Here, I am going to summarize my experience with piezoelectric transducers and their characteristics, possibilities and limitations, as well as some practical advices on their usage.
The piezoelectric effect is the ability of certain materials to generate an electric charge in response to applied mechanical stress, and, reversly, produce force and vibration when subjected to an electric field. As a result, piezoelectric transducers serve as highly versatile sensors and actuators. Their minimal size and weight, effectiveness, and resistance to electromagnetic interference (EMI) make them valuable in various applications, especially in active vibration control of light, resonant structures.
Common forms of piezoelectric transducers:
ceramic discs(PZT - Lead Zirconate Titanate, BaTiO₃ - Barium Titanate, etc.): stiff, brittle, and highly efficient materials commonly used in actuators, ultrasound transducers, and industrial applications;
polymer (PVDF - Polyvinylidene Fluoride): lightweight, flexible, with good piezoelectric properties, often used in sensors, wearable electronics, energy harvesting and biomedical applications;
single-crystal: natural (quartz - Silicon Dioxide) or artificial (Lithium Niobate, Gallium Orthophosphate), used in precise timing applications, optical and telecommunication technologies, frequency control devices.
The most practical material for vibration actuation and sensing experiments are ceramic PZT discs, due to their high sensitivity, low cost and easy supply in various sizes.
Preparing an electrode.
First, you have to solder the wires to the piezo disc. Use shielded cable to prevent interference, the thinner the better, as stiffer cable will pull the electrode introducing some external mechanical stress. Use rather low soldering temperature, about 300-350 degrees Celsius, and try to do it quickly. The piezo disc is a fragile element, and excessive heat can damage it. Solder the shielding to the side of the transducer and apply cyanoacrylate glue to the electrode, evenly covering the active element. This will protect the contact point and allow you to touch the transducer without producing noise. Solder the TS jack to the other end of the cable and the electrode is ready to use.
Vibration sensing.
Piezoelectric discs, due to their high impedance, behave similarly to capacitors, with typical capacitance values ranging from a few picoFarads (pF) to several nF, depending on the size and material of the disc. This capacitive nature means that the transducer can store electrical charge when subjected to mechanical stress, and depending on the preamplifier circuit, the resulting signal can either represent the force applied to the disc (charge amplification) or the amplitude of the vibration (voltage amplification).
Connecting the electrode to the typical microphone, or prefferably a high-impedance (Hi-Z) guitar preamplifier should be enough for first experiments with vibration sensing. Beware of the levels, as the piezo disc can produce high voltage peaks, especially when struck or bent. For testing, try gently sliding it across textured surfaces like a carpet, wall, a sheet of paper or a carton box. Try tapping with your fingers while holding the electrode. For best results experiment with light and stiff structures - membranes, wooden or metal plates, sheets, etc.
To be continued...