You know, I always found automatic doors, escalators, and elevators very magical. Every time I would go close to a door and see it open on its own, I would always walk a little away from the door, to the left or to the right, to check at what point I will be close enough for the door to open. It has always been fun.

We interact and use multiple sensors on a daily basis even without knowing their presence. They are present everywhere! Don't you think they make our life simpler?

One very important thing that all of us should remember is that all the sensors work on the basic laws of physics. They use physical conditions such as light, temperature, pressure, humidity, and so on, using circuitry within them and converting them into electrical signals.

So, the insides of a sensor will look something like this:

Keep this block diagram in mind; we are going to use this to channel our thoughts when we build our own sensor. Remember the three parts of any sensor: a part that senses physical conditions, a second part that converts that to electrical signals (voltage, in most cases), and a third part that gives the resulting signals to a microcontroller.