Arduino Blink Three LEDs

In this lab, we will learn how to make three LEDs of different color blink on and off. We will be replicating the same blink circuit in the prior lab for a red, a green and a blue LED.

LED Connections

The LED circuit is below. Just like the blink lab, each LED will have a black wire from the cathode of the LED to GND. The Anode of each LED will go through a resistor before it connects to one of the Arduino digital output pins. We will be using pin 13, 12 and 11 (left to right) on the Arduino.

Here is a picture of red, green, blue LED circuit.

Circuit Diagram

Here is the circuit diagram we will use for our blink lab.

Code

The Setup Function

Our setup function will be similar to the blink lab except instead of just one output pin, we will have three. The pins are 13, 12 and 11.

void setup()
{
  pinMode(13, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(11, OUTPUT);
}

The Loop Function

The loop function will first turn on and off the red LED on pin 13, just like in the blink lab. We can then copy and paste the four lines of code right after itself to control the red LED on pin 12. After we paste code in we will need to change the pin number from 13 to 12. We will repeat this process and copy and paste four lines for pin 11, the blue pin.

void loop()
{
  // turn the red LED on pin 13 on and off
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000);

  // turn the green LED on pin 12 on and off
  digitalWrite(12, HIGH);
  delay(1000);
  digitalWrite(12, LOW);
  delay(1000);

  // turn the blue LED on pin 11 on and off
  digitalWrite(11, HIGH);
  delay(1000);
  digitalWrite(11, LOW);
  delay(1000);
}

The Full Program

Here is the full program:

void setup()
{
  pinMode(13, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(11, OUTPUT);
}

void loop()
{
  // turn the red LED on pin 13 on and off
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000);

  // turn the green LED on pin 12 on and off
  digitalWrite(12, HIGH);
  delay(1000);
  digitalWrite(12, LOW);
  delay(1000);

  // turn the blue LED on pin 11 on and off
  digitalWrite(11, HIGH);
  delay(1000);
  digitalWrite(11, LOW);
  delay(1000);
}

You can type this into the Tinkercad program or do a copy here and paste it into the code area.

Working example on Tinkercad

Blink Three LEDs

Experiments

1. When the first LED turns off there is a pause of one second before the second gree LED turns on. How would you change the loop() function so that immediately after the first red LED goes off the second green LED goes on?
2. How many places in the program do you have to change to make pattern speed up or slow down? Could you use a variable to allow you to make a change at a single location in the program to adjust the speed?