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How do I make a noise-detecting traffic light? Answered

I am not sure how many people have seen these, but they are used in Elementary school alot. Basically, when the light is green the noise level is at the right level, if it is yellow it is getting a bit too loud and red is WAY too loud. I want to use this type of idea in my classroom. It doesn't have to be a traffic light but a series of light. I just don't know much about wiring.

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11010010110 (author)2009-02-07

use a mic to fetch the noise

amplify a bit (mic preamp)

connect diode to the output and then capacitor and resistor in parallel. this circuit is called am filter or envelope filter

the charge on the capacitor represents the average volume over few sec (time depends on values of capacitor and resistor)

now use opamp to compare this charge to a reference volume and feed the result to a led

you can build more than 1 comparation circuit to set multiple levels

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Sandisk1duo (author)2009-02-07

well.... i did a little research (google) it doesn't seem like you can make one....

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