Design And Construction Of A Simple Smoke Detector

ABSTRACT

This simple smoke detector is highly sensitive but inexpensive. It uses a Darlington-pair amplifier employing two npn transistors and an infrared photo-interrupter module as the sensor. The circuit gives audio-visual alarm whenever thick smoke is present in the environment. The photo-interrupter module (H21A1) consists of a gallium-arsenide infrared LED coupled to a silicon phototransistor in a plastic housing. The slot (gap) between the infrared diode and the transistor allows interruption of the signal with smoke, switching the module output from ‘on’ to ‘off’ state.

1.0                                                      INTRODUCTION

In modern society, it is impossible to imagine house or building without a fire accident detector. Modern houses require a continuous installation of fire detector. Not only industry, but also in the household. Take the case of a duplex that experience a fire accident without a detector that means everything in that building will get burnt even human beings. But in a case whereby fire alarm is installed that means every one in that building will be alerted and also fire security bodies will also be informed for quick security action. The same thing can also happen to our offices and industries. In order to notify residence of any building in the presence of fire accident, a fire alarm system is used.

An automatic fire alarm system is designed to detect the unwanted presence of fire by monitoring environmental changes associated with combustion. In general, a fire alarm system is classified as either automatically actuated, manually actuated, or both. Automatic fire alarm systems are intended to notify the building occupants to evacuate in the event of a fire or other emergency, report the event to an off-premises location in order to summon emergency services, and to prepare the structure and associated systems to control the spread of fire and smoke.

1.1                                  AIM OF THE PROJECT

The objective of this work is to construct a device that will detect the unwanted presence of fire by monitoring environmental changes associated with combustion and smoke.

1.2                                          OBJECTIVE OF THE PROJECT

At the end of this work the student involved shall be able:

1. to know the most way of fire detection and alarm signaling systems.
2. To know how use photo-interrupter module (H21A1)
3. To know the operation of the system

1.3                                           PURPOSE OF THE PROJECT

The field of fire detection has advanced to where smoke detectors and alarm devices have combined to become life-safety systems. The purpose of an automatic fire-alarm system is to detect an occurrence, alert and notify the occupants to take action.

1.4                                      SIGINIFICANCE OF THE PROJECT

The primary advantage of a home fire alarm system is increased reliability and the ability to place alarms and bells exactly where needed. However, the reason most people have them is that they wanted a burglar alarm system and the cost of adding fire alarm features to a residential burglary system is relatively small.

Another advantage is that they are the only way to obtain remote monitoring services. This becomes important in cases where family members may not be capable of escaping from a fire without assistance. For example, if you have an older or physically impaired person in your home and a fire started when no one was home to assist that person, alarms alone might not be enough to assure their safety.

A feature of most monitoring services is the ability to keep special information on the residence which comes up on the computer screen whenever an alarm is received from that home. Thus, if there is a disabled person in the home who needs special assistance this fact will be known to the operator and can be passed along to the fire department when they are called

1.5                                SCOPE OF THE PROJECT

Smoke sensor circuit that detects the outflow of smoke and alerts the user via audio and visual indications. The heart of this engineering project is a smoke sensor, photo-interrupter module (H21A1). The output signal from this smoke sensor module is used to drive a darlinton transistor that drives the alarm. The darlintin transistor works as a tone generator, the frequency of tone can be altered by varying the preset VR2.

1.6                                       APPLICATION OF THE PROJECT

Fire detection, alarm and signaling systems play an important role in:

1. homes
2. factory

• offices

1. worship centers
2. industrial, fire protection

1.7                               PARTS OF FIRE ALARM

Fire alarm composed of the following parts:

• Primary Power supply: Commonly the non-switched 240 Volt Alternating Current source supplied from a commercial power utility.
• Secondary (backup) Power supplies: This component, commonly consisting of sealed lead-acid storage batteries or other emergency sources including generators, is used to supply energy in the event of a primary power failure.
• Initiating Devices: This component acts as an input to the fire alarm control unit and are either manually or automatically actuated. Examples would be devices pull stations, heat detectors, or smoke detectors. Heat and smoke detectors have different categories of both kinds.

1.7                        LIMITATION OF THE PROJECT

They sound an unbearable, very loud noise to alert anyone within the structure that somewhere there is a fire.

1.8                        PROJECT WORK ORGANISATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this work is on the introduction to an automatic fire alarm using photo-interrupter module (H21A1). In this chapter, the background of the study, significance, scope of an automatic fire alarm using photo-interrupter module (H21A1), objective of the fire alarm using photo-interrupter module (H21A1), application of a simple fire alarm using photo-interrupter module (H21A1), limitation and problem of an automatic fire alarm using photo-interrupter module (H21A1), advantages of a simple fire alarm using photo-interrupter module (H21A1)was discussed.

Chapter two is on literature review of the study. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.