Binary Blink

What We Are Making

Turn a light on and off by pushing a button.

Bits We Need

• 
  LED
  A visual output for our circuit
• 
  Button
  An input, used to turn our light on and off
• 
  10k Resistor
  To regulate the voltage readings from the button
• 
  Wires
  To connect everything together!

LED Overview

Setting up our LED will 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 Button
  On-screen button, sends message
  that light should turn on.
• 
  Light Output
  Converts test button message
  into an Arduino signal.

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 on and stay on.

Button Overview

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

Physical Components
of the Button Circuit

Set up your button as in the diagram.

Logical Components
of the Button Circuit

• 
  Button 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 and configure it.

Connect the nodes

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

Deploy Your Code

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

Test the Button Input

Press your button down and up again.

You should see the debug message in your browser.

Logical Components
of the whole circuit

• 
  Button Input
  Receives an Arduino signal
  as a JavaScript message.
• 
  Conversion Function
  Converts the button signal
  into the correct message
  for the LED.
• 
  LED Output
  Sends the JavaScript message
  as an Arduino signal.

Circuit Arduino Nodes

Link the Arduino input and output directly.

The LED should be on when the button is pressed down.

Conversion Function

Link a function between the in node and the out node,
so we can manipulate the value being passed along.

Function Code

var buttonPressed = msg.payload;
var lightOn = context.lightOn;

if(lightOn === undefined) {
    lightOn = false;
}

if(buttonPressed === true) {
    if(lightOn === true) {
      lightOn = false;
    } else {
      lightOn = true;
    }
}

context.lightOn = lightOn;
msg.payload = lightOn;

return msg;

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

Shorter Function Code

var buttonPressed = msg.payload;
var lightOn = context.lightOn || false;

if(buttonPressed) {
    lightOn = !lightOn;
}

context.lightOn = lightOn;
msg.payload = lightOn;

return msg;

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.

Test your circuit

Your button should now act like an on/off switch

Challenge: Stop and Go

Add a green LED to your circuit to make a stop/go light.