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From: Robert Baer
X-Mailer: Mozilla 4.75 [en] (Win98; U)
Subject: Re: Buzzer/Inductor question
Date: Mon, 07 Oct 2002 07:26:58 GMT
NNTP-Posting-Date: Mon, 07 Oct 2002 00:26:58 PDT
Organization: EarthLink Inc. -- http://www.EarthLink.net
Daniel M wrote:
> 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 sample
> circuit and wanted to know if someone can explain it....
> It runs from the CPU output, through a .1uf cap to a buzzer/inductor. The
> other side of the buzzer is tied to ground. The buzzer side of the cap has 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.
The circuit explaination does not make sense.
Are you saying that from a CPU pin that an 0.1 uF capacitor leads to
this black box "buzzer", other side is ground?
And then in parallel with this black box is a 10K resistor?
And a 10uF capacitor is connected from the high side of this black box
If true, it makes no difference whether that 10Uf goes to Vcc or to
ground; the 2 caps make a 100:1 AC voltage divider - so the CPU pin
toggling 0V to 5V will produce 50mV across a hi-Z device.
That does not make sense either, as 50mV drive will not make any kind
od noise (the 10K biases the 10Uf cap to keep it formed).
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