Wireless trail cameras automatically take videos or photos when the PIR sensor detects activity within the area it is covering.
PIR stands for “pyroelectric sensor” or “passive infrared sensor”, which generates energy when it gets exposed to heat.
When a human or animal body gets in the range of the sensor it will detect movement, because human or animal bodies emit heat energy in the form of infrared radiation.
It is called passive infrared sensor because the sensor is not using any energy for detecting purposes, but it just works by detecting the energy giving off by the other subjects.
PIR sensors only detect warm bodied targets in motion, and not stationary targets. To detect a moving living being, it must have an outer temperature that is considerably different than the surrounding ambient heat.
Even though the most common subjects of any PIR detector are warm-bodied (humans, mammals, birds), the PIR sensor will also find moving beings or objects which have an outer temperature that is significantly less than the ambient temperature.
Meanwhile the target is sufficiently big or near the sensor (even if it is small) and its own outer temperature is simply different of the ambient temp, whether it is higher or lower, if it’s in motion it can be caught by the PIR sensor.
Each manufacturer may build their surveillance devices differently, however PIR sensors should be able to be adjusted from within the settings section.
When the high setting is used, the camera will be more sensitive to heat and triggered more often by motion. When the temperature is warm it is more difficult for the sensor to detect animals, therefore the high setting is useful under this condition. High temps are usually above 80°F.
When the low setting is used it will diminish sensor´s sensitivity to heat and movement. Low settings may help in cold weather if the camera is being triggered too often by anything warmer than the surroundings. Low temps are usually below 10°F.
A normal setting can be used when the temperature is average or moderate, typically between 10°F – 80°F.
An automatic setting will have the camera choose the best option based on current ambient climate, but this works better if the temperature is expected to change dramatically while the camera is being used.
Conditions could change significantly from a moment to another. Large temperature changes can place the PIR sensor more or less sensitive. If you have a planned specific range you need to adapt the sensitivity to compensate for potential temperature changes.
If it happens that the subject and ambient temperature are equal, the PIR sensor will difficulty be able to detect it. If the subject is large such as a human, deer, beer, etc., they often have enough variation in their surface temp to permit the sensor to detect them – even when the ambient temp is equivalent to their average body’s temperature.
Depending on the brand and based on intervals you set, a wifi trail camera can take pictures or videos of an area that is outside the PIR sensor´s range without requiring a trigger from an active target. If during this time, a target gets within the range of the sensor, it can still take and send pictures based on your settings.
Wireless game cameras can fall into “false trigger”, which basically means that the sensor believes there is a motion or warmed body target when there is none. This false trigger is caused by having the device in areas where winds would have tree branches create motions and flying objects in front of the camera. Changing the camera to another spot or adjusting the sensor´s level would be required to fix this problem.
Here are additional recommendations for unavoidable false triggers issued by PIR sensors:
- Turn the sensor away from the rising or setting of the sun, that is looking toward North or South
- Keep the sensor away from an area where direct bright sun light will fall into its window
- Turn it away from tall grass or sun warmed vegetation which can trigger heat
- If camera is among a shaded area, turn the sensor away from dense bush which could hold the day’s heat. When the temperature drops at night and the warm shrub moves in the wind, it could cause a trigger
- Be sure to have your cam fastened securely. If the equipment is moved by the wind, it may be interpreted as motion by the sensor causing a false trigger