火灾自动报警系统(英文)

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 sensor
I.INTRODUCTION
Automatic fire alarm control system has experienced aprocess from the simple to the complex and intelligence systemincreasingly in China. The characteristic is automatic firedetection and alarm technology has a great progress along withcomputing and detection technology development. At present, automatic fire alarm control system was used in bulk storageplant, shopping malls, high-level office buildings, hotels andother places. They were used in a number of collectionsfocused on one area of intelligent alarm control method withhigher levels of bus-type alarm control system, and in someresidential areas and commercial buildings were installed by asingle automatic fire alarm detection device. These alarmdetection 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 detectionsystem.
II. GENERAL PROJECT OF THE SYSTEM
The hardware block diagram shown in Figure 1, hardwareby temperature sensors, smoke sensors, signal processingmodule, MCU modules and automatic alarm module. Nonelectrical quantity that is through the sensing element sensors (smoke sensors and temperature sensors) will be on-sitetemperature, smoke and other non-electrical signal into anelectrical signal, as well as signals for signal processing toconvert
analogquantity to digital quantity. Finally, the sampleddata were processed and compared with the limits by MCUsystem. This system can produce local and remote auto-alarmsignals.
Temperature Ionization
Transducersmoke detector
signal
processing
PD0 PD1
SCM
auto alarm
module
T ephoneel
Inter f ace
…
Figure 1. Automatic fire alarm system structure
Ⅲ. THE HARDWARE COMPONENTS
A. Atmega16
The system used by the U.S. Atmel’s microcontrollerATmega16 microcontroller. ATmega16 is based on the AVRRISC architecture to enhance low-power 8-bit CMOSmicrocontroller. Because of its advanced instruction set and asingle clock cycle instruction execution time, ATmega16 datathroughput of up to 1 MIPS / MHz. Thereby mitigate the system in the power and the contradiction between theprocessing rate. ATmega16 has the following characteristics: 16K bytes in-system programmable Flash (with the ability toread and write at the same time, that is, RWW), 512 bytesEEPROM, 1K bytes SRAM, 32 general-purpose I / O portlines, 32 general-purpose working registers, for the JTAGboundary scan interface, support the on-chip debugging andprogramming, 3 has a more flexible mode of timer / counter (T/ C), chip internal / external interrupts, programmable serialUSART, there are initial conditions detector universal serialinterface, 8-channel 10-bit with optional
differential input stageprogrammable gain (TQFP package) of the ADC, with on-chiposcillator 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 nonvolatilememory technology production on-chip ISP Flash allows theprogram memory through the ISP serial interface or a general-purpose programmer for programming; you can also run on theAVR core among the bootstrap to program. Boot program canuse any interface to download the application to the Flashmemory area (Application Flash Memory). Application ofFlash storage area is updated when the boot Flash area (BootFlash Memory) program continues to run, RWW operationachieved. ATmega16 to become a powerful microcontroller by8-bit RISC CPU and the system programmable flash in a singlechip, for many embedded control applications provides aflexible and cost-effective solution. ATmega16 has a set ofprogramming and system development tools, including: Clanguage compiler, macro assembler, program debugger /software emulator, emulators and evaluation boards.
B. Temperature Sensor
Temperature sensor manufactured by DALLASSemiconductor DS18B20-type single intelligence temperaturesensor, its performance features include:
1)This sensor have single-bus-specific technology, either through the serial port cable also through other I / Oport lines and computer interfaces,without going throughother conversion circuits Direct output measured temperaturevalue (9-bit binary number, with sign bit).
2) Temperature range is -55 ℃ ~ +125 ℃, measurementresolution of 0. 0625 ℃.
3) Containing 64 as amended through the laser-read-onlymemory ROM.
4) Fit a variety of SCM or system machine.
5) Users can set separate ways each temperature upperand lower limit.
6) Includes parasitic power.
DS18B20 and the main chip connection diagram shown inFigure 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, atthe same time received a single output signal of the PD0 pin. Pull-up is to pull the uncertainty signal through a resistorembedded in the high places, resistance at the same timecurrent－limited . Program from the DQ pin in high impedancestate to ensure that the beginning, so that you can pull on thepull-up
resistor to the high DQ. At the same time the main chipalso can be an external site alarm buzzer.
Figure 2. ds18b20 and the main chip connection diagram.
C. Smoke Monitoring Module
Smoke sensors choose HIS-07 ion smoke detectors whenthe flow through the inside and outside the ionization chamberionization electron flow is unbalanced, collector chargescurrent until the ionization balance. In a smoke-free or non-combustion, the collector being subject to the impact ionizationcurrent statistical fluctuation, the potential to maintain abalance. Ionization current have impact when the smoke intothe ionization chamber, easily into the ionization chambersmoke outside than inside the ionization chamber of theaffected, ionization current decline in and collector to re-chargeuntil the new equilibrium potential, this potential change can beused to trigger the alarm circuit. Technical parameters such asTable 1.
TABLE I.HIS-07 ION SMOKE SENSOR THCHNICAL DATA
Table Head Table Column head
Equilibrium potential collector5.5±0.3V
Collector potential with the smoke
Reduced light rate of 1% / ft0.6V
Reduced light rate of 4% / ft2.2V
Capacitor6PF
Smoke signals are processed on the chip of choice is theMotorola company’s MC14468, MC14468 for DIP 16-pinpackage, contain oscillator, timer, latch, alarm control logiccircuit, high input impedance comparator etc. When notdetected smoke, MC14468 internal oscillator that oscillationcycle 1.67s. Each 1.67s cycle the internal power supply isprovided to the work of the entire chip. It’s all kept d etect anysmoke in addition to LED flashes, battery voltage alarm andsmoke alarm. The oscillator oscillation period becomes 40mswhen the MC14448 Once detection smoke, this timepiezoelectric buzzer driving circuit to start oscillation, start tobe able to output to maintain the high 160 ms after thecessation of 80ms.Continued during the detection of smokecessation of changes, at this time if not detected smoke beeperwill not be issued a warning sound.
In figure 3, the MC14468 1 pin joint PD1 pin of SCMwhen the ion chamber of the ion current as the scene of smokedetection and change, voltage change generation a weak side-spread seized 15, by the MC14468 internal logic processingcircuit processing, the smoke is detected by 1 pin-out highmicrocontroller for processing. 13-pin then slide rheostat is setto facilitate detection sensitivity when the led flashes and thebuzzer sounded a piercing sound of an audio alarm when thedepartment has a fire alarm signal-based.
In figure 3, the MC14468 1 pin joint PD1 pin of SCMwhen the ion chamber of the ion current as the scene of smokedetection and change, voltage change generation a weak side-spread seized 15, by the MC14468 internal logic processingcircuit
processing, the smoke is detected by 1 pin-out highmicrocontroller for processing. 13-pin then slide rheostat is setto facilitate detection sensitivity when the led flashes and thebuzzer sounded a piercing sound of an audio alarm when thedepartment has a fire alarm signal-based.
Figure 3.Smoke detection circuit
D. Auto-dial alarm module
Dial-up alarm module choices are the EX-1 dial-up moduleis a DTMF signal receiving, storing, and sending as integrationcommunications circuits. Module built-in microcontroller anddial-up management process can provide users with a varietyof signal input and output ports, in security alarm, signalacquisition, automatic control, remote communication andinformation transmission areas such as flexible application. 5groups can have cell phone or group of seven local telephonenumbers are stored, power-down is not lost; Telephone linestatus detection, automatic fault signal output ;Telephone /external switching two kinds of dial-up state control; Triggertime, nine times loop dial preset numbers; To workindependently, independent dial-up, do
not rely on telephoneand other external devices.
EX-1 wiring diagram shown in figure 4, The PD4 pin toconnect the main chip HTO , the module began to dial alarmwhen PD4 output high level signal, PD5 connection ON / OFFpin input is high level signal to open the dial-up settings, theinput does not work when this pin become low, ERR pinconnected to PD6 pin of MCU, PD6 output 1 begun to testwhether the telephone line failure, READY pin connect MCUPD7 pin detection and alarm is completed, the alarm is endwhen PD7 pin is high .
Figure 4. EX-1 wiring diagram
IV. SOFIW AREDESIGN
start
ATmega16
Initialize
N whether there are
smoke signals?
Y
R0=1
collection
temperature
signal
whether the N
alarm value?
Y
R1=1
dial-up alarm
READY=1?
Y
Figure 5.The main program flow chart
Because in the early stages of fires and the smolderingphase will produce a large number of aerosol particles and smoke particles .In the stage of incipient fire substances in thecombustion process produces a lot of heat, so should make thesmoke sensor and temperature sensor used in conjunction, firstwith the smoke sensor detects whether there is smokegeneration, then the temperature sensor detects the temperature, temperature sensor alarm value is set to 50 degrees. When thesmoke is detected R0 is 1, not smoke R0 is 0. Then test thetemperature when the temperature reaches the value ofseasonal early warning R1 is 1, the value of seasonaltemperature not to reach an early warning R1 to 0, at this timecompared to the R0 and R1 is equal to the main chip when thedial-up alarm.
V. CONCLUSION
By the cooperation of using of temperature and smokesensors, through detecting the temperature and smoke on-site, the automatic alarm system could find any fire in warehouseand send the message to managers of warehouse in the earlytime by the form of short messages.
REFERENCES
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