[10DotMatrix] has a budding interest in seismology, so she decided to make her own seismometer out of some easy-to-find materials. Seismometers are prohibitively expensive for hobbyists, but thankfully it’s really easy to build a usable siesmometer out of simple parts. [10DotMatrix]’s seismometer is built around a modified subwoofer, which acts as a transducer for the earth’s vibrations.
The subwoofer is mounted to the bottom of a tripod, which forms the structure of the seismometer. A slinky is stretched between the top of the tripod and a weight that rests on the coil of the subwoofer. Whenever the ground shakes, the slinky and weight vibrate and induce current in the voice coil.
Since these vibrations are usually quite small, the output of the subwoofer needs a bit of amplification. [10DotMatrix] fed the output of the woofer to an AD620 op amp, which amplifies the signal to a measurable level. The amplifier’s output is fed into an Intel Edison board, which samples the voltage and transmits it to a web dashboard for online viewing.
If you’re shaking with excitement about seismic measurements you’ll surely be interested in this similar method which uses a piezo element as the detector.
Nice work, especially the detailed BOM.
One observation is that some cash could be saved on the use of an integrated instrumentation amp, instead building one up out of a quad jellybean cmos op-amp, e.g. tl074 (or tlv2474 would be more suitable for a 5V supply) as in http://en.wikipedia.org/wiki/Instrumentation_amplifier .
http://alabamaquake.com/equipment.html “Amateurs Seismograph Equipment”
My first thought would be those using 6 axis accelerometers as the sensor with all the signal conditioning, A/D all done for you and even have some level of expected accuracy from the datasheet without calibration. That last part is a pain for DIY sensors.
For web connected accelerometers monitoring earthquakes.
Quake Catcher Network
http://qcn.stanford.edu/
This setup is only good for up and down motion. Sideways and rotational motion causes little coil motion cutting lines of force and causing output.
plus the mechanical system he uses isn’t properly damped, so he will not be able to pick up the shape of the seismic wave, just some oscillations.
I usually only comment on builds if I have to say something positive, but in this case I would’t recommend building something like this if one needs a cheap seismo. But maybe I don’t understand the concept and it’s actually quite neat, so feel free to prove me wrong ;)
Ben
No signals shown. resonance frequency might be not low enough.
Usable transducer for tornado detection? Adapted of course…
Opinions?