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

        Ahh, I just used a DC motor and read it with an 8bit ADC. I haven't
calibrated it yet (it's been too cold to use the car method) but the 8bit
number I get from the ADC seems pretty close to the actual wind speed. Why I
say this is because every time we have a windy day I have checked the peak
wind and it always is within a few digits of what 8bit number was peak for
the day. Kinda neat, but I'll calibrate it when it warms up.

> 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.

        An interesting idea, unfortunately I have found rubber balloons to not be
that air tight, they usually only last a week or two before they are
noticeably smaller. I think the air actually gets through the thin rubber,
same as how Hydrogen gets out of a rubber balloon very quickly. But it might
give me some ideas. Thanks. TTYL

> 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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