[sci.electronics] Sine wave generator

cook@stout.ucar.edu (Forrest Cook) (07/20/89)

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)
/|\ /|\ {husc6|rutgers|ames|gatech}!ncar!stout!cook
/|\ /|\ {uunet|ucbvax|allegra|cbosgd}!nbires!ncar!stout!cook

torkil@psivax.UUCP (Torkil Hammer) (07/21/89)

In article <790@serene.UUCP> gbell@pnet12.cts.com (Greg Bell) writes:
#
#I recently took on a somewhat dumb "home project".  I wanted to build a
#door-bell extension since the downstairs bell isn't audible from upstairs.
#
Sears, Roebuck et Cetera (catalog sales) carries a cordless doorbell.
You mount a battery powered transmitter at any convenient point near the door
and plug in bell units in 110V outlets in the rooms where you want them.
Simple, flexible and convenient.  Units are like $20 each.
The range is advertised as being something like 50 ft.
[I don't have one so I don't know how good they are.]

Of course it is not a hack.  But if you want maximum credit for
minimum work at a modest expense that is the way to go.

have fun

torkil

gene@cooper.cooper.EDU (Gene (the Spook) ) (07/21/89)

in article <790@serene.UUCP>, gbell@pnet12.cts.com (Greg Bell) says:
> 
> 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.  In addition, how do the sine wave generators
> that use the PTC of a particular light bulb work???

1) You might try the piezo element, complete with "ding-dong" driver IC,
that Radio Shark used to, and possibly still does, sell.  Loudness is ok
in a reasonably quiet room, but don't expect to hear it above your
vacuum cleaner or power tools.

2) Those light bulbs act as variable resistances in a feedback network.
To oscillate properly, the loop gain must be exactly unity. If it's less,
the signal won't regenerate and it will die out; if it's more, the output
will saturate and your sine wave will become badly distorted (chopped off
at the extremes).

You might want to try a ~wave-generator-in-a-chip like an XR2208 (Exar)
or an 8048 (Intersil).  Loads of fun.

						Spookfully yours,
						Gene

gbell@pnet12.cts.com (Greg Bell) (07/21/89)

cook@stout.ucar.edu (Forrest Cook) writes:
>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.

I've thought of that, but thought there'd be a better/cheaper way of doing
it... a more "conventional" way perhaps.

It just so happens I have an A-D, D-A, some RAM, a monitor EPROM, and an 8031
sitting in breadboard form on my desk in front of me.  I was basically trying
to record sound and play it back.

My goal is to have a telephone ringer that screams instead of rings 8-). 
Could do any number of other sounds too.  Biggest problem is getting the audio
digitized, and burned into an EPROM.  

My experimentation with A-D and D-A is producing questionable results.  I
really need to ad an anti-aliasing filter to the input, some low-pass on the
output, and a sample and hold circuit.  Problem is, I'm outta breadboard
space!  I need to wire-wrap the 8031 brain portion so I can free up the
breadboarding sockets for more fooling around.

    Greg Bell_________________________________________________________
      Hardware hacker          |
      Electronics hobbyist     | UUCP:  uunet!serene!pnet12!gbell
      EE major at UC San Diego |

pec@necntc.nec.com (Paul Cohen) (07/21/89)

NEC has a line of speech generation components which can also be
programmed to generate various tones of which a sine wave (up to about 
3 KHz) would be the simplest example.  DTMF signals are examples of 
somewhat more complex sounds that are possible.  Code for the DTMF 
signals is available as a library.  Since so many frequencies are 
possible, sine waves would have to be custom programmed, but this is 
not difficult.

An open question for the readers of this news-group: what frequencies of
sine waves do you want?   We could add them to our library fairly
easily.

The parts, uPD775x (x = 5, 6, 7) come as mask ROM parts with various
sizes of ROM.  There is also a version, uPD7759 which uses external
memory (RAM or ROM) and a one-time programmable version the uPD77P56.
All of these parts include a D/A and filter circuitry and require only
an external ceramic resonator for clocking.

Call (508) 655-8833 
or   (800) 366-3782 for more information.

bill@videovax.tv.Tek.com (William K. McFadden) (07/22/89)

In article <790@serene.UUCP> gbell@pnet12.cts.com (Greg Bell) writes:
>I recently took on a somewhat dumb "home project".  I wanted to build a
>door-bell extension since the downstairs bell isn't audible from upstairs.
>
>The easy way to do this would be to put another doorbell in series (or
>parallel?) with the one downstairs.  I tried both ways, but neither worked. 
>Either one bell would ring, or neither.  But not both.

In series there would too little voltage to operate (e.g., 12v each instead of
24v).  In parallel they would probably have too little current (power xfmr
too small).  You can get this to work by doubling the voltage or current,
respectively.  I'd be in favor of doubling the transformer current and hooking
them in parallel, since the other solution uses higher voltages (e.g., more
dangerous).

>So, I thought it would be fun to build a simple circuit that would sense the
>drop across the xformer or bell downstairs and generate two sine waves in
>sequence, each decreasing in volume (ie. "Ding-dong").

I know this is cheating, but Radio Shack has a beeper that does this (ding-
dong, I mean, not sense the voltage drop).  You would still have the challenge
of designing the "voltage drop sensor."
-- 
Bill McFadden    Tektronix, Inc.  P.O. Box 500  MS 58-639  Beaverton, OR  97077
UUCP: bill@videovax.Tek.com,  {hplabs,uw-beaver,decvax}!tektronix!videovax!bill
GTE: (503) 627-6920         "The biggest difference between developing a missle
component and a toy is the 'cost constraint.'" -- John Anderson, Engineer, TI

gbell@pnet12.cts.com (Greg Bell) (08/15/89)

I recently took on a somewhat dumb "home project".  I wanted to build a
door-bell extension since the downstairs bell isn't audible from upstairs.

The easy way to do this would be to put another doorbell in series (or
parallel?) with the one downstairs.  I tried both ways, but neither worked. 
Either one bell would ring, or neither.  But not both.

So, I thought it would be fun to build a simple circuit that would sense the
drop across the xformer or bell downstairs and generate two sine waves in
sequence, each decreasing in volume (ie. "Ding-dong").

I didn't know what I was in for!  Sine wave generators aren't too trivial.  I
tried one using a 741 with a twin-T circuit in the feedback loop.  This worked
OK, but was hard to tweak into working right.  Also, making the amplitude
decrease turned out to be difficult.

I opened up National's Linear App book and found a zillion different sine wave
circuits.

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.  In addition, how do the sine wave generators
that use the PTC of a particular light bulb work???

    Greg Bell_________________________________________________________
      Hardware hacker          |
      Electronics hobbyist     | UUCP:  uunet!serene!pnet12!gbell
      EE major at UC San Diego |

c37189h@saha.hut.fi (Suomalainen Harri Olavi) (09/05/89)

In article <790@serene.UUCP> gbell@pnet12.cts.com (Greg Bell) writes:
>
>I recently took on a somewhat dumb "home project".  I wanted to build a
>door-bell extension since the downstairs bell isn't audible from upstairs.

You could do it with a extremely simple device: Rectify voltage your bell works
with, smooth it with a capasitor and connect a piezo buzzer on it!
---  
E-mail:  c37189h@saha.hut.fi             *   If you're feeling good, don't  *
UUCP:    ...!mcvax!santra!saha!c37189h   *   worry  -  You'll get over it!  *  

ISW@cup.portal.com (Isaac S Wingfield) (09/07/89)

Greg Bell writes:

I'm going to all this trouble.  In addition, how do the sine wave generators
that use the PTC of a particular light bulb work???                          

The light bulb's non-linear resistance is (hopefully) used to
control the amplitude of the oscillation to keep the amp in
it's linear region (necessary for good sines). Messers Hewlett
and Packard made a bunch of money off that kind of oscillator!

For the doorbell, try a big L-C set up for damped ringing (sorry)
Maybe you can synthesize the L from an op-amp.

Isaac    isw@cup.portal.com

myers@hpfcdj.HP.COM (Bob Myers) (09/09/89)

>Greg Bell writes:
>
>I'm going to all this trouble.  In addition, how do the sine wave generators
>that use the PTC of a particular light bulb work???                          
>
>The light bulb's non-linear resistance is (hopefully) used to
>control the amplitude of the oscillation to keep the amp in
>it's linear region (necessary for good sines). Messers Hewlett
>and Packard made a bunch of money off that kind of oscillator!

Specifically, find a good reference to the "Wien-bridge" oscillator circuit;
the bulb is used as one of the resistances in the resistive-divider side of 
the bridge, and so provides "automatic" amplitude adjustment.


Bob Myers  KC0EW   HP Graphics Tech. Div.|  Opinions expressed here are not
                   Ft. Collins, Colorado |  those of my employer or any other
myers%hpfcla@hplabs.hp.com               |  sentient life-form on this planet.