The MQ-4 gas sensor board is a semiconductorbased sensing module designed for the detection of methane (CH₄) and compressed natural gas (CNG). The sensing element exhibits high sensitivity to methane, making the module suitable for gas leak detection, gas alarm systems, and safetyrelated monitoring applications. The typical detection range extends from 300 to 10,000 ppm.

The module operates from a 5 V DC supply and integrates the required heater circuitry to maintain the sensing element at its specified operating temperature. Variations in methane concentration cause changes in the sensor resistance, which are converted into an analog output voltage in the range of 0 to 5 V. In addition, a digital output is provided via an onboard comparator with an adjustable threshold, enabling direct connection to microcontrollers or alarm circuits without additional signal conditioning.

After each power-up, the sensor requires a heatup time of approximately 10 to 15 minutes before reliable measurements can be obtained. For initial commissioning, a burn-in period of 48 to 168 hours of continuous operation is recommended to stabilize the sensing element. Following this period, a baseline resistance measurement in clean air should be recorded as a reference value. If the sensor has been powered off for several weeks or longer, repeating the burn-in and baseline procedure is advised to maintain measurement consistency.

The board is equipped with power and status LEDs for visual indication of operation and detection status. For mechanical and layout flexibility, the LEDs may alternatively be soldered on the opposite side of the PCB. Electrical interfacing is provided via a 4-pin 2.54 mm header and a Molex PicoBlade connector, enabling straightforward integration into embedded systems, microcontroller platforms, and gas detection devices.