自动电风扇控制.doc

of accountability, redress of orders and prohibitions. Strengthening the honesty and self-discipline of leading cadres h采用PWM脉宽调制方式来改变直流风扇电机的转速。并通过两个按键改变预设温度值，一个提高预设温度，另一个降低预设温度值。系统结构框图如下：
of accountability, redress of orders and prohibitions. Strengthening the honesty and self-discipline of leading cadres honesty in politics and education work, enhance leaders ability to resist
实用文档
of accountability, redress of orders and prohibitions. Strengthening the honesty and self-discipline of leading cadres honesty in politics and education work, enhance leaders ability to resist
AT89C52
复位
电源
温度显示
晶振
DS18B20
独立键盘
直流电机
PWM驱动
（系统构成框图）
本系统要实现风扇直流电机的温度控制，使风扇电机能根据环境温度的变化自动启停及改变转速，需要比较高的温度变化分辨率以及稳定可靠的换挡停机控制部件。
3、系统方案设计


（系统复位与晶振电路）
在单片机应用系统中，除单片机本身需要复位以外，外部扩展I/O接口电路也需要复位，因此需要一个包括上电和按钮复位在内的系统同步复位电路。单片机上的XTAL1和XTAL2用来外接石英晶体和微调电容，即用来连接单片机片内OSC的定时反馈回路。本设计中开关复位与晶振电路如下图所示，当按下按键开关S
of accountability, redress of orders and prohibitions. Strengthening the honesty and self-discipline of leading cadres honesty in politics and education work, enhance leaders ability to resist
实用文档
of accountability, redress of orders and prohibitions. Strengthening the honesty and self-discipline of leading cadres honesty in politics and education work, enhance leaders ability to resist
1时，系统复位一次。其中电容C1、C2为20pF，C3为10uF，电阻R2、R3为10k，。

（数码管显示电路）
本系统选用5位共阴极数码管作为显示模块，其中前3位数码管用于显示温度传感器实时检测采集到的温度，，显示范围为0-；后2位数码管用于显示系统设置的初值温度，只能显示整数的温度值，显示范围为0-99度。5位数码管的段选a、b、c、d、e、f、g、-，其中P0口需接一10K的上拉电阻，以使单片机的P0口能够输出高低电平。5位数码管的位选W1--，-，则选中与该位相连的数码管。
of accountability, redress of orders and prohibitions. Strengthening the honesty and self-discipline of leading cadres honesty in politics and education work, enhance leaders ability to resist
实用文档
of accountability, redress of orders and prohibitions. Strengthening the honesty and self-discipline of leading ca