Handy project + write-up from Antonio Artimon up on Hackster.io.
DHT11 Temperature and Humidity sensor :
The DHT11 is a 4-pin (one pin is unused) temperature and humidity sensor capable of measuring 20% – 90% relative humidity and 0 to 50 °C. The sensor can operate between 3 and 5.5V DC and communicates using its own proprietary OneWire protocol. This protocol requires very precise timing in order to get the data from the sensor. The LOW and HIGH bits are coded on the wire by the length of time the signal is HIGH. The total time to take a reading is at most 23.4 ms. This includes an 18 ms delay required to start the data transfer and a window of up to 5.4 ms for the data. Individual signals can be as short as 20 μs and as long as 80 μs.
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