![]() 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. 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). R2 can probably be a lot lower, but again, you didn't supply a datasheet so all the component values are just rough ideas or guesses at best.This thing is not a "buzzer" it's a "sounder" in Chinglish or what I'd call a transducer. R2 cause some back voltage to this current to make it die down more quickly, helping the high frequecy response. If you don't give the kickback current a place to go, then the voltage can get high enough to fry Q1. Piezo elements have a significant inductive component as viewed from the driving circuit. Figure you can count on a gain of 50, so that means 215 mA of collector current, which should be way more than required.ĭ1 is there to give the kickback current of SP1 a place to go when Q1 turns off suddenly. When the digital output is high, Q1 will have 4.3 mA of base current, which should easily give it enough current sink capability to pull the collector as low as it can go. You most likely don't need as much base drive as this. Most digital outputs can source that much without issue. Figure the B-E junction drops 700 mV, so that leaves 4.3 V accross R1, which causes 4.3 mA base current and will draw that much from the digital output. R1 limits the current thru the base of Q1 when the digital output is high. The above circuit should work well enough for most piezo speakers, although it can possibly be driven from a higher voltage, which would yield higher volume. Secondly, they are energy-efficient, requiring very little power to operate. Firstly, they are compact and lightweight, making them ideal for use in handheld devices or any application where space is at a premium. The page you linked to turned out not to be a datasheet, so we don't know anything more about the piezo speaker than what you say. Piezo buzzers have numerous advantages that make them popular choices in many electronic devices. You said you were a novice, so here is something simple: Is this correct? Is it possible to build a drive circuit for a piezo buzzer with only these components, or do I something else? The supplementary comments for this circuit diagram suggested people "consider connecting a Zener diode in parallel with the piezoelectric sound component and Rp if necessary."īased on this, my understanding is that the necessary components of this drive circuit are - the microcomputer, I am a novice with electrical engineering and I am trying to understand exactly what components are needed in this external drive piezo buzzer drive circuit. ![]() It is mainly divided into piezoelectric buzzer and electromagnetic buzzer, represented by the letter 'H' or 'HA' in the circuit. It is widely used in alarms, computers, printers and other electronic products as sound devices. ![]() Under the heading "Please give me an example of the drive circuit for a Piezoelectric Sounder or a Piezoelectric Diaphragm (External Drive Type)." they said "Examples of typical drive circuits are broadly divided into case 1 where a transistor circuit is used and case 2 where the product is driven directly from a microcomputer." and gave the following image as an example. The buzzer is a sounding device that can convert audio signals into sound signals. I was reading the FAQ page on the website of a piezo buzzer manufacturer I am interested in the use of a microcomputer in a drive circuit for an external drive piezo buzzer. ![]()
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