Internet PLC Forum

General => Frequently Asked Questions => Topic started by: Yoseph on December 31, 2002, 07:55:32 PM

Title: I don't get ladder logic.
Post by: Yoseph on December 31, 2002, 07:55:32 PM

???

      I have done some machine language programming and some of the other higher
level programming. I think I have a good understanding of how computers work. Does a
ladder logic symbol relate to a specific routine in the PLC?
      I have a PLC I am trying to learn to programm and ladder logic is not making a lot
of sense. I hope some one here can point me in a direction of a good tutorial, a book
or a web site.
                                                                      thanks

Title: Re: I don't get ladder logic.
Post by: support on January 01, 2003, 08:25:45 AM

If you need very fundamental knowledge about ladder logic, please visit:

 http://www.plcs.net

I hope it helps.

Title: Re: I don't get ladder logic.
Post by: philipjoseph on January 07, 2003, 10:08:06 AM

HEY YOSEPH, CHECK THIS: http://claymore.engineer.gvsu.edu/~jackh/books/plcs/html/plcs.html

THERE IS A COMPLETE AN USEFUL MANUAL.

PHILIP

Title: Re: I don't get ladder logic.
Post by: Yoseph on January 07, 2003, 02:45:49 PM

 Hi:-
      That is exactly what I need. Thanks a million Philip.

                                                       Yoseph

Title: Re: I don't get ladder logic.
Post by: MAD on February 06, 2003, 01:27:55 AM

Try this link also.  Lots of example programs, Downloads, and  lots of other links!!!

http://www.geocities.com/plc_guide/index.html

Title: Re:I don't get ladder logic.
Post by: Adam on November 22, 2005, 02:26:19 PM

What would the ladder logic look like to create the movement of an X-Y table (with the use of two stepper motors) to create a parabolic function and a circle?

Title: Re:I don't get ladder logic.
Post by: Myers on November 23, 2005, 06:47:28 AM

I tend to think of my PLC's differently.  There is no real way to do what you want with ladder logic.  It's easier to accomplish with a function as an output in ladder logic.

Ladder logic deals primarily with solid state.  A device is either ON or OFF.  A switch is either OPEN or CLOSED.  Each device, say for example a light bulb, has a number of things that have to happen to turn on.  Switch 1 may need to be open, Switch 2 may need to be closed and either Switch 3 or Switch 4 must be closed.  It relatively easy in ladder logic to perform this.

Wher Tri-Logic comes in is that instead of turning on a light with all those switches, you can turn on a BASIC program that will run and perform your functions.

In your case, a function output would be controlled by inputs called "E-Stop Pressed" AND "Light Curtain Clear" AND "Start Button Pressed".  When all three of those events happened at the same time, a function (Output) would be run to pulse your steppers incrementing or decrementing your X and Y values to make your pattern.

The challenge is not really in the Ladder Logic, but in the BASIC function!

Mark Myers

Title: Re:I don't get ladder logic.
Post by: support on June 23, 2006, 11:23:45 AM

Chapter 8 in the TRiLOGI Programmer's Reference Guide has a short introductory course on Ladder Logic Programming. For those interested, please download the Chapter below:

  www.tri-plc.com/appnotes/Chapter8.pdf

Title: Re:I don't get ladder logic.
Post by: support on August 08, 2010, 12:33:44 PM

You can now go to the following web page to download a free PLC programming E-book written by Kevin Collins of Ireland Sligo Institute:

http://www.tri-plc.com/reqplcbook.htm

This book presents a number of ladder programs that are constructed using the TRiLOGI software and you can use our PLC simulator to test the program.