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From: Robert Baer
X-Mailer: Mozilla 4.75 [en] (Win98; U)
Subject: Re: Buzzer/Inductor question
Date: Tue, 08 Oct 2002 07:47:48 GMT
NNTP-Posting-Date: Tue, 08 Oct 2002 00:47:48 PDT
Organization: EarthLink Inc. -- http://www.EarthLink.net
Daniel M wrote:
> Sorry, I was mistaken in the values. Yes this is how it is hooked up, but
> instead of a 10uf cap it is a 10nf (.01uf).
> It was in the documentation on the web but the processor is End Of Life and
> the documentation is not on the web anymore. I have requested another copy
> from the MFG.
> Ok so with the new value, any theories?? Thanks.
> "Tom Faloon" wrote in message
> > Daniel,
> > You are right. This circuit does not make sense.
> > The 10uF to Vcc would kill any signal fed through the 0.1uF.
> > Is the circuit given in a document which is available on the web ?
> > Tom Faloon
> > http://www.faloon.co.uk
> > Daniel M wrote in message
> > news:vH6o9.13544$lV3.firstname.lastname@example.org...
> > > I have a question about a buzzer circuit i am working on. I have a CPU
> > that
> > > has a buzzer output to drive a simple buzzer. I dont understand the
> > > circuit and wanted to know if someone can explain it....
> > >
> > > It runs from the CPU output, through a .1uf cap to a buzzer/inductor.
> > > other side of the buzzer is tied to ground. The buzzer side of the cap
> > a
> > > 10k pulldown to ground and a 10uf cap to VCC.
> > >
> > > Ok i can possibly see the series cap and pulldown being sometime of RC
> > > filter for the buzzer but the cap to VCC has got me stumpped. Am i wrong
> > on
> > > this? what is the other cap for? any explinations? Thanks.
> > >
> > > Daniel.
> > > email@example.com
> > >
> > >
A 0.1uF drive and 0.01uF load gives about 90 percent to the black box.
Better, but still crazy.
If a microcontroller or CPU is supposed to drive a noisemaker, a
direct drive is one way, and better to drive a driver so the transistors
on the drive pin do not have to be so large.
Now, if that black box is an inductor (driving a diaphram), then the
0.01uF capacitance becomes part of a resonant circuit, making sense.
Perhaps the drive from the CPU is an impulse and the output is
nominally in tri-state mode; then the 0.1 coupling capacitor would be a
part of the resonant circuit for a short period of time; also making
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