when ultrasonic sensor senses something, then led1 will be on for 2 seconds then off, then turn on led2 for 400 milliseconds then off, then turn led1 again as the user is there
when ultrasonic sensor senses something, then led1 will be on for 2 seconds then off, then turn on led2 for 400 milliseconds then off, then turn led1 again as the user is there