基于單片機的測速表設計

摘   要
隨著科技的迅速發(fā)展，單片機的應用也越來越廣泛，并帶動傳統(tǒng)控制檢測技術不斷更新?，F(xiàn)在的車速表大多是電子式的，用LED數(shù)碼管或LCD即時顯示，顯示更加直觀。電子式車速表采用接觸車速傳感器代替軟軸傳動,可使車速表的安裝位置不受距離限制，進一步有效地克服了機械式車速表中的諸多不足。
本次設計給出了以AT89C2051為核心，利用單片機的運算和控制功能，并采用系統(tǒng)化LED顯示模塊實時顯示所測速度的設計方案，以及串口數(shù)據(jù)存儲電路和系統(tǒng)軟件。
該方案由于使用了數(shù)碼管顯示模塊和E2PROM，以及高效快速算法，因而可在節(jié)約系統(tǒng)資源和簡化程序設計的基礎上保證測量精度和系統(tǒng)實時性。其中信號預處理電路包含信號放大、波形變換和波形整形：信號預處理電路中的放大器用于對待測信號進行放大,以降低對待測信號的幅度要求；波形變換和波形整形電路則用來將放大的信號轉換成可與單片機接口的TTL 信號。通過單片機的設置可使INT0 引腳能夠對內(nèi)部定時器T0 的工作進行控制,這樣能精確地測出加到INT0 引腳的正脈沖寬度(即測出脈沖信號的期) 。速度顯示部分采用數(shù)碼顯示, 所得的數(shù)據(jù)采用I2C總線, 并通過E2PROM來存儲, 因而節(jié)省了所需單片機的口線和外圍器件, 同時也簡化了顯示部分的軟件編程。
本方案實現(xiàn)了電動車速度即時顯示，并可通過控制兩個按鍵顯示速度或里程，同時加入了超速語音報警功能，使之更加人性化。

關鍵詞：單片機；霍爾傳感器；數(shù)碼顯示；語音報警；DC/DC變換器

Abstract
With the rapid development of technology, more and more widespread application of microcomputer, and promote the traditional control detection technology constantly updated. Most of the current electronic speedometer, and with the LED digital tube or LCD display real-time, display more intuitive. Electronic speedometer flexible shaft using the contact speed sensor instead of driving, speed tables can be installed without distance limitations, and further to effectively overcome the mechanical disadvantages of speed in the table.
The AT89C2051 is designed to give the core of computing and the use of microcomputer control, and adopting a systematic LED display module shows the measured real-time speed design, and the serial data storage circuits and system software.
The program due to the use of the digital display module and E2PROM, and efficient fast algorithm, thus saving resources and simplifying programming system based on the system to ensure accuracy and real-time. Signal pre-processing circuit which includes signal amplification, wave conversion and waveform shaping: signal pre-processing circuit in the amplifier for the amplified signal could be to reduce the requirements on signal amplitude; wave transformation and wave-shaping circuitry is used to enlarge the signal converted into TTL signals with the microcontroller interface. Set by MCU enables INT0 pin to the work of the internal timer T0 control, so to accurately measure the INT0 pin is added to the pulse width (ie measured pulse signal period). Speed display part of a digital display, the data collected using I2C bus, and through E2PROM to store, thus saving the need microcontroller port lines and peripheral devices, but also simplifies the display part of the software programming.
The program achieved the speed of real-time electric vehicle revealed two buttons can be displayed by controlling the speed or mileage, while adding a speed voice alarm function, make it more humane.

Key words: microcomputer； Hall sensor； digital display；voice alarm； DC / DC converter
 
目  錄
摘   要 I
Abstract II
1 引 言 1
1.1 選題背景 1
1.2 研究意義 1
1.3 研究內(nèi)容 2
2 總體設計方案 3
3 系統(tǒng)單元模塊概述 5
3.1 傳感器選擇 5
3.2 單片機選型 7
3.3 顯示模塊選型 8
3.4 報警電路選擇 9
3.5 速度算法概述 9
4 系統(tǒng)硬件設計 15
4.1單片機主控電路 15
4.1.1 單片機概述 15
4.1.2 復位電路 17
4.1.3 晶振電路 18
4.2 變換電路設計 19
4.3 傳感器電路設計 20
4.4 信號處理電路設計 23
4.5 存儲器電路設計 24
4.5.1 I2C總線概述 24
4.5.2 存儲器電路 25
4.6 報警電路設計 27
4.6.1 語音芯片概述 27
4.6.2 語音報警電路 28
4.7 顯示電路設計 31
4.8 掉電保護電路設計 33
4.9 數(shù)據(jù)處理過程 35
5 系統(tǒng)仿真與分析 37
5.1仿真結果 37
5.2仿真分析 38
6 系統(tǒng)軟件設計 39
6.1 系統(tǒng)軟件總流程圖 39
6.2 速度處理子程序 40
6.3 顯示子程序 41
7 總結與展望 43
致  謝 44
參考文獻 45
附錄A 程序清單 46
附錄B 電路圖 57