On Sat, 2 Jan 2010 06:34:54 am Tom Uban wrote:
While this doesn't have any classic content, it
may be interesting
to some.
I'm working on modifying a Heath/Zenith wireless doorbell to play
a sound effect other than the really bad "ding dong" or
"Westminster"
version of the same. The new sound effect will be the Cloister bell
from the Doctor Who series.
Patching into the doorbell circuitry to detect when it is playing
its builtin sample is relatively easy. Coming up with a simple method
of outputting my new sample is a bit trickier. As I recall, there were
some specialized ICs out a few years back which would do just this
sort of thing. I've also considered connecting a basic mp3 player.
Other suggestions?
Thanks and happy new year to all!
--tom
This is a nice idea!
I used something like this for a project that required a sampled sound.
Timer -> Counter -> EPROM -> DAC.
The timer is set to double the sample frequency. The counters were a few
74LS161's. Next a standard 8-bit EEPROM (or EPROM) and the DAC was a simple
R2R ladder connected to an op-amp to buffer it. There was also some glue logic
to start and stop it counting when it was triggered and when it reached the
end of the sample.
Here's a diagram of an R2R ladder,
http://www.ermicro.com/blog/wp-content/uploads/2008/11/basic_r8.jpg
Where R can be 10k ohms and 2R can be 20k ohms. You will probably want to
buffer the output with an op-amp.
To get a ROM image you can use Audacity and export the sample as an 8-bit,
unsigned, raw data stream.
This may be a little more complicated, but I think the components will be much
simpler to obtain.
Alexis.