How to Read Temperature with a DS18B20 on Raspberry Pi 2

Welcome! This guide shows you how to connect a DS18B20 digital temperature sensor to a Raspberry Pi 2 and read the room temperature accurately.

What You’ll Need

• DS18B20 waterproof sensor (buy online)
• 4.7 kΩ pull‑up resistor (yellow‑violet‑red‑gold)
• Jumper wires
• Raspberry Pi 2 (any model with GPIO)

Step 1 – Wiring the Sensor

The DS18B20 uses a 1‑Wire interface. Connect it as follows:

• Red wire (VDD) → 3.3 V rail on the Pi
• Black wire (GND) → Ground rail on the Pi
• Yellow wire (DQ) → GPIO 4 (physical pin 7)

Place the 4.7 kΩ resistor between the 3.3 V line and the DQ line to act as a pull‑up. The resistor’s “3.3 V” end should touch the red (VDD) side.

Step 2 – Enable the 1‑Wire Interface

1. Edit the boot configuration file:

sudo nano /boot/config.txt

2. Add or uncomment the line:

dtoverlay=w1-gpio

3. Save and exit, then reboot:

sudo reboot

Step 3 – Load Kernel Modules

After the Pi restarts, load the 1‑Wire drivers:

sudo modprobe w1-gpio
sudo modprobe w1_therm

Step 4 – Verify the Sensor is Detected

Check the device tree for the sensor ID:

ls -l /sys/bus/w1/devices/

You should see a folder beginning with 28-, e.g., 28-000006dfa76c.

Step 5 – Read the Temperature

Each sensor exposes its data through w1_slave. View it with:

cat /sys/bus/w1/devices/28-000006dfa76c/w1_slave

The output contains two lines; the second line ends with t=XXXXX, where XXXXX is the temperature in thousandths of a degree Celsius. For example, t=23450 equals 23.450 °C.

Optional – Parse the Value with a Script

Here’s a quick Python snippet to convert the raw reading into °C:

#!/usr/bin/env python3
import time, glob
sensor = glob.glob('/sys/bus/w1/devices/28-*/w1_slave')[0]
while True:
    with open(sensor, 'r') as f:
        lines = f.readlines()
    if lines[0].strip().endswith('YES'):
        temp_raw = lines[1].split('t=')[1]
        temp_c = float(temp_raw) / 1000.0
        print(f"Temperature: {temp_c:.3f} °C")
    else:
        print("Reading error")
    time.sleep(2)

Save this as temp_read.py, make it executable, and run it to get live temperature updates.

By following these steps, you’ll have a reliable temperature monitor running on your Raspberry Pi 2.

For deeper insights, see the Adafruit DS18B20 guide.