DS18B20 单线数字温度传感器，即一线设备，具有独特的优点：
( 1 )采用单总线接口法 与微处理器连接时 微处理器和 DS18B20 双向通信。 单总线具有经济性好、抗干扰能力强、现场温度测量适用于恶劣环境、使用方便等优点，使用户能够轻松构建传感器网络，引入测量系统构建的新概念。
( 2 )测量温度范围宽，测量精度高 DS18B20 测量范围为 -55 ℃ ~ 125 ℃ ； 在 -10~ 85°C 精度在范围内 ± 0.5°C 。
( 3 )持有多点组网功能 多个 DS18B20 可并联在唯一的单线上，实现多点测温。
( 4)供电方式灵活 DS18B20 数据线上可以通过内部寄生电路获取电源。因此，当数据线上的时间顺序满足一定的要求时，可以不连接外部电源 使系统结构更简单，可靠性更高。
( 5 )可配置测量参数 DS18B20 通过程序设置测量分辨率 9~12 位。
DS18B20 包装方体积小、适用电压宽、经济、可选包装方小，电压适用范围更广，适合建立自己经济的温度测量系统，受到设计师的青睐。
产品封装
时序图
典型应用电路
寄生供电方式
支持命令集
复位时序
读写时序
具体操作：
1、打开IDE，项目-加载库-管理库，搜索下载并安装相应的库，否则编程时会报错；
搜索 18B20 ，看到18B点击20相关库 安装好，
打开 找到第一个例子Alarm；
看到除了DallasTemperature.h，还需要另一个库OneWire.h，按照之前的步骤，搜索 OneWire 安装即可；ONE_WIRE_BUS 2 意思是 数据口连接开发版引脚pin 2；
2、Arduino 开发版用USB连接电脑，选择相应的开发版和端口，编译上传烧录，
接线时，必须加电阻，不加电阻检测不到设备；
管脚定义:面朝印字面，左边GND，右为VCC，中间是数字输出引脚(必须连接到4).7K—10K本例4.7K电阻；
BOM表
Arduino Uno *1
18B20温度传感器 *1
4.7K电阻*1
接线
Arduino Uno 18B20温度传感器 颜色
Pin 2 DO 白色
5V VCC 红色
GND GND 黄色
Arduino接线图
4.连接线后再使用USB连接电脑，打开串口监视器查看结果；
Alarm可根据需要修改案例代码：
#include ///引用单总线头文件
#include //引用18b20驱动文件
// Data wire is plugged into port 2 on the Arduino
#define ONE_WIRE_BUS 2//定义2脚为数据脚
// Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);
// Pass our oneWire reference to Dallas Temperature.
DallasTemperature sensors(&oneWire);
// arrays to hold device addresses
DeviceAddress insideThermometer, outsideThermometer;
void setup(void)
{
// start serial port
Serial.begin(9600);
Serial.println("Dallas Temperature IC Control Library Demo");
// Start up the library
sensors.begin()
// locate devices on the bus
Serial.print("Found ");
Serial.print(sensors.getDeviceCount(), DEC);//DEC意思是串口数据以10进制的格式输出
Serial.println(" devices.");
// search for devices on the bus and assign based on an index.
if (!sensors.getAddress(insideThermometer, 0))
Serial.println("Unable to find address for Device 0");
if (!sensors.getAddress(outsideThermometer, 1))
Serial.println("Unable to find address for Device 1");
// show the addresses we found on the bus
Serial.print("Device 0 Address: ");
printAddress(insideThermometer);
Serial.println();
Serial.print("Device 0 Alarms: ");
printAlarms(insideThermometer);
Serial.println();
Serial.print("Device 1 Address: ");
printAddress(outsideThermometer);
Serial.println();
Serial.print("Device 1 Alarms: ");
printAlarms(outsideThermometer);
Serial.println();
Serial.println("Setting alarm temps...");
// alarm when temp is higher than 30C
sensors.setHighAlarmTemp(insideThermometer, 30);
// alarm when temp is lower than -10C
sensors.setLowAlarmTemp(insideThermometer, -10);
// alarm when temp is higher than 31C
sensors.setHighAlarmTemp(outsideThermometer, 31);
// alarn when temp is lower than 27C
sensors.setLowAlarmTemp(outsideThermometer, 27);
Serial.print("New Device 0 Alarms: ");
printAlarms(insideThermometer);
Serial.println();
Serial.print("Ne Device 1 Alarms: ");
printAlarms(outsideThermometer);
Serial.println();
}
// function to print a device address
void printAddress(DeviceAddress deviceAddress)
{
for (uint8_t i = 0; i < 8; i++)
{
if (deviceAddress[i] < 16) Serial.print("0");
Serial.print(deviceAddress[i], HEX);
}
}
// function to print the temperature for a device
void printTemperature(DeviceAddress deviceAddress)
{
float tempC = sensors.getTempC(deviceAddress);
Serial.print("Temp C: ");
Serial.print(tempC);
Serial.print(" Temp F: ");
Serial.print(DallasTemperature::toFahrenheit(tempC));
}
void printAlarms(uint8_t deviceAddress[])
{
char temp;
temp = sensors.getHighAlarmTemp(deviceAddress);
Serial.print("High Alarm: ");
Serial.print(temp, DEC);
Serial.print("C/");
Serial.print(DallasTemperature::toFahrenheit(temp));
Serial.print("F | Low Alarm: ");
temp = sensors.getLowAlarmTemp(deviceAddress);
Serial.print(temp, DEC);
Serial.print("C/");
Serial.print(DallasTemperature::toFahrenheit(temp));
Serial.print("F");
}
// main function to print information about a device
void printData(DeviceAddress deviceAddress)
{
Serial.print("Device Address: ");
printAddress(deviceAddress);
Serial.print(" ");
printTemperature(deviceAddress);
Serial.println();
}
void checkAlarm(DeviceAddress deviceAddress)
{
if (sensors.hasAlarm(deviceAddress))
{
Serial.print("ALARM: ");
printData(deviceAddress);
}
}
void loop(void)
{
// call sensors.requestTemperatures() to issue a global temperature
// request to all devices on the bus
Serial.print("Requesting temperatures...");
sensors.requestTemperatures();
Serial.println("DONE");
// Method 1:
// check each address individually for an alarm condition
checkAlarm(insideThermometer);
checkAlarm(outsideThermometer);
/*
// Alternate method:
// Search the bus and iterate through addresses of devices with alarms
// space for the alarm device's address
DeviceAddress alarmAddr;
Serial.println("Searching for alarms...");
// resetAlarmSearch() must be called before calling alarmSearch()
sensors.resetAlarmSearch();
// alarmSearch() returns 0 when there are no devices with alarms
while (sensors.alarmSearch(alarmAddr))
{
Serial.print("ALARM: ");
printData(alarmAddr);
}
*/
}