The project over all consist of the following components: 1. Microcontroller ATMEL 89S52. 2. Temperature sensor LM-35. 3. Smoke sensor TGS-308. 4. 16x2 LCD. 5. Operational amplifier IC LM-324. 6. 12 Volts Buzzer. 7. 6 Volts Relay. 8. Potentiometers 10K. 9. 5 Volts Voltage regulator 7805. 10. BJT C-1383 NPN-type 11. Crystal oscillator 11.0592 Mhz. 12. LED’s. 13. Push button. 14. Capacitors. 15. DB-25 Connector. 16. ISP Programmer. 17. KEIL UVision-2. 18. 9 Volts Adapter. 19. Weiroboard. 20. Wiring and miscellaneous.
Step wise execution of the project is very necessary to fulfill the task. For this purpose first of all selection and purchase of all the components was done. Then the project was first designed on a breadboard. For this purpose first the microcontroller was connected with the crystal oscillator that produces 11.0592 MHz frequency to drive the microcontroller and to provide the clock frequency. After successful production of the frequency fixed 5 volts supply for the microcontroller was to be designed for which voltage regulator 7805 was used with capacitors circuitry. Output of the regulator was fed into the microcontroller’s Vcc. Until this task which is common for every microcontroller based project everything worked all well and fine. Coming to the main stream now the heat sensor LM-35 was interfaced with a comparator that gives an output voltage level for certain temperature. According to the fire environment the output of the heat sensor compares 0.5 Volts DC already set on the comparator IC, hence any increase in the temperature correspondingly increases the output of the sensor and hence the comparator IC was generating the high output thereby giving positive indication of fire.
Similarly smoke sensor TGS-308 was interfaced with the comparator. As the sensor gives certain voltage level upon positive detection of smoke so the comparator was fed with 3 Volts DC to compare with the output of the smoke sensor, as soon as the output of the smoke sensor increases beyond 3 Volts the comparator passes high logic on its output hence indicating positive presence of smoke.
The output of both these sensors is fed into the microcontroller through pins 2.0 and 2.2. The microcontroller continuously examines these pins and performs AND operation and high output of the AND operation confirms fire, there by sending the operation condition to the buzzer and displaying the location of fire on the LCD through parallel connections through port 1.
Similarly three more smoke and heat sensors’ output were also being fed into the microcontroller which deals these inputs similarly like the one stated above and hence alarming the buzzer as an output and displaying the presence and the location of the fire on LCD display. Hence giving us a flexibility to interface various sensors at a time with the microcontroller and displaying the exact location of the fire. The output current of the microcontroller is very low, as low as a few microamperes, so buzzer can not be directly driven by the microcontroller as the buzzer must need at least a few milliamperes to sound efficiently and loudly. For this purpose need for a relay to be used was felt that was energized on logic high reception from the microcontroller and in turn was activating the buzzer. Continuous examining of the respective pins of the sensors makes this project highly useful to be used in sensitive and high risk areas.
Programming of the project needs continuous examining of the pins connected to the output of the sensors and on positive indication sending data to LCD indicating the position of the fire and sounding of the alarm.