Your home needs to be protected from many things- the weather, unexpected accidents, but most importantly, it needs to be protected from other people who may wish you or your family harm. One way you can do this is with a 
motion detector.
The great thing about motion detectors is that they don’t just cover a specific area, they cover a range. Actions can be unpredictable, so it is good to have options covered if you’re concerned about someone breaking into your home.
How does the motion detector work?
There are two main components to motion detectors. There are sources of focused light (oftentimes a laser beam) and a light sensor. With the type of detector that you would see in someone’s home, it would be set up so that the light sensor would be receiving the light that is being projected out. When someone walks in-between the two, the light signal is interrupted and the light sensor sends a signal to the control box.
There is a more advanced motion detector, which is a passive infrared motion detector. These can detect the heat emitted from the intruder’s body. The sensor in these would be designed to detect sharp increases in the infrared energy. Because of the levels inevitably change subtly from time to time; they are programmed to react with only rapid changes in the infrared level.
With both of these, the alarms are not set off immediately, in order to give the homeowner the chance to enter a code and disable the system. But if they do not get to it in time, or someone else is trying to enter your home and do not enter the code, various alarms will go off.
A motion detector would be a great addition to your home security and can give you extra peace of mind.