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Thread: obstacle avoidance module

  1. #1

    Default obstacle avoidance module

    how do i make a ckt for obstacle avoidance

  2. #2
    Administrator T-1000 rao's Avatar
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    The basic principle behind obstacle avoidance is reflection... you get your IR or ultrasonic soundwaves reflected from the obstacle to your reciever and hence detect and possibly avoid the obstacle..

    Both sound and Light are as such too weak and divergent to travel a respectable distance and get reflected back carrying a detectable intensity.. to over come this problem.. you increase the power and modulate the sound or light.. the general frequency range lying between 30khz to 40khz...

    You can use simple IR for starters.. you can modulate your IR beam to 38Khz.. that giives range and immunity from wide dispersion.. then Use TSOP1738 as a reciever.. keep the reciever right next to the IR LED facing the same direction as the LED.. so when IR radiation is reflected from the object in front.. the reflected wave hits your reciever and the delay between transmission and recieving can be the measure of distance...

    Similarly, you can use piezo speakers and transducers for Ultrasonic obstacle avoidance... you can modulate sound in ultrasonic freq i.e around 40 Khz and throw it.. sound overcomes the dark body limitation of light and hence turns out to be a better means of range finding..

    hope this helps..

    Rao

  3. #3
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    the reflected wave hits your reciever and the delay between transmission and recieving can be the measure of distance...
    Its not easy to measure time taken by light to reflect back. Say ur uC is clocked at 16Mhz. so the least measureable unit of time is 1/16000000 s. in that time light can travel upto 18.75 meters. so the accuracy is plus or minus 18.75 meters !!

    this could be done using some analog arrangement, never tried though.

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    Administrator T-1000 rao's Avatar
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    compare the waveform's frequency and when you get an exact replica of the transmitted wave ( you gotta tune your circuit for that).. thats when you measure delay. and believe me.. that takes time.. or else rangefinding wouldnt have been there,,,

    Rao

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    hi Rao,
    U have proposed the use of piezo speakers and transducers for constructing the ultrasonic range finding module. Can u elaborate on it. Or could u point to some other reference which explains how this can be done.
    Thanks in advance,

    With Warm Regds,
    Cheenu.
    An ounce of application is worth a ton of abstraction -- Booker's Law

  6. #6

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    For a beginner, the best way to implement obstacle avoidance is to use bump sensor (switch) to detect whether the robot has collided into obstacle or not. It's the simple method with checking whether switch is on or off.

    subot.robot

  7. #7
    Senior Member Cyborg
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    I imported a SRF-04 SONAR rangefinder by Devantech ... has given me very satisfactory performance.

    Till now the discussion in this thread has been only on obstacle detection ... not on avoidance as asked by 'bagi' ...
    Sumandeep Banerjee
    M.Tech, IIT Kharagpur,
    B.Tech, IIT Kharagpur,
    http://www.robotix.in

  8. #8
    Administrator T-1000 rao's Avatar
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    How does an ultrasonic system work?? when the diaphragm of the reciever recieves the ultrasonic frequency, the piezo crystals are so configured so as to experience enough pressure at a fixed frequency to generate a detectable signal which is further amplified and used (synthesized or compared )... a peizo speaker or tweeter are capable of creating ultrasonic sounds.. as most other beepers (e.g your computer beeper) are not..

    Hence the detector circuit is formed out of the speaker and transducer..

    Correct me if I am wrong..

    Rao

  9. #9
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    Hi Rao,
    Ur explanation seems to be satisfactory. But u havent mentioned about any circuit to do that. Have u done this before? If yes can u post the circuit diagram? If no, where did u get the idea from? any site or book?. It would be useful if u mention the source.
    Getting a ultrasonic module and making it to work would be easy. But the problem is inavailability. So we will have to work out some solutions so that we wil develop these devices ourselves. Thats the point. Afteralll this site is for indians to get into robotics.

    Thanks,
    with regds,
    Cheenu.
    An ounce of application is worth a ton of abstraction -- Booker's Law

  10. #10

    Default obstacle avoidance

    well a very simple way would be to keep 2 piano wires as described in this link
    http://beamindia.solarbotics.net/firesensors.htm
    now if want to use IR sensors use the 555 timer & IR emitter module to generate pulses of around 38khz. the reflected rays r made to fall on an IR sensor linked o any amp amp for amplification of signals & the output fed to the microcontroller.
    u can find a tutorial in
    gorobotics.net

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