AirNest

The X axis on all charts shows the exact reading time (hours : minutes : seconds). The Y axis on the gas sensor charts is measured in ppm (parts per million). Temperature uses °C and humidity uses %.

To keep the charts readable, each gas sensor has a maximum display cap: MQ-135, MQ-6, and MQ-8 are capped at 10,000 ppm, MQ-7 at 2,000 ppm, and MQ-3 at 500 ppm. Readings above these limits are recorded in the database but will not be fully visible in the chart view.

The periodic occurrence of sudden spikes within the sensor readings is caused by the fact that the MQ series gas sensors need a time to heat up before providing stable output values. Since AirNest is a prototype project, the station had to be restarted several times during its development to run tests and calibrations. Such restarts always result in the restart of the heating process. When it comes to the DHT11 readings (temperature and humidity), the sudden drops were caused by either faulty connection, or the sensor picking upt the heat from the others (solved by moving the DHT11 further away). The process was important for debugging both hardware and software aspects.

The sound chart has two separate lines and two Y axes. The purple line — Background voltage (V) (left axis) reflects the sustained ambient sound level measured by the KY-037 analogue output. The orange line — Events per 30-min session (right axis) counts the number of distinct sound events detected by the digital interrupt during each 30-minute reading session. A higher event count means more sudden sound spikes occurred in that window.