I've been working on this clock for the last few weeks, and finally it is working. Please note that this is a test-bed for some ideas I have had churning in the back of the brain for many years, and is not (in this form at least!) intended for hanging on a wall somewhere, although at some point I will probably do the necessary tarting up to make it (or a Mk 2) domestically acceptable! There's a rather terse description in the YouTube entry, but I am writing it up in gory detail as we speak.

Edited By Neil Wyatt on 12/03/2021 11:10:21

The third sensor allows me to control when the impulse starts and finishes, based on the position of the pendulum. It was a design objective to make the pendulum as free as possible, and therefore maximise the number of swings between impulses, so I'm deliberately not aiming to impulse it on each swing, which is rather different from your approach by the sound of it. The rod is Invar. It has only been running since 10pm last night so I haven't sorted the rating yet – it has lost 20 seconds in 16 hours, but that is without any attempt to adjust the rate.

The motion work/dial is a Quartz clock movement with the electronics ripped out, so just the Lavet stepper and the gearing remains. The "ticks" are taken from the activations of the middle sensor.

Interesting approach! Yes, the stepping of the clock movement is entirely under the control of the micro, so it would be possible to give it a similar electronic rating mechanism. The I/O capability of the micro is a bit limited though, so short of embedding the values of N and M in the software, adjusting the rating would be difficult. Having said that, it will take live software updates via USB (or Bluetooth for that matter) so definitely a possibility.

The BBC Micro:bit supports BT – you can programme it via a phone or a tablet with their app, which is pretty neat.

I'm dead impressed with the Micro:bit so far – mind you, what I am asking it to do isn't very taxing, but the ease of programming and setup is excellent.

I agree – often Vs infrequent impulsing is an interesting debate. I haven't studied the subject enough to have a fixed opinion, but I suspect the fact that the Shortt clocks used infrequent impulsing may be telling us something. The reason I chose to use infrequent impulsing in this clock was that there was a certain appeal to me to build a clock that emulated the swing arc control of the Hipp mechanism, but where the sensing and impulsing is non mechanical, and where there is no mechanical linkage between the pendulum and the motion work. After all, if it was accuracy I was after I would have stuck with a £5 quartz clock.movement.

That's interesting, thanks…looks like a very similar sensing setup to mine, but all the logic hard wired rather than using a micro.

Thanks Dave – yes, the Micro:bit is a great little device, and perfect for this kind of application.

I haven't attempted to characterise the precision (or otherwise) of the Hall-effect devices I am using – I suspect that they are likely to be inherently less precise than a well set up optical sensor, but they have their issues too as you have discovered. For the moment I am happy to have it up and running; I will see how it performs over the next few days.