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# Transducer Piezo: Is it a buzzer?

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#### Screech

##### New Member
Is this transducer piezo a buzzer? :?

I hooker it up to a 9 Volt. battery( black lead to negative and red to positive) but no sound came out.
I then hooked it up to 12 volts, but no sound.
What am I doing wrong?

pic attached.

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From what you say, I guess it is only Piezo-plate without oscillator circuit. For Piezo buzzer to make sound, it requires an oscillator with frequency of around 3kHz. This thing will work only after you connect a sine/square wave oscilaltor to it.

Check this oscillator circuit from "CyberCircuits"

Piezo or Buzzer

There is basically two different types of "piezo buzzers."
One type has an electronic circuit inside the case and the other type consists of only a diaphragm.
I distinguish between the two as follows:
A piezo "buzzer" or "sounder" or "screamer" has an electronic circuit inside the case and when a DC voltage is applied (with the positive connected to the red lead) a sound will be produced by the device. This sound is generally a very loud high-pitched note but it can also be "beep-beep-beep" as used by trucks to indicate reversing.
The other type of piezo device is called a PIEZO DIAPHRAGM.
If you connect it to a DC voltage, you just get a very slight "click."
It must be connected to a "signal."
This "signal" can be almost any type of waveform (sinewave or square wave) with a frequency of approx 4 - 7 kHz.
A piezo diaphragm will have a resonant frequency (such as 4.5kHz) and when this frequency is delivered to the unit, the maximum output will be achieved. As the amplitude of the frequency is increased, the output will also increase.
The output of the diaphragm will also depend on the "quality" of the device and you can get a surprisingly good output from devices used in watches and Christmas cards.
This brings me to the point of your question.
The device shown in the photo is a PIEZO DIAPHRAGM and as such requires a driving signal.
A simple oscillator (such as a square wave) from a Schmitt Trigger will drive the unit and if you use a more sophisticated circuit with parallel inductor, the output of the diaphragm will be "ear-piercing."

I hope this is enough for a start.

Colin Mitchell

Last edited by a moderator:
Understood.
so, I've connectted it to a 555 timer(is that ok).
It's making sound.
It's not loud but probably not in the 3-7 khz. range.
I'm not using a resistor to it. Should I be using one?
I'm using a nine volt battery.

Resistor isn't necessary.

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