说明：  基于PID算法的温度控制系统 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。
(Temperature control system based on PID algorithm 89C51 microcontroller, through keyboard input default value compared with the the DS18B20 measured actual value, and then drives the cooling or heating circuits. Keil C language to implement the PID control.)