Attributes

Brand	-
Category	Robotics / STEM Teaching Tools / Sensors
Origin	-
Model Number	MQ-135
Detection Gases	Ammonia, NOx, Alcohol, Benzene, Smoke, CO2
Operating Voltage	5V DC
Output Signal	Analog and Digital (TTL)
Heater Voltage	5.0V ± 0.2V
Load Resistance	Adjustable via Potentiometer
Preheat Time	24 Hours (Recommended)
Interface Type	3-Pin Header (VCC, GND, OUT)
PCB Dimensions	32mm x 20mm
Application	Arduino, Raspberry Pi, DIY Air Quality Monitors

6 reviews

Anonymous

Mar 29, 2026

Rating: 4/5

Easy to integrate

As a beginner, I found this easy to wire up. The pins are clearly labeled. My only issue was understanding the raw data values at first, but after finding a library online, it works perfectly.

Anonymous

Mar 19, 2026

Rating: 5/5

Reliable and sensitive

I bought two of these for a classroom air quality demonstration. They are highly sensitive to changes in air composition. The dual output (analog and digital) gives flexibility for different coding approaches.

Anonymous

Mar 18, 2026

Rating: 3/5

Works but gets hot

Functionality is fine for basic detection, but the heating element gets quite warm during operation. Make sure your enclosure has ventilation. Documentation could be better, but there are plenty of tutorials online.

Anonymous

Mar 07, 2026

Rating: 5/5

Perfect for my smart home project

This sensor works exactly as described. I connected it to my Arduino Uno and was able to read analog values within minutes. The potentiometer makes calibrating the digital threshold very easy. Great value for the price.

Anonymous

Mar 05, 2026

Rating: 4/5

Good sensor, requires patience

The module is well-built and the soldering points are clear. Just remember that it needs a long preheat time (about 24 hours) before the readings stabilize. Once warmed up, it detects smoke and alcohol vapors very quickly.

Anonymous

Mar 05, 2026

Rating: 5/5

Great for monitoring ventilation

Using this to monitor ammonia levels in my small greenhouse setup. It triggers my exhaust fan when levels rise. Very responsive and the build quality seems durable for indoor use.

5 FAQ

Q: Does this module work with 3.3V logic boards like the ESP8266?

A: Yes, the digital output is TTL compatible, but for the analog output, you may need a voltage divider if your board's ADC cannot handle 5V. The heater requires 5V to operate correctly.

Q: How long does it take for the sensor to give accurate readings?

A: While it responds quickly to gas presence, we recommend a continuous preheat time of 24 hours for the first use to stabilize the internal sensing element for accurate baseline readings.

Q: Is there a library available for Arduino?

A: Yes, there are several open-source libraries available in the Arduino Library Manager. Search for 'MQ135' to find calibration and reading examples contributed by the community.

Q: What is the power consumption of this module?

A: The heating element consumes approximately 150mA at 5V. Please ensure your power supply can handle this current draw, especially if powering multiple sensors.

Q: Can this detect carbon monoxide specifically?

A: The MQ-135 is sensitive to a broad range of gases including CO, ammonia, and benzene. It is not specific to Carbon Monoxide alone; for dedicated CO detection, an MQ-7 sensor is recommended.

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