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Can A Laser Pointer Set Off A Motion Detector?

It can be frustrating if your home’s motion sensors are falsely triggered, especially if you have them connected to your security system and they set off an alarm.

The whole point of a motion sensor system is to trip only when there’s actual motion in your home – you don’t want to have to reset an alarm to find out there was nobody there.

Well, maybe that’s better than finding an intruder, but you understand what I mean.

There are a few potential causes of false alarms – but are laser pointers one of them?

Should you be concerned about kids playing with laser pointers near your home?

Laser pointers emit infrared energy, and the more powerful ones could trigger a PIR motion sensor. Even low-powered ones could set off a sensor due to the rapidly changing light and heat.

In order to answer this fully though, we need to look at:

  • The different types of motion sensor
  • Which type is activated by a laser pointer, and why
  • Other potential causes of false alarms

Different Types of Motion Detectors: Active vs. Passive

Modern motion sensor in action indoors

The first thing to address when answering whether laser pointers trigger motion sensors is that there isn’t just one type of motion sensor.

In fact, there are quite a few different types.

Broadly, you can split them into passive and active groups.

Passive sensors don’t emit any kind of signal.

As the name suggests, they’re completely passive – they’re monitoring the area and will react to a change in the area they can see.

The most common of these is the Passive Infrared (PIR) sensor which makes up the majority of motion detectors used for outdoor lighting and indoor home security systems.

Active sensors emit a signal, which either rebounds off moving objects to a receiver built into the sensor, or they have a separate sensor with a constant signal.

Microwave sensors are active sensors that emit microwaves around a room and react with microseconds if the rebounded microwaves act differently because they’ve hit a moving surface.

The other common type is ultrasound, which uses a separate receiver and a constant ultrasound signal.

Once that signal is blocked by an object, the sensor is triggered.

What Type Of Sensor Can Be Activated By A Laser Pointer?

A low angle shot of a motion sensor lamp

So, now that we’re clear on the main types of motion sensors – which of these can be activated by a laser pointer?

Well, a laser pointer emits low-level infrared energy, depending on the color of the laser beam.

Green laser pointers, in particular, emit a higher amount of infrared energy, especially those that have been manufactured cheaply or in an unregulated country.

Based on that, it’s pretty easy to determine that a laser pointer could trigger a PIR sensor.

It’s not going to interfere with a microwave sensor, and the frequency of a laser isn’t going to interrupt an ultrasonic wavelength for an ultrasound motion sensor.

Whether a laser pointer triggers a motion sensor depends on the beam’s intensity and how accurately it is shone onto the sensor.

You’d likely need to point the laser directly at the motion sensor, and simple red pointers may not emit enough infrared energy.

However, some PIR sensors can be triggered just by the rapid change of light in the field of view, particularly those also manufactured to a lower standard.

So, in theory, any laser pointer could set off a motion sensor if it shone directly at it.

While this is annoying, since many people like to play pranks with laser pointers, they’d have to be pretty accurate to hit a motion sensor on your home to trigger it.

Unless you have some pretty dedicated people who want to annoy you and know where your motion sensors are, you shouldn’t have to worry.

Other Causes of Motion Detector False Alarms

collage of animals - a cat indoors laying on the radiator, raccoon being fed from a human hand, running dog, a ginger cat outdoors

So, what else could trigger a false alarm with your motion sensor?

Firstly it depends on what you categorize as a false alarm.

If you only want your sensor to be triggered because of human movement, then there are times when animals could trigger it.

Pet-friendly motion sensors usually have two receivers pointing in different fields of view – one higher than the other.

The sensor only triggers when change is detected in both fields – so animals low to the ground won’t trigger it.

But if you have an animal that likes to climb on the furniture, or your outdoor sensor sees different animals simultaneously, it could be triggered.

Otherwise, the main false trigger is a change of heat.

If something causes the temperature in a room to change, such as a radiator suddenly switching on, then it might trigger the sensor if it’s detecting infrared signals.

Radiators do emit tiny amounts of infrared, though not by design.

A faulty sensor is the other likely cause of a motion detector false alarm. However, sometimes they can be damaged and misbehave when that happens.

It’s normally something that happens to outdoor sensors more than indoor ones – where wind can blow debris against the sensor, or the elements can cause damage even to waterproof ones.

But once a motion sensor develops a crack, the actual sensor chip inside will start to react even when there isn’t an actual signal to trigger it.

Final Words

It’s easy to buy cheap laser pointers online and often from locations where their manufacture isn’t regulated.

So owning a laser pointer that emits enough infrared to set off a motion sensor isn’t completely out of the question.

However, it’s unlikely that someone can terrorize you with a pointer and constantly set your lighting or home security system off.

Unless it’s a particularly prank-loving member of your family.

Youths looking to cause trouble could trigger outdoor motion sensors. Still, you’d likely only have those connected to your outdoor lights.

It’s a little frustrating, but hardly the end of the world and not exactly a thrill for the prankster either.

Have you had any issues with false alarms on your motion sensor security system? Or problems with laser pointers?