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You are here: Home / Mini Projects / Make this Simple Buzzer Circuit with Transistor and Piezo

Make this Simple Buzzer Circuit with Transistor and Piezo

Last Updated on September 20, 2019 by Swagatam 47 Comments

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.

A buzzer is a high frequency oscillator circuit used for generating a buzzing sound through a transducer or speaker output.

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

Circuit Description

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



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Next: 5 Simple Water Level Controller Circuits

About Swagatam

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!

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  1. Search Related Posts for Commenting

  2. Anders Lid says

    Hi, I have a simple piezo transducer with only 2 leads . How can I substitute as a 3 lead?

    Reply
    • Swagatam says

      Hi, you can try this circuit:

      https://www.homemade-circuits.com/wp-content/uploads/2019/11/metronome.jpg

      replace the speaker with your piezo, and also add a suitable inductor across the piezo wires

      Reply
  3. Henrique says

    Hi Swagatam,
    I understood, it will arouse curiosity among all kids making them willing to learn. 🙂
    Thank you so much, I have to travel to work, but after returning I will show what we have done as we recycling parts instead buying, and this makes a bit more difficult but will work, I hope.
    Thank you again

    Reply
    • Swagatam says

      No problem Henrique! wish you all the best!

      Reply
  4. Henrique Ferraz says

    Hi Swagatam,
    thank you for sharing your ideas and inventions for us, like me, that is just a hobbyist interested only in understanding new things.

    Please, could you explain to us… Is this circuit the same used to prank with small shocks when touched by removing the piezo part?

    Tnx a million!

    Reply
    • Swagatam says

      You are welcome Henrique, The coil can be used for generating high voltages enough to jolt anybody with a tiny shock, but the above circuit cannot be used for that purpose without the piezo transducer. Because without the piezo the circuit will not oscillate. If you use any other form of oscillator with this inductor then probably it can be used for the mentioned application

      Reply
      • Henrique says

        Thank you so much again for your very kind and quick reply 🙂

        I am learning w/ you because I am teaching few kids helping them to forget TV, video games learning something useful… but I know nothing!
        I am just transferring/translating what you teach.
        Is it possible to create a wireless control that could send signals to the buzzer making it to beep like telegraph helping kids learn Morse code with fun?
        If so, would you mind teaching us how to do it?
        Thank you so much again !!!

        Reply
        • Swagatam says

          No problem, I am glad to help!
          To make a wireless morse code circuit, there are 3 things you will have to learn to build. 1) the code oscillator circuit, 2) the Transmitter circuit, 3) the receiver circuit, which can be a small FM radio.

          You can start with the oscillator circuit first, as given below, if you succeed then we can move to the transmitter circuit:

          https://www.homemade-circuits.com/wp-content/uploads/2020/11/morse-code.jpg

          The crystal earphone can be replaced with any normal head phone

          Reply
          • Henrique says

            Thank you Swagatan,
            We will do Telegraph next weekend, the kids are getting mad…
            all of them asked to make the shock first.
            But I am learning to teach… and I didn`t understand well..
            What should we connect after Piezo part to create shock w/ small batteries AAA or Lr44 ones? I am scared to use 9Volts batteries.
            Thank you again

            Reply
            • Swagatam says

              No problem Henrique.
              After making the buzzer circuit successfully, try touching the two ends of the coil, you should find some shock like vibration.

              The mosquito bat circuit is one good source of converting 3V to 1000 V shock

  5. abhi says

    Design a variable frequency oscillator using Electric Bridge network to employed as actuating signal for a buzzer circuit indicating over-current in the system. Assume suitable frequency range for buzzer and electrical load. Justify the selection of the components.

    Reply
  6. Alex says

    Hello Sir,
    What should I have for the value of R1, R2, L1 if I have access a dc voltage of 5.5VDC? Thanks!

    Reply
    • Swagatam says

      Hello Alex, you can use the same set up for 5V operation also…

      Reply
    • Alex says

      Hello Sir,
      I have a current limit of max 1 mA. Wondering if you have any suggestions? Is it possible to decrease the period of the tone with a simple modification on your Simple Buzzer circuit? Thanks!

      Reply
      • Swagatam says

        Alex, the above circuit cannot be customized for frequency, you can try the following instead:

        https://www.homemade-circuits.com/simplest-piezo-driver-circuit-explained/

        Reply
  7. Jatin says

    I want to design buzzer but i have to create time delay for ON/OFF of 2 sec using passive component and using one DC supply of 12V DC no addition switching supply can not be used.

    Reply
    • Swagatam says

      You can connect the above buzer across the output of the following circit:

      https://www.homemade-circuits.com/wp-content/uploads/2019/10/variable-astable-oscillator-using-IC-555.jpg

      Make sure to increase the C1 value to 1uF

      Reply
  8. Norman D Kelley says

    HI Swagatam!
    Just curious… can the BJT be replaced with an AO3400? What effect will it have on the circuit? I was hacking a 3-24V piezo and I think I blew the L6 transistor. The L6 is a 200-400 hfe SMD NPN transistor. I don’t have anything like that, but I do have the AO3400. Its really not a big deal as I have plenty more of the same piezo buzzers. I was just curious. Thanks!

    Reply
    • Swagatam says

      Hi Norman, yes it might work, if the supply is above 6V

      Reply
  9. Rwiju Pal says

    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

    Reply
    • Swagatam says

      Hi, a piezo can be tried, but only if the sound pressure (volume) is reasonably good.

      Reply
    • Rwiju Pal says

      Can you help with the circuit. I cant seem to generate a sustainable voltage.

      Reply
    • Swagatam says

      please specify the volume level of the source, and at how much distance the sensor would be allowed to be positioned….

      Reply
  10. Unknown says

    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

    Reply
    • Swagatam says

      sorry, I am not sure about this circuit idea

      Reply
  11. Nikhil Sonar says

    hi sir,
    good afternoon

    please watch video (https://www.youtube.com/watch?v=FgcB7Lkvp44)

    i want to generate same sound effect using electronic circuit ,
    do you have any idea,
    i have single pulse by which i want to generate the same sound effect.

    Thanks
    Nikhil

    Reply
    • Swagatam says

      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

      Reply
  12. Unknown says

    How can I change the buzzer inductor. By mistake my younger brother used it with main current electricity.

    Reply
  13. Rashmi Dandge says

    WE CAN DETERMINE CONDUCTANCE WITH RESPECT TO FREQUENCY AND HEREBY DETERMINE THE DENSITY

    Reply
  14. Rashmi Dandge says

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

    Reply
  15. Rashmi Dandge says

    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

    Reply
    • Swagatam says

      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…

      Reply
      • Swagatam says

        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…"

        Reply
  16. Rashmi Dandge says

    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

    Reply
    • Swagatam says

      Hi, if you can provide more details regarding the concept then may be I can try.

      Reply
  17. harish says

    Inductor coil & 27mm nickel buzzer plate How much cost in bulk for each peace

    Reply
    • Swagatam says

      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……

      Reply
  18. harish says

    "L1 = Buzzer inductor" in india where it i can get them in bulk please give the contact.

    Reply
    • Swagatam says

      you can get it from Lamington Road, Mumbai

      Reply
    • harish says

      Please tell 12v piezo continues buzzer inductor coil full specifications

      Reply
    • harish says

      Sir please give me your contact number I want talk to u for i am stating new business to manufacture piezo buzzer.i want need your help sir.

      Reply
    • Swagatam says

      sorry, I don't provide telephonic assistance, if you have any questions you can put them here.

      the inductance value is around 40mH (milliHenry)

      image can be seen here:

      2.bp.blogspot.com/-8dkdn6B6OUc/VVBH_3imhcI/AAAAAAAAKLQ/3fKYTil2Fi4/s1600/buzzer%2Bcoil.png

      Reply
  19. Yan Dogadko says

    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?

    Reply
    • Swagatam says

      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.

      Reply
  20. Swagatam says

    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.

    Reply
  21. Swagatam says

    the inductor value is 40mH wound over a ferrite drum

    Reply
  22. Swagatam says

    why do you need it? it's not necessary for such a simple design

    Reply


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