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Sonar and IR — Parallax Forums

Sonar and IR

AImanAIman Posts: 531
edited 2006-12-18 20:30 in BASIC Stamp
Question - if a robot is moving VERY VERY slowly, which is better IR or Sonar?

This robot has a two inch wheel and moves at about 7 RPM / 5 feet a minute. It needs to be able to scan from 1 inch away to 15 feet.

Which is better, Sonar or IR and why?
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Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2006-12-18 17:32
    Sonar, because IR doesn't have that range.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-12-18 17:39
    Even within the range of both devices you can’t base the decision on speed alone.· Both IR and Sonar have pros and cons that you need to be aware of.· It’s the differences in these devices that has seen them integrated together recently on more and more robots.· IR is affected by the color and reflectivity of the surface whereas Sonar is affected by the angle and density of the surface.· Using the sensors together would provide the most complete information.· Where one sensor fails or performs poorly, the other may work better.

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    Chris Savage
    Parallax Tech Support
  • AImanAIman Posts: 531
    edited 2006-12-18 17:57
    Thanks for the feed back.

    I am actually looking at using 2 sonar mounted back to back on a servo for 360 vision with IR coming off all 4 sides of the robot. Possibly one or two IR front and back underneath for edge detection.

    By the way, if IR triggers while sonar is running will they two interfer with each other?

    My first reaction is no they won't but I would like to be certain.
  • Tom WalkerTom Walker Posts: 509
    edited 2006-12-18 18:31
    From where in the energy spectrum they function, they will not interfere with each other. But keep in mind that most sonar units suck up a bit of power at the moment that they "fire" (sometimes to the point that it "browns-out" poorly designed circuits), so building your circuit to handle this situation is a necessity.

    FWIW, the timing of send/receives for either of these technologies is such that it would be very rare that they would be happening at the same time...unless you are using different processors (or COGS) to handle them...so this might be a moot point, anyhow.

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    Truly Understand the Fundamentals and the Path will be so much easier...
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-12-18 20:30
    Well, since you’re using a BASIC Stamp and it will only activate one sensor at a time you shouldn’t have to worry about dropout…But no, sound and light do not generally interfere with each other.· Take care.

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    Chris Savage
    Parallax Tech Support
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