Motion sensor - a small helper for great savings

Description of the purpose, principle of operation of infrared motion sensors. How to choose a motion sensor to fit your needs.

Today, the issues of applying energy-saving technologies in everyday life are becoming increasingly relevant. The cost of electricity consumed can be significantly reduced by using at home motion sensors ("PIR" - from English - "passive infrared" - "passive infrared").

Infrared motion sensors designed to close the power circuit in the event of the appearance (movement) of a person (car, etc.) in a controlled area. Depending on the version, the sensors can be used both indoors and outdoors.

Household motion sensors use in their work the principle of constant monitoring of infrared radiation in the tracking zone. Upon the appearance of an object of sufficient mass and with a temperature exceeding the surrounding by five degrees Celsius, the general picture of the thermal field in the controlled area changes. Using a special lens (Fresnel lens), a signal is sent to the photocell, which actuates the circuit closure mechanism.

Using the checkerboard pattern of alternating “active” and “passive” zones of the common infrared field allows triggering even with the smallest movements in the controlled zone (swaying of a sitting person).

It is most convenient to use this system to turn on / off lighting, ventilation and air conditioning. Depending on the model and purpose, the response period can be adjusted.

Before purchase motion sensormust be determined by the following parameters:

• scope (enclosed space, open canopy or street). The choice of the degree of protection and the method of attachment depends on this. Motion detectors are available in moisture-proof design from IP20 to IP55. Sensors can be either built-in or mounted on brackets.

• power of switched electrical equipment. Since the sensor can be installed for just one daylight lamp, or for a complete set of ventilation and cooling of a warehouse (refrigeration, thermos type) room, models are available for switching on power consumption from two hundred watts to tens of kilowatts. Accordingly, the overall dimensions and installation conditions also change.

• the ability to fine-tune the response time, both on and off. This function is more important for industrial premises, where only a few sensors are installed on a large area, not covering it completely. In these conditions, it is important that a person has time to reach the next sensor (long corridors), or has time to perform the intended work and return to the sensor coverage area.

• response zone configuration. In this aspect, it is necessary to remember that the motion sensor controls only the visible zone (IMPORTANT: glass is an obstacle to the passage of infrared rays, therefore, it also reduces the controlled volume). Any designs, including light ones, such as a pendant lamp, sconce or curtain rod, significantly reduce the radius of actioninfrared motion sensor.

• angle of perception of the sensor. Motion sensors are available with a viewing angle of 180 ° to 360 °. The former are most often mounted on walls, and are designed to respond to entry / exit. It is generally accepted to use the full viewing angle when mounting the sensor on the ceiling, and its focus on the presence registration.

• active / passive ratio formula.This parameter determines the sensitivity of the sensor, and is most important for rest rooms, or office premises. The higher the number of alternation of active and passive zones, the more reliable will be the registration of the presence of people who do not make significant movements (some models can even be configured to respond to breathing).

Read more about the main points that you need to pay attention to when choosing a motion sensor, read here: How to choose a motion sensor to turn on the light

In addition to energy-saving functions, infrared motion sensors are an excellent option for creating an amateur intrusion alarm. Just connect them with a searchlight and a siren, and be sure that not a single thief will open the closed doors of your house, cottage or apartment.