Re: detection of rain and close window

[andrew@xxxxxxxxxxxxxxxxxxxx (Andrew Gabriel)]

In article <48snc1huuqn1vtdd019dm7lehapuu6h5i2@xxxxxxx>,
	MFHult@xxxxxxxxxxxxxxxxxxxxx writes:
> A tipping bucket meter is the only commonly used device that I know of that
> "measure[s] quantity of rain in inches". A typical threshold is 0.04" or
> so.

I designed/built a very simple but effective rain sensor some
35 years ago. It consisted of a piece of strip board (Vero board)
with alternate tracks connected, and placed horizonally with the
tracks uppermost, exposed to any rain, which would bridge the
adjacent tracks and form a circuit. A separate circuit monitored
for the bridging of the tracks via a simple 2 transistor amplifier
driving a relay. It gave you a very early warning at the first few
spots of rain, usually before you even noticed it, but no
indication rate of rainfall.

Some further refinement was a slight tilting of the board so rain
would run off, and glueing about 10 resistors across the underside
to provide something like 1W of heat in total which prevented dew
formation and helped dry off the board quickly when the rain
stopped.

The final result worked perfectly for a number of years.
Occasionally I had to clean off the top, although even when birds
crapped on it, it still worked OK except for perhaps an initial
false trigger at the time. (You could solder a few upstanding
wires to the board to stop birds sitting on it.)

--
Andrew Gabriel