Confused, How to choose GAS detection sensor? Here this article gives detailed Information about gas sensors, it may fetch best GAS sensor to your Project design.
When we are search about gas sensors or detectors the first thing we get is MQ-XX series sensors. The MQ series of Gas sensors are used to detect different Gas forms. Basically every MQ sensors has one Heater inside with an electro-chemical sensor. They are best to smell Gas in indoors at room temperature, by connecting load resistor as variable one we can calibrate the sensor gas detection sensitivity more or less.
The MQ series sensors gives analog output hence it can be easily driven by the Arduino development boards, some breakout boards with ADC gives Digital and Analog outputs.
How the Sensor to be connected?
Before get into the wiring of Gas sensor refer data sheet of that particular sensor, and follow wiring as per the instruction given in datasheet. Mostly the MQ series sensor can be connected as illustrated here.
Connect both A pins together and B pins together and apply +Vcc supply to the coupled A or B pins and apply Ground (Gnd) through variable load resistor (RL) to the remaining coupled A or B pins. Make sure that heater pins H & H connected with Vcc and Gnd. Don’t interconnect A and B pins or don’t make mistakes in the wiring if anything goes wrong the sensor could get damaged, Otherwise you are advised to use breakout boards.
The Heater and Load Resistor
The sensor operation is mainly depends on heater coil, the sensor heater uses 5V Dc supply otherwise PWM pulses from 2V to 5V amplitudes. Important thing is No H pins (heater) directly connected to the micro-controller or Arduino board because it draws much current .
The sensor get warm by using this heater and this time taken for warm is called as “burn-in time” it may upto 3 minutes for MQ sensors.
The Load Resistor at the output to ground may valued from 2KΩ to 47KΩ, when you connecting lower value it brings the less sensitivity, and the higher value gives good sensitivity but less accurate for higher concentration of Gas. The best practice is to make RL as variable resistor.
GAS sensor Pinout
Consider this MQ-XX series sensor, these are have 6 pins namely two heater pins, two A terminals and two B terminals.
Both upside and downside we can use A and B pins as stated in How the sensor to be connected.
Before considering the pins refer corresponding sensor datasheet.
List of GAS sensors
Here the list of Gas sensors given, according to your design need you can adopt suitable one.
|Name of Sensor||Sensitive For|
|MQ2||Sensitive for Methane- Butane-LPG- smoke.|
|MQ3||Sensitive for Alcohol- Ethanol- smoke.|
|MQ4||Sensitive for Methane- CNG Gas.|
|MQ5||Sensitive for Natural gas- LPG.|
|MQ6||Sensitive for LPG- butane gas.|
|MQ7||Sensitive for Carbon Monoxide.|
|MQ8||Sensitive for Hydrogen Gas.|
|MQ9||Sensitive for Carbon Monoxide- flammable gasses.|
|MQ131||Sensitive for Ozone.|
|MQ135||For Air Quality Sensitive for Benzene-Alcohol- smoke.|
|MQ136||Sensitive for Hydrogen Sulfide gas.|
|MQ137||Sensitive for Ammonia.|
|MQ138||Sensitive for Benzene-Toluene- Alcohol- Acetone- Propane- Formaldehyde gas- Hydrogen gas.|
|MQ214||Sensitive for Methane- Natural gas.|
|MQ216||Sensitive for Natural gas-Coal gas.|
How the Sensor Appears
Just for view here the appearance of Gas sensors are given.
This application circuit can be used for any MQ-xx series Gas sensors and it gives visual par graph for Gas concentration sensed by the sensor.