Clock projects are so common that they are almost a cliche. After all, microcontrollers have some clock source and are good at counting, so it stands to reason that a clock is an obvious project. [WilkoL’s] clock though has a most unusual clock source: a 440 Hz tuning fork.
A cheap plastic dome really shows off the fork and contributes to this good-looking build. An ATTiny13 divides the input frequency down, handles the display, and obeys the adjustment buttons. It does require a little metalworking, as the tuning fork needed filing and threading, although we bet you could figure out other ways to mount it.
As good as the clock looks, it is apparently impractical. The problem is that 440 Hz tone is audible. If you think a ticking clock will drive you mad, try a constant 440 Hz tone.
We were amused with the fact that the tuning forks were both a little low so they were tuned by filing material off the ends. Of course, the frequency is only set at a particular temperature and as it gets warmer or colder you might see some drift, but apparently not too much.
A more common choice is a crystal, which usually has a much higher frequency. Sometimes the clock source is the power mains.
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