PIR is the acronym for Passive Infra-Red. A highly effective, low-cost technology for detecting unauthorized activity by monitoring changes in infra-red heat patterns in the area you are monitoring.
When an unauthorized person (such as a burglar) enters a room the PIR sensors detect the change in temperature and trigger either an alarm or security recording. Passive infrared (PIR) detection systems contain a small memory bank that remembers the amount of infrared energy typically focused on its surface when there is no activity in the area.
PIRs are an excellent choice for hidden camera recordings because of their low power use so the run longer on a single battery charge. PIR systems are able to operate on lower power because they do not beam out their own infra red lighting which uses more power and decreases battery life. Instead passive infra red motion detection systems only sense the infrared energy coming in to their sensors from the area being monitored. The room itself generate the infra red signal!
How PIR is used in a motion detector hidden camera.
The electronics of a PIR motion detection camera sit in a passive state and are connected to the input of a burglar alarm or motion detector hidden camera. When someone enters the area, he gives off infrared energy (heat) which cannot be seen by the human eye, but can be picked up by the PIRs electronic sensors. The PIR sensor detects the radiation change emitted by the person who has entered the room. It then compares the old state of infrared energy to the new state, calculates the change and triggers the video recording camera or burglar alarm.
Placement of PIR Motion Detection Cameras & Alarms
Place your PIR motion detection hidden camera or alarm in an unobstructed position with a clear view of the entire security area you want monitored. Good choices include a ceiling or a large open wall. This is why manufacturers offer smoke detector hidden cameras or cameras built into emergency lights.
A PIR should not be placed near an HVAC vent that could blow hot or cold air onto the unit. While air does not emit much infrared energy, the air coming from a vent could change the temperature of the units plastic housing enough to confuse the electronic system and trigger false alarms.
Range of Motion Detection
Passive infrared (PIR) detection systems use a number of lenses or mirrors to give them an average motion detection range of about 25-30 feet. More expensive PIR’s feature single segment mirrors and can detect IR changes more than 100 feet. Some high end units sense up to 400 feet away.
Typically PIRs are designed for a broader angle of coverage.However, you can protect a particular area like the floor space surrounding a safe by purchasing a PIR with a very narrow coverage.
Avoiding Motion Detection False Alarms
A PIR sensor is located on a circuit board covered with a protective housing. This housing keeps out dust and insects which could obstruct the sensor. When infrared energy from a potential intruder reaches the passive infrared (PIR) detection device sensor array window, the infrared energy passes through the plastic housing covering the circuit board. The plastic housing is also useful because the infrared energy of insects could generate false alarms.
If you are using an motion detection alarm with auto dialing feature your false alarms will cost local police money and if your neighbors get used to false alarms they may begin to ignore the alarm signals and become unlikely to act in the event of a real burglary.
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