发布时间 : 星期四 文章篮球三十秒计时器更新完毕开始阅读10efd06925c52cc58bd6be96
目 录
前 言······························································································································ 2 第一章 篮球三十秒计时器设计要求及方案比较······················································ 3
1.1 设计要求········································································································· 3 1.2 方案比较········································································································· 3 第二章 系统组成及工作原理······················································································ 5
2.1 系统组成········································································································· 5 2.2 工作原理········································································································· 5 第三章 单元电路设计、参数计算、器件选择·························································· 7
3.1 控制电路········································································································· 7
3.1.1 暂停/连续控制电路············································································ 7 3.1.2 置数/启动控制电路············································································ 7 3.1.3 清零/灭灯电路···················································································· 8 3.2 秒脉冲发生电路····························································································· 8 3.3 计时电路······································································································· 10
3.3.1 计数器································································································ 10 3.3.2 计时电路的组成················································································ 12 3.4 译码显示电路······························································································· 12
3.4.1 七段发光二极管（LED）数码管······················································ 12 3.4.2 CD4511································································································ 13 3.5 报警电路······································································································· 14 第四章 调试及测试结果分析···················································································· 16
4.1 调试··············································································································· 16 4.2 结果分析······································································································· 17 结论······························································································································ 18 致谢······························································································································ 19 参考文献······················································································································ 20 附录一 原理图············································································································ 21 附录二 元件清单········································································································ 22
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前 言
人类最早使用的定时工具是沙漏或水漏，但在钟表诞生发展成熟之后，人们开始尝试使用这种全新的计时工具来改进定时器，达到准确控制时间的目的。 而典型的应用就是篮球竞赛计时。在篮球比赛中，规定了球员的持球时间不能超过30秒，否则就犯规了。本课程设计的“篮球竞赛30秒计时器”，可用于篮球比赛中，用于对球员持球时间30秒限制。一旦球员的持球时间超过了30秒，它自动的报警从而判定此球员的犯规。
本设计主要能完成：显示30秒倒计时功能；系统设置外部操作开关，控制计时器的直接清零、启动和暂停/连续功能；在直接清零时，数码管显示器灭灯；计时器为30秒递减计时其计时间隔为1秒；计时器递减计时到零时，数码显示器不灭灯，同时发出光电报警信号等。
篮球三十秒计时器和篮球二十四秒计时器如出一辙，不同之处在于置数部分。方案中应用双时钟加、减同步可逆计数器74LS192来实现倒计时功能,在功能选择过程中选择减计数功能,芯片管脚选择中让DOWN处于工作状态。在显示零秒亮灯报警电路中，应用组合电路及二极管发光条件来实现该功能。显示电路用CD451和共阴数码管来实现，通过控制CD4511的灭灯输入信号（BL’）来实现灭灯的功能。
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第一章 篮球三十秒计时器设计要求及方案比较
1.1 设计要求
[课题名称]:篮球三十秒计时器
[基本要求]:1)具有显示三十秒计时功能;
2)设置外部操作开关,控制计数器的直接清零,启动和暂停/连续功能; 3)在直接清零时,要求数码显示器灭灯; 4)计时器为三十秒递减时,计时间隔为一秒;
5)计时器递减计时到零时,数码显示不能灭灯,同时发出光电报警信号。
[主要参考元器件]：NE555﹑74LS161﹑74LS192
1.2 方案比较
本课程设计中，我和我的同组人提出了两个脉冲信号发生电路的方案，方案如下： 方案一是用555定时器构成一个多谐振荡器，为电路提供芯片工作的脉冲信号。其电路图如下： 方案一
图1.2.1 555构成的秒脉冲发生器
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方案二是电路由14位二进制串行计数器/分频器和振荡器CD4060、BCD同步加法计数器CD4518构成的秒信号发生器。 方案二
图1.2.2 基准秒信号发生电路
电路中利用CD4060组成两部分电路。一部分是14级分频器，其最高分频数为16384；另一部分是由外接电子表用石英晶体、电阻及电容构成振荡频率为32768Hz的振荡器。震荡器输出经14级分频后在输出端Q14上得到1/2秒脉冲并送入由1/2 CD4518构成的二分频器，分频后在输出断Q1上得到秒基准脉冲。 方案选择:
本课程设计中对秒脉冲信号的精度要求并不是很高，并且方案二中用CD4060和分频器构成的基准秒脉冲发生电路较于前者要复杂的多，而且CD4060和CD4518我们平常很少用，对其功能和引脚信息了解不多，所以，我们选用了方案一，用555定时器构成电路中的脉冲信号发生器。
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