third party emonTx compatible hardware


We design a range of products that are widely used in electric vehicle charging systems. One product - The Electric Vehicle Supply Equipment Protocol Controller ("EPC") - is used to control and monitor the charge rate for electric cars.

The EPC is sold direct to OEM's but is also made available to end users at low cost by the UK Charity Zero Carbon World;

Here's an example of the EPC being used by electric car drivers to build their own Charging Station during one of the ZCW "EVSE Build Days";

We are developing a new version of the EPC hardware and a customer has suggested that we emulate the emonTx functionality to allow easy integration between OpenEnergyMonitor systems and electric car charging systems. Personally I think this would be a very useful addition because I'm currently controlling my electric car charging rate manually to match my solar PV output.

We do not intend to use any of the emonTx hardware or software but simply emulate the current and voltage measurements and provide a compatible RF interface so that the EPC appears as another node on a OpenEnergyMonitor system. We would also propose the development of OpenEnergyMonitor software enhancements that enable control of the EPC from solar systems, etc.

The EPC is not open source and I would be interested in the communities thoughts on our proposals to add third party commercial hardware that's compatible with OpenEnergyMonitor emonTx.

Many thanks...

glyn.hudson's picture

Re: third party emonTx compatible hardware

Hi Kevin,

Thanks for getting in touch. It would be fantastic for OpenEnergyMonitor project to be involved with EV's, I love EV's and very much look forward to when I can afford one! 

I've just watched the video you posted above and realised that we have met before! It was in a very wet farm yard in Cwn Llan, North Wales at a National Trust Hydro day, here's some photos I took: You had your nice Tesla there and explained the work you were doing making charging stations available, great stuff! 

With regard to integrating energy monitoring into EPC hardware it would be fantastic if you could do this in a way which would be compatible with the OpenEnergyMonitor system. We would be most happy for you to take elements from the emonTx design and emulate the voltage and current reading. Obviously we believe open-source hardware is a better way of doing things but I can understand not all companies are willing to go down the open-source route. However maybe elements of the EPC could be open-source like the energy monitoring part? I believe member of the OpenEnergyMonitor community would be much more included to use, work with and develop with the EPC if it was open-source or partly open-source. I believe the positives and benefits that stem from open-souce hardware outweigh the potential negatives. 

Thinking practically; one way energy monitoring could be integrated into the EPC in an open-source way and provide a compatible RF interface is for you to use the RFu328 module that we use in the emonTx V3, this module is made in the UK by Ciseco and contains an ATmega328 microcontroller (same as used in Arduino Uno) and an RF module which could be either the RFM12B which we use now in all OpenEnergyMonitor units or the Ciseco SRF module which is another popular RF module and one which we might start using more in the future as Ciseco gets the module through FCC certification. This RFu328 module combined with a few additional energy monitoring components (capacitors and resistors) would provide energy monitoring functionality. 

The emonTx V3 hardwre design available on solderpad:

Looking forward to hearing your thoughts. 


dod's picture

Re: third party emonTx compatible hardware

This is excellent, given the rolec units have a din mount epc (probaby made by kevin anyway) it would be a straight swap of epc, then utilising the Rpi it would be really cool to control charge rates via the rfm12b and even with glcd

This would mean I could loose bunch of wiring and the pv would control the charge rate in a much neater solution.

I still love my open evse, but the epc and contactors is a nice neat safer solution.

Can we have one next week please Kevin :-)

Well done both !

Wxll's picture

Re: third party emonTx compatible hardware

There is another opensource project for EVSE's as well which I supported (provided a full set of OpenEnergyMonitor so it could be tested by the developer)

It's using the RFM12B signals send out by the OpenEnergyMonitor box and uses that to adjust the charging rate of a KeContact P20 3 phase 32A home EVSE charger. It can run on the same Pi as the emoncms is running.





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