New Clock Maker

[carlwParticipant @carlw]

I am a retired construction electrician.  My long-time hobby has been building a workshop filled with tools that I have rescued and repaired.  Having pretty much finished with that, my current interest is in making clocks.  I built John Wilding’s Large Balance Wheel Clock and was disappointed in the noise the Hipp toggle made.  So, I designed and built an electronic Hipp toggle circuit which was published in Model Engineer.  That circuit used opto-interrupters to sense the location of the balance wheel and turn on the drive coil at the right time and length of time.  My next project is Wilding’s revision of the ME Jubilee clock by Edgar Westbury.  It quickly became clear that Hall effect transistors would be a much better sensor than the optos.  But that is a more difficult circuit. While researching Hall effects in clocks I discovered John Purdy’s circuit in the ME clock subforum.  I’m now heading over there to post a question about that circuit.

[John HaineParticipant @johnhaine32865]

Hall effect devices which simply produce a logic signal when they sense a magnet are very common (used in millions in cars etc), and cheap.  Just a transistor-like package with 3 leads, +, -, and logic out.

https://thepihut.com/products/hall-effect-sensor

for example.

The problem with HEDs in clocks is that they are somewhat imprecise because the magnetic field extends in space.  So it can be quite hard to control exactly where the impulse is applied and how long it will be.  They can best be used in a configuration where they for example simply control a gravity arm which just gets reset by an electromagnet.  Optos are more precise and can very simple to use.  The Sharp GP1A57 opto-interrupter is very good.

[ChrisLHParticipant @chrislh]

I’ve used an HED (incorporating a permanent magnet) in an IC engine ignition system. I’m not well up in electrics and it therefore came as a bit of a surprise to me to find that there were considerable mechanical forces attracting and then repelling the rotary “vane” (made from mild steel). Could be very upsetting in something delicate like a clock I imagine.

[carlwParticipant @carlw]

John: Thanks for your welcome to the forum.  The problem with optos is that the mounting of the pendulum allows it to move at right angles to its swing and a vane could contact the body of the opto.  This appeared to be serious problem when starting the pendulum from stop as I had no way of starting it in the correct plane.  I have since found a work around which may allow me to use the optos.

Chris: I am probably less well up on electronics.  I’m struggling to unlearn power on-off and learn to think in TTL’s sorta on and sorta off.  My knowledge of HEDs is also limited.  My magnet will be a 1/8″ NIB which will have a rather small attraction to the steel in the HED.

I see some experimentation in my future.

Carl

[John HaineParticipant @johnhaine32865]

That can be a problem.  One advantage of the Sharp device is that it has a wide gap and long reach so there is more margin for error on starting up. In my experience one quickly gets the knack of starting pendulums straight.

Normal HED sensor ICs have no ferrous material in them so magnetic interaction with the pendulum motion should not be an issue.  One  benefit of HEDs is that they aren’t light sensitive.  On two of my clocks using optos sunlight has caused a problem.

[carlw]

On carlw Said:

… The problem with optos is that the mounting of the pendulum allows it to move at right angles to its swing and a vane could contact the body of the opto.  This appeared to be serious problem when starting the pendulum from stop as I had no way of starting it in the correct plane.  I have since found a work around which may allow me to use the optos.

Chris: I am probably less well up on electronics.  I’m struggling to unlearn power on-off and learn to think in TTL’s sorta on and sorta off.  My knowledge of HEDs is also limited.  My magnet will be a 1/8″ NIB which will have a rather small attraction to the steel in the HED.

I see some experimentation in my future.

Carl

Carl, I hesitate to offer advice because building a Wilding clock means you’re a step ahead of me, at least mechanically.   However, what you’re doing has some common ground with my experimental high-accuracy pendulum clock project, which might help.  Ought to mention the clock comes with elaborate ways of measuring short and long-term pendulum performance: each beat of the pendulum, in so far as my opto-sensor system can be trusted, is timed to within about half a microsecond

My Mark 1 pendulum consisted of a steel bob hung from a thin carbon fibre rod, with no suspension at the top.   Instead the carbon-fibre rod flexes like a spring leading me to call it a ‘sprod’.    Consequences:

• The build is extremely simple
• The pendulum’s period is not predictable using either the simple or compound pendulum formula. (Doesn’t matter in my application.)
• Although the carbon-fibre rod has excellent temperature stability, the resin matrix turns out to be humidity sensitive.  Humidity alters the springiness of the rod and hence the timekeeping, a problem!
• Having a round rod with no constraint means the bob need not fly straight, instead following some ellipse, the period of which is unstable.

Although the elliptical path followed by the bob tends to straighten out, the bob’s flight path is disturbed by every impulse, and also by any vibration or air moving in the building.  Like your clock, starting the pendulum was a easy enough except it took over an hour for the period to stabilise.   For that reason, I’ve replaced the ‘sprod’ with a conventional flat-spring suspension, which greatly reduces the bob’s tendency to fly ovals.   The spring would also reduce the chance of a vane hitting the sensors.

If there’s room inside the clock, also possible to move optical sensors further apart.   Unlike Hall Effect Devices, which typically only react to a very local magnetic field,  an opto-sensor system will work over several metres if need be.

There are two basic types of HED, analogue and digital.   The analogue type measure magnetic intensity, which isn’t needed in a clock.  The digital type are more useful in that they switch instantly from OFF to ON whenever the magnetic field level passes a threshold.  This makes them good for timing applications like tachometers and clocks.

I know what you mean about learning TTL.   Actually, TTL and power control aren’t that different.    Conventional power control usually turn some device on or off with a system of mechanical switches, mainly manual, but also automatic such as thermostats etc.  Whilst mechanical systems were traditionally used to implement the rather complex logic required by traffic lights, washing machines, or CNC tools, it’s much easier to build the control circuitry with digital logic (TTL).  The electronics can be packed at high-density on to a low voltage printed circuit board.   The  electronics send low voltage control signals to the distant big-iron, with many advantages such as no need to run lots of separate power cables between the brain and the muscles.      These days discrete logic systems built with TTL are rare, because it’s often cheaper and easier to program complex logic than it is to build the same function from integrated circuits.

Although digital electronics are always ON, their outputs are always ON/OFF signals.   So rather than a human pulling a lever to operate a switch, the lever is pulled by a solenoid actuated by a TTL signal.

Welcome aboard – pendulum clocks are fascinating.

Experimentation galore – my clock is nothing but.   Got it tantalising close to working as intended but so far no banana!  There’s always some new problem to fix!

Which ME was your Hipp article in?  I’d like to re-read it.

Dave

 

 

[ChrisLHParticipant @chrislh]

John,

Thanks for the clarification of the HED set ups. So we have two options

Simple HED detector with small moving permanent magnet which sees no mechanical interaction and

HED unit incorprating permanent magnet with magnetic material vane which sees sizable magnetic effects (not mentioned in the device data although obvious enough if given a bit of thought). On the other hand, if the device data is to be believed, change point in space is well defined.

[carlwParticipant @carlw]

Gentlemen: I am delighted at the response to my divagations on the Jubilee clock project.  I’ll respond in more detail tomorrow or Wednesday.  I may miss a day or two now and then as I am tasked with taking care of my wife.

The Sharpe opto looks very interesting as I can now control the fore and aft movement of the pendulum to within its 3/8″ opening.  The idea of using separate devices – LED and opto-transistor – spaced farther apart is excellent.  The opto-interrupter of my MicroSet clock and watch timer has an opening of about 1″.  This is definitely do-able.  More experimentation is to be done.

My article on the electronic Hipp toggle circuit appeared in Model Engineer #4694 et seq.  John Purdy’s HED modification is here: http://First Attempt at an Electronic Hipp Clock | Model Engineer & Model Engineers Workshop (model-engineer.co.uk)

I took a few minutes to peruse the thread titles in the clock forum.  I now have a lot to read and learn.

[John HaineParticipant @johnhaine32865]

I don’t know if you have seen this site:

https://ve6aqo.com/New2023/Roger%20Jelbert%20cHipp%20Toggle/cHipp_Toggle.htm

Another interesting approach.

If you space the led and sensor further apart it does give more space but may be less precise as the beam width and aperture where the sensing vane passes will be wider.  You may find this site of interest:

https://groups.io/g/Horological-Science-Newsletter/topics

There have been a lot of discussions about pendulum sensors there, and other stuff you may find interesting. Also:

https://groups.io/g/synchronome1/topics

I posted a build thread there on my arduino controlled clock.

[carlwParticipant @carlw]

Thanks, John.  I perused the links and found one solution to my opto problem.  Use a flexible vane/flag!!  A piece of heat shrink tube would be perfect.  The second solution is the method of starting the pendulum accurately.  Just pull it to the desired angle of swing, place a suitable piece of wood between the pendulum armature and the backplate and let go.

Off I go to proto-board the circuit and get the pendulum running.

 

 

 

 

 

 

 

 

[John HaineParticipant @johnhaine32865]

I found the details of the measurements I made with an HED.   I had a 3mm dia X 2mm neodymium magnet 5mm above the sensor, which was an Allegro type on a breakout board designed as an arduino accessory.  The sensor went “on” at 1.5mm before bottom dead centre and “off” at 4.5mm after.  These numbers are very sensitive to the spacing, getting larger when the spacing reduced.  If the pulse from the HED was used directly to impulse the pendulum it would be decidedly lagging rather than centred.  In the application I am looking at though the HED would only be used to control the reset of a gravity arm, and the actual impulse phase is determined by the geometry of this and the pendulum.

[carlw]

On carlw Said:

…
My article on the electronic Hipp toggle circuit appeared in Model Engineer #4694 et seq.  John Purdy’s HED modification is here: http://First Attempt at an Electronic Hipp Clock | Model Engineer & Model Engineers Workshop (model-engineer.co.uk)

…

Thanks for the reference to ME4694, but the link to John Purdy’s modification has got mangled somehow.   Any chance of a correction please?

Ta,

Dave

 

[carlwParticipant @carlw]

Dave: Trying the link again: https://www.model-engineer.co.uk/forums/topic/first-attempt-at-an-electronic-hipp-clock/   It is currently at the top of the fourth page of the scientific instruments and clocks forum.  I’ll post this and test the link.

John: Your measurements of the HED response are most interesting and larger than I had expected.  This solidifies my decision to use optos.  The proto-board will allow me to move the optos to set the timing and duration of the drive pulse.

Carl

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