Saturday, December 17, 2011

LED Candle Light Flicker with Arduino

I've build a simple candle light with an LED which is powered by an arduino. I have one of these cheap candle lights, but they aren't very smooth and they don't look like a flame, so build one myself.

What you will need:

Wire the led and the resistor up like in this schematic:
LED Flicker Setup

Now upload the following code to the arduino:
#define FLICKER_LED_PIN 10

// the start of the flicker (low)
static int flicker_low_min = 200;
static int flicker_low_max = 240;

// the end value of the flicker (high)
static int flicker_high_min = 230;
static int flicker_high_max = 256;

// delay between each low-high-low cycle
// low->high |flicker_hold| high->low
static int flicker_hold_min = 40; // milliseconds
static int flicker_hold_max = 80; // milliseconds

// delay after each low-high-low cycle
// low->high->low |flicker_pause| low->high...
static int flicker_pause_min = 100; // milliseconds
static int flicker_pause_max = 200;  // milliseconds

// delay low to high and high to low cycle
static int flicker_speed_min = 900; // microseconds
static int flicker_speed_max = 1000; // microseconds

void setup() {

int flicker_random_low_start = 0;
int flicker_random_low_end = 0;
int flicker_random_high = 0;
int flicker_random_speed_start = 0;
int flicker_random_speed_end = 0;

void loop() {
  // random time for low
  flicker_random_low_start = random(flicker_low_min, flicker_low_max);
  flicker_random_low_end = random(flicker_low_min, flicker_low_max);
  // random time for high
  flicker_random_high = random(flicker_high_min, flicker_high_max);
  // random time for speed
  flicker_random_speed_start = random(flicker_speed_min, flicker_speed_max);
  flicker_random_speed_end = random(flicker_speed_min, flicker_speed_max);
  // low -> high
  for (int i = flicker_random_low_start; i<flicker_random_high; i++) {
    analogWrite(FLICKER_LED_PIN, i);
  // hold
  delay(random(flicker_hold_min, flicker_hold_max));
  // high -> low
  for (int i = flicker_random_high; i>=flicker_random_low_end; i--) {
    analogWrite(FLICKER_LED_PIN, i);
  // pause
  delay(random(flicker_pause_min, flicker_pause_max));

Everything in the flicker is randomized. You can change each parameter, the get the flicker faster or much slower, glowing like.

The candle light is mostly done. Now cut a 2-3 cm piece of the hot glue stick and drill a 5mm hole in it (diameter of the led). Stick the led in it, and the light is nicely diffused. The get the best result, place a piece of paper around it like in the photo above.

Hope you like it!


  1. Replies
    1. Just simple Board with USB connector running with ur PC (PC - Privet Computer -> Any Computer -> Windows or Apple. A lot ppl dont understand what PC is. Everyone think it is only Windows. That what Apple use to sell Laptops, 2x more MONEY.) There is all kinds of Arduino Boards. On that Board is Microchip that U program it with code above. The open-source Arduino environment makes it easy to write code and upload it to the i/o board. It runs on Windows, Mac OS X, and Linux. The environment is written in Java and based on Processing, avr-gcc, and other open source software. We all share codes and getting help from ppl around the world if we need help. One think a lot of ppl dont explain is, U pull out programed Microchip and use on the Board for project, saving $45-$25 for new Arduino. Microchip is about $7, so put back on ur Board and program it again. Link to Arduino:

  2. This looks awesome. Could anyone tell me what it would take to run several of these? Could they be run off a single Arduino (with different PWM ports and separate code for each)? I'm new to this, but this project is just the sort of thing I'm looking for. Any help would be appreciated- thanks!

    1. Yes, you would just define another PWM pin...

      #define FLICKER_LED_PIN1 3

      Set it up for OUTPUT in setup and then just add code to the loop in both of the analogWrite sections

      analogWrite(FLICKER_LED_PIN, i);
      analogWrite(FLICKER_LED_PIN1, i);

    2. There is all kinds of chips U can use: ATmega328
      Arduino and ATtiny45 / ATtiny85:
      Last Link is to Instructables. They will help with any, any project U like to make, even Robot, or Remote controlled Cars and Helicopters. I hope this will help.

  3. Hi! How many mcd's does the led you used have?

    Nice idea, i'll try to replicate it.


  4. Shouldn't one use pink noise rather than white noise to approximate the flicker spectrum of a candle?

  5. I don't know! How to apply pink noise? I can test it, if i know how to generate pink noise. Btw: Brownian noise is pretty relaxing:

  6. Thank you for the nice laid out example. I used your code and adapted it for the Microchip PIC 12f683 here:

    Please let me know if that is not ok with you.

  7. Thank U. That is nice one. More simple and so easy, that I have seen before

  8. thank you for the idea, but is there a code for the attiny45 ? the cost are lower

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