Published March 11, 2016 © LGPL

Driving LEDs

Easy way to connect leds to Udoo Neo or any arduino board.

BeginnerFull instructions provided1 hour1,536

Things used in this project

Hardware components

UDOO NEO

Story

I find the ULN2803 very useful. It suits very well with the UDOO Neo board. You could easily use it with Linked It One or Arduino similar board.

In this example we are driving two standard 5 mm LEDs and two 5 mm RGB with positive common.

I've represented cables with standard colours. Red for positive, black for negative. Other colours are for driving signals.

The schematics for this components are:

This means that on the right side we get a negative current. If we want to light a LED, we need to put the "c" side against the negative side of the LED.

Code

Arduino array

int timer = 1000;        
int ledPins[] = { 
   5,6,7,8, 9, 10,11, 12 };       // an array of pin numbers to which LEDs are attached
int pinCount = 8;           // the number of pins (i.e. the length of the array)

void setup() {
  // the array elements are numbered from 0 to (pinCount - 1).
  // use a for loop to initialize each pin as an output:
  for (int thisPin = 0; thisPin < pinCount; thisPin++)  {
    pinMode(ledPins[thisPin], OUTPUT);      
  }
}

void loop() {
  // loop from the lowest pin to the highest:
  for (int thisPin = 0; thisPin < pinCount; thisPin++) { 
    digitalWrite(ledPins[thisPin], HIGH);   
    delay(timer);                  
    digitalWrite(ledPins[thisPin], LOW);    

  }

  // loop from the highest pin to the lowest:
  for (int thisPin = pinCount - 1; thisPin >= 0; thisPin--) { 
    digitalWrite(ledPins[thisPin], HIGH);
    delay(timer);
    digitalWrite(ledPins[thisPin], LOW);
  }
}