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Author Topic: Accurate wooden clocks!  (Read 3871 times)
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kit
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« on: July 17, 2016, 08:08:51 AM »

I know that wooden pendulum clocks are built more as kinetic sculpture s than timepiece s, but it would be nice to have a clock that is both. To this end I've been looking into design ideas for a GPS-locked pendulum that is electroma gneticall y powered in a similar way to some of the Woodentim es clocks but which also compares the timing of the pendulum to the very convenien t and deadly accurate "One Pulse Per Second" signal generated by GPS receivers . My plan is to use a small electric motor to move the centre of mass of the pendulum to keep it in step with the 1PPS pulses.

Another option, adopted by carveshop (http://www.carveshop.com/html/accuracy.html) is to adjust the amplitude of the pendulum to adjust it's timing relative to a crystal derived standard. They use an unusually high amplitude that varies between 15 and 25 degrees to give a little under 1% adjustmen t range.

Obviously either method could be adapted to crystal or GPS control depending on the desired accuracy and cost.

Has anybody else played with these ideas and what results have you had?

Kit
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ArtF
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« Reply #1 on: July 17, 2016, 08:57:33 AM »

Hi Kit:

  In the end, when striving for accuracy, the obvious question is "How Accurate?".
a reed switch, a chip and a coil could kick a pendulum as it crosses center, the power of the kick
( pulse width)) would then control accuracy. . up to a point...

 I havent tried any methods to increase accuracy, or added electroni cs to a ticker.. I always figure I can
publish a ticker video and several people will build it, but as soon as I add electroni cs, very few will ever try it,
as the electroni cs scares many. ( though its really easier than its ever been.. ).

  Id imagine a 5$ arduino chip could control a clock as long as the battery holds out.. Ive seen a few examples. .

I wonder how popular an electroni c version of a wooden clock (ticker) would be? Next step would be one you plug
in, then a stepper motor could be added.. run by a bluetooth arduino that checks the internet for sync.. No limit
really to what one could add..but then.. theres that stigma about a electrica l cord or battery on a wooden mechanism ...
Im not sure it doesnt detract to an amazing level..bu t maybe thats just me.

  How about a poll? When anyone reads this, mention how you'd feel about a ticker design that encompass es
soem sort of electroni cs in it. Does it detract if a ticker took power ( battery or plug)? Would you try to build a
design that requires you to do some simple wiring or do you feel that a wooden sculpture s "purity" or
craftsman ship is suspect if it takes power?  Im rather curious on this one, myself and Bob have had
this discussio n several times, my feeling has always been it somehow detracts from a sculpture
if it has wires, how do others feel? Is it just me that feels that way ?

   Its pretty easy for me, as I can program arduinos , wire or design circuits to drive a ticker,
but Ive never been sure anyone really wants or will build something electroni cally driven..
and Ive not been keen on having a cord trailing down the wall behind what I build personall y..
even though I could then program it to do a heck of a lot more than typically .. All a matter
of esthetics I guess, but I woudl be curious to know how others feel.

  So.. how much electroni cs is fair game in a ticker or clock that you may consider building. .

a) None.
b) Simple battery pulse circuit to maintain pendulum timing..
c)  Inexpensi ve microproc essor driven stepper control device.. ( say 30.00 for power, motor and microproc essor component s...)
d) Dont matter, Id never build a wooden sculpture anyway..

 So if your reading this, hit reply and just enter a-d if your not up for a descripti ve answer.. Id be intereste d in
what people think belongs in something they build..

Art





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John T
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« Reply #2 on: July 17, 2016, 09:10:06 AM »

A.

If I want accuracy I'll simply look at my iPhone.
I've built 34 wooden clocks and have have played with regulatin g some of these to about 10 seconds in 24 hours, just see if I could. Ultimatel y it's the weather that makes the differenc e.  For me deadly accuracy isn't where it's at.

John
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ArtF
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« Reply #3 on: July 17, 2016, 09:14:40 AM »

John:

  I hear you. Smiley

  I was thinking more of very impressiv e hour chiming.. dancing monkeys or whatever. Smiley

Art
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John T
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« Reply #4 on: July 17, 2016, 10:54:37 AM »

Hi Art
I've only built one that chimes the hour and it is an order of magnitude more finicky to get it running reliably. I have several that "bong" on the hour or half hour. No dancing monkeys and not even a snail.

John
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kit
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« Reply #5 on: July 18, 2016, 04:08:30 AM »

Dancing monkeys. Now there's an idea! Actually. ...NO!

Like you Art, I know how to program an Arduino and wield a soldering iron. My day job involves maintaini ng a machine that generates a million watts of wireless waves, so that's probably a good thing Wink

One of my biggest concerns about this design is going to be how the wires run. There will be a power cable from the wall wart powering the whole thing and a 5m cable for the GPS antenna. I appreciat e all the concerns about the 'purity' of an electric wooden pendulum clock but it's an interesti ng design challenge and there's something I find intensely annoying about a clock that can't be relied upon when you have an appointme nt to keep (especiall y when I know how good I'd be at rememberi ng to keep it wound!) but it's very appealing to have a visually interesti ng clock in a prominent position on the wall which can be the reference timepiece for the whole household .

I've been given the plans for the 'Sextus' clock from Woodentim es for my birthday so that will be the main project for a while. I will be working on the GPS-locked pendulum as well and then be using Gearotic to design a clock for it if I get it working reliably. No idea how accuratel y I can make the Sextus run but I don't see it being GPS-locked any time soon.

Kit
« Last Edit: July 18, 2016, 06:47:26 AM by kit » Logged
marklazarz
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« Reply #6 on: July 18, 2016, 08:56:02 AM »

My vote - None.  Could I build one with electroni cs?  Yes, if it was fairly well documente d.  Would I build one?  No.

Besides that, my wooden clocks provide dual functiona lity, one being a clock, the other being a hygromete r.  One stops at RH 60%, another stops at RH 65%.
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ArtF
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« Reply #7 on: July 18, 2016, 09:43:48 AM »

Mark:

  Tends to be my feeling as well, adding a wire to a wooden sculpture kinda cheapens it..

Art
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Mooselake
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« Reply #8 on: July 18, 2016, 11:15:59 AM »

Mark, you could make a tick sensor and use them to run your dehumidif ier Smiley

Kit, you could try a microcont roller and an RC servo in the weight to vary the pendulum length, just pretend it's extra mass Smiley

Kirk
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kit
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« Reply #9 on: July 18, 2016, 08:45:21 PM »

One stops at RH 60%, another stops at RH 65%.
Mark,
I hadn't thought of that dual functiona lity! When the clock stops there's a cyclone on the way.

Kirk,
My plan is to use a small GPS module from Adafruit ( https://www.adafruit.com/product/746) to provide the 1PPS signal and an Arduino microcont roller to do all the thinking. I'm going to use a small leadscrew to move the pendulum weight as this will maintain position without being continuou sly powered. In the long term I'd like it battery backed to survive power outages so that it can be set once and tell the correct time for ever more. For me, the pleasure of watching the movement of the clock will be enhanced by knowing that it's bang on accurate.
I have nearly 50 years more experienc e with electroni cs than I do with wooden clocks so this will be the easy bit. It's the mechanics of the clock and getting the aesthetic s just right that will present the problems.

Stage one is to get a pendulum swinging reliably in time to pulses from a much cheaper oscillato r circuit. If I can't get that bit working the whole project is bin-fodder.

I can imagine some of our readers raising their hands in horror, but it's this diversity of views that makes people so interesti ng.
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ArtF
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« Reply #10 on: July 18, 2016, 08:55:13 PM »

>>getting the aesthetic s just right that

  Thats always the key.. no matter wires, weights or whatever. .

Smiley

Art
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BobL
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« Reply #11 on: July 19, 2016, 04:18:59 PM »

Hi;

 I'm no artist, but for me if I get the WOW impressio n then I'm OK with some electroni cs inside.  The less subtle the better obviously, it's kinda like magic that keeps you guessing of how did they do that?  I do respect the views of this oppositio n, and I agree with most of it in general,  but I see this simply as another form of art.  A delicate balance exist between them for sure, but overall, it is still just another form of art.  Anyhow I believe similar debates is what keeps hobbyist experimen ting, and who knows just what cool art device they may come up with someday?


Cheers
Bob
 Wink   
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kit
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« Reply #12 on: June 21, 2019, 11:05:26 PM »

Well, this topic didn't so much get put on the back burner as stuffed in a box and dropped in the freezer! There ia a video on the forum of an electric pendulum from Oct 2017 (http://gearotic.com/ESW/FavIcons/index.php?topic=1778.0) but this is an all-new design of an accurate, electrica lly driven wooden clock.

There's a short video of the prototype at https://vimeo.com/343781598. The final clock will have all the weights and magnets on the back rim of the circular pendulum and all the electroni cs hidden in the base. The design is intended to be easily put into an exhibitio n without having to be hung on a wall and can be powered from a standard USB mobile phone charger.

The design uses a circular pendulum driven by an electroma gnet which repels a permanent magnet mounted on the base of the pendulum. The electroma gnet is triggered by additiona l magnets on the pendulum and a Hall effect sensor. The amplitude of the pendulum's oscillati on is very high at about +- 45 degrees. At this amplitude small changes of amplitude also cause significa nt changes in period. Higher amplitude means a longer period which means too much drive makes the clock run slow. The drive to the electroma gnet is normally enough to push the amplitude too high. By comparing the relative timing of the pendulum as detected by the Hall sensor with an accurate one pulse per second (1PPS) signl derived from a crystal oscillato r or a GPS receiver, the drive is inhibited for some pulses to keep the amplitude just right. Additiona l cuircuitr y makes sure the amplitude cannot go above or below set limits to improve reliabili ty and starting.

Instead of a microcont roller and convolute d software which was the key element of the earlier work, this design uses every pre-computer-age electroni c hobbyists favourite toy the 555 timer. Four of them and a few standard  logic gates do all the clever stuff. The final design will include a basic crystal oscillato r and a battery to make a stand-alone piece for exhibitio n.

To help produce a compact design that can either sit on a shelf or mount on the wall I also used David Morrow's idea of using fixed arbours with the wheels each having their own bearings. This allows any number of wheels of diferent speeds to run on the same arbour. The only moving arbour is the centre one for the minute hand which also has the pendulum bearing mounted on it.

Kit
« Last Edit: June 21, 2019, 11:09:19 PM by kit » Logged
ArtF
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« Reply #13 on: June 22, 2019, 10:37:52 AM »

Kit:

  My impressio ns? Well built, artistic and seems to run very well. I say
congrats on a fine project. I know from experienc e all the dicking about
you need to do to make it look as it does, way to go!.

   I dont think the electroni cs in this case cheapen it at all , Id hide them
in the back and let it sit proudly on its shelf or mantle. Anyone
noticing it sitting swinging away will undoubted ly be left
with the (proper) thought that your something of a craftsman .

Art
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kit
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« Reply #14 on: June 22, 2019, 08:35:20 PM »

Art,

That's very kind of you to say so.

This is only the working model, I wasn't sure what drive power I'd need to move the whole gear train or what range of adjustmen t there'd be on the period whilst still running the ratchet properly. In practice there's been no problem with only a 5v supply and the peak current demand (when charging the capacitor that is discharge d into the coil) is a brief 200mA so no problems powering it from a phone charger which was the aim.

The finished clock will be made from a variety of West Australia n hardwoods using the CNC router that has taken up far too much of my time over the last year and more. At last I have a reliable (shouldn't say that out loud!) accurate machine for doing real work which is why I've finally been able to get back to the clock.

Kit
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