15 Pieces - 41mm Piezo Disc Elements with 4" Leads, Jumbo Contact Pickup CBG Cigar Box Guitar DIY

These things are great. Not only can they be used to sense vibration, they can also be used to deliver vibration, like for high impedance headset uses, buzzers, whatever. Connect the wires to an input amplifier to use them as a sensor, or connect them to a high impedance amplifier's output to use them as a speaker of sorts. My use for them so far is strictly as a sensor, and they put out such a large signal at such a high impedance that they are a perfect match for high impedance, high gain configured op-amps for detecting truly faint vibration. Here's where the problem comes in, though. I've been using them as vibration sensors for outdoor uses, in a high humidity environment. Some of them seem to want to last forever out there, and my God do they deliver for the job I put them on, but ultimately they were suddenly dying for no clear reason other than humidity *seemed* to be at the heart of the problem. I found that where before their impedance was so high my DMM couldn't read it, suddenly one of the "dead" ones was reading 4.6 megohm, which for the design of the amplifier might as well have been a dead short and rendered the whole device useless. The heartbreaking part was that I had JUST put it in there as a replacement for one that had slowly corroded for over a year and died the same way. This one took less than 24 hours to develop the same problem. Thinking by now that the flux residue left on them from soldering in the factory where they were made was perhaps taking on water from the high humidity, causing the "short", I wetted a paper towel with acetone and scrubbed the central disc side. That had seemed to work with another, but this time nope, no dice. So I tried again with alcohol. Nope, still 4.6 Megohm. Tried vinegar thinking "what if it's a metal film on there?", nope. I bombarded it with so many solvents that I figured I had nothing to lose, so I hit it with 90% alcohol and scrubbed hard with a toothbrush, again on the central disc (red/positive contact) side. Looking close while doing that, I saw what looked like a tiny thread come loose of the central disc, right at the edge and close to the red wire solder joint. I continued, working all around the edge of the piezo disc, and saw a little more of the same come loose. Before it was even dry, I checked with my DMM, and woo-ha!!! Infinite, even on the 20 Megohm setting. Looks like I was right - humidity gets into that flux residue and causes their impedance to drop into the low Megohm levels, which if you're doing crazy, extremely high impedance work with them, reads as a short and will at least seriously reduce your performance, or in a case like mine, throw it right off the map. I cleaned the newly ressurected disc up as pristinely as possible, and then sprayed the whole disc down with a couple coats of Rustoleum Crystal Clear Enamel for good measure. That might have been a mistake - it might bring back the same kind of problem when the humidity is high - but it cleans off easily enough so IMHO it's worth a test, and if it works out it will help keep the metals from corroding out there. For now though, it's back to life, and I didn't have to scrap yet another disc. So remember that: If you get dead discs, especially if you're working with very high impedances, try scrubbing them with a toothbrush and alcohol. I think you'll find it's all down to that flux they didn't bother to clean off of them.And then, sit back and enjoy one of the most amazing, stupid simple electronic devices I've ever seen. A million and one uses for these, for sure. :-)PS: They produce a voltage when they are mechanically distorted. In common uses, this means sound traveling through the metal, big deal. But, bend them just slightly, like stand one on edge and press down just soft and gentle, and they go mad crazy with output. Lay one on ring shape just big enough to support them, and press again very gently in the center and they go crazy with output. Once you know what they like, you can exploit that and make incredibly sensitive mechanical vibration sensors with them. So sensitive you can throw a simple 5VDC transimpedance op-amp design right off scale with the gentle tap of a toothpick. They're AMAZING.

Works well for my cigar box guitars. Mounted on inside the box under the bridge gives a nice twangy tone

Great price. Great output. Great shipping. There are sO many resources for information regarding what you can do with Piezo and that just makes the product so much better in general because of the free support from over 30 years now. I'm using these for midi drum triggers but I kind of get distracted easily so I made an electric wine glass with one just to test it out. If you hook a 10k Ohm resister in parallel between negative and positive leads the voltage wont bounce around constantly and feedback from a live speaker is reduced. It acts as a gate/eq I suppose. I'm having fun and that's what I bought them for.

Just what I needed to make some crystal headsets or a suitable substitute for high impedance headsets

These have been useful for DIY e-drum triggers.