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From: firstname.lastname@example.org (bob peterson)
Subject: Re: Avoiding PLCs
Date: 16 Oct 2002 08:32:31 -0700
NNTP-Posting-Date: 16 Oct 2002 15:32:31 GMT
"JohnS" wrote in message news:...
> "bob peterson" 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
> C or
> > > 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
> would be
> > > much appreciated.
> > Most plants need something their own people can maintain. Things
> > programmed in "C" generally don't meet that requirement. Think of it
> > from their perspective. Would you want to be over a barrel to an
> > outside vender who wrote a bunch of custom code you can't fix
> > yourself? Particularly if its a critical system.
> > Its why they want a real PLC, not some kludge together someone came up
> > with that is really good at generating field service revenue.
> OK. Many thanks for all the responses everyone. It's not just about trying
> to generate service calls tho. Don't think we manage to make much money on
> that. But apart from the amount of effort that goes into rewriting code and
> redesigning systems for each PLC, there is also a question of IP in the
> 'know how' of how systems work to control one's own equipment. Giving the
> code away for the PLC makes it invitingly easy for a customer to get copies
> made elsewhere. Anyway thanks again.
Most PLC code is easily translatable from one brand of PLC to another.
This is a common issue with system integrators all the time.
OTOH-if your main issue is to prevent the end user from using or
modifying the code, I think you are out of luck. The reason they want
it in a PLC is for that exact reason. The likelihood is that nothing
you have in your code is really all that big of a deal, no doubt any
competant PLc programmer could easily produce a working program from
an accurate description of how the stuff works.
Most of the supposedly "propriatary" PLC code I have seen is
laughable. Much of it is just run of the mill control logic.
If you have some algorithms that are legitmately trade secrets, insist
the end user sign a secrecy agreement before releasing the code to
them. OTOH-they may just tell you to go scratch, as its likely they
will be able to find an alternate vender who will sell them what they
want without so much hassle.
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