Subject: Re: Avoiding PLCs
Date: Thu, 17 Oct 2002 22:58:37 +0100
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"Bill Shymanski" wrote:
>Now, a PC, doing all the data logging and sending data to your networked
>office automation system, standing between the "office" world and the PLC
>world, is a really good thing - and you don't mind replacing it every
>couple of years.
I supplied a PC based data collection system running on a customer supplied
IBM PS/2 model 50 (think is was a model 50, desktop 25MHz 386).
It started life in a laboratory just off the production floor but was later
moved onto the production floor where it got a chance to suck in more crap
than was ever expected.
It ran more or less 24/7 for 9 years before being replaced under a Y2K
compatibility pretense. The monitor tube was shagged and there was so much
crap in the floppy drive you had trouble inserting a disk never mind
reading it, but, it was still working 24/7. The only crash I know about
occurred during a weekend of particularly violent thunder storms.
The replacement was an industrial plug in 486 processor ISA card in a small
industrial chassis (which at least had a filter on the fan) and a new
monitor. Just stuck in the original install floppy, hit reset, and away it