Hi Philip, I have read about the approach you described with a magnet on the pendulum and a stepper adjusting a steel plate up and down. The one I saw (on Hackaday) seemed to work very well.
I don't really see what the difference is between that method and the method I used. My electromagnet generates a magnetic field the same as the method you described. My pendulum is not being pushed/pulled into correct timekeeping. For example, over the past thirty minutes, the magnet is energized for 16 - 20 beats per minute (which for this clock is 29 - 36 seconds) depending on the error during that minute.. I wasn't clear in my first email on how the error (phase difference) is measured. Because of the strange period of the pendulum (actually 33 beats per minute), and the period of the 1PPS signal, the two line up only three times per minute. That is 11 beats, at 20 seconds, 22 beats, 40 seconds, and 33 beats, at 60 seconds. I hope I said that right. So for all practical purposes, the error can be measured once or twice per minute. The magnetic field period is calculated and applied for whatever portion of a minute is necessary. I believe that you are thinking that you can adjust your plate up and down to apply a variable magnetic field to speed up the pendulum as required. Maybe on a brand new clock, or a well maintained one, you might be able to set the distance and let the clock run for a long time with a given field.. The mechanism on my clock has serious wear. Over a two hour period, it speeds up and slows down periodically as the gears bind. So to maintain a constant phase error, the pulse generated compensates for that problem. Seems to me, it works the same as the method you described. For my clock, you would have to adjust your plate up and down over a 2 hour period to keep the time error the same. Regardless, good luck with your project - I'd love to see the results. Keep us posted! Gerald AI4DE ----------------------------- > > Message: 7 > Date: Wed, 10 Mar 2021 10:43:19 -0500 > From: Philip Gladstone <pjsg-timen...@nospam.gladstonefamily.net> > To: Discussion of precise time and frequency measurement > <time-nuts@lists.febo.com> > Subject: Re: [time-nuts] Grandfather clock sync'd to 1PPS (from > time-nuts Digest, Vol 200, Issue 4) > Message-ID: > < > camd_wwrfz5pm2zeb6asga6b-15vyoxc4v2s8qqfsfwvqurq...@mail.gmail.com> > Content-Type: text/plain; charset="UTF-8" > > 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 > > _______________________________________________ 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.