PLC basics

Hi
I am a total newcomer to the world of PLC. While studying about the PLC I/O , I came across a statement saying: Modules can be composed of 2,4,8 or 16 points. So I would like to know if points are different from the I/O's of a PLC.

Thanks in advance

Pravin

Thats the problem with these texts, they mean exactly what the author wants them to mean, no more, no less.......

Now out of wonderland and into the real world. Points in this context would be equivelent to individual I/Os. An I/O can be digital, or single bit, or it can be an analog value which can each range from 8 to 16 bits (Or theoretically more). Or it can be a special input such as a counter with 3 or 6 input points translating to a 16, 24 or 32 bit input.
To add to your text, 32 point cards are also common, and 64 point cards are also on the drawing board if not on the shelf.

Points are the number of connections. A microplc may be listed as a 10-point controller which means it will have 6 inputs and 4 outputs (normally). A card (module) could have 4, 8, 10, 12, 16, or 32 points depending...., it still represents the number of possible connections whether input, output, or both.

High Speed Counters usually use the term channel...ie one channel but that one channel may have multiple "points" which are used dependent on the configuration of the module.

Analog cards usually just refer to "channels", the term "points" is not usually used with analog cards.

imho, it depends on manufactures terminology and local customs mainly ...i know comapny, where everything is labeled 'channel' - no matter of type or speed or usage ... etc.

so i guess... author just had in his mind some certain device (modules), one can buy today anything from 1 i/o to n i/o devices ...

I am not sure what local customs would have to do with it. This is 20 or more year old terminology that may be more common to US (or English) products than others but it is used by most in some fashion.

AB, AD and GE regularly use the term "point" when refering to modules etc. Siemens uses the term but not as often, I have seen it used when refering to using a specific common to a specific number of "points". Omron also commonly uses the term "point(s)" in reference to their units.

Omron: http://oeiwcsnts1.omron.com/pdfcatal.nsf/PDFLookupByUniqueID/9F255B35944B008086256A29005C88D7/$File/D11CPM1A0301.pdf?OpenElement

AB: http://www.ab.com/plclogic/micrologix/1000/

AD: http://web2.automationdirect.com/static/manuals/d006userm/d06uservol1.pdf

One I have never used
Mitsubishi: http://www.mind.ne.jp/melsec-f/english/plc_fx/lineup/index_e.htm

Its basically just a reference to the number of connection "points" primarily pertaining to digital inputs and outputs but may also be used for description of other modules. As an example AB in the link describles the starter ML with free software as a 10-point controller. In the OMRON link it shows 30 and 40-point controllers. On the AD website all the digital I/O refer to "points" for the modules...ie 8 point input, 4 point output etc etc.

I wish I had the time to develop an all encompassing glossary or dictionary involving industrial terminology and definitions, including common abbreviations etc.

rsdoran said:

I wish I had the time to develop an all encompassing glossary or dictionary involving industrial terminology and definitions, including common abbreviations etc.

Click to expand...

Go to Wikipedia and look up "Sisyphus". Also see Alaric's avatar.

LOL Steve, took me a few minutes to get the relevance. In other words I may as well try to physically count Avogardo's number.

rsdoran said:

I am not sure what local customs would have to do with it.

Click to expand...

... just that i'm not from english-speaking country, it's about translation problem in most of companies here

Like i said Siemens does not use the term that often. From my German class I can see why that may be...I am not even sure which term you would use in German...der Punkt? die Stelle? die Siete? der Zietpunkt or would it be more technical like der Anschlusspunkt.

Then again you may not know German either and have to deal with a translated version which could have issues.

Steve Bailey said:

Go to Wikipedia and look up "Sisyphus". Also see Alaric's avatar.

Click to expand...

All in a days work.

Here is one I created a few years ago, back when I was first learning how to make animated GIFs. I sketched the frames out on autocad, then converted them GIF layers. Its a modern day variant of Sisyphys.




(edit to clarify, I didnt create the avatar (just the home-to-factory gif), The avatar is fairly common on the net)