LPG Sensor Alarm
LPG gas detection project’s main idea is to implement the security system for detecting leakage of liquid petroleum gas in closed environment. In this project gas leakage is identified by using MQ6 gas sensor. A simple circuit with an Op-Amp IC is powered by a step down transformer and finally the alarm produces on detecting gas.
Required Components :
- LM358 Op-amp IC
- MQ6 Sensor module
- LM2596 buck converter
- Buzzer 5V
- Transformer 12V/1A
- NPN Transistor BC547
- Preset 10K (variable resistor)
- Capacitors & resistors etc.
Note : 6V Transformer can also be used but remember about the current rating of transformer must be of minimum 1A. Since the sensor heated up so it requires large working current.
The 5V power supply for the above circuit is provided by IC LM2596 based buck converter. It is highly efficient than LM78XX series ICs. You can get this readymade power supply board from the market. It has an adjustable range for better voltage regulation.
Working principle :
The MQ6 sensor has an ceramic crystal coated with a sensing material is a metal oxide, mostly SnO2. During power supply the heater gets heated up for faster chemical reaction. The oxygen gets adsorbed on the crystal surface with a negative charge when the metal oxide 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.
In presence of the gases the electric current flows in the sensor through the reaction of SnO2 molecules. 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.
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