Most people do not wash their hands properly. Many sources say that you should scrub your hands for at least 15-20 seconds. A good way to keep track is to sing a song like Twinkle, Twinkle, Little Star.
Here is a Lysol LYSOL® Healthy Touch® No-Touch Hand Soap System that has been modified using Arduino to show a countdown and play Twinkle, Twinkle, Little Star..
If you want to make your own, follow the instructions on the next page. Go to Step 1