Automatic fire alarm system based on MCU Abstract: The paper introduced an automatic warehouse fire a1arm system based on MCU. The system was mainly made up of ATmega16, temperature sensors, smoke sensors, and EX-1 auto dialed alarm module. In the system, temperature signals were transformed to serial data, and smoke signals were transformed to voltage signals. All the data were processed by MCU. When the surveillance system checked fire in warehouse, alarm signal was turn on, meanwhile the messages were transmitted to managers through EX-1. Application of the system was convenient to deal with fire in-time, efficiently by warehouse manager.Keywords: fire alarm transducer;smoke sensor system;ATmega16;temperature transducer;smoke sensorI. INTRODUCTIONAutomatic fire alarm control system has experienced a process from the simple to the complex and intelligence system increasingly in China. The characteristic is automatic fire detection and alarm technology has a great progress along with computing and detection technology development. At present, automatic fire alarm control system was used in bulk storage plant, shopping malls, high-level office buildings, hotels and other places. They were used in a number of collections focused on one area of intelligent alarm control method with higher levels of bus-type alarm control system, and in some residential areas and commercial buildings were installed by a single automatic fire alarm detection device. These alarm detection devices fail to report sometimes, or misinformation. Its reliability is not high because of using single sensor. Therefore, it is needed to develop a simple structure, low cost, high reliability, fast responding, automatic fire detection system.II. GENERAL PROJECT OF THE SYSTEMThe hardware block diagram shown in Figure 1, hardware by temperature sensors, smoke sensors, signal processing module, MCU modules and automatic alarm module. Non electrical quantity that is through the sensing element sensors (smoke sensors and temperature sensors) will be on-site temperature, smoke and other non-electrical signal into an electrical signal, as well as signals for signal processing to convertanalog quantity to digital quantity. Finally, the sampled data were processed and compared with the limits by MCU system. This system can produce local and remote auto-alarm signals.Temperature IonizationTransducer smoke detectorsignalprocessingPD0 PD1SCMauto alarmmoduleT ephoneelInter f ace…Figure 1. Automatic fire alarm system structureⅢ. THE HARDWARE COMPONENTSA. Atmega16The system used by the U.S. Atmel’s microcontroller ATmega16 microcontroller. ATmega16 is based on the AVR RISC architecture to enhance low-power 8-bit CMOS microcontroller. Because of its advanced instruction set and a single clock cycle instruction execution time, ATmega16 data throughput of up to 1 MIPS / MHz. Thereby mitigate the system in the power and the contradiction between the processing rate. ATmega16 has the following characteristics: 16K bytes in-system programmable Flash (with the ability to read and write at the same time, that is, RWW), 512 bytes EEPROM, 1K bytes SRAM, 32 general-purpose I / O port lines, 32 general-purpose working registers, for the JTAG boundary scan interface, support the on-chip debugging and programming, 3 has a more flexible mode of timer / counter (T / C), chip internal / external interrupts, programmable serial USART, there are initial conditions detector universal serial interface, 8-channel 10-bit with optionaldifferential input stage programmable gain (TQFP package) of the ADC, with on-chip oscillator of programmable watchdog timer, an SPI serial port, as well as six can be selected by software power-saving mode.The chip is based on Atmel high-density nonvolatile memory technology production on-chip ISP Flash allows the program memory through the ISP serial interface or a general-purpose programmer for programming; you can also run on the AVR core among the bootstrap to program. Boot program can use any interface to download the application to the Flash memory area (Application Flash Memory). Application of Flash storage area is updated when the boot Flash area (Boot Flash Memory) program continues to run, RWW operation achieved. ATmega16 to become a powerful microcontroller by 8-bit RISC CPU and the system programmable flash in a single chip, for many embedded control applications provides a flexible and cost-effective solution. ATmega16 has a set of programming and system development tools, including: C language compiler, macro assembler, program debugger / software emulator, emulators and evaluation boards.B. Temperature SensorTemperature sensor manufactured by DALLAS Semiconductor DS18B20-type single intelligence temperature sensor, its performance features include:1)This sensor have single-bus-specific technology, either through the serial port cable also through other I / O port lines and computer interfaces,without going through other conversion circuits Direct output measured temperature value (9-bit binary number, with sign bit).2) Temperature range is -55 ℃~ +125 ℃, measurement resolution of 0. 0625 ℃.3) Containing 64 as amended through the laser-read-only memory ROM.4) Fit a variety of SCM or system machine.5) Users can set separate ways each temperature upper and lower limit.6) Includes parasitic power.DS18B20 and the main chip connection diagram shown in Figure 2: DS18B20 number one pin grounded, then on the 3rd pin high and the 2nd pin then a 5. 1K of the pull-up resistor, at the same time received a single output signal of the PD0 pin. Pull-up is to pull the uncertainty signal through a resistor embedded in the high places, resistance at the same time current－limited . Program from the DQ pin in highimpedance state to ensure that the beginning, so that you can pull on the pull-up resistor to the high DQ. At the same time the main chip also can be an external site alarm buzzer.Figure 2. ds18b20 and the main chip connection diagram.C. Smoke Monitoring ModuleSmoke sensors choose HIS-07 ion smoke detectors when the flow through the inside and outside the ionization chamber ionization electron flow is unbalanced, collector charges current until the ionization balance. In a smoke-free or non-combustion, the collector being subject to the impact ionization current statistical fluctuation, the potential to maintain a balance. Ionization current have impact when the smoke into the ionization chamber, easily into the ionization chamber smoke outside than inside the ionization chamber of the affected, ionization current decline in and collector to re-charge until the new equilibrium potential, this potential change can be used to trigger the alarm circuit. Technical parameters such as Table 1.TABLE I.HIS-07 ION SMOKE SENSOR THCHNICAL DATATable Head Table Column headEquilibrium potential collector 5.5±0.3VCollector potential with the smokeReduced light rate of 1% / ft 0.6VReduced light rate of 4% / ft 2.2VCapacitor 6PFSmoke signals are processed on the chip of choice is the Motorola company’s MC14468, MC14468 for DIP 16-pin package, contain oscillator, timer, latch, alarm control logic circuit, high input impedance comparator etc. When not detected smoke, MC14468 internal oscillator that oscillation cycle 1.67s. Each 1.67s cycle the internal power supply is provided to the work of the entire chip. It’s all kept detect any smoke in addition to LED flashes, battery voltage alarm and smoke alarm. The oscillator oscillation period becomes 40ms when the MC14448 Once detection smoke, this time piezoelectric buzzer driving circuit to start oscillation, start to be able to output to maintain the high 160 ms after the cessation of 80ms.Continued during the detection of smoke cessation of changes, at this time if not detected smoke beeper will not be issued a warning sound.In figure 3, the MC14468 1 pin joint PD1 pin of SCM when the ion chamber of the ion current as the scene of smoke detection and change, voltage change generation a weak side-spread seized 15, by the MC14468 internal logic processing circuit processing, the smoke is detected by 1 pin-out high microcontroller for processing. 13-pin then slide rheostat is set to facilitate detection sensitivity when the led flashes and the buzzer sounded a piercing sound of an audio alarm when the department has a fire alarm signal-based.In figure 3, the MC14468 1 pin joint PD1 pin of SCM when the ion chamber of the ion current as the scene of smoke detection and change, voltage change generationa weak side-spread seized 15, by the MC14468 internal logic processing circuit processing, the smoke is detected by 1 pin-out high microcontroller for processing. 13-pin then slide rheostat is set to facilitate detection sensitivity when the led flashes and the buzzer sounded a piercing sound of an audio alarm when the department has a fire alarm signal-based.Figure 3.Smoke detection circuitD. Auto-dial alarm moduleDial-up alarm module choices are the EX-1 dial-up module is a DTMF signal receiving, storing, and sending as integration communications circuits. Module built-in microcontroller and dial-up management process can provide users with a variety of signal input and output ports, in security alarm, signal acquisition, automatic control, remote communication and information transmission areas such as flexible application. 5 groups can have cell phone or group of seven local telephone numbers are stored, power-down is not lost; Telephone line status detection, automatic fault signal output ;Telephone / external switching two kinds of dial-upstate control; Trigger time, nine times loop dial preset numbers; To work independently, independent dial-up, do not rely on telephone and other external devices.EX-1 wiring diagram shown in figure 4, The PD4 pin to connect the main chip HTO , the module began to dial alarm when PD4 output high level signal, PD5 connection ON / OFF pin input is high level signal to open the dial-up settings, the input does not work when this pin become low, ERR pin connected to PD6 pin of MCU, PD6 output 1 begun to test whether the telephone line failure, READY pin connect MCU PD7 pin detection and alarm is completed, the alarm is end when PD7 pin is high .Figure 4. EX-1 wiring diagramIV. SOFIW AREDESIGNstartATmega16InitializeNwhether there aresmoke signals?YR0=1collectiontemperaturesignalwhether the Nalarm value?YR1=1dial-up alarmREADY=1?YFigure 5. The main program flow chartBecause in the early stages of fires and the smoldering phase will produce a large number of aerosol particles and smoke particles .In the stage of incipient fire substances in the combustion process produces a lot of heat, so should make the smoke sensor and temperature sensor used in conjunction, first with the smoke sensor detects whether there is smoke generation, then the temperature sensor detects the temperature, temperature sensor alarm value is set to 50 degrees. When the smoke is detected R0 is 1, not smoke R0 is 0. Then test the temperature when the temperature reaches the value of seasonal early warning R1 is 1, the value of seasonal temperature not to reach an early warning R1 to 0, at this time compared to the R0 and R1 is equal to the main chip when the dial-up alarm.V. CONCLUSIONBy the cooperation of using of temperature and smoke sensors, through detecting the temperature and smoke on-site, the automatic alarm system could find any fire in warehouse and send the message to managers of warehouse in the early time by the form of short messages.REFERENCES[1] Shunning Miao,Guangming Xiong,Yongping Li etc.Automatic Fire Alarm System Design and Research, Equipment Manufacturing Technology, 2006(2), P909.[2] Liang Ge, Qi Cong. Intelligent Analysis of office building fire.[3] Ti Zhou. Building Fire System Design, Yunnan Construction,2008(6).[4] Honeywell (Honeywel1)'s construction equipment Monitoring System, Intelligent Building and City Information, 2008(4).[5] Derek Clements-Croome, Intelligent buildings: design, management and operation, Thomas Telford Publishing, 2004.[6]Zhang Huazhong, Commanding System of Fire Automatic Alarm and Fire Control Linkage based on Internet, Computer Engineering, 2001.[7] ANSI, Radiant Energy-Sensing Fire Detectors for Automatic Fire Alarm Signaling,US: ANSI/FMRC FM3260-2004.。