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From: YD@localhost.org (YD)
Subject: Re: Avoiding PLCs
Date: Tue, 15 Oct 2002 19:04:23 -0200
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On Mon, 14 Oct 2002 19:31:07 +0100, JohnS wrote:
>"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
>> > 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.
>> 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.
Are you making money off the equipment or the software? Having the
equipment at hand any competent engineer is able to study it and
determine what it needs in the way of control and interlocks and
write a corresponding piece of software. And the software in and of
itself is rather useless without the equipment. In fact I'd consider
the controller and software as part and parcel of the purchase unless
we buy just the machinery and write our own code.
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