Wednesday, November 3, 2010

Arduino Day 3: Psychedelic Fun With a Tri-Color LED

Tip! This post is part of a series on my adventures with Arduino

I picked up a tri-color RGB super-bright LED yesterday and had some fun playing around with it. The first thing I did was scour the Internet to figure out how to wire this thing up. It was surprisingly difficult to find a decent pin out and wiring guide.

What threw me was that the LED doesn’t exactly get wired to ground. Instead, you wire the long pin to +5v and the short pins to digital outputs. Weird. I would guess it has something to do with a potential difference between the digital output [+0v,+5v] and the +5v supply. That is, pushing 100% on the digital output would cause a difference of 0v, and no light.

If it wasn’t so late I’d go test this theory. Maybe tomorrow. If anyone can help me understand this, please do!

Anyway, it works:


Today’s build was super easy once I wrapped my head around how this thing’s wired. The DIP switch isn’t needed—I was just playing around with one color at a time before I made the video.

Speaking of super easy, has anyone played this game “Candyland”? It’s a bunch of crap. That game is like sooooo easy. It has one problem, though: you have to play it with three year olds who cheat. Oh, and it’s so boring. To pass the time, I try to imagine what it would be like to navigate that crazy candy world in real life. As I stack the deck with doubles, I picture Bruce Willis or pre-crazy Tom Cruise climbing up the side of a giant sugar crystal volcano or something. With some luck, Thing 1 “accidentally” lands on that go-to-the-end square and the torment is over.

On a brighter note, Thing 1 has almost grasped Go Fish, which is pretty magical to see unfold. For now. In a couple weeks…I don't know. It’s become clear to me why we were moved onto playing more sophisticated games as early as possible.

Oh yeah, the build:



day three - bb


Day 3 - schematic


Today’s code is very straight forward. It basically just increases the intensity of each color a random amount (0-5 of 255) every 25ms. Once the color exceeds 255, I flip it to –255 so it can start counting to zero. I only write the absolute value to the pin so the effect is an intensity value that ramps up and down.

I was real nice this time and included comments, even though I usually hate comments (duplication at best, lies at worst).

int RPin = 9;
int BPin = 10;
int GPin = 11;

int Pins[] = { RPin, BPin, GPin };
int Vals[3];

#define PinsCount (sizeof(Pins) / sizeof(int))

void setup() {
  // put your setup code here, to run once:
  for(int i = 0; i < PinsCount; i++){
    // initialize output to random intensity
    pinMode(Pins[i], OUTPUT); 
    Vals[i] = 0;

void loop() {
  // put your main code here, to run repeatedly: 
  for(int i = 0; i < PinsCount; i++){
    // add/subtract a random amount of intensity, wrapping around if necessary
    Vals[i] = (Vals[i] + random(6));
    // start counting toward zero, because the above item always adds
    if(Vals[i] > 255){ Vals[i] = -255; }
    // send the abs value since it could be [-255,255]
    analogWrite(Pins[i], abs(Vals[i]));

Next Steps

This could turn into a neat toy if I just wire the LED to three potentiometers. Then kids could mix colors themselves. Hmmm…

I’ll put that on hold, though as I think I’ll be moving on to a new component. Maybe a buzzer?