This semiconductor gas sensor detects the presence of methane (CNG) gas at concentrations from 300 ppm to 10,000 ppm, a range suitable for detecting gas leaks. The sensor’s simple analog voltage interface requires only one analog input pin from your microcontroller.
Overview
This methane gas sensor detects the concentration of methane gas in the air and ouputs its reading as an analog voltage. The concentration sensing range of 300 ppm to 10,000 ppm is suitable for leak detection. For example, the sensor could detect if someone left a gas stove on but not lit. The sensor can operate at temperatures from -10 to 50°C and consumes less than 150 mA at 5 V. Please read the MQ4 datasheet (161k pdf) for more information about the sensor.
Gas sensor with metal case bottom view.
Connections
Connecting five volts across the heating (H) pins keeps the sensor hot enough to function correctly. Connecting five volts at either the A or B pins causes the sensor to emit an analog voltage on the other pins. A resistive load between the output pins and ground sets the sensitivity of the detector. Please note that the picture in the datasheet for the top configuration is wrong. Both configurations have the same pinout consistent with the bottom configuration.The resistive load should be calibrated for your particular application using the equations in the datasheet, but a good starting value for the resistor is 20 kΩ.
We offer two breakout boards that make it easier to interface with these sensors: a Pololu carrier board and a SparkFun carrier board. The Pololu version is shown below.
Pololu MQ gas sensor carrier with sensitivity-setting resistor soldered in the vertical orientation.
