DHT11/DHT21/DHT22 etc. Temperature & Humidity sensors
http://www.ladyada.net/learn/sensors/dht.html
http://dx.com/p/arduino-digital-temperature-humidity-sensor-module-121350
The sensor module is including resistive humidity sensing component and NTC temperature testing. The compatible digital temperature humidity sensor module is component and connected with 8-byte MCU. This is useful module is fast response, great anti-interference ability and durable.
- Black panel - Sensor including resistive humidity sensing component and NTC temperature testing component and connect with 8-byte MCU - Fast response, great anti-interference ability and durable - Signal transmission range: 20m - Power: 5V - Temperature range: 0-50'C - Humidity range: 20-90%RH
"The sensor works fine. And the price it's very good. I can get the Temperature, % humidity and the Dew Point for the combination of Temperature and % Humidity. You can only need 3 wires: S=> signal, - => GND, 5V (central pin). There are a lot of examples in internet, you can only look for DHT11 and download the library to Arduino."
"Easy enough to wire up - the middle pin didnt appear to be labelled but S is signal and - is ground so the middle one must be power, I think it can take 3.3V or 5V in"
"You can find istruction on Adafruit to connect to raspberry pi and this item have the resistor 4,5k on the data pin so you can connect directly to raspberry without any problem, and the price is low than the single dth11 component"