Fire alarm system


The safety and security is the most important issues those days and it is the main aim of all manufacturers to achieve the best and cheap systems.

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 dialing 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.[1]
  • Controls all the fire alarm components in a building.[1]
  • Notifies persons in the surrounding area.[1]
  • Summons the fire service.[1]

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 go over a certain degree a fan will be activated in order to reduce the temperature and cool the place and if that doesn't work and the temperature still increasing an alarm will be activated in order to notify 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.


General Idea Block Diagram

Components and parts list

  1. 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. 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.
  3. Temperature Sensor (LM35 DZ) this sensor has been chosen due to its high quality, sensitivity, low cost and its simple and easy output interface.
  4. Smoke Detector it's been used to detect smoke in the air and fed back the result to the system.
  5. Switch (it is used to activate or deactivate the system manually by the user in any emergency case).
  6. Buzzer or siren (that is used to inform the persons at the surrounding area and notify them about status of the fire alarm system).

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.

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.


  1. PICmicro Family Tree", PIC16F Seminar Presentation
  3. Microchip Technology (2008-02-27). "Microchip Technology Delivers Six Billionth PIC Microcontroller". Press release.

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