Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!stout!cook
From: cook@stout.ucar.edu (Forrest Cook)
Newsgroups: sci.electronics
Subject: Re: Sine wave generator
Summary: A better doorbell
Keywords: Ding Dong
Message-ID: <3739@ncar.ucar.edu>
Date: 19 Jul 89 21:59:43 GMT
References: <790@serene.UUCP>
Sender: news@ncar.ucar.edu
Reply-To: cook@stout.UCAR.EDU (Forrest Cook)
Organization: Field Observing Facility, NCAR, Boulder, CO
Lines: 31

In article <790@serene.UUCP> gbell@pnet12.cts.com (Greg Bell) writes:
>I'm wondering two things:  What's the best/easiest way of making an electronic
>doorbell?  I'd prefer the attention-getting sound of a "ding-dong", that's why
>I'm going to all this trouble.

Greg, here is a possible solution that could be programmed to make many sounds:

[oscillator]->[4040 counter]->[EPROM]->[DAC]->[low pass]->[amp]->[speaker]
      ^-----[flip flop]<---stop---|
start----------^

You could store both the ding and the dong waveform as a sequence in the
EPROM, which could drive the DAC and output a digitized waveform.
Generate the desired wave form with a program and burn it into the EPROM.
The low pass could be built into the amplifier.
You could use an RS flip flop for the start/stop control, the button sets
the flip flop, causing the oscillator to start and count through the wave
table.  You could use 7 bits for the DAC control and the 8th bit to reset
the flip flop at the end of the pattern.  A 27256 EPROM (32K X 8) would
give you 4 seconds of sound at a sample rate of 8 Khz.
There are many variations on this basic circuit, don't be afraid to experiment.
A single chip micro could be substituted for the osc, counter, eprom, and
start/stop logic.

Personally, my doorbell is coupled into my "house computer" and causes a
speech synthesizer to say "ding dong" in a mechanical sounding voice (SC-01).

 ^   ^  Forrest Cook - Beware of programmers who carry screwdrivers - LB
/|\ /|\ cook@stout.ucar.edu (The preceeding was all my OPINION)
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