Wifi Sensor Modules

Materials (for 1 sensor module):

• ESP8266 NodeMCU 12e Board  (Arduino-compatible development board with Wifi connectivity)
• DHT22 Temperature/Humidity Sensor (Arduino-compatible temp/humidity sensor. It's got better temperature resolution than the cheaper DHT11, and a larger working range for temp and humidity measurements)

Software:

• Arduino IDE
  • ESP8266 NodeMCU 12e board libraries need to be installed.
  • ESP8266Wifi library, ThingSpeak library, and DHT libarary need to be installed
• ​ThingSpeak.com
  • ​Set up ThingSpeak channels with several fiel
• Mobile Phone App
  • I wanted to be able to check on my sensors frome anywhere with an internet connection. Luckily there are many to choose from on Android.

Results:

• Hardware:
  • The actual board and sensor setup is easy. My sensors have built-in pullup resistors in them, so I can directly connect them to the power and GPIO pins of the ESP8266 dev board.
  • I made a quick cardboard housing for the sensors. There is a bright blue LED that blinks every time the sensor data is read, and the housing suppresses that light.

Schematic of the circuit

ESP8266 NodeMCU 12e dev board connected to a DHT22 temp/humidity sensor.

The whole board with a cardboard housing to seal it up. This keeps the (very) bright blue activity light from blinking all night!

• My main ThingSpeak channel is public. Take a look!
  • ​I set up ThingSpeak channels with several fields.
    • Due to quotas on how fast you can write to ThingSpeak (every 15 seconds per channel), I set up 1 channel per sensor.
    • Each sensor channel has 3 fields (temp, humidity,  and an error channel).
    • This allows me to write data from many sensors simultaneously without worrying about timing issues.
  • Each channel generates unique API Keys that can be used to read and write data.
  • ThingSpeak integrates MATLAB functionality directly, so I set up a triggered event to pull the sensor data from all of the different sensor channels, calculate the average, then put the  all of this information in another channel (my main channel).
• Mobile Phone Apps Galore!
  • Android: there are a ton of free apps that allow you to view data from ThingSpeak
    • ThingView App
    • IoT ThingSpeak Monitor Widgit
    • At least 3 others with "ThingSpeak" in the title, and many others with compatibillity​​
  • iPhone: there are no official Apple options that I know of. Sorry apple fanboys, you're out of luck!