New Student looking For professional Insight

[peavey_wolfgang_2000]

Told you they would come around wolfgang. Their serious all they had to find out is if you were.
, but 3072 bits ain`t equal to 1024 bytes is it?

sorry I made a type-o it should read 3072 free bytes, and if you devide 3 into that you get 1024 in 1K

 

[peavey_wolfgang_2000]

With regards to Question 6

The largest amount of RAM available in a PLC processor is often----- or less?

(a) 16K
(b) 32K
(c) 512K
(d) 1K
(e) 2K

After some more reading, and in dept thought on this question, after reading some of your post's I concluded with this...RAM is constructed using TTL Or MOS Chips, these can be static or dynamic, some of the dynamic chips are embedded with refreash controllers, that in essance keep the capacitive storage fully charged in a dynamic chip....after reviewing some of Allen-bradley processors i came across the FlexLogix which uses this chipset and is avilable with either 64K or 512K....So with that said I guess C is my answer

 

[Terry Woods]

Wolfy...

I have a processor with 1.2 MEG of Ram.

That kinda blows your "512K" out of the water, doesn't it?

Do yourself a favor... don't waste your time on this sort of question...

The answer, in this case, is... it depends...

It depends on the particular PLC, the particular processor, and the particular version of that PLC/Processor.

 

[jolio ST]

In the end...

I've had a pretty quick scan of this thread and seen the many shades of expressions here. I'm glad there are students here who put in much effort in what they are learning, especially to those who are self-learning. But in the end, I'd still suggest to you to burn away that book (do not drink the ash with water, as with old chinese saying).

If you are in a tight budget, you can drop by some of the sites suggested by Ron (rsdoran), and I will mention this one more site where you can learn PLC in a general view. There are more info in the extended site if you are interested in micro-controllers, and electronics etc.

BTW, I find some of the questions you had posted very ambiguous. Can get pretty confusing, even to some of the experts here (Count me out for being an expert). Maybe the author needs to go for an english course.

Anyway, hope you like what you are learning, and study hard.

regards
Sherine T.

 

[new Mac]

Wolf,
I applaud you for being a self-starter!

Yes, your book is outdated, I have not gone through the learning tools presented on this site and therefore cannot judge their merit.

I too am a student (56 years old); follow up on Ron's replys on URLs.

Many of these folks will bend over backwards to help - search for pstephens SUPER long post (almost 700). These folks helped bring a machine from concept to production!!!

Many years ago I had a mentor who taught me a VERY important thing:
"Knowledge is gained by the inverse of the parts destroyed".
I don't break much these days - don't you be afraid either

Keep coming back! - we (the industry) need people like you.

Rod (The CNC dude)

 

[JesperMP]

Wolfgang.

An old book is not so good.
New books are better.
But far the best is to really work with some PLC code. The LogixPro program editor and simulator is quite popular with members on the forum. And it is also quite cheap (30 USD).

 

[DonsDaMan]

Wolfgang,

On the topic of why is 1KB 1024 bytes, I suggest you start dividing 1024 by two and see where that leads you. Also, remember that a bit has only two states while doing so.

Sherine,

I go to Singapore about twice a year. I know a girl there named Sherine (an acquaintance more than a friend). I've wondered if you were her, since your first post.

Don

 

[jolio ST]

Whoops!

Don

That's interesting to know you travel here twice a year.:nodi: I'm sure I do not know a Don, except here at this forum (that's you.)

Anyway, hope the trips you make to Singapore are pleasant ones.

On the topic of why is 1KB 1024 bytes, I suggest you start dividing 1024 by two and see where that leads you.

I'm quite sure wolfie here knows the basics of logic, that might explains why he is so interested in learning. Do correct me if my assumptions are wrong.

regards
Sherine T.

 

[peavey_wolfgang_2000]

EePROM QUESTION

I understand that each PLC manufacturer uses a slightly different method of organizing the information which is stored in the memory of the machine. Although all PLCs have similarities in their memory structure, such as RAM and ROM chips, the locations where bits of information are stored and the method the CPU uses to read this data can vary quite substantially. If Memory organization takes into account the way that a PLC divides the available memory into different sections, the ROM memory contains information that is not alterable, this portion of memory is a fixed quantity. However, the application memory is usually quite flexible in terms of how many bytes of information are allocated for any particular function. My question is which category does the APPLICATION PROGRAM of a PLC fall into?

My understanding (So far) is that an Application program should fall in a area well-suited in which nonvolatility is required....Would this be an EePROM.

Further insight on this would be great!!!

 

[elevmike]

These days the program is usually stored in EEPROM. Variables such as where data collected or manipulated is stored in RAM. To retain variable data during power cycles the RAM is backed up by a lithum battery, and/or a "super" capacator.

Some CPUs such as the Automation Direct D2-240, or DL-06 also allow you to store a small amount of variable data in a reserved area of EEPROM, however EEPROMs have a limited number of write cycles, so this data should not be changed frequently.

 

[peavey_wolfgang_2000]

Thanks, that clarified my inital thought!!!

 

[peavey_wolfgang_2000]

CPU tasks in a PLC

Another problem I am having is with CPU tasks in a PLC... I understand that The CPU performs 4 Tasks which are.....

(1) Input & Output operations
(2) Arithmetic & logic Operations
(3) Reading or Changing Contents of memory locations
(4) Jump Operations

(These are my own words, easier to understand)

My section questions was this:

Which Task does a CPU in a PLC Not Perform?
(a) Arithmetic Functions
(b) Basic Data Manipulation
(c) Provide Connection to process sensors for control
(d) Change the executive and applications program
(e) Execute the application program

Well....So far I understand the A,B,E are not an option, and my inital feeling is that The Cpu does not change The excutive & Application Program that has to be done by a programmer, through a programming terminal or PC....But the way the text book uses text it is a little weird, can someone one put in normal terms what they mean by "provide Connections to process sensors for control".....Would that be the same as JUMP OPERATIONS....?

Anyhow I think the answer is D !!!

Anybody wish to agree?

 

[elevmike]

I would also argue C. The connection between the CPU and sensors are usually done with "intelegent" modules such as a high speed counter or analog module.

I dont get the term "executive". My guess?? is that it's a reference to the firmware that executes the application program?

If there were a gun to my head, and I could only choose one; it would be D.

Wolfgang, So you paid a buck or so for the book at a garage sale and your diving into it.. That's good but I've got a better deal for you.. Click here: http://web1.automationdirect.com/static/manuals/d006userm/d006userm.html

This is a real manual written for a real PLC. It's done in such a way that an intelligent beginner with little or no expierance can pick it up quicly. This is a currrent manual for a current product. Place your gagage sale book within reach of the WC (for emergency purposes), and download the manual on the link and start reading that instead...Later when you get a few dollars saved up from flipping burgers (nothing wrong with that; I did it too) then you can buy a real PLC, maybe from Ebay and start playing with that.. Then the manual would apply direclty to the PLC.

BTW.. Here's a DL-105 on Ebay for $5.00..until the next bid..
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=97184&item=3880649170&rd=1

 

[elevmike]

If you get lucky with the Ebay auction, then heres the software and cable for the DL-105: http://www.automationdirect.com/adc/Shopping/Catalog/PLC_Hardware/DirectLogic_105/Programming_SW_-a-_Cables/PC-PGM-105

Or you can download demo software here: http://support.automationdirect.com/demos.html

 

[peavey_wolfgang_2000]

Discrete Output Devices

Which of the following are discrete output devices?

(a) Motor Magnetics & pushbuttons
(b) Limit Switches & Control relays
(c) All Of The choices listed
(d) Solenoid valves & thermocouples
(e) Motor magnetics & pilot lights.

This is what i understand so far concerning Discret Output Devices.

Discret Output devices fall into a list of devices such as

• Control Relays
• Alarms
• Valves
• Motor Starters
• Solenoids
• Fan's
• Lights

Which in a PLC Module, it provides an interface between the CPU and the output componets like the ones I have listed.

My question Is what or Even If a THERMOCOUPLE falls into a discrete output device.

I know that a THERMOCOUPLE is a device which converts Temperature into Voltage.

With what I understand so far I know that the answers can not be A, B, Or C, my gut feeling is leaning towards D.

Some help on this Would be greatfull !!!!