PIR Sensor Alarm


PIR-SENSOR-ALARM-1

This simple alarm can be used to detect the movement of human beings at a distance of 10 meters.It works both day and night and beeps shortly when there is a human movement through its detecting range. It is ideal to monitor the entry passages, stair case, corridors etc. It is highly useful to monitor the human movements in Flats, Multi storied buildings, Shops etc. A relay can also be connected for activating lights, electric alarms etc. It can be used as a Personal alarm during journey to protect luggage.

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Familiarize Electronic Components Part XVII – Motion Sensor


These are Electronic devices that detect the presence of Human beings and large Warm blooded animals (Birds and Mammals) from a distance of 5 meters or more. The most advanced form of Motion sensor is the Passive Infra Red sensor or PIR sensor. This electronic device measures the temperature in the infrared from the body of human beings and compares with the background temperature around the sensor and activates the alarm system. The heat from the human body is emitted in the form of Infrared ,and the PIR sensor can detect it from an angle of 45 degree.

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PIR Sensor based Alarm


This Passive InfraRed Alarm system can switch on a Lamp or Alarm when it detects the heat from an object like moving person. The name PIR (Passive Infrared) is given to the sensor because it receives the infrared rays passively and do not emit any infrared ray. The lamp or alarm remains on few minutes depending on the mono time setting of the PIR Sensor used. Ready to fix PIR Sensors are available with Fresnel lens to increase sensitivity and to filter ambient light. Its range is around 5 meters at 45 degree cone angle.

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PIR Sensor


Infrared is the invisible radiation lies between the Visible and Microwave portions of the electromagnetic spectrum. The term Infra means below the ability to detect visually and the term Red means colour of the light with low energy level. The Near infrared is close to the red portion of visible light and the Far infrared is close to the microwave region. Far infrared is thermal and we feel it as heat by the temperature sensors in our skin. Short and Near infrared rays cannot be detected since these are invisible as well as cool. Active infrared rays are produced from semiconductor sources but natural objects like animals including human beings emit infrared rays from the body heat. Humans at normal body temperature emits Infrared rays at the wavelength of 10 microns.PIR Sensors are used in surveillance systems to detect moving persons in protected areas.



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PIR Sensor


Infrared is the invisible radiation lies between the Visible and Microwave portions of the electromagnetic spectrum. The term Infra means below the ability to detect visually and the term Red means colour of the light with low energy level. The Near infrared is close to the red portion of visible light and the Far infrared is close to the microwave region. Far infrared is thermal and we feel it as heat by the temperature sensors in our skin. Short and Near infrared rays cannot be detected since these are invisible as well as cool. Active infrared rays are produced from semiconductor sources but natural objects like animals including human beings emit infrared rays from the body heat. Humans at normal body temperature emits Infrared rays at the wavelength of 10 microns.PIR Sensors are used in surveillance systems to detect moving persons in protected areas.



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Ferroelectricity


Ferroelectricity is the phenomenon in which a spontaneous electric polarization occurs in some materials by the application of an external electric field. Ferroelectricity was observed in Rochelle salt by Valasek in 1920 and the term was introduced in analogy to Ferromagnetism which is the magnetic property of some materials. A very good ferroelectric material is Lead Zirconate Titanate crystals used in piezoelements. The combined properties like piezoelectricity, Pyroelectricity and memory make the ferroelectric materials ideal for making sensors.

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Piezoelectricity


Piezoelectricity is the accumulation of electric charge in some solid materials such as crystals, ceramics, biological materials like bones, proteins DNA etc. The electrical charge accumulates when these materials are subjected to mechanical stress or heat. The word Piezo electricity was derived from Greek terms Piezein meaning squeeze or press and electric. The piezoelectricity is generated as a result of piezoelectric effect. The Piezoelectric effect is the linear electromechanical interaction between the electrical and mechanical states in the crystalline structure of the material.

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