LOW COST EXPERIMENTAL DEVICES FOR EDUCATIONAL
SEISMIC NETWORKS
George Hloupis, Ilias Stavrakas, Konstantinos Moutzouris and Dimos Triantis
Department of Electronics, Technological Educational Institute of Athens, Agiou Spyridonos, Egaleo, Athens, Greece
Keywords: Educational Seismology, School Seismic Networks, Sensors, Open Source Platforms.
Abstract: The current paper deals with the use of open source, low cost solutions for the development of educational
seismic networks. The contribution of the current research is the minimization of sensors’ and
accompanying hardware costs through newly implemented devices as well as their coupling to custom and
public available software. Our effort is to deploy plug-n-play devices with initial cost under 10€ in their
basic versions that can be easily operated by school teachers without the need of complicated instructions.
Two solutions based on different microprocessors (with the accompanying software) along with preliminary
guides for inquiring students into seismology are presented.
1 INTRODUCTION
The subset of Information and Communication
Technologies (ICT) that used to design and
implement interactive physical systems by means of
corresponding software and hardware that can sense
and respond to the analogue world is called
“physical computing” (Sullivan, 2004) which is a
subset of regular computing. Supported by the
extensive use of powerful microcontroller units
(MCUs) the idea of using physical computing in
students’ experiments and projects can provide the
learning schemes that are based on the use of
motivation when a student is faced with stimuli.
The societal problems caused by natural hazards
have stimulated the interest of many students
(Brudzinski, 2011). Towards to this direction it
should be teachers’ goal to convert that interest into
problem solving skills. A representative example is
the earthquake, where the threat is ever present, but
a lot of questions raised regarding how and why
earthquakes happen.
Helping students understand the properties of
seismic waves is fundamental to teaching about
earthquakes. An obvious approach is the
visualization through animations on seismic waves
(Braile, 2005; Jones, 2005; Ammon, 2007).
Unfortunately, visualization approaches in
educational seismology present lack of hands-on
experimentation due to complexity of required
instruments. To overcome the above limitations
efforts of providing hardware and software in
schools resulted in several studies oriented to a
dominant educational approach that focus to: a)
present earthquake science and earthquake impacts
in an attractive and exciting way and b) provide
teachers and students with seismic sensors and
software as well as educational modules.
Implementations of the last approach led to several
projects around the world in the forms of seismic
school networks: QCN at USA (Cohran, 2009),
Eduseis at Italy (Cantore, 2003), EduSimso at
France (http://www.edusismo.org/index.asp), School
Seismology at UK (http://www.bgs.ac.uk/schoolseis
mology/), DIAS SIS at Ireland (http://www.iris.edu
/hq/sis).
All the above named projects based on the use of
a simplified seismic station. Traditionally, a seismic
station requires a sensor to record the ground motion
(seismometer), a computer to save the data, a GPS
for accurate timing and location, telemetry or radio
equipment to send the data back to a data collection
center and a power supply unit. While these stations
provide continuous, accurate, reliable data, currently
costs (in the order of tens thousands €) prohibit
installation of this type of seismic stations over a
large number of schools. Solutions that provided
today cost from tens to thousand euros in their basic
versions (SEP 061: 510€, AS-1: 350€, EIA S102:
1100€, Guralp PEPP : 2000€, MotionNode Accel:
100€, O-NAVI B: 80€, JoyWarrior24F: 50€).
356
Hloupis G., Stavrakas I., Moutzouris K. and Triantis D..
LOW COST EXPERIMENTAL DEVICES FOR EDUCATIONAL SEISMIC NETWORKS.
DOI: 10.5220/0003923003560359
In Proceedings of the 4th International Conference on Computer Supported Education (CSEDU-2012), pages 356-359
ISBN: 978-989-8565-06-8
Copyright
c
2012 SCITEPRESS (Science and Technology Publications, Lda.)
In this paper, we describe our proposal for a
seismological experimental device which presents
possibly the lowest initial cost for everyone wants to
involve in educational seismology. Without
compromising in sensitive system’s functions
(sensor performance, adaptability with several
software, expandability) we present an experimental
device which costs 10€. Focus our efforts to the use
of powerful MCUs and the elimination of external
electronic components as well as on the construction
of rigid and adaptive firmware we are able to
provide an educational seismology experimental
device with possible the lowest cost available. In
addition to the basic version of the proposed device
we proved a series of expansion capabilities in order
to transform the experimental device to an
autonomous networked ground motion monitoring
system.
2 DESIGN APPROACH
The overall system configuration is represented in
this section along with brief explanation of each
block’s major characteristics.
The minimum hardware and software
requirements that our prototypes must cover are:
Cost under estimated threshold value (here
under 10€) for basic version;
Ready to operate procedures (along with plug-
n-play specifications) ;
Open Design (use of open source software
and hardware)
2.1 Hardware Description
2.1.1 Sensor
In seismological data acquisition systems two main
categories of sensors used for recording earthquakes:
strong motion and weak motion. This separation is
dictated by the fact that there is no unique type of
sensor that can capture the broad range of
amplitudes and frequencies of seismic waves. Low
amplitude ground motion generated by small local
earthquakes (or by significant earthquakes far away)
can be captured reliable by weak motion sensors.
Unfortunately weak motion sensors are useless for
capturing ground motion from moderate to large
local earthquakes since they saturate. In order to
avoid this type of upper values clipping we used
strong motion sensors. It is obvious that the main
disadvantage of strong motion sensors is that they
are not so sensitive to weak ground vibrations.
For the purposes of school experimental device
we select strong motion sensors in the form of
MEMS (Micro-Electro-Mechanical Systems)
accelerometer. Commercial MEMS accelerometers
today can offer characteristics that enable reliable
earthquake capturing with local magnitude over 3.0.
The sensor block consists of the acceleration sensor
and its necessary passive components. Our selection
was Bosch’s BMA180 MEMS (Micro-Electro-
Mechanical Systems) accelerometer which has the
following major properties:
Digital output which means that we avoid the
use of external A/D converter.
14bit accuracy; thus 1.5mG resolution
Several measuring ranges (from ±1g to ±16g)
Multiple sampling rates (from 10Hz to 200Hz)
Cost under 5€
A prototype of sensor block is depicted in Fig.1.
Figure 1: Sensor block with MEMS accelerometer.
2.1.2 Acquisition – Processing Block
The acquisition–processing block is responsible for:
Gather the binary values from sensor’s digital
output
Transform the values to readable format
Feed the data to the communication port
Control additional activities (such as feeding
the data to Ethernet port, provide in situ
calculations for earthquake alarms e.t.c)
The solution to the above is the use of modern,
low cost MCUs. We concluded in two solutions:
Texas Instruments MSP430 and AVR’s
ATMEGA328. We developed the proposed
experimental device in two versions using each
MCU. This rather controversial approach dictated by
the different characteristics that each MCU presents.
MSP430 is offered to the market as a complete
development board (named “LaunchPad”) for a
price of 4.30$ (including all the necessary electronic
components plus communication and power
regulation unit) ready to host only the sensor. This
was our initial solution which led us to an
experimental device with total cost under 10€. Apart
from the major characteristics which are comparable
with AVR’s ATMEGA328 its main disadvantage is
LOWCOSTEXPERIMENTALDEVICESFOREDUCATIONALSEISMICNETWORKS
357
the lack of maturity since it is a new product and the
support by open source community is not very
widespread.
To overcome the last limitation we slightly
relaxed our cost limits in order to gain the better
results on the subject of expansion simplicity. The
selection of ATMEGA328 MCU provide us an
extremely huge community support which expressed
by the use of programming tools which are suitable
for novice (Arduino, Fritzing, Minibloq e.tc.) as well
as a remarkable range of extensions. The main
disadvantage is the higher price (2.6€/per 25 only for
MCU) which leads to a complete product cost
around 11€.
2.1.3 Communication – Power Block
In order to fulfil the “plug-n-play” requirement we
adopt the use of USB connection for data transfer to
host PC. In the case of MSP430, USB connection is
offered as standard in the LaunchPad board whereas
for ATMEGA328 we developed separately.
Since we focus on cost reduction we selected not
to include independent power supply unit. Instead of
this we used the power lines of USB connection for
producing the 5V and 3.3V supply required for our
circuits. The maximum current for each proposal
was not exceeded 150mA whereas USB can provide
500mA maximum.
Complete prototypes are depicted in Fig.2 and
Fig.3.
Figure 2: Prototype based on MSP430.
Figure 3: Prototype based on ATMEGA328.
2.2 Software Description
The required software for the experimental device
belongs to three categories: firmware, accompanying
software and data exchange.
The firmware is going to be stored in MCU’s
non-volatile memory. It will be public available at
http://research.teiath.gr/edu_tech_en/schoolseis at
the first quarter of 2012. Programming each MCU is
quite straightforward for both MCUs.
The accompanying software suite is a collection
of public available software that fulfils three major
requirements regarding captured data: storage,
visualization and analysis. During system design
special attention received for the subject of data
format. The data streams that generated from the
experimental device selected to follow three
different formats that widely used in seismological
signal processing: ASCII SAC, GSE binary and
ASCII CSV. By using these formats we are able to
use the vast majority of public available (and also
commercial) software for seismological analysis as
well as common data analysis products (MS-Excel,
Visio, Matlab e.t.c).
Data exchange software module is responsible
for the exchange and dissemination of each school
results in order to deploy a seismological school
network. It is scheduled to:
Send the results from each school to a
central database.
Produce the necessary maps to display the
results by means of Google Maps API.
Disseminate each school’s results by using
several web projections (Dynamic web
pages, Twitter, Facebook, Pachube)
3 SYSTEM OPERATION AND
EXPANDABILITY
The operation of the system is straightforward.
Users initially plug in the experimental device in an
available USB port. Before running the software for
the first time, users must execute a preliminary script
which is going to write the appropriate values to the
configuration files (i.e which USB port is connected,
synchronize PC clock with NTP, definition of
geographic location by using IP geolocation
services). The next step is to calibrate the sensor.
Users will receive instructions of appropriate
mounting and levelling of the sensor. Upon sensor’s
start-up the firmware runs a series of calibration
tests in order to ensure that the sensor is adequate
installed (i.e X-Y components are in horizontal
plane and Z is in vertical, the noise level is below a
predefined threshold e.t.c). In opposite case, an
informational message window pops-up. After the
initial calibration users are ready to start the
CSEDU2012-4thInternationalConferenceonComputerSupportedEducation
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accompanying and the data exchange software.
Both proposed systems designed having always
in mind future expansions and upgrades. We have
successfully tested (and developed the
corresponding firmware) a number of additional
hardware modules that add flexibility to the whole
system. Those are:
Ethernet module which adds network feature.
Secure Digital (SD) card module.
GPS module.
4 DIDACTIC UNIT EXAMPLE
The proposed experimental device can be easily
imported to an environmental oriented class course.
Following an inquiry based approach students can
experiment using their educational seismograph as
proposed in Table 1 (Kafka et al, 2010).
Table 1: Structure of an inquiry based exercise.
Aspects of the
scientific process
Example Exercise Tasks
Inquire Install Seismograph
Explore
What signals captured by our
seismograph
Investigate
What signals recorded by other
seismographs around the world
– Seismic waves
Apply Detect local earthquakes
Learn
Estimate earthquake’s
epicentre, magnitude – Hazard
correlation
Communicate
Exchange data and results with
other schools
Apart from being a standalone experimental
device, the proposed structure can be successfully
used for active classroom activities. Under this
approach students engaged to physically participate
in learning activities. A proposal is to explore the
nature and the properties of earthquakes. By letting
the students to jump individually or by groups in
specific distances from sensor, the teacher can
present a set of inquiry questions such as the
representative ones below:
Is there a difference between a student’s and a
group of students’ jump?
What happened when student jumps near the
sensor?
Is there a difference between jumping over
floor and over carpets that cover the floor?
Can the students identify from the recordings
when they start jumping?
5 CONCLUSIONS
The current study introduces a set of low cost
educational seismological experimental devices with
initial cost under 10€. It is oriented for standalone as
well as networked operation implemented in this
way the base of an educational seismic network. The
complete design offered as open source hardware.
Coupled with the proposed devices, a set of public
available software tested and verified for concurrent
operation. The proposed system can easily be
adapted to curriculum including hands-on
experiments providing in this way the core for
various inquiry-based activities. Expansion of the
proposed devices is possible by adding GPS,
network capability and SD recording function
leading to complete amateur seismological station.
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Ammon, C. J., & Lay, T., 2007. Animating the Seismic
Wavefield with USArray. Retrieved from http://eqseis.
geosc.psu.edu/~cammon/QA/Ammon-Lay-GSAToday
.pdf
Braile, L. W., 2005. Seismic Wave Demonstrations Using
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Brudzinski, M. R., 2011. Episodic Tremor and Slip:
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