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When are PLC manufacturers going to catch up with the rest of the microprocessor based technology community. I am continually frustrated when having to use and program PLCs.
Of course every PLC manufacturer thinks that their PLC is the only way forward (typical Engineers outlook). Every PLC manufacturer runs its own OS, programmed with it's own programming software and development tools (which generally costs as much as the PLC itself), used only its specially made and expensive modules/cards and generally communicate by its own special comms protocol (although comms issues are improving).
Is it not time the PLC manufactures get together to develop a standardised and dare I say open architecture, similar to what IBM did with the PC. Something based on a PC type processor so costs are kept down and speed up due to the PC market. Something with an expansion bus similar to the PCI bus to which I/O, comms etc, cards from any manufacturer can be plugged into. Something that is fast, ie. has a scan rate of more than 10ms (which realistically, in microprocessor terms it 'ken slow). And something where an increase in just only tens of kilobytes of memory doesn't cost hundreds of extra dollars, why can't I have hundreds of MB of memory on my PLC, long gone are the days where memory was a significent cost of a computer. When will PLCs catch up.
And lets not start carrying on with the old excuse of the reliability of a PC compared to a PLC. We are not talking about a PC here, it is not running Windows XP with a million background tasks and applications, one of which may or may not crash the machine. As far as the hardware goes, it will be no less reliable that a normal PLC, this machine is just based on a different architecture, an open one. Its job will still be to run a single program to control stuff, the difference being is I can run the same program on a machine manufactured by Siemens, AB, GE, Modicon etc.
A particularly fustrating issue is that while a particular PLC may provide all the features one might need in a PLC, the programmer is stuck using the manufactures programming software to programming (which is generally crap). A good point in case is the Quantum PLC, while a reasonably good PLC, the programming software is hopeless.
With an open architecture, as for the PC, a programmer may choose to use any of a variety of software to develop a program. This would lead to some much better development enviroments. We would also be free to program in languages other than ladder (if the end user electrician is capable of reading it!), maybe even a real OO language.
With all this in mind, I see no reason for the PLC manufacturers to be nervous or apprihensive, afterall they will still be manufacturing PLCs and PLC components. And as with PCs, the open and standardised architecture doesn't limit development of units with new and improved features, it will more likely encorrage it. The manufacture of choice will still be therefore based on features, cost, reliability etc. Nothing will change other than a bit of healthy competition.
I'm just a mere Control Engineer and so can do nothing more than write snotty letters about what I would like to see done. I do however hope PLC manufactures will soon see the merits in what I am proposing (which is by no means a new idea), and take it upon their collective selves to co-opererate.
I think they are all a long way off the mark at the moment and it doesn't stop at the PLC level. The current trend continues through to SCADA packages although that is entierly another topic.
When will the PLC catch up, I think it is about time!!!
Doug Panacea
Controls Engineer
Melbourne Australia
Of course every PLC manufacturer thinks that their PLC is the only way forward (typical Engineers outlook). Every PLC manufacturer runs its own OS, programmed with it's own programming software and development tools (which generally costs as much as the PLC itself), used only its specially made and expensive modules/cards and generally communicate by its own special comms protocol (although comms issues are improving).
Is it not time the PLC manufactures get together to develop a standardised and dare I say open architecture, similar to what IBM did with the PC. Something based on a PC type processor so costs are kept down and speed up due to the PC market. Something with an expansion bus similar to the PCI bus to which I/O, comms etc, cards from any manufacturer can be plugged into. Something that is fast, ie. has a scan rate of more than 10ms (which realistically, in microprocessor terms it 'ken slow). And something where an increase in just only tens of kilobytes of memory doesn't cost hundreds of extra dollars, why can't I have hundreds of MB of memory on my PLC, long gone are the days where memory was a significent cost of a computer. When will PLCs catch up.
And lets not start carrying on with the old excuse of the reliability of a PC compared to a PLC. We are not talking about a PC here, it is not running Windows XP with a million background tasks and applications, one of which may or may not crash the machine. As far as the hardware goes, it will be no less reliable that a normal PLC, this machine is just based on a different architecture, an open one. Its job will still be to run a single program to control stuff, the difference being is I can run the same program on a machine manufactured by Siemens, AB, GE, Modicon etc.
A particularly fustrating issue is that while a particular PLC may provide all the features one might need in a PLC, the programmer is stuck using the manufactures programming software to programming (which is generally crap). A good point in case is the Quantum PLC, while a reasonably good PLC, the programming software is hopeless.
With an open architecture, as for the PC, a programmer may choose to use any of a variety of software to develop a program. This would lead to some much better development enviroments. We would also be free to program in languages other than ladder (if the end user electrician is capable of reading it!), maybe even a real OO language.
With all this in mind, I see no reason for the PLC manufacturers to be nervous or apprihensive, afterall they will still be manufacturing PLCs and PLC components. And as with PCs, the open and standardised architecture doesn't limit development of units with new and improved features, it will more likely encorrage it. The manufacture of choice will still be therefore based on features, cost, reliability etc. Nothing will change other than a bit of healthy competition.
I'm just a mere Control Engineer and so can do nothing more than write snotty letters about what I would like to see done. I do however hope PLC manufactures will soon see the merits in what I am proposing (which is by no means a new idea), and take it upon their collective selves to co-opererate.
I think they are all a long way off the mark at the moment and it doesn't stop at the PLC level. The current trend continues through to SCADA packages although that is entierly another topic.
When will the PLC catch up, I think it is about time!!!
Doug Panacea
Controls Engineer
Melbourne Australia