Testing Piezo Buzzer Help

Discussion in 'The Projects Forum' started by Netwaves, Feb 12, 2015.

  1. Netwaves

    Thread Starter Member

    Feb 9, 2015
    44
    1
    I need help understanding how a piezo buzzer will affect my circuit. I have a couple of piezo buzzers. They are essentially black boxes with circuitry inside and no information. The only information I have is "works with 6VDC to 24VDC." I have pulled a couple of them apart and they are all different, one has some resistors, transistors, and a coil and the other has an IC. My questions are:

    01. How can I test them to find resistance and amperage?
    02. How can I calculate their effect on a circuit. Should I find their resistance and essentially put them in the circuit as a resistor?
    03. They seem to cause noise in the DC circuit. It seems the amount of amperage they pull fluctuates while in use. How can I stop this?

    Any help would be greatly appreciated. TIA
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,804
    1,105
    1) Apply 6V DC and measure the current drawn.
    2) From the measured current you can use Ohm's Law to calculate the effective average resistance.
    3) You can't stop the fluctuation without stopping the sound! You can, however, connect capacitors directly across the buzzer terminals to try to reduce interference generated.
     
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  3. Netwaves

    Thread Starter Member

    Feb 9, 2015
    44
    1
    How can I calculate the value of the capacitors needed?
     
  4. Netwaves

    Thread Starter Member

    Feb 9, 2015
    44
    1
    I've now tested a couple of them:
    Buzzer 1 12VDC 6.6mA and I came up with 1818 ohns. Does this seem correct?
    Buzzer 2 12VDC fluctuates wildly between 20mA to 26mA constantly. Should I take the middle ground of 23mA?
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,804
    1,105
    1818 is right. However, bear in mind a buzzer is not a pure resistor; it has capacitance and inductance, too.
    Assume 23mA (it's only an approximation anyway, because the fluctuations affect the meter accuracy).
    As for capacitor values, it's a matter of trial and error rather than calculation, since it depends what else is connected to the buzzer. Try ~100uF (rated for 16V or more) electrolytic for starters.
     
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