Proximity meter

Discussion in 'General Electronics Chat' started by 9R1NC3, Jan 15, 2010.

  1. 9R1NC3

    Thread Starter New Member

    Jan 15, 2010
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    Hie Friends, i am working on a college project and i am stuck with proximity sensor.

    i need to sense the exact distance <10cm(0-10cm) from my bot to another object(size of golf ball) using R/F......so that by using 3 receivers i can pinpoint its location.....the golf ball sized object can carry a R/F transmitter...


    using sonar didn't work because of the noise(reflections) from other bots and obstacles on the same arena....


    Is there any circuit suitable for my application?????:confused:


    Help me please,,,,,:( my dead line is close :(

    Thanx.
     
  2. Duane P Wetick

    Active Member

    Apr 23, 2009
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    If you mount inductive proximity sensors close together, they will interfere with each other. Each sensor is a little self contained metal detector with a fringing field. Using shielded type detectors will reduce the fringing effects, but sensing distance may be sacrificed.
    See www.BannerEngineering.com for lots of data on this subject. Possibly a capacitive type sensor may work in your application.

    Cheers, DPW [ Everyone's knowledge is in-complete...Albert Einstein]
     
  3. bertus

    Administrator

    Apr 5, 2008
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  4. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    That is a very difficult problem. Are you sure you need to use RF? With what accuracy and precision do you need to measure the distance?

    My gut reaction is that a triangulation system using IR is you best bet. But of course, IR is not RF.

    Can you give a little more detail about what you are trying to do and why? Are you really trying to detect a sphere, or just something the size of a golf ball of any shape? What is it made of, and so forth.

    John
     
  5. 9R1NC3

    Thread Starter New Member

    Jan 15, 2010
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    Here is my problem--- i need to make a bot that sense an object(i got to make the object too) which is 3cmx3cmx3cm(max.), lift it with the bot's arm and place it in the storage basket within the bot.......there is the tricky part, there are other bots trying to do the same, so i got to identify my objects precisely......i lose points if my bot touch other objects placed in the arena and all this, i got to do faster than others.

    Objects are to be made by us and it can contain a circuit in itself.........


    i got a hint that my competitors are trying something with RF rangers.......

    thanx Jpanhalt bertus and Duane P Wetick for ur replies.......
     
  6. jpanhalt

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    Jan 18, 2008
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    If the object can contain a circuit, I would put the an IR transmitter in the object. Code its transmission (like a TV remote) to avoid interference from other contestants, then home in on it. You can use two receivers on your bot to do that. When you get close enough, then you could use one of the Sharp GP2D12/15 sensors to locate distance more accurately, not just direction.

    John
     
  7. 9R1NC3

    Thread Starter New Member

    Jan 15, 2010
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    Thank you John

    Is IR sensor highly directional???
    what could be scan angle of the receiver?
     
  8. jpanhalt

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    Jan 18, 2008
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    IR emitters can be directional. I don't know what you mean by highly directional. In any event, you will not be looking for a narrow beam. I think that would be the wrong approach, because you would have to go through a random search to first find it. The non-directionality will allow you to use relative intensity from two detectors to locate it.

    See these two links: http://users.frii.com/dlc/robotics/projects/botproj.htm
    http://www.dprg.org/projects/1998-08a/index.html

    In the first link, look for 12C508 IR Obstruction Detection. It is about half way down the page. Instead of looking for obstructions, you are looking for signal.

    John
     
  9. 9R1NC3

    Thread Starter New Member

    Jan 15, 2010
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    I am not much familiar with IR......i guess that IR finds the distance calculating the time taken for the echo to reach back to the transmitter...in that case how can i locate the my object randomly placed with similar objects???
    my object must have a particular coding (like u said as in 'TV remotes'), but how come i synchronize the transmitter and receiver to calculate the distance???

    help me plss....i am badly frustrated:confused::confused::confused:
     
  10. jpanhalt

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    Jan 18, 2008
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    That is called time of flight measurement. Yes, it can be used to determine distance using IR, sound, etc. That is not what I was suggesting. Use triangulation. Did you look up the detector I gave a link to? Did you check the other links?

    I recommended using a non-directional or essentially non-directional (i.e., broad dispersion) IR emitter. Then home on it. Look up what homing means. You may want to read about ADF and NDB beacons used for aircraft navigation. However, in this application, I think you are better off using IR instead of RF, assuming certain geometric constraints. No synchronization is needed. If you need to deal with the potential for the object pointing away from your robot, then maybe RF is the way to go, at least to find it. The principle is the same, and in that case your reading about ADF (sense antenna) may be directly applicable.

    Questions about how to do school projects usually begin with a forum member asking the OP what he has done to date. You need to read up on the subject, come up with a proposal, and let us help you work out the details.

    Links:

    http://en.wikipedia.org/wiki/Radio_direction_finder
    http://www.navfltsm.addr.com/ndb-nav-history.htm

    The second link gives the history. I find it particularly interesting. On occasion I have suggested that OP's try an A-N system for line following. I don't think anyone has tried that, and it is needed here.

    John
     
  11. 9R1NC3

    Thread Starter New Member

    Jan 15, 2010
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    Thank you for ur reply John.
    I have gone through the links.....

    So as u have suggested:
    Object(cube 3x3x3cm) contains an IR emitter.
    Bot contains IR ranging sensor and a homing device.



    Thank you once again.........
     
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