House Alarm

House alarms are the electronic alarms, which informs the specific dangers such as fire or gas leakage and from intruders (thieves) and protect the users from the disasters or from theft. Sensors are included to the responsive device to detect the intrusion or the disasters, when it senses the disaster or the person it starts shattering sound.

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Alarm types

Burglar or house alarms are mainly distinguished into two types, Indoor Alarms, for indoor use and the second one is out door alarm meant for out door use. Probably indoor alarms are more compatible than out door alarms, because, outdoor alarms may possibly detect false alarms. False alarm means detecting the false person, for example, if person walks in a road, when he is nearing to the alarm it will starts screaming. This is behaviour is unusual in indoor alarms, than a outdoor alarm.

Types of Indoor alarms

Passive infrared detectors (PIR) are most probable used alarm in house and in factories due to its affordable and reliable functionality. The term passive means it doesn’t need to generate and it use its own energy More advanced security systems include passive infrared (PIR) motion detectors. This sensor grabs the infrared energy which is emitted by an intruder's body heat. When an intruder walks into the field of view of the detector, the sensor detects a sharp increase in infra-red energy. Of course, there will always be gradual fluctuation of heat energy in an area, therefore, PIR detectors are designed to trigger the alarm, only when infra-red energy levels changes very rapidly.

There must be motion of an object either towards or away from the receiver.

The motion of the object must cause a change in the ultrasonic frequency to the receiver relative to the transmitting frequency.

From these two possibilities, the Doppler shift method detects the intruders

Disaster Detector

Microwave detector: In this, the detector emits microwave signal on the object, if there is no motion in object, then there will be no change in microwave reflection. If there is a change in object movement, then it causes the change in microwave reflection. By noticing these steep changes in reflection of frequency, it detects the intruders.

Ultraviolet Flame detector: Ultraviolet (UV) detectors work with wavelengths shorter than 300 nm. These detectors detect fires and explosions, within 3–4 milliseconds due to the UV radiation emitted at the instant of their explosion. False alarms can be triggered by UV sources such as lightning, arc welding, radiation, and sunlight. In order to reduce false alarm a time delay of 2-3 seconds is often included in the UV Flame detector design.

Infrared Flame detector: Infrared (IR) flame detectors work within the infrared spectral band. Hot gases emit a specific spectral pattern in the infrared region, which can be sensed with a thermal imaging camera (TIC) a type of thermo graphic camera. False alarms can be caused by other hot surfaces in the area. A typical frequency where single frequency IR flame detector is sensitive is in the 4.4 micrometer range. Typical response time is 3-5 seconds.