Design review: CO/NO2 Sensor

[krook]

Evaluate alternatives to the CJMCU-4514 currently in use to optimize for reliability and robustness.

The gas sensor used in the prototype is the CJMCU-4514, which is a breakout kit for the MICS-4514 sensor. Of course, in a productized solution, the design would be based on the MICS-4514 rather than the breakout.

The sensor itself appears to be of high quality from a reputable manufacturer. However, there are again concerns about its operating temperature. This one also must be exposed to the environment in some fashion, but it only safely operates to 85C.

It is possible that some active cooling solution would need to be incorporated in order to utilize this sensor directly.

High-temperature variants such as the VQ6MB from the same manufacturer do exist, but these are much more expensive, less available, and much larger.

Another alternative is the BME688 sensor, which also includes humidity measurements, which would possibly simplify the design because the humidity sensor could be entirely removed.

Care will need to be taken to choose an appropriate solution that meets the needs of the harsh environment and is cost-effective to manufacture.