Arduino Pendulum Clock Design - Comments Welcome

Ordinary steel is about 1e-5 per Deg C tempco which amounts to about half a second a day per degree. So temperature is probably the first thing to compensate. Carbon fibre is better than Invar, which is anyway hard to get and expensive. I think it's sensitivity to humidity is overestimated. It's cheap and easy to get in rod or tube form.

.

With some regret, Dave … I very much doubt if you are wrong.

MichaelG.

Regarding the Due's notion of 1 second. Yes I already spotted that it is slightly off compared to GPS. But I should look at this further and do some more detailed tests particularly regarding temperature.

Now for a word that may get you really thinking.....of course you may already have thought about this.

The word in question is......Ephemeris

Yep. I talking about the moon and its impact on gravity and hence the pendulum. My maths suggests it should be detectable.

A cheap clock was just a quick way to get started. I suspect the escapement maybe an issue quite quickly.

I managed to pick some invar relatively cheaply. Fused quartz looked interesting but noticed it needs to stretched. carbon fibre wasn't on my radar until now.

I suspect that the somewhat flexible ‘pendulum bracket’ might prove to be a problem, Glenn.

MichaelG.

.

P.S.__ Lots of good information, and some great photos of Shortt clocks here:

http://www.royalobservatorygreenwich.org/articles.php?article=1327

Edited By Michael Gilligan on 29/03/2022 22:57:47

And a good place to start too! Applying an ordinarily programmed Arduino to an imperfect pendulum clock will detect erratic running and working out what causes detected errors is educational. If an ordinarily programmed Arduino is applied to a very good clock, then the Arduino's own timing errors start muddying the picture.

By 'ordinarily programmed', I mean code written using the standard libraries without regard to any timing issues they might introduce. For example, digitalRead() and digitalWrite() are both very slow compared with directly manipulating ports because they do lots of friendly behind the scenes checking: they're easy to use, but slow. The alternatives are fast, but harder to program.

Dave