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 using NAND Gates
This 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 it to modulate an FM transmitter so that it creates a 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 on and off.
the inductor symbol used in the piezo transducer driver suggests a ferrite core choke. Can a simple wire wound inductor be used instead?
No, the inductor has to be a ferrite wound inductor, air core will not work.
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Very nice post, would you kindly explain how one can use a piezo transducer to measure liquid level from the bottom of container like how ultrasonic fuel level sensors work?
Thanks, Glad you liked it. for ultrasonic application, one piezo can be used for transmitting high frequency towards the target (liquid level), another piezo adjacent could be used for capturing the reflected vibrations, and then processing the distance.
Hi Swagatam,
I am looking to build a simple circuit which can light up a 12v LED strip using piezo. Basically trying to use a piezo attached to a drum and light up the LED attached to it. Please help me out.
Hi Rajtilak, It can be difficult to light up a 12V LED strip, since a typical piezo (27 mm) will not generate more than 3V at its optimal capacity.
even a boost charger circuit will not be able to help since the current involved with a piezo output could be relatively low
Hi,
I am not looking to power up the strip with the current generated from the piezo sorry if i had confused you. All i need is using this piezo as a trigger source and get supply from a 12V source. Im still not clear about what i am trying to tell you. I will have a separate 12V DC source, all i need is, when i hit this trigger(piezo) i want the signal to make this strip power up from that 12V source. Please help.
Hi, Swagatam hoping you are well.
Can a 555 timer be used to drive a driverless piezo and please provide a value for the inductors.
I would like to use it in the moisture detector.
I do have a small toy 8 ohm speaker would that be better, but I think it would require a sound generating circuit.
Unfortunately due the virus i cannot purchase directly, only online but the shipping costs are astronomical.
Eg. For 10 cents I’d be paying 100 cents shipping. Thanks so much and be safe.
Hi Moboy, yes it is possible to drive a piezo element directly through a IC 555 astable, by connecting the piezo wires across pin3 and ground, but you will also require a small 100uF inductor parallel with the piezo wires for proper amplification, an the frequency will also need to be adjusted to suit maximum volume.
Thank you Swatagam, I truly appreciate your prompt reply and advise.
I wish you all the best.
No problem, moboy!
Hello,
I need a circuit to produce ultrasonic vibrations. The vibrating element (piezo) has to attach the wall of a let's say glass and the vibrations should detach the bubbles attached to the glass wall at a frequency of about 80 kHz. Do you think this configuration will be helpful?
Hello, yes the last design can be used for the purpose but the piezo will need to be attached correctly so that the vibration do not get dampened
What value should be the coil for a 35Khz oscillator?
you will have to determine the frequency by trial and error method by varying the 33K resistor or the capacitor values and confirming the results with a freq meter
Can third high volume circuit be driven by microcontroller pin generating clock?
yes you can, feed the clock directly to the base of the transistor via a 1k resistor