Color Changing LED Tree

Ever wanted an LED tree? Well now you can have your LED tree and eat it too (no, wait, you probably shouldn't)...

You will need:

1x ATtiny85
10x male header pins
Solid core wire, 2 colors
A bunch of LEDs

1x Arduino Uno to program the ATtiny

To prep the Arduino for programming the ATtiny, follow the guide on this page.

After you have done that, upload this sketch to the ATtiny.

//CODE STARTS HERE

//ATtiny85 RGB color fading tree

const int 2Pin = 2; 
const int 1Pin = 1; 
const int 0Pin = 0;


void setup()
{
  pinMode(2Pin, OUTPUT);    
  pinMode(1Pin, OUTPUT);    
  pinMode(0Pin, OUTPUT);
 
}

void loop() {
    2to21();
    21to1();
    1to10();
    10to0();
    0to02();
    02to2();
  }
 
void 2to21()
{
  digitalWrite(redPin, HIGH);
  digitalWrite(bluPin, LOW);

  // fade up green
  for(byte i=1; i<100; i++) {
    byte on  = i;
    byte off = 100-on;
    for( byte a=0; a<100; a++ ) {
      digitalWrite(grnPin, HIGH);
      delayMicroseconds(on);
      digitalWrite(grnPin, LOW);
      delayMicroseconds(off);
    }
  }
}



void 21to1()
{
  digitalWrite(grnPin, HIGH);
  digitalWrite(bluPin, LOW);

  // fade down red
  for(byte i=1; i<100; i++) {
    byte on  = 100-i;
    byte off = i;
    for( byte a=0; a<100; a++ ) {
      digitalWrite(redPin, HIGH);
      delayMicroseconds(on);
      digitalWrite(redPin, LOW);
      delayMicroseconds(off);
    }
  }
}


void 1to10()
{
  digitalWrite(grnPin, HIGH);
  digitalWrite(redPin, LOW);

  // fade up blue
  for(byte i=1; i<100; i++) {
    byte on  = i;
    byte off = 100-on;
    for( byte a=0; a<100; a++ ) {
      digitalWrite(bluPin, HIGH);
      delayMicroseconds(on);
      digitalWrite(bluPin, LOW);
      delayMicroseconds(off);
    }
  }
}



void 10to0()
{
  digitalWrite(bluPin, HIGH);
  digitalWrite(redPin, LOW);

  // fade down green
  for(byte i=1; i<100; i++) {
    byte on  = 100-i;
    byte off = i;
    for( byte a=0; a<100; a++ ) {
      digitalWrite(grnPin, HIGH);
      delayMicroseconds(on);
      digitalWrite(grnPin, LOW);
      delayMicroseconds(off);
    }
  }
}


void 0to02()
{
  digitalWrite(bluPin, HIGH);
  digitalWrite(grnPin, LOW);

  // fade up red
  for(byte i=1; i<100; i++) {
    byte on  = i;
    byte off = 100-on;
    for( byte a=0; a<100; a++ ) {
      digitalWrite(redPin, HIGH);
      delayMicroseconds(on);
      digitalWrite(redPin, LOW);
      delayMicroseconds(off);
    }
  }
}



void 02to2()
{
  digitalWrite(redPin, HIGH);
  digitalWrite(grnPin, LOW);

  // fade down blue
  for(byte i=1; i<100; i++) {
    byte on  = 100-i;
    byte off = i;
    for( byte a=0; a<100; a++ ) {
      digitalWrite(bluPin, HIGH);
      delayMicroseconds(on);
      digitalWrite(bluPin, LOW);
      delayMicroseconds(off);
    }
  }
}

//CODE ENDS HERE

First, start by taking two different colors of wire and cutting them into pieces (I cut them about 6 inches long). Then strip the ends off all the wires.

Solder an LED to the end of two different colors of wire (for example, I used black wire for the cathode and green wire for the anode). Then, separate the LEDs with wires attached into 3 groups.

Solder all the anodes of one group together, and all the cathodes of all the groups together, so you have 3 different groups all with a common cathode. I soldered header pins to the end of these groups so that I could easily plug it into a breadboard.

Connect the 3 anode groups of the tree to ATtiny digital pins 0, 1 and 2 (actual pins 5, 6 and 7 on the ATtiny). Connect the single common cathode to ground.

Connect ATtiny pin 4 (ground) to the negative wire of a 3 volt 2xAA battery pack, and pin 8 (Vcc) to +3 volts.

Don't use any resistors, because if you do, the ATtiny will not have enough power to light up all the LEDs. I tried with some 1/4w 220 ohm resistors and the LEDs don't light up at all.

You're done! Now go in a dark room and watch the magic!