The Fire Alarm System Engineering Essay

We are populating in a clip that safety and security became one of the necessary demands in all countries of life, in the center of engineering revolution which aims to do life easier and more secure, engineering has been earned by adult male in many Fieldss of his life, and because of that and to do topographic points where we live, work or even loosen up is more unafraid and safe by using a fire dismay system.

As mentioned above we will plan a fire dismay system which will alarm user if there is an indicant of a fire state of affairs. The chief purpose of all makers is to accomplish the best and the cheapest systems.

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Fire dismay system is an automatic system which detects if there an indicant of a fire state of affairs by feeling temperature or feeling a fume, which are an indicants of the changing in the environment that surrounds the system.

Fire dismay system can be considered as a manual system which activated by the user or an automatic system which activates by itself, or it can be considered both automatic and manual system.

The general architecture of the fire systems consists of the detectors itself, the commanding device ( microcontroller or personal computing machines or any logic circuits ) , and the dismay talkers ( doorbells ) and in some instances it may incorporate an car dialling devices to name the constabulary or the proprietor of the edifice.

Fire dismay systems can supply one or more of the followers:

Notifies the residents.

Controls all the fire dismay constituents in a edifice.

Notifies individuals in the encompassing country.

Biddings the fire service.

Undertaking Description and Aims

The chief purpose of this undertaking is to plan a PIC microcontroller based fire and over heat monitoring and dismay system ; the system will hold the ability to observe fume and continuously mensurate the temperature at any coveted country and expose it on an LCD ( liquid crystal show ) screen.

And when the temperature goes over a certain grade a fan will be activated in order to cut down the temperature and cool the topographic point. But if that does n’t work and the temperature still increasing an dismay will be activated in order to alarm the individuals on the environing country and the fan will be disabled in order to cut down the chance of get downing a fire.

Besides this dismay will be activated in tow more ways, either by the pull box switch which will trip the fire dismay manually or by the fume sensor that will observe any sort of fume which is frequently an indicant for the being of fire.

This fire system can be considered as a manual automatic system, it is based on many ways to alarm people that go toing in a certain topographic point -where the system is activated – for a fire state of affairs ; the first method is feeling the temperature of the country if any increasing of the temperature over a certain grade is detected by the accountant it will be displayed on the LCD and the fan will be activated, if the temperature still increasing that will bespeak a fire state of affairs so the microcontroller will trip the dismay, the 2nd method is by drawing the switch box manually by any user, and eventually when the fume detector will observe a fume in the environment the microcontroller will have the read and will trip the dismay and expose the consequence on the LCD.

Main system constituents:

PIC microcontroller as the system encephalon.

LCD to expose consequences from PIC microcontroller

Temperature detector to mensurate the air Temperature.

Smoke sensor detects if there a fume in the air.

Alarm which alert in the fire state of affairs.

Switch used for manually activate or deactivate system.

Fan to diminish the air Temperature.

1.3 System Block Diagram:

fir blo.JPG

Figure ( 1.1 ) System Block Diagram

PIC microcontroller as shown in the figure ( 1.1 ) is can be described as the encephalon of the system, which receives inputs from three parts the first 1 is the temperature detector, which measure the temperature of a certain country and base on balls it to the PIC microcontroller which will observe the temperature whether it ‘s over a certain grade or non, if the temperature grade is less than the certain degree them PIC will expose the grade on the LCD, if the temperature grade is over so the PIC microcontroller will expose the temperature grade and will set the fan to work until the temperature lessening to the normal grade.

But if the temperature grade still increasing so the PIC will see a fire state of affairs activate the system automatically including turn the fan off and will set the dismay on to alarm people to a fire state of affairs, dismay ca n’t be put on if there is non a drive circuit PIC may non be able to turn the dismay on.

The 2nd input is from fume sensor which detects if there a fume in the air, and send the consequence continuously to the PIC whether there a fume or non. And the PIC will observe the consequence if there is no fume PIC will expose the consequence on the LCD, but if there is smoke PIC will expose the consequence on the LCD and will turn the dismay on to alarm people to a fire state of affairs.

The 3rd input is from the switch by which user will be able to trip or deactivate the fire system manually. If the system detects a fume or increasing in the temperature and assumed a fire state of affairs and there is no fire the user can deactivate the system manually, and if the user happen himself in a fire state of affairs but the system has n’t detected it yet he can trip the system manually.

1.4 Plan to implement

As shown in the block diagram foremost the LCD screen must be connected to the PIC in order to expose the coveted informations, so the reading of the temperature detector will be fed to the PIC microcontroller through the ADC ( parallel to digital ) peripheral of the PIC as input so it will be processed in the PIC microcontroller so it can be displayed on the LCD screen, so we will interface the fume sensor with the PIC microcontroller and expose its position on the LCD screen.

After that an interface must be done through a drive circuit to trip and deactivate the Siren with a control signal from the PIC microcontroller, and so to do the connexion of the pull box switch.

Besides a drive circuit has to be implemented to command the system chilling fan from the PIC microcontroller.

1.5 Software Approach

Since we are planing a PIC microcontroller based system, foremost we need tools to plan and compose the package for the PIC microcontroller, so will necessitate to utilize a PIC codification compiler that is efficient and easy to utilize, so we have chosen to utilize ( MikroBasic ) compiler.

Chapter Two

Theoretical Background

2.1 Overview

In this chapter we are traveling to explicate all system difficult ware constituents and why we used them.

Several hardware constituents are required to unite the ability of feeling the temperature grade and observing fume in the air with triping the system for fire cubic decimeter

In this chapter we will present all the undertaking components with a brief about each constituent.

The undertaking chief constituents are:

PIC microcontroller as the system encephalon.

LCD to expose consequences from PIC microcontroller

Temperature detector to mensurate the air Temperature.

Smoke sensor detects if there a fume in the air.

Alarm which alert in the fire state of affairs.

Switch used for manually activate or deactivate system.

Fan to diminish the air Temperature.

2.2 PIC microcontroller

A microcontroller is an incorporate circuit consists of simple CPU which associated with support maps such as timers, consecutive and linear I/O, crystal oscillator, its memory is divided to ROM, RAM, EEPROM, PIC is designed for little or dedicated applications.

PIC used to cut down size and cost comparison to the theoretical account that uses separated CPU, memory, and I/O devices PIC besides provides a benefit of commanding non digital electronic systems.

PIC became popular in both industrial developers and hobbyists thats because of the low cost handiness, easy to plan and reprogram with brassy memory ( EEPROM ) capability.F: EnasyacoubPICpic_pl.jpg

Figure 2.1 ( PIC microcontroller )

2.2-1 Types of the PIC ‘s Pins:

The Must Pins


which mean maestro clear and it active high which mean this pin works utilizing 1but if its written as M-CLR that mean it is active low plants utilizing 0, the map of this pin is to reset the PIC which mean reset to the plan counter to return to the beginning of the executed codification. It is the PIN no. 1 in the PIC and most of the clip it is connected to the Vcc ‘logic 1 ‘ to allow the PIC work.


It is defined as a periodic fluctuation between two things based on altering in energy, frequence at which oscillator plants is normally determined by a vitreous silica crystal which vibrates at a frequence depends on it thickness when current is applied to it. Oscillator can unite inductances, resistances, and/or capacitances to find the frequence. There are two types of oscillator: internal oscillator, external oscillator such as quartz crystals.

Power supply:

The chief map of power supply is to supply system with fixed electromotive force needed, the typical electromotive force for about PICs is ( 5 V ) which indicates that there is a restriction on the electromotive force, for illustration if the PIC was provided with ( 5.5-6 V ) it will damage, less than ( 2.5 V ) PIC will non work, ( less than 4.5 and more than 2.5 ) it is a float value which mean it is non a known value for the PIC. Normally no. of power pins is 4 ; 2 pins are grounded ( VSS ) , the other two are 5 Vs ( VDD ) .

The Optional Pins

These pins are divided into groups that are called ports. Each port has a constellation registry inside the PIC and it is called TRISE registry ; which a information way registry that controls the way of informations ( input or end product ) of each pin of that port. For illustration holding TRISA cleared ( 0 which is the default ) will configure all pins of PORTA as end product.

PIC Microcontroller ( 16F876A ) which is best described as the encephalon of the system, this portion were chosen for its convenience for the undertaking because all the constituents in this undertaking must be interfaced with each in any easy and simple attack in order to salvage clip and attempt, for case we have used an LCD screen as a human interface to expose the system position, which much is easier to link the LCD to the PIC microcontroller instead than confronting an external interfacing hardware design.

2.2-2 PIC 16F876A:

PIC16F876A High-Performance RISC CPU:

Merely 35 single-word instructions

All single-cycle instructions except for plan subdivisions, which are two-cycle.

Operating velocity: DC – 20 Megahertz

Clock input DC – 200 ns direction rhythm.

Up to 8K tens 14 words of Flash Program Memory.

Up to 368 tens 8 bytes of Data Memory ( RAM )

Up to 256 tens 8 bytes of EEPROM Data Memory.

Those characteristics result because of the PIC engineering “ CMOS Technology ” :

Low-power, high-speed Flash/EEPROM engineering.

Fully inactive design.

Wide operating electromotive force scope ( 2.0V to 5.5V ) .

Commercial and Industrial temperature ranges.

Low-power ingestion.

2.3 Liquid Crystal Display ( LCD )

2.3-1 Definition and Mechanism of LCD

LCD is the short of a Liquid Crystal Display which is a thin, level panel. LCD is an electronically displayer for information which can be a text, symbols, Numberss, images or traveling images. It can be used as a proctor for computing machines, TVs, bet oning devices, reckoners, etc. figure ( 3.13 ) shows a 16A-2 LCD.

Character LCD

Figure ( 2.2 ) Liquid crystal display

2.3-2 LCD Basicss:

Simple LCDs consists of liquid crustal cell surrounded by conductive electrode, upper and lower glass, upper and lower polarizer, as shown on the figure.

Figure 2.3 ( LCD construction )

LCD shows utilize two sheets of polarising stuff with a liquid crystal between them. When an electric current passed through the liquid crystal causes the crystals to aline. Because of that visible radiation will non be able to go through through them. Therefore, each crystal is like a shutter, either leting visible radiation to go through through or barricading the visible radiation as you can see in figure ( 3.14 ) .

Because its low electrical power ingestion which allows it to be used in battery powered electronic equipment it made of any figure of pels filled with liquid crystal cells, to bring forth image in colorss or monochromatic pels must be arrayed in forepart of light beginning.

Among to its lightweight building, its portability, and its ability to be produced in much larger screen sizes than are practical building of cathode beam tubing ( CRT ) show engineering which are LCD ‘s major characteristics. Besides its low electrical power ingestion enables it to be used in battery-powered electronic equipment.

Since all the maps such as show RAM, character generator and liquid crystal driver, required for driving a dot-matrix liquid crystal show are internally provided on one bit, a minimal system can be interfaced with this controller thrust.

LCD ( Liquid Crystal Display ) screen that will be used to expose the temperature and to expose the position of the system, we have chosen an LCD screen since it ‘s the best manner to inform the user about the system position in a friendly and simple manner.

2.4 Temperature Detector:

Which is a device used to feel temperature besides known as measurement temperature device. Temperature detectors can be classified into two types contact and non-contact detectors.

2.4-1 Contact detectors

Which step its ain temperature as the environment ‘s temperature, by sing that the detector and the object are at the in thermic equilibrium which means that there is no flow temperature between them.

2.4-2 Non-contact detectors

Which receives thermic beaming power of infrared radiation radiates from some country, so its step it as the temperature of that country.

Temperature Sensor ( LM35 DZ ) this detector has been chosen due to its high quality, sensitiveness, low cost and its simple and easy end product interface.

Features of temperature Sensor ( LM35 DZ )

Calibrated straight in A° Celsius ( Centigrade )

0.5A°C truth

Rated for full -55A° to +150A°C scope

For distant applications this detector is suited

It can run from 4 to 30 Vs

The current drain is less than 60 AµA

2.5 Smoke Detector

It ‘s been used to observe fume in the air and fed back the consequence to the system. There are two methods to observe fume in the air:

Photoelectric method which besides called optical sensing. By breathing electronics from a affair such as liquid metals or gases that from electromagnetic radiation negatrons energy would be absorbent, so the emitted electronics will be detected by the sensor. The procedure is done as a visible radiation beam which goes in forepart to the visible radiation detector in the instance of no fume, but if there smoke visible radiation will reflect in angles so light beams will be scattered to the visible radiation detector which will see it as a fume setuation.

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Ionization by change overing an ion into molecule by taking or adding charges “ negatrons ” . The rule of this method is that a chamber which includes two electrodes with air between them and there is a little changeless current will be permitted but if there a fume enters the ionic chamber so the little current will be interrupted which will bespeak a fire state of affairs.

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2.6 Switch

This is an electrical device used to go through or non pass current. It is used to trip the system manually by any user in any exigency instance. Or deactivate the system manually by the user in if the system activate automatically and there is no exigency instance.

2.7 Buzzer or siren

Is besides called a pager which is an electronic device which consists figure of detectors or switches, has many applications such as auto horn, clock dismay etc…

That is used to inform the individuals at the environing country and advise them about position of the fire dismay system.

2.8 Driving circuit

Which is an electrical circuit by which an electronic device can command another device, driving circuit for illustration can be used to magnify current.



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