See the new BME280 combination Temperature, Humidity, AND Barometric Pressure Sensor all in one!
6/2/2015 See the new WiFi Version! - http://arduinotronics.blogspot.com/2015/06/wifi-we...
I wanted to set up a home web server that could monitor indoor and outdoor temperature, humidity levels, and even monitor for indoor freezing or flooding conditions (and other security, appliance or environmental alerts). The approach I took consists of a Arduino and a Ethernet shield, running a tiny web server sketch, and for this example, I'm using the popular DHT-11 Temperature / Humidity module. You can interface this to smoke / heat sensors, CO and other gas sensors, and a whole lot more.
For this example you will need:
Ethernet Shield (this could be done with wifi as well with some code changes)
DHT-11 Temp/Humidity Module
10k Ohm Resistor
Optional: BMP-085 Barometric Pressure Sensor
A internet router and home internet access
Step 1: The DHT-11 Temperature / Humidity Sensor
This little 4 pin sensor (only 3 are used) is an inexpensive and common sensor. It's easy to use and connect. Pin 1 connects to +5v, Pin 2 to an Arduino Input (we are using D2 on the Arduino), and pin 4 to Arduino Gnd. Since the Ethernet shield will stack on top of the Arduino, plug the DHT-11 into the same pins on the Ethernet shield.
The ethernet shield uses pins A0, A1, D4, and D10-D13
The DHT-11 is using D2, but can be changed.
The BMP180 uses A4 & A5.