Conversely, the comparator output and the connection to the Arduino’s analog converter (A0) are labeled nodes from the “Output and Labels” menu. The names are significant, including the spaces.

LPG gas sensor module's DO pin is directly connected to pin 18 (A4) of Arduino and Vcc and GND are connected to Vcc and GND of arduino. LPG gas sensor module consist a MQ3 sensor which detects LPG gas ...