rain Sensors, was Infra-red Opto help
Russell McMahon email (remove spam text)
> >A raindrop falls from at least 500 meters of height and has
> >a minimum size. I'd use a simple microphone attached to a
> >drum-like structure (with saran wrap skin I think). This may
> >react to other things besides rain.
> Well yeah, if it is actually raining, in a "cats and dogs" sense. But
> when I'm driving my car, the road is wet, and there is misty water landing
> on the wind screen, so there is some precipitation of moisture out of the
> atmosphere. It certainly does not land on the windscreen with enough
> to make any noise.
FWIW - a raindrop has a terminal velocity of a few tens of kilometres per
second. Actual velocity depends on drop size but in free fall is never vast.
I imagine that wind blown drops assume a speed approaching that of the wind
gust they are carried by.
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