Using Temperature Sensors

Learn how to use temperature sensors with the Raspberry Pi Pico and MicroPython.

Overview

Welcome to Lesson 10 of the Raspberry Pi Pico with MicroPython - GPIO Mastery course. In this lesson, we will learn how to use temperature sensors with the Raspberry Pi Pico and MicroPython.

Course Content

In this lesson, you will learn:

• What temperature sensors are and how they work
• How to connect a temperature sensor to the Raspberry Pi Pico
• How to write MicroPython code to read temperature sensor values

Key Results

After you have completed this lesson, you will know how to use temperature sensors with the Raspberry Pi Pico and MicroPython. You will be able to connect a temperature sensor to the Pico, write MicroPython code to read temperature sensor values, and understand the basics of temperature sensor operation.

What you’ll need

To follow this lesson, you will need:

• A computer, tablet, or phone to read the lesson material from
• A Raspberry Pi Pico board
• A temperature sensor (such as a DS18B20 or more commonly DHT11), jumper wires, and a breadboard for hands-on practice

What are Temperature Sensors?

Temperature sensors are electronic devices that measure the temperature of the surrounding environment. There are many different types of temperature sensors, including thermistors, thermocouples, and digital temperature sensors.

Connecting a Temperature Sensor to Raspberry Pi Pico

To connect a temperature sensor to your Raspberry Pi Pico board, follow these steps:

1. Identify the type of temperature sensor you are using and its pinout.
2. Connect the temperature sensor’s pins to the appropriate GPIO pins on the Raspberry Pi Pico board.
3. If necessary, connect a pull-up or pull-down resistor to the temperature sensor’s output pin.

Reading Temperature Sensor Values with MicroPython

To read temperature sensor values using MicroPython, you will need to use a library specific to your temperature sensor. Here is an example of reading temperature values from a DS18B20 digital temperature sensor using the onewire and ds18x20 modules:

from machine import Pin
import onewire, ds18x20

# Set up the 1-wire bus
one_wire_bus = Pin(4)
ds_sensor = ds18x20.DS18X20(onewire.OneWire(one_wire_bus))

# Scan for temperature sensors on the bus
ds_sensor.scan()

# Read the temperature value
ds_sensor.convert_temp()
temperature = ds_sensor.read_temp(roms[0])

# Print the temperature value
print("Temperature: {:.2f} degrees C".format(temperature))

DHT11 example

import machine
import dht

# Initialize the DHT11 sensor on pin 15
d = dht.DHT11(machine.Pin(15))

# Read the temperature and humidity values from the sensor
d.measure()

# Print the temperature and humidity values
print("Temperature: {} C".format(d.temperature()))
print("Humidity: {} %".format(d.humidity()))

In this example code, we first import the machine module and the dht module, which provides support for the DHT11 sensor.

We then initialize the DHT11 sensor by creating an instance of the dht.DHT11 class with the GPIO pin number of the data pin connected to the sensor. In this case, we have connected the data pin of the sensor to GPIO pin 15.

Next, we use the measure() method of the DHT11 class to read the temperature and humidity values from the sensor. This method updates the internal state of the DHT11 instance with the latest sensor data.

Finally, we print the temperature and humidity values using the temperature() and humidity() methods of the DHT11 instance, respectively.

Note that the DHT11 sensor requires a pull-up resistor on the data pin, so it is recommended to use a breadboard or other prototyping board to connect the sensor to the Raspberry Pi Pico. Also, the DHT11 sensor is known to be relatively slow to respond to commands, so it may take several seconds to read the temperature and humidity values after calling the measure() method.

Conclusion

In this lesson, you learned how to use temperature sensors to measure the temperature in your environment, and how to read temperature sensor values using MicroPython. You can use this knowledge to create a variety of projects with your Raspberry Pi Pico board.

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