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John,
You have to match the natural resonance of the buzzer.
Putting a resistor is series allows it to try and resonate.
If you ac couple and adjust frequency, you will find it gets louder as
you approach the resonance frequency.
Ray


On Sun, 1 Apr 2007 21:30:34 -0700 (PDT), John Chung wrote:
>=A0I have been trying to understand the theory of why my
>=A0buzzer is not working as it is suppose to be*at least
>=A0to my understanding*.
>
>=A0I managed to salvage a buzzer from a PC. It looks some
>=A0thing like this.
>
>=A0http://www.rdiusa.com/products/Audio/DMT-12%20Srs.html
>
>=A0On the component it does not state the manufacturer so
>=A0I was left to identify the type of buzzer. Magnetic or
>=A0piezo. I applied the buzzer leads across the PIC i/o
>=A0pins PORTA 0 and ground. I checked the current
>=A0consumption during Q and it was draining about 32mA.
>=A0That was when I concluded that it was a magnetic
>=A0buzzer like the link above due to the coil.
>
>
>=A0I measured the resistance of the buzzer which was 15
>=A0ohms. Now I pulse my i/o pin and there was no audible
>=A0sound. When I place a resistor in series with the
>=A0buzzer I can =A0hear an audible sound from the buzzer.
>=A0Now comes the question. Why do I need a resistor in
>=A0series? It is due to the time constant of the coil
>=A0that I need to reduce it? =A0t =3D L/R? Currently it does
>=A0not make sense here.
>
>=A0Can anyone help me understand the theory behind this?
>
>=A0Thanks,
>=A0John




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