siliconchip.com.au Australia’s electronics magazine April 2019 83
SD card space per day. With the added
channel in this version, that increases
to around 38MB per day, or just over
1GB per month.
A simpler approach
If you have a geophone sensor, but
don’t want to build the full Seismo-
graph including the MEMS acceler-
ometer, you could use the small strip-
board circuit presented here with a
bare Arduino Uno (or compatible)
board and our test sketch. This sketch,
named “Geophone_Sensor_Test.ino”,
was written so that we could test our
geophone sensor in isolation.
Fit the stripboard interface to the
Uno board and upload the test sketch.
Open the Serial Plotter at 115,200 baud
and you can view the output of the
sensor in real-time. The vertical scale
is merely the raw ADC data values, in
the range 0-1023.
Mounting
As noted, the geophone sensor we
used is designed for vertical mounting.
Our tests involved placing the sensor
on its flat end on a desk, and we found
that it was quite sensitive like that.
For the best performance in measur-
ing seismic activity, the sensor should
be rigidly attached to the underlying
bedrock (or something else attached to
it, like a concrete foundation). Many
appear to use mechanical mounts such
as bolts, but a good construction ad-
hesive should make a reasonable sub-
stitute. SC
Screen 1: this sample Serial Monitor output is from the
“Arduino_Seismograph_with_Geophone.ino” sketch
immediately after power-up. If you get any error messages,
check your wiring and the SD card.
Screen 3: we are sending the output of the “Geophone_
Sensor_Test.ino” sketch to the Serial Plotter. During this,
the geophone sensor was being held by hand and did not
appear to be moving much. So it really is quite sensitive.Screen 2: the seismograph writes data to the SD card as five-channel WAV files,
which can be loaded with Audacity. Other audio editing software packages may
not be able to handle five channels of audio in one file.