Tutorial 4: Arduino Knight Rider

Created on: 31 July 2012

In this tutorial, eight LEDs are interfaced to the Arduino Uno board. This is not complicated – it is just like interfacing a single LED to the Arduino as done in tutorial 3, but eight times over. A program is then loaded to the Arduino that will turn the eight LEDs into a "Knight rider" display, also known as an LED chaser.

The following video shows what you will achieve:

Prerequisites

You will need to have completed tutorial 3 and its prerequisites before attempting this tutorial.

Components

Besides a breadboard, Arduino Uno and USB cable, you will need:

Qty	Part	Designator	Notes	Type
8	470 ohm resistor (yellow - violet - brown)	R1	1/4W, 5% or better	Resistors
8	5mm red LED	D1	Other coloured and sized LEDs could also be used, e.g. 3mm green LED	Semiconductors
9	Wire links		Wire links that will reach from the breadboard to the Arduino	Wire

Circuit Diagram

The circuit diagram is shown below. It is simply eight LEDs interfaced to the Arduino pins 2 to 9.

Building the Circuit

Place the LEDs next to each other in the breadboard so that the anode (longer lead) is at the left and the cathode is on the right.

Insert the 470 ohm resistors connecting one lead to the LED's cathode and the other to the top rail.

Join the anodes of the LEDs to pins 2 to 9 of the Arduino from left to right using single-core wire. Join the top rail to one of the GND pins of the Arduino.

When finished building the circuit, connect the Arduino to the PC via the USB cable.

Loading the Program

The Knight Rider program listing is shown below. Copy it and pasted it into the Arduino IDE.

/*
  Knight Rider
  
  Knight rider display on 8 LEDs
*/

void setup() {
    // set up pins 2 to 9 as outputs
    for (int i = 2; i < 10; i++) {
        pinMode(i, OUTPUT);
    }
}

// function to switch all LEDs off
void allLEDsOff(void)
{
    for (int i = 2; i < 10; i++) {
        digitalWrite(i, LOW);
    }
}

void loop() {
    // move on LED to the right
    for (int i = 2; i < 9; i++) {
        allLEDsOff();
        digitalWrite(i, HIGH);
        delay(200);
    }
    // move on LED to the left
     for (int i = 9; i > 2; i--) {
        allLEDsOff();
        digitalWrite(i, HIGH);
        delay(200);
    }
}

Load the program to the Arduino and if the circuit was built correctly, your knight rider circuit will start operating.

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