Re: "ding" circuit

On Thu, 25 Jan 2007 11:35:10 -0700, the renowned Jim Thompson
<To-Email-Use-The-Envelope-Icon@xxxxxxxxxxxxxxx> wrote:

On Thu, 25 Jan 2007 18:31:03 GMT, Jan Panteltje
<pNaonStpealmtje@xxxxxxxxx> wrote:

On a sunny day (Thu, 25 Jan 2007 13:37:43 -0500) it happened Spehro Pefhany
<speffSNIP@xxxxxxxxxxxxxxxxxxxxxxx> wrote in
<0gshr2phgbiscgbdkc38ak8gd5vth0vjd0@xxxxxxx>:

On Thu, 25 Jan 2007 09:52:31 -0700, the renowned Jim Thompson
<To-Email-Use-The-Envelope-Icon@xxxxxxxxxxxxxxx> wrote:

On Thu, 25 Jan 2007 12:04:39 -0500, Spehro Pefhany
<speffSNIP@xxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Thu, 25 Jan 2007 09:26:05 -0700, the renowned Jim Thompson
<To-Email-Use-The-Envelope-Icon@xxxxxxxxxxxxxxx> wrote:

On 25 Jan 2007 07:13:12 -0800, Winfield Hill
<Winfield_member@xxxxxxxxxxx> wrote:

I'd like a simple circuit to make a nice quiet
pleasant-sounding "ding" that I can add to my
automatic coffee-cup heating circuit.* I'll
trigger the ding when the cup heater reaches
the exact best temperature and it turns off.
I'll keep it quiet so as not to wake my wife,
but loud enough for me to hear. I want it to
be a very pleasant sound so if she does hear it,
it won't disturb her. I can hear it now, dinggg.

* The coffee-cup heater I'm going to design.

Way back in the last century (~1975), before microprocessors were in
cars, I designed "ding" and various other warning sounds into a chip
for GM cars.

I started by recording their mechanical sound makers, then devising
R/C active circuits that matched the waveforms.

"Ding" is just an abrupt- start sinusoid that decays.

...Jim Thompson

Fast attack & relatively slow log decay, right?

IIRC, to get a really musical tone you need more than one frequency.

Probably GM and their customers wouldn't much care if it's just
bugging you about seatbelts, headlights or something.


Best regards,
Spehro Pefhany

Can't you direct record such a sound into RAM and simply play it back
?:-)

...Jim Thompson

Sure. Record the sound on a PC, use something like CoolEdit/Audition
to edit it and convert to the desired bit width (eg. 8 or 12 bits)
resample at the desired sample rate, export as csv, massage all the
numbers into assembler or C format (a few lines of Perl or awk maybe),
and write a little firmware program to read the table and spit the
output values periodically to a DAC or PWM. A second or two of fairly
decent sound would fit in the flash of a cheap micro without any kind
of compression. For example, a PIC18F87J60 with 128K of 10-year
retention flash program memory. The chip, a ceramic resonator and
perhaps an 8 or 12-resistor DAC (or MCP4922) and an audio amplifier.
Two 12 bit samples could easily be packed into 3 bytes. There are a
few micros with 10 or 12-bit built-in DACs (AD, BB/TI and Silicon Labs
come to mind).

Personally, for a one time sort of thing, I would buy a 15 Euro mp3 player
with 256 MB flash and remove the case and drive the buttons with some CMOS
transistors.
Then it can say more then 'ding'.
'Hallo Winfield the coffee is ready'.
Anyways I just managed to make the perfect soft 'ding' by
taking an erase rubber, sticking it on a pencil, and pinging
against an empty COFEE CUP.
'diiin'
Now to rent time in a dead room in the soundstudio.

MIT's music library had sound-proof listening cubicles... maybe your
library does as well?

...Jim Thompson

Can you see into them from the outside? ;-)


Best regards,
Spehro Pefhany
--
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