A couple of weeks ago I took one of the projects that came to the meetings last year using the arduino called the bzztbomb. I am trying to take this Arduino project to the next level in two ways.
# to create a board which would cleanly amplify the sound from the arduino board as an above board add on.
# To create a low cost board which could be used to for the finished product.
The schematic for the V-1 in its current form is at http://www.digithink.com/embedded/hardware/arduinosound/rev1/noisinout_reva.pdf
The eagle files are at
http://www.digithink.com/embedded/hardware/arduinosound/rev1/noisinoutdip_a.sch
and
http://www.digithink.com/embedded/hardware/arduinosound/rev1/noisinoutdip_a.brd
http://dorkbotpdx.org/files/images/postapril.preview.jpg
When I finished my prototype I was able to get stereo output by modifying the example sketchbook called play_melody_faded_volume but found that the sound out of the pwm volume control sounded aweful.
I started looking at filtering the output to get smooth outputs. One of the missing pieces of the documentation of the arduino AnalogWrite is the duty cycle of the timer. A web search had the timer running at everything from 400 hz to 10-32khz. Once I finally put the sketch on a scope I found that the pwm duty cycle is 2ms long.
500hz.
The sound being modulated is in the range between 261(c) and 523(C) hz. which makes 500hz a very unuseful value.
In otherwords the model included in the examples doesdnt work with ardueno – 0007.