Article 10

Touch-Activated Lighting

Control WS2812B NeoPixel LEDs from the Touch Board — colour changes, animations, and combined audio-visual responses.

⏱ 20 min read NeoPixel WS2812B LEDs lighting Adafruit visual feedback

Adding visual feedback

The Touch Board’s built-in LED (D13) is barely visible and not usable for art. WS2812B NeoPixels (sold as Adafruit NeoPixels or similar) are addressable RGB LEDs you can control with a single data wire from the Touch Board — change any LED to any colour from code.

What you need

Touch Board
WS2812B LED strip or individual pixels (Adafruit NeoPixel, ALITOVE, etc.)
5V power supply (or USB for small LED counts)
300–500Ω resistor (on the data line)
Optional: 1000 μF capacitor across the power rail

Wiring

Touch Board 5V  ─────────────────── LED Strip 5V
Touch Board GND ─────────────────── LED Strip GND
Touch Board D6  ──── 470Ω ─────── LED Strip Data

Power warning: Each WS2812B LED draws up to 60mA at full white. 12 LEDs at full brightness = 720mA — more than USB can safely supply. For more than ~8 LEDs, use a separate 5V power supply rated at 1A+ and share the ground with the Touch Board.

Install the Adafruit NeoPixel library

Library Manager → search “Adafruit NeoPixel” → Install

Basic sketch: touch electrode → colour

#include <MPR121.h>
#include <Wire.h>
#include <Adafruit_NeoPixel.h>

#define LED_PIN    6
#define LED_COUNT  12

Adafruit_NeoPixel strip(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800);

// Assign a colour to each electrode
uint32_t COLOURS[12] = {
  strip.Color(255,   0,   0),  // E0  red
  strip.Color(255, 127,   0),  // E1  orange
  strip.Color(255, 255,   0),  // E2  yellow
  strip.Color(  0, 255,   0),  // E3  green
  strip.Color(  0,   0, 255),  // E4  blue
  strip.Color(148,   0, 211),  // E5  violet
  strip.Color(255,  20, 147),  // E6  pink
  strip.Color(  0, 255, 255),  // E7  cyan
  strip.Color(255, 165,   0),  // E8  amber
  strip.Color(127, 255,   0),  // E9  lime
  strip.Color(138,  43, 226),  // E10 purple
  strip.Color(255, 255, 255),  // E11 white
};

void setup() {
  strip.begin();
  strip.setBrightness(80);  // 0–255
  strip.show();

  if (!MPR121.begin(0x5C)) { while(1); }
  MPR121.setInterruptPin(4);
}

void loop() {
  if (MPR121.touchStatusChanged()) {
    MPR121.updateTouchData();
    for (int i = 0; i < 12; i++) {
      if (MPR121.isNewTouch(i)) {
        strip.setPixelColor(i, COLOURS[i]);
        strip.show();
      }
      if (MPR121.isNewRelease(i)) {
        strip.setPixelColor(i, 0);  // off
        strip.show();
      }
    }
  }
}

Combined audio + lighting

Add the MP3 player alongside the NeoPixels:

#include <MPR121.h>
#include <Wire.h>
#include <SPI.h>
#include <SdFat.h>
#include <FreeStack.h>
#include <SFEMP3Shield.h>
#include <Adafruit_NeoPixel.h>

SFEMP3Shield MP3player;
Adafruit_NeoPixel strip(12, 6, NEO_GRB + NEO_KHZ800);

void setup() {
  Serial.begin(57600);

  strip.begin();
  strip.setBrightness(60);
  strip.clear();
  strip.show();

  // MPR121 init
  if (!MPR121.begin(0x5C)) { Serial.println("MPR121 error"); while(1); }
  MPR121.setInterruptPin(4);

  // MP3 init
  SdFat sd;
  if (!sd.begin(SD_SEL, SPI_HALF_SPEED)) { Serial.println("SD error"); while(1); }
  if (!MP3player.begin()) { Serial.println("MP3 error"); }
  MP3player.setVolume(10, 10);  // lower = louder on VS1053
}

void loop() {
  if (MPR121.touchStatusChanged()) {
    MPR121.updateTouchData();
    for (int i = 0; i < 12; i++) {
      if (MPR121.isNewTouch(i)) {
        // Play sound
        char filename[12];
        sprintf(filename, "TRACK%03d.mp3", i);
        if (MP3player.isPlaying()) MP3player.stopTrack();
        MP3player.playMP3(filename);

        // Light the LED
        strip.setPixelColor(i, COLOURS[i]);
        strip.show();
      }
      if (MPR121.isNewRelease(i)) {
        strip.setPixelColor(i, 0);
        strip.show();
      }
    }
  }
}

Animations on touch

More expressive than on/off: fade in on touch, fade out on release:

uint8_t brightness[12] = {0};
bool touching[12]      = {false};

void loop() {
  // Update touch state
  if (MPR121.touchStatusChanged()) {
    MPR121.updateTouchData();
    for (int i = 0; i < 12; i++) {
      if (MPR121.isNewTouch(i))   touching[i] = true;
      if (MPR121.isNewRelease(i)) touching[i] = false;
    }
  }

  // Animate brightness
  for (int i = 0; i < 12; i++) {
    if (touching[i]) {
      brightness[i] = min(255, brightness[i] + 15);  // fade in
    } else {
      brightness[i] = max(0,   brightness[i] - 5);   // fade out (slower)
    }
    // Scale the LED colour by brightness
    uint8_t r = (red(COLOURS[i])   * brightness[i]) / 255;
    uint8_t g = (green(COLOURS[i]) * brightness[i]) / 255;
    uint8_t b = (blue(COLOURS[i])  * brightness[i]) / 255;
    strip.setPixelColor(i, r, g, b);
  }

  strip.show();
  delay(16);  // ~60fps update
}

Key takeaways

WS2812B NeoPixels connect via a single data pin (D6) with a 470Ω series resistor
Each LED draws up to 60mA at full brightness — use a separate power supply for more than 8 LEDs
strip.setPixelColor(i, colour) followed by strip.show() updates the display
One NeoPixel per electrode creates immediate visual feedback for each touch
Fade animations (update brightness each frame) are far more expressive than on/off
The NeoPixel data pin (D6) is fully compatible with the Touch Board alongside MPR121 and MP3 player