Semiconductor Combustible Gas Sensor MQ-2

How to design and fabricate a reliable Combustible Gas Detector Alarm using easy to use and inexpensive components?One good answer to the question is MQ-2.Yes,we can build such a useful circuit (suitable for detecting of LPG, i-butane, propane, methane ,alcohol, Hydrogen,smoke) using the MQ-2 Semiconductor Gas Sensor!

MQ-2 is a Semiconductor Sensor for Combustible Gas.MQ-2 gas sensor has high sensitity to LPG, Propane and Hydrogen, also could be used to Methane and other combustible steam, it is with low cost and suitable for different application.Sensitive material of MQ-2 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.Just use simple electrocircuit, Convert change of conductivity to correspond output signal of gas concentration.

Features of MQ-2

*Good sensitivity to Combustible gas in wide range

* High sensitivity to LPG, Propane and Hydrogen

* Long life and low cost

Application of MQ-2

* Domestic gas leakage detector

* Industrial Combustible gas detector

* Portable gas detector

Basic test circuit of the sensor is shown here.The sensor need to be put 2 voltage,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: Power of Sensitivity body(Ps): Ps=Vc2×Rs/(Rs+RL)2.

MQ-2 sensor is composed by micro AL2O3 ceramic tube, Tin Dioxide (SnO2) sensitive layer, measuring electrode and heater are fixed into a crust made by plastic and stainless steel net. The heater provides necessary work conditions for work of sensitive components. The enveloped MQ-2 have 6 pin, 4 of them are used to fetch signals, and other 2 are used for providing heating current.

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