2 Part RADAR / UltraSonic / LIDAR system

Discussion in 'Wireless & RF Design' started by Brent1798, Jul 1, 2018.

  1. Brent1798

    Thread Starter New Member

    Jun 5, 2018
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    I definitely don't have enough experience with rf design to get anywhere near what I need so I'm here asking Y'all once again. What I need to build is a system that sends out a radio signal from device one and starts a stopwatch. When that signal is received by device two, it sends a complementary signal back to device one that when received stops the stopwatch. This way I can use time-of-flight analysis to determine the distance between the two devices. I can't use LIDAR because the line of sight is not guaranteed, and I haven't found an ultrasonic system that can handle the distance requirement (150m). I do comprehend that the MCU would need at least a 1ghz to get within a foot of accuracy which is all I need. But if anyone could even recommend an MCU or system that could meet that I can probably work out the rest. THANK YOU ALL SO MUCH!!
     
  2. jpanhalt

    Expert

    Jan 18, 2008
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    Without line of sight, have you considered the effect of multipaths on your results? What accuracy do you need?
     
  3. Brent1798

    Thread Starter New Member

    Jun 5, 2018
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    The line of sight isn't guaranteed only a vertical level. The system is underground shooting through a straight pipe but that pipe can have several degrees of rise that a laser wouldn't go through but an rf easily would. All that considered I don't think multiple signals will be much to contend with. and as for accuracy just down to the foot.
     
  4. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    What's at the other end?....device 2? Are you putting device 2 at same end? Diameter of pipe? Can you explain the WHOLE situation? So many unanswered questions.

    What exactly are you doing?
     
    williswang likes this.
  5. Brent1798

    Thread Starter New Member

    Jun 5, 2018
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    Apologize, Device 1 is stationary on a tripod at the front of the pipe and a little robot (device 2) drives down the pipe to explore if for cracks fissures. I need to know how far the robot is from the other device. Elevation could change and a possible 45* turn here and there. Hence why LIDAR wouldn't work and it's too far for a sonic version. The pipe diameter can change drastically from 6" to 32" or greater.
     
  6. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    Can you attach a scaled tether?
     
  7. Brent1798

    Thread Starter New Member

    Jun 5, 2018
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    What do you mean "a scaled tether"?
     
  8. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    A string with feet marked off. It would spool out from device 1. Or if device 2 is wire powered.....mark length marks on power cable.
     
  9. Brent1798

    Thread Starter New Member

    Jun 5, 2018
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    Oh! Yes that's how the old tech did it, and while it's efficient, it can cause the robot to slip when the string gets too heavy, and who knows maybe when its all said and done I'll go back to that, but for now I want to explore and create an rf based distance sensor.
     
  10. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    Fishing line wouldn't wick pipe contents and cause much drag. But harder to mark.
     
  11. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    You could use rotation of spool for length.....save you from marking tether.
     
  12. PhilTilson

    Well-Known Member

    Nov 29, 2009
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    Had you considered putting a transmitter on the 'cart' which sends a (coded) pulse for every revolution of its wheels back to device 1? Just count the pulses, do the sums and you have your distance. That way, multipath reflections should be irrelevant, you don't have to worry about timing problems or very high speed MCUs and you don't have to get out your ball of string and black marker!
     
    olphart likes this.
  13. olphart

    Active Member

    Sep 22, 2012
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    I like PhilTilson's concept, but will offer a different method.
    A periodic "chirp" of current position based on adding / subtracting the wheel pulses.
    Slippage may require a separate encoder wheel or multiple wheel sensors.
     
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