Raspberry Pi DS18B20 Tutorial | Basic Interface and IoT Monitor

In the earlier project involving the DS18B20 Digital Sensor, we explored how to connect an Arduino with the DS18B20 sensor and display the temperature on a 16×2 LCD display. In this project, we will focus on the interface between the Raspberry Pi and the DS18B20 Temperature Sensor, as well as the ability to monitor the temperature from a remote location through a web-based temperature monitor.

The project comprises two main parts. The first part involves establishing the connection between the DS18B20 sensor and the Raspberry Pi, and then displaying the temperature readings on the terminal. In the second part, we will access the Raspberry Pi over the internet using Dataplicity, allowing us to view the temperature readings from a remote computer.

Overview

In the previous tutorial, we covered the DS18B20 Temperature Sensor in detail. However, as a quick recap, here are a few important points about the sensor.

The DS18B20 is a digital temperature sensor that communicates via a 1-Wire interface. This makes it particularly suitable for projects involving the Raspberry Pi, as the Pi lacks analog input pins. Therefore, opting for a digital sensor like the DS18B20 is a natural choice for implementation in Raspberry Pi projects.

The DS18B20 Sensor, in its TO-92 package, consists of three pins: GND, DQ (Data), and VDD. Power can be supplied to the sensor through either the VDD pin or the sensor can draw power from the DQ pin in parasite power mode.

For additional details on the DS18B20 Temperature Sensor and instructions on how to interface it with an Arduino, you can refer to the Arduino DS18B20 Interface Tutorial.

Circuit Diagram of Raspberry Pi DS18B20 Interface

The circuit diagram below depicts the interface between the DS18B20 Temperature Sensor and the Raspberry Pi. The first image illustrates the connections between the Raspberry Pi and the DS18B20 using Fritzing Parts.

[Image: Circuit diagram of DS18B20 Temperature Sensor interfaced with Raspberry Pi using Fritzing Parts.]

For a more comprehensive understanding of the connections, referring to the following wiring diagram can be quite helpful.

Components Required

To undertake this project, you will need the following components and materials:

– Raspberry Pi 3 Model B
– DS18B20 Digital Temperature Sensor
– 4.7KΩ Resistor (1/4 Watt)
– Breadboard
– Connecting wires
– Micro USB Cable
– Computer with Internet Connectivity

Circuit Design

To begin, make the following connections:

1. Connect the VDD pin of the DS18B20 sensor to the 3.3V pin of the Raspberry Pi.
2. Connect the GND pin of the DS18B20 sensor to the GND pin of the Raspberry Pi. It's worth noting that the DS18B20 sensor can tolerate a +5V supply, but for compatibility with the Raspberry Pi's GPIO voltage level, we use 3.3V.
3. Connect a 4.7KΩ resistor (pull-up resistor) between the DQ pin of the DS18B20 sensor and the 3.3V pin of the Raspberry Pi. This resistor helps in maintaining the voltage level on the DQ pin.
4. Lastly, connect the DQ pin of the DS18B20 sensor to GPIO4 (physical pin 7) of the Raspberry Pi. This connection allows the Raspberry Pi to communicate with the sensor and receive temperature readings.

Raspberry Pi DS18B20 Temperature Sensor Interface

Next, we will explore the process of interfacing the DS18B20 Temperature Sensor with the Raspberry Pi. With this interface, you can develop various applications such as a weather station, remote temperature monitor, temperature data logger, and more.

Enable 1-Wire Interface in Raspberry Pi

Make the necessary connections according to the provided circuit diagram and power on the Raspberry Pi. As the DS18B20 sensor communicates exclusively via the 1-Wire interface, we need to enable this feature on the Raspberry Pi. To do so, open the Command Prompt on the Raspberry Pi and access the config.txt file by executing the following command:

sudo nano /boot/config.txt
Towards the end of the config.txt file, append the following statement:
dtoverlay=w1–gpio
Save the changes made to the config.txt file by pressing Ctrl+x and then y. Once the file is saved, you will need to reboot the Raspberry Pi for the changes to take effect. To do this, use the following command to initiate a reboot of your Raspberry Pi:
sudo reboot

Check whether the Sensor is Working

The subsequent steps will help you verify whether your DS18B20 Temperature Sensor is functioning correctly or not. You may choose to skip this step and proceed with writing the Python program for the Raspberry Pi.

Once your Raspberry Pi has completed the reboot process, log in to your Raspberry Pi and enter the following commands in the command prompt:

sudo modprobe w1-gpio
sudo modprobe w1-therm
Now, navigate to the devices directory by executing the following command:
cd /sys/bus/w1/devices

Within this directory, you can list the available devices using the “ls” command.

In your case, you will find a directory corresponding to the DS18B20 sensor, such as “28-0316555c2fff”. Use the “cd” command to access this directory.

cd 28-0316555c2fff

To view the raw temperature reading from the sensor, use the following command.

cat w1_slave

If you notice, the value t=25250 at the end of the second line of the result represents the temperature as 25.25 0C.

Python Program for Reading Temperature from DS18B20

I’ve created a folder called ‘projects’ in Raspberry Pi’s Home. Change to this directory and create a new Python file with name ‘temperature.py’ using vim editor.

sudo vim python temperature.py

In this file, type the following code and save the file.

 

import os
import glob
import time
os.system(‘modprobe w1-gpio')
os.system(‘modprobe w1-therm')
base_dir = ‘/sys/bus/w1/devices/'
device_folder = glob.glob(base_dir + '28*')[0]
device_file = device_folder + ‘/w1_slave'
def read_temp_raw():
f = open(device_file, ‘r')
lines = f.readlines()
f.close()
return lines
def read_temp():
lines = read_temp_raw()
while lines[0].strip()[3:] != ‘YES':
time.sleep(0.2)
lines = read_temp_raw()
equals_pos = lines[1].find(‘t=')
if equals_pos != 1:
temp_string = lines[1][equals_pos+2:]
temp_c = float(temp_string) / 1000.0
return temp_c
while True:
i=(read_temp())
print i, ‘Degree Celsius'
time.sleep(1)

After writing or copying the code in to editor, save the file and you are ready to run the script. To run the Python Script, simply use the following command.

sudo python temperature.py
The temperature reading will be provided in degrees Celsius. If you wish to display the temperature in Fahrenheit, you can modify the code within the “def read_temp():” section accordingly.

IoT based Temperature Monitor

Let's take the project further by setting up a web-based temperature monitor. To accomplish this, we will utilize the services of Dataplicity. Follow the link provided to access the Dataplicity homepage.

Enter your email address in Section 1 and click on “Start.” You will be presented with a code in Section 2. Copy this code and paste it into the Command Prompt (Terminal) of the Raspberry Pi to activate the remote shell.

The code will be something like this.

curl https://www.dataplicity.com/xxxxxxxx.py | sudo python
Upon entering the code, the system will initiate the download of the required file onto your Raspberry Pi. It will then proceed to register your device with the Dataplicity Server, configure your system accordingly, and run the remote agent to establish the connection.

Next, click on “Done” on the Dataplicity website to initiate remote access to your Raspberry Pi. The terminal will become enabled, allowing you to log in using your Raspberry Pi's credentials.

Assuming that your Python script for the DS18B20 sensor is stored in the “projects” folder, navigate to that directory using the following command:

cd projects

Once you are in the correct directory, execute the script using the following command:

sudo python temperature.py

About The Author

Ibrar Ayyub

I am an experienced technical writer with a Master's degree in computer science from BZU Multan University. I have written for various industries, mainly home automation, and engineering. I have a clear and simple writing style and am skilled in using infographics and diagrams. I am a great researcher and is able to present information in a well-organized and logical manner.

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