A piezo buzzer circuit is quite popular to make feedback or alert sounds. You can find them in wristwatches, cars, medical devices, sirens, panic alarms and like so.
In a previous post I wrote about how to make a self driving piezo buzzer with a 3 terminal piezoelectric element.
That buzzer works well, but makes just high pitch buzzing sound, why not improve it to make the sound pleasant to the ears ?
It’s rather a simple piezo buzzer circuit, just a transistor and a UM66T ic with few other passive components are enough to make it.
- One piezoelectric buzzer, 2 or three terminal
- One UM66T or BT66T IC
- One BC548 transistor or any equivalent NPN transistor
- One 4.7kOhm resistor
- An inductor coil, 1mH to 20mH, no exact value
- A power supply, 4.5 volt to 12 volt
- A little switch, optional
The inductor coil’s value is not much important, you can use anything between 1mH up to 100mH. It also doesn’t needs to be a sophisticated one. You can make it by winding 50 turns of enameled copper wire on a iron nail !
In this piezo buzzer circuit, the piezoelectric element doesn’t needs to be a 3 terminal one, as it will be driven by the UM66T IC.
The IC BT66T or UM66T are essentially same thing, you can use any of them. More details and pinout of the UM66T IC here.
Circuit diagram and project construction
This buzzer circuit is so simple that you could make it just by soldering the components to each other. But using a small piece of PCB or strip board will make it more sturdy.
Lets have a look at the piezo buzzer circuit diagram
I made the circuit just by soldering the components together, not so neat !
I salvaged the coil from a broken CFL, inductance rated 5mH.
Note that the coil’s DC resistance must not be too high, typically less than 100 Ohm. Else the buzzer will start misbehaving.
How this piezo buzzer circuit works ?
The UM66T IC is the heart of the buzzer circuit, it makes the nice mono tone sound, which is a pulsating DC.
In the next step, the pulsating DC current is amplified by the BC548 transistor, the amplified output is available at the collector of the transistor.
The transistor’s collector pin is connected to the +ve of the power supply/battery via the inductor coil. As the current through coil varies, it produces high voltage spikes according to the varying music output from the UM66T IC.
Then the high voltage spikes goes to the buzzer’s main electrode through the connecting wires and makes loud sound.
That’s all about how to make a good sounding piezo buzzer with a 2 terminal piezo elemen. Leave your questions and suggestions in the comment section.