1. What is a PIR sensor?
  2. Range of different PIR sensors
  3. How do PIR sensors work?
  4. Application of PIR sensor in Trail Camera
  5. What are the different adjustable settings for the PIR sensor on the Trail camera?
  6. The best place to put the PIR sensor

Trail cameras are essential for wildlife enthusiasts, hunters, and outdoor enthusiasts who want to capture images of wildlife and other outdoor activities. One of the most important aspects of a trail camera is the sensor. In this guide, we'll explore the different types of sensors and their characteristics.

PIR or motion sensors are used to track cameras to detect movement in front of the camera. Each trail camera will have one or more PIR sensors. These sensors are an integral part of every trail camera design and will directly affect each camera's performance.


trail camera

 Ref: Elprocus

What is a PIR sensor?

A passive infrared sensor (PIR sensor) is an electronic sensor that measures infrared (IR) light emitted by objects within its field of view. They are most commonly used in PIR-based motion detectors. PIR sensors are often referred to simply as "PIR" and are sometimes referred to as "PID," which stands for "Passive Infrared Detector." Passive means that the PIR device does not radiate energy for detection purposes. They work entirely by detecting infrared radiation (radiant heat) emitted or reflected by objects.

How it works: All objects with a temperature above absolute zero emit heat energy through electromagnetic radiation. Usually, this radiation is invisible to the human eye because it radiates at infrared wavelengths, but it can be detected by electronics designed for this purpose. A PIR sensor can detect changes in the amount of infrared radiation impinging on it, depending on the temperature and surface properties of the object in front of the sensor. When an object, such as a person, passes in front of a background, such as a wall, the temperature within the sensor's field of view will rise from room to body temperature and then back again. The sensor converts a change in incident infrared radiation into a change in output voltage, which triggers the detection. Objects with similar temperatures but different surface features may also have different patterns of infrared emission, so moving them relative to the background may also trigger the detector.

What it does: PIR-based motion detectors are used to sense the motion of people, animals, or other objects.


trail camera

Ref: Elprocus

Range of different PIR sensors

  • Indoor Passive Infrared: The detection distance ranges from 25 cm to 20 m.
  • Indoor Curtain Type: The detection distance ranges from 25 cm to 20 m.
  • Outdoor PIR: The detection distance ranges from 10m to 150m.
  • Outdoor Passive Infrared Curtain Detector: Distance from 10m to 150m.

How do PIR sensors work?

Compared to other sensors, a PIR sensor is primary on its own, but it becomes much more complicated when a Fresnel lens is added to round out the system.

The PIR sensor has only two "pixels," and the PIR detector cannot see the image. Two "pixels" are much less than the millions in the primary image sensor. Therefore, to detect any moving people and animals in the field of view, it needs to be supplemented by other optics - Fresnel lens.

Fresnel lens array

The design of the Fresnel lens array is very subtle. Did you notice the little black curved piece of plastic on the camera? This black plastic is the Fresnel lens array for the PIR system. On the back of the curved plastic is a careful layout of Fresnel lenses. The role of the Fresnel lens is very important. First, gather light. Provides a more comprehensive range of IR for the sensor. Second, expand the detection area. Broader and more complex large rectangular regions can be seen through the small sensor window. This is performed by faceted sections of the plastic cover, engineered through precisely placed concentric rings called Fresnel lenses. Each facet works with the PIR sensor to detect a different area. The design of the Fresnel lens is essential for the camera to see the angle and location.

As mentioned earlier, the Fresnel lens design can significantly affect the detection angle, while the detection distance depends on the PIR sensor.

trail camera

Application of PIR sensor in Trail Camera

First, PIR sensor technology has been gradually improved, with small size and low-cost advantages. Secondly, the camera sensor will only activate and shoot when animals pass by in front of the camera, which is very consistent with the randomness of outdoor detection of animals. Meet the needs of long standby time and save battery power. Finally, storage space on the camera's memory card is also reserved, as the camera only takes photos and videos when there is an activity in the detection area.

What are the different adjustable settings for the PIR sensor on the Trail camera?

PIR sensor adjustable settings include primary and secondary PIR selection on or off, sensitivity selection, and trigger interval setting.

Primary and secondary PIR selection: For some trail cameras with 3 sensors, the side sensor can usually be turned on or off. Typically, the 3 sensors of the trail camera are turned on by default. But if you only want to monitor a narrower area, or because of the camera's placement, it gets a lot of false trigger recordings from the side detection area, you can turn off the side PIR sensor in the settings.

Sensitivity selection: The PIR sensitivity of general trail cameras is divided into three levels: high, medium, and low. You can tailor the camera's sensitivity to your surroundings. If it is a relatively quiet and remote deep forest, there are few animal activity tracks, and the sensitivity can be set too high to ensure that the passing of animals will not be missed. Suppose the animal activity in the area where the camera is protected is very active to save the storage space on the camera memory card. In that case, you can set the PIR sensitivity of the camera to low. This feature provides multiple applicability to detection environments and scenarios.

Trigger Interval Setting: Most trail cameras have a PIR interval between 5 seconds and 60 minutes. The PIR delay interval is the time interval the camera waits before triggering another round of photos and videos.

5-second delay: you will get many shots of the same animal.

5-minute delay: You may get a single image of each animal unless they stay longer than 5 minutes.

If you are starting with a trail camera, I suggest you can set a delay interval of 30 seconds to start. After shooting in 30-second intervals for a while, you can extend or delay the trigger interval depending on the conditions and the footage you want.

Different settings of the PIR sensor, according to the needs of your detection area, you can adjust the PIR sensor to meet your shooting needs. This function also dramatically improves the applicability and versatility of the trail camera.

trail camera

The best place to put the PIR sensor

  • Ensure that all key areas are covered, including possible entry routes, corridors, and corners
  • Avoid installing sensors near heatsinks and vents, for example, because temperature changes may affect reliability or cause false alarms
  • The ideal installation height is usually 2-3 meters above the ground
  • Avoid placing the sensor in direct sunlight

PIR sensors are an essential part of trail cameras. So if you're looking to buy a trail camera or want to get the most out of the one you have, it's essential to understand how a PIR sensor works. When shopping for a trail camera, it's important to consider the sensor's quality and any adjustable settings available to ensure you get the most out of your trail camera to capture the perfect shot. Click to learn more about trail cameras with high-quality sensors.

Read More