Smart meters setup

Question

I want to monitor my exported solar energy. The solar inverter (L1+N) is already connected to my mains power meter (grid) through a smart meter (SDM630), which in return, transmit RS485 data back to the inverter.

Now, I want to power on a water heater if power is being exported to the grid. The existing smart meter has already used up the RS485 connection, so I have bought another smart meter (SDM230) to be able to export the data to a microcontroller and program it to activate a relay.

My question: Is it OK to just hook up the SDM230 on the existing line (L1) of the SDM630?. In other words; Is it possible to have two smart meters connected in series right after each other?

I will have an electrician do this, but I want to understand if this will work or not.

Sorry for my English, it is not my first language.

my https://github.com/jandrassy/Regulator may be useful for you project — Juraj, Sep 25 '20 at 07:45
RS485 is a bus. but connect the slaves parallel to each other — Juraj, Sep 25 '20 at 07:46
you ask about the power line? why would that be a problem? can't the inverter share the data measured with its meter? — Juraj, Sep 25 '20 at 15:38
Unfortunately I have not found a way to extract data from the inverter. Do you know how to do it? Growatt SPH3600 with Shine WiFi-S. — Brian Petersen, Sep 25 '20 at 18:14

score 2 · Answer 1 · answered Sep 25 '20 at 06:40

2

You might not need to do this (i.e add another smart meter) since the RS485 protocol allows for connecting many devices in serial (check your device specs for the maximum number, it depends on the driver circuit). All RS485 "+" terminals should be conneccted together, and all RS485 "-" terminals together, and the devices can be dasiy chained. You typically put a terminating impedance at final end. So you can have one RS485 to the inverter and another to your microcontroller.

To ensure maximum stability during lightning strikes and ground surge currents, all the connected equipment should have similar transient protection devices such as optocouplers and surge protection, but that is usually the case for well engineered devices.

Otherwise, if you would like to use both meters, if you can send a diagram of how you want to connect it. Voltage has to be connected in parallel.

answered Sep 25 '20 at 06:40

kangaroo8

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1

The inverter and the microcontroller are both masters and the smart meter is slave. I’ve just read that you cannot connect more than one master to a Modbus RTU slave..? – Brian Petersen Sep 25 '20 at 08:34
a microcontroller can surely be programmed as a slave... – Sep 25 '20 at 11:52
I've added a diagram. Please have a look at it. – Brian Petersen Sep 25 '20 at 14:04
The power meter is a slave, so I have to use the microcontroller as a master to communicate with it. – Brian Petersen Sep 25 '20 at 14:12

score 0 · Answer 2 · answered Sep 26 '20 at 19:29

0

So I got it to work. The two smart meters had to be connected in series. The image is a screen dump from html live feed.

answered Sep 26 '20 at 19:29

Brian Petersen

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I think you connected the **current** measurements in series and the **voltage** sensing in parallel. You might want to clarify. You can accept your own answer (after a day or two, I think) to mark the problem as solved. – Transistor Oct 26 '20 at 21:35

Smart meters setup

2 Answers2