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From: Richard Lamb
X-Mailer: Mozilla 4.72 [en]C-CCK-MCD NSCPCD472 (Win95; U)
Subject: Re: Loudspeaker and microcontroller
References: <firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: Wed, 23 Oct 2002 00:44:00 EDT
Organization: Prodigy Internet http://www.prodigy.com
Date: Wed, 23 Oct 2002 04:44:00 GMT
Look into the LM-386 (?) audio amp chip.
8 pin dip and a couple of Rs and Cs.
john jardine wrote:
> firstname.lastname@example.org (jools) wrote in message news:<email@example.com>...
> > Hi
> > Im trying to create a door sensor and door bell configuration using a
> > PIC and loudspeaker.
> > The problem is making the sound loud enough to hear, a peizo is not
> > really loud enough to hear so a small speaker is going to be used. The
> > problem is can I drive is directly from the uC pin? Or does it require
> > more current than this can supply?
> > Speakers I can get come in 4ohms, 8 ohms, 16ohms, etc. Which one do I
> > require to get the loudest sound possible? Do I need to amplify the
> > signal from the uC if so which speaker impedance is most suitable.
> Those peizo's even at PIC type power levels, can be unbelievably
> noisy. Maybe it's worth trying some other type.
> Hanging a low resistance small speaker straight onto the PIC pin will
> just flatten the logic levels. At best, a PIC pin can deliver about
> (5V@25ma)=1/8th watt (to a 200ohm load), which audio-wise is oh so
> You need an audio amp tacking on, to shift the power up to a couple of
> watts at least. Cheapest and quickest way is to buy one of the
> amp+speakers type that plugs into a PC sound card. Possibly just using
> the innards from them.
> (I agree the PIC doorbell project is very worthwhile doing, but to use
> 100,000 transistors to replace the bell!. Our technology is running
> riot :-)
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