Microcontroller Based Earthquake Detection System for Spontaneous Cut-off of Domestic Utility Lines for Safety Measures

Abstract

Bangladesh is a country with a high frequency of earthquakes. Since the country lies at the junction of three tectonic plates, the intensity of earthquakes felt in this region is moderate. Surprisingly, the number of deaths and financial loss in this region by earthquakes is not due to building crashes or being crushed under homes. Rather, major reasons of losses are due to indirect phenomena such as induction of fear, as well as fire induced from a cracked gas line or faulty electrical transmission line damaged by earthquakes. As a result, a low cost automated microcontroller based system has been designed and implemented using inexpensive locally sourced electronic components, which senses earthquakes and gas leaks via force sensitive resistors and gas sensors respectively. The microcontroller operates a relay and a motor that cuts off electricity and gas supplies respectively during the event of an earthquake, helping to prevent associated potential disasters.

Full text

Microcontroller Based Earthquake Detection System
for Spontaneous Cut-off of Domestic Utility Lines for
Safety Measures
Swapnil Sayan Saha
[1]
, Shekh Md. Mahmudul Islam
[2]
, Anindita Mashsharat
[3]
Department of Electrical & Electronic Engineering, University of Dhaka
Dhaka, Bangladesh
swapnilsayansaha@ieee.org[1], mahmud@du.ac.bd[2], aninditamashsharat@gmail.com[3]
Abstract— Bangladesh is a country with a high frequency of
earthquakes. Since the country lies at the junction of three
tectonic plates, the intensity of earthquakes felt in this region is
moderate. Surprisingly, the number of deaths and financial loss
in this region by earthquakes is not due to building crashes or
being crushed under homes. Rather, major reasons of losses are
due to indirect phenomena such as induction of fear, as well as
fire induced from a cracked gas line or faulty electrical
transmission line damaged by earthquakes. As a result, a low cost
automated microcontroller based system has been designed and
implemented using inexpensive locally sourced electronic
components, which senses earthquakes and gas leaks via force
sensitive resistors and gas sensors respectively. The
microcontroller operates a relay and a motor that cuts off
electricity and gas supplies respectively during the event of an
earthquake, helping to prevent associated potential disasters.
Keywords- Microcontroller, Force Sensitive Resistor, Gas
Sensor, Relay, Servo Motors
I. INTRODUCTION
Intermittent and frequent earthquakes are a common cause
of terror and concern amongst the citizens of Bangladesh. As a
country situated at the intersection of the Indian Plate, the
Eurasian Plate and the Burma Plate, Bangladesh has been
affected by some large earthquakes; some of them had
magnitudes greater than 7.0 on the Richter scale and had
epicenters inside the country [1]. Several major historical
earthquakes that have affected Bangladesh are shown in Table
I.
TABLE I. LIST OF MAJOR HISTORICAL EARTHQUAKES AFFECTING
BANGLADESH (>7.0 MAGNITUDE) [1][2][3]
Date Name Magnitude
(Richter)
Epicentral distance
from Dhaka (in km)
8
th
Jul 1918 Srimangal Earthquake 7.6 150
2
nd
Jul 1930 Dhubri Earthquake 7.1 250
23
rd
Oct 1943 Numaligarh Earthquake 7.2 438
12
th
Sep 1946 Mawlaik Earthquake 8.0 407
15
th
Aug 1950
Assam Earthquake 8.5 -
Earthquakes over the last few years that have affected this
region have stayed within the 4-7 magnitude range, with the
2015 Nepal Earthquakes as exceptions. Figure 1 shows the
magnitudes of earthquakes near Dhaka, Bangladesh that have
affected the fast emerging megacity in the last ten years (2006-
2016).
Figure 1. Scatter plot of Earthquakes affecting Bangladesh in the
last ten years (Data taken from earthquaketrack.com [3]).
The red line in Figure 1 shows the mean earthquake
magnitude to be 4.8 with a slight postive correlation.
News of deaths due to earthquakes caused by being
crushed under homes is quite rare in Bangladesh, thanks to the
epicentrial distances of extremely large earthquakes being
400-800 km away from the capital city. However, other than
injuries and deaths caused by induction of panic, another
subsidiary cause of fatalities might be fire caused by a fissured
gas supply line or short circuits from faulty electricity
transmission lines. Examples of severe destruction of lives and
properties caused by fires from gas lines include fires caused
by the San Franscisco (1906), the Tokyo (1923), The Loma
9th International Conference on Electrical and Computer Engineering
20-22 December, 2016, Dhaka, Bangladesh
978-1-5090-2963-1/16/$31.00 ©2016 IEEE
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Prieta (1989), Northridge (1994) and Kobe (1995) earthquakes
[4]. Since gas and electrical utility lines of Bangladesh
especially are prone to damage due to earthquakes, it is
advisable that these utlity lines should be cut-off during the
interval during which the tremors are felt.
Unfortunately, the natural instinct of humans would be to
take cover or run for their lives rather than doing something
intricate like switching off circuit breakers or turning off gas
valves during emergencies. Hence, this paper presents the
design and implementation of an automated earthquake
detection system that automatically cuts of the discussed two
utlity lines using the AVR family of microcontrollers.
II. LITERATURE REVIEW
Several US patents exist which claim to shut off utility lines
during earthquakes [5] [6]. This system, compared to the
existing systems, uses a microcontroller as the central hub.
Force sensitive resistors tuned to resonate at seismic wave
frequencies have been utilized for vibration detection. The
system also encompasses several modern and convenient
features such as integration with an android application, turning
on emergency lights to guide the user to an emergency
evacuation route and using an attention grabbing alarm.
Compared to existing systems using mechanical means or
relays, this system uses a single high current relay and a servo
motor to turn off the entire domestic gas and electricity supply.
III. MATERIALS AND METHODS
A. Operational Principle
Figure 2. Block diagram of the designed automated earthquake detection
system. The relay and the servo motor are connected to the
electrcity and gas supplies respectively.
As shown in Figure 2, the designed system consists of
primarily five parts. The microcontroller platform controls the
operation of the entire system. The sensor circuitry detects
tremors caused by earthquakes as well as leaks in the gas line.
Once an earthquake is detected, the microcontroller platform
shuts down the electricity supply through a relay and causes the
servo motor attached to the gas line valve to rotate. It also turns
on the emergency lights which illuminates the evacuation path
for the user. The alarm circuitry is also activated
simultaneously.
If no earthquakes are detected but a gas leak is detected by
the gas sensor, then the system shuts down the gas valve only.
The entire operation can be monitored via an android
application, which facilitates remote operation and control of
the system.
Figure 3. Schematic Diagram of the Entire System.
B. The Microcontroller Platform
This system has been designed using the Arduino Mega
microcontroller development platform, which features the
Atmel Atmega 2560 microcontroller. The commercial
prototype should not be built using the Arduino if one wants to
lessen production costs and space [7].
C. The Sensor Circuitry
Two sensors have been utilized in this designed system for
two different purposes.
In this designed system, the MQ-2 gas sensor module has
been utilized. This particular sensor has been chosen due to its
non-exorbitant cost, low power requirements, wide detecting
scope, fast response, high sensitivity and a long life [8], all of
which promotes its use for engineering applications in
Bangladesh. Most vitally, the sensor is well known for its use
in embedded systems in detecting combustible gases [8].
Figure 4 shows the sensitivity curve of this gas sensor [9].
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Figure 4. Typical Sensitivity Characteristics of the MQ-2 Gas Sensor [9].
We are interested in the sensitivity curves of methane, alcohol, carbon
monoxide and smoke in this designed system.
Concentrations of atmospheric methane is 0.722 ppm
[10] and carbon monoxide is 0.2 ppm, which are way beneath
the minimum sensitivity of the sensor as show in Figure 6.
Hence, the sensor would not produce false values due to
atmospheric concentration of these gases.
A force sensitive resistor is a variable resistor whose
resistance decreases with an increase in force applied on the
resistor [7].
In order for the force sensitive resistor to oscillate at
surface wave frequencies of earthquakes, a mass should be
attached to the force sensitive resistor such that the resonant
frequency of oscillation of the resistor matches with the
resonant frequency of the surface waves.
Several factors should be considered in choosing the resonant
frequency of oscillation for the sensor:
• Resonant Frequency of the buildings: As a rule of
thumb, the resonant frequency of civil structures is
found using the following empirical relationship [11]:
1/φ
Β
= 0.1Ν
(1)
where,
φΒ = Resonant frequency of the building
N = Number of stories of the building (1, 2...)
• Seismic Microzonation map of the area: Not all
structures within a given area may have the same
resonant frequency. Thus, seismic microzonation
needs to be applied in order to determine which
structures are at the maximum risk. For this particular
project, the city of Dhaka was chosen as the intended
area. Figure 5 shows the seismic microzonation map
of Dhaka, divided into 4 bands [12].
Figure 5. Seismic Microzonation Map of Dhaka City. Band a is
for structures 2-5 storeys high, Band b is for structures of 6-8
stories high, Band c is for structures 9-14 stories high, Band d is
for structures 15-20 stories high [12].
It is evident from Figure 5 that buildings 9-20 stories high are
at the maximum risk of being affected by earthquakes, whose
resonant frequencies lie in the range of 0.5-1 Hz using eqn. 1.
As a result, the magnitude of the mass that needs to be
attached to the system is given by:
m = k/
(2
π
φ
Β
)
2
(2)
where,
φΒ = Resonant frequency of the building in Hertz
k = Spring constant of the oscillating system
m = mass of the oscillating system
The spring constant of an end-loaded cantilever is given by:
k = Et3w/4l3 (3)
where,
E = Young’s Modulus, which can be found from Figure 6
t = thickness, w = width, l = length of the system [13].
Figure 6. Stress-strain characteristics across two faces of a carbon
filled PDMS sponge, the material typically used for crafting force
sensitive resistors [14].
100
100
0
100
00
ppm
10
Rs/Rb
MQ2
1
H2
LPG
CH4
CO
Alcohol
Smoke
Propene
Air
Q1
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The high amplitude oscillations of the mass-sensor system
causes a force to act on the sensor, which alters its resistance
and thus, voltage output from the sensor increases.
D. The Output Circuitry:
As soon as an earthquake is detected, the microcontroller
activates a relay that cuts off electricity supply. It also sends
pulses to a servo motor attached to the gas valve which rotates
in order to turn a gas valve off, cutting off gas supply. If there
is no earthquake event but a gas leak is detected, then the
microcontroller platform simply turns off the gas supply. The
system also activates a set of emergency alphanumeric
displays that read “E X I T” once an earthquake is triggered to
mark the evacuation route for the user.
E. The Alarm Circuitry:
The alarm circuitry consists of a DC buzzer and an LED to
warn the user of a possible earthquake event through the use
of light and sound.
F. The System State Circuitry:
The system state circuitry consists of the Bluetooth module
and the android application for serial communication. Once an
earthquake is detected, a warning message is displayed on the
android application. However, the application’s role is
prominent when a gas leak is detected and the system turns off
gas supply completely. It displays a message “Gas leak
detected! Please consult a qualified repair personnel” Once the
leak has been fixed by the technician, the user can reactivate
the gas supply by typing in “A” from the application.
IV. IMPLEMENTATION AND COST ANALYSIS
TABLE II. BILL OF MATERIALS FOR PROTOTYPING THE SYSTEM
Feature Quantity
Unit Price
(USD)
Cost
(USD)
Arduino Mega 2560 1 14.74 14.74
MQ-2 Gas Sensor Module 1 12.10 12.10
406 Force Sensitive Resistor 1 11.70 11.70
HC-05 Bluetooth Module Breakout 1 7.13 7.13
4 Channel 5V Relay Module 1 3.59 3.59
Buzzer 1 0.26 0.26
Alphanumeric Displays 4 0.60 2.40
Servo Motor 1 3.90 3.90
Miscellaneous (LED, Light Bulb, Power
Cord, Power supplies)
- - 3.00
TOTAL 58.82
Table II shows that the entire system was built under $60
(all materials were bought from techshopbd.com). A
commercial prototype of this system would cost around
$100-120. Note that, a device that mimics the operation of
the designed system is not available in this country. Seismic
sensors are available on eBay, lacking capabilities to turn off
utility lines and only supporting the detection of earthquakes.
V. RESULTS, CONCLUSION & FUTURE WORK
The designed system was a just a proof of qualitative
concept and was not tested on a large scale during actual
earthquakes. The prototype did manage to detect simulated
earthquake-like tremors with magnitudes of 4.0+.
Several improvements may be brought to this system:
1. A 3 axis accelerometer can replace the FSR for
detection in all planes independent of frequency.
2. 2D Multi-gas mapping techniques with cascading
module system over a wireless sensor network can be
used to monitor the gas leaks at multiple points [15].
3. Pattern recognition algorithms based on positive
decision logic may be integrated into this system [16].
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