instructions.md

Blink

Blink an LED

Bits you'll need

• 1 x Arduino
• 1 x power
• 1 x bargraph

If you don't have a bargraph, use an alternative LED bit instead e.g. LED, Long LED or Bright LED.

Assembling the circuit

Connect power bit to d0 on Arduino bit, d5 on Arduino bit to bargraph (or LED) bit.

Code

var five = require("johnny-five"), 
  board, led;

board = new five.Board();

board.on("ready", function() {
  led = new five.Led(5);
  led.strobe( 1000 );
  this.repl.inject({
    led: led
  });
});

You can find a copy of this code in blink/blink.js

Notice how we have included the johnny-five framework using a require statement at the start of our program:

var five = require("johnny-five")

We can access the framework using the five variable throughout our program. We've also declared other variables that we will use (board and led) at the start of our program.

In all of our programs, we'll first create a board object to correspond to our Arduino, and then wait for the board to be ready before we start working with our input and output modules:

board = new five.Board();

board.on("ready", function() {
  // code to work with inputs and outputs goes here
  // it will run only after the board has started up and is ready to go
});

Run the code from the terminal e.g.

node blink/blink.js

What you'll see

A Light Emitting Diode (LED) converts electrical energy into light. We've created an Led object to control our LED module attached to pin 5.

led = new five.Led(5);

The strobe method blinks the LED module on and off by varying the signal on the I/O pin to which the LED is connected between on (5V) and off. We specify the blink delay in milliseconds as a parameter:

led.strobe( 1000 );

All of the LEDs in the bargraph will blink on and off together, once per second (1000 milliseconds).

What to try

Johnny-Five provides a REPL (Read-Eval-Print Loop) where you can type in commands to take effect immediately. So that we can control our LED module interactively, we inject our led object into the REPL:

this.repl.inject({
    led: led
});

From the REPL prompt try the following commands:

led.stop()    // stop blinking or pulsing
led.off()     // turn led off
led.on()      // turn led on
led.pulse()   // pulse the led
led.fadeIn()  // fade to full brightness
led.fadeOut() // fade to off

Hit control plus d on a new line in the REPL to exit and terminate the program.