LPG Sensor modules are available now at low cost and we can use it in the Kitchen as a Gas leakage Alarm. The Module has a MQ6 Gas sensor, an Op-Amp as comparator and a preset for adjusting the sensitivity. All we need is a load resistor at the output to connect with the alarm circuit. Module is very sensitive to LPG (Liquefied Petroleum Gas) which contains Propane and Butane. The MQ6 sensor detects the gas concentration between 200 to 10,000 ppm.
The module works off 5 volts DC and has two outputs.
1. The Analogue output ( A) can be used to drive a buzzer through a driver transistor.
2. The Digital output ( D) can be used for Micro controller based circuits.
The MQ6 LPG Sensor has 6 pins. But in the Sensor module, the MQ6 is already connected.
This is how the Gas sensor module is used to drive a buzzer as alarm
How to Test?
Connect the Module with the Buzzer driver circuit . Adjust the Preset in the module just to turn off the output LED. Then light a Cigarette lighter and keeping its knob pressed, puff off the fire. You can smell the gas. Show it near the Gas sensor and adjust VR1 (Load resistor) till the buzzer beeps. Place the circuit on the wall 1 foot above the Gas cylinder. Use a 9 volt battery to avoid electric wiring.
More about gas sensors
Gas Sensors are devices which detects the presence of gases in an area. These are used for safety purposes to activate alarm systems as warning measure or to shut down a machinery. Gas detectors are used to detect different kinds of gases like combustible, flammable and toxic gases.
Catalytic detectors use the basic oxidation principle to detect a combustible gas like LPG. When the gas oxidizes, heat generates and the gas sensor converts this heat in to corresponding electric signals. A standard Wheat stone arrangement is used for this. The output from the gas sensor is equal to the concentration of gas in the area. The heater inside the sensor has two heating elements. One is the active element and the other is the reference element.
The active element is placed in the catalyst. When the combustible gas reacts exothermically with the oxygen, temperature rises due to catalytic action. The rise in temperature changes the resistance of the active element. The catalytic reaction takes place on the surface of the catalyst. The reference element is non- responsive to gas and gives the base line signal to compensate atmospheric temperature changes. This prevents false triggering of the alarm system.
6 Pin Gas sensors
These are sensitive semiconductor Gas sensors that give an analog voltage at the output when the air contains Combustible gas molecules. In clean air, it gives low voltage and when the gas concentration increases, output voltage also increases accordingly.
The Sensors are provided with 6 pins but 4 pins are sufficient for connection.
H-H pins – These are used for providing 5V DC to the heater element. These pins have no polarity and one H can be connected to 5V DC and the other to the ground.
Pins A – A (or B-B). The A and B pins can be used for providing 5 V DC or to get output voltage. If the pins A are used (by shorting), pins B( by shorting) act as the output or Vice versa.