Weather station is interesting project to build. First of all you can collect lots of interesting data, analyze it and even use for various purposes. Tinkerman wanted to build completely autonomous weather station that would power itself using battery accompanied by renewable energy source like solar panel. As a base he’s chosen Arduino Fio board where he attached XBee module to send data wireless, DHD22 temperature and humidity sensor, and BMP085 barometric pressure sensor.
While working with sensors seems pretty obvious – code is mostly based on ready made libraries. But more challenging task with autonomous devices like this is power profile. Power usage has to be minimized to preserve energy in all corners. As we mentioned, it uses a solar panel which is 6V 2W to charge 3.7V 850mAh Lithium Polymer battery in day time and use it when dark. Sensors like DHT22 require some warming up, transmitting data chews its own amount. But most time station stays in power down mode leaving with ~0.8mA average current drain. With 850mAh battery weather station could last 44 days. Also solar panel fills battery every day – all seems to work fine. It seems that there are few things to add before boxing it and putting in to field.