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Lesson 18: Temperature Sensor Module (DS18B20)

In this lesson, you’ll learn how to integrate and read temperature data from DS18B20 sensors using the Raspberry Pi Pico W. You’ll begin by setting up a OneWire bus on the GPIO pin and scanning for DS18X20 devices. The main focus of the lesson is continuously reading and displaying temperature measurements from these sensors.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Universal Maker Sensor Kit	94	Universal Maker Sensor Kit

You can also buy them separately from the links below.

Component Introduction	Purchase Link
Raspberry Pi Pico W	BUY
Temperature Sensor Module (DS18B20)	-
Breadboard	BUY

Wiring

Code

Note

Open the 18_ds18b20_module.py file under the path of universal-maker-sensor-kit-main/pico/Lesson_18_DS18B20_Module or copy this code into Thonny, then click “Run Current Script” or simply press F5 to run it. For detailed tutorials, please refer to Open and Run Code Directly.
Don’t forget to click on the “MicroPython (Raspberry Pi Pico)” interpreter in the bottom right corner.

from machine import Pin
import onewire
import time, ds18x20

# Initialize the OneWire bus on GPIO pin 12
ow = onewire.OneWire(Pin(12))

# Create a DS18X20 instance using the OneWire bus
ds = ds18x20.DS18X20(ow)

# Scan for DS18X20 devices on the bus and print their addresses
roms = ds.scan()
print('found devices:', roms)

# Continuously read and print temperature data from the sensors
while True:
    # Start the temperature conversion process
    ds.convert_temp()
    # Wait for the conversion to complete (750 ms for DS18X20)
    time.sleep_ms(750)

    # Read and print the temperature from each sensor found on the bus
    for rom in roms:
        print(ds.read_temp(rom))

    # Wait for a short period before the next reading (1000 ms)
    time.sleep_ms(1000)

Code Analysis

Importing Libraries

The code begins by importing necessary libraries. machine is used for controlling GPIO pins, onewire for the OneWire communication protocol, ds18x20 for the specific temperature sensor, and time for delays.

Regarding OneWire in MicroPython, you can refer to OneWire driver.
```
from machine import Pin
import onewire
import time, ds18x20
```
Initializing OneWire Bus

A OneWire bus is initialized on GPIO pin 12. This sets up the communication between the Raspberry Pi Pico W and the DS18B20 sensor.
```
ow = onewire.OneWire(Pin(12))
```
Creating DS18X20 Instance

A DS18X20 instance is created using the OneWire bus. This instance is used to interact with the temperature sensor.
```
ds = ds18x20.DS18X20(ow)
```
Scanning for Devices

The code scans for DS18X20 devices on the OneWire bus and prints their addresses. This is important for identifying the connected sensors.
```
roms = ds.scan()
print('found devices:', roms)
```
Reading Temperature Data
- The main loop of the program continuously reads temperature data from the sensor.
- It starts the temperature conversion process and waits for it to complete, which takes about 750 milliseconds.
- It then reads and prints the temperature from each sensor found on the bus.
- The loop pauses for 1000 milliseconds before repeating.
```
while True:
    ds.convert_temp()
    time.sleep_ms(750)
    for rom in roms:
        print(ds.read_temp(rom))
    time.sleep_ms(1000)
```