Spectrum Spinner

What We Are Making

Change the colour of a light by turning a dial.

Bits We Need

• 
  RGB LED
  A visual output for our circuit
• 
  Potentiometer
  A dial which outputs a range of values
• 
  3x 330Ω Resistor
  To regulate the voltage to the LED
• 
  Wires
  To connect everything together!

LED Overview

Setting up our LED will once again consist of two parts:
the physical components, and the logical components

Physical Components
of the LED Circuit

Set up your LED as in the diagram.

Logical Components
of the LED Circuit

• 
  Test Buttons
  On-screen buttons, one for each
  LED colour component.
• 
  Light Output
  One Arduino pin output for each
  LED colour component.

Pass a Message Out to the Arduino

Drag an arduino out node into your workspace and configure it.

Inject a Message

Drag an inject node into your workspace and configure it.

Connect the nodes

Click and drag the small square on the inject node,
and attach it to the arduino out node.

Deploy Your Code

Click the “Deploy” button in Node Red
to link your logic flow with the Arduino.

Test the LED Output

Click the square trigger button on the inject node.

Your LED should turn red.

Test Green and Blue

Add two more flows to test the green and blue.

The test buttons should all work correctly.

Potentiometer Overview

Setting up our potentiometer will also consist of two parts:
the physical components, and the logical components

Physical Components
of the Potentiometer Circuit

Set up your potentiometer as in the diagram.

Logical Components
of the Potentiometer Circuit

• 
  Potentiometer Input
  Converts the Arduino signal
  into a JavaScript message.
• 
  Debug Logger
  Displays the JS message on
  the screen when received.

Receive a Message from the Arduino

Drag an arduino in node into your workspace and configure it.

Debug the Incoming Data

Drag a debug node into your workspace. The default configuration is fine.

Connect the nodes

Join your arduino node to your debug node.

Deploy Your Code

Click the “Deploy” button in Node Red
to link your logic flow with the Arduino.

Test the potentiometer input

Turn the dial on your potentiometer.

You should see value being logged in your debug panel.

Logical Components
of the whole circuit

• 
  Potentiometer Input
  Receives an Arduino signal
  as a JavaScript message.
• 
  Conversion Function
  Converts the potentiometer signal into the correct message for the LED.
• 
  LED Outputs
  Sends the JavaScript message
  as an Arduino signal.

Circuit Arduino Nodes

Link your arduino input to the three arduino output nodes
via a function, like we did last time.

This time your function requires three outputs instead of one.

Function Code

var dialValue = msg.payload;
var redOn = false;
var greenOn = false;
var blueOn = false;

if(dialValue < 300){
    redOn = true;
} else if(dialValue > 900) {
    blueOn = true;
} else {
    greenOn = true;
}

var redMessage = { payload: redOn };
var greenMessage = { payload: greenOn };
var blueMessage = { payload: blueOn };

return [redMessage, greenMessage, blueMessage];

Paste this code into your function config popup,
in the code editor section.

Shorter Function Code

var dialPosition = msg.payload;

var messages = [
    {payload: (dialPosition <= 300)}, // red
    {payload: (dialPosition > 300 && dialPosition < 900)}, // green
    {payload: (dialPosition >= 900)} //blue
]

return messages;

For experienced coders:
This code does exactly the same thing,
but is a bit shorter.

Deploy Your Code

Click the “Deploy” button in Node Red
to link your logic flow with the Arduino.

Full Circuit Test

Turn the dial to change the colour of your LED.

Your potentiometer should now act like a colour picker.

Challenge: Mood Lighting

Modify the conversion function to output 5 or more colours.

Bonus points: Fade the LED through a continuous spectrum.