Hello,

I am trying to find pictures of PLCs (programmable logic controllers), SCADA (supervisory, control and data acquisition) systems, RTCs (real time clocks), and any other examples of embedded systems as defined by IEE:

'Devices used to control, monitor or assist the operation of equipment, machinery or plant. "Embedded" reflects the fact that they are an integral part of the system. In many cases their embeddedness may be such that their presence is far from obvious to the casual observer and even the more technically skilled might need to examine the operation of a piece of equipment for some time before being able to conclude that an embedded control system was involved in its functioning. At the other extreme a general purpose computer may be used to control the operation of a large complex processing plant, and its presence will be obvious.'

I have found one page of some pictures -- if others know of others pictures, please provide the URLs -- or better yet, please email me a "doctored-up" copy of the graphic file that the URL points to, along with the URL. In the "doctored-up" copy, bring up the graph, please, in paint shop pro, or some graphic package, or paint brush, and indicate with an arrow and a text label such as "PLC", "SCADA", or "RTC."

Also, if anyone can provide code examples of "latter logic" in a PLC showing some date manipulation code, that would be high appreciated too.

The page I have found so far (but without any of the pictures "doctored up" as I would like them to be) are:

http://net.onion.it/omav/htmlen/gallery.html

This page has a few interesting descriptions (with links) to goto: "Electrical panel with programming unit (Allen-Bradley PLC)" which shows this picture (link address): http://net.onion.it/omav/img/lav88.jpg Is the PLC the terminal unit on the left, or the big panel that it is connected to? Or is it both (the whole thing is the integrated system)?

Here is another link at the http://net.onion.it/omav/htmlen/gallery.html page:

"P.2200 ton: Gas heated log furnace max production 4000 Kg/h., four direct heated zones with combustion control trough PLC. In the exit zone is installed the gas conical heating."

It points to: http://net.onion.it/omav/img/fur9.jpg

Can you see the PLC in this picture -- if so, care to bring it up in paint shop pro, or paintbrush and put an arrow pointing to where the PLC is?

By the way, I spoke with an electrical engineer over an old 486 motherboard that was being thrown away, I wanted to know exactly where the RTC (real time clock) was. He told me that there are really four pieces to be concerned about:

(a) the battery that maintains the date/time/cmos data and keeps the clock working while the machine is turned off;

(b) the crystal whose vibrations provide the "raw data source" (c) the generator that converts the output of the crystal to a square wave that the computer can work on and interpret as a new date/time value (ie, the generator cleans up the vibration signal made by the crystal);

(d) the CMOS chip which stores the date/time representation of the current state of the RTC. (the engineers said that the Y2K problem in the RTC was in the CMOS data structure arrangement as the engineers had failed to provide storage for a four digit year value).

The engineer was able to show me all of these pieces, except he guessed which chip was the CMOS chip as he did not have a schematic for the motherboard.

My question, in all RTC environments, are there always these many components? I gathered from this engineer that some RTCs use fewer pieces, but I forgot to pinpoint him on exactly how fewer pieces would be involved. Comments anybody? Are there any URLs (doctored up) graphic pictures showing the RTCs too?

Thanks in advance to any who can help. I'll gladly give you credit and links, etc.

Postscript. This request may come as a surprise to people who have read my articles. But I have always been upfront about my background, which is 21 years in data processing preceeded by a computer science diploma, preceeded by years of Sociological research, including a M.A. degree and experience at various research centers. I do not directly with these embedded systems; I have never said that I do either. I just read about them and write about them because there is a gap among the Y2K literature on the topic that I felt needed to be "filled in." I gave a short bio stating this even in my Year/2000 Journal article. I've never tried to "pull the wool" over people's eyes.

And this email is trying to fill in another gap--nowhere on the web dealing with embedded systems are there pictures of these embedded systems. It's time we get them together. I'll put the pictures up on my web site or at least URLs to them.

Thanks, everybody, who bother to take the time to help here.

-Roleigh http://ourworld.compuserve.com/homepages/roleigh_martin

-- Anonymous, May 29, 1998

Answers

I meant "ladder logic" not "latter logic."

-Roleigh

-- Anonymous, May 31, 1998

Try these links http://www.abb.ch/abbgroup/businesses-products/segment/indust1.htm http://www.barber-colman.com/products/ http://www.eurotherm.co.uk/process/iedefault.htm http://www.foxboro.com/ http://www.bailey.com/ http://www.frco.com/fr/index.dgw http://www.iac.honeywell.com/ http://www.pantek.co.uk/ http://www.mooreproducts.com/ http://www.orsiweb.com/ http://www.intellution.com/ http://www.plcopen.org/ http://www.pas.com/d3k/ http://www.ad.siemens.de/simatic/html_76/pcs7/index_j.htm http://www.iac.honeywell.com/ http://www.aut.siemens.de/ http://www.controlartsinc.com/index.html http://www.modicon.com/ http://www.ab.com/ http://www.siebe.com/ http://www.wonderware.com/ http://www.yokogawa.co.jp/

-- Anonymous, June 11, 1998