The Ximimark MQ135 MQ-135 air quality sensor module is designed for detecting a range of hazardous gases including ammonia, sulfide, benzene vapor, smoke, and other airborne contaminants. Each module is built around the original MQ-135 gas sensor, featuring a sensitive semiconductor layer that changes resistance when exposed to target gases. The board integrates both analog and digital signal outputs, giving users flexibility to interface with microcontrollers like Arduino. A built-in potentiometer allows adjustment of the digital threshold level for triggering alarms or logic signals. The PCB is crafted from standard FR-4 material with clean solder joints and clearly labeled pin headers (VCC, GND, DO, AO), ensuring straightforward wiring.

With a dual output design, this module can be used in continuous monitoring setups or threshold-based alert systems. The compact 32mm x 17mm footprint fits easily into breadboards and enclosures. Package includes three identical units, providing convenience for multi-point measurement or backup units. Each module requires a 5V DC power supply and delivers a stable signal response under normal operating conditions.

The analog output voltage varies proportionally to gas concentration, enabling fine-grained data collection. The digital output goes high/low when the preset threshold is exceeded, offering simple on/off detection. This module is particularly suited for indoor air quality monitoring, gas leak detection in workshops, and environmental sensing projects. The sensor’s sensitivity can be calibrated using the onboard trimmer, though factory settings suffice for most general applications.

The working temperature range is typical for semiconductor gas sensors (approx. -10 to 50°C), and warm-up time of about 20-30 seconds is recommended for accurate readings. While not intended for precise industrial grade measurements, it provides reliable relative indication of hazardous gas presence. The three-pack configuration offers excellent value for hobbyists, makers, and educators working on multiple Arduino-based detection projects.

The modules are lightweight (approximately 6 grams each) and require basic soldering for header attachment if not pre-soldered. All units are batch tested for basic functionality before packaging. This sensor works well with Arduino analog inputs or digital interrupt pins. The design prioritizes cost-effectiveness without compromising basic detection capability, making it an accessible tool for learning and prototyping in electronic gas sensing.