I have experience with the SDM120c. I ordered another from China with Aliexpress:
http://www.aliexpress.com/item/SDM120C- ... 29725.html
Also sdm120 can 'work to 240 Volt
- Nominal Voltage(Un): 230V AC
Operational Voltage : 176~276V AC
While DRS-205C:
- output Voltage:120V/ 230V
There is also the SDM220Modbus but I have no experience.
I used the SDM120c with Raspberry with a USB / RS485 like this:
http://www.ebay.com/itm/New-USB-to-RS48 ... 58bb354d7f
I installed Nodejs and interrogate the SDM120c from Raspberry with the API:
https://github.com/gianfrdp/SDM120C
I write a little html page which send (socket.io) readings at intervals of 2 seconds.
I'm recording all the data every two minutes on a Firebase DB and writing a nodejs app to analyze them!
The works is in progress!!
I'd like to read the second sdm120c via wifi to connect for example to an inverter grid tie that reads energy production, or
to another user far from the raspy I want to monitor.
You could use to monitor the consumption of several apartments in a residence, etc.
Too bad I do not know LUA, actually I have not updated the firmware esp8266 for testing (do not have much time available).
I hope to do some testing during the holidays, but where I live, the sea is very nice !!!!
I'm happy someone else and interested in making this small project and share the software free to all!
Do you think that the electrical schematic that I drew, it can work?