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In 2002 I began construction of a low-cost yet highly accurate self-contained weather station
that could be easily deployed. The fundamental design for such a station was for it to be solar
powered; but because it is a low-cost endeavour some very careful design considerations had to
be met in order to conserve energy.
We selected the Atmel 2313 microcontroller as the heart of the system which handles
sensor measurements and calculations, packet encoding and also the charge control circuitry.
This particular microcontroller was selected partly because I had more experience with these
devices as opposed to PICs or other micro's, and also to meet the ultra-low power requirements
of this design. Plus, they accomodate every feature requirement we had for the station micro
at a very low cost.
The chip spends most of it's time in idle mode, consuming less than 2uA of current. It
periodically wakes up in order to take samples from the sensors, checks battery levels and
transmits the data before it goes back to sleep. The standard sensor interval is one minute,
which means that we will have a very precise dataset from each location once deployed. The
device supports a multitude of sensors, including temperature, humidity, barometric pressure,
wind direction, wind speed and rainfall.
Most of the sensors are also in development mode in parallel with the station. Since some sensors
are actually quite complicated, we have spent a great deal of time designing devices to work
with the stations without degrading their performance. We have developed innovative solutions to
allow the sensors to operate with great accuracy while consuming only a minute amount of power.
This of course is a work in progress but we are nearing the end of the design phase
and are gearing up towards installing our first prototype station soon. The prototype
is all but complete at this point, yet there will undoubtedly be many design improvements as
time goes on which of course will be documented here.
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