What is IR sensor ?
As we all know that light have different color . Generally light have 7 colors in its visible spectrum . Infra-Red is another types of color of light but unfortunately we cannot see this color . This is beyond our eye can detect it .Infrared (IR) falls in the range of the (EM) spectrum between microwaves and visible light. It has frequencies from about 3 GHz up to about 400 THz and wavelengths of about 30 cm to 740 nm . Hence IR sensor is a electronics component that detect Infrared color emitted from different object .These sensor are useful in many application . For example night vision ,Detecting stars,mass,astroid from galexy ,in smart phones to off display while calling , in line following robots etc . And we can also make it to detect object from certain distance .
How does IR sensor works to measure distance ?
IR sensor have two led one generate IR radiation and another measure reflection of IR radiation .We have taught in high school that black color is perfect absorber of light while white color reflects all and the color between white and black somehow reflect ray and some absorbs .So Basically IR sensor sense how much amount of color is reflected .Some sensor gives digital value and some need to convert into digital using suitable ADC .So the time between transmitted and received signal is used to detect the distance where the object is located .
You will find application of IR sensor in AVR section to measure speed of object in tachometer using AVR section .