Dec 15, 2011

Simple Buzzer Circuit - Piezo Electric Buzzer Explained

In this article we learn how to make a very simple buzzer using using piezo electric transducer and hardly any electronic components.
Just a single transistor, a coil, a piezo buzzer are enough to make it “buzz” or rather “twit” for you, with an output that may be quite ear piercing.

Circuit Description:

The simple 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


Referring to the above simple piezo buzzer circuit 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 stuck or installed in a special way inside its housing.

how to stick piezo


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 for the proposed simple piezo buzzer circuit

R1 = 100K,
R2 = 4k7,
T1 = BC547,
L1 = Buzzer inductor,
PZ1 = Piezo element, 27mm, three terminal
Rubber ring = 22mm

33 comments:

  1. Cool project!
    Where and or how do I get or make the;
    "L1 = Buzzer inductor"?

    ReplyDelete
    Replies
    1. In India you can get them in bulk, I have hundreds of them lying with me, I wish I could give it to you. Not sure from where you can get it in your country.

      Delete
    2. HELLO Anonymous, did you find where to get the buzzer inductors? I would like to know where you got them.

      Delete
  2. Is it available readymade in the nearby local electronic equipment stores?????

    ReplyDelete
  3. Would you be more specific in describing the Buzzer Inductor? What is the value of the inductance? open aired or ferrite cored? a picture is worth a thousand words.Thanks.

    ReplyDelete
    Replies
    1. Please check the image here:

      http://1.bp.blogspot.com/-j-B5fWFwJVo/UQTewNIMC7I/AAAAAAAACzA/Y7WLCNIbUGs/s1600/buzzer%20coil.jpg

      Delete
    2. L value depends on the resonance frequency you would like to generate and the supply voltage. I have used 3V and generating 35V across the coil at 3kHz. I have used a ferrite 10mH inductor. Hope that helps.

      Delete
  4. hi,
    can u provide me the data sheet for the above circuit.?
    tat means, current and voltage levels for each component, etc..

    ReplyDelete
    Replies
    1. why do you need it? it's not necessary for such a simple design

      Delete
    2. i need datasheet because i am planning to use this part in my project.So i need tat.pls help me.
      Thanks.

      Delete
    3. Hi Anonymous,
      Though this post is quite old, I saw it today and feel like commenting on it. If you have already solved your problem, then simply skip it.

      First, it would be much better if you create a user name rather than post as "Anonymous".

      Second, I think Swagatam Majumdar has not actually built this circuit, so he may not be able to answer your specific questions regarding the actual current and voltage levels for the components during operation ;-)

      So the best alternative is to build the circuit yourself and measure the voltages and currents at various points. I am sure you are capable of doing that much yourself; why do you want to be spoon fed?

      Regarding the inductor, check above for the post of Kramadhati for clear detailsof of the same. Good luck.

      Delete
    4. For your kind information Mr. Chinmoy, I have built and sold many, many 1000 pieces of this unit, so I think I know about this circuit quite well.

      This is an oscillator design and therefore might not have fixed values at the different points which might vary depending on the specs of the particular piezo, inductor, and also the supply levels, that's the reason why i could not specify the details to Mr. Anonymous

      Delete
    5. the inductor value is 40mH wound over a ferrite drum

      Delete
    6. Hi Swagatam,
      I missed your reply to my post dated July 11, so I'm answering today. Regarding the DC voltages at various points of the circuit, IMHO they should not vary substantially while using different piezos since the operating point of the transistor is largely decided by the biasing circuit on the base. There are only two places where you can measure the DC voltages in this circuit, the collector and the base, since the other points are either ground or +12V VCC, so I feel you could have posted some average representative values for the two voltages as an answer to the query (since you have made many 1000 pieces of this unit).

      I appreciate your work very much, but what surprised me was your response "why do you need it? it's not necessary for such a simple design"! Actually, for a learner in electronics, the voltages at various points in even a single transistor common emitter stage may be vital for understanding the operation of the circuit and inclusion in a college project etc. Though I am sure you appreciate the fact that I advised Anonymous to measure the values himself since it is a simple task!

      Best regards

      Delete
    7. 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.

      Delete
  5. 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?

    ReplyDelete
    Replies
    1. 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.

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

    ReplyDelete
    Replies
    1. you can get it from Lamington Road, Mumbai

      Delete
    2. Please tell 12v piezo continues buzzer inductor coil full specifications

      Delete
    3. 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.

      Delete
    4. 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:

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

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

    ReplyDelete
    Replies
    1. 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......

      Delete
  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

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

      Delete
  9. 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

    ReplyDelete
    Replies
    1. 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...

      Delete
    2. 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..."

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

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

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

    ReplyDelete

Readers are requested not to include external links while commenting. For consulting a diagram, upload it on Google Drive and provide the link here.