/*
   Written by R. Jordan Kreindler, 12/2017

   Digital pin 3 goes to 3K resistor than to base
      of TIP120

   LED in series with 220 ohm resistor,
      Both go between TIP120 collector & 5VDC
*/

int i;

// PMW pin 3
#define BASE 3
int delay1 = 1500;

void setup()
{
  // Set pin for output to control Base pin
  pinMode(BASE, OUTPUT); 
}

void loop()
{
  // By changing values for i you can change 
  //   the brightness of the LED
  for (i = 0; i <= 255; i = i + 40) {
    analogWrite(BASE, i);
    delay(delay1);
  } // End for
} // End loop