Is your piezo contained in a little plastic box or is it just a lose
plate ?
The box makes resonance and amplifies the sound a lot with resonance
frequency depending on size and shape of box.

-----Original Message-----
From: Spehro Pefhany [mailto:speff@INTERLOG.COM]=20
Sent: Sunday, February 10, 2002 10:33 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [pic]: Can you amplify with a single 2n2222 ??

At 01:34 PM 2/10/02 -0800, you wrote:
>So, using what amounts to the Freqout command from
>a stamp, I generate my tone, but it isn't loud enough.
>
>Can you make a little amplifier using a single 2n2222 transistor?

Well, sure, but I bet that's not the problem. The PIC has
a fair bit of output drive for a piezo (which basically looks
like a ~10n capacitor (depending on size).

Try this: Try driving *two* port pins 180' out of phase,
and connect the piezo across them. This gives you double the
P-P voltage across the piezo. Higher supply voltage will help
with both the output drive and the loudness. Make sure the
PIC supply is well bypassed.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the
reward"
speff@interlog.com             Info for manufacturers:
http://www.trexon.com
Embedded software/hardware/analog  Info for designers:
http://www.speff.com
9/11 United we Stand

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