Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: Admin on September 22, 2006, 09:38:07 PM
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Anyone know where I can get cheap (under $500) underwater sonar sensors?
It must be easily to interface with a microcontroller, and not be bigger than 4"x4"x4"-ish.
Those cheap fish finder sonar appear useful, does anyone know how to hack them?
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Are you competing in the AUV competition? (http://www.auvsi.org/competitions/water.cfm)
My school took 5th last year and pushed MIT to the sun! (the top five teams from the previous year get the shaded spots)
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I am building a robot fish for research on fish propulsion (I cant give out more details until the paper release in April, 2007).
I am trying to make the AUV small enough to fit inside a backpack and yet still have effective sensors, so was lookin for other ideas . . .
Yea I saw the video from the competition a few months ago, was studying it for ideas to 'steal' ;)
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What capabilties are you looking for? I know our AUV team originally built a depth sounding sonar that was really cheap and easy. I would imagine the fish finder could be hacked with great difficulty, but their resolution is probably too course and effective range to great for your needs, and of course most of them are 2D.
The AUV guys recently got REALLY fancy, but their solution is way to big for what you're looking for (not to mention expensive!).
Good luck w/ ur project. I can't help but think of that dolphin from SeaQuest that John Brandis rode around in. Can't wait to hear the results in 6 months!
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Initially it must work in just a swimming pool, for experimental test work. The long term however, it must be capable of navigating ocean shorelines and coral reef like environments. Sonar is required for the ocean environment, but would be nice for the pool experiments. Depth will never go below ~50 feet.
I would need the device to locate and follow slow moving objects about the size of a small car from a max of 50-ish feet away. So its just short range.
Price isnt a problem, I can afford it. Small size, and interfacibility with a microcontroller, is however a must.
2D low quality coarse resolution sonar is fine. I know a few algorithms that can estimate 3D using only 2D info. No precision work being done.
I searched all the companies that supplied sonar for each team for the AUV contest you mentioned, but the weight for even the smallest lightest ones were almost equal to the weight of my vehicle (8 pounds).
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Admin,
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
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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.
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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.
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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
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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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If you waterproof the air-based transducer, it might block/muffle the emitted sounds when in water. I think Ill just get out a multimeter/scope and see what I can get from a hacked fishing sonar. And call up the manufacturer, as Militoy said, too. Just been busy lately to get back to it . . .
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I talked to the guy from Devantech, with the idea of replacing the transducers with solid aluminum face transducers, but he came back and told me it wouldn't work.
Underwater sonar is really tricky - I would stick with either the solution I posted earlier, or trying to reverse engineer a fish-finder. If you've got more space and money, there's a company in New Zealand that markets an NMEA depth sounder for boats that produces an RS-232 data stream...
http://www.cruzpro.com/active.html
- Jon
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As a quick note - and maybe a cheap way to play with your idea - Harbor Freight Tools just put a portable fish finder, with a floating transducer, on sale for $39.99. In-store sales only - sale ends Dec 26. 45 degree sonar angle; runs off (4) AA batteries; range 0-100 ft. I'm going to pick one up this weekend, and tear into it, just for the "cool" factor of seeing how it works.
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send us pics/details when you do! :)
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I've seen a documentary on submarine sonar. They use a piezo transducers - I think mainly because they work as both transmitter and receiver.
In order to get them to work for submarine operations, they stack them up. This increases the "throw" of the devices, and their energy output. It's a mechanical way of adding up their attributes.
I just received the little piezoelectric transducers that I ordered from Edmund Scientific. I'll let you know how they "stack up."
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Today I stumbled upon these waterproof sonar transducers:
http://www.murata.com/auto/pdf/14ma40_e.pdf
The more complete datasheet can be found here:
http://www.murata.com/catalog/p19e.pdf
Two issues . . . doesnt come with sonar driver circuitry . . . anyone have experience with that?
The other issue, even though they are waterproof, is Im still not entirely sure they will work underwater. The datasheet says:
Applications
1. Back sonar of automobiles
2. Parking meters
3. Water level meters
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Hello All,
I was wondering if you guys have found a solution to this subject. I know this is a very old post by I am doing the exact same and looking for a way to hack a Transducer or a fish finder.
If anyone can please give me a hint, i'd really appreciate it.
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I've been using the Maxbotixs water resistant sonar, and then waterproofing it using RTV. Only one of them fried, not sure why, but my others still working fine.
http://www.maxbotix.com/Ultrasonic_Sensors.htm#XL-WRC (http://www.maxbotix.com/Ultrasonic_Sensors.htm#XL-WRC)
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I've been using the Maxbotixs water resistant sonar, and then waterproofing it using RTV. Only one of them fried, not sure why, but my others still working fine.
http://www.maxbotix.com/Ultrasonic_Sensors.htm#XL-WRC (http://www.maxbotix.com/Ultrasonic_Sensors.htm#XL-WRC)
I'm guessing they didn't report distance correctly according to the spec sheet anymore due to different speeds of sounds. What was the conversion you observed?
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I don't remember offhand, but I just fed it to the ADC and then ran my own conversion equation. I think it was something like ~4x. The range was significantly higher, too.
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Guys, do you have found out solutions for that? I have same problem. I would like to get underwater depth information for microcontroller. Are nobody hacked an old handheld fish finder?
If you have some solutions could you show it others?
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Low cost NMEA transducer:
http://www.hodgesmarine.com/Garmin-Intelliducer-Nmea-2000-Transom-Mount-p/gar010-00703-00.htm
(http://www.hodgesmarine.com/Garmin-Intelliducer-Nmea-2000-Transom-Mount-p/gar010-00703-00.htm)
And same in other place:
http://www.fishfinder-store.com/garmin-010-00703-00-nmea2k-transom-mount-transducer.html (http://www.fishfinder-store.com/garmin-010-00703-00-nmea2k-transom-mount-transducer.html)