Show HN: Apple II clock using interrupts from physical pendulum clock

Re:Show HN: Apple II clock using interrupts from physical pe... by em3rgent0rdr on Sunday January 28, 2024 @12:23PM (#39167774)

Interesting idea to use an inductive sensor. I personally would have suggested a hall sensor (though that would involve fixing a tiny magnet to the pendulum) as the cheapest solution. But of course there are many ways to solve the same problem. Neat project, thanks for sharing!

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Re:Show HN: Apple II clock using interrupts from physical pe... by SomeoneFromCA on Sunday January 28, 2024 @01:02PM (#39168099)

The canonical way of using pendulums as time reference in electronic circuits, is to use magnetic pendulum coupled a special circuit (a bjt and an inductor) that would not only sense the pendulum but also reenergize it.

example: https://electronics.stackexchange.com/questions/685779/elect...

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Re:Show HN: Apple II clock using interrupts from physical pe... by wkjagt on Sunday January 28, 2024 @01:45PM (#39168561)

Oh cool I didn't know that existed. In my case I don't have to re-energize it because I use an existing mechanical clock.

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Re:Show HN: Apple II clock using interrupts from physical pe... by zokier on Sunday January 28, 2024 @03:45PM (#39169642)

If you are curious about this sort of thing, look up master pendulum clocks. They were precision clocks that provided electric timing pulses to network of slave clocks or other uses. Afaik they were common in mid-20th century

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Re:Show HN: Apple II clock using interrupts from physical pe... by totetsu on Sunday January 28, 2024 @06:56PM (#39171202)

Here I was imagining you had to wind your computer with a key every morning.

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Re:Show HN: Apple II clock using interrupts from physical pe... by wkjagt on Sunday January 28, 2024 @09:03PM (#39171951)

I also got a rotary encoder with the plan to use it with a wind up clock. So maybe one day!

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Re:Show HN: Apple II clock using interrupts from physical pe... by wkjagt on Sunday January 28, 2024 @01:42PM (#39168534)

Thanks! I liked the inductive sensor, because it meant I didn't have to change the physical clock in any way. And they were only like 5 CAD each.

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Re:Show HN: Apple II clock using interrupts from physical pe... by joezydeco on Sunday January 28, 2024 @12:52PM (#39168037)

My mind went to an optical sensor. Either interrupt a beam with the pendulum or attach a small reflector to the arm.

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Re:Show HN: Apple II clock using interrupts from physical pe... by NikkiA on Wednesday January 31, 2024 @06:03AM (#39202365)

Optical sensor would be the best option - both induction and hall effect will add a very tiny eddy current brake effect that will slow down the pendulum. Probably imperceptively, but it'll be there and will affect time keeping eventually.

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