Underwater speed? - Page 2


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  1. #41
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    Default Re: Underwater speed?

    Hi All!
    Again you guys are very correct. I cannot imagine running the sub in a stream, only a lake, pond, or swimming pool with still waters. In aircraft there are two measurements of speed, IAS (indicated air speed) and TAS (true air speed). IAS is the speed weather into the wind or with the wind while TAS is the speed over the ground as if you were a car. In this case we can realistically only work with IAS as far as I know.

    Best, Ed

  2. #42
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    Default Re: Underwater speed?

    How much money do you have? I found this http://www.airmartechnology.com/uplo...res/CS4500.pdf by accident and wonder if it might work. I'm also wondering if you couldn't find one used at a dock or salvager.

    The brochure is light on how to hook it up but it would fit your needs almost perfectly. After a quick search I couldn't find anything on the "Airmar paddlewheel format" this is supposed to put out.

  3. #43
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    Default Re: Underwater speed?

    Hello Ramius
    It looks like folks here were very helpful and I'm curious about what you came up with for a solution. I have a project that I'm working on and need speed through the water, using as small a sensor as I can.
    Thanks
    Mike

  4. #44
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    Default Re: Underwater speed?

    Hi Mike!
    Actually there are now a lot of answers to basic questions. First save yourself a lot of research by knowing that speed = PSI! As for the PIC code you can find it here at:http://www.picbasic.co.uk/forum/showthread.php?t=19572. For me I needed a "differential" pressure sensor from Seroflo ([email protected]). The reason for a differential is that as my sub dives pressure will increase so you have to subtract out "depth" pressure (Static Pressure) from the pressure on the bow (velocity Pressure). One technique I have used with my compass was to mount the sensor on top of the PIC. If you are using a surface mount PIC you will see the PIC fits comfortably under just about any sensor. You can use a CAD program to design your PC board and then convert the CAD drawing to Gerber files. It helps to create "Layers" in Cad that you can turn on and off so you can create you solder mask and "ground plane". You will probably end up with a double sided board so you can make one side say in red traces and the other side in blue traces. Do not forget to specify plated thru holes! Your board size will most likely be .625 x .625". About the only other design consideration will be to isolate the sensor from the water. Hope this helps.

    Best, Ed

  5. #45
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    Default Re: Underwater speed?

    Quote Originally Posted by AvionicsMaster1 View Post
    How much money do you have? I found this http://www.airmartechnology.com/uplo...res/CS4500.pdf by accident and wonder if it might work. I'm also wondering if you couldn't find one used at a dock or salvager.

    The brochure is light on how to hook it up but it would fit your needs almost perfectly. After a quick search I couldn't find anything on the "Airmar paddlewheel format" this is supposed to put out.
    That's very interesting.

    I wonder what would be involved in rolling your own version. Ultrasonic implies the use of sound, are there new devices out for robotics that could be used for this?

    I'm looking at the speeds involved in the specs at it's not NASA-type stuff. Except for the sensitivity of the sensor device, the rest seems within our grasp.

    Robert
    My Creality Ender 3 S1 Plus is a giant paperweight that can't even be used as a boat anchor, cause I'd be fined for polluting our waterways with electronic devices.

    Not as dumb as yesterday, but stupider than tomorrow!

  6. #46
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    Default Re: Underwater speed?


    Weight:
    —1.4 kg (3 lb)—Plastic
    —1.8 kg (4 lb)—Bronze
    usable aboard a model ... ???

    Alain
    ************************************************** ***********************
    Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
    ************************************************** ***********************
    IF there is the word "Problem" in your question ...
    certainly the answer is " RTFM " or " RTFDataSheet " !!!
    *****************************************

  7. #47
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    Default Re: Underwater speed?

    Hi Guys!
    The Airmar sensor requires a hole almost 3" in diameter! In models this is huge in comparison to a 1/8" pitot tube or just a single pressure tube used with a complete pressure sensor circuit that only takes up .625" (3/8") square! Ultrasonics is great and again the transmitter and receiver are about 1". Mike asked for something as small as possible. 3/8" is about as small as I can think of.

    Best, Ed

  8. #48
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    Default Re: Underwater speed?

    What about a radiometric hall effect type sensor/s placed on the inside hull and a magnetic steel wire (guitar string?) running perpendicular on the outside - equipped with a small hydro-resistive plane on the loose end? As the speed of the ship increases, current moves the wire and the hall sensor/s record the reduced/ increase field strength. I think that adjusting the sensitivity is as easy as adjusting the length and wire diameter of the sensor and the placement of the sensor along the length. It might take two sensors - one forward, one reverse.

    I also think a small tab hanging below the hull on a hinged fitting... an angle sensor measures the deflection as the sub moves through the water. May be oriented horizontally or vertically, using a spring. Forward is positive angles, reverse is negative...

    The ultrasonic holds promise - if the resistance of the external mechanism is not an issue. I imagine either one transmitter mounted flush amidships - a triangular reflector splitting the ping to receivers mounted fore and aft, or a more traditional setup with transmitter and receiver on both ends. Could temperature be eliminated as a factor by calibrating an offset at zero speed? Pressure remains a factor I think, but didn't I read that is currently measured?

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