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 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 SYSTEM

The 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 convert analog 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.

Figure 1. Automatic fire alarm system structure

Ⅲ. THE HARDWARE COMPONENTS

A. ATmega16

The system used by the U.S. Atmelrsquo;s micro controller ATmega16 micro controller. ATmega16 is based on the AVR RISC architecture to enhance low-power 8-bit CMOS micro controller. 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 optional differential 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 micro controller 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 Sensor

Temperature 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 high impedance state to ensure that the beginning, so that you can pull on the pull-up resistor to the high D

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