To Do

  1. Change the pattern of HIGH/LOW signals to the solenoid, so that instead of being
    on (HIGH) for 1.5s, and off (LOW) for 4s, it is on and then off in some other sequence,
    e.g.: 3 short on/off-cycles, followed by a long delay, followed by 1 long on/off cycle.

Be sure to use a for loop to keep your code simple.