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Lesson 6 - Wrap-up and Theory

Duration: 45 minutes
Target group: individuals, pairs, or class

Task: Summarize what you have learned, understand the theory of Node-RED and MQTT, and create a small project that ties everything together.

1. Summary of what we have achieved​

In the previous lessons, you:

  • prepared the HARDWARIO TOWER, paired modules, installed firmware,
  • measured various values (temperature, orientation, motion),
  • created graphs and dashboards in Playground,
  • filtered messages, used conditions,
  • controlled the LED strip and other outputs,
  • sent data to the cloud / mobile app and set up notifications.

The purpose of this lesson is to connect all this knowledge, understand how it works “under the hood,” and try it out in one complete project.

2. What is Node-RED​

Node-RED is a visual environment for “flow-based” programming, often used in IoT.

  • It consists of nodes that receive, process, and send messages.
  • Nodes are connected into flows.
  • A message usually has two important parts:
    • topic – subject, category/channel of the message
    • payload – the content of the message, e.g., a number, text, or a JSON object
  • Nodes such as Switch, Change, Function, Debug allow you to modify, filter, or react to messages.
  • Playground uses Node-RED for visually building flows, testing, and interacting with devices.

3. What is MQTT​

MQTT is a messaging protocol, particularly suitable for IoT.

  • Principle publish / subscribe: a device (publisher) sends messages on a certain topic, and other devices (subscribers) subscribe to that topic and receive messages.
  • Difference compared to direct sending: the publisher does not know who will receive the message; the subscriber does not know who sent it.
  • A broker is the server that mediates all messages.
  • Important features:
    • topic hierarchy (e.g., home/room1/temperature)
    • possible QoS levels (Quality of Service) – e.g., “delivered at least once,” “delivered exactly once”
    • retained messages – the last message can be stored and new subscribers will receive it immediately upon subscribing
  • Security: authentication, encrypted communication, careful management of keys / tokens.

4. How everything fits together – architecture​

Here is a simplified diagram of how the message flow works in your projects:

  • The sensor module measures and sends data to HARDWARIO Playground.
  • The HARDWARIO Playground application takes the message received by the Radio Dongle and publishes it via the MQTT protocol.
  • Node-RED processes the message from MQTT: it can filter, react, or forward it again through MQTT.
  • The broker distributes the messages to those interested – applications, output modules, dashboards.
  • Outputs react – LEDs, notifications, etc.

5. Final project​

Try the following project:

Task:

  1. Use a sensor (e.g., temperature) and a motion/orientation detection module.

  2. When the temperature exceeds the set threshold and motion/orientation change is detected, then:

    • the LED strip lights up red,
    • a message is displayed in HARDWARIO Playground,
    • a notification is sent to the mobile app (e.g., the Blynk app).

  3. Show a dashboard with the current temperature, motion/orientation status, and LED strip status.

  4. Draw the message flow: topic(s), payloads, nodes in Node-RED, who publishes / subscribes.

6. Good practices and what to watch out for​

  • Name topics carefully – clarity helps.
  • Don’t send data unnecessarily often – it saves the network and device resources.
  • Security: never share passwords / tokens / keys. Always use strong ones.
  • Monitor what happens in case of outages or errors – what if the sensor doesn’t send, or the MQTT broker is unavailable?

7. Reflection and sharing​

  • What was the hardest part for you? What was the easiest?
  • Which part would you like to explore in more depth (e.g., how MQTT works, security, databases…)?
  • Share your project or message flow with others – explain how you built it.

Summary ✅​

Congratulations! You have completed the entire course. You now know HARDWARIO TOWER not only practically, but also on a theoretical level.
You already have the basics to build your own IoT projects – and you can continue expanding them with your own ideas.