DS18B20 单线数字温度传感器，即“一线器件”，其具有独特的优点：
（ 1 ）采用单总线的接口方式 与微处理器连接时 仅需要一条口线即可实现微处理器与 DS18B20 的双向通讯。 单总线具有经济性好，抗干扰能力强，适合于恶劣环境的现场温度测量，使用方便等优点，使用户可轻松地组建传感器网络，为测量系统的构建引入全新概念。
（ 2 ）测量温度范围宽，测量精度高 DS18B20 的测量范围为 -55 ℃ ~ 125 ℃ ； 在 -10~ 85°C 范围内，精度为 ± 0.5°C 。
（ 3 ）持多点组网功能 多个 DS18B20 可以并联在惟一的单线上，实现多点测温。
（ 4）供电方式灵活 DS18B20 可以通过内部寄生电路从数据线上获取电源。因此，当数据线上的时序满足一定的要求时，可以不接外部电源，从而 使系统结构更趋简单，可靠性更高。
（ 5 ）测量参数可配置 DS18B20 的测量分辨率可通过程序设定 9~12 位。
DS18B20 具有体积更小、适用电压更宽、更经济、可选更小的封装方式，更宽的电压适用范围，适合于构建自己的经济的测温系统，因此也就被设计者们所青睐。
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，搜索下载安装相应的库，不然程序写好了，编译时会报错；
搜索 18B20 ，看到18B20相关的库，点击 安装好，
打开 文件-示例，第三方库刚安装好的库，找到第一个例子Alarm；
看到除了DallasTemperature.h，还需要另一个库OneWire.h，再按之前步骤，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，选择对应的开发版和端口，编译上传烧录，
3、接线，必须加电阻，不加电阻检测不到设备；
管脚定义：面朝印字面，左为GND，右为VCC，中间为数字输出引脚（须接上4.7K—10K的上拉电阻）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、接好线后，再用USB连接电脑，打开串口监视器查看结果；
Alarm案例代码，可根据需要自行修改：
#include <OneWire.h>//引用单总线头文件
#include <DallasTemperature.h>//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();//初始化器件
// locate devices on the bus
Serial.print("Found ");
Serial.print(sensors.getDeviceCount(), DEC);//DEC的意思是串口数据以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("New 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);
}
*/
}
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