Picture of Arduino LED Thermometer

This is my first project using an Arduino Uno as well as posting it on Instructables. I will do my best to make this instructable as clear and and to the point as possible.

I wanted to take a household object and add a temperature and LED sensor that would change the brightness of the LEDs as the temperature in the room changes.

To start here is a list of supplies I used:

Clear LEDs(x6) per LED $0.24) for pack of 25 LEDs $5.50)

1K OHM Resistor(x6) If you plan on doing other projects involving circuit boards I would suggest just purchasing a resistor and capacitor book from

Blank circuit board for final product

Solid Core Wire Its a good idea to use different colors for the Ground Wire (negative and commonly marked by black wire) and the Positive Wire (marked with red wire).

9v battery Can be found in most stores Target, Walmart and Radioshack but here is a link if you would rather order them. and also a case for the battery(optional)

Breadboard(optional) A breadboard is used for testing a circuit without the need for soldering.

Soldering Iron and solder Short Tutorial on soldering:Soldering

Glass Jar

Spray Paint Used to frost over the glass jar

Now for the more important components.

Multimeter Very useful tool, used for lots of different task a few being; testing to make sure your connection is getting power, can read the value of resistors and read the voltage left in a 9v battery and much more.

Arduino Uno Link:Arduino (link also up top) Cable amazon.comfor Arduino Link:

DHT22 Temperature/Humidity Sensor I choose not to implement humidity in this project however you can have the LEDs change as the humidity changes the same way as they do for the temperature, which will be explained in the code later on. Adafruit also sells a wired sensor with a resistor built in. I originally used that sensor but ran into overheating issues.

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earton7 months ago

I hope to make this, does the code need changing if I used coloured LEDs (blue for cold red for hot etc). Thanks, I am a beginner!

pmt4 (author)  earton7 months ago
In one of my test I had different colored LEDs and one issue I ran into was when the temp dropped and the lights were suppose to fade back down they didn't. I think it had something to do with the LEDs having different voltages. My original project plan was to use RGB LEDs that changed colors as the temp changed I'm currently working on those and will post an update.