Node-RED: Lecture 3 – Example 3.6 Using an mqtt output node to test the flow

As an alternative to using the HiveMQ test page to publish on the MQTT topic, we can configure an mqtt output node. This is the mirror of the mqtt input node and allows you to configure an MQTT service and the topic you are publishing on. You can then send the node messages with the exact same JSON string we’ve been sending via the HiveMQ test page.… Read the rest

Node-RED: Lecture 3 – Example 3.5 Scaling input with the range node

When dealing with real world input from sensors and other devices, an ability to scale input data is often required. Node-RED provides the scale node to support this and allows you to scale (linearly) an input value.

This example continues our theme of manipulating MQTT input data. If you aren’t familiar with how to setup an MQTT node then refer to Example 3.1.… Read the rest

Node-RED: Lecture 3 – Example 3.4 Using the rbe (report by exception) node

In this example, you’ll continue your message analysis theme and add nodes to the part of the flow that is used when you determine that the flow should be analyzed. You’ll be using the rbe (report by exception) node which only passes on data if it has changed. You can set it to examine a message payload and either block until a message changes (rbe mode) or when a messages changes by a specified amount (deadband mode).… Read the rest

Node-RED: Lecture 3 – Example 3.3 Using a change node to change or manipulate a message payload

Another useful node is the change node, which will allow you to change a message payload or add new properties. You can use this node to affect the properties in a message, either by changing existing ones, deleting them or adding new properties.

In this example, you’ll continue with your MQTT theme and see how, now that you have successfully ‘switched’ the message flow based on the incoming MQTT message, you can add a new message property msg.payload.note.… Read the rest

Node-RED: Lecture 3 – Example 3.2 Using the switch node to handle a JSON object

This example continues to use the MQTT node we setup in Example 3.1. If you aren’t following these examples sequentially you may want to review example 3.1 as it shows how to use the free MQTT broker, HiveMQ which is needed for the MQTT node.

One of the nice features of having a JSON object is that you can easily act on its properties.… Read the rest

Node-RED: Lecture 3 – Example 3.1: Receiving JSON via an MQTT message

This example builds on the mqtt node, which provides a convenient way to take input from an MQTT broker. For those not familiar with MQTT, it is an example of a publish/subscribe system (usually shortened to pub/sub system) which lets sensors publish updates that all delivered to client subscribed to that sensor.… Read the rest

Node-RED: Lecture 8 Advanced flows with Node-RED

 

This lecture is a set of links to advanced tutorials we have written. These include:

  • Tutorial: Using FRED (Cloud Node-RED) to build an AI chatbot using IBM Watson
  • Tutorial: Using FRED (Cloud Node-RED) with the GE Predix Timeseries Microservice
  • Tutorial: Using OPC-UA with FRED (Cloud Node-RED)
  • Monitor a Pi Zero hosted security camera with Node-RED & MQTT
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Node-RED: Lecture 3 – Basic nodes and flows

In this lecture you will get to see a few of the more commonly used nodes and build on some of the things you learnt in previous lectures. You’ll start off with a series of examples based around the popular MQTT protocol that shows how to wire together a set of basic but very useful message processing nodes.… Read the rest

In this lecture you will get to see a few of the more commonly used nodes and build on some of the things you learnt in previous lectures. You’ll start off with a series of examples based around the popular MQTT protocol that shows how to wire together a set of basic but very useful message processing nodes.… Read the rest