Infrared Motion Detectors – How do they work?

We need to understand the ways in which Motion Detectors function, and we can delve into some technical information as well, preferably for increasing our awareness of these products as a consumer and as well as to hone a little bit of our general knowledge.

Those who have studied electronics and sciences may be more than aware of the ways in which an infrared motion detector works. But laymen do not always possess such knowledge. That is where this awareness will help us at least choose the right products in the market. Even a salesman may start to look startled or puzzled, the moment you throw a technically specific question at him.

Almost all the objects emit infrared rays – mostly objects that heat up to certain extents, objects that generate heat of longer wavelengths than normal lights. Human beings emit stronger infrared rays that are as strong as 9.4um. Animals can generate such amount of infrared lights as well. These lights cannot pass through translucence – a translucent window, just like sun light can pass through it. Hence, the infrared waves emitted by human beings are not visible to the naked eye.

Motion detectors can pick up such amount of heat through their sensors, and these same sensors remain idle at extensive heat or apparent light which could be seen by naked eyes. Motion detectors can detect light emitted by human beings which is not much apparent and visible to the human eyes.

The sensors are made of silicon or crystallized materials which pick up heat from humans, namely, the infrared radiation. Special filters ensure that they respond only to a certain wavelength possibly emitted by human beings, and avoid exposure to other wavelengths of heat.

Some more special features in motion detectors, like two different sensing materials in one motion detector can ignore varying temperatures and heat caused by sunlight and other blazing sources. However, even if a few of the sensors pick up the radiation from other wavelengths of infrared rays, the second sensing material can cut off the alarm or lights from going off.

Detection in almost all the motion detectors is limited to 8 to 14um which is transmitted by humans and other non-glowing objects. This gives the sensors a high sensitivity to the human body. Active Motion Detectors also transmit infrared radiation around a wavelength of 8 to 14um. Lenses like the Fresnel Lens, which have a focal length of 0.65 inches – from the Fresnel Lenses to the sensing materials, are made of materials that transmit Infrared radiations.

These are some of the technically specific ways that a Motion Detector functions. Although, we laymen do not understand the technical nuances, we shall merely hope that the above information are written in a decodable manner to the laymen. We may better understand these technical nuances to improve an awareness related to consumerism. This knowledge will equip customers with the confidence of possessing an ability to buy the best of technologically superior products. Updating ourselves with technical knowledge is a must in the satiable urge to be fully benefited of our purchases!