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ESP32 with Multiple DS18B20 Temperature Sensors

This guide shows how to read temperature from multiple DS18B20 temperature sensors with the ESP32 using Arduino IDE. We’ll show you how to wire the sensors on the same data bus to the ESP32, install the needed libraries, and a sketch example you can use in your own projects. This tutorial is also compatible with the ESP8266 and the Arduino boards.

We have a getting started guide for the DS18B20 temperature sensor that you may find useful: Guide for DS18B20 Temperature Sensor with Arduino.

You might also like reading other DS18B20 guides:

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.

  • 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).

In the previous schematic, the round side of the sensor is facing backwards. The flat part is facing forward.

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.

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

  1. Click here to download the OneWire library. You should have a .zip folder in your Downloads
  2. Unzip the .zip folder and you should get OneWire-master folder
  3. Rename your folder from OneWire-master to OneWire
  4. Move the OneWire folder to your Arduino IDE installation libraries folder
  5. Finally, re-open your Arduino IDE

Dallas Temperature library

  1. Click here to download the DallasTemperature library. You should have a .zip folder in your Downloads
  2. Unzip the .zip folder and you should get Arduino-Temperature-Control-Library-master folder
  3. Rename your folder from Arduino-Temperature-Control-Library-master to DallasTemperature
  4. Move the DallasTemperaturefolder to your Arduino IDE installation libraries folder
  5. 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.

/*
Gnd_To_Vcc
 */

#include <OneWire.h>

// Based on the OneWire library example

OneWire ds(15);  //data wire connected to GPIO15

void setup(void) {
  Serial.begin(9600);
}

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.

/*
Gnd_To_Vcc
 */

// 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.

How the Code Works

First, include the needed libraries:

#include <OneWire.h>
#include <DallasTemperature.h>

Create the instances needed for the temperature sensor. The temperature sensor is connected to GPIO 15.

// Data wire is connected to ESP32 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);

Start the Dallas temperature library for the DS18B20 sensor.

sensors.begin();

Then, enter the addresses you’ve found previously for each temperature sensor. In our case, we have the following:

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 };

In the setup(), initialize a Serial communication and start the Dallas temperature library for the DS18B20 sensor.

void setup(void){
  Serial.begin(115200);
  sensors.begin();
}

In the loop(), request the temperatures both in Celsius and Fahrenheit and print the results on the Serial Monitor.

First, you need to request the temperatures using the following line of code:

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

Then, you can request the temperature by using the sensors address:

  • sensors.getTempC(SENSOR_ADDRESS) – requests the temperature in Celsius
  • sensors.getTempF(SENSOR_ADDRESS) – requests the temperature in Fahrenheit

For example, to request temperature in Celsius for sensor 1, you use:

sensors.getTempC(sensor1)

In which sensor1 is a variable that holds the address of the first sensor.

This is just a simple sketch example to show you how to get temperature from multiple DS18B20 sensors using the ESP32. This code is also compatible with the ESP8266 and Arduino boards.

Taking It Further

Getting temperature from multiple DS18B20 temperature sensors is specially useful in monitoring and temperature control projects and data logging. Learn how to log the collected data to a microSD card:

You can also publish your readings via MQTT to Node-RED and display your data in charts. We have a tutorial about that subject in the link below:

Thanks for reading.

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Published by Gnd_To_Vcc

Here to spread my knowledge . Knowledge should always be spread not stored.

7 thoughts on “ESP32 with Multiple DS18B20 Temperature Sensors

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