Realistic Fire Simulation

In this page is described how to create a realistic flickering fire effect with LEDs and an Arduino board. In this case I used a Digispark due to its small size.

The intention is to give some light to a small clay decoration house, one of those prepared for lighting a small candle inside and evaporate water with essence. Instead of using a candle I put a simple battery with some LEDs inside but it looked too boring so I tried to imitate the movement of a candle inside it. Here it is described the design and process followed.

Component Schematics

The three LEDs (two reds and one yellow - I guess one red and two yellows would also look nice) are connected to the PWM ports of the arduino (Digispark, which has exactly 3 PwM pins).

The pin P1 of the Digispark board already has red LED attached to it, so there is no need to add a new one, or to remove the current one. For this reason the new schematics is:

Building

Code

For schematic 1, with all LEDs logically inverted:

int p1 = 0; // Set the 3 pins with PWM
int p2 = 1;
int p3 = 4;

void setup() {
  pinMode(p1, OUTPUT); // Set the pins as output
  pinMode(p2, OUTPUT);
  pinMode(p3, OUTPUT);
}

void loop() {
  int v1, v2, v3;

  v1 = random(155) + 100; // Calculate the new light
  v2 = random(155) + 100; // intensity values for each LED
  v3 = random(155) + 100;

  analogWrite(p1, 255 - v1); // Apply the light intensity
  analogWrite(p2, 255 - v2); // to each LED
  analogWrite(p3, 255 - v3);

  delay(20 + random(80)); // Wait some random time for next udpate
}

For schematic 2 (reusing the LED attached to Pin 1, which is not "logically inverted"):

int p1 = 0; // Set the 3 pins with PWM
int p2 = 1;
int p3 = 4;

void setup() {
  pinMode(p1, OUTPUT); // Set the pins as output
  pinMode(p2, OUTPUT);
  pinMode(p3, OUTPUT);
}

void loop() {
  int v1, v2, v3;

  v1 = random(155) + 100; // Calculate the new light
  v2 = random(155) + 100; // intensity values for each LED
  v3 = random(155) + 100;

  analogWrite(p1, 255 - v1); // Apply the light intensity to each  LED
  analogWrite(p2, v2);       // This LED is not "logically inverted"
  analogWrite(p3, 255 - v3);

  delay(20 + random(80)); // Wait some random time for next udpate
}