Piezo buzzer operation

[Rajinder]

Hi all,
I have attached a diagram showing a 3 wire piezobuzzer connected to a micro.
I am not sure how this works.
I think you apply a voltage between the main and ground terminals. The feedback is then used to keep the buzzer oscillating around its resonant freq. I am not sure how the component values are selected.
Can anyone help me to understand this?
Thanks in advance

 

[bertus]

Hello,

Have a look here:
https://electronics.stackexchange.com/questions/18212/whats-the-third-wire-on-a-piezo-buzzer

Bertus

 

[Rajinder]

Hello,

Have a look here:
https://electronics.stackexchange.com/questions/18212/whats-the-third-wire-on-a-piezo-buzzer

Bertus

Hi,
I have already seen this. However the circuit that I uploaded does not have a transistor in it. I think it needs a 'kick' to get it oscillating, then the feedback keeps it going. Not sure how you select the resistors and capacitor values.
Thanks

 

[Audioguru]

An oscillator does not work with magic, instead it works from a battery or power supply providing energy to a transistor amplifier that drives and takes feedback from the piezo.
A piezo buzzer or beeper has a transistor in it and it produces the frequency of the piezo in its resonant housing.

 

[Rajinder]

An oscillator does not work with magic, instead it works from a battery or power supply providing energy to a transistor amplifier that drives and takes feedback from the piezo.
A piezo buzzer or beeper has a transistor in it and it produces the frequency of the piezo in its resonant housing.

Thanks for the reply. My other question is, how are the component values selected?

 

[Audioguru]

We simply buy a piezo beeper, nobody makes it themself. To make one you must buy the piezo beeper then break it apart to take the 3-terminals piezo disc that is not sold by itself.

Then you must go to school to learn how to make a very simple transistor amplifier. You will learn how to select component values.
Or maybe you can find the datasheet of a piezo beeper and it might have a circuit showing the component values they selected.

 

[Harald Kapp]

To make one you must buy the piezo beeper then break it apart to take the 3-terminals piezo disc that is not sold by itself.

Not by itself but by Amazon.

 

[Alec_t]

I am not sure how this works

I'm guessing the micro would output driving pulses to the main piezo terminal and monitor the strength of the signal picked off from the feedback terminal. It would the adjust the driving pulse interval to maximise the signal strength.

 

[Audioguru]

Not by itself but by Amazon.

Amazon sells cheap clothing and shoes.
I didn't know that their sellers break apart cheap Chinese piezo beepers then sell the piezo wafers. Oh, defective piezo wafers?
Then I guess Amazon sells anything.