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tamiwiki:projects:piezo [2023/11/25 13:27] – yair | tamiwiki:projects:piezo [2023/11/26 08:21] (current) – [more] yair | ||
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+ | metatag-description=(Piezo stuff) | ||
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had a nice page in oldwiki, here's a reboot. im placing it for now. | had a nice page in oldwiki, here's a reboot. im placing it for now. | ||
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=== Piezo === | === Piezo === | ||
- | see: how to make a contact mike: using piezo disks to pick up tiny sounds | + | see: how to make a contact mike: using piezo disks to pick up tiny sounds, chapters 7-8 |
=== contact-mic-circuit === | === contact-mic-circuit === | ||
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+ | A piezo element can be thought of as a sound-dependent voltage source in series with a large capacitance of about 15nF. Here the trouble starts. You need to put this into a load which is higher than the impedance of the series capacitor at the lowest frequency of interest. If that is 20Hz, since the impedance of the capacitor is 1/2pifreq*C then you want that to be > 530k. I’ve terminated mine in 3.9M because that’s what I had to hand. | ||
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