Steam extractor

An extractor fan that clears the steam: a DHT22 (data GPIO4, 3.3 V, 10 kΩ pull-up) and a fan behind a high-trigger relay on GPIO26.

• humidity above 70 %: fan on
• once humidity is below 60 %, keep the fan running for another 3 s, then stop
• in between (60–70 %) nothing changes

The DHT22 gives a fresh reading at most every 2 s. The test bathroom is at 50 %, 85 % at 1 s (shower), 65 % at 4 s and 55 % at 7 s.

Budget: the Relay + fan kit with a loose DHT22 costs $20.25 — too much. Pick the cheaper half.