simple....but more useful.....

DANGERS OF INFLAMMABLE GASES LEAKAGE-

Now a days the use of inflammable materials like LPG, Methane, propane, alcohol etc. is increasing fast and leakage is common due to extensive use of non standard instruments.The danger increases when leakage occurs in closed area.This causes mainly "asphyxia" means lack of oxygen causes suffocation.If the amount of leakage is enormous this causes the death of individuals.To prevent serious damage to the living beings earliest detection of leakage is important.

                                             

but here is a solution for detecting the inflammable gas leakage.The circuit uses a gas sensor(MQ-6) which can detect the presence of LPG, propane, methane and other combustible materials.

MQ-6 SEMICONDUCTOR SENSOR FOR COMBUSTIBLE GASES-

Sensitive material of MQ-6 gas sensor is SnO2, which with lower conductivity in clean air. When the

target combustible gas exist, The sensor’s conductivity is more higher along with the gas concentration

rising. Please use simple electro circuit, Convert change of conductivity to correspond output signal of

gas concentration.

MQ-6 gas sensor has high sensitivity to Propane, Butane and LPG, also response to Natural gas. The

sensor could be used to detect different combustible gas, especially Methane, it is with low cost and

suitable for different application.

mq-6 gas sensor

GAS SENSOR PCB LAYOUT AND CONFIGURATION-

                   

                                                                       

BASIC TEST LOOP-

The above is basic test circuit of the sensor. The sensor needs to be put 2 voltages, heater voltage (VH） and test voltage (VC). VH used to supply certified working temperature to the sensor, while VC used to detect voltage (VRL) on load resistance (RL) whom is in series with sensor. The sensor has light polarity, VC need DC power. VC and VH could use same power circuit with precondition to assure performance of sensor. In order to make the sensor with better performance, suitable RL value is needed:

CIRCUIT DIAGRAM

       

POWER SUPPLY FOR CIRCUIT-

WORKING-

The op-amp LM358 is designed in a comparator mode which compares the signal received from the sensor to a threshold voltage(reference voltage).  Potentiometer of 10kΩ is connected at pin no. 2.It is set at 2V(reference voltage).    The voltage 2V is equal to  output voltage of gas sensor in normal air condition i.e. in absence of gas. LM358 compares two input i.e. preset voltage i/p at inverting end with gas sensor o/p voltage at non-inverting end. In absence of gas the output voltage of gas sensor is 2V thus overall output voltage of op-amp will be 0V. In presence  combustible gases  input voltage reduces and output voltage of gas sensor increases thus creating difference between two input voltage of op-amp.  Thus output voltage of LM358 lead to triggering of buzzer and thus alarm sound generates and LED glows showing the presence of combustible gas. 

SNAPSHOTS-

           

                   

                  

                                       

Good luck

sourabh mathur.
22/07/2012