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Topic: Non-Line-Of-Sight Distance Sensors (Read 419 times) previous topic - next topic

cr0sh

To my understanding, most speakers are capable of emitting high frequency.
I suppose that would depend on your definition of "high frequency". In general, high frequencies within the range of human hearing are done with tweeters:

http://en.wikipedia.org/wiki/Tweeter

There is a particular class of tweeters, designed to go over 20 kHz (generally accepted upper-limit of human hearing):

http://en.wikipedia.org/wiki/Super_tweeter

Over 20 kHz, though, you are in ultrasonic territory - and should look into ultrasonic transducers. For long distances, you also need more power (wattage) to drive the transducer (whether a standard tweeter or ultrasonic).

Finally realize that sound is transmitted in a "cone" pattern, and the lower the frequency, the wider the cone spreads (in general - it is also a function of time); ultrasonic transducers typically have narrower "spreads" than non-ultrasonic transducers.

However, the mic is the concern. What is my criteria for buying it?
Well, your main criteria is that it can respond to the frequency range that you'll be generating, and have a peak detection centered around your generated frequency.

Also, how can I use the arduino and the mic to determine the frequency of sound?
You shouldn't really need or want to do this; instead, you tune your transmitter and receiver amplifiers for a particular frequency, ideally centered at the peak of the generation of the transducer being used on the transmitter - and if your receiver "mic" is in the same area, that amp should be tuned for that as well. Then, the receiving end should simply output a HIGH or LOW value you detect with the Arduino.

You would need a way to signal the receiver that you just transmitted a ping (use RF or light), so you can measure the time delay and get distance. Lastly, you would want a minimum of three transmitters (spaced around the work area of the robot platform) in order to triangulate and calc the distance.
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

Bear95

Thanks again guys for your inputs.  I have come across this tutorial: http://www.instructables.com/id/Arduino-Audio-Input/?ALLSTE

Please let me know what you guys think. Should I go ahead, buy the equipment, and give it a shot?  Or are there certain aspects that the author is overlooking?

Any input is much appreciated.

Thanks :)

michinyon

Here's three suggestions:

(a)  a fixed grid of laser beams across your space,   each modulated differently,  so when your devices crosses a laser beam it can determine which beam it has crossed.

(b)  Make some boards with large simple shapes painted a uniform colour,  around your space.  Have a rotating camera on the top of your car.  From the direction and apparent size of the easily detectable shapes,  you can determine your position.

(c)  Use the arduino to sequential open the trapdoors of a dovecote on top of your car,  releasing a flock of carrier pigeons.

KenF

(c)  Use the arduino to sequential open the trapdoors of a dovecote on top of your car,  releasing a flock of carrier pigeons.
You would need to release the carrier pigeons sequentially, otherwise once the flock has gone, the vehicle would have no reference to find it's way home.

Maybe a turnstyle type system. 

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