摘 要
本文用單片機設(shè)計了一個數(shù)字電子秤，并給出了設(shè)計框圖、硬件組成及軟件系統(tǒng)。本系統(tǒng)以51單片機最小系統(tǒng)為核心，主要的部件有24位專用串行A/D轉(zhuǎn)換芯片HX711、懸臂梁式電阻應(yīng)變傳感器，輸出采用4位數(shù)碼管顯示。系統(tǒng)通過傳感器將壓力轉(zhuǎn)化為微弱電信號，即電阻應(yīng)變片感應(yīng)到壓力后，電阻發(fā)生微小變化。通過全橋測量電路將電阻的微小變化轉(zhuǎn)化成電壓的微小變化，再經(jīng)過24位專用串行A/D轉(zhuǎn)換芯片HX711將微小的電壓信號轉(zhuǎn)換為24位的串行數(shù)字信號輸入到單片機進行處理，最后輸出到數(shù)碼管上顯示。本設(shè)計采用的24位專用串行A/D轉(zhuǎn)換芯片HX711，具有分辨率高，占用I/O口少，與外設(shè)接口簡單等優(yōu)點。

關(guān) 鍵 詞：數(shù)字電子秤；應(yīng)變片式電阻傳感器；HX711；單片機

ABSTRACT
It designed a digital electronic scale by using the single chip computer, which included the frame drawing, hardware structure and software system. It based on 51 microcomputer system and included other models, such as dedicated A/D converter chip HX711 and cantilever-type resistance strain sensor. The output was displayed by four-bit digital tube. This paper conveted the pressure into weak signal. That is when the pressure was induced by the resistance strain gauge sensor, small changes in resistance occurred . It would be converted to voltage with full-bridge measurement circuit. Then the 24 special serial A/D converting chip HX711 converted the small changes in voltage into 24-bit serial digital signals, SCM processed the signals, lastly the digital tube displayed the output. HX711 is special for A/D converter, moreover it has high resolution and occupys less I/O ports. Importantly its interfacing with peripheral circuits is simple.

KEY WORDS: Digital electronic scale; Resistance strain gauge sensor; HX711; Single chip computer



目 錄
1 緒論 1
2 系統(tǒng)組成及工作原理 3
2.1 系統(tǒng)的組成 3
2.2 系統(tǒng)的工作原理 3
3 系統(tǒng)硬件設(shè)計 5
3.1 主控芯片STC89C52單片機基本系統(tǒng) 5
3.1.1 STC89C52單片機性能介紹 5
3.1.2 STC89C52單片機引腳功能 5
3.1.3 復(fù)位電路 6
3.1.4 晶振電路 7
3.2 A/D轉(zhuǎn)換芯片HX711接口電路的設(shè)計 7
3.2.1 HX711引腳功能 8
3.2.2 HX711管腳說明 8
3.3 壓電傳感器的設(shè)計 12
3.3.1 應(yīng)變片式電阻傳感器 12
3.3.2 應(yīng)變片式電阻傳感器的結(jié)構(gòu)和原理 12
3.3.3 全橋測量電路 13
3.4 LED顯示電路的設(shè)計 14
4 系統(tǒng)軟件設(shè)計 17
4.1 系統(tǒng)主函數(shù) 17
4.2 A/D數(shù)據(jù)采集子函數(shù) 17
4.3 數(shù)碼管顯示子函數(shù) 18
5 系統(tǒng)測試及定標(biāo) 19
5.1 系統(tǒng)硬件測試 19
5.2 線性度的確定 19
5.2.1 未定標(biāo)時數(shù)碼管顯示值 19
5.2.2 定標(biāo)后數(shù)碼管顯示值 19
5.2.3 誤差分析 19
6 總結(jié) 23
致 謝 25
參考文獻 27
附 錄1系統(tǒng)原理圖 29
附 錄2 PCB圖 30
附 錄3系統(tǒng)程序清單 31
附 錄4 MATLAB繪圖程序清單 33
附 錄5 實物圖 34