int potpin = A0; 
int ledpin = 8;  
 
void setup() 
{ 
pinMode(ledpin, OUTPUT); 
} 
 
void loop() 
{ 
  int scale = (5000 - 100)/ (1023);
  int offset  = 100;
  int time = analogRead(potpin) * scale + offset;

  digitalWrite(ledpin = HIGH);
  delay(time);
  digitalWrite(ledpin = LOW);
  delay(time);
}