Exterior Lighting

How Do Motion Sensors Work? 

Motion Sensors At Home

Although you may think that all motion sensors function in basically the same way, there are various kinds of motion sensors that actually slightly differ from one another, and there are various benefits and drawbacks of each type.

If you’re looking to reduce your energy bills without changing your lighting system completely, using motion sensors will help ensure that lighting is only switched on when necessary.

Motion sensor lights are perfect for those rooms where you typically leave the lights on accidentally, like offices, but are also great for rooms that you normally enter carrying stuff in and don’t have a free hand to operate switches, like supply closets and laundry rooms.  

But how do motion sensors work exactly? Read on to find out more about these kinds of sensors and how motion sensors work.

Motion Sensors At Night

Although the principle is essentially the same, not all motion sensors are made the same. Therefore, if you are planning on investing in motion sensors for your workplace or home or anywhere else, you need to have a better understanding of how the different types of technology involved work.

In the following post, we go into details so you can learn exactly how do motion sensor lights work – which will help you to make better buying decisions.  

So What Are The Different Types of Motion Sensors?

By looking at the wide array of different types of motion sensors available and the technologies used by them, to help you choose between them, based on where and in what way you want to use them.

When it comes to outdoor lighting, motion sensors are often combined with solar panels, reducing the installation time and your electricity bills (wondering how do solar panels work?).

Active Sensors 

Active sensors are motion sensors that utilize radar waves, infrared energy or similar methods to identify changes in rooms whey are located and monitoring. There are three active sensors that are used the most: 

  • Tomographic 
  • Ultrasonic 
  • Microwave 

motion sensors indoor

Tomographic sensors generate radio waves and are normally used commercially where a higher level of security is required to provide coverage for a larger area, such as for solar powered flood lights. Ultrasonic sensors are the kind most often used in lighting and generate sound waves that are at a higher level than human ears can hear, although cats, dogs and on rare occasions, fish can hear.

Microwave sensors, as the name suggests, generate microwave pulses. The problem is that as they are often able to see right through walls and other non-metallic objects, if they are not calibrated properly, they can set off false alarms.  

When active sensors are installed, they basically send our pulses of energy, the type depends on the kind of active sensor they are, and they measure the amount of time the pulses of energy take to bounce back after hitting objects in a room they are installed.

This is very similar to how a bat uses echolocation to see well in the dark. It’s worth noting that they are not limited to just line of sight and are able to identify even minor movements and changes.

It’s also worth keeping in mind that these particular sensors are prone to raising false alarms and as they work constantly, they consume a great amount of power than passive models. 

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PIR or Passive Infrared Sensors 

Speaking of passive models, there’s actually only one type of passive sensor – PIR or passive infrared sensor. This form of motion detector does its job by measuring increases and decreases in infrared radiation, or heat as it’s better known. The heat generated by all and any warm-blooded animals, humans and the sun. Within PIR sensors there are two slots and a thin piece of pyroelectric material.

This is what reacts with the IR radiation. When both slots are detecting the same heat levels, the sensor stays idle. That’s known as the calibrated ambient heat level of the room.  

However, when a large animal or human being enters into the covered area, this creates what is known as a positive differential charge between those two slots. This charge is what triggers the PIR sensor.

They can be calibrated to react to specific heat level changes, which means you don’t have to worry about small, insignificant fluctuations turning the lights on, which means it would trigger just because it’s sunrise and the room gets warmed a little or because a small animal like a cat or dog enters the room.

Unfortunately, as PIR sensors have a line of sight and directional coverage, you need to be careful that there’s no shelves or partitions blocking the space you are wanting detected. 


Dual Tech Motion Sensors – Dual Technology Sensors 

With dual technology sensors or dual tech motion sensors you get the benefits of a PIR sensor and ultrasonic sensor in one effective and efficient device. False alarms are less likely and these sensors are used where you can’t just use a single type of sensor, like classrooms, offices and rooms that have tall furniture or high ceilings. Lights only switch on when both the PIR and ultrasonic sensors both detect occupancy, when you have dual tech sensors in place.  

And have the added bonus of only requiring that one sensing tech is active to keep the lights on if the room is actually occupied. Meaning that smaller movements such as someone writing or typing is detected by the ultrasonic sensor, but a person walking down the hallway and past the door to that room is not detected. 

Vacancy Vs Occupancy 

There are two types of lighting motion sensors – vacancy and occupancy varieties. Vacancy sensors switch the lighting off in a room if it does not detect motion and the room is empty, but you need to switch on the lights manually whenever you enter the room.

Because of that, rooms with large windows and conference rooms that have a lot of natural daylight entering them through the day are the rooms that benefit most from this kind of lighting motion sensor.  

Whereas occupancy sensors switch the lights on automatically when it is tripped and then switch off again after a pre-determined period of time without any movement. As such, this kind of sensor works best in rooms that are high-traffic areas like restaurant pantries and bathrooms. 

So, now you have a better understanding on how these great pieces of technology work, you can make much smarter decisions about the type of outdoor motion sensor lights you need in your property, whether it is in your office or at home.  

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