Tutorial on Smoke Detectors and Fire Alarms

The purpose of this article is to give information pertaining to the suitable application of smoke detectors used in conjunction with the fire alarm systems. The title outlines fundamental principles that must be considered in the application of early caution fire and smoke detection devices. It represents working characteristics of detectors and ecological factors, which may aid, delay, or stop the operation of fire and smoke detection devices.However, sometimes when there is a smoke from a fire it sends a message that especially alarms, if life is in danger. If fire breaks out in the daytime – there is a possibility to smell it and do something about it. But during night when everybody is asleep, fire can take the oxygen, which is required to breathe and produce toxic carbon monoxide gas, which is enough to take everyone into deadly slumber from which no one might never recover.

Smoke Detectors and Fire Alarms

A Smoke Detector device is a smoke sensing device that indicates fire. Smoke Detectors are very useful in homes, offices, schools and industries. Smoke Detectors are extraordinarily useful devices because the damage caused by fire accidents is catastrophic.Nowadays, smoke detectors and smoke alarms are very low-priced as their usage is increasing and the cost of manufacturing is decreasing.

Smoke Detector Circuit

This smoke detector circuit warns the consumer against fire accidents. It relies on the smoke that is formed due to a fire that passes between a bulb and an LDR, such that the quantity of light falling on the LDR decreases. This kind of circuit is called an optical smoke detector. This can not be used as a home smoke detector; it’s just for electronic projects. In this circuit, the resistance of LDR raises and the voltage at the bottom of the transistor is pulled high due to which the supply to the COB (chip-on-board) is finished. The sensitivity of the smoke detector depends on the distance between the bulb and LDR as well as on the setting of preset VR1. Thus, by insertion the bulb and the LDR at right distances, one may vary preset VR1 to get better sensitivity.

Some Detector Circuit
Some Detector Circuit

Types of Smoke Detectors

There are five types of smoke detectors

  • Photoelectric Smoke Detector
  • Ionization Smoke Detector
  • Projected Beam Smoke Detector
  • Aspirating Smoke Detector
  • Video Smoke Detection

Photoelectric Smoke Detector

A pulsed light beam from a light-emitting diode (LED) with its linked optics is projected across the interior of a blackened chamber that might contains smoke to be detected. A photocell, with its optics, looks to the projected beam beside a line perpendicular to the beam. When smoke enters the chamber, the smoke particles are reflect a little portion of the light beam near the photocell, which provides a voltage to be amplified and causes an alarm. The light source is monitored in front of the smoke chamber and regulated to stop variation of the light intensity from causing erratic detector performance.

Photoelectric Smoke Detector
Photoelectric Smoke Detector

Ionization Smoke Detector

A little amount of radioactive material ionizes the air within a chamber that is open to the ambient air. A calculated, small amount of electrical current is allowed to flow throughout the ionized air. Some little, solid particle products of burning that enter the chamber, as a result of fire,  interfere with the usual movement of ions (current) and when the current drops low,the alarm rings. A two-position switch, which is needed to manage sensitivity is provided.

Ionization Smoke Detector
Ionization Smoke Detector

Projected Beam Smoke Detector

The projected beam smoke detector operates on the principle of light obscuration and comprises a projected beam transmitter & lens, the light receiver and light reflector (not in all cases). The light transmitter emits an unseen beam of  light that is received by a receiver in usual condition. The receiver is calibrated to represent sensitivity level based on a percentage of whole obscuration. When the smoke obscures beam, an alarm signal is activated.

Projected Beam Smoke Detector
Projected Beam Smoke Detector

Aspirating Smoke Detector

An aspirating smoke detector is an extremely sensitive light sensor or nephelometer, that works by dynamically drawing a sample of air and additional contaminates through a pipe network into a sensing chamber. It consists of the following major components: a network of small-bore pipes, particulate filter, sensing chamber, focused light source and also a sensitive light receiver. When smoke enters the sensing chamber across the pathway of the light beam, some light is scattered or obscured by the smoke particles, which is a detected by the sensor. The output is analogue and can be triggered by multiple alarms.

Aspirating Smoke Detector
Aspirating Smoke Detector

Video Smoke Detection

Video Smoke Detection (VSD) is based on a computer analysis of video images provided by the standard video (CCTV) cameras. A video smoke detection system comprises the following components: one or more video cameras, computer and software to analyze the video signal. The computer uses a particular software to identify the unique motion and pattern of smoke. This unique signal is identified triggers an alarm.

Video Smoke Detector
Video Smoke Detector

Fire Alarm Control Panel

The control panel is the head of the fire detection and alarm system. It is responsible for monitoring a variety of alarm input devices such as manual and automatic discovery components – and activating alarm “output” devices such as a horn, bells, warning lights, emergency telephone dialers, and building controls. Control panels may range from simple units with a single input and output zone to complex computer driven systems that monitor some buildings over an entire campus.

Fire Alarm Control Panel
Fire Alarm Control Panel

There are two main manageable panel arrangements, which are conventional and addressable.Conservative or point wired fire detection and alarm systems were in use for many years as a standard method for providing emergency signaling. In a predictable system one or more circuits are routed during the protected space or building. Along every circuit, one or more detection devices are placed. Selection and placement of these detectors are needed for a multiplicity of factors including the need for automatic or manual initiation, ambient temperature and ecological conditions, the predictable type of fire, and the desired speed of response.

One or more device types are normally located along a circuit to address a variety of desires and concerns.Upon fire, one or additional detectors operate. This action closes the circuit, which the fire control panel recognizes as an urgent condition. The panel then makes active one or more signaling circuit to noise building alarms and call for emergency help. The panel may also send the signal to a further alarm panel so that it can be monitored from a remote point.

Fire Detection an Alarm System

This system informs building occupants to take evasive action to escape the dangers of a hostile fire and summons organized help to initiate or assist in fire control activities. The infinite automatic fire control &containment systems sound alarm, supervise fire control and suppression system to assure operational position is maintained. And also initiate supplementary functions involving environmental, utility & process control. The system may incorporate one or all of these functions. The system components may operate, mechanically, hydraulically and also electrically.

This is all about smoke detectors and fire alarms. A fire alarm device is that detects the presences of fire and atmospheric changes concerning to smoke. In some cases, a firm alarm is an element of a total security system, in adding to a robbery protection system. The fire alarm operates to observant people to evacuate a location in which a fire or smoke accretion is present. When functioning correctly, a fire alarm will sound to inform people of an instant fire emergency. Fire alarms can be established in homes, schools, churches and businesses, and function as the catalyst to saving lives.

For the majority fire alarms, when sounded, a beep, bell or horn noise is made. This discrete sound exists to permit the announcement to be heard. The fire alarm constructed by this project work is dependable at low cost. Furthermore, any queries regarding this article or electrical and electronics projects, please give your valuable suggestions by commenting in the comment section below. Here is a question for you, what is the function of smoke detector?

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6 Comments

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  2. Jenny Dominic says:

    This is the best thing in security systems. The only caution that we need to take is we can not light up a matchstick or a lighter in that area.

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