Computer Interfacing
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Connectivity between my Sunny Box Inverter and my PC

Is there a difference between RS485 and Ethernet


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Author Message

Jan 22, 2008 2:17 am

Hi All, Smile

I want to connect a Sunny Boy Inverter (Solar Grid Connect System)to my PC so that I can monitor performance and collect data for trending. I already have an Ethernet LAN with 10/100/1000 switch and would prefer to hook the Inverter into it and keep things as simple as possible. The Inverter and PC are within 12 meters of each other. The Supplier of the Inverter tells me that RS485 and Ethernet are the same. Is this true or will I need a converter to make it work?

Thanks in advance.........S
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Joined: 13 Mar 2007
Posts: 145
Location: Netherlands and Kazakhstan

Jan 22, 2008 10:19 am

Hi StewK,

First of all Welcome to the Computer interfacing Forums!

In general RS485 and ethernet are not the same thing. RS485 is a serial communication standard where two or more devices may communicate over one "time-sharing" communication line, where ethernet communication always takes place between a maximum of two devices over two separate lines. There are also differences in allowed communication speed, voltage levels, the contents of the data packages etc.

But sometimes the word ethernet is used for multiple things. It can not only be used for the communication protocol, but also for the cable itself. Although often referenced as UTP cable, people may call it ethernet cable because that is the main use or it. Maybe the supplier wanted to say that you can use ethernet cable for the connection between the Sunny Boy Inverter and your PC. That is perfectly possible if you solder the right connectors on both sides, although you can't route the data through your ethernet LAN switch. The cable has to be connected directly to a communication port in your PC.

I took a look at the Sunny Boy website, and found the following communication poster. It shows which communication models are supported on each device they have. For routing over your 10/100/1000 LAN switch you need a device that supports the TCP/IP protocol, but unfortunately the Sunny Boy models only support RS485 and wireless communications.

At the bottom of the page is the Sunny Data Control Software which supports three communication methods, i.e. TCP/IP, USB and RS485. In small print it says "RS485 may require RS485/RS232 protocol converter". This is a little bit misleading. Except for some special Industrial PCs, not a single computer is standard equipped with an RS485 port, so they should rather say "RS485 almost always requires a protocol converter". So if you want to connect with the Sunny Boy over RS485, you will need an extra converter to hook it up onto your computer.

Be sure that you have a computer with an external RS232 port. Most modern computers won't have them and the RS485 to RS232 converter will be worthless. You may also buy an internal RS485 PCI card for your PC. In the end I think this will be cheaper because such a card doesn't need an external power supply.

Last edited by lammert on Jan 22, 2008 11:07 am; edited 1 time in total

Jan 22, 2008 10:49 am

Thanks Lammert, excellent answer. Not really the one I wanted to hear, but you have saved me a lot of grief and unwanted expense........S Wink

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