Editor & Article Writer for Outdoor Wilds
How Do Trail Cameras Work?
Today we sometimes take it for granted that our “little plastic box of tricks” we use to record wildlife and game pictures, will happily snap away all it detects without much thought into the technology behind it. Let’s take a look at how do trail cameras work?
Better known as a trail camera, game camera or camera trap. These clever little devices have rapidly grown with technological advancement in the last 20 years. But how do trail cameras work to achieve the results we enjoy so much?
Understanding the basic technology how a modern trail camera work, helps you have a better idea as where to place the camera for best results and also in making a more informed choice on which trail cam is best suited to your goals.
The first people to record and monitor deer activity were management and wildlife biologists. Over 30 years ago this involved placing a piece of string across a trail, triggering a clock when tripped. Later 35mm cameras were incorporated.
If your interested in the history of trail cameras and how they evolved from this basic triggered method, take a read of my post about the history of trail cameras.
How Does Infrared Work?
During the technological advancement over the last 20 years or so, 2 types of infrared triggered game cameras emerged. Active infrared and passive infrared or PIR as it’s known.
For the most part we use PIR trail cams and I will focus on the technology behind how a PIR sensor works.
Active Infrared Trail Cameras
Active infrared cameras are much less common. They have their place in recording data but are more specialist and used mainly by scientists.
They work by simply emitting an infrared beam which is received by a separate unit. When the beam of energy is broken it acts as a trigger. This has an advantage in extreme hot or cold climates as it’s less susceptible to “miss triggers”, when an animal is a similar temperature to the ambient air temperature.
Companies such as TrailMaster have been one of the leading manufacturers in active trail monitoring systems for many years.
Passive Infrared Trail Cameras
As with most advances in technology, size and weight is often reduced. Trail cameras are no different and PIR sensor technology has been a key part of seeing our trail cameras become smaller. You only have to look at trail cameras like the Browning Strike Force HD Pro to see where trail camera manufacturers are heading.
Some people mistake PIR sensors to emit infrared. They only receive information of the environment within their detection zone. They do not emit an infrared beam like the active infrared systems mentioned earlier.
The PIR sensor is aware that something is in front of them by changes in temperature and motion and the temperature difference between the moving object and the background environment.
To understand exactly how a PIR sensor works, first of all it’s important to understand the very basics of infrared energy.
It’s hard to believe, but everything on the planet gives off energy, even an ice cube. To understand this science, the electromagnetic spectrum provides a scale of energy emitted by objects.
Infrared energy or radiation is invisible to the human eye, but we can feel it. A fire emits infrared radiation and we in turn notice it as heat. All objects that are not at absolute zero in temperature -459 degrees fahrenheit emit some amount of infrared however small. As of course so do all warm blooded animals.
It’s this infrared energy emitted by a deer or any other warm blooded animal that the PIR sensor picks up.
What Does PIR Mean?
The PIR sensor sits on the trail cameras printed circuit board (PCB) and the sensor itself is housed inside a sealed metal case. A window at the top of the sensor covered in silicon exposes 2 squares or slots to infrared radiation.
When a heat source hits 1 of the sensors slots or squares it creates a positive differential change in temperature. As the heat source moves (heat in motion) from one half of the sensor to the other half it creates a negative differential change.
It’s these changes in energy pulse that send an electronic signal to the camera’s image sensor and a trigger is made.
Extreme ambient temperatures can affect the PIRs ability to detect these subtle changes in temperate. That’s why it’s always best to point a trail camera north as sun rays falling on the PIR may cause it to “false trigger”.
This basic understanding of how a PIR works inside a trail camera will hopefully allow you to make better choices in the area to setup the camera and to avoid too many “false triggers”.
What Makes A Good Trail Camera?
There are 3 main factors that determine whether your trail camera will perform well.
- Trigger speed
- Size of detection zone
- Recovery rate
What is trigger speed?
Todays manufacturers like to use trigger speed as marketing tool. You’ll see trigger speed advertised before anything else when it comes to trail cameras.
Trigger speed is the time it takes for the PIR sensor to detect “heat in motion” across the sensor, sending an electronic pulse to the camera image sensor for it to open and close the camera shutter, thus recording an image to the SD card.
Most trail cameras these days will have a trigger speed of less than one second. If your covering a trail head then your going to need a trail cam with as fast a trigger speed as possible.
This is less critical if your setup at the edge of a field where deer are more likely to be grazing on food plots.
The Importance of Detection Zone
It’s great to have a trigger speed that is sub 1 second, but if the detection zone is too narrow it won’t trigger the camera to record a picture.
The detection zone is essentially a cone shaped zone in front of the camera that the PIR sensor picks up “heat in motion”. Some detection cones are long and narrow, others are wide and short. Again it depends on what area your trying to cover that you choose the right trail cam for the job.
What is shot lag?
The time it takes for the camera to be ready to take another picture after it recorded the previous image is the recovery time or as some people call it, “shot lag”. Video mode on modern trail cameras don’t require a fast recovery time as you can set the video length and interval manually on most trail cameras today.
Many trail cameras also have a burst mode for still pictures, where the camera will take 6 – 8 images in rapid succession once triggered. It is however a factor to consider when looking to choose a trail camera.
Type of Batteries
Low battery power does reduce the effectiveness of the PIR sensor. This will mean reduced detection range and more “false triggers”. Extreme cold can also reduce the battery life of a camera.
Always check with the manufacturer to see what temperature ranges they specify that are optimal. I have written a post with further information about trail camera battery choice here.
Conclusion
Hopefully you now have a better understanding of how trail cameras operate. This should help you decide on suitable monitoring locations that will record more pictures with less empty frames.
It’s worth noting that as a trail camera ages, the PIR sensor becomes more “noisy” meaning it will become less accurate to the “heat in motion” detection that records a picture. You get what you pay for in trail cameras in many cases.
Cheaper trail cams will have lower quality PIR sensors and tend to wear out quicker, so that is something to consider when purchasing a trail camera.
The best way to get to know your trail camera is spending time with it in different setups. The knowledge you gain from this experience will be invaluable for scouting wildlife for many years.
I hope you have found this post useful. Good luck out there and happy hunting!
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