Build Instructions

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• 1

  Wire up the LCD

  I happened to have an unused Adafruit RGB backlight positive LCD 16x2 handy, so I soldered on the headers, then followed their wiring guide to ensure everything was working. The particular LCD that I'm using is RGB-backlit, but to keep the project somewhat generic and applicable to standard single-color displays, I resisted the urge to get fancy, and only wired up the R(ed). There's quite a bit of wiring required, with 12 of the 16 pins populated on the standard LCD (the RGB adds another two pins for controlling green and blue). The Adafruit tutorial has an excellent description of how to hook it up, as well as what each pin does, but here's a cheat sheet so that you can check your work, or skip the long version:

  1    GND
  2    +5V
  3    contrast pot wiper (with other sides of pot connected to GND and +5V respectively)
  4    Arduino D7
  5    GND
  6    Arduino D8
  
  11    Arduino D9
  12    Arduino D10
  13    Arduino D11
  14    Arduino D12
  15    +5V
  16    GND
  

• 2

  Test the LCD

  Once you've got the LCD wired up, it's a good idea to give it a quick test before proceeding, so grab the built in HelloWorld example from File->Examples->LiquidCrystal. The Adafruit tutorial uses different pins than the Arduino default, so we'll need to tweak the code slightly; instead of:
  

  const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
  LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
  

  we need:

  LiquidCrystal lcd(7, 8, 9, 10, 11, 12);
  

  for the way we wired it. Compile and Upload the sketch, and you should see a lovely hello, world! on your LCD. If not, hit me up in the comments and I'll try to help you figure out what went wrong! 💙

• 3

  Add the DHT11

  
  Now that we know the LCD is working, let's have a look at the temperature. I'm using the commonly available, inexpensive, DHT11. It's not the fastest or most accurate way to measure temperature, but it's cheap, and good enough for our purposes. Hook the middle (out) pin on the DHT11 to digital pin 2 on the Arduino, and the + and - pins to 5V and GND respectively. You'll need to install the Adafruit DHT sensor library as well as its dependency, the Adafruit Unified Sensor library - if you've not done this before, Adafruit has an excellent walk-through. With the libraries installed, we can run another quick test sketch like we did for the LCD: open File->Examples->DHT->DHTtester and uncomment this line (15 at the time of writing) by removing the leading forward slashes:

  #define DHTTYPE DHT11   // DHT 11
  

  
  

  then comment out this line (16) by prefixing it with two forward slashes:

  //#define DHTTYPE DHT22   // DHT 22  (AM2302), AM2321

  
  

  and give it a quick Compile. If you run it, chances are you won't see the expected output on the serial monitor, but as long as it compiled OK, we should be good for now.

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