Electronic Design

Volcano Studies Flow Toward Wireless

Tungarahua, a 5016-meter volcano in Ecuador, rumbles while spewing ash and hot gas each day. But when is it going to blow? To get that answer, researchers must rely on wired monitoring systems. Not only are they costly, they also quickly exhaust their batteries, and retrieving the accumulated data requires climbing the volcano's dangerous slopes every few days. So, computer scientists from Harvard University have teamed with seismologists from the University of New Hampshire and the University of North Carolina to develop a network of five tiny, low-power wireless sensor "motes."

These motes could replace the system that's currently used to monitor Tungarahua and other volcanoes. Three of the motes are equipped with a Panasonic BM-034Y microphone that monitors infrasonic (low-frequency acoustic) signals emitted during eruptions. The fourth mote receives data from the other three and forwards it over a serial point-to-point link to the monitoring station more than five miles away. Interfaced with an off-the-shelf Garmin GPS receiver, the fifth mote provides a common time base for the data-collection elements.

Two AA batteries power each of the sensor motes. Also, the sensor motes pack an 8-bit microcontroller, 4 kbytes of memory, and a Chipcon CC1000 radio with a 100-meter range and a 38-kbit/s bit rate in a waterproof package the size of a soap dish. During a field test in July, the network collected 54 hours of data, totaling 1.7 Gbytes of uncompressed log files. Next, the researchers hope to deploy a network of 20 to 50 motes on Tungarahua or on other volcanoes. Larger arrays like this could be used to eliminate sources of noise and triangulate the source of eruption events.

For details, go to www.eecs.harvard.edu.

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