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Sensor suggestion

Discussion in 'Robotics & Mechatronics' started by nimasa, May 20, 2016.

  1. nimasa

    nimasa New Member

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    Hello,
    I need your suggestions on choosing appropriate sensor for my project.

    I have some rolling tyres and I need to measure time (and speed) of them while rolling, by sensors. It could be easily done by putting a laser sensor on one side and a LDR on the other side and read and measure the time in which received signal is being cut by rolling tyre. But, it has to be on one side only, so on the other side I don't want to put LDR.
    Considering application requirement as below, what are your recommendations?
    Is it possible to use reflectors on the other side?
    Do I have to use rangefinder sensors?


    Covering distance: 20cm-3m

    resolution (at beam spot): 0.1mm

    short time-of-flight



    Have a look at attachment also.

    Thanks in advance
    Nimasa
     

    Attached Files:

    Last edited: May 20, 2016
  2. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    Can you put a mirror (or a retro-reflective surface) on the far side? This way, all the electronics could be on one side, and only a piece of truck tape on the far side.
     
  3. nimasa

    nimasa New Member

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    Yes, it's possible to use retro-reflective surface or a mirror, but what sensor to use then?
     
  4. dave

    Dave New Member

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  5. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    What is your budget? Are you looking for a ready-made (commercial) solution, or are you a hobbyist that wants to build your own?
     
  6. nimasa

    nimasa New Member

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    I want to build by my own, and budget is not important.
     
  7. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    Cheapest, quickest, most robust way: Get some IR beam break detectors usually found across the bottom of garage doors. I see these at my local "Habitat for Humanity" thrift shop for a couple of $, or you can buy them new as a replacement part... well, maybe you could, since you didn't put in a country when you registered for this web site...

    I have previously posted how to make them work. They come complete with optics that focus into a narrow beam, so they have a range of 10s of meters, even in daylight. They would work fine mounted together facing a retro-reflector. Their beam is likely a bit bigger than you would like. The time resolution might be a bit slow, depending on how fast your tires are moving...

    If you want to roll your own using LEDs and your own optics, you can try using TV IR remote receiver modules as discussed here but you will only be able to detect the instant the beam is broken, not the edge where the beam is re-established after the tire passes.
     
    Last edited: May 21, 2016
  8. nimasa

    nimasa New Member

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    Thanks for your suggestions MikeMI.
    I want to use two set of sensors at a fixed distance from each other, as it could be seen via image of post#1 and also following link: https://dl.dropboxusercontent.com/u/74629435/M.T/2.1-cell-animation.swf

    And as you said, I'm in need of "beam break detector".
    Both your suggestions are based on IR detection and although they are good at long distance and daylight working, but I'm afraid if they are suitable for my application due to IR wavelength (700 nm – 1 mm), compared to laser (180 – 700 nm) . For my application, after getting signal from sensor, on a micro-controller, I measure the time that I have input (signal). And these timings are very important for further calculations.

    regarding your first suggestion, how to put them in one side? same question for your second suggestion. I want sender and emitter in one side. Is using a reflector accurate enough?
     

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