毕业设计(论文)附录.doc

北京信息科技大学 毕业设计（论文）附录 题目：基于单片机的数字钟的设计 学院：自动化学院 专业：自动化 学生姓名：崔智明 班级/学号：06331/16 指导老师/督导老师：唐胜春/ 起止时间：2010年 3月 21日至2010年 6月 25日 目录 附件1：基于单片机的英语论文及翻译…………………………………共 9页 附件2：软件程序…………………………………………………………共 18页 基于单片机的英语论文及翻译 Programmable controllers From a simple heritage, these remarkable systems have evolved to not only replace electromechanical devices, but to solve an ever-increasing array of control problems in both process and nonprocess industries. By all indications, these microprocessor powered giants will continue to break new ground in the automated factory into the 1990s. HISTORY In the 1960s, electromechanical devices were the order of the day ass far as control was concerned. These devices, commonly known as relays, were being used by the thousands to control many sequential-type manufacturing processes and stand-along machines. Many of these relays were in use in the transportation industry, more specifically, the automotive industry. These relays used hundreds of wires and their interconnections to effect a control solution. The performance of a relay was basically reliable - at least as a single device. But the common applications for relay panels called for 300 to 500 or more relays, and the reliability and maintenance issues associated with supporting these panels became a very great challenge. Cost became another issue, for in spite of the low cost of the relay itself, the installed cost of the panel could be quite high. The total cost including purchased parts, wiring, and installation labor, could range from $30~$50 per relay. To make matters worse, the constantly changing needs of a process called for recurring modifications of a control panel. With relays, this was a costly prospect, as it was accomplished by a major rewiring effort on the panel. In addition these changes were sometimes poorly documented, causing a second-shift maintenance nightmare months later. In light of this, it was not uncommon to discard an entire control panel in favor of