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Asaduzzaman@wichita.edu ... embedded systems have potential to detect gases and alert people. ... to sense for the people especially when they are less.
A Novel Embedded System for Better Detection of Perilous Gases Abu Asaduzzaman

Muhammad F. Mridha

Kishore K. Chidella

EECS Department Wichita State University Wichita, Kansas, USA [email protected]

CSE Department University of Asia Pacific Dhaka, Bangladesh [email protected]

EECS Department Wichita State University Wichita, Kansas, USA [email protected]

Abstract—Gas leakage is a major problem in industrial sectors, residential premises, and gas-powered vehicles such as compressed natural gas (CNG) cars. The gas detection kits are used to detect the gas leakage at vulnerable places to prevent accidents due to harmful gases. Studies show that modern embedded systems have potential to detect gases and alert people. Various sensors are used (in the embedded systems) to detect various harmful gases. However, most commercially available systems can detect only one gas. The aim of this paper is to introduce an embedded system that can detect various perilous gases and automatically alert about gas leakage in vulnerable premises as needed. The experimental gas leakage system consists of a Carbon Dioxide (CO2) sensor, Carbon Monoxide (CO) sensor, temperature sensor, microcontroller, air conditioner, and a buzzer. The use of temperature sensor is not just confined to detect the temperature but it is used to control the heating ventilation and air conditioning (HVAC) applications inside the residential premises. According to preliminary experiments, the proposed system can detect both CO and CO2 with up to 98% accuracy, control HVAC applications, and alert people in case of a gas leakage. Comparing with two similar contemporary systems, the proposed system offers more and better useful features such as detecting multiple gases, displaying messages, and triggering alarm system. Keywords—Embedded systems, HVAC, gas detection, perilous gases, temperature sensors

I. INTRODUCTION Embedded systems use sensors for automated data collections. Smart sensors may detect signals/disturbance in the environment and may react accordingly. Generally, the sensors are used to give an output in digital format and monitor the change in the course of time [1]. The sensors are generally interfaced with microcontrollers and programmed according to the users’ requirements. Smart sensors are now widely used in automotive applications [2], medical applications, HVAC applications, marine applications, civilian applications, etc. Wireless sensors are usually used in security and communication [3]. Sensors in HVAC applications are used to check and monitor environmental variables like carbon dioxide density, temperature, humidity, etc. Many gases have fewer odors and thus it could be difficult to sense for the people especially when they are less concentrated. Particularly, at these scenarios security systems that can detect the gas leakage are essential to protect the people from harmful gases and thus can avoid gas leakage 978-1-4799-6399-7/14/$31.00 ©2014 IEEE

accidents in prior. Gas sensors have a wide range of applications in automotive industry to detect harmful emission of dangerous gases in the atmosphere and perform necessary actions to minimize the release of the hazardous gases to the environment [4]. In this work, we focus on the usage of special sensors in detecting perilous gases and controlling HVAC applications. The sensors are capable of detecting CO and CO2 in a particular room and check the room temperature. Embedded systems can be developed to automatically activate alarm systems if gas is detected and/or allow cool/hot air to flow in the room if the room is hot/cold [5]. The use of sensors and microprocessors in the HVAC applications may automate the process and reduce the physical burden. If the gas level is more than the referred safe level then the microcontroller sends a signal to a buzzer to be activated and thus the public can be alerted. This paper is organized as follows: Section II summarizes some related published articles. Important hardware and software components used to implement the system are discussed in Section III. Section IV introduces the proposed perilous gas detection system. The proposed system is evaluated in Section V. Finally, this work is concluded in section VI. II. BACKGROUND STUDY There are many published articles in improving security systems due on gas leakage. Some relevant papers are discussed in this section. During the period of 1999-2004, more than 16,447 people died because of CO poisoning in the United States [6]. According to the report of the Centers for Disease Control and Prevention, often people in the age group of 65 years plus are more affected by CO gas. Of the total deaths, 24% is contributed by the age group of more than 65 years and the less affected one are 0-4 year’s age group. During the months of December and January the mortality rate is very high and the months of July and August stand the least [6]. There are few common sources of CO in homes that are released in open air due to fuel-burning devices such as gas or kerosene space heaters, boilers, water heaters, power generators, camp stoves, motor vehicles, and some power tools with internal combustion engines. Finally, smoking is also a major or common source of CO that can affect the air quality or create a polluted environment [7]. An average of 6,800 CO exposures per year is self-reported to Poison Control centers in

2000-2009 [8]. These scenarios lead to the severe death rates and are causing health hazards in large number due to inadequate control of gases. According to the National Fire Protection Association (NFPA), there are 242 CO-related non-fire deaths attributed to heating and cooking equipment in 1991. The leading specific types of equipment were gas-fueled space heaters (69 deaths), gas-fueled furnaces (52 deaths), charcoal grills (36 deaths), gas-fueled ranges (23 deaths), portable kerosene heaters (23 deaths), and wood stoves (13 deaths) [9]. CO2 is released into the atmosphere mainly by the industries. The other human activities that emits CO2 include the combustion of fossil fuels (such as coal, natural gas, and oil) for energy and transportation. Some industrial processes and land-use changes also emit CO2 [10]. CO2 not only puts out fire, but also puts out life. Sensors are introduced to detect gases and improve the sensitivity and selectivity [11]. The study based on the report of International Energy Agency (IEA) explains that there is an increase of 78.1% emission of CO2 inside the marines and due to marines [12]. The recent study has stated that 34 billion tons of CO2 was emitted in the year 2012 alone [13]. As a result, people who are living near the industrial areas have to be more careful because the emission of CO and CO2 is high in these areas. CO2 is also the primary gas involved in the “greenhouse effect,” and therefore may be prevalent in an enclosed, windowed area [14]. The increasing levels of CO2 encourage plant growth, an unusual flowering or blooming of household plants may indicate an overabundance of CO2 [15]. Using a system which detects the level of CO and CO2 constantly should be helpful as the people can be on the safe side and save their lives. The gases which are harmful can be sensed by using sensors. Also, using embedded systems, the information of the harmful gases can be sent to the people as an alert. In an existing system, the detection of CO is considered as the main component to bring the safety in mining industries. The detection system consists of light generation, gas chamber, signal generation and processing section. The detection sensitivity is improved by using fiber optic sensing. Photodetector pin is connected to optical fiber and is coupled with gas chamber that consists of input and output lens. The gas chamber is smooth and they can’t absorb the infrared and so the aluminum alloy material is selected as the gas chamber material. In this system, using Differential Absorption Detector reduces the detection errors caused by the instability of the light source. Using piezoelectric crystal Bragg grating, which releases two harmonic signals, modulates the light wavelength. The primary harmonic is used to control piezoelectricity and the other is precisely locked in center longitudinal mode spectrum and thus detects CO gas with high sensitivity [16]. To monitor the flow of CO2 gas due to forest fire, green house emissions in open air environment, the system uses nondispersive infrared (NDIR) sensor and is interfaced to a node sensor in a wireless sensor network using a communication protocol with low power, while maintaining the trade-off between energy consumption and accuracy. The signals from the sensors are filtered, then amplified and a voltage peak

detector is used to provide accurate readings. The microcontroller (MC9RS08KA8) sends the values collected from sensors to a node sensor and it is interfaced to a sealed tight crystal vessel and thus controlling the CO2 flow. A thermistor in NDIR sensor controls the temperature to improve sensitivity. The active signals after filtering and amplifications are observed in simulation results [17].

Most currently available systems are with single sensors; they are not capable of displaying the alert information, nor controlling the fresh air in building [16-17]. The existing systems are useful to detect the gas but they are not efficient to control the flow of gases. The proposed system is designed on a single-board with multiple sensors to keep the system small and cheap, detect various gases, and help alart people as needed. III. HARDWARE AND SOFTWARE COMPONENTS A. Microcontroller A microcontroller is the heart of the system – processes all computational operations. The microcontroller consists of a powerful central processing unit (CPU), tightly coupled with memory, various input/output interfaces such as serial port, parallel port, timer or counter, interrupt controller, data acquisition interfaces-analog to digital converter, digital to analog converter, integrated on to a single silicon chip. Other components are interfaced with the microcontroller. Dragon-12 plus2 board is used in this work. The board comes with MC9S12DP256CCPV and MC9S12DG256CVPE microcontroller on it. The MC9S12DG256 is a replacement for the MC9S12DP256 because Freescale has discontinued the latter. The only difference between DG256 and DP256 is the number of controller area network (CAN) ports. B. Sensor Sensors are used to read the environment continuously and feed the signals or values to the microcontroller accordingly. The microcontroller processes the data by comparing with the reference values, which are already stored in the memory. A wide variety of sensors are available in the market today. These sensors give analog values that are later converted to digital and send to the microcontroller. A CO2 sensor is such a device that is used to measure the amount of CO2 present in air or in the environment. These sensors measure the amount of gas in parts per million (ppm) or by percentage volume. They are often used in buildings or auditoriums where the inflow of fresh air is low so that the system can maintain indoor air quality [18]. 1) Non-Dispersive Infrared (NDIR) CO2 Sensor One of the most popular sensors that can be used to measure CO2 gas is NDIR. A NDIR CO2 sensor is used in this work. This sensor uses infrared to detect the gas present in the air. The workflow of this sensor is explained below. This type of sensors basically consist of a tube or a chamber in which a source of infrared light is placed at one end and a detector is placed at the other end as shown in Figure 1.

D. Buzzer The buzzer takes the power supply from relay. The microcontroller sends signals to the buzzer as needed. Different frequency can be assigned to the buzzer so that each sensor can be assigned with a different sound. This is done so that the user can understand which sensor is activated and what gas is released into his surrounding area.

Fig. 1. Operations of a NDIR CO2 sensor

The tube is filled with the gas and the source directs the infrared waves of light in the tube filled with gas. The molecules of the CO2 gas absorb light of particular wavelength. An optical filter, which is just placed in front of the detector, absorbs light except the light of wavelength absorbed by CO2 molecules. The difference between the amount of infrared light among the source and the detector is calculated. This difference is directly proportional to the number of carbon dioxide molecules present in the gas. 2) CO Sensor CO sensor is used to detect the presence of carbon monoxide in the vicinity. As CO is a poisonous gas, the usage of these sensors is highly recommended in the places such as chemical laboratories, industrial zones, and coal mines, where the chance of presence of CO is very high [19]. CO displaces oxygen in our blood and it harms us if we are exposed to either high levels of CO in a short period of time or to low levels of CO over a longer period of time. 3) Temperature Sensor Evaluation of temperature is helpful in many technical procedures like assessing the performance of jet engine, smelting of steel, measuring the approach of an experiment, detecting the temperature inside a laboratory, and determining the consequences of global warming. In the experiment, the voltage is read across the diode. When the voltage increases, the temperature also rises. There is a voltage drop between the emitter and base of the transistor, which is recorded. If the voltage difference is amplified, an analog signal is generated. This signal and the temperature are proportional. Even though the technique has improved, this remains the basic working principle of the temperature sensors [19]. C. LCD Screen A liquid crystal display (LCD) is convenient for electronic visual display or video display that uses the light modulating properties of liquid crystals (LCs). LCs does not emit light directly. LCD is used to display the parameters of sensors and temperature that constantly changes. Microcontroller takes care of sending the value to the LCD screen. A general purpose alphanumeric LCD with two lines of 16 characters is used in this work.

E. Relay Relay in this work is a simple switch, which can be operated both electrically and mechanically. A relay consists of an electromagnet and also a set of contacts that are connected. The switching mechanism is carried out with the help of the electromagnet. F. CodeWarrior Development Suite CodeWarrior, a powerful and professional tool from Freescale, is used to write code in embedded C, debug, and develop the applications. IV.

PROPOSED SYSTEM

In the proposed perilous gas detection and HVAC control system, the sensors communicate with the microcontroller and the system alerts people if the harmful gas levels are abnormal. The system also measures the room temperature; if the temperature is higher than a reference value, it turns on A/C system. Figure 2 shows the block diagram of the proposed system. A microcontroller is the centerpiece of the system which is connected to all the three sensors, relays, LCD, etc. Sensors play a very important role by providing the readings as analog signals to the system. Each sensor acts as a transducer. In particular, these transducers are being used as electrical transducers. These electrical transducers convert physical quantities like gas, heat, and pressure into electrical signals. A sensor continuously senses the signals and sends these signals to the microcontroller system. Analog-to-digital converters on the microcontroller system are responsible for converting the analog signals to the equivalent digital values. The microcontroller is used to compare the gas levels of sensor with pre-determined reference values and activates the buzzer if any harmful gas is detected. The values obtained from the sensors are displayed on LCD. Power Supply Buzzer CO Sensor Relays

CO2 Sensor

Microcontroller Air Conditioner

Temperature Sensor

LCD

Fig. 2. Block diagram of the perilous gas detection system

The operations of the proposed system are explained using the flowchart in Figure 3. The values from the sensors are given as input to the microcontroller. The microcontroller compares the sensor values with the reference values, which are already stored into the memory. It should be noted that the complete operational logic is also stored into the microcontroller’s memory. The readings of the sensors are continuously fed into the microcontroller, which in turn compares with the reference values. Whenever the value of any sensor exceeds the reference value, the microcontroller sends a signal to the buzzer. At the same time, the LCD screen should be displayed with a prefixed message explaining which sensor is causing the alarm. The LCD screen also displays the temperature continuously and the microcontroller updates the temperature regularly.

Fig. 3. Operations of the proposed system

The system can be used to detect the toxic gases that may cause serious health issues. These gases need to be monitored regularly so that any increase in any of the gas levels could be known and proper precautionary measures can be taken. V.

EVALUATION

The proposed system is implemented by using Dragon-12 plus2 board. The code is written in CodeWarrior/C. Some important components used to implement the proposed system are summarized in Table I. TABLE I.

Component Microcontroller CO Sensor CO2 Sensor Temperature Sensor LCD Relays Buzzer

COMPONENT SPECIFICATIONS

Specifications MC9S12DP256CCPV MQ-7 MG811 TMP36 LCD-09393 2KA-4A-105 ROB-12567

The microcontroller (MC9S12DP256CCPV) used in this project is low cost, easy to program, flexible to add new functions, and can be reprogrammed with no additional costs. In addition, the power dissipation is less and operating speed is 40 MHz. It supports C/C++ languages, which are very popular languages among programmers. The sensitive material of CO sensor (MQ-7) is SnO2, that have better sensitivity to natural/combustible gas with less driving circuit and highly reliable. The CO2 sensor (MG811) is more popular due to its sensitivity and selectivity to detect the gas in real time environments. These are best in maintaining airflow control including the features like reproducibility and stability. The temperature sensor (TMP36) is familiar in various fields of applications that provide highest accuracy, low self-heating characteristic, low voltage operation and shutdown current to drain less than 0.5μA, which saves the power. The other components used are more generic and widely available in market for low cost and better reliability. The sensors are good in controlling the ventilation system of buildings and are widely used in the newly constructed buildings. The sensor readings can help to manage the control circuits in real-time mode. The experimental outcomes of the system (such as detecting gas and turning on the buzzer) indicate that the design criteria are met. Placing a small amount of CO and CO2 gases, respectively, near to the sensors, we test the system. CO and CO2 gas sensors detect the gases and send signals accordingly to the microcontroller. Finally, the microcontroller sends an activation signal to the buzzer. As a result, the buzzer rings and messages are displayed on the LCD screen. If the system needs to regain its initial conditions, then it is essential to press the reset button that brings the execution to the starting of the program which is stored in a microcontroller. Table II summarizes some important observations during the experiments using two previously introduced and the proposed gas detection systems. TABLE II.

Parameters CO detection CO2 detection Temperature Sensor A/C control LCD display Buzzer ring Design Complexity Cost Other Advantages

EXISTING VS. PROPOSED SYSTEMS

System-1 [16] Yes No

System-2 [17] No Yes

No

No

No Yes Yes Low

No Yes Yes Medium

Low

Medium

Alerts when CO is high

Alerts when CO2 is high

Proposed System Yes Yes Yes Yes Yes Yes Medium Low Alerts when CO and/or CO2 are high. Turns on the A/C if the temperature is high.

VI.

CONCLUSION

Various gases are used in and released from industries in large quantities. Some of these gases are toxic and cause serious health issues. These harmful gases have to be monitored so that any increase in the normal level of these gases could be known and proper precaution measures can be taken. With the help of various special sensors, hazardous gases can be potentially identified when they are processed through a gas detection system. These sensors usually employ an audible alarm to alert people when a dangerous gas has been detected. Currently available gas detection systems have many limitations: they are not easily portable, difficult to implement, have only one gas sensor, etc. This paper presents a novel embedded system to detect various perilous gases and automatically alert gas leakage in vulnerable premises. The proposed system consists of a temperature sensor to control the HVAC applications inside any residential premises. A test-bed embedded system is developed using Dragon-12 development board to evaluate the purposed system. In addition to CO, CO2, and temperature sensors, the proposed system consists of a buzzer and a LCD. CodeWarrior software is used to write and debug the code. The HVAC system has high accuracy and fast response to environmental parameters change. With the use of HVAC system, the level of CO2 and desired temperature can be monitored and controlled in the building by continuously observing and collecting the outputs from the sensor. By spreading CO2 gas to the system, the system is observed and analyzed. The gas leakage is detected with the help of the sensors. It is also noticed that the propagation delay is negligible. Considering various functionalities such detecting multiple gases, flexibility, LCD display, and sound-alarm system, the proposed gas detection system outperforms the others. For future extensions, sensors to detect other gases such as propane and methane can be added to the proposed system. To make the system more efficient and user friendly, the system can be added with a Global System for Mobile (GSM) communication module so that the users can be informed with a text messages as necessary. ACKNOWLEDGMENT We sincerely acknowledge Yogendhar R. Anugu, Anvesh Kolluri, and Rahul Kishan (students in EECS Department at Wichita State University) for their efforts to verify the results and to review the earlier drafts of this paper. REFERENCES [1] [2]

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