89C51单片机，通过键盘输入预设值，与DS18B20测得的实际值做比较，然后驱动制冷或加热电路。用keil C语言来实现PID的控制。 ,89C51 microcontroller, through keyboard input default, and DS18B20 measured to compare the actual value, and then drive circuit refrigeration or heating. Keil C language used to a