_3_speed_blinking

long previousMillis = 0; // store last time LED was updated
long interval = 100; // blink interval (milliseconds)

void setup() {
  
  pinMode(2, INPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  
  digitalWrite(4, HIGH); // start with one LED on

}

void loop() {
  
 if (digitalRead(2) == HIGH) {

   if (interval == 100) {
       interval = 250;
   }
   else if (interval == 250) {
      interval = 500; 
   }
   else if (interval == 500) {
     interval = 100;
   }
   
   delay(500);
   
 }

 unsigned long currentMillis = millis();
 
  if(currentMillis - previousMillis > interval) {
    // store the last time LEDs blinked 
    previousMillis = currentMillis;

    // alternate the LEDs
    if (digitalRead(3) == HIGH) {
      digitalWrite(3, LOW);
    }
    else {
      digitalWrite(3, HIGH);
    }
    
    if (digitalRead(4) == HIGH) {
      digitalWrite(4, LOW);
    }
    else {
      digitalWrite(4, HIGH);
    }
    
  }
 
}