[H-GEN] Remote process monitoring & control

[Michael Anthon]

(Note reply-to: being general at humbug.org.au vs Michael Anthon <mca at tams.com.au>)

Oh, err.. bleargh.

OK, I misunderstood.  I thought you were going to interface into the
existing PLC systems to get the info you wanted, not add a complete new I/O
system to do it for you.  If it is a simple parallel I/O board such as you
are talking about, reading/writing them is usually as simple as
reading/writing some part of the I/O space on your PC.  Many, many years ago
I used to do this sort of thing with a system called OPTO 22 and Turbo
Pascal *grin*.

If you are putting this into a commercial factory situation, I would look
very carefully at the electrical isolation of the system you are using.  A
lot of the cheaper systems are not well designed which can lead to several
problems.  The most drastic of these is a total breakdown of your isolation
during a fault condition (which could be as simple as a surge from a motor
causing a voltage spike).  This can lead to nasty high voltages being
applied to parts of you computer that they really should NOT be applied to
and even into your LAN if the network card is also not well isolated....
Another potential [1] problem is the injection of HF noise into your
computer from the I/O circuits (again, usually caused by switching of heavy
machinery motors and solenoids).  This tends to cause extremely hard to
duplicate intermittent faults.

This should be the sort of thing that would be pretty easy to do in Linux,
you could even build a nice web interface to allow you to view the status
and control things...  I've never done any I/O work in Linux, perhaps
someone else could tell us how hard this is to do.  Would perl or PHP be
capable of doing I/O?  That would be nice 8^)

Hehe.. looks like programming in VBA [2] for the last couple of years hasn't
dulled my interest in this sort of stuff.


Cheers

Michael

[1] Pardon the pun
[2] Take pity on me

> -----Original Message-----
> From: Doug Young [mailto:dougy at gargoyle.apana.org.au]
> Sent: Thursday, 15 July 1999 1:57
> To: general at lists.humbug.org.au
> Subject: Re: [H-GEN] Remote process monitoring & control
> 
> 
> (Note reply-to: being general at humbug.org.au vs "Doug Young" 
> <dougy at gargoyle.apana.org.au>)
> 
> 
> -----Original Message-----
> From: Michael Anthon <mca at tams.com.au>
> To: 'general at lists.humbug.org.au' <general at lists.humbug.org.au>
> Date: 15 July 1999 10:00
> Subject: RE: [H-GEN] Remote process monitoring & control
> 
> 
> >(Note reply-to: being general at humbug.org.au vs Michael Anthon
> <mca at tams.com.au>)
> >
> >This is a pretty broad subject.  There are many, many, many 
> types of PLCs
> >and factory automation equipment out there.  Unfortunately, 
> because it is a
> >fairly competitive industry, there was never a defined standard for
> >inter-communication between these devices.  Each 
> manufacturer tended to
> come
> >up with their own protocol.  Some used RS232, some RS422, 
> some optical
> >fibre, some a parallel interface.. etc etc.
> >
> >That said, the Gould MODBUS protocol has become somewhat of 
> an industry
> >standard and when I was last involved in this sort of thing 
> (about 3-4
> years
> >ago) there were moves afoot to produce a standard protocol 
> (I think it was
> >called FieldBUS or something, F-BUS perhaps).
> >
> >At what level do you need to interface to these devices?
> 
> ummmmmm .... would you re-phrase that in words of less than 
> two syllables ??
> The situation involves a bunch of (mostly) plastic extrusion 
> moulders with
> PLC's already and I want to be able to monitor simple 
> functions like has an
> alarm tripped / is something running or not  etc. There are 
> heaps of Windows
> boxes around the place including spare 486's that could be switched to
> whatever flavour of unix, a LAN between the actual factory 
> and the office,
> and a dialup WAN to another office location. Ideally the 
> status of various
> machines will be monitored from anywhere with dialup access 
> to the LAN, and
> hopefully also from the net.
> 
> If you are going
> >to have to write serial protocol drivers for them, then I 
> would suggest
> that
> >VBA would not be the tool of choice.....
> 
> 
> OK .... so is there a reasonably straightforward solution ?? 
> ..... I notice
> both Jaycar and Dick Smith have cheap I/O interface kits 
> available that
> apparently use QBasic programming and which appear to do what I need,
> however I don't know whether or not I can monitor and control 
> stuff remotely
> if I use QBasic.
> 
> 
> 
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