Help - Motion Detector

Discussion in 'The Projects Forum' started by partyzan, Apr 10, 2008.

  1. partyzan

    Thread Starter New Member

    Apr 10, 2008
    1
    0
    Hello,
    I want to build a motion detector. I'm not sure where to start or how to go about such a thing. Basically I want a board that incorporates a cheap motion detector that can output to a common interface linkable to a Computer and easily captured for analysis. Perhaps someone can suggest where I can start, and or pitfalls of my project. Maybe something already exist as a kit and I can simply purchase the parts - however the key aspect is that I want to be able to analyze data and not just on/off states in a field. I dont even know if you can purchase a part that gives you a spectrum view. So I guess I'm asking for
    two things:

    [1] Availability of a sensor with spectrum output

    [2] Direction

    Thanks )
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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  3. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    Hello,

    Your requirement is quite common and can be a rather expensive product. You need to be clear about performance expectations and what application you intend for it.

    High end units meant for animation go for thousands, just to give you a rough idea. Traditional motion detectors use pyroelectric sensors in a balanced arrangement to detect changes in infrared light.

    The simplest and cheapest way is to use a webcam. Then, I would write code, if you were so inclined, to compare each frame to detect motion. Perhaps someone has already done this task. I remember seeing somewhere a person that made an algorithm that provided a vector output showing the direction and relative magnitude of the motion, but I don't remember where...

    It all boils down to your performance requirements, so the ball is in your court.

    Steve
     
  4. d94jonca

    New Member

    Apr 10, 2008
    1
    0
    I'm also working (struggling :)) on my own board for motion detection. While the standard 2-pixel PIR sensors do not offer spectrum output, it does offer direction (in one dimension).

    I started out with a circuit that i found at:

    http://archilochus.netfirms.com/#anchor553053

    Like you I am interested in an analogue signal that I can process to determine direction, speed, strenght of signal etc so i built the part of the circuit that is highlighted in the attached picture. The signal that comes out of the OP-amp at 1 is nice and strong and I just feed it into the A/D-input of a PIC-processor. I then make the PIC-processor analyze the signal and take the appropriate action (this is where my problem starts. the pic closes a relays but the load causes voltage to fluctuate, which in turn makes the op amp go nuts :), which causes a false reading...) anyway, I imagine you could instead have the PIC-processor send the readings via RS232 or other protocol to a computer.

    Some other links on this topic:

    http://eepn.com/Locator/Products/ArticleID/33099/33099.html

    http://glolab.com/pirparts/infrared.html

    Hopefully this will get you started.
     
  5. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    If you have access to a full-featured version of Matlab with the image processing toolbox and the application creator, then you can probably come up with a neat solution that way. I've done some basic image processing with a webcam and was surprised how easy it was to do, then, I was able to wrap this up with another toolbox that turns it into an exe, i forget what this toolbox was called.

    Steve
     
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