detecting specific sound frequency

Spineless Cougar

I'm working on a combat information center automation project. One of the things we are doing is a sound tract of sound effects and people speaking. Currently, the plan is to play individual sound files directing them to a BS2 with a group of relays (currently seven of them) that would direct the sound to various speakers; the stamp would receive a command from the controlling PC letting it know which relay to close just prior to the sound file playing.

But, working with all these individual files (maybe 50 or 60) would be a pain. Now I'm thinking keep all the sounds in one file and put in high frequency sound signals that the stamp could recognize and close the appropriate relay when it gets the signal.

Is there any way for a stamp to read various high frequency sounds and flip a switch based on which frequency is received?

-Erik

Phil Pilgrim (PhiPi)

Take a look at the LM567C.

-Phil

pwillard

The LM567 is excellent advice... but it was not made clear how long the duration of frequency will exist.· In my experience with the LM567 (which isn't much, actually), ·the LM567 needs a little time to LOCK ON.

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There's nothing like a new idea and a warm soldering iron.

Phil Pilgrim (PhiPi)

A little more info: the LM567 can be used not only for detecting individual tones, but also for demodulating frequency-shift keying (FSK). The latter may be the most appealing, since you can use a single device and encode serial data for use with SERIN. You will want a period of marking (a single tone corresponding to a logic one) ahead of the data to get the unit in sync.

-Phil

metron9

http://focus.ti.com/lit/an/sloa093/sloa093.pdf

http://www.circuitdb.com/circuits/id/162


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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

Post Edited (metron9) : 11/3/2007 8:27:26 AM GMT

Spineless Cougar

Thanks for the info. The LM567C looks like the way to go.

-Erik

Tracy Allen

Note there is also a low power CMOS version, the LMC567, which has better characteristics in some respects.

The simplest way to use the '567 is to take the lock signal (pin 8) into a single Stamp pin. That pin will go low when it is locks onto a valid tone, so an presence/absence binary code on the tape could select the voice file. The tone can be high above the audio range if the equipment will support it.

The FSK as Phil suggested could potentially be more reliable. It think it requires more components and processing in addition to the lock indication, to sense the voltage on the loop filter or to count the lock frequency.

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Tracy Allen
www.emesystems.com