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DHT11 Humidity and Temperature Sensor With Raspberry PI Pico and MicroPython

raspberry pi pico dht11 featured image
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The DHT11 is a very simple chip (easy to find on common ecommerce stores) which brings to your projects the ability to read Temperature and Humidity. Let’s see how to connect and use DHT11 with Raspberry PI Pico and use it with MicroPython

In this tutorial, I’m going to show you how to connect and use a DHT11 sensor to Raspberry PI Pico with MicroPython. Please note that if you are interested in using a Raspberry PI computer board (like RPI Zero), you will need to refer to my Use Raspberry PI with DHT11 Temperature and Humidity Sensor tutorial.

DHT11 sensor

As already explained in that post, DHT11 Sensor is a cheap solution to measure indoor Temperature and Humidity (it is not indicated for outdoor uses). You can use it with Arduino (usually in Weather Station projects or similar) or alone, directly connected to a Raspberry PI.

What We Need

As usual, I suggest adding from now to your favourite e-commerce shopping cart all needed hardware, so that at the end you will be able to evaluate overall costs and decide if continuing with the project or removing them from the shopping cart. So, hardware will be only:

raspberry pi pico microcontroller

Please note that there are 2 versions of DHT11 modules. One including a board (which only adds a pull-up resistor to data pin), which has 3 pins, and one without this board, having only the sensor (and 4 pins, one of which unused). In this post, I’m using the first one, similar to images in this post.

You may also find it useful to evaluate a sensors kit (like Elegoo Starter Kit) which is a cost-saving solution if you want to test many sensors for different purposes.

Check hardware prices with the following links:

amazon raspberry pi pico box
Amazon Breadboard box
Amazon Dupont Wiring box
Amazon DHT11 umidity temperature box

Wiring Diagram

Please find below the wiring diagram picture:

raspberry pi pico dht11 wiring diagram

…and some detail images:

raspberry pi pico dht11 details 01
raspberry pi pico dht11 details 02
raspberry pi pico dht11 details 03

Step-by-Step Procedure

Prepare cabling according to the previous paragraph. Connect RPI Pico to Thonny (you can refer to my tutorial about the First steps with Raspberry PI Pico).

Get DHT11 MicroPython Libraries

Download the “dht.py” file from GitHub repository of ikornaselur.

You can also download a copy of it from my download area with the following link:

According to my Adding external modules to MicroPython with Raspberry PI Pico tutorial, add this file in your Raspberry PI Pico root folder or inside a folder named “lib”. This is how appears in my RPI Pico storage:

thonny files dht11 raspberry pi pico

Get and Understand my picoDHT11.py Code

Now download my main file to test your DHT11 sensor:

I’ll explain all code lines in the following paragraphs. It is really simple as the dht.py library makes everything needed to manage the temperature and humidity sensor.

First of all, we import required libraries:

from machine import Pin
import utime as time
from dht import DHT11, InvalidChecksum

The data PIN number is associated to a variable for better code management and then the sensor object is associated with “dhtSensor” variable. It requires as unique parameter a PIN object initialized as output with a pull down (software) resistance. All of these operations are made within a line (the second in the following code):

dhtPIN = 15
dhtSensor = DHT11(Pin(dhtPIN, Pin.OUT, Pin.PULL_DOWN))

We arrive directly at the main loop, which simply prints the 2 values of temperature (dhtSensor.temperature) and humidity (dhtSensor.humidity). My print statement uses the format method to get a more pretty output:


while True:
    print("Temp: {}°C".format(dhtSensor.temperature), \
          "| Hum: {0:.1%}".format(dhtSensor.humidity/100))

Before repeating the loop, dht11 requires a wait time to correctly answer the requests. It tested that 1.1 seconds should give you a stable result, even if the more interval you can accept, the better is:

    time.sleep(1.1)

Running the picoDHT11.py Script

Run this script in your Thonny IDE (F5) and you will start reading measures from dht11 sensor in your Thonny shell, as in the following:

MicroPython v1.15 on 2021-04-18; Raspberry Pi Pico with RP2040

Type "help()" for more information.
>>> %Run -c $EDITOR_CONTENT
Temp: 27.7°C | Hum: 82.0%
Temp: 28.0°C | Hum: 83.0%
Temp: 27.9°C | Hum: 83.0%
Temp: 27.8°C | Hum: 83.0%
Temp: 27.9°C | Hum: 83.0%

Enjoy!

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