On 2/20/2012 2:42 PM, David Duffy (AVD) wrote:
> Has anyone here done much work with proximity sensors?  I am looking to
> trigger an event when someone stands in front of (or walks past) a
> specific area in a retail environment.  The sensing must be done from
> one side only (no beam break methods).
>
> The sensing range would need to be approx 200mm - 1000mm (8" - 40").
> The horizontal detection width would need to be approx 500mm (20") at
> end of the range I guess.  There would be multiple sensors, spaced at
> approx 600mm - 900mm (24" - 36") intervals.
>
> There is nowhere to mount the sensors apart from near the floor or
> *maybe* on the wall higher up.  Ideally the sensors need to stand up to
> a bit of abuse from knocks and maybe a splash from a cleaners mop.
>
> Typical machinery proximity sensors would be easy to mount, but seem to
> be mostly very short range.  Ambient light can change somewhat so shadow
> detection would not be suitable I suspect.
>
> I had thought about ultrasonic "range finders" (as used in robotics) but
> they would probably interact when use this close together.  They also
> wouldn't stand up to the abuse they'd cop being mounted down low.
>
> I think typical PIRs are going to be too coarse, but maybe there are
> better ones than what I've seen so far?
> David...
>
Multiple sensors can be used if you control them all.  Just use time=20
division multiplexing - only one on at a time. For the other=20
requirements, I would look at IR transmitters/receivers.

What is the penalty for false positives?
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.