Driving Multiple LEDs — SIK Circuit 4

Make eight LEDs dance! Learn about arrays, for loops, and multiple output patterns including chase, ping-pong, marquee, and random blink effects.

Instructions

Parts & Introduction

This experiment uses 8 LEDs to create light patterns. You'll learn about arrays (grouping related variables) and for loops (repeating actions efficiently). The sketch includes 6 different animation functions you can try.

Parts Needed

1x Arduino Uno + USB cable
1x Breadboard
8x LEDs (any color)
8x 330Ω Resistors
9x Jumper Wires

Hardware Hookup

Wiring Instructions

Place 8 LEDs in a row on the breadboard.
For each LED, connect the negative leg (shorter) through a 330Ω resistor to GND.
Connect the positive leg (longer) of each LED to Arduino digital pins 2 through 9 (LED 1 = pin 2, LED 2 = pin 3, etc.).
Connect the GND rail on the breadboard to Arduino GND.

Tip: Keep the LEDs neatly spaced for the best visual effect.

Arduino Code

Open the Arduino IDE and upload the following sketch to your Arduino board.

multiple_leds.inoarduino

/*
SparkFun Inventor's Kit
Example sketch 04 — MULTIPLE LEDs

Make eight LEDs dance. Dance LEDs, dance!

Hardware connections:
  8 LEDs with 330 ohm resistors on pins 2-9.
  Negative sides through resistors to GND.

This code is completely free for any use.
*/

int ledPins[] = {2,3,4,5,6,7,8,9};

void setup()
{
  int index;
  for(index = 0; index <= 7; index++)
  {
    pinMode(ledPins[index], OUTPUT);
  }
}

void loop()
{
  oneAfterAnotherNoLoop();

  //oneAfterAnotherLoop();
  //oneOnAtATime();
  //pingPong();
  //marquee();
  //randomLED();
}

void oneAfterAnotherNoLoop()
{
  int delayTime = 100;

  digitalWrite(ledPins[0], HIGH); delay(delayTime);
  digitalWrite(ledPins[1], HIGH); delay(delayTime);
  digitalWrite(ledPins[2], HIGH); delay(delayTime);
  digitalWrite(ledPins[3], HIGH); delay(delayTime);
  digitalWrite(ledPins[4], HIGH); delay(delayTime);
  digitalWrite(ledPins[5], HIGH); delay(delayTime);
  digitalWrite(ledPins[6], HIGH); delay(delayTime);
  digitalWrite(ledPins[7], HIGH); delay(delayTime);

  digitalWrite(ledPins[7], LOW); delay(delayTime);
  digitalWrite(ledPins[6], LOW); delay(delayTime);
  digitalWrite(ledPins[5], LOW); delay(delayTime);
  digitalWrite(ledPins[4], LOW); delay(delayTime);
  digitalWrite(ledPins[3], LOW); delay(delayTime);
  digitalWrite(ledPins[2], LOW); delay(delayTime);
  digitalWrite(ledPins[1], LOW); delay(delayTime);
  digitalWrite(ledPins[0], LOW); delay(delayTime);
}

void oneAfterAnotherLoop()
{
  int index;
  int delayTime = 100;

  for(index = 0; index <= 7; index++)
  {
    digitalWrite(ledPins[index], HIGH);
    delay(delayTime);
  }
  for(index = 7; index >= 0; index--)
  {
    digitalWrite(ledPins[index], LOW);
    delay(delayTime);
  }
}

void oneOnAtATime()
{
  int index;
  int delayTime = 100;

  for(index = 0; index <= 7; index++)
  {
    digitalWrite(ledPins[index], HIGH);
    delay(delayTime);
    digitalWrite(ledPins[index], LOW);
  }
}

void pingPong()
{
  int index;
  int delayTime = 100;

  for(index = 0; index <= 7; index++)
  {
    digitalWrite(ledPins[index], HIGH);
    delay(delayTime);
    digitalWrite(ledPins[index], LOW);
  }
  for(index = 7; index >= 0; index--)
  {
    digitalWrite(ledPins[index], HIGH);
    delay(delayTime);
    digitalWrite(ledPins[index], LOW);
  }
}

void marquee()
{
  int index;
  int delayTime = 200;

  for(index = 0; index <= 3; index++)
  {
    digitalWrite(ledPins[index], HIGH);
    digitalWrite(ledPins[index+4], HIGH);
    delay(delayTime);
    digitalWrite(ledPins[index], LOW);
    digitalWrite(ledPins[index+4], LOW);
  }
}

void randomLED()
{
  int index;
  int delayTime = 100;

  index = random(8);
  digitalWrite(ledPins[index], HIGH);
  delay(delayTime);
  digitalWrite(ledPins[index], LOW);
}

Test & Experiment

What You Should See

All 8 LEDs light up one after another, then turn off in reverse order. This repeats continuously.

Troubleshooting

Some LEDs don't light: Easy to insert an LED backwards. Check polarity.
Out of sequence: With 8 wires, it's easy to cross a couple. Verify LED 1 is on pin 2, then each pin in order.
Starting fresh: Sometimes pulling everything out and re-wiring is faster than debugging.

Experiments to Try

Uncomment the other functions in loop() to try: oneOnAtATime(), pingPong(), marquee(), randomLED().
Create your own animation pattern!
Modify the delay times to change the speed.

Materials

•SparkFun Inventor's Kit - V3.2 - 1 kitNOK 999.20
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•Arduino Uno R3 - 1 piecePlaceholder
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•Breadboard - 1 piecePlaceholder
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•5mm LED - 8 piecessPlaceholder
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•330 Ohm Resistor - 8 piecessNOK 24.00
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•Jumper Wires - 9 piecessNOK 39.20
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Tools Required

Computer with Arduino IDE

CC0 Public Domain

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