Make: Volume 78

• SENSIRION SCD30 is a nondispersive infrared

(NDIR) optical sensor that costs about $50.Shown

in Figures

C

and

D

, this Swiss-made sensor

has two channels or tubes that use infrared light

to detect CO

2

in the air. The infrared light that's

emitted is absorbed by the CO

2

molecules. “The

more CO

2

in the tube, the less infrared light is

detected,” said Guido.The SCD-30 also measures

temperature and humidity. It’s available on

breakout boards including Seeed’s Grove and

Adafruit’s Feather format.

• SENSIRION SCD40 is a newer, miniature

photoacoustic CO

2

sensor. It’s not dual channel,

so it might show a bit more drift in the long run,

but it’s mor ...