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Make this Simple Buzzer Circuit with Transistor and Piezo

Make this Simple Buzzer Circuit with Transistor and Piezo

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In this article we learn how to make a very simple circuit for buzzer using piezo electric transducer, two resistors, a small coil and a BC547 transistor.

Simple Buzzer using a Single Transistor

Just a single transistor, a ferrite inductor, and a piezo transducer, that's all you will need to make this circuit “buzz” or rather “twit” for you, with an output that may be quite loud and ear piercing.

The simple piezo buzzer circuit described here actually works in a quite unique way. Instead of the normal working concept employed by other forms of oscillators which require resistor and capacitor networks for generating the oscillations, this circuit use inductive feedback for the required operations.

simple buzzer circuit using a single BC547 transistor, piezo 27mm and an inductor

How it Works

Referring to the above buzzer circuit diagram we find that the transistor T1 along with the inductor forms the heart of the circuit.

Basically the coil which is specifically called the buzzer coil, is in fact positioned for amplifying the created oscillations while the actual feed back is provided by the center tap of the three terminal piezo element used for the present application.

When a voltage is introduced in the circuit, the transistor conducts, operating the piezo element across the buzzer coil, however this also leads to the grounding of the base of the transistor through the center tap of the piezo element, this instantly switches off the transistor and in turn the piezo also switches off, releasing the base of the transistor.

The transistor reverts to its original state and the cycle repeats, generating oscillations or the required “buzzing” frequency.

The center tap from the piezo transducer plays an important role in sustaining the oscillations and therefore in this particular design we need a three terminal piezo rather than a two terminal one.

The oscillations produced at the collector of the transistor is dumped into the coil, saturating the coil with magnetic inductions.



The coil kicks back the stored energy during the oscillations, magnifying the generated AC across it.

This stepped up AC is applied across the anode and the cathode of the piezo element, which starts vibrating sharply according the pitch of the frequency, generating a shrill, ear piercing sound in the air.

However to make the sound audible at maximum intensity, the piezo transducer needs to be glued or installed in a special way inside its housing.

Frequency of Oscillator

Although it may be difficult to derive the exact formula for this circuit, the design resembles a Crystal oscillator where the piezo acts like a ceramic crystal

Frequency = 1 / 1 / 2π√LSCS

Where Ls and Cs are the internal inductance and capacitance of the piezo respectively.

Video Clip

How to Stick Piezo

how to stick piezo transducer on a rubber ring and housing for maximum sound

Video Clip showing the various procedures required for sticking a piezo transducer correctly:

For this particular application the piezo element needs to be stuck at the base of its housing which must consist of a hole having a diameter of about 7 mm.

The piezo element cannot be stuck directly over the base of the housing, rather it must stuck and positioned over a soft, pure rubber ring, having diameter 30 % less than that of the piezo transducer. Only if the above fixing procedure is followed, the buzzer will sound, otherwise the sound may get choked and fail to reproduce.

Parts List
R1 = 100K,
R2 = 4k7,
T1 = BC547,
L1 = Buzzer inductor,

2 pin buzzer coil


PZ1 = Piezo element, 27mm, three terminal
Rubber ring = 22mm

SHARING IS CARING!

About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!






28 thoughts on “Make this Simple Buzzer Circuit with Transistor and Piezo”

  1. Hi All,

    Perhaps it not the right post to ask my question but if you can help me it would be great. I am trying to generate small voltage (~5mV) from sound of high frequency (~20 Khz). Also I need a cheap option to make it (~ INR 5) as I would require to mass produce the circuit. I was thinking of using a piezoelectric in place electromagnetic inducers for the same. Do you think it is possible

  2. Hi sir ,i have a piezo (black) which gives beep when applied to 3v…i want to make sparrow sound through it using 220v capacitive power supply

    • Hi Nikhil, It's a TINGGGGG sound…sorry I don't have it… it needs to be programmed or designed and tested with a lot of trial and error

  6. resonant frequency:500khz,Electrical-mechanical Coupling coefficient:0.75±8%,Mechanical Quality Factor:60±15%, these are the specifications of my piezodisc

  7. i am suppose to measure bone density using piezo disc P-52,i want to make piezo to work as an actuator at one end(exciting it usinf electric field so that it produces at stress at one side) which is attachted to a bone.the waves will travel through the bone and are picked up by other piezo patch at other end.and correspondingly define conductance and thus bone density

    • you mean to say the bone density will causing variations in the frequency level from one to the other end? I don't think do this concept will help to measure bone?

      I can design but that won't help the purpose…

      • sorry a lot of typos in the above comment, here's the corrected version:

        "you mean to say the bone density will cause variations in the frequency level from one end to the other end of the bone? I don't think this concept will help to measure bone density?

        I can design it but that won't help the purpose…"

  8. HI.I AM WORKING ON PROJECT FOR BONE DENSITY MEASUREMENT USING PIEZO.I HAVE PIEZOELECTRIC DISC(500KHZ),PZT-52.CAN YO HELP ME IN DESIGNING THE ACTUATOR AND SENSOR PART

    • I don't know about the latest rates, you can inquire it in Lamington Road (Mumbai).

      …by the way manufacturing the above explained buzzer won't be easy because plenty of small and big companies are already manufacturing these at extremely competitive rates……

  11. Hello, i wiuld like to buy a certain quantity of those pzt elements for a project i'm having.
    The only problem is, i need to know much power output one piece can provide per pulse, and i don't know how to calculate it with the data dosplayed on the datasheets… can someone help me?

    • The datasheet reveals that it has a resonant impedance of 300 ohms approximately, so you can use is this with reference to the supply voltage and use Ohms law for calculating the current intake
      Once you find the current you can multiply it back with the supply voltage.

  12. Thank you Chinmoy for your curiosity,

    However I would repeat the same thing again…"why do you need it? it's not necessary for such a simple design"

    I am afraid just like your other previous comments you once again failed to understand the core of the advise 🙂

    I meant to say that we measure voltage and current parameters only for those circuits for which these matter, so that it helps the user to tweak and optimize the results from the circuit, and here it wasn't relevant at all since the circuit is heavily dependant on readymade components such as the piezo, transistor and the inductor, so it wasn't so important, it's just about using good quality components and witness perfect results.

    And as far as a new learner is concerned it becomes even more meaningless and irrelevant for him to know these parameters, because a new learner must first learn the basics regarding transistors, piezos, inductors etc, and then learn how these need to be configured for achieving the intended results, there's no point in jumping to an oscillator and start measuring the voltages and current, what would the new learner understand from these data?

    And by the way, piezos vary a lot for different makes and brands, and so does the hfe of the transistors and so does the mH of the inductors, which are procured readymade….so IMO these can definitely cause variations in the discussed parameters and there’s no way to change these until the components were itself changed,…and again it's not important to change these variations because it wouldn't yield anything substantial in terms of the sound intensity.

    Sound intensity for the above design is hugely dependent on how it's stuck on the base, the quality of the rubber ring and the size of the hole of the front lid.

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