OpenEnergyMonitor Community

emonTx & LoRa

Hi all, I wondered if there was a known implementation of using LoRa for either emonTx (or emonPi) using LoRa modules to transmit sensor readings over longer distances. I’ve found a peppering of older posts relating to Lora over the past four years but involve v. specific situations or more complex/advanced LoRaWan projects.

I have a particular use case where our village would like to obtain and publish energy/solar data from multiple, remote community buildings within 300m radius. A powered emonTx + RFM95 combination would seem perfect for the job but checking if there was a working example of an elegant approach somewhere before i embark on this adventure (with inevitably less elegant code). I understand the emonTx RFM69 processes things differently and uses different libraries so not an obvious solution to switch out?

The receiving end seems more straightforward being a Lora receiver converting to MQTT or posting to emonCMS directly.

Grateful for any thoughts, ideas, misadventures shared. Ta

Hello @thedawnbefore it’s not something that we have developed yet and I don’t think I’ve seen anything else on here that would provide a working example. I’d be interested in hearing how you get on though, would it require some clever processing of the emontx data to reduce the data rate? Perhaps just sending kWh elapsed at longer intervals rather than 10s power data?

Thanks @TrystanLea, that’s a helpful steer. I’m still diving into LoRa basics but understand the transmission rate would need to be reduced considerably over a conventional OEM setup.

I had imagined transmission every 5 minutes might be sufficient (even longer) as the purpose is more for community information, engagement and evaluating long-term ROI of some grant-funded solar projects (and eventual EVSE frequency/occupancy) but would be grateful for any thoughts re: transmission rate. I will probably start with this issue.

Yes that sounds good, I have through that for applications like this maybe just recording half hourly kWh consumption would be sufficient, it would be enough for evaluation against variable tariffs. It would be really neat to be able to record a full history of half hourly kWh consumption on some form of memory attached or integrated in a modified emontx like hardware, together with a local real-time clock for accurate allocation. That data could then be uploaded via WiFi or something like LoraWan. It would be particularly useful for projects that we are involved with such as EnergyLocal, but being already stretched with quite a few different things, its’ not something we’ve got on to working on yet.

If you’re going to use emonLibCM, that has been tested, as the documentation states, up to a reporting period of 5 mins. For periods greater than that, the concern would be overflow of the variables that accumulate the values as part of the averaging process, which clearly depends on the power levels experienced.

You might be interested in this but when you read it carefully, a little bit of cheating was involved :wink:

I’d be wary of using any library with emonLibCM, because you might find it steals processing time and prevents emonLibCM from sampling correctly - this is why, with the RFM69CW that has a data buffer on-board, we can’t use the ‘classic’ JeeLib (which does not use the buffer). If you have 3-phase supplies, it’s almost guaranteed that the 3-phase sketch will lose lock unless you can fill the data buffer at your leisure and hand off actual transmission of the message to the radio module itself.

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Interesting idea, agree half hourly would likely be sufficient.

Re. EnergyLocal… what a brilliant initiative. I’ll certainly pass this on

Thanks for the heads up on this, well noted.