NEW
POLE MICRO TO COME
If
I had I buried more wire when I first built
the weather station, I wouldn’t have to add
another microcontroller at the weather station’s
pole now. The cables for the resolver in the
weather vane could have run the 75' to the house
and the microcontroller could have done the
polling. It may be busy enough at the moment
and unable to meet the 10-ms sampling time.
I haven’t looked into that because it hasn’t
been an issue. There isn’t enough wire. So,
another microcontroller will replace the junction
box on the pole (see Figure 3 and Photo 5).
It will gather the data at the pole and pass
it to the microcontroller in the house.
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(Click
here to enlarge)
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Figure
3—The MC68HC11E1CFN2 microcontroller’s ADC
works much better with an external reference
like the REF-02. The RH signal is buffered
with a unity gain op-amp. An AD2S99 generates
resolver excitation signals. The AD2S90
performs the conversion from resolver signals
to digital. |
|
(Click
here to enlarge)
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Photo
5—The venerable HC11 Rulz board that we
use at the Northern Alberta Institute of
Technology pulls weather station duty. The
small PLCC sockets hold the Analog Devices
parts. There is space left to add some circuitry
in the future. A short ribbon cable connects
to a daughterboard to handle signal collection
and distribution. |
The
new microcontroller will be installed in an
aluminum box, which I’ll make as weatherproof
as possible. Cables will enter the box via holes
facing the ground with little clearance so I
can minimize the amount of condensation in the
box. I’ll use military-style connectors at the
end of the cables going into the anemometer
and the weather vane. I’ll weatherproof the
connectors with a section of plastic pipe.
After
the initial testing, all of the data from the
pole microcontroller will be passed to the house
microcontroller via an RS-232 link. For now,
however, the weather vane and RH data will go
to the house as a DC signal (as was done initially).
Initially, the anemometer and rain gauge pulses
will be fed to the house microcontroller. The
pole microcontroller will handle this later.
