Another "Anti-tie down" question.

Question, why is an (OSR) command even needed when a [TON] timer is use in a “Anti-Tie Down” program. This is my next project for school. I’ve read the book on timers several times. It explained what they are, how they work, and what they look like, but it did not relate how to use them with any relative type of application. I did a search (on this site) for anti-tie down questions and found several. In looking at these ladders on-line, I still do not understand the need for the (OSR) commands. The two ladders that I produced on paper prior to the search did not need any, banghead that I can see of. Being new to this, I’m probably missing something.
Any help with this?
Thanks, barry.
P.S. I'm still learning how to operate within this forum, so as soon as I figure out how to display my ladders, I will if needed.

Well Barry

One Shot Relay OSR is time of one scan time of the PLC. it go on for one scan.
What it giveing you?
It give you the option to operate function who need short signal to start to run like mathematic function.
It also can save you programing work if you use it in right order .

I looking for example.I will send you when I will find it.

Go to you can see example of OSR.
http://www.plctalk.net/qanda/showthread.php?s=&threadid=5143

Anti-repeat

I'm not sure which code you are looking at which includes a one-shot. Im essence, you are right, for anti-tie down, a one-shot isn't needed, as the code HERE shows.

But anit-tie down isn't the whole story in safety. Usually, not only do we insist that the operator place both hands on the control panel before starting the machine, we also want to make sure that he releases the buttons before the machine will start a second time. This is referred to as anti-repeat.

Since the key to anti-repeat is to have the button pressed and not have the system react again until the button is released and pressed again, a one-shot is the most common method (but not the only one possible) used to keep track of the releasing of the button. The bit will be ON for only one scan when the button is pressed, and will not be ON again until the button is first released.

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As for posting ladder to this forum, just use the LADDER button immediately above the Your Reply: window when posting.

A dialog box will popup. Just add a space character and click OK.
There will then be two vB tags added to your message:
[ladder] [/ladder]

Everything between those two tags will be posted exactly as you lay them out. So use whatever characters you like (dashes and 'pipes'('|') are popular, uses spaces to line up the text, and you're off to the races.

You would write something like this:

[ladder]                  

   2b         ?           

---| |---+---( )          

         |                

   2b    |                

---|/|---+                

[/ladder]                 

Click to expand...

And it would post like this

   2b         ?

---| |---+---( )

         |

   2b    |

---|/|---+

BTW, this is a quote from Shakespeare.

To be or not to be, that is the ERROR-Operand not entered! ?

I've said this before. Allen's quote is evidence that either George Boole or Dick Morley is the real author of the plays attributed to William Shakespeare.