#include <TimerOne.h>

  int ledPin1 = 10;
  int ledPin2 = 11;
  int ledPin3 = 12;
  int ledPin4 = 13;
  int x = 1;

  int buttonState = 0;
//  long previousMillis = 0;
//  long currentMillis = millis();
volatile byte stateOne = HIGH;
volatile byte stateTwo = HIGH;
volatile byte stateThree = HIGH;
volatile byte stateFour = HIGH;

  
void setup() {

   pinMode(ledPin1, OUTPUT);
   pinMode(ledPin2, OUTPUT);
   pinMode(ledPin3, OUTPUT);
   pinMode(ledPin4, OUTPUT);

   Timer1.initialize(150000);
   Timer1.attachInterrupt(change);
   Serial.begin(9600);
   }

void loop() {

  switch (x) {
    case 1:  digitalWrite(ledPin1, stateOne);
      x++;
      break;
    case 2:  digitalWrite(ledPin2, stateTwo);
      x++;
      break;
    case 3:  digitalWrite(ledPin3, stateThree);
      x++;
      break;
    case 4: digitalWrite(ledPin4, stateFour);
      x = 1;
      break;
  }
}

void change()
{
  stateOne = !stateOne;
  stateTwo = !stateTwo;
  stateThree = !stateThree;
  stateFour = !stateFour;
}