Gas sensor (MQ5 sensor)

MQ5 sensor is used in gas leakage detecting equipments in the industries and house. It has high sensitivity to liquefied petroleum gas (LPG) and small sensitivity to alcohol and smoke. The characteristics of this sensor are fast response, stable, long life and have simple drive circuit.

When a dangerous levels of gas vapors are detected. A detectors measure a gas concentration and the sensor responds to a calibration gas, which serves as the reference point or scale. Usually the reference point or scale is in voltage (V). The calibration of MQ5 is important in order to compare the sensitivity of MQ5 when detecting oxygen gas or liquefied petroleum gas (LPG). For an example, if the MQ5 sensor detects oxygen gas it might produce a low value of output voltage but when it detects other gases especially LPG gas it will produce a high value of output voltage. The output voltage value is between ranges 0 until 5 volts.

Based on the picture above, MQ5 have 6 pins (2 A, 2 B and 2 H). Pins for A should be attach together and then connect with the pin H for become an input connection. On the other hands, pins B will be the output connection, meanwhile the other H pin become grounded. Before the sensor connects to theATmega328 pins, it should face some calibration with lighter gas using a multi-meter to identify differences of voltage output value in normal condition (normal atmosphere) and worst condition (when detecting any presence of liquefied petroleum gas). During normal condition, the voltage output is less than 1.5 volts. When the MQ5 detected the gas produce by the lighter, the voltage output is 2 volts and above. This output values are important because it will be useful data during program writing.

Figure below shows the connection wires of gas sensor (MQ5) at the analog pins of ATmega328.