Introduction: RGB LED Temperature Indicator

Picture of RGB LED Temperature Indicator

Recently, the AC has been broken, and I've been very curious as too how how an environment can get before it begins impeding my thought process. I wanted a quick indication that tells me if the temperature is freezing, cool, mild, or searing hot, so I decided to make an RGB LED temperature indicator.

In this project the LED will change colours from blue to cyan to green to yellow to pink to red, depending on the temperature of the surrounding environment, with blue indication very cold and red indication very hot.

Step 1: Tools and Materials

Picture of Tools and Materials

  • Arduino 101 or Arduino Uno
  • RGB LED
  • 3 pieces of 100Ω Resistor
  • Temperature Sensor - TMP36
  • Jumper Wires

Step 2: Circuitry

Picture of Circuitry

Connecting the Arduino Power to the Breadboard. Both the temperature sensor and the RGB LED would require to be connected to a common ground and 3.3V so we will use the breadboard power rails.

  • Connect the 3.3V pin from the Arduino to the red power rail on the breadboard with a red jumper cable.
  • Connect the GND pin from the Arduino the black power rail on the breadboard with a black jumper cable.

Wiring the Temperature sensor to the Arduino

  • Connect the bottom-most pin of the temperature sensor with the flat side facing right, to 3.3V on the red power rail of the breadboard
  • Connect the top-most pin of the temperature sensor to the common ground on the black power rail of the breadboard
  • Connect the middle pin to the analog pin A0 of the Arduino .

Lastly, wiring the RGB LED to the Arduino

  • Connect the longest pin of the RGB LED to the common ground on the black power rail of the breadboard.
  • Then, connect each of the three other pins from the pin on the edge closest to ground (this is the red LED pin) to a 100Ω resistor in series to pins 5, 6, and 9 on the Arduino, respectively.

Step 3: Code

Picture of Code

//create constants for the three analog input pins

const int redPot = 0; const int greenPot = 1; const int bluePot = 2;

//create constants for the three RGB pulse width pins const int redPin = 5; const int greenPin = 6; const int bluePin = 9;

//create variables to store the red, green and blue values int redVal; int greenVal; int blueVal;

void setup() { //set the RGB pins as outputs pinMode(redPin, OUTPUT); pinMode(greenPin, OUTPUT); pinMode(bluePin, OUTPUT); }

void loop() { //read the three analog input pins and store their value to the color variables redVal = analogRead(redPot); greenVal = analogRead(greenPot); blueVal = analogRead(bluePot);

//use the map() function to scale the 10 bit (0-1023) analog input value to an 8 bit //(0-255) PWM, or analogWrite() signal. Then store the new mapped value back in the //color variable

redVal = map(redVal, 0, 1023, 0, 255); greenVal = map(greenVal, 0, 1023, 0, 255); blueVal = map(blueVal, 0, 1023, 0, 255);

// use the analogWrite() function to write the color values to their respective // RGB pins. analogWrite(redPin, redVal); analogWrite(greenPin, greenVal); analogWrite(bluePin, blueVal); }

Step 4: Demo

Different temperature ranges will produce a different colour LED. Blue is used for very cold indoor temperatures, indicated for temperatures below 16 degrees, followed by cyan, green, yellow, pink/purple, then red for searing hot temperatures. When I touch the temperature sensor the colour changes to purple or red, depending on my body temperature.

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Bio: Aerospace Engineer working in Software Development with a passion for Hardware.
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