Musical Beat Sensor

Jon Keinath

I am working on my 2006 New Years Sphere, it is basically a mini version of the Ball in New York. It would be really cool if I could make it respond (like change color) to the beat (or a specific frequency) of an audio sorce (cd player) durring the time it is just sitting at the top. I am thinking that this would be easily to implement with some sort of external circuit. I have been looking at a "light Organ", but all these switch 110ac and all I need to do is trigger a pin on my Javelin stamp, (which durring this time would be running a tight loop, looking for an input). If there is anything else that you need to know to help me in this task just ask.
Thanks
-Jon

Beau Schwabe

Jon,

Seems like what you need is a low pass filter connected to an Op-Amp with a gain of about 10dB
to detect the music "beat".

Here is a link that may help to determine RC( Resistor and Capacitor) values for a low pass filter.
www.muzique.com/schem/filter.htm

Here is a site that deals with OP Amps.
www.bcae1.com/opamp.htm

From here the Stamp can monitor the output of the OP Amp and do in software whatever else needs
to be done as far as triggering specific events like color or whatever. It might be interesting to have
more that one frequency cutoff for a project like this.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Clock Loop

I did a BPM device that accepted a button input(with alot of help),
you might be able to modify the code with the above low pass filter to get waht you want.

Really all it did was calculate the BPM that I was clicking my button at.... Not sure if it will help you, but here...

http://forums.parallax.com/showthread.php?p=540831