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Cheap underwater sonar

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I put a file up on my web server:

http://www.huv.com/maus2.zip that the author sent me about 6 years ago.

I don't know if you've seen it, but it certainly looks interesting...

- Jon

Are you looking for just the transducer, or a complete system? Seems to me that there should be lots of small transducers available - I did a Google search on "low cost underwater sonar transducer", and came up with 294,000 hits. Several of my customers sell underwater imaging systems, and their transducers aren't much higher than your limit. It's the micro, and the data processing that cost a lot of $. Your idea of hacking a commercial fishing depth finder is a good one - some of the ones I've used show a beautiful profile of the bottom, at depths up to 1000 feet. To "hack" any device of that type, your first step would be to pick up a used unit; put a storage scope across the output to see what the output signal looks like; and give the manufacturer a call, and ask to speak with their Chief Engineer. You may be surprised how much help he may be willing to lend, once you explain what you're trying to accomplish.

You know, you could probably take a cheap above-ground sonar system and put some sort of thin plastic membrane on the reciever/transmitter... Then you could make your microcontroller turn around or whatever when the sonar read 5 feet instead of 0, or you could make a simple converter circuit as long as the output of the sonar unit was a straight voltage.

Sorry to ask a n00b question but how would a sonar pattern change from air to water?
IE would the sonar 'beam' change it's shape and develop more side lobes and such or would it pick up more random sound....just curious...I plan to stay on the ground but it seems like something I should know something about... ;D

The pattern of the sonar “wave” won’t necessarily be so different in water from that in air per sé, but the speed of the wavefront will be much faster in the much denser water. The main problem I imagine you would have using a transducer underwater that was designed for service in air, and vice-versa, is the frequency of operation. Most “sonar” transducers designed for use in air are ultrasonic, and the signal they produce will lose most of its useful energy within a very short distance underwater. Underwater sonar operates at a much lower frequency, and will not be effective at distance in an air medium.


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