First Post - Advice required for large scale

Hi all,

I have setup a self-hosted Emoncms this evening with view to building my own monitoring system. I work for a Solar PV company as Ops & Comms Technician, mainly installing fibre optic comms, satellite broadband and monitoring systems. 

Our PV installs are mainly large scale farms between 3MWp and 35MWp. We have various monitoring solutions but not one good solid solution so my plan is to try and build a system with OpenEnergyMonitor. My concerns are as follows:

1. I am not a coder, will this be too complicated?

2. Wireless will not work for me, our monitoring panels can be 30 metres from the nearest sensors and located within containerised inverter cabins. Is there any hardware available with hard wired inputs, or can ADAM and similar devices be used?

3. I need to provide DC Voltage and DC Current for each inverter module, many of our inverters contain 9 modules and I need to drill down to string level. String Combiner Boxes all have RS485 comms boards installed.

4. I also have to provide data from a pyranometer, a panel temp sensor, an ambient temp sensor and an anemometer.

5. Final requirement, I need to provide data from the generation meters. There is normally a main meter and a check meter.

Can anyone please give me some advice? I really like the look and flexibility of Emoncms and would love to build a large monitoring system with it. I just need to know if its possible.

Many thanks in advance,



Robert Wall's picture

Re: First Post - Advice required for large scale

Welcome, Bret.

I'll try to answer some of those points.

1. Some knowledge of coding, and IT systems will be very useful. That you have set up your own emonCMS is probably a good indication that you won't struggle too much. There's plenty of help in the forums here when you need it.

2. You need to be clear where the distinction is between the hardware of the emonTx and emonBase, and the software of emonCMS. EmonCMS can accept data from anywhere via any transmission medium, normally it arrives by Ethernet to the server where emonCMS is running.  I think that opens the possibility of using Ethernet between your monitoring points and the inverter modules. You can use anything you like to feed the packets into the Ethernet provided that you can specify the content - there are examples in emonCMS help of what emonCMS expects. I'm not familiar with ADAM so I can't comment on that.

3 - 5. Those requirements can't be met with our standard emonTx, which was (in simple terms) designed for the UK domestic market. Putting my Systems Engineer's hat back on, I think you're looking at - depending on the quantities - getting a custom-designed front end that is exactly tailored for your needs. You don't say exactly how much data there is at RS485 level, or what the interfaces to the other instrumentation is, so I can't judge what front-end processing might be needed, but my feeling is you'll need some moderately powerful processing in each modular container.

bretwhitcombe's picture

Re: First Post - Advice required for large scale

Hi Robert,

Thanks very much for your reply, and I really appreciate your input. I did work in IT for 17 years before starting my career in solar PV last year so I'm very comfortable with hardware and the web hosting element, it's just the specific coding. I can see what you mean about hardware, any data logger particularly those with an Ethernet or Modbus TCP communication should work. It is just deciphering the captured data packets that would need some coding experience I guess.

The ADAM devices are used by our current monitoring company to receive RS485 signals from all of the sensors I listed above, and then convert it into Modbus TCP. Even the generation meters provide their data by RS485 so we seem to have a fairly standard data collection method across the entire platform.

After speaking with our Head of Engineering he would like to use a Raspberry PI in all of our inverters as the main processing component which for us cuts out a huge amount of self-consumption meaning less design and material to power the auxiliary equipment, lower operating temperatures than conventional PC's and a solution we can manufacture in-house. I'm extremely enthusiastic about designing and building a system and after our recent delivery of equipment from overseas was badly damaged by the carrier we have a greater need to make this work.


It would also be nice to develop EmonCMS in corporate colours with our logo.


Many thanks,


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