12 V RGB strip color fade on an Arduino Uno

// A 12 V RGB strip through three MOSFETs, faded around the color wheel.
//
//   strip +12V -> the 12 V supply
//   strip R, G, B -> the drains of three IRLZ44Ns; their sources to GND
//   the gates -> pins 9 (red), 10 (green) and 11 (blue)
//
// The strip is common anode: a color lights while its MOSFET pulls that pad
// to ground, and PWM on the gate sets how much of the time it does.

const uint8_t RED = 9, GREEN = 10, BLUE = 11;

void color(int r, int g, int b) {
  analogWrite(RED, r);
  analogWrite(GREEN, g);
  analogWrite(BLUE, b);
}

void setup() {
  pinMode(RED, OUTPUT);
  pinMode(GREEN, OUTPUT);
  pinMode(BLUE, OUTPUT);
}

void loop() {
  // Red to green, green to blue, blue to red: one color fades in as the last fades out.
  for (int i = 0; i <= 255; i += 5) { color(255 - i, i, 0); delay(15); }
  for (int i = 0; i <= 255; i += 5) { color(0, 255 - i, i); delay(15); }
  for (int i = 0; i <= 255; i += 5) { color(i, 0, 255 - i); delay(15); }
}