Interfacing DS18B20 Temperature Sensor with ESP8266 NodeMCU

Status Untested

Build Time ⏱️ 15-20 mins

Learn Time 📚 30 mins

Experience Level 🛠️ 1 year

Learn how to connect a DS18B20 1-Wire digital temperature sensor to an ESP8266 (NodeMCU) board and read temperature values via the Serial Monitor in Celsius.

1. Overview & Specifications

The DS18B20 is a 1-Wire digital temperature sensor that measures temperatures from -55°C to +125°C with ±0.5°C accuracy (between -10°C and +85°C). It operates on a supply voltage from 3.0V to 5.5V, making it fully compatible with the 3.3V logic level of the ESP8266.

2. Bill of Materials (BOM)

1x ESP8266 Development Board (NodeMCU)
1x DS18B20 Temperature Sensor (TO-92 or Waterproof Probe)
1x 4.7 kΩ Resistor (1/4W)
1x Breadboard & Jumper Wires

3. Hardware Connections & Pinout

The DS18B20 uses a single data line for communication (1-Wire protocol). A 4.7 kΩ pull-up resistor is required between the DQ (Data) line and the 3.3V supply line for stable communication.

DS18B20 Pinout Table

DS18B20 Pin	Function	ESP8266 Connection
Pin 1 (GND)	Ground	GND
Pin 2 (DQ)	1-Wire Data Line	D4 (GPIO2) (Requires 4.7 kΩ pull-up to 3.3V)
Pin 3 (VDD)	Power Supply (3.0V – 5.5V)	3.3V

Note: Multiple DS18B20 sensors can be connected in parallel on the exact same DQ line because each sensor has a unique 64-bit factory-lasered ROM ID code.

4. Required Arduino Libraries

Before uploading the code, install the following libraries via the Arduino IDE Library Manager (Tools > Manage Libraries):

OneWire by Paul Stoffregen
DallasTemperature by Miles Burton

5. Source Code

Upload the following low-level ANSI-compatible C++ Arduino sketch to your NodeMCU board:

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

// Data wire is connected to NodeMCU Pin D4 (GPIO2)
#define ONE_WIRE_BUS D4

// Setup a oneWire instance to communicate with any OneWire devices
OneWire oneWire(ONE_WIRE_BUS);

// Pass our oneWire reference to Dallas Temperature sensor handler
DallasTemperature sensors(&oneWire);

void setup() {
  // Initialize serial communication at 115200 baud
  Serial.begin(115200);
  
  // Start up the DallasTemperature library
  sensors.begin();
}

void loop() {
  // Send the command to request temperature from all devices on the bus
  sensors.requestTemperatures(); 
  
  // Fetch temperature in Celsius for the first sensor on the bus (index 0)
  float tempC = sensors.getTempCByIndex(0);
  
  // Output result to Serial Monitor
  Serial.print("Temperature: ");
  Serial.print(tempC);
  Serial.println(" °C");
  
  // Delay 1 second before the next reading
  delay(1000);
}

6. Testing & Verification

Connect your NodeMCU board to your PC via Micro-USB.
Select board NodeMCU 1.0 (ESP-12E Module) and correct COM port in Arduino IDE.
Compile and upload the sketch.
Open the Serial Monitor set to 115200 baud.
You should see real-time temperature updates printed every second.