I am trying to build a networked smoke & gas detector. I got a few MQ-2 sensors to hook up to my Arduino (Uno with WiFi Shield) via my breadboard.
My local suppliers didn’t have the ones with the breakout boards so I have the “raw” 6-pin sensors.
I have gone through the data sheet (http://www.pololu.com/file/0J309/MQ2.pdf) as best I can. I have also looked at the Arduino Playground page (http://playground.arduino.cc//Main/MQGasSensors) as regards the sensors and tried to follow that as best as I can. I have also looked at some video examples. But they all seem to be using breakout boards for their connections…
But I am lost in the wiring. Basically I see there are 2x A pins, 2x B pins and 2x H pins. My understanding is that I should be connecting the two A pins together, the two B pins together and the 2 H pins together. My assumption therefore was to run two wires from the two A pins to two holes in the breadboard but in the same column, two wires from the two B pins to a same column in the breadboard and two wires from the two H pins to a same column in the breadboard. I would then run one wire from the A pin column in the breadboard to the Arduino, one from the B pin column to the Arduino and one from the H pin column to the Arduino (ie 3 wires from the breadboard to the Arduino).
The sensor appears to take 5V directly and I am going to need to add a load resistor (from 2kOhm to 47kOhm) connected to the ground part of the circuit.
My basic problem is that I can’t decipher which of the sensor pins goes where. I believe one of the pins goes to the 5V, one goes to GND and one goes to an analog input port such as A0. But I don’t know which pin (pair - column) corresponds to each of these.
From the Playground page I believe the A pins go to the 5V. But I’m not sure. I then don’t know which goes to the GND (B pins or H pins). Whichever goes to GND then gets the resistor between it and the GND on the Arduino and the other pin pair goes to A0.
Any ideas or suggestions?