39. Addressable RGB LEDs: NeoPixel / WS2812 Strips

Project: Shelf mood strip

Build a short accent strip for a shelf or bench edge: calm blue, work amber, or alert red. Power and show() habits matter more than fancy animations on day one.

Sketch 1 discovers fill, chase and show(). Sketch 2 is the useful mood strip - type C/W/A in Serial (hands-on bridge to the lesson 40 status tile).

One data wire, many LEDs

WS2812 / NeoPixel LEDs keep their own colour and forward the stream. Change a RAM buffer, then call show() - without show(), nothing updates.

Power first: 5 V, GND and current

Do not power an 8-LED strip from ESP32 3V3. Use external 5 V and common GND. Budget ~60 mA per LED at full white. Keep Colour values modest (about 80) in class.

Data resistor, direction and colour order

Follow the strip arrow DIN -> DOUT. Wrong colours often mean NEO_GRB vs NEO_RGB. Weak supply causes resets on bright white.

Library choice

Adafruit NeoPixel only for this lesson. FastLED can wait.

Wiring and safe build sequence

1. Power off before connecting the strip
2. External 5 V+ -> strip 5 V; GND common with ESP32
3. ESP32 GPIO 5 -> 330-470 ohm -> strip DIN
4. USB powers ESP32 only

What this sketch is for: Discovery: solid dim red, then a green chase proves power, DIN direction and show(). Match the breadboard layout below before upload (short 8-LED stick only).

#include <Adafruit_NeoPixel.h>

const int pin = 5;
const int n = 8;
Adafruit_NeoPixel strip(n, pin, NEO_GRB + NEO_KHZ800);

void setup() {
  strip.begin();
  strip.clear();
  strip.show();
}

void loop() {
  strip.fill(strip.Color(80, 0, 0));
  strip.show();
  delay(500);

  strip.clear();
  strip.show();
  for (int i = 0; i < n; i++) {
    strip.setPixelColor(i, strip.Color(0, 80, 0));
    strip.show();
    delay(80);
    strip.setPixelColor(i, 0);
  }
}

What this sketch is for: Useful accent light: type C (calm), W (work) or A (alert) in Serial to fill the strip. Same three moods return as a matrix status tile in lesson 40. Match the dedicated 5 V breadboard below before upload.

#include <Adafruit_NeoPixel.h>

const int pin = 5;
const int n = 8;
Adafruit_NeoPixel strip(n, pin, NEO_GRB + NEO_KHZ800);

void fillMood(uint8_t r, uint8_t g, uint8_t b, const char* name) {
  strip.fill(strip.Color(r, g, b));
  strip.show();
  Serial.print("Mood: ");
  Serial.println(name);
}

void setup() {
  Serial.begin(115200);
  strip.begin();
  strip.clear();
  strip.show();
  fillMood(0, 0, 60, "CALM");
  Serial.println("Shelf mood strip - type C, W or A");
}

void loop() {
  if (!Serial.available()) return;
  char c = Serial.read();
  if (c == 'C' || c == 'c') fillMood(0, 0, 60, "CALM");
  if (c == 'W' || c == 'w') fillMood(50, 30, 0, "WORK");
  if (c == 'A' || c == 'a') fillMood(60, 0, 0, "ALERT");
}