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На основе этого кода сделайте свой

/*
 * Blink_Randomly
 *
 * Modified from the basic Arduino example.  Turns an LED on for a random time,
 * then off for a (most likely) different random time.  We use pin 13 because,
 * depending on your Arduino board, it has either a built-in LED
 * or a built-in resistor so that you need only an LED.
 *
 * Original at - http://www.arduino.cc/en/Tutorial/Blink
 */

int ledPin = 13;                  // LED connected to digital pin 13
long randOn = 0;                  // Initialize a variable for the ON time
long randOff = 0;                 // Initialize a variable for the OFF time


void setup()                      // run once, when the sketch starts
{
  randomSeed (analogRead (0));    // randomize
  pinMode(ledPin, OUTPUT);        // sets the digital pin as output
}

void loop()                       // run over and over again
{
  randOn = random (100, 1200);    // generate ON time between 0.1 and 1.2 seconds
  randOff = random (200, 900);    // generate OFF time between 0.2 and 0.9 seconds
    digitalWrite(ledPin, HIGH);   // sets the LED on
    delay(randOn);                // waits for a random time while ON
    digitalWrite(ledPin, LOW);    // sets the LED off
    delay(randOff);               // waits for a random time while OFF
}