Wifi sensor

Recently I stumbled upon a 5EUR embedded WiFi module: ESP8266-01. Because it is cheap, can be used by some simple AT-command via an UART and the documentation in the interwebs isn’t that bad I decided to order a bunch together with some 3.3V/8Mhz Arduino Pro Mini clones.

The plan was to do some temperature and humidity readings with the DHT11 sensors I had laying around.

When finally playing with the ESP8266 and looking at the documentation I discovered a project which provides a plugin to the Arduino-IDE which enables you to run your software on the actual ESP8266. Therefore no ‘extra’ Arduino was needed to build my sensor node.

And even better: somebody at Adafruit had already done nearly the same thing I wanted to do…

Because I want to run several sensors I changed the software a little bit:

  • The sensors measure every minute and then push their measurements to a simple PHP-script on the home server.
  • The home server stores the sensor data in a MariaDB.
  • Another simple PHP-script delivers the data as JSON and it can be displayed in a HTML-page using flot-charts.

The prototype:

IMG_20150627_214711

The schematics:

WifiSensor_Schaltplan

And the result:

IMG_20150627_213924

chart

Conclusion:

The setup works and is really simple to build and setup. The humidity reading of the DHT11 sensors seems not very accurate. The values jump around between measurements and I used a sliding average of 10 values to create the chart above.

I’m thinking about buying some of these BME280 boards from Watterott to replace the DHT11.