What Are PIR Triggers and How Do They Work? A Complete Guide

Do you want to know what are Pir triggers and how do they work? Yes, As a homeowner’s PIR is an electronic sensor that measures infrared light radiating from objects in its field of view and they are often used to automatically activate or trigger other devices and systems. 

I first learned about PIR triggers when installing a security system in my home. The alarm company technician showed me how the small PIR motion detectors worked with the control panel to sense intruders. 

I was fascinated by how this simple passive infrared technology could detect movement and provide perimeter protection around my property.

In this blog post, I will explain in depth how basic PIR sensors work as triggers. You’ll learn about the pyroelectric sensor, Fresnel lens, and circuit inside these compact motion detectors. 

I’ll also cover how to use PIR triggers for applications like home automation, animatronics, and even Arduino projects.

Let’s dive in!

What Are PIR Triggers and How Do They Work?

Passive infrared (PIR) sensors detect motion and are often used to automatically activate or trigger other devices and systems. I first learned about PIR triggers when installing a security system in my home.

The alarm company technician showed me how the small PIR motion detectors worked with the control panel to sense intruders. I was fascinated by how this simple passive infrared technology could detect movement and provide perimeter protection around my property.

In this in-depth blog post, I will cover everything you need to know about PIR sensors and how they function as triggers. We’ll start by examining how basic PIR motion detectors operate using passive infrared detection and pyroelectric sensors. I’ll explain PIR trigger features like detection range, field of view, and sensitivity adjustments.

Later, we’ll explore the many applications for PIR triggers in motion-activated systems like home security alarms, lighting control, animatronics, and more.

I’ll also provide tips for hacking and modifying PIR sensors using Arduino and Raspberry Pi. And if you’re looking to buy PIR motion detectors, I’ve included a buyer’s guide covering key specifications, recommended models, and price comparisons.

By the end of this guide, you’ll understand exactly how PIR passive infrared motion sensors work as versatile triggers for DIY and commercial projects. So let’s get started!

How PIR Motion Sensors Work

Passive infrared (PIR) sensors are electronic devices that detect infrared radiation emitted from objects within their field of view. They are called “passive” because they do not emit any energy for detection purposes, unlike active sensors like radar. The term PIR stands for “pyroelectric infrared”.

PIR motion sensors contain a pyroelectric sensor, which can detect levels of infrared radiation. Everything emits some low level radiation, and the hotter something is, the more radiation is emitted. The human body emits infrared radiation that is detectable by PIR sensors.

When a person moves within the detection zone, the sensor picks up the changes in infrared radiation levels, which triggers the output.

The pyroelectric sensor is sensitive to levels of infrared radiation but cannot differentiate between sources on its own. It needs help to focus only on a restricted area for monitoring motion.

This is why PIR sensors also contain a plastic Fresnel lens that focuses infrared radiation onto the pyroelectric sensor in a specific detection pattern.

Together, the pyroelectric sensor and Fresnel lens allow a PIR motion detector to monitor a defined area for changes in infrared radiation levels.

When an intruder passes through the field of view, their body heat triggers the sensor to activate its output to indicate motion detection.

Inside the PIR motion sensor is a circuit board consisting of the following stages:

• Pyroelectric sensor – Detects levels of infrared radiation
• Fresnel lens – Focuses infrared from detection field of view
• Amplifier – Boosts the sensor signals
• Threshold comparator – Compares signals to defined trigger level
• Output circuit – Provides switch or analog output signal
• Timing and sensitivity controls – Sets detection parameters

When motion is detected by the sensor, it sends a amplified signal to the comparator. If the signal crosses the defined threshold, it activates the output circuit which then switches the output pin or provides a variable analog voltage depending on the sensor model.

The sensitivity and timing controls allow adjusting the trigger threshold and duration of the output.

Now that you understand the internal workings of basic PIR motion sensors, let’s look at some key features and specifications you’ll see for these passive infrared detectors.

PIR Sensor Features

PIR motion sensors designed for trigger applications have a variety of features and settings to consider:

Detection Range – The maximum distance at which the sensor can reliably detect movement. Long range models can detect up to 30 feet.

Field of View – The focused area that the PIR can monitor, usually expressed as an angle (e.g. 120° field of view). Sensors with wider fields of view cover larger areas.

Sensitivity – Adjusts the trigger threshold level to filter noise or activate only on significant infrared changes. Higher sensitivity settings make the PIR sensor more easily triggered.

Time Delay – Specifies how long the output remains active after detecting motion. Configurable delay from 5 seconds to several minutes.

Weatherproof – PIR sensors rated for outdoor use with waterproof, dust-proof casings and sealed electronics.

Voltage – Typically low voltage sensors powered by 5-24V DC voltage, with capability up to mains AC voltage levels.

Output Interface – Simple digital (switching) output, or analog voltage proportional to detected motion level.

Mounting – Integrated swivel/tilt mount and wiring terminals or external housing.

PIR sensor specifications will also indicate parameters like power consumption, operating temperature range, surge protection rating, and conformal coatings for reliability.

We’ll cover how to interpret these specs when buying PIR motion detectors later in this guide.

Now that you have a solid understanding of how passive infrared PIR motion sensors work, let’s explore some real-world applications for using them as versatile triggers.

Using PIR Triggers for Motion Activated Systems

PIR motion sensors are commonly used as triggers in automated systems that need to activate based on movement and occupancy. Their ability to reliably detect infrared radiation changes makes them ideal for security systems, lighting control, special effects, and more.

Some of the most popular applications for PIR sensor triggers include:

Security and Intrusion Alarms

Passive infrared sensors are a key component of many home and business security systems used for intruder detection. Their capability to monitor human motion both indoors and outdoors makes them ideal for:

• Perimeter protection – PIRs mounted on walls or fence lines detect intruders entering the property. Long range models provide expanded coverage.
• Room motion monitoring – Detectors placed in key interior areas to sense intruders moving through the premises. Pet immune PIRs ignore small animals.
• Connecting to alarm panels – Sensor digital outputs easily interface to control panel zones. Central monitoring of multiple PIRs throughout a building.
• Active arming – PIRs placed at entrances ensure alarm activation only after area is vacated and secured. Reduces false alarms.
• Closet/cabinet alarms – Mini PIR sensors used to detect cabinet doors or drawers being opened.

With fast response times and adjustable sensitivity, PIR motion detectors are standard components in many DIY and commercial security installations. Their versatility supports comprehensive protection against unauthorized entry.

Automated Lighting Control

PIR occupancy sensors help automate lighting systems in homes and businesses for convenience and energy savings. Typical applications include:

• Motion activated interior lighting – Lights turn on when room is occupied and off after a delay when vacant. Saves electricity.
• Exterior spotlights – PIR sensor switches on exterior lighting when motion is detected around entrance or patio. Adds safety and security.
• Stairwell lighting – Sensors mounted on landings control lighting for stairs. Only illuminates when used.
• Parking areas – Single PIR can control multiple lights covering garage, carport or driveway.
• Integration with smart lights – Connect motion sensors to smart bulbs and lighting controllers using IFTTT rules or direct integration.

Automating lighting with PIR sensors provides hands-free control for interior and exterior areas. It eliminates wasted energy from lights left on in unoccupied spaces for convenience. PIRs deliver effective occupancy-based lighting automation.

Prop Controllers and Animatronics

The haunt and theme park industries rely heavily on PIR motion sensors to trigger animated props, displays, and scare effects:

• Actor triggers – Sensors cue animatronic character motions based on guests approaching. Creates interactive scenes.
• Scare triggers – Activate pneumatic props, lights, or sounds when people walk through a haunted house room. Adds dynamic effects.
• Display triggers – Motion near an exhibit or diorama starts animation sequences using servos, motors or controllers. Automatically draws attention.
• Weatherproof PIRs – Ruggedized sensors specially designed to trigger outdoor props and effects in any weather.

With adjustable fields of view, PIRs only activate props and effects when people are present in a specific zone. This helps startle guests or draw them into an experience at the right moments for maximum impact. Rugged outdoor units ensure reliable performance even in rain, dust, or fog.

PIR motion sensors are a versatile way to integrate automated triggering effects into any haunt attraction or themed environment. Their infrared detection capabilities bring spaces to life when activated.

Hacking and Modifying PIR Sensors

The simple digital or analog interfaces on basic PIR motion detectors make them easy to integrate into electronics projects using platforms like Arduino and Raspberry Pi. With just a bit of hacking, you can modify sensor behavior and response.

Some common ways to hack PIR sensors include:

• Using longer jumper wires to separate/relocate the PIR module from the development board for more flexible mounting in your project enclosure.
• Triggering a buzzer, LEDs, or camera when motion is detected. Visual or audible alerts.
• Interfacing multiple PIRs to independently monitor zones and track direction of movement.
• Cascading PIR outputs so motion from one sensor triggers the next in sequence like dominos.
• Extending detection range by adding multiple Fresnel lens inserts in 3D printed enclosures. Focusing infrared across longer distances.
• Increasing sensitivity by amplifying the PIR module output voltage before feeding it to the microcontroller. More easily triggered.
• Using variable analog output to determine level of motion and trigger different responses proportional to activity.
• Troubleshooting false triggers by adjusting PIR module sensitivity trimpot, repositioning lens inserts, or filtering power.

With inexpensive commercial modules available, PIR sensors are easy to integrate into custom electronics and programming experiments. The ability to modify their performance opens up even more possibilities for interactive projects!

Buying Guide for PIR Motion Sensors

When purchasing PIR motion detectors for your application, there are a few key specifications and features to consider:

Detection Range – Match the sensing distance to the size of the area you need to monitor. Long 50+ foot ranges suit outdoor areas. Short 10-15 feet ranges for small indoor spaces.

Field of View – Narrow FOV (~40°) for hallway monitoring, wide FOV (120°+) to cover large open indoor or outdoor areas. Adjustable FOV allows customizing for unique spaces.

Sensitivity – Look for multiple sensitivity settings (at least 2-3 levels) to fine tune trigger performance. Avoid over-sensitive units that false trigger often.

Output Interface – Digital output for simple on/off control applications. Analog voltage options allow more advanced interfaces with variable triggering.

Power Source – Low voltage DC units offer easy integration, while 110-240V AC PIRs can directly switch lighting and other mains voltage devices.

Weatherproofing – IP65 or higher ratings are suitable for reliable outdoor operation in all conditions. Avoid unsealed sensors outdoors.

Wireless Options – Good for adding sensors to existing buildings, integrates with wireless alarm systems. Note shorter battery life vs. wired.

Motion Sensing Tech – Some vendors offer quad (4) element pyroelectric sensing for fewer false triggers and superior performance over standard dual element units.

Price – Inexpensive PIR modules ($1-$5) may have limited range and reliability. Invest in quality sensors ($10-$50) for critical applications.

Let’s look at some recommended PIR motion detector models for common use cases:

• Security – Bosch ISC-BPR2-W12 12m PIR, Paradox MGSP480 15m Wireless PIR
• Lighting Control – PhilipsHue Smart Motion Sensor, XYZ Wave PIR Occupancy Sensor
• DIY Projects – HC-SR501 Adjustable PIR Module, Adafruit PIR Motion Sensor (comes wired for Arduino)
• Haunted Houses – FrightProps 15m Weatherproof PIR, Distortions DTRON-003z Zombie PIR
• Outdoor – DMP 310W Waterproof 30m Wireless PIR, MaxBotix MB1010 50 ft Outdoor PIR

When sourcing PIR sensors, look for reputable brands like Bosch, DSC, Paradox, MS Sedco, Adafruit, SparkFun when possible. Avoid no-name modules with limited specifications.

Buying through Amazon, specialty electronics distributors like Mouser, or directly from brands yields the best results.

PIR motion sensor modules typically cost $1 to $5 each when purchased individually. Buying bulk 10-50 pack units can reduce the price to $0.50 – $3 per sensor for high volume projects.

Wired PIR sensors with integrated housing, cabling, and mounting brackets sell for $10 to $50 each for professional installations.

Now that you’re familiar with critical PIR sensor specifications and top recommended models, you can select the right motion detection solution tailored for your specific application and requirements.

Frequently Asked Questions About PIR Triggers

What Is A Pir Trigger?

A PIR trigger refers to a passive infrared sensor used to detect motion and automatically activate or “trigger” another device when movement occurs in its sensing zone. PIR stands for passive infrared, referring to the technology the sensor uses to detect infrared radiation emitted by objects.

The radiation level changes when something moves into the PIR detector’s field of view.

Should Pir Sensitivity Be High Or Low?

For most applications, PIR sensitivity should be set moderately high to detect motion reliably but not so sensitive that the sensor false triggers.

High sensitivity ensures the PIR picks up small infrared changes from people or objects moving through the monitored area.

But an overly sensitive setting leads to false triggering from environmental sources like heaters or sunlight. Start with a medium-high level around 75% sensitivity and adjust from there.

What Does A Pir Sensor Do?

A PIR sensor detects infrared radiation changes within its lens coverage area. The pyroelectric sensor inside the PIR module monitors incoming infrared levels.

When a moving object (like a person) emits different infrared radiation than the static background, the sensor detects this change and activates its output trigger signal. This signal can control a security alarm, turn on lights, activate props, etc.

What Should Pir Be Set At?

There is no single ideal PIR sensitivity setting. It depends on the environment and application. As a starting point, set PIR sensitivity around 75% for indoor use and 50-60% outdoors, then adjust up or down as needed. Settings are often marked as minimum, medium, and maximum values. Choose medium initially and tweak from there.

What Does High Pir Sensitivity Mean?

A PIR sensor set to high sensitivity triggers on minute fluctuations in detected infrared radiation. At this setting, the sensor detects very small changes from sources like small pets, air currents, or heat reflections.

High sensitivity provides the maximum range to detect motion but also most prone to false triggering. It should only be used in stable environments.

What Does Pir Trigger Mean On A Trail Camera?

On a trail camera, the PIR trigger refers to the passive infrared motion sensor used to detect moving animals and activate the camera to snap a photo or video clip.

When an animal passes in front of the PIR sensing pattern, the detector signals the trail cam to wake up from standby and record. Faster PIRs provide better shots of moving wildlife.

What Are The 3 Settings On Pir Sensor?

Most PIR motion sensors have three main sensitivity settings:

1. Low – Detects large infrared changes from significant motion sources. Less prone to false triggers but may miss some movement.
2. Medium – Balanced setting to detect motion while filtering noise. Works for most applications.
3. High – Maximum sensitivity to the smallest infrared fluctuations. Detects all motion but also more false triggers.

Some PIRs add a time delay adjustment or advanced settings like immunity modes. But the basic 3 sensitivity levels adjust the triggering threshold.

Why Is Pir Always On?

If a PIR motion sensor seems to be continuously triggering or on, there are a few possible causes:

• Sensitivity set extremely high, detecting smallest fluctuations and false triggering. Lower sensitivity.
• PIR lens focused on heat source like HVAC vent or sunlight. Reposition sensor.
• Bad power filtering allowing electrical noise to continually trigger output. Add filtering capacitor.
• Faulty pyroelectric sensing element damaged by power surge. Replace sensor module.
• Moisture or insect inside PIR housing creating constant signals. Open housing and inspect for issues.

Which Is Better Pir Or Motion Detection?

PIR passive infrared sensing is generally better for motion detection compared to basic optical motion sensors. PIRs detect infrared radiation changes from moving body heat.

This makes them very sensitive to live objects even in low light conditions while ignoring most environmental disturbances. Simple optical motion detectors are more prone to false triggers from lighting changes, dust, etc.

How Sensitive Is A Pir Motion Sensor?

PIR sensitivity ranges from detecting large heat sources like vehicles within 20-30 feet at low settings to sensing subtle radiation changes from rodents or humans up to 60+ feet away on maximum sensitivity.

With high gain pyroelectric sensors and multi-element Fresnel lenses, modern PIRs can detect temperature differences as small as 1°F at up to 100 foot distances.

How Do You Adjust The Sensitivity Of A Pir Sensor?

Most PIR sensors have onboard jumpers, dipswitches, or potentiometers to adjust detection sensitivity from low to high. For adjustable PIR modules, turning the potentiometer clockwise increases sensitivity.

Some sensors use interchangeable Fresnel lens masks with different sensitivities. Work from medium sensitivity outward when adjusting to avoid over or under triggering initially.

How Long Does It Take For A Pir Sensor To Trigger?

Quality PIR sensors trigger in under 0.5 seconds from detecting motion across their coverage area.

Faster sensors with higher frequency pyroelectric elements and optimized electronics can respond to motion in 100-200 milliseconds.

The trigger speed determines how quickly lights activate or cameras capture images of moving objects.

What Are The Problems With Pir Sensors?

Common PIR sensor issues include false triggering, shortened range, slow response, and failure to trigger at all. False alarms are caused by high sensitivity, electrical noise, heat sources, or bad filtering. Short range and uneven coverage result from dirty or damaged lens inserts.

Slow response and no triggering can indicate component failures from surges or weather damage.

How Do You Trick A Pir Motion Sensor?

PIR sensors can be tricked or fooled in several ways:

• Move very slowly at edges of detection zone to avoid significant infrared change.
• Block sensor lens with an object so it can’t see motion.
• Use aerosol sprays to coat lens with fog that obscures infrared.
• Shine bright flashlight or infrared LED lights at sensor to blind it.
• Heat the background using hot air or radiant heaters to mask body heat changes.

Conclusion

Passive infrared (PIR) motion sensors provide an inexpensive and versatile solution for automatically triggering events and effects based on detected motion.

This guide provided an in-depth look at how basic PIR detectors function using passive infrared sensing and Fresnel lens optics.

You learned about the internal circuitry and operation of PIR sensors, key features and sensitivity controls, and how to apply them as triggers in security systems, lighting control, animatronics, and more.

Hacking and modifying PIRs for custom DIY projects opens even more possibilities when interfaced with electronics platforms like Arduino.

The buying guide gave you a solid basis for selecting PIR motion sensors based on critical specifications like detection range, field of view, sensitivity, and ruggedness for your particular usage.

With this knowledge, you can source the ideal PIR trigger solution from reputable brands to suit any motion sensing application.

Passive infrared technology will continue advancing with next generation PIRs offering smarter automatic environment adaptation, pet and noise immunity, and discipline-specific optimizations.

Wireless connectivity and integration with home/building automation systems is also on the horizon to extend PIR sensor capabilities.