In the previous post we discussed a piezo transducer element and learned how to use it with electronic circuits. In this article we will see how a piezo tranducer can be driven or operated using a simple circuit.
As discussed earlier a piezo transducer basically requires a frequency to vibrate and reproduce the required sound.
This property makes these devices typically suitable for buzzer related applications and in warning alarm devices.
So does this mean that if we apply a frequency across the terminals of a piezo transducer, it will start generating the intended sound outputs?
Partially this may be correct but might not be as easy as that.
How to Operate a Piezo with Maximum Sound
The applied frequency will be required to be amplified very sharply or strongly before it can actually produce the intended effects in the piezo.
However the amplification procedure is not by using conventional amplifying circuits as used in systems incorporating speakers, but rather it is simply implemented through an inexpensive inductor.
The low power frequency which may be available from a relevant circuit or an IC is first amplified using a transistor, and further more the transistor output is pumped up using an inductor. The use of a inductor becomes the most crucial stage for driving a piezo electric transducer.
The used inductor might not be critical with its value, but the value should as high as possible, the higher the sharper the reproduction from the piezo.
A simple piezo transducer driver circuit or a simple piezo alarm circuit is shown in the following circuit using a NAND gate.
Please note: The junction of the 0.01uF capacitor and the 33 K resistor needs to be connected to ground, which is mistakenly not indicated in the diagram. So please make sure to do this otherwise the circuit will not work.
Piezo Driver with Intermittent Beep Sounds
This piezo intermittent beep sound generator, driver circuit can be utilized as a building block in a wide range of projects. The best example can be its application as a tone-burst oscillator to operate a piezo transducer directly, and using a transistor to sound an alarm.
It may be also possible to use the above circuit modulate an FM transmitter so that it creates an intermittent beeping sound on reception. The circuit is made up of a single quad NAND gate, a couple of resistors, and a pair of capacitors.
The first 2 gates are configured as the "burst" oscillator while the third and fourth gates function like a "tone" oscillator. The burst oscillator is a lot slower compared to tone oscillator and is accustomed to pulse the tone oscillator with an intermittent on and off.
Using IC 555
A very simple yet effective piezo driver circuit could be build using a single IC 555 as shown below:
You can try adjusting the values of C1 and R1 for experimenting with the tone output of the piezo driver.
To get maximum sound output make sure to mount the piezo transducer inside a plastic enclosure with an elevated step and a 5 mm hole at the center.
Or you can simply buy a ready-made unit with the piezo fitted inside a plastic enclosure, as shown below:
With the above assembly you may find the sound output to be quite impressive. However, if you want the sound to be extremely high and ear piercing, you may consider using a buzzer coil as indicated below:
These can be easily procured ready-made from any electronic spare part retailer.
To connect this, simply attach the coil leads across the piezo buzzer wires, or parallel to the piezo buzzer wires. Once done, you may find the piezo driver sound output increasing drastically to an extremely high level.