Thanks Mike, Apparently DARPA is looking onto the possibility of harvesting electrical power from piezoelectric sources.
See the following Wikipidia article: http://en.wikipedia.org/wiki/Piezoelectric About a third of the way down the Wiki article is the following tantalizing but brief sentence. "A similar idea is being researched by DARPA in the United States in a project called Energy Harvesting, which includes an attempt to power battlefield equipment by piezoelectric generators embedded in soldiers' boots." * * * * Such research does make me wonder how much practical electrical energy can be harvested and/or stored from the right combination of piezoelectric crystals. Correct me if I'm wrong but is it correct to assume that if we know a particular piezoelectric crystal's harmonic frequency, and then we proceeded to "bang" it or stress it at its specific harmonic frequency that by doing so is likely to be the best way to maximize the amount of potential electrical energy that can be "harvested". Incidentally, I DO know that these crystals generate extremely high voltages, sometimes in the range of 10,000 to 25,000 volts. What I'd like to know is how much amperage is associated with such stratospheric voltage readings. One assumes the amperage readings must be quite small. Never the less, I wonder if certain crystal combinations could possibly increase the amount of amperage that could be harvested while simultaneously maintaining extremely high voltages. Any thoughts? Regards, Steven Vincent Johnson www.OrionWorks.com > > Steve, > > The electrical model of a piezoelectric generator is a > voltage source in series with a capacitor. This means > you can't get DC out of such a generator, but you can > get high voltage bursts by hammering a crystal as in > a charcoal grill igniter. The snap you hear is in part > a hammer hitting a chunk of barium titanate or the like. > I don't know what the peak power in the spark is. In > principle, you could build a generator that whacks > crystals repetitively and if you are clever, it might > even be fairly efficient. It would be a gross mismatch > to general electrical and electronic practice, which > emphasizes high current and low voltage from > electromagnetic generators. > > Mike Carrell
