SET——》用于选择设置时间、下限温度、上限温度；最大时间99分钟，由于加热片等因素限制最高温只能到60度。
+、- -——》用于调结大小；
START——》开始键；

当温度小于下限温度时，加热器进行加热；
当温度大于下线温度小于上限温度时，加热器停止加热；
当温度大于上限温度时，散热风扇进行工作。
原理图如下：

源程序：
#include<reg51.h>
#define uchar unsigned char
#define uint unsigned int
sbit rs=P1^5;
sbit rw=P1^6;
sbit en=P1^7;
//sbit rs=P2^6;
//sbit rw=P2^5;
//sbit en=P2^7;
sbit DQ=P2^0; //18b20
//sbit DQ=P1^7;
sbit jdq=P1^1; //继电器
sbit fj=P1^0;
sbit fmq=P2^5; //蜂鸣器
// sbit fmq=P1^5;
sbit key1=P3^0;//设置
sbit key2=P3^1;//加
sbit key3=P3^2;//减
sbit key4=P3^3;//开始
uchar b,c,t,t1,t2,d1,d2,start;
void init();
void delay1(uint i);
void delay5us();
void delay(uint z);
void Init_DS18B20(void);
uchar ReadOneChar(void);
void WriteOneChar(uchar dat);
uint ReadTemperature(void);
void write_1602byte(uchar date);
void write_1602order(uchar date);
void display();
void keysan();
void comper();
void fengminqi();
void main()
{
init();
while(1)
{
keysan();
comper();
display();
}
}
void init()//初始化程序
{
TMOD = 0x01; //定时器初始化
TH0 = 0x4c;
TL0 = 0x00;
EA = 1;
ET0 = 1;
TR0 = 0;
en=0;//初始化1602液晶
rs=0;
rw=1;
start=0;
fmq=0;
jdq=0;
fj=0;
d1=5;
d2=15 ;
delay(5);
write_1602order(0x38);
write_1602order(0x0c);
write_1602order(0x06);
write_1602order(0x10);
}
void delay1(uint i)//延时函数
{
while(i--);
}
void delay5us() //延时5us
{;;}
void delay(uint z) //延时ms
{
uint x,y;
for(x=z;x>0;x--)
for(y=123;y>0;y--);
}
void Init_DS18B20(void)//18b20初始化
{
uchar x=0;
DQ = 1; //DQ复位
delay1(8); //稍做延时
DQ = 0; //单片机将DQ拉低
delay1(80); //精确延时 大于 480us
DQ = 1; //拉高总线
delay1(10);
x=DQ; //稍做延时后 如果x=0则初始化成功 x=1则初始化失败
delay1(5);
}
uchar ReadOneChar(void) //18b20读一个字节
{
uchar i=0;
uchar dat = 0;
for (i=8;i>0;i--)
{
DQ = 0; // 给脉冲信号
dat>>=1;
DQ = 1; // 给脉冲信号
if(DQ)
dat|=0x80;
delay1(5);
}
return(dat);
}
void WriteOneChar(uchar dat)//18b20写一个字节
{
unsigned char i=0;
for (i=8; i>0; i--)
{
DQ = 0;
DQ = dat&0x01;
delay1(5);
DQ = 1;
dat>>=1;
}
delay1(5);
}
uint ReadTemperature(void) //18b20读温度
{
uchar a=0;
uint b=0;
uint t=0;
Init_DS18B20();
WriteOneChar(0xCC); // 跳过读序号列号的操作
WriteOneChar(0x44); // 启动温度转换
delay1(200);
Init_DS18B20();
WriteOneChar(0xCC); //跳过读序号列号的操作
WriteOneChar(0xBE); //读取温度寄存器等（共可读9个寄存器） 前两个就是温度
a=ReadOneChar(); //低位
b=ReadOneChar(); //高位
b<<=8;
t=a+b;
return(t);
}

void write_1602byte(uchar date) //1602写数据
{
rs=1;
rw=0;
delay5us();
P0=date;
delay5us();
en=1;
delay5us();
en=0;
delay5us();
rw=1;
rs=0;
delay5us();
delay5us();
delay5us();
delay5us();
}
void write_1602order(uchar date)//1602写指令
{
rs=0;
rw=0;
delay5us();
P0=date;
delay5us();
en=1;
delay5us();
en=0;
delay5us();
rw=1;
rs=1;
delay5us();
delay5us();
delay5us();
delay5us();
}
void display() //显示函数
{
t=(ReadTemperature()>>4)&0x00ff;
write_1602order(0X80);
write_1602byte(*S*);
write_1602byte(*J*);
write_1602byte(0X30+c/10);
write_1602byte(0X30+c%10);
write_1602byte(*:*);
write_1602byte(0X30+b/10);
write_1602byte(0X30+b%10);
write_1602order(0X80+9);
write_1602byte(*W*);
write_1602byte(*D*);
write_1602byte(0X30+t/100);
write_1602byte(0X30+t%100/10);
write_1602byte(0X30+t%10);
write_1602byte(0xdf);
write_1602byte(*c*);
write_1602order(0X80+0x40);
write_1602byte(*X*);
write_1602byte(*X*);
write_1602byte(0X30+t1/100);
write_1602byte(0X30+t1%100/10);
write_1602byte(0X30+t1%10);
write_1602byte(0xdf);
write_1602byte(*c*);
write_1602order(0X80+0x40+9);
write_1602byte(*S*);
write_1602byte(*X*);
write_1602byte(0X30+t2/100);
write_1602byte(0X30+t2%100/10);
write_1602byte(0X30+t2%10);
write_1602byte(0xdf);
write_1602byte(*c*);
}
/************************比较电路程序******************************
****当实际温度大于上限温度时，停止加热，同时散热风扇开始工作*******
*******当实际温度小于下限温度时，开始加热，散热风扇未工作**********
******当实际温度在上限、下限温度之间时加热器与风扇都未工作*********
*****当工作时间为零时，定时器停止工作，蜂鸣器开始报警**************/
void comper()
{
if(start==1)
{
write_1602order(0X80+7);
write_1602byte(0x7F);
write_1602byte(0x7e);
write_1602order(0X80+0x40+7);
write_1602byte(0x7F);
write_1602byte(0x7e);
if((t>=t1)&&(t<=t2))
{
jdq=0;
fj=0;
}
if(t<t1)
{
jdq=1;
fj=0;
}
if(t>t2)
{
jdq=0;
fj=1;
}
if((b==0)&&(c==0))
{
TR0=0;
fengminqi();
start=0;
}
}
else
{
jdq=0;
fj=0;
TR0=0;
write_1602order(0X80+7);
write_1602byte(0x7e);
write_1602byte(0x7f);
write_1602order(0X80+0x40+7);
write_1602byte(0x7e);
write_1602byte(0x7f);
}
}
void keysan()
{
uchar i,tp1,tp2,tp3;
if(key1==0)
{
delay(d1);
if(key1==0)
{
i++;
if(i==9)
i=0;
}
while(!key1);
delay(d2);
while(!key1);
}
/*************************时间设置，最大时间99分钟***********************************/
while(i==1)//十分位
{
tp2=c/10;
tp1=c%10;
write_1602order(0X80+2);
write_1602order(0X0f);//光标闪烁
if(key2==0)
{
delay(d1);
if(key2==0)
{
tp2++;
if(tp2>9)
tp2=0;
}
while(!key2);
delay(d2);
while(!key2);
}
if(key3==0)
{
delay(d1);
if(key3==0)
{
tp2--;
if(tp2>9)
tp2=9;
}
while(!key3);
delay(d2);
while(!key3);
}
c=tp2*10+tp1;
display();
if(key1==0)
{
delay(d1);
if(key1==0)
{
i++;
if(i==9)
i=0;
}
while(!key1);
delay(d2);
while(!key1);
}
}
while(i==2)//分位
{
tp2=c/10;
tp1=c%10;
write_1602order(0X80+3);
if(key2==0)
{
delay(d1);
if(key2==0)
{
tp1++;
if(tp1>9)
tp1=0;
}
while(!key2);
delay(d2);
while(!key2);
}
if(key3==0)
{
delay(d1);
if(key3==0)
{
tp1--;
if(tp1>9)
tp1=9;
}
while(!key3);
delay(d2);
while(!key3);
}
c=tp2*10+tp1;
display();
if(key1==0)
{
delay(d1);
if(key1==0)
{
i++;
if(i==9)
i=0;
}
while(!key1);
delay(d2);
while(!key1);
}
}
/*************************下限温度设置，最大温度150度***********************************/
while(i==3)//百分位
{
tp3=t1/100;
tp2=t1%100/10;
tp1=t1%10;
write_1602order(0X80+0x40+2);
write_1602order(0X0f);//光标闪烁
if(key2==0)
{
delay(d1);
if(key2==0)
{
tp3++;
if(tp3>1)
tp3=0;
}
while(!key2);
delay(d2);
while(!key2);
}
if(key3==0)
{
delay(d1);
if(key3==0)
{
tp3--;
if(tp3>1)
tp3=1;
}
while(!key3);
delay(d2);
while(!key3);
}
t1=tp3*100+tp2*10+tp1;
display();
if(key1==0)
{
delay(d1);
if(key1==0)
{
i++;
if(i==9)
i=0;
}
while(!key1);
delay(d2);
while(!key1);
}
}
while(i==4)//十分位
{
write_1602order(0X80+0x40+3);
if(key2==0)
{
delay(d1);
if(key2==0)
{
tp2++;
if(tp2>=10)
tp2=0;
}
while(!key2);
delay(d2);
while(!key2);
}
if(key3==0)
{
delay(d1);
if(key3==0)
{
tp2--;
if(tp2>9)
tp2=9;
}
while(!key3);
delay(d2);
while(!key3);
}
t1=tp3*100+tp2*10+tp1;
display();
if(key1==0)
{
delay(d1);
if(key1==0)
{
i++;
if(i==9)
i=0;
}
while(!key1);
delay(d2);
while(!key1);
}
}
while(i==5)
{
write_1602order(0X80+0x40+4);
if(key2==0)
{
delay(d1);
if(key2==0)
{
tp1++;
if(tp1>=10)
tp1=0;
}
while(!key2);
delay(d2);
while(!key2);
}
if(key3==0)
{
delay(d1);
if(key3==0)
{
tp1--;
if(tp1>9)
tp1=9;
}
while(!key3);
delay(d2);
while(!key3);
}
t1=tp3*100+tp2*10+tp1;
display();
if(key1==0)
{
delay(d1);
if(key1==0)
{
i++;
if(i==9)
i=0;
}
while(!key1);
delay(d2);
while(!key1);
}
}
/*************************上限温度设置，最大温度199度，实际温度不会超过120***********************************/
while(i==6)//白分位
{
tp3=t2/100;
tp2=t2%100/10;
tp1=t2%10;
write_1602order(0X80+0x40+11);
if(key2==0)
{
delay(d1);
if(key2==0)
{
tp3++;
if(tp3>1)
tp3=0;
}
while(!key2);
delay(d2);
while(!key2);
}
if(key3==0)
{
delay(d1);
if(key3==0)
{
tp3--;
if(tp3>1)
tp3=1;
}
while(!key3);
delay(d2);
while(!key3);
}
t2=tp3*100+tp2*10+tp1;
display();
if(key1==0)
{
delay(d1);
if(key1==0)
{
i++;
if(i==9)
i=0;
}
while(!key1);
delay(d2);
while(!key1);
}
}
while(i==7)//十分位
{
write_1602order(0X80+0x40+12);
if(key2==0)
{
delay(d1);
if(key2==0)
{
tp2++;
if(tp2>=10)
tp2=0;
}
while(!key2);
delay(d2);
while(!key2);
}
if(key3==0)
{
delay(d1);
if(key3==0)
{
tp2--;
if(tp2>9)
tp2=9;
}
while(!key3);
delay(d2);
while(!key3);
}
t2=tp3*100+tp2*10+tp1;
display();
if(key1==0)
{
delay(d1);
if(key1==0)
{
i++;
if(i==9)
i=0;
}
while(!key1);
delay(d2);
while(!key1);
}
}
while(i==8)//分位
{
write_1602order(0X80+0x40+13);
if(key2==0)
{
delay(d1);
if(key2==0)
{
tp1++;
if(tp1>=10)
tp1=0;
}
while(!key2);
delay(d2);
while(!key2);
}
if(key3==0)
{
delay(d1);
if(key3==0)
{
tp1--;
if(tp1>9)
tp1=9;
}
while(!key3);
delay(d2);
while(!key3);
}
t2=tp3*100+tp2*10+tp1;
display();
if(key1==0)
{
delay(d1);
if(key1==0)
{
i++;
if(i==9)
{
i=0;
write_1602order(0x0c);
}
}
while(!key1);
delay(d2);
while(!key1);
}
}
/**********************************按下key4开始启动*********************************/
if(key4==0)
{
delay(d1);
if(key4==0)
{
start++;
if(start>=2)
start=0;
TR0=~TR0;
}
while(!key4);
delay(d2);
while(!key4);
}
}
void fengminqi()//蜂鸣器报警程序时间为5秒钟
{
uchar i=20;
while(i!=0)
{
fmq=~fmq;
delay(500);
i--;
}
}
void time0()interrupt 1
{
uchar a;
TH0 = 0x4c;
TL0 = 0x00;
a++;
if(a==20)
{
a=0;
b--;
if(b>59)
{
b=59;
c--;
if(c>90)
c=0;
}
}
}