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.
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
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,
- PZ1 = Piezo element, 27mm, three terminal
- Rubber ring = 22mm
Simple Buzzer using 8 Ohm Speaker
The circuit illustrated below generates sounds similar to a genuine buzzer. It simply works with two integrated circuits and very few parts.
When S1 is temporarily pushed, C1 begins to charge via resistors R1 and R2. Pin 2 of the 555 oscillator/timer, IC1, is finally triggered. By driving pin#7 low, the IC begins to drain the capacitor via R2. This cycle will continue as long as S1 remains pushed.
The output of IC1 (pin 3) alternates in rhythm with the capacitor's charging and discharging, generating a sound frequency for IC2. IC2 is an LM386 low voltage audio power amplifier which amplifies the audio frequency's volume.
The speaker is employed to replicate IC1's tone frequency, that feels like a genuine buzzer sound. To get a low-frequency buzzing, you may want to increase the value of C1 to 0.1 uF.
For added stability, you can connect pin 7 of IC2 to ground through a 47 uF capacitor.
Looking for a circuit schematic using hi frequency tweeters or piezo speakers for and LRAD application used against neighbors barking dogs??
You can easily build it using an 555 IC astable circuit.
A related concept is posted in the following article, you can checkout the last circuit from this article:
How to Make Dog Barking Preventer Circuit using High Frequency Deterance
Hi, I am looking for 1500 kHz frequency circuit’s for my son collage project, for metal Detector working on 12 Volts battery. As he have had gone throw bike Accident. 4 months total on bed as multiple fractures. We both are choked. Can u please help
You can easily make the oscillator using a 555 IC as explained below:
https://www.homemade-circuits.com/ic-555-astable-multivibrator-circuits/
Can you please help me with a driver circuit for a two terminal piezo buzzer.
Sure, you can try the following circuit using IC 555:
If you want to increase the volume drastically just add a buzzer coil parallel to the piezo wires.
Hi swagatam
I am using this buzzer in 24v system .this buzzer starts operate from low voltages ex:3V , how to block voltage below 22V , it should operate only above 22v to 28V.
Hi Mehboob, you can add a 22 V zener diode in series with the buzzer positive wire.
HI Swagatam , Thanks for the circuit . If I want it 0.5 secs on and 0.5 secs off(intermittent) what circuit I will have to use ?
Hi Nikhil, unfortunately you can’t change anything in the above diagram for getting intermittent sound. You may have to use another oscillator for this.
Hello Sir,
I would like to know the resistance value of the inductor of 40 milli Henry you have showed in your circuit is it below115 ohms or above that.As you said the resistance increases with the Henry value such that I will be able to select a suitable Henry value for my circuit. With 115 ohms a iam getting a very good sound and the current is also less.
Regards
Regards.
Hello V. Sambath, I did not measure the inductor resistance so I am not sure about it. If 115 ohm inductor is working for you then you can continue using it without any doubts.
Hello Sir,
My problem is that I don’t know the inductance value i only know the resistance of the inductance 115 ohms , that is why i asked about the resistance of the 40 Henry coil.I tried with the suppliers they are asking to mention the Henry value .
Hello V.Sambath, you can buy a multimeter which has an inductance measuring facility, then you can easily determine the value of your inductor.
Thank you Sir.
Regards.
Hi, Sir
Thank you very much for your fast response.
Sir I have designed afire alarm hooter which can be used along with the present digital, programmable fire alarm panel working on 24v DC. The circuit is 100% OK and draws around 52 ma at 24v actually during a fire the hooter voltage goes down to 19 to 20v in that condition the current again will go below 40 ma, tone is also easily variable as per our requirement I got the ferrite coil from my junk box i don’t know the value of it ,the voltage from the + of the coil to Gnd is 20.5v the buzzer is driven by a transistor so the voltage across the buzzer is 5.8v it is a 27 mm 12v buzzer so I hope 40 mill Henry may match for my circuit transistor is driven by a 555 ic. 100 milli Henry or 40 milli Henry which will have more resistance .my coil shows 115 ohms.the coil is 32 SWG.
Regards ,V.Sambath Kumar.
Thank you V. Sambath, for the detailed explanation.
As the inductance value increases the resistance also increases, therefore the 100mH will have higher resistance than the 40mH coil.
Sir,
Thank you so much for your valuable information. If you add a provision for uploading the circuits from our end it will be more usefull .
Regards .
You are welcome V.Sambath, I agree with you however we do not have an easy facility for image uploads, therefore presently this may not be possible, hopefully in future we may see this facility implemented in all WordPress blogs.
Sir,
What will the ohmic value of the coil that you have mentioned in the circuit. Is it necessary to use only ferrite core type coil if the inductance 40 milli Henry match will it work. One looks like a resistor can I use this if the Henry value is same, will a 100 milli Henry resistor type work here these are easily available in the market.
Regards. V.Sambath kumar
Hello Sambath, the recommended inductor is shown in the figure, for maximum sound output. If you are using an air core coil then an equivalent coil wold be much bigger in size, but it will work. I am not sure about the exact mH value of the coil
Sir,
Can I use a resistor type inductor of 40 milli henery. It is a tubular type Air Core type.
Regards V.Sambath kumar
Sir, first of all thanks a lot for sharing the circuit details of almost all simple to somewhat complex circuit concepts in details here. I hv a question which is not related to this post of urs but definitely related to mini buzzer. I have a circuit wherein when a transistor turns on it activates a DC pump and also a audio indication using a buzzer. But the sound of the buzz is not so pleasing when the pump is connected. Otherwise(without pump) it gvs nice sound. Is there any way to rectify this sound issue when inductive loads are connected .Thanking you so much
Thank you Binoj, the disturbance in the buzzer sound could be due to the motor reverse spikes. You can try connecting a high value capacitor between 100uF and 1000uF right across the buzzer terminals and check if that helps or not
Hi. I have just discovered your site; it is very interesting and useful to complete electronic newbies like me. I have made the basic buzzer circuit (https://www.homemade-circuits.com/how-to-make-simple-piezo-buzzer-circuit/) and fiddled with it, trying to change the pitch of the output. Nothing changes it. I have thought about this and wonder if it is because the feedback part of the piezo ‘speaker’ fixes the output frequency. Is that the case or is there something else going on? Do you have any circuits on the site that I haven’t found that show how the pitch of a piezo ‘speaker’ can be changed?
Hi, thanks for liking this site! you cannot adjust the tone frequency of the sound in this circuit. yes it is due to the feedback element determining the frequency
you can try the following concept instead for a variable feature:
Simplest Piezo Driver Circuit Explained
Thank you; I will certainly try that (with a 2-terminal transducer…)
Hi, I have a simple piezo transducer with only 2 leads . How can I substitute as a 3 lead?
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