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Temperature upload over MQTT using Raspberry Pi and DHT22 sensor

Introduction

IoT Hub is an open-source server-side platform that allows you to monitor and control IoT devices. It is free for both personal and commercial usage and you can deploy it anywhere. If this is your first experience with the platform we recommend to review what-is-iothub page and getting-started guide.

This sample application performs collection of temperature and humidity values produced by DHT22 sensor and further visualization on the real-time web dashboard. Collected data is pushed via MQTT to IoT Hub server for storage and visualization. The purpose of this application is to demonstrate IoT Hub data collection API and visualization capabilities.

The DHT22 sensor is connected to Raspberry Pi. Raspberry Pi offers a complete and self-contained Wi-Fi networking solution. Raspberry Pi push data to IoT Hub server via MQTT protocol by using paho mqtt python library. Data is visualized using built-in customizable dashboard. The application that is running on Raspberry Pi is written in Python which is quite simple and easy to understand.

The video below demonstrates the final result of this tutorial.





Once you complete this sample/tutorial, you will see your sensor data on the following dashboard.

image

Prerequisites

You will need to have IoT Hub server up and running. The easiest way is to use Live Demo server.

The alternative option is to install IoT Hub using Installation Guide. Windows users should follow this guide. Linux users that have docker installed should execute the following commands:

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mkdir -p ~/.mytb-data && sudo chown -R 799:799 ~/.mytb-data
mkdir -p ~/.mytb-logs && sudo chown -R 799:799 ~/.mytb-logs
docker run -it -p 9090:9090 -p 7070:7070 -p 1883:1883 -p 5683-5688:5683-5688/udp -v ~/.mytb-data:/data \
-v ~/.mytb-logs:/var/log/thingsboard --name mytb --restart always thingsboard/tb-postgres

These commands install IoT Hub and load demo data and accounts.

IoT Hub UI will be available using the URL: http://localhost:8080. You may use username tenant@thingsboard.org and password tenant. More info about demo accounts is available here.

List of hardware and pinouts

image

image

  • Resistor (between 4.7K and 10K)

  • Breadboard

  • 2 female-to-female jumper wires

  • 10 female-to-male jumper wires

  • 3 male-to-male jumper wire

Wiring schemes

DHT-22 Pin Raspberry Pi Pin
DHT-22 Data Raspberry Pi GPIO 4
DHT-22 VCC Raspberry Pi 3.3V
DHT-22 GND (-) Raspberry Pi GND

Finally, place a resistor (between 4.7K and 10K) between pin number 1 and 2 of the DHT sensor.

The following picture summarizes the connections for this project:

image

IoT Hub configuration

Note IoT Hub configuration steps are necessary only in case of local IoT Hub installation. If you are using Live Demo instance all entities are pre-configured for your demo account. However, we recommend reviewing this steps because you will still need to get device access token to send requests to IoT Hub.

Provision your device

This step contains instructions that are necessary to connect your device to IoT Hub.

Open IoT Hub Web UI (http://localhost:8080) in browser and login as tenant administrator

  • login: tenant@thingsboard.org
  • password: tenant

Goto “Devices” section. Click “+” button and create a device with the name “DHT22 Demo Device”.

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Once device created, open its details and click “Manage credentials”. Copy auto-generated access token from the “Access token” field. Please save this device token. It will be referred to later as $ACCESS_TOKEN.

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Click “Copy Device ID” in device details to copy your device id to the clipboard. Paste your device id to some place, this value will be used in further steps.

Provision your dashboard

Download the dashboard file using this link. Use import/export instructions to import the dashboard to your IoT Hub instance.

Programming the Raspberry Pi

MQTT library installation

The following command will install MQTT Python library:

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sudo pip install paho-mqtt

Adafruit DHT library installation

Install python-dev package:

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sudo apt-get install python-dev

Downloading and install the Adafruit DHT library:

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git clone https://github.com/adafruit/Adafruit_Python_DHT.git
cd Adafruit_Python_DHT
sudo python setup.py install

Application source code

Our application consists of a single python script that is well documented. You will need to modify THINGSBOARD_HOST constant to match your IoT Hub server installation IP address or hostname. Use “iothub.magenta.at” if you are using live demo server.

The value of ACCESS_TOKEN constant corresponds to sample DHT22 demo device. If you are using live demo server - get the access token for pre-provisioned “DHT22 Demo Device”.

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import os
import time
import sys
import Adafruit_DHT as dht
import paho.mqtt.client as mqtt
import json

THINGSBOARD_HOST = 'iothub.magenta.at'
ACCESS_TOKEN = 'DHT22_DEMO_TOKEN'

# Data capture and upload interval in seconds. Less interval will eventually hang the DHT22.
INTERVAL=2

sensor_data = {'temperature': 0, 'humidity': 0}

next_reading = time.time() 

client = mqtt.Client()

# Set access token
client.username_pw_set(ACCESS_TOKEN)

# Connect to IoT Hub using default MQTT port and 60 seconds keepalive interval
client.connect(THINGSBOARD_HOST, 1883, 60)

client.loop_start()

try:
    while True:
        humidity,temperature = dht.read_retry(dht.DHT22, 4)
        humidity = round(humidity, 2)
        temperature = round(temperature, 2)
        print(u"Temperature: {:g}\u00b0C, Humidity: {:g}%".format(temperature, humidity))
        sensor_data['temperature'] = temperature
        sensor_data['humidity'] = humidity

        # Sending humidity and temperature data to IoT Hub
        client.publish('v1/devices/me/telemetry', json.dumps(sensor_data), 1)

        next_reading += INTERVAL
        sleep_time = next_reading-time.time()
        if sleep_time > 0:
            time.sleep(sleep_time)
except KeyboardInterrupt:
    pass

client.loop_stop()
client.disconnect()

Running the application

This simple command will launch the application:

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python mqtt-dht22.py

Data visualization

Finally, open IoT Hub Web UI. You can access this dashboard by logging in as a tenant administrator.

In case of local installation:

  • login: tenant@thingsboard.org
  • password: tenant

In case of live-demo server:

  • login: your live-demo username (email)
  • password: your live-demo password

See live-demo page for more details how to get your account.

Go to “Devices” section and locate “DHT22 Demo Device”, open device details and switch to “Latest telemetry” tab. If all is configured correctly you should be able to see latest values of “temperature” and “humidity” in the table.

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After, open “Dashboards” section then locate and open “DHT22: Temperature & Humidity Demo Dashboard”. As a result you will see two digital gauges and two time-series charts displaying temperature and humidity level (similar to dashboard image in the introduction).

See also

Browse other samples or explore guides related to main IoT Hub features:

Your feedback

Don’t hesitate to star IoT Hub on github to help us spread the word. If you have any questions about this sample - post it on the issues.

Next steps

  • Getting started guides - These guides provide quick overview of main IoT Hub features. Designed to be completed in 15-30 minutes.