First Attempt at an Electronic Hipp Clock

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First Attempt at an Electronic Hipp Clock

This topic has 38 replies, 10 voices, and was last updated 10 February 2023 at 15:58 by Roger Jelbert.

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28 January 2023 at 22:43 #3997
John Purdy
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@johnpurdy78347
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28 January 2023 at 22:43 #631222
John Purdy
Participant
@johnpurdy78347
My first attempt at making an electronic "Hipp" toggle clock. Definitely a proof of concept. Over the last 24 hours it has lost 1 1/2 minutes compared to the quartz clock in the workshop. I don't expect it to keep very accurate time as the pendulum rod is just a length of 1/4" 303SS and it is in the workshop whose temperature currently fluctuates from 6-7 to 20-22 deg. depending on whether I'm working in there or not. The bob is a 2" x 8" brass tube filled with lead and weighs 4.123 kgms. The electronics are similar to those of Carl Wilson (ME 4694 et al ) with a number of modifications and additions. Rather than optos I'm using Hall effect devices to sense pendulum position. Currently the pendulum is receiving an impulse every 3 min. 30 secs. plus or minus a few seconds. The clock is a standard quartz movement with the Lavet stepper isolated and driven by the pendulum clock electronics. Before anyone says " why didn't you use a micro computer ? (Arduino, BBC microbit )" its because I have a whole box of TTL and CMOS chips collected over the years and its been 35+ years since I did any "C" programming!

It's time now to start on Mk2, carbon fiber tube, revised upper suspension, micro processor controlled and to try John Haines Helmholtz coils idea for supplying the impulse for the pendulum.

John
29 January 2023 at 00:09 #631228
duncan webster 1
Participant
@duncanwebster1
Neat!
29 January 2023 at 09:06 #631240
John Haine
Participant
@johnhaine32865
Nice to see it ticking John!
29 January 2023 at 10:03 #631243
SillyOldDuffer
Moderator
@sillyoldduffer
Another fan. Is there such a thing as pendulum porn? I've been ogling the pictures for a good 5 minutes!

Dave
29 January 2023 at 14:32 #631267
Martin Kyte
Participant
@martinkyte99762
Not in any way a criticism, you have without doubt produced an interesting timepiece but a Hipp clock?. I recognise you have titled it an electronic Hipp clock and omitted the toggle tag but I thought the whole essence of the Hipp Toggle clock was in fact the toggle mechanism of the same name. I realise you have to call it something so do we need a new name for electronically sensed, magnetically impulsed free pendulum timepieces.?

Maybe Pendulatrons ?

I’m sure someone has a better name but the variety of interesting new takes on free pendulum oscillators deserves a class name of their own.

regards Martin
29 January 2023 at 15:23 #631269
John Haine
Participant
@johnhaine32865
Roger Jelbart called his a Chipp Toggle…

Rogerj.co.uk
29 January 2023 at 15:42 #631270
John Haine
Participant
@johnhaine32865
Also the Hipp Toggle strikes me as a horrible mechanism which must perturb the pendulum every cycle just so it can detect when the amplitude has decayed enough to give an impulse. Electronics gets us away from that so maybe we can avoid "guilt by association"!
29 January 2023 at 16:21 #631272
duncan webster 1
Participant
@duncanwebster1
From the Ministry of UTLAs. How about Controlled Amplitude Timepiece, or CAT for short

Edited By duncan webster on 29/01/2023 16:22:42
29 January 2023 at 16:38 #631276
Tony Jeffree
Participant
@tonyjeffree56510
Posted by Martin Kyte on 29/01/2023 14:32:42:

Not in any way a criticism, you have without doubt produced an interesting timepiece but a Hipp clock?. I recognise you have titled it an electronic Hipp clock and omitted the toggle tag but I thought the whole essence of the Hipp Toggle clock was in fact the toggle mechanism of the same name. I realise you have to call it something so do we need a new name for electronically sensed, magnetically impulsed free pendulum timepieces.?

Maybe Pendulatrons ?

I’m sure someone has a better name but the variety of interesting new takes on free pendulum oscillators deserves a class name of their own.

regards Martin

The whole essence of the Hipp toggle isn't the mechanism itself, but what it is there for – which is to both detect the decaying swing amplitude of the pendulum and to trigger the electromagnetic impulse necessary to restore the swing amplitude, and therefore keep the swing amplitude within defined bounds. This clock uses sensors and logic to achieve the same end result, but with no mechanical interference to the pendulum – as did my own free pendulum clock, serialised in MEW last year (https://www.model-engineer.co.uk/forums/postings.asp?th=171748 ). I suspect that if Hipp had been able to use modern electronic devices in place of his toggle, he would have done so, but in his day, he had little option but to invent a mechanical solution. That being the case, describing this (and my clock for that matter) as "an Electronic Hipp Clock" seems pretty reasonable to me.
29 January 2023 at 18:41 #631286
Martin Kyte
Participant
@martinkyte99762
Fair comment Tony and I did acknowledge the removal of the word toggle and the inclusion of electronic. However to me the name Hipp toggle does seem fairly wedded to the impulsing mechanism rather than the rest of the clock so I wondered if we could do better. All these clocks are essentially free pendulum timepieces and the similarity in my mind to either the Hipp or the Synchronome is somewhat tenuous. Just an opinion.

regards Martin
29 January 2023 at 23:53 #631311
John Purdy
Participant
@johnpurdy78347
An update. After 48 hours it is now 1:48 minutes slow, so in the last 24 hours it has only lost 17 seconds (had been 1:31 after 24 ) so seems to have stabilized. The pendulum is currently swinging through an arc of 5.67 deg. right after it has been given an impulse. Just from measurements the pulse of current to the magnets lasts 96ms. At the moment I'm not about to lug my scope into the workshop to confirm that! The coils for the magnets measure 6.82 and 6.69 ohms and when connected in series draw ~370ma @ 5 volts.Too keep things simple for a start I decided to drive the coils with 5 volts from the logic board power supply. I removed the 5 volt jumper on the L298 module and connected the 5 volts from the logic board to both the 12 and 5 volt input and ground on the L298 module. I wasn't sure if this would be enough to give sufficient impulse to the pendulum as the output from the L298 to the coils is probably in the neighborhood of 4 volts, but it seems to be fine as it is impulsing only once every 3 1/2 minutes to keep the pendulum swinging.

Here's a couple of pics of the logic boards.
30 January 2023 at 11:23 #631341
SillyOldDuffer
Moderator
@sillyoldduffer
A few comments if I may:
- My clock data shows the pendulum takes a while to stabilise from starting, so I let it run for a few minutes before setting the time. The error isn't huge, but it's detectable,
- There's a good chance drift is the dominant error. That is the pendulum isn't adjusted spot on, and runs slightly slow or slightly fast. If the clock gains or loses at a constant rate over several days, the mechanical construction and electronics are probably both good, The problem is how to adjust the period of the pendulum accurately. It's not easy, especially when the pendulum is close to correct, because the effect of temperature and air pressure changes become significant and confuse the issue. The early regulator clocks used in Observatories to calibrate time didn't attempt to get their pendulums spot-on. Instead, they put considerable effort into finding the rate of the clock relative to time from star observations. When the rate was known, they read the dial, and corrected the reading from a rate table. So the dial in the observatory clock might be significantly 'wrong' compared with the ordinary clocks and chronometers it was setting accurately. So let the thing run, and write down how it compares with an accurate time over several days. If the rate of drift is constant, award self a gold star. If the rate varies inconsistently, look for mechanical, electronic, sensor or environmental problems. How good should it be? In their day, when they were best in the world, Shortt clocks were good to about 1 second per year.
- In the great hardware vs software debate we're exact opposites. I'm a fairly competent programmer, but it's 25 years since I last did any serious digital circuitry, and 20 since I made a PCB with Ferric Chloride. To poor old out-of-date me physical circuits are hard work, to be avoided if possible, especially since components became sub-miniature. But hardware logic has some significant advantages, notably speed, and should always be on the table. Suspicion is growing that my clock's input electronics are a step too over-simplified!
- If anything misbehaves erratically on your clock my first suspect would be powering the magnets directly off the logic board. The magnets could easily disrupt the logic by injecting spikes and brown-outs into the chips through the power rail. (You can guess how I know!)
Nice work,

Dave

Edited By SillyOldDuffer on 30/01/2023 11:24:02
30 January 2023 at 19:13 #631379
John Purdy
Participant
@johnpurdy78347
Dave
Thanks for your reply.

My thoughts are along your lines in that I plan on just logging the time difference over a number of days and see how consistent it is. The large difference between day one and two might be that on day one I had the heater on for about 2 hours bringing the temp up from its normal ~8deg to 22 for about 2 hours whereas on day 2 there was no heat on. When logging the daily difference I'll have to note whether the heat has been on to see what difference that makes.

As far as driving the magnets from the logic power supply I haven't noticed any problems, there are Schottky snubbing diodes on the output of the L298 module that should take care of any back EMF from the coils.

Your comment about being opposites in the software/hardware debate is quite correct. The last programming I did was in the '80s, and that was in Fortran and Assembler and a small amount of "C" ( still have Kernighan and Ritchies book on programming in "C", they were the ones that developed "C" at Bell Labs for the UNIX operating system ). I've been making PCB since the late '50s, first ones with model airplane dope and a paint brush! Got more sophisticated over the years graduating in the '70s to artwork/cameras,litho film/photo resist. Currently it's software/laser printer/iron on resist, much less hassle. Gave up on ferric chloride quite a few years ago, one time use, disposal problems and corrodes everything in sight. Now use cupric chloride. While not as fast as ferric can be regenerated indefinitely by bubbling air through it and periodically adjusting the pH and SG with HCl and water . I started out with 500 ml, now have over 2L.
John

Edited By John Purdy on 30/01/2023 19:15:12

Edited By John Purdy on 30/01/2023 19:16:59
30 January 2023 at 19:53 #631382
S K
Participant
@sk20060
Very nice!

I'm working on something similar. A question: I note that you have positioned the coil drive pointing vertically. I've seen that elsewhere at least once, too. I wonder why that is? Wouldn't it be more efficient pointing horizontally? Also, does it have an iron core or is it open?

Thanks.
30 January 2023 at 22:12 #631389
John Purdy
Participant
@johnpurdy78347
SK
Thanks. The coils are 1.875" between cheeks and consist of 12 layers, 100 turns per layer of .45mm (.0177 ) wire wound on a soft iron core .460" dia. ending up just under 1"dia. The two coils are spaced 1.000" apart bolted to a soft iron yoke at the bottom, and spaced out from the backboard so that the centre of the two coils is on the centre line of the bob when at rest and spaced off to the left so that the left edge of the 3/4" wide armature on the bottom of the rod is on the centre line of the coils. The coils are activated as the pendulum is 11mm from the vert position in its swing right to left and are deactivated as it reaches the vertical postion . The two coils are connected in series with the start of each winding connected together and the end windings connected to the voltage source. This gives the max mag flux.
As far as positioning them horiz or vert, all the pics I've seen have them where I have them. If horiz they would have to be out to one side beyond the max swing with the impulse given just before max swing rather than at the centre of the swing. How this might affect the timing I don't know. It would have one positive effect though, it would eliminate the downward pull on the pendulum every time they are actuated that exist with them underneath as I have them. The effect is quite obvious in mine as I don't even have to look at the indicator LED on the logic board to know when the coils are driven as there is a very audible "sprong" (for lack of a better description ) sound from the pendulum rod. I put it down to one of two possible things, the rod, suddenly being put in tension vibrates like it has been plucked, or the rod has a very slight bend it it and when put under tension straitens slightly again vibrating like it has been plucked.
John
30 January 2023 at 22:23 #631390
duncan webster 1
Participant
@duncanwebster1
Mine has a single coil off a 24vAC relay, with mild steel pole pieces to make up the circuit. Triggered about 4mm before centre and off just before centre (timed by the Arduino). The coils are driven off the 5v through a potentiometer, resistance increased until it misses only the occasional pulse. It pulses both ways, and can only miss one way. If I reduce the resistance enough I can make it swing wildly, only being impulse on alternate swings. It is completely silent.
30 January 2023 at 23:31 #631396
S K
Participant
@sk20060
Thank you for the detailed explanation. The second coil was almost hidden in the head-on photo, so thanks for mentioning that too.

I think a horizontal arrangement should be OK in principle even when activated at vertical, except that the amount of energy needed would be higher. One pendulum I saw (from memory) included symmetrical rod "horns" extending towards the coil, and partially encompassed by the coreless coil, so it was operating essentially as a solenoid.

Do you have any comments about the use of the Hall effect sensors? I looked up the sensor you are using, and it looks there's a non-trivial temperature effect on the "operate" and "release" of the sensor about room temperature. I have never used them, but I've been presuming that optical would be superior.
31 January 2023 at 09:37 #631410
John Haine
Participant
@johnhaine32865
In my view one should avoid any magnetic material in the fixed part of the coil system. There clearly has to be some somewhere to be attracted by the coil, usually on the pendulum. But you want to avoid any spurious forces from remanent magnetism. With any reasonable Q the force needed for impulse is so tiny that a core should not be needed.
31 January 2023 at 09:51 #631413
Howi
Participant
@howi
I would have thought 5v power to the coils would not be enough to move a long pendulum and weight.

My recolection of the master clocks in telephone exchanges is that 50v was used.
31 January 2023 at 10:18 #631417
Tony Jeffree
Participant
@tonyjeffree56510
Posted by Howi on 31/01/2023 09:51:59:

I would have thought 5v power to the coils would not be enough to move a long pendulum and weight.

My recolection of the master clocks in telephone exchanges is that 50v was used.

5V is actually plenty for these coils – the issue isn't voltage but amp-turns, which basically determines the magnetic strength. I suspect the Post Office coils used many more turns of much finer wire. Telephone exchanges were based on 50V DC electrics so it was probably easier to make coils to suit the voltage than to mess around with a lower supply voltage. I believe I am currently running mine on 12V but that is massive overkill.

The John Wilding 3/4 second Pendulum Clock which was the inspiration for my design (and in turn, for this one) used a 3V supply (2x "D" cells in series).
31 January 2023 at 10:38 #631419
SillyOldDuffer
Moderator
@sillyoldduffer
Posted by Howi on 31/01/2023 09:51:59:

I would have thought 5v power to the coils would not be enough to move a long pendulum and weight.

My recolection of the master clocks in telephone exchanges is that 50v was used.

The power of an electromagnet is proportional to ampere-turns rather than voltage, so you get the same effect from hundreds of amps through a single turn at miniscule voltage, or a few milliamps through thousands of turns, driven by tens of volts. The engineer can wind a magnet coil to suit almost any voltage / current combination. Telephone exchanges used to run on 80V, lorries run on 24V, cars on 12V, electronics on 9, 5 or fewer volts. Contactors run on mains voltage. Relays are available for all of them.

My reaction to John mentioning his pendulum twangs is that the impulse is too powerful and/or slightly mistimed.

There are two cases though:
1. If the pendulum is started from stop by the electromagnet it has to be powerful enough to overcome bob weight inertia. As this is considerable when the bob weighs a few kilograms, a powerful magnet is needed.
2. If the clock is started by hand, then the electromagnet only has to be powerful enough to keep the bob swinging once it's going. The amount of energy needed to keep a well-made pendulum going is low because the main losses are stirring air and heating up the suspension spring, A weak electromagnet will do the job, ideally being only just powerful enough because excess energy upsets time of swing.
Timing is also vital. Like pushing a child on a swing, the impulse has to be timed just so. When the electromagnet is mounted directly below the bottom dead centre, it has to be pulsed just before the bob reaches BDC so that the bob accelerates, and then turned off quickly. If the electromagnet is still on when the bob reaches BDC, it becomes a brake, either removing energy from the pendulum with a bump, or stopping it entirely.

Dave
Edited By SillyOldDuffer on 31/01/2023 10:38:33
31 January 2023 at 22:23 #631517
John Purdy
Participant
@johnpurdy78347
SK
I had originally planned to use opto interrupters as I had them (Harris H2182 ) but after playing with the pendulum when first made it I found it was very easy to impart some sideways motion when moving it off to one side and releasing it to set it going. As the slots in my sensors are only 3mm wide, and there would be 4 of them spaced over about 2-2 1/2", I felt there was too much chance of the interrupting vane on the pendulum impacting the side of one of the sensors, hence the decision to use Hall devices. There were two other potential problems with with these devices: stray light activating them and they are quasi linear devices were the output doesn't switch rapidly when the beam is interrupted. John Haine has got around these drawbacks by using Sharp optos which have a 10mm wide gap and a built in Schmitt trigger output, which still leaves the possible stray light problem.

As to the temperature effects on the Hall effect devices, the data sheet I have shows that there is a maximum 10 Gauss change in the actuating or release flux between 0 and 25 deg C. Since the magnet I am using (.125" dia x .125" long neodymium ) has a magnetic flux of ~1200 Gauss at a distance of 1/16", the spacing between the magnet and the sensor I'm using, (according to info from the web site linked to by John Haine in another post here ) the difference in the position that the device would be activated for a 10 Gauss difference, I feel would be insignificant.
I don't think it would make any difference anyway as the time keeping is a function of the pendulum period and exactly when the impulse is sent to the clock would make no difference, only that the spacing between seconds might not be equal, but averaged over time would be correct.

Dave

About your comment about the "twang" I think you are correct in saying the the impulse is more powerful than needed. I am going to try and put some resistance in series with the coils and see how far I can lower the voltage and still get sufficient impulse to keep the pendulum going. Or I could also just lower the coils to increase the distance from the coils to the armature on the pendulum rod to decrease the magnetic flux.

I don't think there is a problem with the timing as the coils are de-energized just as the leading edge of the armature reaches the centre line of the coils.

John

Edited By John Purdy on 31/01/2023 22:39:23
31 January 2023 at 22:54 #631518
John Haine
Participant
@johnhaine32865
Just a data point, my small clock has a 25cm pendulum with a tiny neo magnet on the end swinging above a small air cored coil which has a resistance of about 200 ohms. It's impulsed for about 15ms every other swing or so from an Arduino output through another 220 ohm resistor. You really don't need much energy or force to impulse a reasonably high Q pendulum.

Impulse timing matters if the strength or phase of the impulse changes. If the phase centre of the impulse is at the centre of the swing it doesn't change the pendulum phase.
1 February 2023 at 10:21 #631550
Howi
Participant
@howi
Hi all

my post about 5v v 50v, I know that current determines electromagnet strength, I was aluding to the fact that a lower voltage would require a lot more current than higher voltages to produce a reasonable amount of electromagnetic force.

Oh! well, back to sleep, somebody wake me up when an interesting post arrives.
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