Using an ultrasonic sensor underwater? or other ways to detect close objects

[Jon Clark]

Hey Everyone,

Has anyone ever tried to use the ultrasonic ping sensors underwater?  I know that the sensor reading would obviously be a lot different because sound traveling faster through water and because of the extra layer of whatever material is used to make it waterproof. Although it would be nice to be able to get an actual distance to the object, I'm mainly concerned with just knowing that I'm 6" to 12" away from the object.  What I'm trying to do is automate the depth that the ROV travels at so that it stays just slightly above the bottom of the lake floor.  I'm open to any other ideas anyone has as well.  

[Pat McCarthy]

That’s sonar, right?

 

 

Patrick McCarthy

 

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[Ben Hibben]

Sounds like you need a sonar system; water conducts certain frequencies better than others but I'm not sure ultrasonics would work.

Blenster

[Brian Wagner]

Sounds, in water, travel 25 times faster than air.  It would be an interesting experiment to see how it works.

On Mon, May 7, 2012 at 2:54 PM, Jon Clark <jdc...@gmail.com> wrote:

[Jon Clark]

For most purposes... Yes SONAR is the way to go.  The problem is the price and complexity of using SONAR.  The SONAR system I just purchased last week for the ROV cost a little over $8,000! (and that came only second to the next level up which cost $30,000!)  For the ROV SONAR we are using a forward scanning sonar which is great for navigating but now I just want to be able to add something a lot less costly that will let me know when I'm getting close to the floor.    

[Brian Wagner]

How about something mechanical like a rod with a magnet?

[Jon Clark]

The problem with anything mechanical is the fact that the ROV has to physically touch the floor which is the reason from trying to do it with some type of ultrasonic or sonar.  When anything touches the floor of the lake, sea, etc, it causes a major amount of dirt/silt to be thrown up in the cameras view.  You can go from cyrstal clear picture to dirt storm by just barely touching the floor.  

On Monday, May 7, 2012 2:54:23 PM UTC-4, Jon Clark wrote:

[Ben Hibben]

As far as I understand it an ultrasonic sensor is basically "sonar in the air" -- why not build a simple sonar?  Doesn't need to do scanning and terain mapping; jut return a distance value, right?

Blenster

[Pat McCarthy]

What you are doing is basic echo sounding…  I have seen small devices that look like a flashlight… put it in the water, press the button, get depth.

I think they can be found in marine catalogs

Much more common is the “fish finder”… which looks for 2 “return signals” showing a soft bottom (fish) and a hard bottom (seabed)

 

In your case, if thick, it’s return “silt layer” and “Hard bottom” J

 

PS, IIRC, you don’t need to actually touch the bottom, your impellers are downward facing, right? So anywhere close and you’ll stir up a mess J

 

Hey, you get a place to practice?

I have a small pond (small turtles)

And a bigger lake (Bigger Turtles) you could practice in…. (I Need to get permission if you are interested in the big lake…)

 

Patrick McCarthy

 

T 502.476.9878

C 502.939.1756

pmcc...@humana.com

 

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[Jeff Johnson]

Fish finder perhaps?

[Tim Miller]

you need some underwater transducers, you can hack them off of fish finders or buy them seperatly, they work exactly the same as a regular ultrasonic ping sensor does but just have different math for being in the water.

adafruit forum suggested this when I searched for underwater transducers but depth transducer appears to give better results

http://www.cruzpro.co.nz/active.html   

http://www.downwindmarine.com/Depth-Transducers-p-1-c-5293.html 

[Lockadoc]

Just tonight I cut the old sonar sensor that was on the bottom of my boat, it is from before I owned the boat I do not have the readout part but you can have it if you want.

Or go to Bass Pro Shop you can get a deapth sounder for $100.00 .

Bill S

Sent from my iPhone

[Brian Wagner]

discussions like this are why LVL1 is so AWESOME!

[Jonathan Clark]

Hey Bill,

I def wouldn't mind making use of the one you stripped off your boat if you'r not going to use it anymore.  Might make the boss happier having something to test with before we go out and buy a bunch too.  

[Lockadoc]

It is in my truck 

Next time I am there I will drop it off

Bill S

Sent from my iPhone

[Richard Weisbeck]

Hello

This is 4 years later, so hopefully you haven't moved on to other things.

I would like to know if you found a practical solution .

I need precisely the same device.

 I would like to maneuver my ROV towards the bottom, detect the bottom, and stop further decent at about 8 in. above the lake bottom.

Richard

On Monday, May 7, 2012 at 11:54:23 AM UTC-7, Jon Clark wrote:

[Richard Weisbeck]

On Monday, May 7, 2012 at 11:54:23 AM UTC-7, Jon Clark wrote:

[Brian Wagner]

I wonder what kind of fishing sensors the fishing community uses.

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[Greg Miller]

I can't imagine one of the ultrasonic sensors working underwater for two reasons: 1) high frequencies don't travel through water as well as they do through air, and 2) water is much heavier so a stronger force is needed to create vibrations.

I know typical audio speakers are strong enough to produce audio in shallow water when in a waterproof housing (I tested the waterproofness of my waterproof weather radio).  I imagine the pressure becomes a problem pretty quickly though.

--

[Joe]

SONAR is just sound waves.  Fish finders?

Joe

-------- Original message --------
From: Greg Miller <gmi...@gregmiller.net>
Date: 04/12/2016 6:00 PM (GMT-05:00)
To: lv...@googlegroups.com
Subject: Re: {LVL1} Re: Using an ultrasonic sensor underwater? or other ways to detect close objects

[Brian Wagner]

Trained dolphin?