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Noob piezo resonator question:

Discussion in 'Electronic Components' started by The First Blarg on the net, Sep 12, 2007.

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  1. Sorry to be such a novice, but can someone tell me if a piezo electric
    crystal resonator will make an audible sound
    if I hook it up to a small battery?
    I'm looking for any miniature lightweight electronic sound generating object
    for a miniature toy I'm developing.

    I have small transducers that work well, but I'd like to go smaller and
    someone said piezo crystals are what they use
    to make watches beep, etc.

    Thanks in advance.

    P.S.

    I've seen some the specs for which mention 1.8 mhz to 50 mhz as the
    frequency range, but I'm guessing
    all of the above will be inaudible(?)
     
  2. Nemo

    Nemo Guest

    Sorry to be such a novice, but can someone tell me if a piezo electric
    You are on the right track but you have a number of half truths which
    are misleading you. Here's the rest of the story.

    Piezo devices come in all kinds of frequencies from audio (sub 20kHz)
    through ultrasonic (60kHz is the kind of freq they used to be for things
    like position sensors) to MHz these days (not sure what they use those
    for, probably all kinds of things). Anyhow, you want the audio frequency
    ones. You can find these in various catalogues like Digikey under
    headings like "piezo sounders".

    There ARE a few with a circuit built in which just need a battery
    attached but most need an oscillator attached. For the loudest output,
    one which resonates at the resonant freq of the piezo element as it
    flexes. Piezo devices usually have a fairly sharp resonance so are good
    for high pitched beeps but not for speech reproduction (speech is
    generally below, um, 4kHz I think and piezos only really start making
    appreciable volume at 2 - 4kHz). Although for very small air volumes
    like inside your ears, piezos can produce a better range of sounds -
    don't ask me why - which is why iPod earpieces use them.

    The two main sounder technologies (for small items anyhow) are piezo and
    electromagnetic (coil). Coil sounds better for audio but is only about
    2-5% efficient so for battery operated things piezo is often used - a
    massive 10% efficiency, = longer battery life. Piezo usually needs 2-4
    times as many volts to give te same volume as coil, but because it needs
    less current it's less power overall. For a battery operated toy, piezo
    is probably cheaper and will definitely give you more battery life.

    What you need is an example circuit here, but I've run out of time.
    Um... try googling "piezo circuit", this gives you various example
    pages.

    Oh one other thing. Piezo elements are sometimes sound as bare disks.
    Don't buy them unless you know what you're doing as you then need to
    build a cavity round them and somehow attach wires. For your first piezo
    circuit, at least, go for one with a plastic moulded case and 2 actual
    pins or leads. Some have 3 pins, which use a different circuit to drive
    them.
     
  3. Thanx for the response! You are the only one who answered me. All I need
    is the smallest, lightest
    thing that I can hear. A beep or even continuous tone. The beep tone from a
    wristwatch would suffice.
    I know virtually nothing about circuits, but I will take your advice and
    google piezo circuits.

    Anyway, many thanks!

    K.
     
  4. Gary Tait

    Gary Tait Guest

    Another option might might be the sort if ring sounder they use in cell
    phones.
     
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