What is a PIR Sensor

The term PIR is often seen in lighting and on lighting products and is associated with turning lights on and off automatically when someone walks near one. We explore what PIR means, how it works, how to choose it and when you should use it within your lighting choices. Here’s what you need to know.

Ceiling PIR Sensor

What is a PIR?

A PIR is a passive infrared sensor used to detect motion, so a PIR is a passive motion detector that waits for infrared temperature from body heat to trigger an activity. In other words, it can sense motion through changes in temperature.

So when a person walks into the detection area of a passive sensor, it detects heat emitted from that person and triggers an alarm or turns on the light. However, these sensors wouldn’t be practical if they could be activated by small animals or insects so most passive sensors can be adjusted to pick up motion of humans with certain levels of emitted heat rather than anything and everything that moves.

Motion Detector Lighting

Motion sensing lights have been around since the 1960s when they were first invented by General Electric Company (GEC). They’re best suited for areas where there is a lot of activity such as parking lots or warehouses because they detect movement automatically and turn on instantly when something passes under them without any need for wires or cords to be connected between fixtures and switches.

PIR’s have been included in lighting as a way to reduce energy usage and increase safety. Now LED is the primary source of illumination that is instantly on, PIR presence detection has become a very effective way to turn lighting off and immediately on according to movement or dim it down to a lower output when there is no occupation.

PIR as an Energy Saver

So how do motion sensing lights help with energy saving? The answer is simple. Motion sensor lights are an excellent way to bring down the wattage or lumens needed for a given space by lighting only what you need when it’s being occupied and allowing for much less wasted light during hours of vacancy. It has been estimated that up to 50% of all outdoor lighting can be turned off due to non-occupancy so using PIRs in your exterior spaces will have a huge impact on decreasing electricity costs over time.

PIR for Health and Safety

When movement can be detected without needing to turn on lighting, the environment changes and occupants feel safer. This is especially beneficial in places like stairwells, elevators or hallways where lighting can be kept on with the use of motion sensors so that they will only turn off when no one’s present.

PIR for Security Lighting

The other, less tangible benefit related to using PIRs as part of outdoor ambient lighting is safety which comes from making sure there are no dark areas where intruders could hide once the sun goes down outside. This contributes to creating a safe environment which can be both comforting and aesthetically pleasing.

PIR detectors are used for all sorts of purposes from vehicle security to detecting intruders through windows at night time to allow you visibility without having lights visible from outside your home. One final benefit to using PIR technology is its ability to not only sense occupancy but also give feedback about what activities are being done by people based upon their heat signatures which makes it a great way for homes with elderly living there alone keep track of them during certain times while allowing others entry after hours if needed. All in all, PIR sensors are a smart, efficient and cost effective way to use lighting.

How Does a PIR Motion Detector Work?

A Passive Infrared (PIR) sensor detects changes in infrared (heat) radiation. The PIR works by accumulating thermal energy from the surrounding area, which is then processed to produce an output signal proportional to the rate of thermal energy being received at its sensing face. This type of motion detector may be thought of as a heat-seeking device; it will detect any moving object that has a significantly higher temperature than its surroundings or background ‘noise’. In this way, even relatively cool objects can activate the detector if they are moving quickly enough and their emitted heat signature is high enough compared with ambient levels. Some passive infrared sensors have built-in lenses so they only respond to specific beams within their field of view – e.g., an alarm zone in front of a doorway.

PIR sensors are passive devices, detecting changes in infrared radiation without generating or radiating any power themselves. This makes them able to operate reliably with very low power consumption over long periods of time (up to 20 years). They require only a small heat input from an external heat source such as the sun, humans, electrical appliances etc., for operation. They have no moving parts and typically last 100K hours or more depending on model type and quality.

PIR Detector Components

A PIR detector also consists of three main components:

PIR Sensor

The PIR sensor detects infrared light. It is protected from outside factors like humidity by a metal casing. On top of the casing, there is a small surface with infrared-transmitting material under it. The pyroelectric elements within the housing contain electrodes made up of lead zirconium titanate ceramic materials that are capable taking temperature measurements by changing their electric charge. The sensor generates electricity from the infrared radiation or heat.


The lens is what can be seen from the outside of the detector. It’s main roles are to focus light on the infrared sensor so it can cover a larger area, filter light to capture specific wavelength, and protect the sensor from outside impacts and dirt.

Printed Circuit Board

A printed circuit board (PCB) processes the triggered activity from the sensor. It regulates how sensitive the sensor can be, tells how long it takes for the light to turn on after motion has been detected and how long it takes for the light to turn off after no motion has been detected.

A detector circuit which contains an amplifier that amplifies & outputs the signal created by changes in temperature level within its detection zone or field of view. It then sends this information on to transmitter circuits where it becomes processed into various control signals such as “line voltage”, control relays etc., before being passed on via wires back to lighting load centers, photocells, timers and other electrical equipment like motors (elevators).

Types of PIR in Lighting

In most lighting applications, there are three different types of PIR detectors: narrow beams for long-range detection and wide angle beams which detect motion from the side as well as in front of them. Finally, there is a standard beam which has 180 degree range to detect motion in front of it.

When to Use a Narrow Beam PIR

Narrow beam PIR are best for lighting applications where you need to cover a long distance, so garages or warehouses are the perfect fit. These types of beams have low sensitivity levels which makes them less likely to detect unnecessary things like rain coming through an open window or someone pushing on the door when they shouldn’t be in that area at all.

When using narrow beams it is important not to place objects close by because this will trigger false alarms and can cause problems with your security system if there is no one around causing any movement at all. This type of detector is often used outdoors since they offer great range capabilities even under bad weather conditions such as snow storms, fog etc.

When to Use a Wide Beam PIR

Wide beam PIR are best for lighting applications where you need to cover a large area. This makes them perfect for corridors, entrances and exits of buildings or warehouses which have lots of traffic in the early morning hours when people are arriving to work.

Unlike narrow beams, wide beams detect what is happening on either side as well as what’s going on directly in front of it making these detectors ideal if there are multiple entry points into an area that needs coverage. They also don’t create false alarms like narrow-beam detectors do with objects close by because they sense things from different angles so empty spaces won’t trigger any activity at all.

When to Use a Standard Beam PIR

Standard beam PIR are ideal for outdoor lighting since they have a wide range of 180 degrees and can detect motion from any direction. This makes them the most common type used when creating security systems because you will be able to cover all possible entrances into an area with just one detector by placing it in the center making sure that there is no blind spot anywhere.

One disadvantage of using standard beams is that sometimes, depending on where you place your detectors, people walking past may trigger false alarms but this isn’t too big of a problem if these lights are only meant to serve as part of a security system which also includes other types like sound sensors or combination units which include both light & sound detection capabilities together.

Advantages to PIR Sensor Lighting

PIR sensors are advantageous as they don’t require any external connections like power cables to function, and thus can be easily moved around or re-located if required. For example: If you need a sensor on the outside of your home which is not near an electrical outlet for it to be connected with wiring back into your home (for appliances), then this would make for a good choice since no wiring is needed at all.

Secondly, because PIR sensors work by detecting infrared radiation from heat sources such as people moving around within their detection zone or field of view; this means that even though there may be things such as curtains etc., in front of windows where people may try hiding behind – these won’t really affect its functionality since they’re not emitting heat like people are.

PIR sensors can also be used for applications such as animal/pest control, to monitor the movement of pets at home or in kennels; they can also help prevent unwanted entry into buildings (e.g., by shoplifters), detect intruders who may have entered via an open door etc.; PIRs are also widely used for security purposes both outdoors and indoors – e.g., controlling lights on roads so that there is no glare from them which drivers could experience while driving their cars at nighttime etc.. Lastly, one advantage with using a PIR sensor is that you won’t need to use bright lighting within dark areas where it’s being since its natural infrared radiation will be enough to provide lighting for you.

PIR Outdoor Lighting

Why PIRs are so great in outdoor lighting is that they’re very quick to detect changes in temperature up to 30-feet away, have no issues with interference from light sources or sun exposure, don’t get fooled by stationary objects like trees swaying in the wind, aren’t affected by rain or snow because they simply sense heat rather than rely on reflected light back into space even though most of these sensors are encased inside weatherproof housings – it’s worth noting that some models may not hold up well under water conditions where immersion beyond an hour could damage them. Some people put motion sensing lights around their homes for security purposes which are perfect to be used in dark areas where there is no power.

Why Solar Lighting Benefits from PIR

PIR is a great choice for solar lighting because it’s the best way to save on your energy bill by not having to use electricity all of the time. With PIR, the solar lighting is only on for as long as you set once motion is detected so the longevity of the precious resource of sunlight charged battery power is extended by avoiding wastage.

Solar lighting with PIR sensors are also great for outside use because they can be set to turn on within certain time intervals that you specify, which is useful if there might be animals or pets around your home since it’ll still keep them from getting too close.

PIRs work well even in the dark and their detection capabilities won’t get affected by other light sources such as street lamps etc. One thing worth noting about these lights though is that when they do detect movement from people walking past then consider the beam width most suitable to avoid unwanted passing traffic.

If you’re planning to have one of these installed outdoors either sunlight or at night-time then make sure to buy a model which is weatherproof if you want your light to last for years without any issues.

Andrew Orange , the owner of Orange Lighting qualified and worked as an interior designer in 1993 before specialising in lighting working on high profile projects based in London. Since starting Orange Lighting Ltd in 2003 he has been sharing his knowledge and unique teaching style mostly to his designer clients, offering practical real life advice born from running a busy consultancy and lighting supply business. Launching in 2020, his blog has evolved into Quick & Easy Lighting, curating some 25 years design experience into making the lighting choice and design process achievable and easy to understand for all.