This project makes sound in a whole new way.
It is quite easy to build and only uses a few parts:
A transistor like a tiny switch
A special coil like a mini electromagnet
A tiny speaker component piezo transducer that turns electricity into vibrations
The result is a high pitched sound kind of like a whistle.
This circuit is special because it uses the coil to make the sound which keep going unlike most circuits that use resistors and capacitors.
What is a Piezo Buzzer Circuit:
A basic electronic circuit that generates sound using a piezoelectric buzzer is called a piezo buzzer circuit.
In electrical equipment piezo buzzers are often used to produce auditory alerts, notifications or alarms.
The essential part of a piezo buzzer is the piezoelectric element which produces sound waves by vibrating in response to an applied voltage.
Circuit Working:
Parts List:
| Category | Item | Quantity |
|---|---|---|
| Resistors | 100k CFR | 1 |
| 4.7k CFR | 1 | |
| Semiconductors | Transistor BC547 | 1 |
| Buzzer Inductor | 1 | |
| Piezo 3 Pin | 1 |
A study of the piezo buzzer circuit diagram indicates that the transistor T1 and the inductor make up the circuits core.
Basically the middle tap of the three terminal piezo element used in this application gives essential feedback while the buzzer coil, is placed carefully to amplify the resulting oscillations.
The piezo element across the buzzer coil is activated by the transistor functioning when voltage is fed into the circuit.
The transistor and piezo are quickly turned off by this action which also grounds the transistors base through the piezo elements central tap.
When the transistors base is released it returns to its initial state starting a cycle that repeats and generates the desired oscillations or buzzing frequency.
The piezo transducers central tap is essential for maintaining the oscillations.
A three terminal piezo compared to a two terminal one is therefore necessary for this design.
In order to fill the coil with magnetic induction the oscillations generated at the transistors collector are directed into it.
After that the coil enhances the AC generated across it by releasing stored energy during oscillations.
The anode and cathode of the piezo elements receive this increased AC which causes them to vibrate sharply in response to the frequencies pitch and produce an ear piercing sound.
The piezo transducer needs to be carefully joined or fitted into the enclosure in order to enhance sound intensity.
To reach the necessary frequency a crystal oscillator like design is used in which the piezo works similarly to a ceramic crystal.
The oscillators frequency which is difficult to calculate correctly is based on a design that resembles a crystal oscillator.
For this particular use the piezo element needs to be connected to the base of its enclosure or housing which should have a hole that is around 7 mm in diameter.
Formulas:
The formulas for Simple Piezo Buzzer Circuit is mentioned below:
The resonant frequency of an electrical circuit with a connected inductor L and capacitor C is measured by this formula.
The correct frequency at which a circuit responds to an transforming current AC signal to the greatest extent is known as the resonance frequency.
Frequency = 1 / (2π√LsCs)
here,
- The resonant frequency measured in hertz Hz is represented by f.
- The formula uses the mathematical constant 2π which is pi times 2 as a factor for conversion.
- The symbol for a square root is √.
- Henrys H inductors limit variations in current and L is the circuits inductance as measured in Henrys.
- Capacitors store electrical energy and C is the circuits capacitance as measured in farads.
Calculation Steps:
Use component details or the electrical devices inductance L and capacitance C to measure these values.
Be sure that the capacitance and inductance are measured in the correct units F for Farad and H for Henry by replacing the measured values of L and C in the formula.
Calculate the products square root (L x C).
The resonance frequency of the circuit is expressed in hertz Hz is easily calculated by dividing 1 by (2π x square root of (L x C)).
Like if the circuit contains a capacitance C of 1 farad and an inductance L of 1 henry:
1 / (2π√(1 x 1)) = f
f = 0.159 Hz (after division and square root calculations)
How to Build:
Below mentioned are the steps to build a Simple Piezo Buzzer Circuit:
- Place the NPN transistor T1 on the breadboard.
- Connect the ferrite inductor to the collector of the transistor.
- Connect the three terminal piezo transducer to the base and emitter of the transistor.
- Add resistors and capacitors as per the circuit design.
- Use connecting wires to establish the necessary connections between components based on the circuit diagram.
- Connect the power supply to the correct points on the breadboard ensuring it matches the required voltage for the circuit.
Piezo Transducer Installation:
- Create a housing for the piezo transducer with a hole having a diameter of about 7mm.
- Join the three terminal piezo element at the base of the housing.
- Place a soft pure rubber ring with a diameter 30% less than that of the piezo transducer on top of the piezo.
- Carefully glue or secure the piezo transducer and the rubber ring inside the housing to ensure proper positioning.
Testing and Adjust:
- Switch ON the power supply and observe the circuits behavior.
- If the circuit is functioning correctly one can hear a buzzing sound from the piezo transducer.
- To get the desired frequency adjust the values of the resistor and capacitor as needed.
- To boost the sound intensity carefully adjust the piezo transducers position within the housing.
Note:
- One can construct a simple piezo buzzer circuit with informative feedback that generates special oscillations by following these detailed instructions.
- The circuit is modified to meet the correct frequency standards.
References:
BUZZER BASICS -TECHNOLOGIES, TONES,AND DRIVE CIRCUITS
Design Techniques to Increase a Piezo Transducer Buzzer Audio Output