Hi again Herbert,

BTW, what did you end up doing for the wind vane?

I have a crude idea for a pressure sensor. It's mainly just an interesting
idea to try, and wouldn't be a reliable long term sensor. What about taking
a small (maybe 1 cm by 4 cm) piece of paper, drawing a heavy pencil line on
it, with large "dots" at each end. Now, blow up a small rubber balloon. Use
double-sided tape to attach the paper to the surface of the balloon. Then,
take two small strips of aluminum foil, and use single sided tape to attach
them to the dots at the ends of the pencil line, and cover over the whole
piece of paper with tape to prevent water from getting to it.

If you make electrical contact to the strips, you should have a variable
resistor whose resistance is proportional to air pressure (less air
pressure makes the balloon expand, which reduces surface curvature, which
shortens the pencil line). If you fed the resistor with an accurate
constant current source, you could use an ADC to just measure the voltage
across it.

Sean



At 03:31 PM 3/4/01 -0500, Herbert Graf wrote:
>         As some of you might remember I recently added a wind vane to my
> house
>monitoring system and now I've gotten the weather bug! I have a temperature
>sensor but now I want to get a humidity and pressure sensor (any other
>weather variables come to anybody's minds?). Anyone have any ideas on where
>to get these CHEAP? Or even to build them? I have some ideas on building a
>humidity sensor but not much on a pressure sensor. It doesn't need to be
>calibrated, knowing that one day was more humid than another is good enough
>for me. Thanks on any leads. TTYL
>
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