Piezo buzzers are one of the most common buzzers available around, they got their name from the piezoelectric material used as the active element.
These buzzers are usually driven at a relatively higher voltage but low current, consumes a little power, but still capable of producing very high sound.
So, here we’re going to build and test a simple piezoelectric buzzer circuit , lets get started …
You’re going to need few very basic components for this simple piezo buzzer circuit.
- One BC548 transistor, or other similar NPN transistor.
- One 10kΩ resistor.
- One 100kΩ resistor.
- One self drive 3 terminal piezoelectric buzzer.
- One 1-10mH inductor coil, details below.
- A power source of course, 6V to 24V.
The Piezo element must be a three terminal one, like in the picture.
The blue wire is connected to feedback(F) terminal, red wire to the main (M) terminal and the black wire to the piezo element’s ground(G) plate.
The inductor coil’s value and shape is not crucial. You can use any coil from 1mH to 10mH or more, or even no measured value at all. I used a 40 turn coil on a small ferrite toroid in the final design.
Circuit diagram and construction
Lets have a look at the circuit diagram,
Note the piezoelectric element’s pinout, M is the main terminal, F is the feedback terminal and G is the ground plate.
The circuit is fairly simple, you can use a little piece of strip board to make it. As this piezo buzzer circuit uses very few components, so it also could be constructed by soldering the components to each other.
My sample prototype, I opted for soldering the components to each other.
Buzzer construction notes
The wires connecting the buzzer’s Main and feedback terminal MUST be very flexible and thin, else the buzzer won’t work !
Why ? The piezo element produces a very little displacement, possibly in range of few micro meters only. The flex force ain’t that powerful to overcome the pressure from connecting wires.
Did you notice the two copper coils in the above picture ? I used them to minimise the pressure from connecting wires, but it was pretty impractical. So later removed those and and soldered two thin and very flexible wires, that just worked.
I also replaced the 5mH coil with a 50 turn coil on a ferrite toroid. Now all components fits nicely inside the buzzer’s housing.
How this piezo buzzer circuit works ?
When A voltage is applied to the electrodes of the piezo element, they produces flex in either way. This flex force bends the ground plate up and down.
The exact opposite thing happens too, when a a piezoelectric element is subjected to varying pressure, it produces voltage.
As you’ve seen before, self drive piezo buzzers are constructed with an extra electrically isolated feedback electrode. The voltage created by the flex force is available in the feedback terminal.
The piezo buzzer is placed in a resonant cavity, there is a hole in the opposite side of the resonant cavity from where the buzzing sound comes out.
The driver circuit and piezo buzzer co-operates soon between themselves and they starts oscillating on the resonant frequency of the piezo buzzer.
So that’s it, construction of a simple piezo buzzer circuit, I could write more about it’s operating principle, but that’s not necessary here.
Need a buzzer that sounds good ? Here is the more pleasant sounding piezoelectric buzzer circuit .
And what if you want to make a magnetic buzzer circuit ?
If you’ve got some suggestion/question/problem, just leave a comment, I’d like to hear from you !