I am investigating the timing of the DHT (11,21,22) sensor.
Problem description:
I implemented a DHTlib - Arduino Playground - DHTLib - which works quite well. Yesterday I started to investigate some timing aspects and I saw that to read the DHT22 sensor I used on average 24-25 milliseconds from which 20 milliseconds was a delay to wake up the sensor (from low power mode). This is 80% of the (blocking) time needed. Clocking in the 40 databits take 40*80-120usec= 3200-5000 usec.
The DHT11 and DHT22 documentation says 18 millis at least, the DHT21 documentation states 1 millisec at least. That could be a typo?
Experiment:
I have patched my library to use smaller delays than specified and I ended up (for now) with a wake up delay of 1 millisecond. This works well for for a 16Mhz UNO, DHT22 with 10 cm wires.
Question:
Has anyone done similar experiments with a DHT11, 21 or 22?
If so what are your results?