Understanding motion

By now you must have figured that the PIR sensor is not the most idealistic sensor for us to switch the lights on or off. Mostly because, although the motion is one of the best indicators of presence, there can be times when you might not move at all, for example, while resting, reading a book, watching a movie, and so on.

What do we do now? Well, we can do a little trick. Remember in the last chapter we used our proximity sensor to sense whether a person has crossed a specific area or not? We will implant a similar logic here; but rather than just copy pasting the code, we will improve it and make it even better.

So rather than using one single IR proximity sensor, we will be using two of these things. The mounting will be as shown in the following diagram:

Now it is very evident that whenever a person walks in from the door side to the room side the Sensor 1 will show a lower reading when detecting a body. Then, while he is walking towards the room side, Sensor 2 will...