Piezo disc

Can someone please advise, on a piezo pick up disc what is the white coating to the disc centre on one side where one of the wires is solder connected , is it a ceramic coating ??

I bought a piezo for my first build, after its arrival from a slow boat from China and its removal from its packaging the white coating was split and then fell off in parts including the wire point.

I thought I might be able to re solder it but I strongly suspect its " Donald Ducked"

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  • The piezoelectric effect was discovered in 1880 by the Jacques and Pierre Curie brothers. They found out that when a mechanical stress was applied on crystals such as tourmaline, tourmaline, topaz, quartz, Rochelle salt and cane sugar, electrical charges appeared, and this voltage was proportional to the stress.

  • Same happened to me on two occassions, the wires came off the centre of the piezo. I re-solder mine back on. Both worked ok.

    Piezoelectric materials can be divided in 2 main groups: crystals and cermaics.
    The most well-known piezoelectric material is quartz (SiO2).

  • This is the best UK seller I have found
    £2.84 for ten prewired 20mm discs (my preferred size though she sells other sizes)
    http://m.ebay.co.uk/itm/10-20mm-Piezo-Elements-Sounder-Sensor-Trigg...
  • not sure now where i read about it but the first time i used a piezo as a pickup was around 1983... i tried to amp my acoustic 12 string. although it did work and it was surprising that it seemed to work no matter where i put it, even on the headstock. however the sound was not great. i had only started studying electronics then so i didnt know how to filter the screeching highs... lol.
  • Interestingly enough, the piezo disks we use were manufactured to be speakers for smoke detectors, burglar alarms, alarm clocks, cell phones, earphones, PA system and guitar amp tweeters, etc.  We are creatively reusing them, much like chopping a wall-wart for a mag-pickup, or using a voice-coil speaker as a mic in a stomp-box.

  • to use as a buzzer they need to be driven with an oscillator they change pitch if you change the oscillator frequency.
    fortunately the also work in reverse , which is why we can use them as pickups/microphones.
  • The ceramic is what vibrates as the top vibrates and somehow the mechanical vibrations are converted to electronic sounds. 

  • Thanks for the feedback guys, lesson learned on my first build ,don't skimp on the important components.
    • If you got it off amazon write a bad review or contact the seller they will probably send you a new one.
      • Shawn

        yes I got it off Amazon, I have been on to the seller and they did offer a refund, I asked them to just send a replacement as I couldn't be bothered with a couple of £ refund.

        To their credit they did get back to me promptly. will wait and see if I get a fully functioning one next time around but my future buys are going to be more local with the guarantee of a decent build.   

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