Got a DHT22 humidity sensor recently, was pretty easy to get up and running.

Since moving to the new place i’d been having issues with sinus headaches, probably due to low humidity. I got a cheapo humidifier, but it did not do so well.

I finally got an industrial strength humidifier, a CM-6009, and wanted to both see what the humidity is, and how well the humidifier is working.

Busted out my logic analyser for pretty much the first time ever, the timing was pretty close to as indicated in the datasheet.

Zooming in, the short high pulses are ~25us and the long high pulses are ~72.4us. The data sheet claims that the short pulses should be 26us-28us and the long pulses should be 80us, so these are a bit fast actually.

I used some really simple busy wait code to time the duration of the high periods (using loop_until_bit_is_set / loop_until_bit_clear), which works well enough. There is already publicly available code to use interrupt based methods that would be better.

For a first test I turned off my humidifier, and you can see the slow drop in RH over the next hour, with some sharper drops roughly tied to when the AC turns on. I also quickly learned my humidifier is set way higher than I thought it was… 70% is a bit high.

Looks like AC is my main problem, it is continuing to get drier. Once I see how low it drops I’ll turn the humidifier back on to get the recovery rate.