Passive Infrared Sensor

A passive infrared sensor is a type of optical device that detects light wavelengths beyond human vision.

Where human beings can generally see light from 400 to 700 nanometer wavelengths, infrared wavelengths span across a very broad spectrum from about 740 nanometers to 300,000 nanometers or more at the far infrared range.

Most passive infrared sensor units, especially those built into security systems, have optical filters to limit their reception to between 8,000 and 14,000 nanometers, which is the range at which human bodies glow in the infrared.

PIR sensor technology has been employed in a wide range of remote sensing residential and commercial applications because the sensors are inexpensive, long-lasting, and very reliable.

A primary feature of the passive infrared sensor that makes it popular in security systems, motion activated controls such as on public faucets in restrooms, and other interactive technology is its portability.

Since they are capable of detecting such a wide range of the infrared spectrum, special filters or light-focusing fresnel lenses can be placed atop the sensor's optical detector to customize it as well.

The fresnel lens incorporated into the passive infrared sensor is a curved plastic sheet of hundreds of minute focusing prisms, which can take weak light signals received from multiple angles and channel them all to one focal point on the sensor's detector for maximum reception.

Pyroelectricity

The earliest observation of the pyroelectric effect occurred in 314 B.C., when the ancient philosopher and scientist Theophrastus noticed that tourmaline minerals create electrical attraction when they are heated.

In piezo crystals, for instance, physical force such as bending a mineral will generate electricity. Similarly, pyroelectricity results from the interaction of the thermal and electrical properties of a crystal.

The amount of electricity produced by the pyroelectric effect is typically not enough to power other devices. This means that pyroelectricity is not a practical power generation method.

Each detector contains a wide-angle lens and a pyroelectric crystal.

When a person walks past the sensor, their body heat causes the crystal to generate pyroelectricity and the alarm is activated.

Pyroelectric sensors can be used to detect other sources of heat, such as fire.

Unlike traditional smoke detectors, a sensor that uses pyroelectricity is able to detect an actual flame even if smoke is not present.

IR Receiver Module

Very simply put, an infrared receiver module is a component that receives an infrared signal from its associated transmitter and interprets the request.

These infrared signals are transmitted to and from the IR receiver module in wavelengths of 840-960 nanometers in the near infrared range.

Many devices use an IR receiver module for wireless remote control and similar purposes, such as in television remotes or robots.

In television remote control applications, the remote sends infrared signals at a particular frequency, and the signals are received by the television. This frequency usually is set between 30 kilohertz and 60 kHz, with the most common frequencies being 36 kHz, 38 kHz and 40 kHz.

IR extenders relay the signal from one IR receiver module to another.

Additional applications that utilize an IR receiver module include three-dimensional glasses, a plethora of sensors and various human-computer interaction technologies.

HCI applications, especially as part of the Open CV library, utilize IR receiver modules in their development of technologies such as interactive whiteboards and face recognition.

IR Spectroscopy Instrumentation

IR spectroscopy instrumentation is used to elucidate what groups are present in a sample.

The IR radiation band comprises wavelengths of 800-1,000,000 nanometers. This light is invisible to the human eye, although the effects of IR radiation are felt as heat.

The radiation range used in IR spectroscopy instrumentation is 2,500-16,000 nanometers. This range is called the group frequency region.

Chemical bonds in a molecule can be made to stretch, bend or twist when exposed to IR radiation. This occurs at a wavelength that is unique for each bond and each type of vibration.

Therefore, the presence of a specific bond is characterized on an IR spectrum by the absorption of radiation at a discrete set of wavelengths.

Conventional IR spectroscopy instrumentation requires a source of radiation, a container for the sample and IR sensors to detect which wavelengths have passed through the sample.

The traditional IR spectrometer is called a dispersive grating spectrometer. This works by dividing the radiation from the IR source into two streams, with one stream passing though the sample and the other being used as a control.

IR Goggles

Infrared goggles, or IR goggles, are devices that allow the wearer to view the infrared radiation, also called thermal or heat radiation, emitted by or reflected by objects.

The electromagnetic radiation, or light, referred to as infrared has a longer wavelength than the visible light that humans can see.

The infrared light that is closest in wavelength to visible light is called "near infrared" while the infrared wavelengths that lie closer to microwaves are called "far infrared."

IR goggles take advantage of ambient infrared radiation. This allows the wearer to see objects that emit in the infrared or reflect it.

The more expensive and complex NVDs use a power source to intensify ambient infrared and visible light as they pass through a series of lenses and filters.

As a result, inexpensive IR goggles are not capable of amplifying the infrared light to the same degree as a night-vision device.

A pair of IR goggles can be crafted using welding goggles with removable lenses and sheets of filter gel.

IR Light Switch

An IR motion sensor might respond by turning on a light after detecting motion by receiving infrared signals from people, living things, or any objects producing heat.

IR sensors might also perform a task when triggered by a beam of infrared light aimed directly toward the sensor by a light emitting diode .

The IR light switch operates indoors or out to turn on lights, fans, or other electrical devices.

Sensors in an IR light switch detect this energy and translate the signal into electric current, causing a light to turn on.

When used for outdoor safety or security, the light producing device generally contains the IR light switch.

The IR light switch usually screws into the light bulb socket and a light bulb screws into the outer end of the device.

Another type of IR light switch requires attaching the device to a live wire of a room wall switch or socket.

Infrared Sensor

Many of these types of sensors only measure infrared radiation, rather than emitting it, and thus are known as passive infrared sensors.

All objects emit some form of thermal radiation, usually in the infrared spectrum. This radiation is invisible to our eyes, but can be detected by an infrared sensor that accepts and interprets it.

In a typical infrared sensor like a motion detector , radiation enters the front and reaches the sensor itself at the center of the device. This part may be composed of more than one individual sensor, each of them being made from pyroelectric materials, whether natural or artificial.

They are wired in such a way so that when the sensor detects an increase in the heat of a small part of its field of view, it will trigger the motion detector's alarm.

It is very common for an infrared sensor to be integrated into motion detectors like those used as part of a residential or commercial security system.

A set of these lenses on a motion detector can focus light from many directions, giving the sensor a view of the whole area.

A sudden change in one area of the field of view, especially one that moves, will change the way electricity goes from the pyroelectric materials through the rest of the circuit. This will trigger the motion detector to activate an alarm.