08-09-2014, 12:17 PM
Embedded system for Hazardous Gas detection and Alerting
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ABSTRACT
Safety plays a major role in today’s world and it is necessary that good safety systems are to be
implemented in places of education and work. This work modifies the existing safety model installed in
industries and this system also be used in homes and offices. The main objective of the work is designing
microcontroller based toxic gas detecting and alerting system. The hazardous gases like LPG and
propane were sensed and displayed each and every second in the LCD display. If these gases exceed the
normal level then an alarm is generated immediately and also an alert message (SMS) is sent to the
authorized person through the GSM. The advantage of this automated detection and alerting system
over the manual method is that it offers quick response time and accurate detection of an emergency and
in turn leading faster diffusion of the critical situation.
INTRODUCTION
The increase in the development of technology and the human race, we failed to take care about
the surroundings in which we live in. Thus we polluted the environment and thereby reducing
the quality of the place we live. Even though there are several aspects of pollution such as soil,
air and water pollution, out of these air pollution acts as the serious aspect as the other can
detected visually and by taste, but the polluted air cannot be detected as it can be odorless,
tasteless and colorless. Hence there is a growing demand for the environmental pollution
monitoring and control systems. In the view of the ever-increasing pollution sources with toxic
chemicals, these systems should have the facilities to detect and quantify the sources rapidly.
Toxic gases are one that causes serious health impacts, but are also used in industries in large
quantities. These gases have to be monitored; such that increase in the normal level of them
could be known and proper precaution measures can be taken. But the current systems
available are not so portable and are costly and difficult to implement. So an embedded system
is designed using PIC 16F877 Microcontroller, for the purpose of detection of hazardous gas
leakage, which in turn avoids the endangering of human lives. The hazardous gases like LPG
and propane were considered here. If these hazardous gases level exceeds normal level that is
LPG>1000ppm or Propane>10000ppm then an alarm is generated immediately, and a SMS is
sent to the authorized user as an alert message, which leads to faster diffusion of emergency
situation. The system is affordable and can be easily implement in the chemical industries and
in residential area which is surrounded by the chemical industries or plants, to avoid
endangering of human lives
Related work
In the year of 2008, LIU zhen-ya, WANG Zhen-dong and CHEN Rong, “Intelligent Residential
Security Alarm and Remote Control System Based On Single Chip Computer”, the paper
focuses on, Intelligent residential burglar alarm, emergency alarm, fire alarm, toxic gas leakage
remote automatic sound alarm and remote control system, which is based on 89c51 single chip
computer. The system can perform an automatic alarm, which calls the police hotline number
automatically. It can also be a voice alarm and shows alarm occurred address. This intelligent
security system can be used control the electrical power remotely through telephone [8].
In the year of 2008, Chen Peijiang and Jiang Xuehhua, “Design and implementation of Remote
Monitoring System Based on GSM”, this paper focuses on the wireless monitoring system,
because the wireless remote monitoring system has more and more application, a remote
monitoring system based on SMS through GSM. Based on the overall architecture of the
system, the hardware and software architecture of the system is designed. In this system, the
remote signal is transmitted through GSM network. The system includes two parts which are
the monitoring centre and the remote monitoring station. The monitoring centre consists of a
computer and a TC35 communication module for GSM. The computer and the TC35 are
connected by RS232. The remote monitoring station consist of a TC35 communication module
for GSM, a MSP430F149 MCU, a display unit, sensors and a data gathering and processing
unit. The software for the monitoring center and the remote monitoring station were designed
using VB [7]
Components of Embedded System
• Hardware specifically built for that application
• An embedded operating system
• User interface like push buttons, LCD, numeric displays
The major part of this project is the hardware model consisting of sufficient sensor with
embedded system. Embedded systems are computer in the widest sense. Based on functionality
and performance requirements, embedded systems can be categorized as, Stand-alone system,
Real time system, Networked information appliances and Mobile devices. Every embedded
system consists of custom-built hardware built around a central processing unit (CPU). This
hardware also contains memory chips onto which the software is loaded. The software residing
on the memory chip is also called as the firmware
AIR QUALITY (AQ)
Air quality is defined as a measure of the condition of air relative to the requirements of one or
more biotic species and/or to any human need or purpose.[1] Air quality indices (AQI) are
numbers used by government agencies to characterize the quality of the air at a given location.
As the AQI increases, an increasingly large percentage of the population is likely to experience
increasingly severe adverse health effects. To compute the AQI requires an air pollutant
concentration from a monitor or model. The function used to convert from air pollutant
concentration to AQI varies by pollutant, and is different in different countries. Air quality
index values are divided into ranges, and each range is assigned a descriptor and a color code.
Standardized public health advisories are associated with each AQI range. An agency might
also encourage members of the public to take public transportation or work from home when
AQI levels are high.
Environmental issues in India
The rapid growing population and economic development is leading to a number of
environmental issues in India because of the uncontrolled growth of urbanization and
industrialization, expansion and massive intensification of agriculture, and the destruction of
forests. Major environmental issues are forest and agricultural degradation of land, resource
depletion (water, mineral, forest, sand, rocks etc.), environmental degradation, public health,
loss of biodiversity, loss of resilience in ecosystems, livelihood security for the poor. Road dust
due to vehicles also contributing up to 33% of an air pollution. In cities like Bangalore, around
50% of children suffer from asthma and also it causes a significant risk factor for multiple
health conditions including respiratory infections, heart disease, and lung cancer,
according to the WHO. One of the biggest causes of air pollution in India is from the
transport system. Hundreds of millions of old diesel engines are continuously burning away
diesel which has the range between 150 to 190 times the amounts of sulphur than the European
diesel has
HARDWARE SYSTEM DESIGN
Block Diagram Of The Proposed System
The gas levels are sensed through the respective gas sensors (here MQ-2 and MQ-7 are
used for sensing LPG and propane respectively for demonstration purpose) and sent to the PIC
micro controller. The sensed analog signals are converted to digital through ADC (inbuilt in
case of PIC). The sensed gas levels are displayed in the LCD; if any one gas level exceeds the
set point then an alarm is generated immediately. At the same time an alert message is sent as
SMS to the authorized user through the GSM modem. The block diagram of the proposed
system is shown in figure3
GAS SENSORS
Normally a gas sensor is the one which is made up of transducer that senses the gas molecules.
It sends electrical signals as the output which is proportional to the gas concentration. The gas
sensors do not sense a particular gas, thus they must tend to employ analytical techniques to
adopt to identify a particular gas. However these analytical methods suffer from many
disadvantages of skilled operator, specially designed PC’s and slows response time etc., and the
proposed system does not suffer such disadvantages. The proposed system is an automated one,
but it requires to reset after every critical situation.
LPG sensor
It is an ideal sensor to detect the presence of a dangerous LPG leak in our home or in a service
station, storage tank environment and even in vehicle which uses LPG gas as its fuel. This unit
can be easily incorporated into an alarm circuit/unit, to sound an alarm or provide a visual
indication of the LPG concentration. The sensor has excellent sensitivity combined with a
quick response time. When the target combustible gas exist, the sensor’s conductivity is higher
along with the gas concentration rising.
Combustible Gas sensor
Sensitive material of MQ-2 gas sensor is SnO2, with lower conductivity in clean air. When the
target combustible gases exist, the sensor’s conductivity is higher along the gas concentration
increasing. A simple electronic circuit is used to convert the change of conductivity to its
corresponding output signal of gas concentration. MQ-2 gas sensor is shown in figure5, which
has sensitivity to propane, butane and also to natural gas. The sensor could be used to detect
different combustible gas, especially Methane and it is a low cost sensor and suitable for
different applications.
PIC Microcontroller
The Microcontroller used here is the PIC16F877. It has attractive features and they are suitable
for a wide range of application. It consists of I/O ports, 3 timers, ROM, RAM, Flash memory
and inbuilt ADC. PIC channel 10 bit inbuilt ADC which convert the analog value into 10 bit
digital data. PIC is programmed to convert 10 bit data into an 8 bit data and to transmit the data
into a transistor driver. Microcontroller 16F877A has 40 pins, 32 pins for parallel port. One port
includes 8 pins, so 32 pins formed 4 parallel ports; each of them is recognized as port 0, port 1,
port 2 and port 3. Number of each pin of parallel port starts from 0 through 7, first pin of port 0
is named P0.0 and the last pin of port 3 is named P3.7.
Software Development
Application development on desktop computers is called native development as development
and execution are done on the same hardware platform. Embedded software cannot be
developed directly on the embedded system. Embedded software development is done in two
stages. Initially, the software is developed on a desktop computer or a workstation. This is
called the host system. Subsequently, the software is transferred to the actual embedded
hardware called the target system. The host and the target system can be connected through a
serial interface such as RS232 or through Ethernet. The processors of the host and the target
system are generally different. Hence, this development is known as cross-platform
development. The embedded software can be transferred to the target system by programming
an EEPROM or Flash memory using a programmer, or downloading through a communication
interface or JTAG port. There are several different ways of writing code for embedded systems
depending on the complexity of the system and the amount of time and the money that can be
spent. Many ready built designs provide libraries and additional software support which
dramatically cut the development time. Fig 8 shows the software cross-platform development.
Cross Compilation
A compiler is mainly to translate program written in some human readable language into an
equivalent set of opcodes for a particular processor. Each processor has its own unique machine
language, and then we need to choose a compiler that is capable of producing programs for the
specific target processor. In the embedded system, this compiler almost always runs on the host
computer. It simply does not make sense to execute the compiler on the embedded system
itself. A compiler that runs on one computer platform and produces code for another is called as
cross compiler. The use of a cross compiler is one of the defining features of embedded
software development, and these tools support an impressive set of host-target combinations.
Toll chain for building the embedded software is shown in fig 9.
CONCLUSION
An embedded system for hazardous gas detection has been implemented; here only two gases
(LPG and Propane) have been detected for demo purpose. The gas sensors and the critical level
of the respective gas should be known, and then this system can be implemented for detecting
various gases either in domestic area such as places of educational institutions, residential and
industrial areas which avoids endangering of human lives. This system provides quick response
rate and the diffusion of the critical situation can be made faster than the manual methods.