Instructables has a great project to build an inexpensive air quality sensor that can be embedded into a helium balloon that will change color according to the level of pollutants it detects. A three- or four-foot diameter glowing sphere isn't necessarily a precision scientific instrument, but making information readily available can be useful for raising awareness of a topic.
Operation of the balloon is quite simple. According to the site, "Inside each balloon is a tri-colored LED. This LED reacts to data from an air quality sensor, turning green, yellow or red based on low, average, and high values." And the materials for this project only cost $30 to $40, depending on the sensor that is used. It is a simple project requiring only a small amount of soldering and assembly.
written by Linda Sullivan, August 09, 2010
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