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Twinkle/Sparkle Effects

cookbook/recipes/twinkle.md

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Twinkle/Sparkle Effects

Difficulty Level: ⭐⭐ Intermediate Time to Complete: 25-35 minutes Prerequisites:

You'll Learn:

  • How to create probability-based animations using random8() threshold checks
  • Selecting random LED positions safely with random16(NUM_LEDS)
  • Tuning fade rates and probability thresholds to control twinkle density and persistence
  • Creating variations (starfield, party lights, fireflies) by adjusting parameters
  • Using brightness variation and timing to add depth and dimension to sparkle effects

Random twinkling stars and sparkle effects.

Simple Twinkle

Basic twinkling effect with random colors:

cpp
void twinkle() {
    // Fade all LEDs slightly
    fadeToBlackBy(leds, NUM_LEDS, 32);

    // Add new twinkles
    if (random8() < 50) {  // 50/255 chance per frame
        int pos = random16(NUM_LEDS);
        leds[pos] = CHSV(random8(), 200, 255);  // Random color
    }
}

Colored Twinkle

Twinkle effect with a specific color:

cpp
void coloredTwinkle(CRGB color) {
    fadeToBlackBy(leds, NUM_LEDS, 20);

    // Add multiple twinkles per frame
    for (int i = 0; i < 3; i++) {
        if (random8() < 100) {
            int pos = random16(NUM_LEDS);
            leds[pos] = color;
            leds[pos].fadeToBlackBy(random8(50, 150));  // Vary brightness
        }
    }
}

Sparkle (Instant Flash)

Quick flashing sparkles on a dark background:

cpp
void sparkle(CRGB color, int count, int delayMs) {
    // Turn off all LEDs
    FastLED.clear();

    // Flash random LEDs
    for (int i = 0; i < count; i++) {
        int pos = random16(NUM_LEDS);
        leds[pos] = color;
    }

    FastLED.show();
    delay(delayMs);
}

White Twinkle (Christmas Lights)

Warm white background with bright white twinkles:

cpp
void whiteTwinkle() {
    // Background: warm white
    for (int i = 0; i < NUM_LEDS; i++) {
        leds[i] = CRGB(255, 147, 41);
        leds[i].fadeToBlackBy(200);  // Dim background
    }

    // Random bright twinkles
    for (int i = 0; i < 5; i++) {
        if (random8() < 80) {
            int pos = random16(NUM_LEDS);
            leds[pos] = CRGB::White;
        }
    }

    FastLED.show();
    delay(100);
}

How It Works

The twinkle effect creates a starry night appearance by:

  1. Fading: Gradually dimming all LEDs to create trails
  2. Random selection: Choosing random LEDs to light up
  3. Brightness variation: Using different brightness levels for depth
  4. Color variation: Optional random or specific colors

Parameters Explained

  • Fade rate (in fadeToBlackBy): How quickly LEDs dim

    • Lower values (10-20) = long, smooth trails
    • Higher values (50+) = quick, snappy twinkles

  • Probability (in random8() check): How often new twinkles appear

    • Lower values (20-50) = sparse, occasional twinkles
    • Higher values (100-200) = frequent, dense twinkles

  • Count: Number of simultaneous sparkles

    • 1-3 for subtle effect
    • 5-10 for busy starfield

Usage Tips

For a starfield effect:

cpp
void loop() {
    fadeToBlackBy(leds, NUM_LEDS, 32);
    if (random8() < 30) {
        leds[random16(NUM_LEDS)] = CRGB::White;
    }
    FastLED.show();
    delay(20);
}

For party lights:

cpp
void loop() {
    fadeToBlackBy(leds, NUM_LEDS, 50);
    for (int i = 0; i < 5; i++) {
        if (random8() < 100) {
            leds[random16(NUM_LEDS)] = CHSV(random8(), 255, 255);
        }
    }
    FastLED.show();
    delay(50);
}

For fireflies:

cpp
void loop() {
    fadeToBlackBy(leds, NUM_LEDS, 10);  // Very slow fade
    if (random8() < 20) {
        leds[random16(NUM_LEDS)] = CRGB(255, 255, 100);  // Yellowish
    }
    FastLED.show();
    delay(30);
}

Variations

Palette-Based Twinkle:

cpp
void paletteTwinkle(CRGBPalette16 palette) {
    fadeToBlackBy(leds, NUM_LEDS, 40);
    if (random8() < 60) {
        int pos = random16(NUM_LEDS);
        leds[pos] = ColorFromPalette(palette, random8(), 255, LINEARBLEND);
    }
}

Twinkling Rainbow:

cpp
void rainbowTwinkle() {
    fadeToBlackBy(leds, NUM_LEDS, 30);
    if (random8() < 80) {
        int pos = random16(NUM_LEDS);
        leds[pos] = CHSV(random8(), 255, 255);
    }
}