Write some design notes

README.org

@@ -0,0 +1,32 @@
+#+TITLE: Weather Station
+
+The goal of this project is to produce a cheap and reasonably robust
+weather station with low energy usage that can be deployed far from
+any kind of power or network infrastructure.
+
+* Design
+** Infrastructure
+*** Data storage
+	Removable storage device that can be routinely retrieved and
+	swapped out.  An SD card seems to be the best choice.
+
+*** Power supply
+	A pack of rechargable batteries is the simplest solution.
+
+** Metrics
+*** Temperature & Humidity
+	Off-the-shelf temperature and humidity sensor.
+
+*** Insolation
+	Off-the-shelf ambient light sensor.
+
+*** Pressure
+	Off-the-shelf barometer.  [[https://uk.rs-online.com/web/p/pressure-sensor-ics/1361511][DPS310]] seems to fit the bill.
+
+*** Wind speed
+	3D printed cup anemometer using a permanent magnet and a hall
+	effect sensor.
+
+*** Wind direction
+	3D printed wind vane with a permanent magnet on the axis and a
+	angular position sensor.