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Faulty MQ2 Sensor In Gas Detector

By on August 25, 2015
mq2 sensor








I received a gas detector for repair, the complaint is: after few minutes the beeper will sound but the gas is not interrupted. After connecting the detector, it takes about 2 minutes to calibrate; next it will enter in detection mode. When detect the gas leakage, the gas is interrupted for safety.

gas detector repair

In the above picture you can see the gas detector, no name.


Four screws and the detector were opened. Take a look at the circuit board below:

gas detector repairing

I started to check the surrounding components, and everything was ok. Next I searched on the internet for more details about MQ2 sensor.

mq2 sensor repair

According to the datasheet, the sensor should need 5V ± 0.1 to work and the heater resistance is about 33 Ohm-see the photo below:

mq2 sensor

You can check out the datasheet here. When I measured the voltage at the sensor, it was 4.9 V, so it was good, but when I checked with ohmmeter the heater resistance, it gave me 0 ohm. Yes, I found the culprit!

Next I bought the sensor and replaced it and the Gas detector came back to life again.

mq2 sensor

gas detector repaired

This article was prepared for you by Mihai Mazarus from Brasov Romania. He works in a copyshop and his hobby is electronics repair.

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  1. asim

    August 25, 2015 at 9:50 pm


  2. George

    August 25, 2015 at 10:21 pm

    Looking at the solder joints in the middle of the rear of the circuit card they look pretty bad. Overheated maybe? I assume they were corrected when the sensor was swapped.

    • Anthony

      August 26, 2015 at 5:33 am

      I certainly agree on that observation with you George !

    • Mihaii

      August 26, 2015 at 7:10 pm

      You are right George, i correct the problem.

  3. yogesh Panchal

    August 26, 2015 at 12:12 am

    Good attempt thanks for sharing.

  4. Corriete

    August 26, 2015 at 3:02 am

    yes like this one.good job

  5. Robert Calk

    August 26, 2015 at 5:49 am

    Good job, Mihai. Thanks for the article.

  6. Gautam

    August 26, 2015 at 9:58 am

    Most of the faults are detected by keen observation of the component's it self. Weldon dear.

  7. Gurpreet

    August 26, 2015 at 1:11 pm


    Somewhat different but good job. Thanks for the article.

  8. Kushan

    August 26, 2015 at 2:52 pm

    Good job! congratulation! Can a MQ2 sensor be reused ? (after detecting GAS one time) ?


  9. Mihai

    August 26, 2015 at 7:20 pm

    Thank you for everyone ! No, the sensor is used for more times, sometimes it fail.This gas detector it works perfectly about 5 years.

  10. Mihai

    August 26, 2015 at 7:42 pm

    Thank you far comments ! the sensor is not single use only.

  11. Chris

    August 27, 2015 at 7:00 pm

    Miha well done job!
    My best regards.


    August 29, 2015 at 1:34 am

    good can you provide gas detector circuit diagram. to make a mini project

  13. Mihai

    August 29, 2015 at 4:29 pm

    Hi, Y RAMANJANEYULU, I'm sorry i don't have a circuit diagram because is no name detector, but you can find on google schematic diagrams, try to search for "mq2 arduino".


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