PIR Sensor Alarm – the Technology Behind it

A PIR sensor can pick up infrared radiation from surrounding objects. Once temperatures change due to a moving intruder, the alarm connected to such a sensor can go off.

Safety is a big issue nowadays, whether you are talking about home or business. One way to ensure this is to install alarms, and one kind of alarm is the PIR Sensor Alarm, which is based on the technology of the Passive InfraRed sensor. The infrared sensor is an electronic gadget that measures the degree of infrared light radiated by objects that pass through or that are picked up by the sensor. Such sensors are used to build motion detectors, which are attached to alarms.

A PIR sensor can sense movement through changes in temperature. For instance, if a human passes in front of a source of infrared radiation that is of a different temperature, say a wall, safe, or display case then the sensor will detect the change in temperature and set off an alarm. This is because all objects emit black body radiation; IR radiation may be invisible to human eyes, but electronic devices such as the PIR sensor can spotthis radiation. While some infrared sensors will emit infrared light beams, a passive infrared sensor will simply accept and detect incoming radiation.

You can think of the PIR sensor as an infrared camera that remembers how much infrared energy is on its surface. When power is applied to the sensor, the electronics will control a set of circuits that are connected to and can activate the control panel of a security alarm. When a person enters the PIR sensor’s monitored area, the sensor picks up the infrared energy that the person’s body emits. This infrared energy is then focused by a segment of mirror or a Fresnel lens. This detected energy overlaps a certain part of the sensor chip that was measuring a cooler part of an area that the PIR is protecting. As the person moves, the hot spot on the sensor chip also moves, which can activate the alarm through input that is interpreted as detection.

In other words, differences in temperature can call the alarm up. The PIR sensor can be overrun with an intruder holding a thermal shield that would make him or her have the same radiation and temperature as the surrounding area. This is very difficult to achieve, however, so a PIR sensor can be useful in protecting houses, businesses, and other establishments that need security from intruders. For more information on the best PIR sensor for your home or business, talk to your local security retailer.