Help with Piezoelectric Speaker

Discussion in 'The Projects Forum' started by zharvester, Sep 24, 2009.

  1. zharvester

    Thread Starter New Member

    Sep 24, 2009
    2
    0
    Hi,
    Im using a Piezo Audio Indicator model KPE-276A
    http://www.datasheetarchive.com/pdf-datasheets/Datasheets-12/DSA-228130.pdf (not using the KPE-276 because this one is louder..)

    It is part of a Circuit which can get 12-24V and since it can tolerate up to 20V i put a resistor 500 oham in serial to it.

    simple schematic (w/o the relay and holding circuit):
    Vcc-------Resistor-------Speaker-------GND

    The Speaker works but sometimes it makes a very low sound as if choking.
    when i connect it directly to Vcc 12-20V it works perfect allways.

    Is there a problem connecting a resistor to Piezoelctric device ?
    Do i need a different resistor or maybe put diode instead .... ?

    Thanks in advance.
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
    Hello,

    Perhaps you could use a 4.7 Volts zenerdiode in series.

    Greetings,
    Bertus
     
  3. zharvester

    Thread Starter New Member

    Sep 24, 2009
    2
    0
    Thanks, I did run it with Zener and it worked fine, but so did the Resistor in the begining (i found the problem few monthes after the card started to work...)
    I want to understand why the Resistor is causing Problems.

    Thanks again.
     
  4. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    It is supposed to be driven from a low impedance supply.
    Its voltage varies wildly when it is fed through a resistor. The resistor reduces the voltage only for part of the cycles.
     
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