After getting my heating and power usage/generation into EmonCMS I wanted to start pulling other sources of data into EmonCMS, so I started looking for a more expandable method to bring multiple sources of data into EmonCMS.

Open Energy Monitor, the folks behind EmonCMS, have recently started looking at Node-RED so I decided to also have a look at this.

It is also getting colder and I wanted to get a bit more information on the operation of my OpenTRV board that has been sitting underused since the spring when I installed it on the radiator in the office.

Getting Started

I won’t go into detail about downloading/installing Node-RED as there are good instructions in the Node-RED documentation and the Node-RED EmonCMS Node blog post includes instructions on installing the EmonCMS specific components.

First of all we need to get the data from the OpenTRV devices. In my setup this is via a USB to TTL adapter connected to the serial data port on the OpenTRV.

That is it for the hardware, but how do we get the data into Node-RED? For this we need the Serial node.

Setting Up the Serial Connection

Drag one of these nodes to the workspace and double click to open the settings. You’ll need to configure:

  • Serial Port: The COM port your USB-TTL adapter is connected to
  • Baud Rate: Typically 4800 for OpenTRV devices
  • Data Bits: 8
  • Parity: None
  • Stop Bits: 1

Data Processing

The OpenTRV devices output status information in a structured format that includes temperature readings, valve positions, and other sensor data. Node-RED provides excellent tools for parsing this data:

Switch Node

Use a switch node to route different types of messages based on content patterns.

Function Nodes

Create custom JavaScript functions to parse the OpenTRV status strings and extract meaningful data points.

Debug Nodes

Essential for monitoring data flow and troubleshooting your Node-RED flows.

Integration with EmonCMS

Once you have the data parsed and formatted, the EmonCMS node makes it simple to send the data to your EmonCMS instance:

  1. Install the EmonCMS Node: Use the Node-RED palette manager
  2. Configure Connection: Set your EmonCMS server URL and API key
  3. Map Data: Ensure your parsed data matches the expected EmonCMS format

Benefits of Node-RED

Using Node-RED for IoT data integration provides several advantages:

  • Visual Programming: Flow-based programming makes complex data processing easier to understand
  • Extensive Library: Thousands of contributed nodes for different protocols and services
  • Real-time Processing: Live data transformation and routing
  • Easy Debugging: Built-in debugging tools and message inspection
  • Flexible Deployment: Can run on Raspberry Pi, local servers, or cloud platforms

Next Steps

This initial experiment with Node-RED has opened up many possibilities for expanding my home automation and monitoring system. Future posts will explore:

  • Handling multiple OpenTRV nodes
  • Adding other sensor data sources
  • Creating custom dashboard interfaces
  • Advanced data processing and alerting

Node-RED proves to be an excellent tool for bridging different IoT protocols and services, making it much easier to create comprehensive monitoring and automation systems.