【正文】 I 摘 要 現(xiàn)代社會(huì)的發(fā)展對(duì)稱重技術(shù)提出了更高的要求。目前，臺(tái)式電了秤在商業(yè)貿(mào)易中的使用已相當(dāng)普遍，但存在較大的局限性：體積大、成本高、需要工頻交流電源供應(yīng)、攜帶不便、應(yīng)用場(chǎng)所受到制約。但是在工業(yè)測(cè)量中還沒有讓人們期待的電子秤出現(xiàn)。多年來(lái)，人們一直期待測(cè)量準(zhǔn)確、價(jià)格低廉的在工業(yè)發(fā)展中起到巨大作用的電子秤投放市場(chǎng)。 本課程設(shè)計(jì)的電子秤以 AT89S52 單片機(jī) 為控制核心 ，利用全橋測(cè)量原理，通過(guò)對(duì)電路輸出電壓和標(biāo)準(zhǔn)重量的線性關(guān)系，建立具體的數(shù)學(xué)模型，將電壓量綱（ V）改為重量綱（ g）即成為一臺(tái)原始電子秤。其中測(cè)量電 路中最主要的元器件就是電阻應(yīng)變式傳感器。電阻應(yīng)變式傳感器是 稱重 傳感器中應(yīng)用最多的一種，本設(shè)計(jì)采用全橋測(cè)量電路，使系統(tǒng)產(chǎn)生的誤差更小，輸出的數(shù)據(jù)更精確。而放大器電路采用 AD620，其作用就是把傳感器輸出的微弱的模擬信號(hào)進(jìn)行一定倍數(shù)的放大，以滿足 A/D轉(zhuǎn)換器對(duì)輸入信號(hào)電平的要求。 MAX187 A/D轉(zhuǎn)換的作用是把模擬信號(hào)轉(zhuǎn)變成數(shù)字信號(hào)，進(jìn)行模數(shù)轉(zhuǎn)換，然后把數(shù)字信號(hào)輸送到顯示電路中去，最后由顯示電路顯示出測(cè)量結(jié)果。 電子秤主要由電源、稱重傳感器、單片機(jī)、鍵盤 /開關(guān)、 12864液晶顯示器等部分構(gòu)成。主要技術(shù) 指標(biāo)為：稱量范圍 — 5kg；分度值 ；精度等級(jí) m級(jí)；電源 5v。儀器的技術(shù)指標(biāo)參考了目前國(guó)內(nèi)市場(chǎng)上使用最多、國(guó)內(nèi)外產(chǎn)量最大的電子衡器的技術(shù)指標(biāo)，其合理性無(wú)疑加大了產(chǎn)品投放市場(chǎng)后的競(jìng)爭(zhēng)能力。儀器主要功能有去皮、計(jì)價(jià)、累計(jì)、單價(jià)設(shè)定、過(guò)載報(bào)警、時(shí)間顯示等。 關(guān)鍵詞： 單片機(jī) 稱重傳感器 放大器 模數(shù)轉(zhuǎn)換 II The design of multifunctional electronic scale Abstract The development of the modern society has put forward higher request on weighing technology. The desktop electronic scales have been great application in mercial trade, but they have many shortings such as large volume, high cost, AC supply power and not cove nince to carry, so they are restricted to use. The usual portable scales are lever scales which are mostly used by residents, and spring balance which measure through pression or drawing of spring. They are being rejected for their big measuring errors. People have been expecting cheap portable electronic scales which can measure accurately and be carried conveniently for many years. The curriculum design of electronic scales in order to AT89S52 microcontroller to control the core, the use of fullbridge measuring principle, through the circuit output voltage and the standard weight of a linear relationship, the establishment of a specific mathematical model, the dimensionless voltage (V) changed the weight of Class ( g) bee a single original electronic scales. Measuring circuit in which the most significant ponent is the resistance strain sensor. Resistance strain gauge sensor is a sensor in the most widely used, this design uses a fullbridge measurement circuit, so that system to produce a smaller error, the output of the data more accurate. The amplifier circuit using AD620, whose role is to weak analog sensor output signals a certain multiple of the amplification in order to meet the A / D converter input signal level requirements. MAX187 A / D conversion is the role of the analog signals into digital signals, analogdigital conversion, digital signal and then transmitted to the display circuit and there, finally shown by the display circuit measurement results. Electronic Scale is a major by the power, weighing sensor, microcontroller, keyboard / switch 12864 LCD monitors and other parts. Its technical indictors include10kg maximal measuring range,10g division value, III precision, 5V work voltage. Its technical indictors refer to the indictors of the electri conic measuring tools of most popularity in the markets and of large output at home and board, so the instrument is strengthened the petitive power after putting on markets. Instrument III main functions are peeled, pricing, total, unit price setting, overload alarm, time display, etc. Key Words： SCM Weighing Sensor Amplifiers Analogdigital conversion IV 目 錄 第一章 前 言 ......................................................... 1 課題研究意義 ................................................. 1 國(guó)內(nèi)外研究情況 ............................................... 1 本設(shè)計(jì)的任務(wù)和主要內(nèi)容 ....................................... 2 第二章 方案論證 ...................................................... 3 單片機(jī)選擇 .................................................... 3 顯示部分 ..................................................... 3 數(shù)字時(shí)鐘 ..................................................... 4 放大部分 ...................................................... 4 A/D 轉(zhuǎn)換器選擇 ............................................... 5 壓力傳感器部分 ................................................ 5 第三章 總體方案 ...................................................... 7 工作原理 ..................................................... 7 系統(tǒng)各模塊的最終方案 .......................................... 7 第四章 硬件電路的設(shè)計(jì) ............................................... 8 單片機(jī)控制電路的設(shè)計(jì) .......................................... 8 Hl8傳感器的電路設(shè)計(jì) ......................................... 9 信號(hào)放大電路的設(shè)計(jì) .......................................... 13 信號(hào) A/D 轉(zhuǎn)換器 .............................................. 16 DS1302 時(shí)鐘電路的設(shè)計(jì) ........................................ 17 鍵盤和過(guò)量程報(bào)警電路設(shè)計(jì) ..................................... 18 12864 液晶顯示電路的設(shè)計(jì) ..................................... 19 電源電路設(shè)計(jì) ................................................ 21 總體工作電路原理圖 .......................................... 21 第五章 軟件的設(shè)計(jì) ................................................... 25 軟件所實(shí)現(xiàn)的功能 ............................................ 25 軟件主流程 .................................................. 25 數(shù)據(jù)采集子程序的設(shè)計(jì) ........................................ 27 顯示子程序的設(shè)計(jì) ............................................ 27 報(bào)警子程序的設(shè)計(jì) ............................................ 28 V 軟件抗干擾設(shè)計(jì) .............................................. 29 第六章 調(diào)試與分析 ................................................... 30 調(diào)試系統(tǒng)簡(jiǎn)介 ................................................ 30 調(diào)試故障及原因分析 .......................................... 31 第七章 結(jié)論 ......................................................... 31 參考文獻(xiàn) ............................................................ 32 附錄 ................................................................ 33 致謝 ................................................. 錯(cuò)誤 !未定義書簽。 1 第一章 前 言 課題研究意義 隨著經(jīng)濟(jì)的發(fā)展，出售商品品種的增加，需要稱量物品的設(shè)備也需要更新?lián)Q代。多功能電子秤就是現(xiàn)代生活中應(yīng)運(yùn)而生的一種精確、智能、 方便、明了、可靠的稱量?jī)x器。它克服了傳統(tǒng)的桿秤、盤秤不精確、速度慢、不能計(jì)價(jià)、易作弊等缺點(diǎn)，在商業(yè)領(lǐng)域應(yīng)用越來(lái)越多。 目前，臺(tái)式電子秤在商業(yè)貿(mào)易中的使用已相當(dāng)普遍，但存在較大的局限性：體積