int ledPin = 13;
  int potPin = A0; 
  void setup() {
     pinMode(ledPin, OUTPUT); 
     } 
     void loop() {
       int potValue = analogRead(potPin);
       int blinkRate = map(potValue, 0, 1023, 100, 1000);
        digitalWrite(ledPin, HIGH); // LED on 
        delay(blinkRate); 
        digitalWrite(ledPin, LOW); // LED off 
        delay(blinkRate);
     }