Silicon Chip Online - Simple Data-Logging Weather Station, Pt. 1

If you need to record weather data at a remote location, there are very nice professional logging weather stations out there that do the lot, with solar panels for power and ability to record rainfall, temperature, humidity, barometric pressure, wind speed and direction, sunlight hours etc. While it would be nice to have all that capability, I had a need that was a lot simpler. Like many people, I only wanted to record rainfall and temperature. More importantly, I couldn't justify the cost of the professional systems, which typically run to four or five figures. There are plenty of hobbyist weather stations out there too - and at much better prices. They appear very capable but none can log data unattended for an extended period (well, I did find one but even it was well over a thousand dollars). SILICON CHIP has published 'weather' station projects in the past including a PICAXE-based system that recorded temperature and humidity (December 2004). There was also an electronic rain gauge but again, neither project was suitable for unattended remote logging for months at a time. A bit of research convinced me that it wouldn't be too hard to build my own, including a suitable rain sensor. So that's just what I did!

On the electronics side, a low power microcontroller was the way to go. With the right device and a bit of care in design, current consumption has been kept down to an average of around 10mA, meaning a set of three AA batteries should last for years – virtually their shelf life, in fact.

In terms of logging capability, with half-hourly readings, it is capable of storing just under a year’s worth of rainfall and temperature records, utilising the 64 kilobytes of on-board EEPROM memory. The firmware can easily be modified for reading at more frequent intervals. With six minute logging frequency it has over two months capacity. At the other extreme, with hourly recording, it will store almost two years of data.

Here's a close-up view of the data-logging weather station. Top right is the rain gauge, bottom left the temperature measurement while the "works" (shown above) is housed in the lower right container.

The data is accessed through an on-board RS232 interface, enabling easy downloading straight to a laptop or desktop computer. If, like me, you don’t own a laptop there is a simple solution. The controller is cheap and easy enough to build that you can make two and simply swap one out and take it home to dump the data at your leisure.

In fact, the most time-consuming part about the project isn’t the electronics – it’s the hardware. Building the rain sensor will probably take the most time and effort. But if you don’t have the time or inclination, at modest cost you can even solve that little problem too.

While unsuccessfully looking for a suitable commercial weather station, I found a good quality rain sensor for a few hundred dollars that will interface with the weather station. More on this later.