From: firstname.lastname@example.org (Spehro Pefhany)
Subject: Re: Avoiding PLCs
Date: 12 Oct 2002 22:41:13 -0700
NNTP-Posting-Date: 13 Oct 2002 05:41:13 GMT
"JohnS" wrote in message news:...
> We have run into a problem, hope someone here can make a helpful
> suggestion! We have a digital control system which is fairly easily built
> 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 avoid
> this I am looking for modular electronic systems that we can program in C or
> whatever so we can avoid using a PLC, but still have the flexibility to add
> I/O etc as required.
> We could design from the ground up, but there must be suitable systems out
> there, ideally with CE and UL approval!. Any pointers to possibles would be
> 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.