Introduction

In this project we are making an automatic LPG leak sensing alarm system. Taking the help of modern engineering and technology, liquefied petroleum gas can be detected by the sensor MQ6. It will avoid the fire accident by giving an alert alarm and can save energy by preventing its wastage. So, it is able to alert against serious burning accidents by butane gas present in LPG. The system is energized by using electricity.

Rationale

We can only smell the odour of LPG during leakage condition. But when a person goes to sleep by shutting the kitchen down at night, if the gas leaks then the system makes an alarm to avoid the whole night wastage of gas.

Scientific Principle

This sensor detects the concentrations of combustible gas in the air. The conductivity of the sensitive material inside it is higher when the gas concentration increases. As a result it activates the circuit and the siren is on.

Components required

1. Transistor bc547
2. Resistor
3. Capacitor
4. Diode 1N4007
5. Vero board
6. LED
7. Transformer 
8. Battery 12 V
9. Gas sensor
10. 555 IC
11. Relay
12. 7805 voltage regulator IC
13. Bzzer

Components Description

Transistor

A transistor amplifies current. It can be used with other components to make an amplifier or switching circuit. BC 547 is a general purpose transistor. It is an npn epitaxial silicon transistor. Its maximum collector current (DC) is 100mA.

Resistor

A resistor restricts the flow of current. The 1kΩ resistor used here is carbon film and quarter watt type. The 470Ω resistor used here is a wire wound type with 5 watt rating.

Capacitor

A capacitor stores electric charge. Capacitor used here is 1000 µF, 10 µF  and these are of electrolytic type.

LED (Light Emitting Diode)

It is a transducer which converts electrical energy into light energy.

Transformer

It consists of two coils of insulated copper wire linked by an iron core. Transformers are used to step up (increase) or step down (decrease) AC voltages. Energy is transferred between the coils by the magnetic field in the core. There is   no electrical connection between the coils. Here we have used a shell type step down transformer which step downs 230 volt AC to 12 volt AC. It can supply maximum 1A current. The working principle of transformer is very simple. It depends upon Faraday’s law of electromagnetic induction. Actually, mutual induction between two or more winding is responsible for transformation action in an electrical transformer.

Diode 1N4007

These are general purpose diodes. These diodes have high current capability and low forward voltage drop. The average rectified output current is one ampere.

NE 555

The 8-pin NE 555 timer is the most useful ICs ever made in the world. Its popular name is timer IC. It is used in many electronics projects. Just adding a few external components, it can be used to construct so many circuits. The 555 has three operating modes: Monostable mode, Astable mode and Bistable mode. It can withstand maximum supply voltage up to 16 volt. It has a maximum power dissipation up to 600mW.

Relay

Generally relay is defined as an electromagnetic switch. The relay used here is a 12 volt ice cube type.

7805 voltage regulator

The 7805 voltage regulator IC gives us a constant 5 volt DC power supply from a 12 volt rectified output voltage. So , where the rest of the 7 volt goes ? Actually, the rest 7 volt goes nowhere. It is dissipated as heat in the heat sink provided to the voltage regulator IC.

Gas Sensor

The gas sensor is a sensor which detects LPG in the air. When LPG is available near sensor it detects the iso-butane and provides an output based on gas concentration. The sensor is called MQ6.

Buzzer

A buzzer contains a piezo-electric material. Sound originates from vibration. When electric potential difference is applied to piezo-electric material, mechanical vibration is produced. Therefore sound is generated.

Working

The transformer steps down the 230 volt AC into 12 volt AC. The bridge rectifier converts 12 V AC into 12 V DC and filtered by the 1000 µF capacitor. The LED in series with 1 kΩ resistor is just for power indication purpose. The output is connected to 12 V battery terminals for charging. A diode is connected in series with the positive output of rectifier circuit and positive terminal of 12 V battery to avoid continuous glowing of power indicator even when we are not charging.

The components are connected appropriately following the design rule. The circuits are mounted on the board. Here is a simple circuit based on a sensor which sense leak of liquefied petroleum gas and generates an alarm to avoid serious accident and wastage of fuel.

The above astable multivibrator circuit drives the buzzer and the danger indicator simultaneously.

Application

1. Alert against serious burning accident.

2. Used in gas leakage detecting  equipments in family and industry, are suitable for detecting of  LPG, iso-butane, propane, LNG.

Contact:

Er. Anil Kumar Prusty

Phone: +91 9861004895