How Automatic Sensors Work
- You come near a locked door and the door automatically opens and makes way for you! You enter with your hands in pocket!
- You put your hand under the tap and the tap automatically starts!
- You have to dry your hands and you hold the same near the drier, the hot air automatically starts blowing!
Modern technology aims at doing every task in the air without need of much physical touch. Well it is interesting to hear that the technology is not that modern and it is being used for decades ... maybe a few centuries!
It all lies at the heart of the simplest semiconductor device- The DIODE. To be more specific, the PhotoDiode. Let me skip the working principle of a semiconductor diode at this point of time and focus on the working of a photodiode. You may interpret it this way that when light "of a particular wavelength" falls on the diode, the electrons getting excess energy become excited and start flowing rapidly. Thus the circuit is completed only if "that" light falls on the diode.
Now we explain the technology. If some obstacle blocks that path of light then the current flow in the circuit stops. If we make an arrangement such that at that point of time another circuit is activated, which for example starts the tap water ... then we get our desired result ... automation of devices.
Such principle is also applied in air conditioners, home lighting systems, mobile phones and most electronic gadgets.
