versatile sensor for object detection

Discussion in 'The Projects Forum' started by nerwal, Dec 4, 2010.

  1. nerwal

    Thread Starter New Member

    Sep 18, 2010
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    I'm looking for a portable solution for object presence detection - something that can be set up and taken down easily, without requiring too much setup/calibration each time. Also, it has to work outside in bright sunlight.

    My first idea was a retroreflective sensor - with a reflector on the other side. my experience is that those aren't usually TOO picky about angles.

    Then I thought an IR proximity sensor might work, with a bit of creative programming.

    Both of these are susceptible to interference though.


    Any suggestions?
     
  2. radiohead

    Active Member

    May 28, 2009
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    you can try ultrasonic transducers. Some vehicles have them mounted in the back to warn drivers that they are about to back into another vehicle. What kind of range were you looking for? What's the application?
     
  3. nerwal

    Thread Starter New Member

    Sep 18, 2010
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    Application is a portable race timer for r/c vehicles, with multiple checkpoints.

    So I would use a laser pointer into a phototransistor or similar design, but I am looking for something that wouldn't require too much fiddling around with aiming the Tx at the Rx. [hence the prox. sensor idea]
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    A lap timer type of application, or a measuring speed application?
     
  5. nerwal

    Thread Starter New Member

    Sep 18, 2010
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    Lap timer.
    I'm aiming for something that can be set up on a patch of rocks for an impromptu offroad course. (I'll probably mount the sensors on those flexible mini tripods or something similar.)

    How reliable would modulated IR proximity sensors be in bright sunlight? (Obviously I'll be making sure they're shaded by some sort of cover)
     
  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    If this is for a "break beam" type of sensor, it is fairly straightforward. Pulse the LEDs at 38kHz (since there are IR Receivers and even some transmitter ICs for that frequency), and note when the signal stops. The reason for pulsing is so steady light, such as sunlight can be measured and accounted for, so the transmitter signal (or lack of) is received. Alignment isn't super-critical, a "Ready" LED could light up on the receiver when it is aligned correctly, like a garage door opener's obstacle detector.

    The timing and display part is best done with a microcontroller, this is where it would get complicated.
     
  7. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I used some 'emitter and receiver' type beam break sensors from Banner engineering before at work to count RPM and they worked great. I went to their website to find them for you, but I ran across this which I think might work better.
     
  8. nerwal

    Thread Starter New Member

    Sep 18, 2010
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    Thanks for the suggestions! That Banner sensor looks great, but it's pretty pricey.
    Also, since this is a TR project for school, I don't want to buy too much 'ready to go' solutions that might make my project too easy ;)

    I will probably use something similar though. I was considering one of these (modulated, of course).

    I hope to use a central hub with a microcontroller connected to a PC and multiple (3+) checkpoint sensors. The sensors should be powered through the central hub as well...

    what uC would you suggest? (I was thinking of using an ATmega16A)
     
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