HIGH SENSITIVE LPG SENSOR WITH GAS LEAK ALERT BUZZER

Under the guidance of Mr. A. Raghavendra Prasad

Submitted by Batch X

S. Venkata Sudeshna 08X51A0265P. Raghavendra 08X51A0237E. Swathi 08X51A0258G. Ravi Kanth 08X51A0240N. Paramesh 08X51A0232

INTRODUCTION

Gas leak detection is the process of identifying potentially hazardous gas leaks by means of various sensors. These sensors usually employ an audible alarm to alert people when a dangerous gas has been detected. Common sensors used today include Infrared Point Sensors, Ultrasonic Sensors, Electrochemical Sensors, and Semiconductor Sensors. These sensors are used for a wide range of applications, and can be found in industrial plants, refineries, wastewater treatment facilities, vehicles, and around the home.

History

Gas leak detection methods became a concern after the effects of harmful gases on human health were discovered. Before the development of electronic household carbon monoxide detectors in the 1980s and 90s, carbon monoxide presence was detected with a chemically infused paper that turned brown when exposed to the gas. Since then, many technologies and devices have been developed to detect, monitor, and alert the leakage of a wide array of gases.

TYPES OF DETECTORS1. ELECTROCHEMICAL DETECTORS

2.INFRARED POINT DETECTORS

3.SEMICONDUCTOR DETECTORS

4.ULTRASONIC DETECTORS

Semiconductor Detectors Semiconductor sensors detect gases by a chemical reaction that takes place when the gas comes in contact with the sensor. Tin dioxide is the most common material used in semiconductor sensors. the sensor must come in contact with the gas in order to detect it, semiconductor sensors work in a smaller range than infrared point or ultrasonic detectors

Household Safety There are many different sensors that can be purchased to detect hazardous gases around the house. Carbon monoxide is a very dangerous gas that robs the lungs of oxygen, killing hundreds of people worldwide each year. It is an odorless, colorless gas, making it impossible for humans to detect it. This LPG gas sensor can be used as a wireless gas leak detector in home security system.

LPG Sensor Sensitivity control circuit

Transistor driver circuit

Buzzer

BLOCK DIAGRAM

CIRCUIT DIAGRAM

POWER SUPPLY:

The input to the circuit is applied from the regulated power supply. The A.C. input i.e., 230V from the mains supply is step down by the transformer to 12V and is fed to a rectifier. The output obtained from the rectifier is a pulsating D.C voltage. So in order to get a pure D.C voltage, the output voltage from the rectifier is fed to a filter to remove any A.C components present even after rectification. Now, this voltage is given to a voltage regulator to obtain a pure constant dc voltage.

Transformer:

Usually, DC voltages are required to operate various electronic equipment and these voltages are 5V, 9V or 12V. But these voltages cannot be obtained directly. Thus the A.C. input available at the mains supply i.e., 230V is to be brought down to the required voltage level. This is done by a transformer. Thus, a step down transformer is employed to decrease the voltage to a required level.

Rectifier:The output from the transformer is fed to the rectifier. It converts A.C. into pulsating D.C. The rectifier may be a half wave or a full wave rectifier. In this project, a bridge rectifier is used because of its merits like good stability and full wave rectification.

The Bridge rectifier is a circuit, which converts an ac voltage to dc voltage using both half cycles of the input ac voltage. The circuit has four diodes connected to form a bridge. The ac input voltage is applied to the diagonally opposite ends of the bridge. The load resistance is connected between the other two ends of the bridge.For the positive half cycle of the input ac voltage, diodes D1 and D3 conduct, whereas diodes D2 and D4 remain in the OFF state. The conducting diodes will be in series with the load resistance RL and hence the load current flows through RL.

For the negative half cycle of the input ac voltage, diodes D2 and D4 conduct whereas, D1 and D3 remain OFF. The conducting diodes D2 and D4 will be in series with the load resistance RL and hence the current flows through RL in the same direction as in the previous half cycle. Thus a bi-directional wave is converted into a unidirectional wave.

Capacitive filter is used in this project. It removes the ripples from the output of rectifier and smoothens the D.C. Output received from this filter is constant until the mains voltage and load is maintained constant. However, if either of the two is varied, D.C. voltage received at this point changes. Therefore a regulator is applied at the output stage.

FILTER:

Voltage regulator:

As the name itself implies, it regulates the input applied to it. A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. In this project, power supply of 5V and 12V are required. In order to obtain these voltage levels, 7805 and 7812 voltage regulators are to be used. The first number 78 represents positive supply and the numbers 05, 12 represent the required output voltage levels.

Configuration

MQ9 SENSOR

MQ- 9

Semiconductor Sensor for CO/Combustible Gas

Sensitive material of MQ-9 gas sensor is SnO2,

MQ-9 gas sensor has high sensitity to Carbon Monoxide, Methane and LPG. The sensor could be used to detect different gases contains CO and combustible gases, it is with low cost and suitable for different application.Character Configuration•Good sensitivity to CO/Combustible gas •High sensitivity to Methane, Propane and CO •Long life and low cost •Simple drive circuit Application•Domestic gas leakage detector •Industrial gas detector •Portable gas detector

TWO TERMINAL PRESET

The regulated 5v supply from voltage regulator is given to senor board through a two pin Relament connector. This power is utilsed by the sensor and transistor. A preset is used to adjust the sensitivity of the gas sensor and the value of this is 50 kΩ. Whenever LPG is detected the output of sensor is high, this output drives the transistor into saturation region which activates the buzzer. This buzzer activates depending upon the gas particles surrounding the environment.

CONCLUSION

Finally we conclude that this LPG Gas Sensor is used to detect the presence of a dangerous LPG leak in your Home, car or in a service station, storage tank environment.. The sensor can also sense iso-butane, propane, cigarette smoke. We can also use this as a wireless Gas leak detector in home security system..

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