The field of electronics plays a vital role everywhere from the scientific fields to the home appliances. In our home we use television, washing machine, air conditioner, refrigerator etc, which all falls under the list of the electronic components. Before, the television should be sufficiently tuned to get the desired channel. But now remote sensing facility with the automatic tuning of channels is available. This tuning is sufficiently done by the sensors. So sensor is a key factor of the automation field. For controlling the temperature of the chamber at the industries we use the temperature sensor. Similarly for monitoring the gas level in the environment and in fact in the chemical factories we use certain gas sensors. Generally a sensor does the work of converting the physical parameter to the electrical parameter. The physical parameter could be anything say humidity, temperature, pressure, force, vibration etc. this is converted in terms of voltage. Automation is almost an important factor in many areas. The technology reaches a peak day by day with its updated model (Al-Abbass, Al-Habashneh, Mohamed and Husain, 2009). A little change in the security system with the high resolution sensor and microcontroller system could provide a high impact. Power crisis is said to be a common problem around the world. Saving the electric power is an utmost important factor. With the help of sensor this could be highly achieved. The load shedding could also be minimized. Sensor senses the environment and provides a high signal to the microcontroller that could be easily coded with the embedded C language. Other then the microcontroller, we could also use the Arduino set that should be programmed.
The level of living has been enhanced with monitoring the environment situation around the living. Despite of these situations, selection of sensors is an utmost important factor and it is still a difficult process. Hence the equipment is sufficiently selected according to the scenario. We have used ATMEGA 328 microcontroller for the project, which is said to be a part of embedded system. Embedded system is said to be the combination of hardware and software that has been designed to do a specific task (Babrauskas, 2008). They are widely used everywhere around the communication application, Automation in industries with the control software, autonomous sensors, military and aerospace application. They could sufficiently reduce the time of designing a product as well as provides an environment in real-time monitoring of large amount of generated data. In our paper we have briefly discussed regarding various types of gas and temperature sensors and we have used LPG gas sensor for
The block diagram of this project is shown in the figure given below. Here the sensor such as temperature and gas sensors detects the temperature and the gas level of the particular environment. If the gas or the temperature exceeds a predefined value, the indicated will be indicated by the microcontroller unit. The microcontroller used here is ATMEGA 328 microcontroller. This is further attached to the buzzer component. The buzzer in turns alarms the user regarding the warning condition (Blagojevich, Petkovich et al, 2011). Moreover, the transformer used here will step-down the input AC voltage and it is rectified as DC voltage by the rectifier circuit which is composed of 4 diodes connected as a bridge circuit. This voltage is passed through the voltage regulator circuit. This regulated voltage is provided to the microcontroller. An LCD is also connected to the block. This gives out the numerical display of the permitted voltage to the circuit.
The type of sensor is used to measure the concentration of gas level in air. This sensor is typically used to detect any toxic gases and prevent its exposure from spreading into the environment. This technology is operated with the help of battery supply that could be used for safety purposes. Moreover, this sensor could be portable as well as fixed at a particular place. The indication could be given through visual indicators and acoustic indicators. Visual indicators come in the form of lighting systems and acoustical indicators come in the form of alarm. Traditional gas sensors were there to predict one gas at a time (ArunKumar, Rajasekhar, Satyanarayana and SuryanarayanaMurthy, 2012). But now, the sensors were calibrated to do multi-functional task by determining several gases by multi-gas devices (BSI 2011). These devices could be used in a particular area to monitor a small work place else it could be constructed as a protection system to work with the larger areas.
The response obtained from the sensors could be kept as a reference point. The detector when detects the gas higher than the reference point or when it exceeds the pre-set value, the system indicates and warns the user. There are several types of sensors and detectors available. Majority of the detectors should be chosen based on the sensors we use. Based on the environmental situation, it is advised to fit the sensor to detect the gas level and provide warning regarding its dangerous situation.
Based on the gas type it is necessarily categorized into two divisions: 1) Toxic 2) Combustible. Based on this wide range of category it is further classified based on the technology they adapt.
Electrochemical sensors:
These sensors or cells play a vital role in detecting toxic gases such as carbon monoxide, chlorine and nitrogen oxides. The signal produces an electric signal when the gas is detected. This electrical signal is displayed in the form of digital reading. Moreover, this type of sensor is highly sensitive.
Metal Oxide Semiconductors (MOS):
This sensor is composed of a thin gas sensitive film that is filled with the tin or tungsten oxides. This film is said to be highly sensitive that could detect the toxic gases easily. When the film detects any toxic gas it reacts and triggers the device (Utne, Hokstad, & Vatn, 2011). These devices are high in their efficiency since they could operate at a low humidity region. In fact, this device could also be used to detect the combustible gases.
2.1.3 Combustible Gases
The great manufacturer of gas detector devices is said to be the catalytic sensors that are highly manufactured. The detection of hydrocarbon could be effectively determined through this sensor due to the catalytic oxidation (Winter et al, 2013). The sensors are constructed with the wire coil that is treated with the platinum. When the catalytic surface is in contact with the combustible gases, oxidation takes place that releases the heat, which changes the resistance of the wire. This resistance change could be determined by the bridge circuit.
Hydrocarbon vapours are highly combustible that could be detected by the Infrared sensors and detectors, which is composed of transmitters and receivers. Normally these transmitters are said to be the optical sources and the receiver section includes the light detectors. If the optical path from the source is interrupted with any gas particles, the intensity of the light varies that could be identified by the detector. Through this intensity change of the light, we could be able to determine the type of gas that has been exposed in the environment.
Gas detectors are not only used for the home appliances but also they could be used for the Industrial purposes. They are commonly used in the welding shops and nuclear plants to detect the combustible as well as any toxic gases (Juntato, Xiaotao & Bingjie, 2010). The hazardous gas that evolves from the waste water plant could be effectively detected by these sensors. The gas sensors could be sufficiently fixed in the environment where manual interruption is very low in the area. These areas include storage bins, tanks, pits and vessels. Before the user entry place these detectors could be fitted that could provide the visualization.
Gas detectors work effectively that has high reliability, which could last up to a period of five years. But these detectors should be properly maintained and calibrated at a regular period. The method of calibration is effectively carried in order to check the working condition of the sensor in detecting various gases that are exposed in the environment. Infected sensors could not detect the toxic gases that could lead to the dangerous situation. Hence frequency calibration is predominantly carried out.
Description:
The Liquefied Petroleum Gas (LPG) sensor is simple to use that is suitable for sensing the gas particles especially butane and propane concentration in the environment (Apeh, Erameh and Iruansi, 2014). The detection could happen anywhere from 200 ppm to 10,000 ppm (parts per million). The sensors have two major advantages: 1) Response time is very fast 2) High sensitivity. The output from the sensor will be in the form of analog. When the heat coil is powered up with 5 volt by adding the load resistance and finally connecting the output to the Analog to Digital converter (ADC), it becomes a driver circuit. The LPG gas sensor is shown in the figure given below
Temperature Sensors:
For the detection of temperature we use temperature sensor. There are various types of temperature sensors
A temperature sensor is selected based on the following factors:
Thermistor:
The Thermistor is said to be a high temperature sensitive element that could also determine the Negative temperature coefficient (Chen, Hovde, Peterson & Marshall, 2008). It is extremely cheap where the lead resistance will be ignored constructed with the glass bead. It develops a non-linear curve for Resistance to Temperature characteristics. This particular sensor could not be used in the place of high temperature detection region.
RTD:
It could be used for detecting the high temperature range and it is said to be very accurate and stable. It is made up of platinum hence it becomes more expensive (Xin & Khan, 2007). It requires current excitation for its operation and it also has small resistance range. The main concern for this RTD will be the lead resistance and self heating. Hence a signal conditioning circuit should be introduced.
Thermocouple:
The best known temperature sensors used in the wide range of industries will be thermocouple. It works on the principle that if 2 conductors of varying materials are joined at a point then at the open ends, an emf will be produced (Asche, Osmundensen, Sandmark, 2012). This generated emf will be dependent on the temperature of the junction. This is shown in the figure given below. When T1 increases then the emf also varies. The reference end temperature is also concerned that could vary the emf. The temperature measure could exceed at a range of 600 degree Celsius.
Integrated Silicon Linear Sensor:
These sensors appear in the form of integrated format. They could measure the temperature range of about -40°C to +150°C. The limited accuracy will be +/- 2 degree. This sensor promotes a linear response and no calibration is required. The sensor could be directly interfaced with the Analog to digital converter (ADC) circuit device.
ATMEGA 328 Microcontrollers:
The entire general task could be performed by the computer very effectively such as storing the files after performing some calculations with the help of software or it could be used to browse by accessing the internet. Moreover, microcontrollers have been introduced to perform the specific task (Herriott et al, 2009). For instance, the operation of heater could be done with the help of microcontrollers. The heater state will be switched OFF when the temperature exceeds a predefined value or it will be switched ON when it has a fall in its set value. Microcontrollers come with the popular families such as AVR, 8051 and PIC. They have been created to perform the desired task. In this paper, we are going to get involved with the AVR microcontroller.
The features of the AVR Microcontrollers are as follows:
Description:
ATMEGA 1281 is an 8-bit AVR RISC-based microcontroller that is attached with 4/8/16 KB flash memory, which has Read-While-Write capabilities (Chen et al, 2008). The microcontroller is known for its high performance and consumes less power. The device has 512/1K/1K bytes SRAM with 54 general purpose input and output lines and 256/512 KB EEPROM. There are 32 working registers with the real time counter and timer module. Additionally it has the below features:
The device operates at a range of 2.7-5.5 volts. By executing the single clock cycle with the powerful instruction set, the system could achieve 1 MIPS throughput at a frequency of 1MHZ that saves the power consumption and balance the speed of the processor. The pin diagram of ATMEGA 328 microcontroller is shown in the figure given below
Architecture of ATMEGA 328 microcontroller
The Idle mode stops the CPU while allowing the SRAM, Timer/Counters, USART, 2-wire Serial Interface, SPI port, and interrupt system to continue functioning (Gottuk et al, 2012). The content of the register could be saved by the power down mode, by freezing the oscillator and it will disable all the chip functions till the next interrupt and the hardware starts to reset. The asynchronous timer works on the power save mode that maintains the base of the time and the other rest of the devices will be in the sleep mode (Hu, 2017). The CPU will be stopped by the ADC noise reduction mode and the remaining input-output modules lowers the noise level during the analog to digital conversion except asynchronous timer and ADC. The resonant crystal oscillator works at the standby mode and the other remaining devices will be in sleep mode (Klason, Andersson, Johansson & van Hees, 2011). This permits very quick start-up thereby leading to the consumption of minimum power.
The ATmega48, ATmega88 and ATmega328 differ only in memory sizes, RAM, EEPROM and interrupt vector sizes. Below is the table that describes the variation of these microcontrollers
Microcontroller variation with the flash, interrupt vector size and RAM variations
There is an isolated boot loader section for the ATMEGA 328 microcontroller, which greatly supports the Read-While-Write Self-Programming mechanism (Ashish, Ratnesh, Rajeev and Rahul, 2013). The execution of SPM instructions alone takes place in these microcontrollers (Chiti, 2009). While programming the ATMEGA 328 microcontroller there are certain points to be remembered that are as follows:
PUSH Button:
A push button plays a major role in starting and stopping an operation. This could be indicated by an open and closed switch in a PLC diagram. There is also manually operated push button which could be used for some emergency circumstances (Klason et al, 2011). The functionality of the push button is to move the position of the actuator into housing. This is supported by the spring mechanism which could open or close the contact. There are two types of push button namely momentary push button and Maintained contact push button (Meeravali and Anusha, 2012). Momentary push buttons will come to its actual position once the button is manually released and the maintained push button which is mechanically latched has a certain latching mechanism to hold its position. The push buttons can be categorized as Normally opened (NO), Normally closed (NC) and Change over (CO) type. At the position of NO the switch is opened and during the actuator action the contacts are closed which could permit the flow of air. At NC position the air is forbidden in this position and during the actuator position the contacts are closed.
This is a very simple device which could withstand any harsh environment and these relays are said to be electromagnetically operated (Marman, Peltier and Wong, 2008). These relay switches acts as a signal processing device. The relays are designed in such a manner to withstand the heavy power surges which could cause damage to the circuits. The system consists of the coil core through which the voltage is applied. This coil converts the electrical power into the electro-magnetic energy which will attract the armature towards the winding. The armature will actuate the relay making it to be in the open or closed position. Depending upon this operation the system provides the output (Richards, 2008). There is a spring attached in order to return the armature to the initial position. There is an interlocking capacity supported by the relays. This interlocking capacity will avoid the instantaneous switching of relays to ON and OFF.
The buzzer is said to be the audio signalling device that is used as an indicator. Buzzer is typically used as an alarm device that could be best suited for the security purposes. The types of buzzer could vary based on their manufacture:
Mechanical Buzzer: One of the best examples of the mechanical buzzer is said to be the joy buzzer.
Electro-mechanical Buzzer: this is the commercially used buzzer that sounds with the metal gong when the supply is given that could be directed by the relay switch. The buzzer interruption could also be done by the relay (Hartley, Medlock and Rosthal, 2012). The buzzer could be fitted to the wall of the ceiling.
Piezoelectric buzzer:
A piezoelectric element may be driven by an oscillating electronic circuit or other audio signal source, driven with a piezoelectric audio amplifier (Blagojevich, Petkovich and Simich, 2011). Sounds commonly used to indicate that a button has been pressed are a click, a ring or a beep. A simple applicable buzzer is shown in the figure given below
Voltage Regulator:
A regulator is sufficiently fixed after the rectifier circuit. This is done in order to get a particular voltage that is fed to the microcontroller and to the LCD display circuit (Milke, 2013). Here we have used BC547 transistor. This is said to be NPN Epitaxial Silicon Transistor. This small general-purpose transistor comes with the plastic packages. This purpose of this transistor is to maintain a switching operation and amplification of 45 V and 100 mA. The BC547 transistor is shown in the figure given below
BC 547 transistor pin configuration
This concept is best understood with the NPN configuration. Normally large current flows through the collector (Ic) and the emitter terminal. This occurs only if we have small biasing current that flows through the base terminal (Ib). This will enable the base terminal to acts as an current control input. The DC current gain is said to be the ratio of collector current and the base current (Ic/Ib). This is denoted as Beta, (β) (Winter, Moore, Davis & Strauss, 2013). The ratio of the collector current and the emitter current Ic/Ie, is known as Alpha (α). Since the emitter current is said to be the sum of collector current and the base current (Ie = Ic + Ib), the value of Ie will be close to the value of Ic (since we have a very small base current, the value of base current will be neglected). Moreover, the value of the alpha will be unity and in certain cases it could vary among 0.950 to 0.999. The NPN transistor configuration is shown in the figure given below
The function of the diode serves as a rectifier circuit that does either half wave rectification or either full wave rectification. These diodes are connected in the form of bridge circuit. Several points is to be remembered while using the rectifier circuit
Diodes such as IN4001, IN4002, IN4003, IN4004, IN4005, IN4006 and IN4007 are readily available in the market. The diode that we use for our application is IN4007 that has 50 V of the maximum reverse bias voltage capacity and 1 A of maximum forward current capacity. Diodes with the varying capacities could be attached with one another (Rose-Pehrsson et al, 2011). Diode with the high capacity could be attached in the place of low capacity but the vice versa is not possible. For instance IN4007 could be used in the place of IN4002 but IN4001 could not be used instead of IN4007.
Working:
A P and N junction together forms a diode. P junction is said to be the composition of holes and N junction is the composition of electrons (Coster & Hankin, 2008). When the voltage is applied in the forward bias, there will be the movement of electrons towards the positive side of the terminal due to the positive potential. The movement of the electrons from the N side will be filled by the negative terminal of the battery thus making a current path. The current path could be achieved only when the depletion layer of the diode crosses 0.7 V. Thus the majority charge carriers from the N side will tend to move towards the positive side of the battery (Proulx, 2008). In case of reverse bias, there will be attraction of electrons towards the positive terminal of the battery and thus increasing the depletion layer. So no conduction happens and at last due to the avalanche of electrons we have breakdown voltage (Rothmann, Gamache et al, 2011). The function of PN junction diode is illustrated in the figure given below
A resistor is a 2 terminal device that tends to obey ohm’s law. Ohm’s law states that the voltage across the terminal will be directly proportional to the current in which the current will be opposed by the resistor. According to Ohm’s law,
The unit of the resistor is denoted as ohm (Ω). Resistors play a vital role among all electronic components. For higher practical applications resistors is made up of nickel or chrome that is said to be high resistivity alloys (Stewart, 2008). The resistors could be identified by the colour codes with the combination of tolerance band. The main role of a resistor is to dissipate the power by resisting the current (Ramya & Palaniappan, 2012). The value below which the dissipation of the power will be limited by maximizing the current flow at a limit of the applied voltage is known as critical resistance (this depends on the material and the design of the resistor).
Resistors with their varying dimensions
Capacitors:
A passive electronic device that is composed of two conductive plates separated by the dielectric medium is known as capacitance. An electric field is developed across the dielectric when the voltage is applied across the conductive terminals. The energy is stored across the terminal that promotes a mechanical force between the plates (Blake, 2010). The effect varies based on the type of the conductor (wide, parallel, and flat).Normally plate type capacitance is commonly used since it permits only a low leakage current. The unit of capacitor is Farads. Ideally capacitor is calculated by the permittivity of air and vacuum with the area and the distance of the dielectric medium. But practically there will be some leakage current (Shin-Juh Chen et al, 2008). An equivalent resistance will be introduced by the conductor and the lead terminals of the capacitor. The breakdown voltage will be limited by the dielectric that permits the electric field. The quality factor and the resonant frequency will be determined by the capacitor’s properties. Additionally it also determines the operating frequency with the power dissipation factor. The various forms of capacitor are shown in the figure given below
Various forms of capacitor
Capacitor is an electronic component that helps in storing the electric charge. In filter networks, it serves the best purpose by blocking the DC current and allowing the AC current to pass, while it serves in smoothing the output of the power supply by tuning a particular frequency neglecting the remaining.
LCD display:
The Liquid Crystal Display screen works on the principle of blocking the light source. This consumes less power when compared to the LED’s (Tsow et al, 2009). This is just an indication that shows the status of the working condition.
Keil µVision IDE:
The Integrated Development Environment of µVision combines the project, builds the facilities required, provides the run-time environment, provides the platform for editing the source code, and debugs the program inside a single powerful environment (Thompson & Bank, 2007). µVision is very easy to handle and it will fasten the embedded software development. This allows in creating the individual window layout and chains multiple screens on the visual surface.
The application code will be tested, verified and optimized under a single environment in the debugger environment (Rubin et al, 2007). The debugger permits commercial features like simple and complex breakpoints, executes the control, monitors the windows and permits entire visibility to the peripheral devices (Singh and Singh, 2012). Keil development tools for the 8051 Microcontroller Architecture support every level of software developer from the professional applications engineer to the student just learning about embedded software development. In order to go to a new project, the microcontroller which we use should be selected and the database could be viewed from the device (Wali and Russen, 2012). This will set the compiler, assembler, linker, and memory options of µVision IDE for the user.
MC Programming Language: Embedded C
In our project we have used the Embedded C language. This is similar to the high-level C programming language. Through this program we could integrate all the hardware components with the software platform. The pin configuration of the microcontroller device should be given properly with their necessity configuration.
The testing and the working of our particular setup is as follows:
Conclusion:
This paper has been done regarding the home and the industrial automation by testing various gas and temperature sensor. At last the best sensor for this project has been selected and finally the output has been received by the ATMEGA 328 microcontroller. Using the temperature sensor, the alert signal could also be obtained when the temperature is raised to a particular defined level. Moreover, in industries this could be used to detect the temperature of the chamber and adjust according to that. Gas sensor plays a main role in every industry for monitoring the gas level of the environment. This project extremely reduces the cost with the enhancement in the functionality.
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