![]() ![]() Choosing the right value for resistor R1 largely depends on your specific application. The signals entering the circuit through the “PIEZO_IN” connector is handled by the first op-amp (IC1A) of IC-TL072P. Let me quickly walk through the schematic: It’s very easy to build the electronics for this using a FET, but I opted for a more effective idea. If we don’t match this, we get all sorts of humming, buzzing, and noise - all associated with low-level signals. Because the piezo disc has a very high impedance (1 MΩ typical), it should be buffered to avoid possible impedance mismatch with an existing audio system. Furthermore, a ceramic piezo disc can conform to an odd surface.Īctually, the piezo disc can put out a lot of signal and hardly needs any amplification, but buffering is essential, and that can be done through several methods. The ceramic is more self-resonant, efficient, and less expensive.įor applications in which flat frequency response isn’t necessary, a ceramic piezo disc is a good choice because it can produce a larger signal and is shielded better due to the larger disc on one side. Actually, piezos generally come in two types of materials: ceramic and polymer. At the heart of the contact mic described here is a ceramic piezo-disc, which can be mounted with double-sided adhesive tape to a surface for capturing structure-borne sounds.Ĭeramic piezo discs are inexpensive they are like sonic microscopes and allow us to make very simple contact microphones to probe for secret sounds. ![]() Unlike other microphones, a contact microphone makes you look at the world in a different way. ![]()
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