Microcontroller Based LPG Gas Detector Using GSM Module
INTRODUCTION
The presence of dangerous LPG leakage in the cars, service station or in the storage tank environment can be detected using the Ideal Gas Sensor. This LPG gas leakage detector unit can be easily integrated into a unit that can sound an alarm or give a visual suggestion of the LPG concentration. The sensor has both admirable sensitivity and rapid response time. This sensor can also be used to sense other gases like iso-butane, propane, LNG and even cigarette smoke.
The output of the sensor goes LOW as soon as the LPG sensor senses any gas leakage from the storage. This is detected by the microcontroller and the LED & buzzer is turned ON. After the delay of few milliseconds, the exhaust fan is also turned ON for throwing the gas out and it continues sending message as ‘GAS LEAKAGE’ to a mobile number which is pre-defined.

LITERATURE REVIEW

Various research groups are working all over the world for the development of Microcontroller based LPG Gas Leakage Detectors using GSM Module. The main applications of a LPG Gas Leakage Detector would be : * As a protection from any gas leakage in cars, industries, homes, hospitals etc. * For safety from gas leakage in heating gas fired appliances like boilers, domestic water heaters. * In Large industries which use gas as their production * For safety from gas leakage in cooking gas fired appliances like ovens, stoves etc.

This project has many advantages which are as follows : * The Project is easy to use and it gives remote indication to the user. * The sensor used in this Project has excellent sensitivity combined with a quick fast response time. * The system is highly reliable, tamper-proof and secure. * In the long run the maintenance cost is very less when compared to the present systems. * It is possible to get instantaneous results and with high accuracy.

This Project has a lot of Future Scope in the sense that using this project, we can provide a voice feedback system in the future. With recent development in technology, Temperature display during periods wherein no message buffers are empty is one such theoretical improvement that is well possible. Another very interesting and significant improvement would be to accommodate multiple receiver MODEMS at different positions in the geographical area carrying duplicate SIM cards. Multilingual display can be another added variation in the project. Audio output can be introduced to make it user Friendly.

WORKING METHODOLOGY/PROPOSED ARCHITECTURE

MQ-5 semiconductor sensor is Combustible Gas Sensitive. The MQ-5 gas sensor is made up of SnO2 which has lower conductivity in clean air. A simple electro-circuit is used here which is used to convert the changing conductivity into corresponding output signal of gas concentration. Both Methane and Propane can be detected easily by MQ-5 sensor because it has high sensitivity towards Methane, Propane and Butane. It is a low cost sensor suitable for different application.

BLOCK DIAGRAM FOR LPG GAS LEAKAGE DETECTOR

Block Diagram for Gas Leakage Detector

BLOCK DIAGRAM DESCRIPTION
MICROCONTROLLER
It is the heart of the project. It is used to control the Exhaust fan, LED and Buzzer when LPG leakage occurs. The input/ output ports of the microcontroller are used for this purpose. MQ-5 LPG SENSOR
This sensor is used to sense the leakage of LPG. In normal conditions the output of this sensor is ‘high’ and it goes ‘low’, when the LPG is sensed. EXHAUST FAN
The LPG is pushed out into the environment using an exhaust fan which reduces the concentration of LPG near the leakage area. BUZZER
The leakage of the LPG is indicated by using the buzzer. It is 12 V DC operated buzzer. LED
The leakage of the LPG is indicated by using the LED. It is 1.2 V DC operated LED.

MQ-5 LPG GAS DETECTOR MODULE
WORKING PRINCIPLE
In TGS gas sensors the sensing material is a metal oxide, most typically SnO2. The oxygen gets adsorbed on the crystal surface with a negative charge when the metal oxide crystal such as SnO2 is heated at a particular temperature in air. The donor electrons on the crystal surface are then transferred to the adsorbed oxygen which results in leaving positive charges in the space charge layer. Thus the surface potential serves as a potential barrier against the electron flow. The electric current flows in the sensor through the combination parts (grain boundary) of SnO2 micro crystals. Adsorbed oxygen forms a potential barrier at the grain boundaries which prevents carriers to move freely. The electrical resistance of the sensor is recognized by this potential barrier. The surface density of the negatively charged oxygen decreases in the presence of deoxidizing gas which reduces the barrier height in the grain boundary. This reduced barrier height decreases the sensor resistance.

GSM MODULE
For sending message, a GSM Module named SIMCOM_300 with RS232, power supply, buzzer and audio interface are used. This can be connected to PC by using a USB to Serial Adaptor. Terminal programs such as Real term are used to send & receive data. The interface between GSM Module and microcontroller can also be done directly with the help of wires.
GSM Module works with AT COMMANDS where AT stands for Application Terminal.