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Low Power Triangulation Circuits

Discussion in 'Electronic Basics' started by [email protected], Jan 3, 2009.

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  1. Guest

    Hello,

    What I would like to do:
    Capture motion (not specifically human motion) in a room that is about
    3*3*3 meters. The system should be able to capture 16 'active' points
    in said room.

    What I thought I could do:
    - Get something from the market, but whatever i try to search for,
    google does not provide me with what I really want which is a system
    that allows me to locate transmitters in a room.

    The second thing I though of is doing the following:
    - Get 3 radio receivers to form a base for triangulation
    - Get transmitters to send 100 times a second an ID + count
    - Get a circuit that is able to use the data from the 3 bases to
    triangulate the position of the object through a microprocessor or
    something like that

    The problems kinda start now:
    - I do not know of any company that provide that kind of equipment (or
    I am searching for the wrong stuff on google) so if someone can orient
    me in the correct direction in this regard I ll be glad
    - I have pretty much no knowledge of electronics except my classes
    from 10 years ago. I do not mind learning but I do not even know where
    to start, once again any guidance will be appreciated. (I especially
    do not understand how digital data can be sent on analog radio
    frequencies)
    - If you know of any circuits that allows to triangulate the position
    of an RFID (for example) and that can do that for more than 1 I ll
    gladly take the information.

    In the hope someone may help in a way or another,

    Best Regards
     
  2. Phil Allison

    Phil Allison Guest


    ** This is a problem you solve optically - ie with cameras.


    ** That mad idea is a complete non starter.

    ** See above.

    Consider that the speed of radio waves is 1 foot per nanosecond !!

    Location by time of flight is impractical on such a small scale as yours.

    However, as few as two video cameras could locate an object in plan position
    and height above floor ( ie 3D) in a small room.


    .... Phil
     
  3. Guest

    Ok,
    So if I understand this right radio waves moves too fast to measure
    small distances.

    So it could work forslower waves right ?

    As for optical detection, I ll check on google

    Thanks for the input
     
  4. Phil Allison

    Phil Allison Guest


    ** Yep - slow poke EM waves are you saviour pal.

    Find lotsa dem up in the Ozarks - any times ..........



    ** Question:

    We get this SAME fucking IDIOTIC idea posted about three time a year
    here.

    WHY the **** do YOU want to electronically locate mysterious fucking
    objects in some a small room ??

    NO-ONE has ever said why !!!!!!!!!!!

    Is some fucking lunatic prize hanging on doing it ???





    ..... Phil
     
  5. Jasen Betts

    Jasen Betts Guest

    well, differential GPS gets some pretty good performance using radio,
    works best outdoors though.

    GPS hardware is highly specialised, and only cheap because of mass
    production.
    for indoors using ultrasonics with either mobile beacons and fixed
    microphones or the other way round will probably be easier than using
    GPS.
     
  6. You don't need transmitters, you just need a bunch of video or still
    cameras, one centrally located on each wall minimum, or more if needed
    due to field of view etc.
    Then it becomes simply a software and calibration issue. Code for
    image detection in video and still images is readily available.
    And you can use colour filters too if that makes your job easier.

    Unltrasonics is another way, but that can get messy.
    Forget radio transmission, it's too fast, you won't get such a small
    resolution.

    Is this a real practical problem? or some uni project?

    Dave.
     
  7. Guest

    @ Chris Jones:
    Thanks for the info but i did not mean to actually build the whole
    system from scratch either :), but electrofields (have no idea how to
    translate the term in my language and dictionaries ain't helping) and
    me is really not a love story. I tend to dislike physics which is
    mainly why I kinda suck at anything related to waves.

    @Phil Allison:
    If I get my stuff to work I ll be sure to answer why I want to do
    this :)

    @David L.Jones:
    It is not a uni project and since I am working in a bank there is not
    really any direct real link to it. But same with Phil Allison, I ll
    answer why I want to do this either when I get it working or once I
    give up on the hardware part of this project which is the main step
    for me.
    And I would do this as a hobby :)
     
  8. Guest

    Bah, stupid of me not saying what I want to make. Especially since
    giving my need and not the solution would probably get me better
    answers anyway.

    So I want to place for example 2 sensors in said room and follow the
    motion of it.
    But I want it to be wireless (because lines are damn annoying). I want
    the system to be able to operate a number of wireless sensors.
    Also, I am not interested in the position per say, but the motion.

    To go back to technical stuff:
    So after my first post I tried to look at other stuff than radio.
    Ended up on accelerometers and they seem like they can handle the job.
    I don't really care about the position so accelerometers can do the
    motion job just fine and if need be even relate the position though
    with slight errors (rounding issues)
    Yes I know, commercially available for 2000$ for 2 wireless sensors.
    But:
    - Less fun to do :)
    - More expensive than the DIY way
    - Won't learn how to write drivers for PCs
    - Won't learn about how it works generally
    - Won't be as customizable as I might want it to be

    And here is what I am now thinking of building:
    Get for example a set of Accelerometers on own boards. Place them on
    an object lets say a club for example. Connect both sensors to a
    'controller' that also has wireless capabilities on its board. It
    would be something like:
    Sensor ---- wiring ---- Controller + Wireless ----- wiring ---- Sensor
    Then have a wireless base that receive the transmission and send it to
    the CPU through USB for example. Then I treat the data as I want it.

    The issues I have seen so far:
    0/ Is 1m a long distance in regards to cabling. (Some documentation on
    accelerometers tells that Sensor should be near MCU)
    1/ How many Sensors can be controlled by a MCU unit using a SPI
    interface (maybe better ways exists but seems like lots of components
    use it). (And I still don't understand how a MCU can tell which Sensor
    it wants to talk too on the SPI line)
    2/ How can I make the Base receive signals from more than one wireless
    controller + sensor system.
    3/ How can I identify which sensor is the data from
    4/ How do I make the link between a MCU and a Wireless unit (need to
    read docs here I guess)

    Other question:
    1/ Do I need a MCU between the sensors and the Wireless Unit?
    2/ Is it practical to have 1 wireless unit per sensor (I am not for
    this, I d rather aggregate stuff through wiring, less dangerous, less
    radio cluttering and such)

    If you see any other issues, have ideas on how to better that kind of
    system. Know of already build circuits and such (with documentation
    (at least a minimum)) it would be great.

    Best regards,
    Chryzo
     
  9. Phil Allison

    Phil Allison Guest

    <
    ** Halleluiah !!

    At least one fuckhead can see how dumb it is not to describe the
    application.


    ** Oh dear.....

    He is still a complete fuckhead.

    Cos he has chosen NOT to describe what is going on in the room that makes
    the sensors move about nor the purpose of the whole thing.



    ...... Phil
     
  10. Guest

    lol :)

    I won't describe the application whatever happens. I expressed a need
    with a bit of technological requirements, should be enough to get me
    going in the right direction. Though, found some stuff on freescale
    but it does not do exactly what i want :(.

    You do not need to know about the end application to help though :)

    Anyway, to answer my self, a ZSTAR3 system from freescale seems cheep
    enough to get me going though it is full wireless which isn't as good

    Anyway

    Thanks for the help and info :)
     
  11. Guest

    On Jan 7, 8:39 am, wrote:
    Could an ultrasonic car alarm be adapted?

     
  12. Phil Allison

    Phil Allison Guest

    <
    "Phil Allison"
    I won't describe the application whatever happens.


    ** Then you are a TOTALLY STUPID, ARROGANT ****.


    You do not need to know about the end application to help though :)


    ** That is 100% wrong.

    Go drop dead.



    ...... Phil
     
  13. Guest

    I can even give you more info now though. Finally found how to
    translate what i wanted so google could start giving some good
    results.

    I d like to build some wireless 6DoF board sensor with a base than can
    receive inputs from up to 16 board sensors.

    To point me in the right technology / direction, I really do not see
    why you need to know of the end application especially since it is
    plainly a curiosity thing on my part. I ain't gonna resell anything at
    the end. If I am able to get that working I ll just have satisfied my
    curiosity.

    Regards,
     
  14. You can set up ultrasonic receivers, and chirp from the moveable
    object every few ms. If you also flash some kind of infrared LED when
    you chirp, you can use that as a timing reference. The relation
    between the time of the infrared pulse, and the reception of the
    ultrasonic pulse indicates the distance.

    If you have one receiver, you can determine that the transmitter is on
    the surface of a sphere. Two gives you a circle in space, and three
    gives you a point.

    Getting this to work will probably be very difficult.

    Regards,
    Bob Monsen
     
  15. I just read this on Slashdot, perhaps this would be adaptable to your
    needs. We'll have to see if they can actually make it to the
    marketplace.

    "One of my top picks at the Consumer Electronics Show was Sixense's
    TrueMotion, a game-controller technology that resembles the Wii's
    remote, but uses an electromagnetic field to provide far more
    precision — it knows the exact location of the controller in 3D space
    and which way you're pointing it. (The Wiimote only knows which
    direction you're moving the controller.) TrueMotion-based remotes are
    due by Christmas, bundled with a PC game for under $100."

    http://technologizer.com/2009/01/10/truemotions-way-better-than-wii-game-controller/

    -Kevin

    On Jan 8, 10:22 am, wrote:

    (..)
     
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