实时采集当前环境温度值，并显示于数码管上。 同时，当温度高于某一值时（此处设为31摄氏度），蜂鸣器便会发出报警。 而当低于该值时，蜂鸣器自动停止报警。试验时，可用手触摸DS18B20，使其温度升高到31度，观察现象。-Real-time acquisition current environmental temperature, and display in the digital tube. At the same time, when the temperature is higher than a certain value (here set to 31 degrees Celsius), buzzer will then send out alarm. And when less than this value, buzzer automatic stop alarm. Test, usable hand touch DS18B20, make its temperature to 31 degrees, observed phenomena.