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The Fire Alarm System Engineering Essay

Paper Type: Free Essay Subject: Engineering
Wordcount: 2843 words Published: 1st Jan 2015

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We are living in a time that safety and security became one of the necessary requirements in all areas of life, in the middle of technology revolution which aims to make life easier and more secure, technology has been earned by man in many fields of his life, and because of that and to make places where we live, work or even relax is more secure and safe by applying a fire alarm system.

As mentioned above we will design a fire alarm system which will alert user if there is an indication of a fire situation. The main aim of all manufacturers is to achieve the best and the cheapest systems.

Fire alarm system is an automatic system which detects if there an indication of a fire situation by sensing temperature or sensing a smoke, which are an indications of the changing in the environment that surrounds the system.

Fire alarm 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 sensors itself, the controlling device (microcontroller or personal computers or any logic circuits), and the alarm speakers (buzzers) and in some cases it may contain an auto dialling devices to call the police or the owner of the building.

Fire alarm systems can provide one or more of the following:

Notifies the occupants.

Controls all the fire alarm components in a building.

Notifies persons in the surrounding area.

Summons the fire service.

Project Description and Aims

The main aim of this project is to design a PIC microcontroller based fire and over heat monitoring and alarm system; the system will have the ability to detect smoke and continuously measure the temperature at any desired area and display it on an LCD (liquid crystal display) screen.

And when the temperature goes over a certain degree a fan will be activated in order to reduce the temperature and cool the place. But if that doesn’t work and the temperature still increasing an alarm will be activated in order to alert the persons on the surrounding area and the fan will be disabled in order to reduce the opportunity of starting a fire.

Also this alarm will be activated in tow more ways, either by the pull box switch which will activate the fire alarm manually or by the smoke detector that will detect any kind of smoke which is often an indication for the existence of fire.

This fire system can be considered as a manual automatic system, it is based on many ways to alert people that attending in a certain place -where the system is activated – for a fire situation; the first method is sensing the temperature of the area if any increasing of the temperature over a certain degree is detected by the controller it will be displayed on the LCD and the fan will be activated, if the temperature still increasing that will indicate a fire situation so the microcontroller will activate the alarm, the second method is by pulling the switch box manually by any user, and finally when the smoke sensor will detect a smoke in the environment the microcontroller will receive the read and will activate the alarm and display the result on the LCD.

Main system components:

PIC microcontroller as the system brain.

LCD to display results from PIC microcontroller

Temperature sensor to measure the air Temperature.

Smoke detector detects if there a smoke in the air.

Alarm which alert in the fire situation.

Switch used for manually activate or deactivate system.

Fan to decrease 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 brain of the system, which receives inputs from three parts the first one is the temperature sensor, which measure the temperature of a certain area and pass it to the PIC microcontroller which will detects the temperature whether it’s over a certain degree or not, if the temperature degree is less than the certain degree them PIC will display the degree on the LCD, if the temperature degree is over then the PIC microcontroller will display the temperature degree and will put the fan to work until the temperature decrease to the normal degree.

But if the temperature degree still increasing then the PIC will consider a fire situation activate the system automatically including turn the fan off and will put the alarm on to alert people to a fire situation, alarm can’t be put on if there is not a driving circuit PIC may not be able to turn the alarm on.

The second input is from smoke detector which detects if there a smoke in the air, and send the result continuously to the PIC whether there a smoke or not. And the PIC will detect the result if there is no smoke PIC will display the result on the LCD, but if there is smoke PIC will display the result on the LCD and will turn the alarm on to alert people to a fire situation.

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The third input is from the switch by which user will be able to activate or deactivate the fire system manually. If the system detects a smoke or increasing in the temperature and assumed a fire situation and there is no fire the user can deactivate the system manually, and if the user find himself in a fire situation but the system hasn’t detected it yet he can activate the system manually.

1.4 Plan to implement

As shown in the block diagram first the LCD screen must be connected to the PIC in order to display the desired data, then the reading of the temperature sensor will be fed to the PIC microcontroller through the ADC (analog to digital) peripheral of the PIC as input then it will be processed in the PIC microcontroller so it can be displayed on the LCD screen, then we will interface the smoke detector with the PIC microcontroller and display its status on the LCD screen.

After that an interface must be done through a driving circuit to activate and deactivate the siren with a control signal from the PIC microcontroller, and then to make the connection of the pull box switch.

Also a driving circuit has to be implemented to control the system cooling fan from the PIC microcontroller.

1.5 Software Approach

Since we are designing a PIC microcontroller based system, first we need tools to program and write the software for the PIC microcontroller, so will need to use a PIC code compiler that is efficient and easy to use, so we have chosen to use (MikroBasic) compiler.

Chapter Two

Theoretical Background


In this chapter we are going to explain all system hard ware components and why we used them.

Several hardware components are required to combine the ability of sensing the temperature degree and detecting smoke in the air with activating the system for fire l

In this chapter we will introduce all the project components with a brief about each component.

The project main components are:

PIC microcontroller as the system brain.

LCD to display results from PIC microcontroller

Temperature sensor to measure the air Temperature.

Smoke detector detects if there a smoke in the air.

Alarm which alert in the fire situation.

Switch used for manually activate or deactivate system.

Fan to decrease the air Temperature.

2.2 PIC microcontroller

A microcontroller is an integrated circuit consists of simple CPU which associated with support functions such as timers, serial and analog I/O, crystal oscillator, its memory is divided to ROM, RAM, EEPROM, PIC is designed for small or dedicated applications.

PIC used to reduce size and cost comparing to the model that uses separated CPU, memory, and I/O devices PIC also provides a benefit of controlling non digital electronic systems.

PIC became popular in both industrial developers and hobbyists thats because of the low cost availability, easy to program and reprogram with flash 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 master clear and it active high which mean this pin works using 1but if its written as M-CLR that mean it is active low works using 0, the function of this pin is to reset the PIC which mean reset to the program counter to return to the beginning of the executed code. It is the PIN no. 1 in the PIC and most of the time it is connected to the Vcc ‘logic 1’ to let the PIC work.


It is defined as a periodic fluctuation between two things based on changing in energy, frequency at which oscillator works is usually determined by a quartz crystal which vibrates at a frequency depends on it thickness when current is applied to it. Oscillator can combine inductors, resistors, and/or capacitors to determine the frequency. There are two types of oscillator: internal oscillator, external oscillator such as quartz crystals.

Power supply:

The main function of power supply is to provide system with fixed voltage needed, the typical voltage for almost PICs is (5 V) which indicates that there is a limitation on the voltage, for example if the PIC was provided with (5.5-6 V) it will damage, less than (2.5 V) PIC will not work, (less than 4.5 and more than 2.5) it is a float value which mean it is not a known value for the PIC. Usually no. of power pins is 4; 2 pins are grounded (VSS), the other two are 5 volt (VDD).

The Optional Pins

These pins are divided into groups that are called ports. Each port has a configuration register inside the PIC and it is called TRISE register; which a data direction register that controls the direction of data (input or output) of each pin of that port. For example having TRISA cleared (0 which is the default) will configure all pins of PORTA as output.

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PIC Microcontroller (16F876A) which is best described as the brain of the system, this part were chosen for its convenience for the project because all the components in this project must be interfaced with each in any easy and simple approach in order to save time and effort, for instance we have used an LCD screen as a human interface to display the system status, which much is easier to connect the LCD to the PIC microcontroller rather than facing an external interfacing hardware design.

2.2-2 PIC 16F876A:

PIC16F876A High-Performance RISC CPU:

Only 35 single-word instructions

All single-cycle instructions except for program branches, which are two-cycle.

Operating speed: DC – 20 MHz

Clock input DC – 200 ns instruction cycle.

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

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

Up to 256 x 8 bytes of EEPROM Data Memory.

Those features result because of the PIC technology “CMOS Technology”:

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

Fully static design.

Wide operating voltage range (2.0V to 5.5V).

Commercial and Industrial temperature ranges.

Low-power consumption.

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, flat panel. LCD is an electronically displayer for information which can be a text, symbols, numbers, images or moving pictures. It can be used as a monitor for computers, TVs, gaming devices, calculators, etc. figure (3.13) shows a 16Ã-2 LCD.

Character LCD

Figure (2.2) LCD

2.3-2 LCD Basics:

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 structure)

LCD displays utilize two sheets of polarizing material with a liquid crystal between them. When an electric current passed through the liquid crystal causes the crystals to align. Because of that light will not be able to pass through them. Therefore, each crystal is like a shutter, either allowing light to pass through or blocking the light as you can see in figure (3.14).

Because its low electrical power consumption which allows it to be used in battery powered electronic equipment it made of any number of pixels filled with liquid crystal cells, to produce image in colours or monochrome pixels must be arrayed in front of light source.

Among to its lightweight construction, its portability, and its ability to be produced in much larger screen sizes than are practical construction of cathode ray tube (CRT) display technology which are LCD’s major features . Also its low electrical power consumption enables it to be used in battery-powered electronic equipment.

Since all the functions such as display RAM, character generator and liquid crystal driver, required for driving a dot-matrix liquid crystal display are internally provided on one chip, a minimum system can be interfaced with this controller drive.

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

2.4 Temperature Sensor:

Which is a device used to sense temperature also known as measurement temperature device. Temperature sensors can be classified into two types contact and non-contact sensors.

2.4-1 Contact sensors

Which measure its own temperature as the environment’s temperature, by considering that the sensor and the object are at the in thermal equilibrium which means that there is no flow temperature between them.

2.4-2 Non-contact sensors

Which receives thermal radiant power of infrared radiation radiates from some area, then its measure it as the temperature of that area.

Temperature Sensor (LM35 DZ) this sensor has been chosen due to its high quality, sensitivity, low cost and its simple and easy output interface.

Features of temperature Sensor (LM35 DZ)

Calibrated directly in ° Celsius (Centigrade)

0.5°C accuracy

Rated for full -55° to +150°C range

For remote applications this sensor is suitable

It can operate from 4 to 30 volts

The current drain is less than 60 µA

2.5 Smoke Detector

It’s been used to detect smoke in the air and fed back the result to the system. There are two methods to detect smoke in the air:

Photoelectric method which also called optical detection. By emitting electronics from a matter such as liquid metals or gases that from electromagnetic radiation electrons energy would be absorptive, then the emitted electronics will be detected by the detector. The process is done as a light beam which goes in front to the light sensor in the case of no smoke, but if there smoke light will reflect in angles then light beams will be scattered to the light sensor which will consider it as a smoke setuation.

http://upload.wikimedia.org/wikipedia/commons/thumb/f/f5/Photoelectric_effect.svg/275px-Photoelectric_effect.svg.png http://upload.wikimedia.org/wikipedia/commons/thumb/4/49/OpticalSmokeDetector.png/250px-OpticalSmokeDetector.png

Ionization by converting an ion into molecule by removing or adding charges “electrons”. The principle of this method is that a chamber which includes two electrodes with air between them and there is a small constant current will be permitted but if there a smoke enters the ionic chamber then the small current will be interrupted which will indicate a fire situation.



2.6 Switch

This is an electrical device used to pass or not pass current. It is used to activate the system manually by any user in any emergency case. Or deactivate the system manually by the user in if the system activate automatically and there is no emergency case.

2.7 Buzzer or siren

Is also called a beeper which is an electronic device which consists number of sensors or switches, has many applications such as car horn, clock alarm etc…

That is used to inform the persons at the surrounding area and notify them about status of the fire alarm system.

2.8 Driving circuit

Which is an electrical circuit by which an electronic device can control another device, driving circuit for example can be used to amplify current.


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