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Let’s read the temperature with a DS18B20 Temperature Probe, connected to a Raspberry Pi!

Index

• Introduction
• Prerequisites
• Hardware
• Setup
• Software Approach
• Using ‘w1thermsensor’ python library
• Conclusion
• Resources

Introduction

Recently I bought a DS18B20 Temperature Probe from my local electronic store. I want to do some temperature measures and this probe works outdoors, indoors, is waterproof, and has a range between -55°C and +125°C. That should be enough for all spots I can imagen to test it in!

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Prerequisites

Read this blog post about how to use the GPIO pins on a Raspberry Pi:

• https://www.raspberryfield.life/2020/05/18/raspberry-pi-getting-started-with-gpio/ [2020-05-23]

This is also a good post to read if you are unsure how to work with a Raspberry Pi:

• https://www.raspberryfield.life/2020/05/22/headless-raspberry-pi/ [2020-05-23]

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Hardware

The DS18B20 Temperature Probe is based on the component DS18B20. Normally you need to use a resistor with DS18B20, but that is already built into this probe. As already mentioned, it has a range between -55°C and +125°C.

It outputs the information digitally, that’s perfect because the Raspberry Pi is digital only, it does not have analogue input readings on the GPIO pins.

The probe can be used for your Raspberry Pi or Arduino projects. It comes with a socket that makes it easier to connect to.

Reading the documentation about DS18B20, it is possible to connect several temperature sensors on the same data wire because each one broadcast a unique number associated with it. It is also possible to feed power via the data wire, so you only need two wires (called parasitic connection).

The Probe can be fed 3-5V.

In this post we will be using the simplest setup. Only one probe and using all three wires.

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Setup

Here I have connected the Probe to the Pi via the socket and a bread board:

Wires:

• Red – Vcc (+5V)
• Black – Gnd
• Yellow – Data (GPIO15)

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Software Approach

Now when you want to interface with a device like this, you have a choice between two approaches to make:

1. Read the datasheet of the device and components and figure out in detail how everything is working and write a software on your own for it.
2. Go on the Internet and try to find someone that already did approach 1, so you don’t have to waste your time and energy and probably making a lot of mistakes on the way.

Going for approach 2, I found this github page:

https://github.com/timofurrer/w1thermsensor [2020-05-23].

This is a library in Python used for interfacing with the DS18B20 temperature sensor!

It is well documented and has plenty of examples, let’s use this one!

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Using ‘w1thermsensor’ python library

To use the library, we first need to install it.

First run:

To install the w1thermsensor library, log in to your Pi and execute this command:

After the installation, we need to make changes to a config file in Raspbian.

From the authors github page:

“On the Raspberry Pi, you will need to add dtoverlay=w1-gpio” (for regular connection) or dtoverlay=w1-gpio,pullup=”y” (for parasitic connection) to your /boot/config.txt. The default data pin is GPIO4 (RaspPi connector pin 7), but that can be changed from 4 to x with dtoverlay=w1-gpio,gpiopin=x “.

We use a regular connection where I want the data wire on GPIO15. So, add this line to the file /boot/config.txt:

Reboot your Pi.

Here is a code example, how to use the library in Python3:

tempProbeDS18B20.py

from w1thermsensor import W1ThermSensor
import time
import traceback

print ("Starting tempProbDS18B20.py, Press Ctrl+C to exit.")

#Initialize instance of W1ThermSensor
sensor = W1ThermSensor()

degree_sign = '\u00b0'

try:
	while True:
		#Print sensor ID and its temperature.
		print ("Sensor: %s(id), temp: %.2f%sCelsius." % (sensor.id, sensor.get_temperature(), degree_sign))
		time.sleep(1) #1second.

#Exit loop by Ctrl+C
except KeyboardInterrupt:
	#Put code here to run before exit by Ctrl+C here:
	print ("\n Keyboard interrupt, exiting program...")

except Exception as e:
	print ("An unforeseen error has occurred!")
	print ("Error message: ", e, ".")
	print (traceback.format_exc())
	print ("-----")

finally:
	print ("Thank you for using tempProbDS18B20.py! Bye!")

Here is output from the program:

A simple test with hot water:

And the output from the program:

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Conclusion

In this post we have:

• Read the temperature from an external device.
• Used a third-party library.

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Resources

• Nice tutorial: https://www.circuitbasics.com/raspberry-pi-ds18b20-temperature-sensor-tutorial/ [2020-05-23]
• Datasheet DS18B20: https://www.alldatasheet.com/datasheet-pdf/pdf/58557/DALLAS/DS18B20.html [2020-05-23]
• Suppliers homepage about the DS18B20 Temperatur Probe: https://www.velleman.eu/products/view/?id=439184 [2020-05-23]
• w1thermsensor library: https://github.com/timofurrer/w1thermsensor [2020-05-23]

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