I like to stop at the Dollar Tree store whenever I get a chance. I look for any new $1
trinkets that wiggle or blink or make noises because that means there may be a motor
or LED or speaker that I can repurpose. This month they had some solar dancing witches
and solar dancing skeletons for halloween. (Maybe there will be solar dancing turkeys,
santas, elves and rabbits as the seasons roll by.) It turns out the dancers make
simple, but effective and cheap, seismometers!
A seismometer is a sensing device that detects movement of the earth's crust. These
movements are often called earthquakes when they are large enough to be felt. Since
there are not a lot of earthquakes you can feel in Georgia, I wanted a seismometer
that could detect even very small movements ("micro-quakes"?).
I use the term "seismometer" for the detector and the term "seismograph" for the
combined detector plus the analyzing/recording software. Some people use the term
"geophone" for the detector as the detector is an "earth microphone". I am not a
geologist so decide for yourself what terms you want to use.
The Halloween seismometer has a magnet suspended at the end of a lever arm that moves
over a coil of wire. The magnet generates a small electrical current in the coil when
it moves. That current is fed into the microphone jack on a computer or digital
recorder. Computer software then analyzes the signal.
I wrote a similar IBL a while back (http://www.instructables.com/id/Build-a-Pendulum-Seismometer-for-under-15/
) and you might get some ideas there on other kinds of
seismometers to build. There are a number of references in the last step of this IBL
that may help you with this project. This might make a good science project if you
live in a seismically active area.
There is a bit of soldering involved in this project but it is otherwise pretty
simple. The cost of the seismometer should be under $5 and the software is free.