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775Re: [booksbybibin,www.booksbybibin.tk] Re: Mdulated Infrared Sensors.......Urgent Help needed

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  • Saeed Bin Shakir
    Jan 3, 2007
      Distance Measurement is complex yet interesting techniques. Here are some points
      1. when IR is transmitted, it is reflected by many objects at different distances, so we will have to measure the longest/shortest distance of some obstacles, or we will have to measure the distance from the largest obstacle(who reflects maximum IR wenergy).
      2. ultrasonic devices can measure distance by the time their  wave reflects. ie. We send a wave packet(not continuous waves), and   wait for reception of the same pattern. The distance can be calculated by D = Vs * dt/2 (dt the small time interval and Vs is the average sound velocity taken as constant).
      3. if the Transmitter or the Reflector(obstacle) is moving, Distance can be more accurately measured by Frequency Shift of the ultrasonics.
      4. If the obstacle is artificial, we can make a table of output vs reflected IR/sonic powers by some controlled experiment, fit a suitable curve to the data(interpolate), and then code the function in porgram. (works but under tight controled systems).
      5. IR is not suitable for above three techniques, because its frequency, velocity are very high and energy is very low. however 4th technique may work well.
      If u or some other researcher has worked or uses these techniques in future, please inform me with the results.
      As far as built-in IR distance measuring devices, i think they work on time-delay techniqs but very precisely and may use sort of DSP/VLSI chip. These are larger size(5x5 inch) and not easy to interface with hardware.

      MURALI <mailmurali_robo@...> wrote:
      you WILL get analog o/p from IR SENSOR.. interface the o/p of
      photodiode to ADC and calibrate it sutiably to get the distance..

      go through the posts in robotics india

      thank you

      --- In booksbybibin@ yahoogroups. com, bibin john <njbibin@... > wrote:
      > IR sensor give only digital output. See tsop sensor tsop1738
      > read
      http://www.robotics india.com/ modules.php? name=News& file=article& sid=32&mode= &order=0& thold=0
      http://www.robotics india.com/ modules.php? name=News& file=article& sid=35&mode= &order=0& thold=0
      > you can go for sonar or ultrasonic transducer also
      > Bibin John
      > www.bibinjohn. tk
      > "º´·»-=|Þ®ä†ëëk|=-•._.· º´·»-=|Ågä®wä£|=-(¯` ObsessiVe LoVe"
      <adonisprateek@ ...> wrote:
      > Hello People,
      > I wanted to know how to make modulated distance measuring ir sensors
      that give analog value i.e. some sort of Sharp sensors as they itself
      are quite costly. I need these urgently in my robotics project in
      which I want the distance reading as analog value after modulation. I
      had no idea how modulation could be done in normal Ir sensors. Please
      help me. Please give some circuit diagram or some link.
      > Thank you,
      > Regards,
      > Prateek
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      Saeed bin Shakir

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