This project used in gas leakage detecting equipments in family and industry, are suitable for detecting of LPG, iso-butane, propane, LNG, avoid the noise of alcohol and cooking fumes and cigarette smoke.
This project makes use of MQ2 sensor which detects flammable gas like LPG. IC741 act as comparator which compares reference voltage (can be adjusted via VR1) with sensor voltage. When LPG gas detected sensor output voltage increases than the reference voltage, there by Comparator O/P will go to logic 1 from logic 0.
The O/P of comparator acts as input of relay driver ULN2003. This logic high signal from comparator activates relay and buzzer via ULN2003 .