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Can Animals Trigger A Motion Sensor Light?

Most people that buy motion sensor lights do so because they want them to be triggered whenever a human approaches.

That’s because it’s nice to be welcomed home after a long day to an illuminated pathway and also because it’s a good way of deterring intruders late at night.

Although most burglars know that outdoor lights are triggered by a motion sensor, it’s not necessarily a sign that you’re awake.

They’ll still want to minimize any risk of being seen clearly on cameras or by neighbors.

But what about animals? Can motion sensor lights pick those up? And do you want them to or not?

Standard PIR sensor motion lights will detect some animals. Some allow you to adjust the sensitivity to avoid detecting pets. At the same time, there are pet-immune sensors that will ignore animals altogether.

There’s a little more to it than that, so let’s take a look at:

Can Animals Set Off Motion Sensor Lights?

brown cat in a grass

So to explain whether animals can set off a motion sensor light, we must first look at how they work.

Because most motion sensors aren’t actually sensing ‘motion.’

If they did, the tiniest movement caused by a gentle breeze could set them off, and your motion sensor lights would resemble a disco.

Most motion sensor lights work using a PIR sensor. PIR stands for passive infrared. It uses infrared detection to look for changes in the detection area.

Any time there is a change in the infrared signals, then it will activate the light.

The reason it’s called passive is that it isn’t sending out any kind of signal itself. Instead, it’s only passively monitoring an area for infrared changes.

There are active infrared sensors that instead send out infrared signals to a separate detector, but these are rare.

PIR sensors are a popular choice because they’re effective and reasonably cheap to manufacture.

But if you just buy a standard PIR sensor, it will be triggered by anything that gives off infrared radiation.

And every living thing gives off some level of infrared, so yes – animals will set off motion sensor lights.

Not always, though, as it depends on the quality of the sensor, how large the animal is, and how close it is to the sensor.

For example, a basic sensor will probably always trigger when a dog, coyote, or deer enters the field of view.

Cats, raccoons, and possums will probably set them off as well.

When it comes to smaller creatures like mice and rats, it’ll depend on how many there are in view – a lone one may be too far from the sensor to properly register.

Normally, bugs and spiders won’t cause a PIR sensor to be triggered because they’re cold blooded. So their body temperature is the same as the surrounding environment.

However in some rare cases they could trigger the sensor if they’re close enough, as their body temperature may be high enough compared to the temperature on the ground.

How To Prevent False Detections Caused By Animals?

possum climbing a wooden fence

Now some people may be happy to have their motion sensor lights triggered by animals, especially if you have a problem with deer, possums, or raccoons getting into your home.

Having a motion sensor light pointed at your trash cans is a good idea. However, this may not be 100% successful as animals will often adjust.

But plenty of people don’t want their lights to be triggered by wildlife.

So, how do you prevent false detections?

Firstly, to prevent the sensor from being set off by smaller creatures, ensure it’s mounted away from any beams or surfaces that insects or rodents may crawl on.

It should be in an open area ideally.

Beyond that, you’ll either need to buy a motion sensor light with adjustable sensitivity or a pet-friendly one (sometimes labeled as “pet immune”).

Motion sensors with adjustable sensitivity let you use a dial to determine how much of a change in infrared is needed for the sensor to trigger.

By making it less sensitive, it can ignore smaller amounts of infrared. Still, you’ll likely need to experiment with it to get the right setting.

Also, remember that the sensor will still be triggered if you’re visited by multiple animals. It’s the total change of infrared in the field of view that it’s detecting, after all.

Unfortunately, while there are other types of motion sensors beyond PIR, none of them are particularly better at avoiding false detections.

They all rely on detecting movement or by interrupting a signal between an emitting sensor and a receiver – and animals do move, and can block other types of signal too.

How Do Pet-Friendly PIR Sensors Work?

jumping dog trying to catch its shadow on a grass on a sunny day

Pet-friendly PIR sensors are a wise option to help reduce false animal detections.

They work by splitting their field of view with multiple beams.

They’ll have one that’s aimed towards the ground and one that’s at a higher angle.

These sensors will only be triggered if something enters both fields of view.

So if it’s a dog or a cat, it will only trigger the beam pointed low. Still, a human will be taller and trigger both beams, causing the sensor to activate the lights.

It’s not infallible. Pets can sometimes reach higher spaces, especially for indoor motion sensor lights where there’s furniture to climb on.

Or you could have a bird and a dog in view simultaneously.

But while not perfect, these pet immune motion sensor lights do at least cut down on those pesky false detections.

Some other pet-friendly PIR sensors will just ignore anything below a certain weight limit, only triggered when a sufficient mass enters the field of view.

These are another option too, but multiple animals at once could still trigger the sensor.

Related: Can You Use LED Bulbs For Bearded Dragons?

Final Words

Unfortunately, despite our size differences, we’re still quite similar to animals, so it’s hard to create technology that can perfectly detect the differences between humans and animals with 100% accuracy while still keeping costs down.

But buy a motion sensor that is pet immune or where you can at least adjust the sensitivity. Then, you should be able to stop most false detections.

It might happen occasionally, but for the most part, you’ll still be saving money rather than constantly switching the light.

Have you had any issues with false alarms from your motion sensors? Or any stories of when they’ve helped keep your trash (or home) safe?