Quartz of them, at least.
Back from vacation, delayed a little by Snowpocalypse 2010 II: The Wrath of James Caan (It’s NOT Snowpocalypse 2010; that was the storm in February). I didn’t know how much snow the DC area would get and it seemed foolish to drive in during the storm or just as the cleanup were to begin. (And the part of abandoning my mom with whatever snowfall was there. That would have been bad). Turns out that DC got almost nothing — it had all melted by Wednesday evening — and Niskayuna got around 6″ (an amount easily handled), though you didn’t have to travel too far to find pockets which had gotten a foot or more, especially up in the hills. Further south and east got dumped upon. My route back, which was inland (Rt 88 to 81 to 15 to the beltway), was all clear.
So here’s a video about how a quartz watch works, which I found via fine structure
two weeks ago in saint paul/minneapolis we got 23″. that is one of the three largest snowfalls for the twin cities. and now we have broken the snowfall record for December. in think the best witty description of the snow isn’t snowpocalypse, or snowmageddon, but snOMG.
but it’s all good. i just got a snowblower. 🙂
The excitation confuses me. I would have thought that, with the direct current from a battery, the crystal would merely deform a single configuration until the current was removed. You certainly can’t apply a single stress to a piezoelectric crystal and have it continuously generate a potential; the inverse would be that you can’t apply a single potential and have a continuous (and sinusoidal) stress, i.e., vibration. Is there circuitry to use the dc from the battery to apply pulses to the crystal?
You take the output, amplify it and feed it back into the circuit, and as long as you have sufficient gain it will oscillate at the resonant frequency. There will always be some signal at the resonant frequency when you start it up (noise or a Fourier component of the turn-on step)
Ah, I see. Thanks.