Modbus devices control

Hi all,
I am rather new to the field and I was asked to plan a remote control solution for an industrial machine. The machine is composed of about 6
modbus interfaced devices and needs to be controlled from the internet through a VPN. Do I need a PLC? Or can I just plug all the devices to the COM ports of a normal PC? This is not a harsh industrial environment, so a normal PC would be resistant enough. Can you point me to a software application that would allow me to control modbus devices, store data and so forth? Or do I need to code my own? I have also noticed that many industrial applications are coded in VB. Is there any particular reason for that? I hope you people can englighten me on these matters.
Thanks!
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That would be a lot of com ports on a pc. Can you instead give each of the units an IP address and use modbus over an ethernet or something similar?
You can use a simple PC, given the right programming. I can't point you to the right programming. You may find that standard laboratory packages have some provision for this. You can code your own.
The reason a lot of applications are in VB is that it is easy to learn and work with.
Michael
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Herman Family ha scritto:

Thanks for your reply! Could you point me to some software package? I read about LabView, is it good?
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proclaimed to the world:

Labview is not really for control of industrial machines. Can you tell us more about the application?
Does it run all the time? Is material loaded into the process or machine? How fast is the process?
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Paul M ha scritto:

The machine is supposed to run for a production cycle and then be switched off for a while. Material is loaded in it, about every few months or so. The process should be a couple of hours.
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...
may be that he has modbus-rtu devices ; if he has modbus-over-ethernet then the task is easier, yes.
but there seems to be plenty of modbus implementations around, just look at http://freshmeat.net/ and search for modbus, http://freshmeat.net/projects/libmodbus / might be one good example..

yes, mostly depending on programming skills .. or about any sw house can be contracted to do this kind of work, this is no rocket science.
having one more plc in between might help so that the computer doing the vpn would need to interface only one plc that in turn would speak modbus to rest of the controllers or whatever-modbus-speaking-devices there may be. Having a real plc instead of 6-port serial card is expensive tough but it might pay itself back if the programmer doing the pc-plc -link may do it in modbus-over-ethernet and with single plc ; someone will then need to program that gateway-plc to distribute the configuration items to real conrollers .. requires some thinking and coding anyway..

smells like a holy war coming.. :-)
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Check out www.automatedsolutions.com for a full line of Modbus software components that can be used for Modbus communications between PC and Modbus devices.
Free, fully-functioning 30-day trial versions with powerful example applications are available for download.
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John.John ha scritto:

I've found this on freshmeat. http://www.tuxplc.net/index.php?page talogging-application I think this will work for me. Has anyone had any experiences with it? Thanks to all who answered my posts.
cheers!
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Hello John, I had a similar issue while communicating with a modbus device. I had posted my issue on one of the sites and i got a link to this site whe re they had this HMI/SCADA which allows you to control and monitor your mod bus devices. The SCADA they provide is an easy and its very intuitive which made it more comfortable to use it to monitor the devices. If you would like to see the site is www.Protoconvert.com
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