Shop OBEX P1 Docs P2 Docs Learn Events
Ultrasonic distance measurement underwater — Parallax Forums

Ultrasonic distance measurement underwater

eblanckeeblancke Posts: 26
edited 2009-09-17 20:47 in Accessories
I want to build an underwater pool cleaning robot and I need a network of sonar transmitters around the pool so I can locate and control the location of the robot by distance sensing and calculation. Does anyone have any ideas or experience? Will a normal ultrasonic transmitter (as used in ping and others) work underwater if it is placed in a sealed container?

Comments

  • LeonLeon Posts: 7,620
    edited 2009-09-13 19:28
    Probably not, as the container will attenuate the signal.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-09-14 16:27
    Underwater sonar tends to use different (usually lower) frequency signals and specialized transducers. Take care.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage

    Parallax Engineering
    50 72 6F 6A 65 63 74 20 53 69 74 65
    ·
  • FranklinFranklin Posts: 4,747
    edited 2009-09-14 19:17
    You might be able to hack transducers designed for fish finder/depth guages on boats.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Stephen
  • kwinnkwinn Posts: 8,697
    edited 2009-09-14 19:25
    You might also want to consider using leds to determine location by triangulation and transmission of data. Simpler and less expensive than ultrasound.
  • John R.John R. Posts: 1,376
    edited 2009-09-14 21:36
    I would also expect to have problems with echos and background noise, especially in a pool or other confined space. This problem is compounded in shallow water.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    John R.
    Click here to see my Nomad Build Log
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2009-09-14 23:46
    The fish-finders are a good source for ultrasonic stuff to hack - but, as John says, you'll probably have too many issues with echos - the pool will be like a giant, ultrasonic echo chamber --- Even messy for one tx/rx pair ... I know :-|

    You need a "tracking wire" of sorts ...

    Kwinn's got a neat idea worth exploring. If you could figure out a way to make an LED version of a rope light, you might be able to lay two down on both sides of the pool along the bottom, running the length of the pool. Make the lights sequence and just have one on in the direction it needs to go - it seeks that light. Have a bumper-feeler for when it hits the side, then it revereses direction, turn on the opposite light ... and it zig-zags back and forth.

    Another idea: if you could float a little transponder buoy on top, then you could put some kind of tracking wire/radio thingy on the pool's side.

    I guess if you don't really care what the pool looks like, you could paint the zig-zag line on the pool bottom - and use a modified line follower... for that matter, maybe you could use some kind of water proof UV paint , and use a UV tx/rx to track the line - then you won't see it [noparse]:)[/noparse])

    For that matter, if you haven't poored the concrete yet [noparse]:)[/noparse] then embed a tracewire <G>

    (see what happens when you get us started brainstorming [noparse]:)[/noparse])

    - Howard

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
  • John R.John R. Posts: 1,376
    edited 2009-09-15 01:24
    Or, possibly forget the "tracking" in this manner altogether, and use accelerometers. In essence, "dead reckoning" navigation. Touch sensors could confirm "wall contact".

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    John R.
    Click here to see my Nomad Build Log
  • steve_bsteve_b Posts: 1,563
    edited 2009-09-15 15:07
    I've got a fishfinder transduce sitting beside me that I've yet to play with!

    I need to scope my father-in-laws fishfinder to see what the signal is (I suspect a pulsed dc signal).

    Not sure how leds/phototrans will work during daylight hours....but I suppose it's a none issue if you only run at night (no background light).

    I'm itching to hack this transducer....but man, this is my first forum post in a long time!! I hope this doesn't get shelved with all the other money-making ideas I don't have! [noparse];)[/noparse]

    Cheers

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    <FONT>Steve



    What's the best thing to do in a lightning storm? "take a one iron out the bag and hold it straight up above your head, even God cant hit a one iron!"
    Lee Travino after the second time being hit by lightning!
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2009-09-17 20:47
    If you put a floating buoy top side, a variation of this might work:

    http://www.norrislabs.com/Projects/WatchBot/index.html

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Sign In or Register to comment.