From: "Tom Needham"
Subject: Re: Avoiding PLCs
Organization: The Node of Last Resort
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Date: Sun, 13 Oct 2002 11:07:58 -0400
NNTP-Posting-Date: Sun, 13 Oct 2002 10:12:21 CDT
I am currently exploring the same avenue.
You will have some trouble selling a custom animal to some customers,
but depending on your application, it may be possible to use the "black box"
to do the "magic" portion of the control, with the PLC in charge of the
and basic I/O control.
This will simplify the PLC portion to the simple tasks, which will reduce
of code re-write when using the customer specified PLC.
The "black box" could be common across all PLC platforms.
It will also keep the "magic" code in a compiled format that will be hard
the competition to copy, or keep the renegade maintenance dude from
"tweaking" critical code.
I have decided on Z-world embedded controllers to start with.
Just my $.02
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"Spehro Pefhany" wrote in message
> "JohnS" wrote in message
> > We have run into a problem, hope someone here can make a helpful
> > suggestion! We have a digital control system which is fairly easily
> > using a plc. (Lots of interlock logic, timers, 4/20 mA circuits, 4 line
> > display, etc) Unfortunately every customer then seems to insist that we
> > build using the make of controller already in use by them. In order to
> > this I am looking for modular electronic systems that we can program in
> > whatever so we can avoid using a PLC, but still have the flexibility to
> > I/O etc as required.
> > We could design from the ground up, but there must be suitable systems
> > there, ideally with CE and UL approval!. Any pointers to possibles
> > much appreciated.
> Other than PC-based systems (which would be hard to recommend for a
> variety of reasons), I don't really think there *is* much out there.
> On the PC platform (various packaging, but all really PCs underneath)
> you have to worry about the availability of IO's and service bits off
> into the future. I think you will have little success (for good reason)
> convincing your customer to go with something other than what they are
> using on large projects. On small projects, you may well be able to talk
> them into a micro-PLC because of the low cost of both the controller and
> the software you will develop for them. From a business POV it's probably
> best to concentrate on the major brands of PLC and/or those your major
> prospects and customers use.
> The only ray of hope I can offer is that you may be able to IEC-61131
> compatible controllers, but selling that to your customer base is
> another thing. See: http://www.plcopen.org
> I've cross-posted the reply to sci.engr.control and
> alt.engineering.electrical as it's appropriate in those newsgroups.
> Best regards,
> Spehro Pefhany