For my next lesson I need to get a piezoelectric buzzer and while shopping for them I read that there are active and passive buzzers. The exercise has me use a transistor to activate a buzzer if something happens.
The passiveness stumped me. I understand how a transistor could pass a current to a buzzer based upon another event.
So how would a passive buzzer work ?

Thanks.
.

 

https://www.allaboutcircuits.com/textbook/semiconductors/chpt-1/active-versus-passive-devices/

https://en.wikipedia.org/wiki/Electronic_component#Passive_components

 

I am going to venture a guess here as to an active or passive buzzer or as the case may be an active or passive piezoelectric buzzer. My guess is that with a passive device you need to send it an AC signal of some frequency to have it make a sound, much like sending a signal to a speaker. My guess is that an active piezoelectric buzzer has an on board oscillator to create the sound so we only need provide it with a DC signal. Turn it On for sound and Off for silence. That said and if I am correct my guess is you want an Active buzzer where the oscillator and speaker are self contained and you would turn it On or Off using for example a transistor.

Ron

<EDIT> I see dl324 has it already covered. </EDIT>

 

A passive speaker is called a transducer. An active buzzer beeps not buzzes so I call it an active beeper.
An active buzzer is an old mechanical one.

 

Just in general _active_ means positive amplification (which requires energy/pwr) from 3'rd source and passive means all energy is just from signal! Sry if response is 2 general

@Audioguru just 2 say I was fan of u way b4 I joined! vry happy 2 see u back on here!

 

For my next lesson I need to get a piezoelectric buzzer and while shopping for them I read that there are active and passive buzzers. The exercise has me use a transistor to activate a buzzer if something happens.
The passiveness stumped me. I understand how a transistor could pass a current to a buzzer based upon another event.
So how would a passive buzzer work ?

An "active buzzer" contains a circuit that drives the piezoelectric transducer element with an AC signal to produce sound. Some produce a steady tone, while others produce an intermittent, "beep-beep-beep" sound. They require DC power to operate, usually 3-20 volts or so at a couple of milliamps.

A "passive" buzzer contains only the piezoelectric transducer element itself, with no driving circuitry. They have to be driven with AC (or pulsating DC) at the desired frequency to produce sound. Some are provided as just the raw transducer (usually a small brass disc with the ceramic piezo element bonded to it) with or without connecting wires, others with the piezo in a plastic housing with pins to facilitate mounting on a PC board.

 

@OBW0549 Thanks for taking effort for proper explanation!

So I plead guilty to cynicism but totally innocent? So ok! Not totally guilty to charge of total laziness

 

Hi Aleph(0), thanks for the greeting.

A piezo transducer is not a speaker, it is a squeaker because it produces no low frequencies like a speaker.

 

A piezo transducer is not a buzzer, but a passive transducer. It requires an alternating voltage to get it to emit sound.

A piezo buzzer has a built-in oscillator and requires DC to power the oscillator circuit.

 

I think that I understand it. For me before, the difference was that one was powered and one was not.
For these pesky buzzers, the DC powered one, which the lesson calls for, is what I need. And if I read the responses accurately, it will have the internals to generate the audio signal.
The passive needs to have the audio signal sent to it.
Hmmm, are audio signals considered ac ?

Thanks

 

I think that I understand it. For me before, the difference was that one was powered and one was not. For these pesky buzzers, the DC powered one, which the lesson calls for, is what I need. And if I read the responses accurately, it will have the internals to generate the audio signal. The passive needs to have the audio signal sent to it.

That is correct.

Hmmm, are audio signals considered ac ?

Yes.

 

audio signals considered ac

It depends. Does the signal have a near zero DC voltage when measured? Then yes.
Is the AC superimposed on a DC voltage? Then it could be considered to be a pulsating DC.
Interpretations are many. It all depends on your perspective and the application under review - what communicates the situation the best.