ETHERNET TERMO-HYGROMETER with ARDUINO


The device is measuring ambient temperature and humidity. It can be connected to an LAN through Ethernet port and allows data reading on a simple web page.
The project requires an Arduino board with Ethernet shield, a digital temperature and humidity sensor SHT75 or SHT71 and a 4.7kOhm pull up resistor.
Information on the Arduino hardware and its programming IDE (Integrated Development Environment) is widely available on Internet and it is out of the scope of this page.
A system similar to the one described here could also be realized with cheaper sensors compared to SHT75 (like DHT22). However, when using those sensors, I experienced severe and not reversible saturation problems in outdoor environments where 100% relative humidity condition can last for hours.
In case you'd like to realize a cheaper system for indoor conditions, not facing high humidity levels, I can provide you with the connection scheme for DHT22 sensor together with the Arduino code. Just contact me.
Connections among the components Arduino and SHT7x sensor can be realized as per the picture below. The sensor require a connection with two digital pins (Serial Data and Serial Clock) in addition to Source Voltage and Ground. Source voltage of 3.3V is recommended but 5V can also be used and might be beneficial if a longer wire is used.




The code for Arduino realizes a very simple web server. When directly connecting to the Arduino board with its IP address and an optional TCP port (http://arduino_address[:port]) you get an answer with a simple text summarizing temperature, humidity and calculated dew point data:



Pure temperature, humidity and due point figures can also be retrieved at respective addresses (http://arduino_address[:port]/temperature, http://arduino_address[:port]/humidity and http://arduino_address[:port]/dewpoint).
The source code for the Arduino board is shown here below.
Local network settings should of course be changed according to the LAN the Arduino will be connected to.
Before compiling with Arduino IDE, you've to download from the Internet Sensirion libraries and load them into the IDE with the Library Manager.
A copy of library file is also included in the archive with all needed project files available for download.

Arduino_SHT75_temperature_humidity_webserver.ino:


All files needed to realize this system can be downloaded at this link.


"Arduino", "SHT75", "SHT71", "DHT22" and other brands mentioned in these pages are trademarks of their respective owners.