On the other hand, piezo discs can also perform as a piezo sensor in a microphone to capture sound waves. Piezo disc buzzers can be found in many household and commercial alarms and equipment to produce various sounds depending on the frequency of the applied voltage input. The ability of piezoelectric discs to perform as both piezoelectric actuators and piezoelectric sensors makes them an extremely useful material in sound generation and detection. Piezo disc sensors are very sensitive, making them useful in microphone applications. Depending on the circuit attached, the digital signal can be amplified or recorded. The deformation of the piezo disc creates a readable voltage proportional to the sound wave input. Piezoelectric discs in microphones and contact microphones that attach directly to musical instruments oscillate as sound waves are received. The pressure from the sound waves produces an electrical voltage output which can then be amplified or recorded. A piezoelectric ceramic sensor inside a microphone detects and captures sound waves. Now let’s look at the other effect of piezo discs in sound detection and amplification.
Piezo disc sensors in microphones detect sound waves. Piezoelectric disc buzzers are extremely useful elements for generating sound. The vibration creates sounds of all tones, pitches, and volumes found in clock alarms, smoke alarms, doorbells, telephones and much more. When an AC voltage is applied to the two electrical contacts on the face of the piezo disc, the piezoceramic vibrates at the applied frequency to produce the desired sound.
Piezo disc actuators bend back and forth very rapidly when an electrical signal is applied, oscillating and vibrating. Let’s first explore piezo disc buzzers as piezo actuators in sound production. The beauty of piezoceramics is they can perform as a piezoelectric actuator and produce sound, or as a piezoelectric ceramic sensor and detect sound. We will explore the detailed mechanics of piezo buzzers and piezo discs in sound production and detection below. Piezoelectric discs capture sound waves and convert them into an electrical signal, such as in contact microphones. A piezo disc alone has the opposite effect of a piezo buzzer. Piezoceramics that produce sound are usually known as piezo buzzers, which consist of a piezoelectric disc attached to a housing driving circuit. The sound generated will have different pitches and sounds at different frequencies. Depending on the frequency of the voltage, the oscillation of the piezoceramic produces an audible sound. When a voltage is applied to a piezo disc, the piezo disc oscillates. Piezoelectric discs are most used in this application. The piezo element looks (electrically) like a capacitor (in this case, a 20nF capacitor) so the drive waveform from a PIC will be a bit trapezoidal (sloped rise and fall), but if you squint should look pretty much like a square wave.Piezoelectric ceramics have long been used in microphones and sound production as a compact, yet effective means of capturing and producing sound. Here is an example of the latter type of circuit: If you use a microcontroller, you can drive the 'sounder' with two port pins push-pull, and so get almost 10Vpp drive from a 5V supply. You could create a 2500Hz square wave oscillator with a 555, or use a PIC or other microcontroller. You will get the maximum sound level by driving it with a sine wave at that frequency and the maximum rated voltage, but a square wave will work too, since more than 80% of the energy of a square wave is at the fundamental frequency (but won't sound as pure because there is still some response from the transducer ('sounder') at, say 7500Hz. That element is acoustically coupled to a Helmholtz resonant cavity.ĭue to the "tuning" of the element and resonant cavity, the response of the "sounder" is not at all flat- it's really designed to emit the maximum sound level at a single frequency, in this case 2500Hz. It's actually a thin round piezoelectric "bender" element bonded to a metal backing that distorts in an "oilcan" mode when voltage is applied (image from here). This thing is not a "buzzer" it's a "sounder" in Chinglish or what I'd call a transducer.
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