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Old 12-23-2011, 04:21 PM
efe_vural@yahoocom efe_vural@yahoocom is offline
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Default Piezo buzzer(self or external driven) or piezo transducer help

Hello everyone,

In my lab project i have to use a buzzer in a part and produce a note of certain frequency. I had buzzers from last semester(THDZ written on them, circular, no other information). I built a function generator with opamp. Now i am assuming that(since after a search for one day, i could not found anything about that, I think the days buzzers are driven with opamp is ancient) i have to connect buzzer in betweeen directly the output of the opamp and ground levels and the buzzer will sound the "musical note" according to the given frequency. By the way my function generator includes a square wave and triangular wave generator and single supplied so the output is above a dc avarage level with respect to ground.(
I built the circuit and i measured the musical note coming out of buzzer using my guitar tuner program. And it always give the same sound Eb7(also not a change in the feeling of the sound: same tone). So i made my homework and searched the internet and all i could find is some buzzers are externally driven and some buzzers are self driven. The conclusion from this seems to be my buzzer is self driven and will always give the same frequency and does not need ac waveform. However i have to buy an external driven buzzer so that it will produce a musical note according to he frequency of the driving waveform.

Is that right conclusion?
And also if it is right am i going to just connect buzzer between the circuit ground and generator output?
In another forum i am told that i have tu use a piezo transducer. But project information clearly says "use buzzer".
Is it possible to use an external driven buzzer ( for this purpose?
Might i be not producing different musical notes due to the avarage dc offset in the output of opamp; caused by single voltage supply?

Thanks for your help
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Old 12-23-2011, 07:46 PM
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Bill_Marsden Bill_Marsden is offline
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In general a buzzer generates a tone that is fixed. There is a class of piezo buzzer where you add the transistor and it also generates a fixed tone. This describes the two classes you are talking about.

What you want is a speaker. It can be a dynamic or piezo speaker, but it will reproduce the audio you feed it.
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