# Piezo Circuits: A Detailed Overview About It

Published on October 13, 2021 , Last modified on July 12, 2024
by Hommer Zhao

Every day, we come across different situations that require us to measure unknown physical quantities. Like, temperature levels or pressure levels. And, to measure these unknown quantities, you’ll need a device with such capabilities. Thankfully, we have the answer. All you need is a piezo circuit. There are different types of piezo circuits for various applications, like the piezoelectric buzzer or piezo sensor. However, the focus of this article is on piezoelectric transducers. So, in this article, we will show you everything you need to know about piezo circuits and the different types of piezo circuits. Additionally, if you want […]

Every day, we come across different situations that require us to measure unknown physical quantities. Like, temperature levels or pressure levels. And, to measure these unknown quantities, you’ll need a device with such capabilities. Thankfully, we have the answer. All you need is a piezo circuit. There are different types of piezo circuits for various applications, like the piezoelectric buzzer or piezo sensor. However, the focus of this article is on piezoelectric transducers. So, in this article, we will show you everything you need to know about piezo circuits and the different types of piezo circuits. Additionally, if you want to learn more about piezoelectric transducers for your conversion project, this article is also for you.

## What is Piezo Circuits

Digital circuit

First, let’s look at what piezoelectricity means. Simply put, piezoelectricity is electricity produced from mechanical pressure, creating what we know as the piezoelectric effect

Now, a piezo circuit uses this piezoelectric effect to convert energy created by changes in force, acceleration, temperature, pressure, or strain into an electrical charge.

The term transducer encompasses everything that can change one form of energy to another. Thus, the piezoelectric transducer is one of the types of transducers.

But that’s not all.

The piezoelectric transducer’s sensitivity is high. So, it can serve as a sensor and work in an accelerometer because of its good response frequency.

## How does a Piezoelectric Transducer work?

Ultrasound transducers icons

As mentioned earlier, the piezoelectric transducer works on the piezoelectric principle. Also, the piezoelectric material, in this case, quartz, has a thin layer of conductive material (silver) covering its body.

Quartz Crystal

Additionally, quartz crystals are combinations of silicon and oxygen placed in an orderly crystalline system (Si02).

What’s more, piezoelectric crystals are electrically neutral and unbiased (not uniform and symmetric).

Though the atoms present with these crystals are not in order, it has moderate electrical loads. In other words, the positive charges counteract the negative charges.

Plus, the quartz crystal has one unique function. It produces an electrical polarity whenever you apply pressure or mechanical force to it on a surface.

## Piezoelectric Transducer Types

There are various types of piezoelectric transducers. Plus, you can classify these types of piezo transducers according to the piezoelectric crystal material.

### Ceramic Piezoelectric Transducers

Well, you can create the ceramic piezoelectric transducer in different shapes and sizes. For this reason, you can always meet your or your customer’s specific requirements. The major component of the ceramic piezoelectric transducer is mostly created compositions of lead zirconate titanate.

### Rochelle-salt Piezoelectric Transducers

Rochelle salt is another material that can work in piezo transistors. Out of all the different piezoelectric materials, the Rochelle salt is the material with the highest output.

Some of the downsides include not being able to use this material in humid environments. Also, you can use this material above a particular temperature (240 degrees Celsius).

However, synthetic crystals are more effective for voltage peak output applications, especially for sensitivity, than natural crystals.

### Piezoelectric Transducers based on Operation

You can divide a piezo transducer into mega-sonic, sonic, and ultrasonic transducers, depending on the working frequency. Each of these classifications has different designs and functions. First, you can use the sonic transducer at any audible frequency level, which should be lower than 2 kHz.

Good examples of the sonic transducer are buzzer transducers. Second, the normal operating frequency of the ultrasonic transducer is between 20 to 200 kHz. Lastly, mega-sonic transducers work at the MHz frequency level.

Ultrasonic Transducers

## Piezo Circuits Examples

Here are few examples of other piezo circuits and how they work:

### 3V Powered Loud Beeper

It’s difficult to get a loud sound intensity from a piezoelectric type beeper with a 3V DC supply.

However, this circuit bypasses such limitations and efficiently produces an intense sound. It does this by combining a voltage boost sector with a resonant feedback network.

So, the voltage the piezoelectric wafer receives is approximately 40 volts peak-to-peak. The final result is a circuit that creates a loud sound without consuming a lot of currents.

### Motion Alarm using Piezo Device

Here is another piezo circuit that’s affordable and easy to build. The result of this circuit is a piezoelectric device that you can use as a motion-sensing device for any motion alarm.

### Click Sound Generator Piezo Circuit

The click sound generator circuit creates an audible “click” or feedback whenever you push a button—on a computer system. Both circuits above have the capabilities to generate these click sounds every time their logic input switches from low to high.

The piezo-type sound generator has low power consumption and it provides a sensor level of indication. Also, you can control the number of clicks you get per second.

### Piezoelectric Tap Switch

Here’s another piezo circuit that utilizes a piezoelectric wafer. Also, you can secure this wafer inside a plastic box so it acts as a finger tap sensor. Hence, whenever you tap the box containing the wafer, it’ll turn on/off the power (AC or DC) of an external device.

Additionally, a 9v battery powers this circuit and drives a single 10 Amp contact rating single-coil relay (5V). With this relay, you switch between AC or DC power. Also, when you place the circuit on standby mode, it draws a minimal 1ua current.

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## Piezoelectric Transducer: The Different Types of Operating Modes

The piezoelectric transducer has three main operating modes, depending on how you slice the piezoelectric material. They include transverse, longitudinal, and shear operating modes.

For the transverse mode; you can apply pressure to the main axis ‘Y’ and generate a load. Then, move towards the ‘X’ direction at a 90-degree angle from the line of pressure. At this point, the charge will depend on the shape of the piezoelectric material.

For the longitudinal mode, the load the generated load depends on the force you apply. In contrast to the transverse effect, the load in the longitudinal mode does not depend on the shape or size of the piezoelectric material.

Finally, the shear mode is similar to the longitudinal effect. It generates load based on the force you apply and is also not reliant on the geometry of the piezoelectric component.

## Piezoelectric Transducers Applications

Here are some applications of the piezoelectric transducer:

Automobile Applications

• In residential products such as motion detectors or object detectors
• In normal electronic devices like toys, remote controllers, and games

Remotes

• To calculate detonations in automotive applications
• In airports or restaurants with automatic doors

## Advantages and Limitations of Piezoelectric Transducers

Here are some of the advantages and limitations of piezoelectric transducers

• They are self-generating transducers
• Perfect for a wide variety of applications
• Simple to use and handle in circuits

### Limitations

• Susceptible to environmental conditions like temperature
• Can’t measure static applications
• You can’t get the shape and strength you want for your piezoelectric materials with ease
• Occasionally low output voltage in few applications

## In Summary

Piezoelectric circuits are unique circuits that work for various applications. The piezoelectric transducer is one of these circuits that offer you unique capabilities you can hardly find in other sensor devices.

The Piezoelectric transducer has several advantages and disadvantages—but, this depends on your application. Lastly, be sure to closely evaluate the performance of a piezoelectric transducer before making a choice or purchase.

We’ve now come to the end of this article. However, if you have more questions, feel free to contact us. We’d love to hear from you.

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Hommer Zhao
Hi, I'm Hommer Zhao, the founder and Chief Editor at WellPCB. With extensive experience in the PCB industry, I oversee all content to ensure it meets the highest standards of accuracy and insight. We proudly serve over 4,000 customers globally. For inquiries or more information, don't hesitate to reach out. Your satisfaction is my top priority!