MQ-2 smoke sensor module

This is the MQ-2 smoke sensor module. It is sensitive to flammable gases such as LPG, propane, and methane.

Find our tutorial here

It has four pins:

AO: Analog Output

DO: Digital Output

GND: In electronics, we define a point in a circuit to be a kind of zero volts or 0V reference point, on which to base all other voltage measurements. This point is called  ground or GND.

3.3V  : While 'VCC' stands for Voltage Common Collector, we'll connect the VCC pin to 3.3V on the micro:bit

Voltage is the difference in potential between two points. As it is difficult to talk about voltage without a reference point, we need another point to compare it to.