Sending MQTT State as Number

Hello everyone! I’ve been working on integrating my home energy monitoring system with MQTT, and I’ve encountered an interesting challenge. I’m sending the current power consumption of my home via MQTT to an openHAB broker, but it seems like the value is being received as a string instead of a number. This is causing some issues with my rules and visualizations, as they expect a numerical value. I was wondering if anyone has encountered this before and how they resolved it.

First, let me explain my setup. I have a Raspberry Pi running a script that reads the power consumption from my smart meter and publishes it to an MQTT topic. The data is being sent as a JSON payload, which includes the current power usage in watts. On the openHAB side, I have an MQTT binding configured to listen to this topic and update a number item accordingly.

However, when I check the item in openHAB, it’s showing up as a string instead of a number. This means that any rules or transformations that rely on numerical operations aren’t working as expected. For example, I have a rule that triggers an alert if the power usage exceeds a certain threshold, but it’s not activating because the value is treated as text.

I’ve tried a few things to resolve this. First, I checked the MQTT payload to ensure that the value is indeed a number and not a string. Using an MQTT client, I can see that the payload is correctly formatted with a numerical value. Next, I looked into the openHAB MQTT binding configuration to see if there’s an option to specify the data type of the incoming message. Unfortunately, it seems like the binding automatically infers the type based on the payload, which in this case is being interpreted as a string.

After some research, I found that one possible solution is to modify the state transformation in the channel configuration to explicitly cast the received value to a number. I updated my channel definition to include a transformation that converts the string to a number using a simple rule. Here’s how I did it:

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Type number : powerUsage [ stateTransformation=“JSONPATH:$.watts”, transformationPattern=“NUMBER” ]

This transformation ensures that the value is treated as a number in openHAB. I also made sure to restart the MQTT binding after making the changes to apply the new configuration.

Since implementing this change, the power usage value is now correctly recognized as a number, and my rules are functioning as intended. It’s a relief to have this issue resolved, and I can now focus on optimizing my energy monitoring setup further.

I’d love to hear if anyone else has dealt with similar issues or has alternative approaches to ensure data types are correctly handled in MQTT integrations. Sharing experiences like this really helps the community grow and learn together!

Best regards,
[Your Name]