Gas detector circuit using OPAMP

Gas detector circuit using OPAMP

A Smoke Detector is a smoke sensing device that smokes presence. Smoke Detectors are very commonly used in offices, schools, homes and industries.

Smoke detectors and smoke alarms are very cheap as its usage is high and cost of production is low. In this project, we are making a simple Smoke Detector Circuit using operational amplifier.

Circuit diagram:

Component required:

  • MQ-2 Sensor
  • LM358
  • 10KΩ
  • 330Ω
  • LED
  • 0.1µF
  • 10KΩ POT

 

Working:

In our smoke detector circuit LM358 acts as a comparator. It is connected to POT so that the sensitivity of the circuit can be adjusted.

 

 

We used a Smoke Sensor MQ-2 as the main sensory device. The working of the circuit is simple and is explained below.

Smoke Sensor MQ-2 is used as the main sensor. The working of the circuit is simple and is explained below.

When the smoke is not present, the conductivity between the electrodes is less, as the resistance is in the order of 50KΩ. The inverting terminal input of comparator is higher than the non-inverting terminal input. The indicator LED is OFF.

When the sensor gets in contact with smoke, the resistance of the sensor falls to 5KΩ and the conductivity between the electrodes increases.

This provides a higher input at the non-inverting terminal of comparator than the inverting terminal and the output of comparator is high. The alarming LED is turned ON as an indication of presence of smoke

 

Application:

  • Smoke or fire detector in offices and factories.