This is the first in a series of tutorials we will write in the next couple of weeks on the use of the SODAQ board for autonomous, outdoor solar powered sensor stations. 

We use the SODAQ, an Arduino compatible solar powered board (www.sodaq.net) to which we connect a tipping bucket rain sensor.

A tipping bucket rain gauge consists of a funnel that collects and channels the rain into a small seesaw-like container. When this container fills up the seesaw tips and a magnet is moved past a reed switch and the reed contact close momentarily. This corresponds to a certain amount of rainfall. For the rain bucket we use in this tutorial it corresponds to 0.3mm rain.

We use the SODAQ board to register this rainfail and send the information hourly to the Internet.

There are various systems where we can send the data to like:

Weather Underground

After uploading the data it can be displayed in for instance a bar chart.

Step 1: Materials need

Picture of Materials need
We start by collecting the materials that we need:

Solar Panel
Fine Offset Rain Funnel
Waterproof Casing OBO T-100
2 Pipe clamps
Grove screw terminal
Grove Cable
Jubilee clamps

To get the SODAQ board please visit this Kickstarter page.
The GPRSbee, Antenna, Solar Panel and Battery can be bought from SEEEDstudio or for instance in the Netherlands at sunbedded.nl.

In this example we use a 0.5W panel and a 1000mAh battery.  The SODAQ board uses very little power and will be sleeping most of the time. Only when the rainbucket tips it wakes up to record and every hour when it switches on the GPRS module to send the data to the Internet.
Depending on where you are located and the sunshine hours you have, you however may need a bigger panel and or battery. 

We have used the OBO T-100 junction box, which we think is good value for money and has the right size. You can of course use any other waterproof container you have lying around. For durability it is best to use a UV stabilized plastic. The OBO T-100 comes in two varities, the UV stabilized one is a bit more more expensive though.

You can use any tipping bucket like the Davis Rain Collector II but for this tutorial we have chosen for the widely available and cheap sensor produced by the Chinese Manufacturer ' Fine Offset'.  This rain bucket is often sold in a set forming a complete weather station under various brand names like Alecto, Watson, Elecsa, Ambient Weather and Tycon.

You can for instance buy the rainbucket here for less than $10.
Sparkfun sells the rainbucket as part of their Weather Meters set for $69.95.

Because we want to have the lowest possible power consumption we make our system sleep most of the time. When sleeping it draws less than 50 µA. There are only two conditions under which we want the system to be awake:

- when the tipping bucket tips
- once every hour to send data to the Internet

Microcontroller board like the SODAQ can use so called interrupts to be woken from the sleep condition.

The SODAQ has two interrupt lines. One we will use for the Rainbucket (port D3) and other one for the on board Real Time Clock (D2).