How automatic tap works

Well in modern days it very necessary to preserve  every drop of water, because in most of the places of the earth, ground level water is fast depleting, causing a acute shortage of drinking water. Automatic tap is  one of the best  choices, to regulate usage of water .

Do you ever wonder how does automatic tap works. Here is how-

Though the animation above, illustrates the whole mechanism clearly. Then also, I am describing the important parts.

1.  Object, Obviously  in our case its hand.
2.   A sensor emitting infrared signal, it is the same signal, as in our T.V remote.
3.  The connection between sensor and solenoid valve is important, it sends signal to solenoid valve to open up, without it valve will not open at any condition.
4.  Solenoid Valve, this is kind of valve that opens up whenever it gets an electrical signal. Thus creating a passage for water to pass. 
5. other important parts are indicated directly

To understand the working of solenoid valve this video is the best.