I'm looking for an implementation for detecting when a person walks over given sections of a sidewalk. Digging up and existing sidewalk to install force sensing resistors may not be an economically viable solution, however I would like some help in solving this.
I was also thinking of an EMF detection wire system, similar to those used for vehicle detection on roadways, but to detect people. However, this would be subject to too much external EMF interference due to it's highly-sensitive calibration.
If you are trying to apply this to an existing sidewalk it would seem you're going to be stuck with some sort of proximity detection as opposed to force sensing.
BTW ... The vehicle detectors I have worked with, like the Peeks, sense metal and are thus not suitable for sensing people.
Sensing a non-metallic body would likely be best implemented as either a sense antenna buried next to the sidewalk (assuming that this is practical) or falling back on tried and true technology like sensing when an optical beam is broken by the person walking on the target area. This seems like it would be the simplest and most reliable solution too.
To top it off, you are sure to find lots of optical beam detectors at you local security dealer, hardware store, or Radio Shack.
I'd try approaching your local security contractor and placing the problem at their feet.
Or, you could go to your local security hardware dealer and ask what they might have that would be suitable for localized proximity or motion detection.
Either of these two suggestions would put you in touch with the people most likely to get you the answers you need.
That said, if you just want to develop a new product then you might be able to place small acoustic sensors in the sidewalk (would only need small holes drilled) and listen for footsteps. I suspect that this would actually be reasonably practical to develop if there is not a lot of other noise sources to confuse the sensors. Something like this may already exist as they use something similar around bank vaults (though not as sensitive). Again, talk to your security hardware dealer.
Infrared laser beam? (infrared to keep people from playing with a visible beam)
Simple: Detect a break in the beam across the area of interest.
Complex: Use a *very* narrow laser source on each edge of the sidewalk aimed at a small reflector on the sidewalk surface between the laser source and the *very* narrow detector. The weight of a person walking across the sidewalk would deflect the concrete enough to be detected. Yes, sidewalks do deflect under a person's weight, just not very much ;-)
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