ex02

Exercise 2

This exercise makes use of array to turn ON and OFF multiple LEDs in sequence.

Schematic Description

Components and Connections

Component	Pin/Connection	Arduino Pin	Description
LEDs (5x)	Anode	9, 10, 11, 12, 13	Indicates sequence by turning ON and OFF in an order defined by the programme logic.
	Cathode	GND (via Resistor)	Connects to ground through a 220Ω resistor to limit current.

Schematic Description Table

Connection	Pin	Purpose
LEDs to Arduino	9, 10, 11, 12, 13	Controls the ON/OFF state of LEDs in a sequence as programmed in the code.
LEDs to Ground (via Resistors)	GND	Ensures safe operation of LEDs by limiting current with resistors.

Code

// define constants
const int led_pins[] = {9, 10, 11, 12, 13};         // array of LED pins
const int no_pins = sizeof(led_pins) / sizeof(int); // number of pins
const int between_HL = 250;                         // milliseconds between ON and OFF

// initialisation
void setup()
{
    // set the digital pins as outputs using a for loop
    for (int cnt = 0; cnt < no_pins; cnt++)
    {
        pinMode(led_pins[cnt], OUTPUT);
        digitalWrite(led_pins[cnt], LOW);
    }
}

// main loop function
void loop()
{
    // turn the leds ON and OFF from first to last
    for (int cnt = 0; cnt < no_pins; cnt++)
    {
        digitalWrite(led_pins[cnt], HIGH); // turn the LED on
        delay(between_HL);                 // wait for a second
        digitalWrite(led_pins[cnt], HIGH); // turn the LED off
        delay(between_HL);                 // wait for a second
    }

    // turn the leds ON and OFF from last to first
    for (int cnt = no_pins - 2; cnt >= 1; cnt--)
    {
        digitalWrite(led_pins[cnt], HIGH); // turn the LED on
        delay(between_HL);                 // wait for a second
        digitalWrite(led_pins[cnt], HIGH); // turn the LED off
        delay(between_HL);                 // wait for a second
    }
}

Exercise Steps

1. Connect the LEDs:

   • Connect five LEDs to digital pins 9, 10, 11, 12, and 13 on the Arduino.
   • Use appropriate resistors (e.g., 220Ω) in series with the LEDs to limit current.
   • Connect the cathode of each LED to the GND rail.

2. Upload the Arduino Code:

   • Copy the provided code for sequential LED blinking.
   • Open the Arduino IDE, paste the code, and upload it to the Arduino.

3. Observe LED Behaviour:

   • LEDs will turn ON and OFF in sequence from first to last and then from last to first.
   • Adjust the between_HL constant in the code if needed to modify the delay between LED toggling.

4. Experiment and Modify:

   • Experiment with adding more LEDs or changing the sequence logic in the code.