Cheap weather gadgets

Researchers at the department of water management (faculty of Civil Engineering and Geosciences) want to cover Africa with inexpensive weather stations made out of electronic gadgets, such as the Wii.

(Photo: Flickr)
(Photo: Flickr)

Like most people they used to play computer games with it, but now Rolf Hut and Steven Weijs have found another application for their Wii. They use it to measure evaporation and wind speeds. “This device contains three highly sensitive acceleration sensors that are very useful for making all kinds of measuring instruments,” says Weijs. “And the good thing,” adds Hut, while jiggling the Wii in his hands, “is it costs only about forty euros, which is five times less than the devices you can buy in the shop.”
Messing with the Wii is not the core business of Hut and Weijs. Hut is a mathematician working on network analyses, and Weijs develops mathematic models to better regulate artificial lakes for water storage.
In their spare time at the university however both these PhD students experiment with electronic gadgets to help their professor, dr. Nick van der Giesen, achieve his dream of installing small weather stations across Sub Saharan Africa.

“Almost nothing is known about the hydrology on that continent because there are hardly any weather stations,” says Van der Giesen. “Of course there are satellites that observe the earth, but many of them are useless on a cloudy day, and above all, their data are very rough.”
And that’s a shame, the professor says, because it would be possible to increase the crop yields in Africa and expand the agricultural lands if the available water was used more efficiently.
Together with researchers from the International Water Management Institute and Oregon State University, Van der Giesen plans to create a grid with a weather station every thirty kilometers that measures soil humidity, rain fall, evaporation, temperature and wind.

“That would make for some 20 thousand weather stations. We can cope with that. We’ll start by making a prototype over the next two years. It has to be cheap – two hundred dollars at the most - and strong, without any moving parts that can be obstructed by insects or dust. We think this will be possible using all kinds of new, cheap sensors and chips that you can find on the market. After we have the prototype, we’ll look for more financing.”
The next step would be to distribute the stations at schools that are already equipped with XO-laptops, which are also known as the ‘100 dollar laptop’. “School children make wifi networks with these laptops,” says Van der Giesen, “so they could use their networks to assemble the data.”
Back to basics now. How do you change a Wii into a useful weather instrument? “That’s easy,” says Hut. “The trick is to hack the signals that this advanced remote control uses to communicate with the gaming console. Any nerd can do that with a Bluetooth adapter.”

The Wii continually receives infrared signals (pulses) from a signaling device connected to the console, which is usually a bar that must be placed at the top of the screen. The Wii registers the signals with a sensor and uses them to calculate its location in the room. That information is then sent to the console, allowing you to see where you must swing in the air to knock out a virtual adversary or to hit the ball.
“Once you’ve hacked the Wii, instead of aiming the Wii at the console you aim it at something else that emits infrared - like a bobber for example,” Weijs comments.

In an instrument that one of their students developed to measure the evaporation in a lake, the researchers attached the Wii to the side of a floating basin filled with water. They then placed a bobber that emits an infrared signal in the middle of the basin. Due to evaporation, the water level in the basin will drop, as will the bobber. And that’s exactly what the Wii measures and what you can read out.
“Of course, because we made our measurements on a lake, most fluctuations were caused by waves,” Hut explains. “But with smart mathematics we can filter those movements out of the data, because the Wii measures at a rate of hundred times a second. And that for only forty euro!”