Motion sensors are often used in indoor spaces to
control electric lighting [11]. A motion detector i.e. Passive
Infrared sensor (PIR sensor) is an electronic device that is
being used to measure the infrared (IR) light radiating from
objects in its field of view. PIR sensors are often used in the
construction of PIR-based motion detectors. Apparent
motion is detected when an infrared source with one
temperature, such as a wall. All objects above absolute zero
emit energy in the form of radiation [10]. Usually infrared
radiation is invisible to the Human eye but can be detected
by electronic gadgets designed for such a purpose [11]. The
term passive in this instance means that the PIR device does
not emit an infrared beam but merely passively accepts
incoming infrared radiation. “Infra” means below our ability
to detect it visually and “Red” is because of its Color
representation which shows the lowest energy level of the
color RED and applies to many sources of invisible energy.
Thus, a simple equation can be used to model the sensor
output S (x,ϕ ) as a function of the distance x and the angle
of incidence ϕ with the target surface: