Modbus Data Cable - What can you recommend

Hello all.

I’m about to start my emon journey and planning out a few things to try before jumping in big time.

I’m running Home Assistant on a NUC which has meant an old RaspberryPi 3 is free for repurposing.

I’ve got the base install done by flashing onto a 128GB SD card, got an account set up and feeling a bit daunted with what I see. I’ve established an integration in Home Assistant but there’re no feeds into HA yet as I have nothing setup/connected onto the emonSD.

However, I’m also completely redoing my distribution board “zone” to get ready for Solar and battery, and am needing replace my CU with a nice shiny new one. I plan to have an SDM120 Modbus MID 45A on each top level circuit and an SDM230 at the “front” along side a SPD, all daisy chained together and terminating at a RS485 to USB adaptor which is plugged into the Pi.

But before I splash out on about 10 SDM120s, I’m wanting to test things with the SDM230 first, and I’ll need a data cable.

I know I’ll need an insulated single twisted pair cable. A bit of googling suggests I should go for the Belden 3105A Data Cable. But wanted to ask any recommendations from the community first, as that cable is not cheap. Would some Shielded Cat5e be suitable, and leverage one to the pairs (and ground wire, of course)? Say the O/O-W pair?

Would appreciate some thoughts.

Thanks in advance.

The important thing is that the Inputs are created automatically if you send data to emoncms (via various routes). You then need to create processes to save that data into Feeds.

Have a look at the RFM (Really Fine Manual) and see if that helps

Can’t help on suitable cable - sorry.

Thanks very much of this @borpin - Really appreciated.

I’ve pulled the trigger on a length of CAT5e (shielded) and will see how that goes. Should be OK - it’s not as if I’m streaming critical medical data or needing telemetry accuarcy with near zero latency to land a rocket! :slight_smile:

Thanks again.

@borpin . Just out of interest, might there be an interfacer for Solis hybrid inverters? :slight_smile:

Thanks again.

Did you search the Forum for Solis - there are a number of threads.

I’ll have a look, thanks.


You will be fine with the cat5 cable I am using standard telephone twisted pair to retrieve modbus data from my Sofar ME3000 and it has no problems (there is not even a ground just A and B )