// These variables store the flash pattern

// and the current state of the LED

// 1000ms=1s

// 16.6ms= 1/60th of 1 second, or one 60hz cycle.

// 8.3ms is half of on 60hz cycle

// so 8.3ms OnTime and 8.3ms OffTime adds up to a

// full cycle square wave at %50 duty

// As long as your on and off both add up to your

// desired frequency you should be good.

int ledPin = 10; // the number of the LED pin

int ledState = LOW;// ledState used to set the LED

long Freq = 16.6;

unsigned long previousMillis = 0; // will store last time LED was updated

long OnTime = 8.3; // milliseconds of on-time

long OffTime = Freq - OnTime; // milliseconds of off-time

void setup()

{

 // set the digital pin as output:

 pinMode(ledPin, OUTPUT);

}

void loop()

{

 // check to see if it's time to change the state of the LED
 unsigned long currentMillis = millis();

 if((ledState == HIGH) && (currentMillis - previousMillis >= OnTime))
 {
   ledState = LOW;  // Turn it off
   previousMillis = currentMillis;  // Remember the time
   digitalWrite(ledPin, ledState);  // Update the actual LED
 }
 else if ((ledState == LOW) && (currentMillis - previousMillis >= OffTime))
 {
   ledState = HIGH;  // turn it on
   previousMillis = currentMillis;   // Remember the time
   digitalWrite(ledPin, ledState);	  // Update the actual LED
 }

}

 if((ledState == HIGH) && (currentMillis - previousMillis >= OnTime))
 {
   ledState = LOW;  // Turn it off
   previousMillis = currentMillis;  // Remember the time
   digitalWrite(ledPin, ledState);  // Update the actual LED
 }
 else if ((ledState == LOW) && (currentMillis - previousMillis >= OffTime))
 {
   ledState = HIGH;  // turn it on
   previousMillis = currentMillis;   // Remember the time
   digitalWrite(ledPin, ledState);	  // Update the actual LED
 }

}