说明：  本次课程设计是设计一个具有长时间定时（1小时以上）的电路。该电路的核心部分有2部分 ，一是可调占空比的方波发生器电路；另一个是时间控制电路。这两部分应用的主要元件都是555定时器，可调占空比的方波发生器电路是应用555定时器连接的多谐振荡器，时间控制电路是应用555定时器连接的单稳态触发器。该长时间定时器设计思路清晰，电路连接简单，性价比高，有很大的实用价值。
(The curriculum design is to design a long period of time from time to time (1 hour or more) circuit. The circuit is the core of the 2 parts, an adjustable duty cycle square wave generator circuit the other is the time control circuit. Application of these two parts of the main components are 555 timer, an adjustable duty cycle square wave generator is the application of 555 timer circuit connected Multivibrator, time control circuit is connected to the application of 555 timer monostable trigger browser. The long timer clear design, circuit connectivity is simple, cost-effective, there are great practical value.)