I understand that there is a small circuit board keeping time and turning power and and off to the lights (or something like that). But what is physically moving on the circuit board, to keep track of the time?
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A crystal oscillator, typically.
It is surprisingly simple once you know how it works. You know how a wine glass makes a very pure tone if you tap it? Notice it’s always the exact same tone too. The frequency it resonates at is determined by it’s shape and the material.
Now imagine a slightly smaller glass. It’s pretty easy to predict that it’s going sound a little higher in tone, right? Because the resonance frequency is higher.
Now let’s keep at it and keep shrinking it until it’s smaller than a grain of salt. It’s a little hard to tap now, of course… But what if we could tap it with electricity though? Enter piezoelectric materials! They also have the benefit of not only doing a little “jump” when you apply electricity, but they even send a little electric pulse *back* after their little jump.
So you just poke it at the same rate that it pokes back and you’ve got a clock frequency going.
Keeping track of time then is just a simple matter of counting cycles of the clock.
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