【正文】 er power consumption than NMOS. Surely this change in technology must affect our design of hardware at both the chip and the system level. At the chip level, single chips are now being produced which are equivalent to board levels of only the previous year or two. These chips have microprocessor, memory in RAM and ROM, IO Ports both serial and parallel, A/D timer, flags and other functions on chip. At the system level, the new chips make new architectures possible. The objective of this paper is to show how technology can influence system architecture in the field of fire control. The new high density single chip microcontrollers are incorporated in the design of a large scale system and yet we obtain a smaller system with a better performance. In terms of fire detection and alarm monitoring, this is reflected directly in the local station hardware, because of their remoteness and power supply requirements. A plete local station can be designed around a single CMOS chip with power consumption of a few m W depending on system operation. This approach reduces the cost and plexity of design, implementation and maintenance and provides easily expandable and portable design. This implementation was not possible with old technology. Most of fire detection/monitoring systems available are tailored towards a specific application and lack the use of recent advances in CMOS VLSI technology. In this study, we develop a fire detection/monitoring system which is general in concept, readily implementable in a multitude of applications for early detection of a fire before it bees critical, for equipment and evacuation of personnel. Here, we propose a central control and distributed control/detection/monitoring with adequate munication, where use is made of singlechip microcontrollers in the local stations, thus improving controllability and observability of the monitoring process.2 Detection and alarm devicesA basic fire detection system consists of two parts, detection and annunciation. An automatic detection device, such as a heat, smoke or flame detector, ultraviolet or infrared detectors or flame flicker, is based on detecting the byproduct of a bustion. Smoke detectors, of both ionization and optical types, are the most monly used detector devices. When a typical detector of this type enters the alarm state its current consumption increases from the pA to the mA range (say, from a mere 15pA in the dormant mode to 60 mA) in the active mode. Inmany detectors the detector output voltage is well defined under various operating conditions, such as thosegiven in Table 1:Table 1 Typical detector voltage output levelsvoltage levelDetector condition22VDetector is in open circuit condition13V~22Vdetector is normal1V~13Vdetector is in an alarm state1Vdetector is in short circuit conditionThe more sensitive the detector, the more susceptible it is to false alarms. In order to control the detector precisely, either of the following methods is used: a coincidence technique can be built into the detector, or a filtering technique such that a logic circuit bees active only if x alarms are detected within a time period T. The detection technique depends greatly on the location and plant being protected。結(jié)束語設(shè)計的煙霧超標(biāo)報警自動排氣電路，選用MQ2煙霧傳感器，AT89S51單片機(jī)、語音芯片ISD1820PY等器件，實現(xiàn)了煙霧檢測、語音報警、自動排氣等功能。語音報警中的退耦電容可以改變音質(zhì)。因此，本論文中的可燃性報警器滿足檢測要求。經(jīng)實驗的標(biāo)定，：濃度（%LEL）濃度誤差濃度（%LEL）濃度誤差0050553553101600154652203703251755305802353854402903455955%，在所規(guī)定誤差范圍177。 濃度（%）電壓（V）01020304050607080901000從該表中可以看出，電壓值與煙霧濃度之間是非線性關(guān)系，為了實時顯示氣體濃度，需要對其進(jìn)行線性化處理，使顯示的煙霧濃度與實際誤差在177。MQ2為煙霧傳感器，電路采用交流供電，220V交流市電從插頭引入電路，經(jīng)電源變壓器降壓后變?yōu)橹绷?，直流電壓直接供傳感器MQ2的加熱絲hh工作，加熱絲給傳感器MQ2預(yù)熱一定時間后，才能正常檢測煙霧。如果有，則表示振蕩電路正常。(5)用示波器檢測振蕩電路，主要是檢測119引腳。(3)檢測P 3口或P2 口的空閑電壓是否有5V電壓，如果沒有，說明單片機(jī)系統(tǒng)沒有工作。(2) 用萬用表檢測31引腳是否有5V電壓。根據(jù)本設(shè)計的實際情況，就要先焊電阻、插槽、晶振、瓷片電容、電解電容，最后焊接煙霧傳感器和喇叭。如果經(jīng)檢測沒有問題可以工作，就可以在焊接板上開始對元器件進(jìn)行焊接。 硬件制作在Proteus軟件中仿真無誤后就可以進(jìn)行安裝、焊接元器件。(4) 仿真運(yùn)行，“debug”—“execute”。(2) 在元器件庫中選擇需要的元器件，再擺放好元器件，設(shè)定好參數(shù)，最后連接電路圖。（由于語音芯片、煙霧傳感器以及風(fēng)扇等元器件在Proteus元器件庫中沒有收錄，此次仿真過程中用電位器表示煙霧傳感器，用蜂鳴器表示語音報警，用發(fā)光二極管代表風(fēng)扇。在編譯方面，它也支持IAR、Keil和MPLAB等多種編譯器。Proteus是世界上著名的EDA工具(仿真軟件)，從原理圖布圖、代碼調(diào)試到單片機(jī)與外圍電路協(xié)同仿真，一鍵切換到PCB設(shè)計，真正實現(xiàn)了從概念到產(chǎn)品的完整設(shè)計。它不僅具有其它EDA工具軟件的仿真功能，還能仿真單片機(jī)及外圍器件，它是目前最好的仿真單片機(jī)及外圍器件的工具。最后通過progisp把編譯、調(diào)試正確的程序下載到AT89S51芯片中。右邊 target 1 右鍵彈出框，找到output，再找到creat hex fi:前面復(fù)選框選中 OK。編譯前要進(jìn)行一個重要的操作。然后保存這個文件filesave彈出框save as 填寫你要保存的文件名。彈出一個框，選擇“否”。為了便于集中管理建議新建一個文件夾（上面第二個圖標(biāo)）。 程序編譯及調(diào)試界面編譯及調(diào)試具體的步驟首先打開Keil uVision。jidianqi=0。 jidianqi=1。 yuyin=0。} void main() //主函數(shù){ yanwu=1。y0。x0。 void delay1(uint z) //延時子程序 1ms{ uint x,y。 sbit yuyin=P1^1。根據(jù)整體軟件流程圖用C語言編寫程序。程序初始化結(jié)束后，系統(tǒng)進(jìn)入監(jiān)控狀態(tài)。4．系統(tǒng)軟件設(shè)計 。二極管D2的作用是保護(hù)繼電器。三極管是處于飽和導(dǎo)通還是處于截止斷開，則由其基極B控制。繼電器中開關(guān)動作受三極管控制，當(dāng)三極管處于飽和導(dǎo)通狀態(tài)時，集電極電流驅(qū)動繼電器動作，開關(guān)閉合，電機(jī)回路導(dǎo)通，電機(jī)開始工作。自動排氣電路主要包括5V繼電器和排氣扇。減小該電容值，可使噪聲能量沖擊的幅度變小、寬度變窄；故選用10uF/。此電容可以有隔直（隔斷直流電壓）和耦合（耦合音頻的交流信號）。芯片穩(wěn)定工作后，BYPASS的電壓值約為VCC的一半，改變BYPASS外接電容的容值大小，可以有效抑制噪聲?！?”、“－”輸出端可以很好地抵消共模信號，有效抑制共模噪聲。通過接在1管腳和8管腳間接電解電容（1腳接電容+極）來改變增益，斷開時增益為20。LM386的封裝形式有塑封8引線雙列直插式和貼片式。為使外圍元件最少，電壓增益內(nèi)置為20。音頻放大電路中采用的芯片為LM386。在直通模式下，直通開關(guān)閉合，對話筒說話會從喇叭里擴(kuò)音播放出來，構(gòu)成喊話器功能，由于該模式下的話筒放大同時經(jīng)過AGC自動增益調(diào)節(jié)和帶通濾波器，其音質(zhì)比通常的話筒放大器要好很多，而且不會出現(xiàn)喇叭過載的情況。按住S1(REC)錄音按鍵不放即錄音，RECLED燈會亮起，松開按鍵錄音停止。平時FT端為低，要實現(xiàn)直通功能，需將FT端接高電平，同時REC、PLAYE和PLAYL保持低。振蕩電阻(ROSC)：此端接振蕩電阻至VSS，由振蕩電阻的阻值決定錄放音的時間。單端使用必須在輸出端和喇叭之間接耦合電容，而雙端輸出既不用電容又能將功率提高至4倍。自動增益控制(AGC)：AGC動態(tài)調(diào)整前置增益以補(bǔ)償話筒輸入電平的寬幅變化，使得錄制變化范圍很大的音量(從耳語到喧囂聲)時失真都能保持最小。話筒參考(MIC REF)：此端是前置放大器的反向輸入。外接話筒應(yīng)通過串聯(lián)電容耦合到此端。話筒輸入(MIC)：此端連至片內(nèi)前置放大器。此外，放音遇到EOM標(biāo)志時，此端輸出一個低電平脈沖。持續(xù)至此端回到低電平，或遇到EOM標(biāo)志，或內(nèi)存結(jié)束，放音結(jié)束后自動進(jìn)入節(jié)電狀態(tài)。放音后，可自動釋放PLAYE。邊沿觸發(fā)放音(PLAYE)：當(dāng)此管腳有一個上升沿時，可以驅(qū)動芯片開始進(jìn)行放音。直到REC變低或芯片內(nèi)存錄滿后，錄音結(jié)束，芯片自動寫入一個信息結(jié)束標(biāo)志(EOM)，以后的放音操作當(dāng)遇到結(jié)束標(biāo)志(EOM)就會停止，芯片進(jìn)入節(jié)電狀態(tài)。錄音 (REC)：REC高電平有效，不管芯片處在節(jié)電狀態(tài)還是正在放音的狀態(tài)只要REC變?yōu)楦唠娖?，芯片就開始錄音。地線(Vssa，Vssd)：Vssa是芯片內(nèi)部的模擬電路的地線匯接引腳。電源線的匯合這樣接法會使得噪聲的影響減少到最小。語音芯片ISD1820PY管腳功能為：電源(VCC)：芯片內(nèi)部的有兩路電路分別是：模擬電路和數(shù)字電