's most precise.... wall clock > > Message-ID: > > <20210303064245.9fa61406...@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-tay...@blueyonder.co.uk> > > To: time-nuts@lists.febo.com > > Subject: Re: [time-nuts] World's most precise.... wall clock > > Message-ID: <1393578e-89cf-c8f1-434a-9c649e46d...@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-tay...@blueyonder.co.uk > > Twitter: @gm8arv > > > > > > > > ------------------------------ > > > > Message: 11 > > Date: Wed, 3 Mar 2021 09:54:36 +0100 > > From: Attila Kinali <att...@kinali.ch> > > To: Discussion of precise time and frequency measurement > > <time-nuts@lists.febo.com> > > Subject: Re: [time-nuts] World's most precise.... wall clock > > Message-ID: <20210303095436.40523a874e437af353260...@kinali.ch> > > Content-Type: text/plain; charset=US-ASCII > > > > On Tue, 02 Mar 2021 22:42:45 -0800 > > Hal Murray <hmur...@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 <ede...@softaplic.com.br> > > To: Discussion of precise time and frequency measurement > > <time-nuts@lists.febo.com> > > Cc: Hal Murray <hmur...@megapathdsl.net> > > Subject: Re: [time-nuts] World's most precise.... wall clock > > Message-ID: <20210303150030.ga3...@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. > > > > > > > > > > > > > > > _______________________________________________ > > > time-nuts mailing list -- time-nuts@lists.febo.com > > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > > and follow the instructions there. > > > > > > > > ------------------------------ > > > > Subject: Digest Footer > > > > _______________________________________________ > > time-nuts mailing list > > time-nuts@lists.febo.com > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > > > > > ------------------------------ > > > > End of time-nuts Digest, Vol 200, Issue 4 > > ***************************************** > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.