adccommunitymod (AutomationDirect) asked a question.
Created Date: February 07,2012
Created By: Dbutler
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Hello, I have a GS1 AC Drive that I'm going to use to drive a fan, and I would like to have it fully automated and be able to send commands to it via the RS485 interface, preferably with a LabView UI on a PC. I purchased the GS1 and can control it via the front panel, but I also purchased USB-485M hoping that this would give me the access I needed to send commands to the GS1. When reading through the manual I see a lot of information about using Click PLCs and DirectLOGIC Modbus stuff, but I was just hoping to find a simple programmers reference guide that lays out the commands required to change the parameters on the GS1 directly out of my USB-485M port. Is it possible to control the GS1 this way without using a PLC? If so, how would I be able to change the parameters directly from sending (HEX?) commands down the port? I 've browsed through examples and FAQ and not finding what I'm looking for. Thank you!
Created Date: February 07,2012
Created by: bcarlton
The commands are using Modbus. Read more about the protocol at www.modbus.org
Created Date: February 07,2012
Created by: Dbutler
thanks bcarlton, taking a look at the protocol now. This looks like a lot to digest, and I might have to take a few runs to figure out how this modbus stuff relates to controlling the GS1 AC Drive.
So, in a nutshell, can I control this GS1 from my laptop using the USB to 485 adapter and hyperterminal or LabView, or do I need to purchase more hardware and software tools to do that?
Created Date: February 07,2012
Created by: bcarlton
It would be a software tool and there are some free ones for Modbus.
Simply Modbus has a 'master ' version you can play with but it is limited until you buy it. You can at least see what's going on. After 4 requests you'll have to restart.
Created Date: February 08,2012
Created by: Dbutler
So are you saying that my hardware setup won't work?
PC --> USB-485M --> GS1
http://i260.photobucket.com/albums/ii7/deater1/Drawing1.jpg
I was hoping I could use this setup to send simple commands to the GS1 to change parameters.
Created Date: February 08,2012
Created by: bcarlton
I said nothing about your hardware setup. It probably will be fine as long as the pinouts are correct and the port setups match. I just mentioned the protocol which is used for sending commands and receiving status.
Created Date: February 08,2012
Created by: Dbutler
If this setup won't work, then what is the simplest way to drive this GS1 with my PC? It looks like the Click PLC may be a good option, but what is the recommended setup and will it come with all of the software and cables needed?
Created Date: February 08,2012
Created by: bcarlton
The only item I don't know about is - will the 'LabView UI on a PC ' use Modbus to send and receive information?
Created Date: February 08,2012
Created by: Dbutler
LabView can access COM ports with ease, and with the USB-485M device (purchased from automationdirect), it gives me access to the port as a virtual COM, similar to the USB to RS232 devices that are made at FTDI ( www.ftdichip.com ). I was hoping for something simple like a list of commands to send to the GS1 with this USB to RS485 interface.
I 've looked through the modbus link you provided and it hasn't clicked for me just yet. I'm not sure at this point how the modbus comes in to play. What are the most important parts of the modbus that I need to know in order to interface with my GS1 AC Driver?
Thank you :)
Created Date: February 08,2012
Created by: Do-more PE
Let me step in and see if I can explain this in a simple manner.
There are three parts to communications to a device. Hardware, communications specification and protocol.
Lets say we are making a call. We want the call to go to China. we pick up the phone (hardware), dial the number (communications specification), and someone answers (protocol). If the person answering the phone does not speak the same language that you do (protocol) then communications will never be established.
So what you have is Labview on a PC and a GS drive. For arguments sake we will call this hardware.
You have an RS-485 adapter. RS-485 is a communications specification.
What you are missing is the protocol. In this case the needed protocol is MODBUS RTU. You can get a MODBUS RTU driver for LabView, get an OPC server that translates between OPC and MODBUS RTU (Labview would talk to the OPC server which would then translate the protocol to MODBUS RTU), or you could write you own driver (not recommended, it's like doing self dentistry.)
So you either need to find a MODBUS RTU driver for Labview or find some OPC server software that will do MODBUS RTU and install that on the computer with Labview and use that as a wedge between Labview and the GS drive.
Created Date: February 08,2012
Created by: Dbutler
Thank you so much ADC App Assist, I found a LabView MODBUS Driver here:
http://sine.ni.com/nips/cds/view/p/lang/en/nid/201711
I will get that installed and try it out. Thanks for clearing that up for me.