Introducing the DS18B20 Temperature Sensor

The DS18B20 temperature sensor is a 1-wire digital temperature sensor. Each sensor has a unique 64-bit serial number, which means you can use many sensors on the same data bus (this means many sensors connected to the same GPIO). This is specially useful for data logging and temperature control projects. The DS18B20 is a great sensor because it is cheap, accurate and very easy to use.

The following figure shows the DS18B20 temperature.

Note: there’s also a waterproof version of the DS18B20 temperature sensor.

Here’s the main specifications of the DS18B20 temperature sensor:

Comunicates over 1-wire bus communication

Operating range temperature: -55oC to 125oC

Accuracy +/-0.5 oC (between the range -10oC to 85oC)

From left to right: the first pin is GND, the second is data, and the rightmost pin is VCC.

Where to Buy the DS18B20 Temperature Sensor?

Check the links below to compare the DS18B20 temperature sensor price on different stores:

DS18B20 digital temperature sensor

DS18B20 digital temperature sensor (waterproof version)

Wiring Multiple DS18B20 Sensors

Here’s a list of the parts you need to follow this example:

ESP32 DOIT DEVKIT V1 Board – read ESP32 Development Boards Review and Comparison

DS18B20 temperature sensor (we’re using 3 sensors in this example)

4.7k Ohm resistor

Jumper wires

Breadboard

When wiring the DS18B20 temperature sensor you need to add a 4.7k Ohm resistor between VCC and the data line. The following schematic shows an example for three sensors (you can add more sensors if needed).

Preparing the Arduino IDE

?

There’s an add-on for the Arduino IDE that allows you to program the ESP32 using the Arduino IDE and its programming language. Follow one of the next tutorials to prepare your Arduino IDE to work with the ESP32, if you haven’t already.

Windows instructions – ESP32 Board in Arduino IDE

Mac and Linux instructions – ESP32 Board in Arduino IDE

Installing Libraries

Before uploading the code, you need to install two libraries in your Arduino IDE. The OneWire library by Paul Stoffregen and the Dallas Temperature library. Follow the next steps to install those libraries.

OneWire library

Click here to download the OneWire library. You should have a .zip folder in your Downloads

Unzip the .zip folder and you should get OneWire-master folder

Rename your folder from OneWire-master to OneWire

Move the OneWire folder to your Arduino IDE installation libraries folder

Finally, re-open your Arduino IDE

Dallas Temperature library

Click here to download the DallasTemperature library. You should have a .zip folder in your Downloads

Unzip the .zip folder and you should get Arduino-Temperature-Control-Library-master folder

Rename your folder from Arduino-Temperature-Control-Library-master to DallasTemperature

Move the DallasTemperaturefolder to your Arduino IDE installation libraries folder

Finally, re-open your Arduino IDE

Getting the DS18B20 Sensor Address

Each DS18B20 temperature sensor has a serial number assigned to it. First, you need to find that number to label each sensor accordingly. You need to do this, so that later you know from which sensor you’re reading the temperature from.

Upload the following code to the ESP32. Make sure you have the right board and COM port selected.

#include <OneWire.h>

// Based on the OneWire library example

OneWire ds(4); //data wire connected to GPIO 4

void setup(void) {

Serial.begin(115200);

}

void loop(void) {

byte i;

byte addr[8];

if (!ds.search(addr)) {

Serial.println(" No more addresses.");

Serial.println();

ds.reset_search();

delay(250);

return;

}

Serial.print(" ROM =");

for (i = 0; i < 8; i++) {

Serial.write(' ');

Serial.print(addr[i], HEX);

}

}

Wire just one sensor at a time to find its address (or successively add a new sensor) so that you’re able to identify each one by its address. Then, you can add a physical label to each sensor. Open the Serial Monitor at a baud rate of 9600 and you should get something as follows (but with different addresses):

Untick the “Autoscroll” option so that you’re able to copy the addresses. In our case we’ve got the following addresses:

Sensor 1: 28 FF 77 62 40 17 4 31

Sensor 2: 28 FF B4 6 33 17 3 4B

Sensor 3: 28 FF A0 11 33 17 3 96

Getting Temperature From Multiple Sensors

Getting the temperature from multiple sensors on the same common data bus is very straightforward.

The example code below reads temperature in Celsius and Fahrenheit from each sensor and prints the results in the Serial Monitor.

// Include the libraries we need

#include <OneWire.h>

#include <DallasTemperature.h>

// Data wire is connected to GPIO15

#define ONE_WIRE_BUS 15

// Setup a oneWire instance to communicate with a OneWire device

OneWire oneWire(ONE_WIRE_BUS);

// Pass our oneWire reference to Dallas Temperature sensor

DallasTemperature sensors(&oneWire);

DeviceAddress sensor1 = { 0x28, 0xFF, 0x77, 0x62, 0x40, 0x17, 0x4, 0x31 };

DeviceAddress sensor2 = { 0x28, 0xFF, 0xB4, 0x6, 0x33, 0x17, 0x3, 0x4B };

DeviceAddress sensor3= { 0x28, 0xFF, 0xA0, 0x11, 0x33, 0x17, 0x3, 0x96 };

void setup(void){

Serial.begin(115200);

sensors.begin();

}

void loop(void){

Serial.print("Requesting temperatures...");

sensors.requestTemperatures(); // Send the command to get temperatures

Serial.println("DONE");

Serial.print("Sensor 1(*C): ");

Serial.print(sensors.getTempC(sensor1));

Serial.print(" Sensor 1(*F): ");

Serial.println(sensors.getTempF(sensor1));

Serial.print("Sensor 2(*C): ");

Serial.print(sensors.getTempC(sensor2));

Serial.print(" Sensor 2(*F): ");

Serial.println(sensors.getTempF(sensor2));

Serial.print("Sensor 3(*C): ");

Serial.print(sensors.getTempC(sensor3));

Serial.print(" Sensor 3(*F): ");

Serial.println(sensors.getTempF(sensor3));

delay(2000);

}

Open the Serial Monitor at a baud rate of 115200 and you should get something similar.