> Jack - who grins and bears it because for me, there is no solution.
There are more sophisticated detectors available, that can distinguish
between a tree branch moving in the wind and a person moving, but they are
significantly more expensive (and usually sold for alarm applications, not
I don't know what the "hot setup" is today, but it used to be a combination
of passive IR (which looks for warm bodies moving in the field of view) and
radar (which can judge the size of the moving object). Getting them set up
was kind of tricky, but when properly done, the overall system could tell
the difference between a tree branch (or laundry), a small animal (cats,
squirrels, etc), and a person.
Of course it still wasn't perfect, there is a real gray area between a large
dog and a small child (for example), but much better than the cheap IR
sensors usually found with lights.
There are also the IR beam systems, which detect only something interrupting
the beam. That won't help if your trees drop branches into the area you
want to protect, but you could maybe route the beam around the trees.
Hmm, with compute power & digital cameras being so cheap these days, I
wonder if anyone offers a true imaging system yet, that actually looks for
the shape of a man walking? A quick Google didn't turn up any commercial
products, but there does seem to be a fair amount of research going on. Eg,
Something like this might work well:
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