Simple switch function

bist · Oct 15, 2005

Hi,

I got myself an AB PLC5

I was wondering. How can one make a standar switch function.

I mean when 1 press a button then the light goes on. When I press it again the light should go off.

I looked at the latch function. But it didn't do what i wanted.

What functions should I use?

Thnx in advance

Ken Moore · Oct 15, 2005

This has been discussed many, many times. Search the sight for "flip-flop" logic.

Ken

Binaural · Oct 15, 2005

What you are after is a toggle. There are a lot of ways to do this; most use a one-shot bit so the toggle only executes once when you press the button. I often use something like this (ignore the *, they are there due to formatting issues):

*****button************ toggle
|------||--------[OSR]--------()----|

***toggle*** output******* output
|----||--------||--------------(U)----|
*********|
*********|
*********| output ***** output
**********--|/|-------------(L)----|

.... Although there are a lot of other examples readily found using the search function on the title bar - use that for basic questions like this in future

here's one to get you started...

http://www.plctalk.net/qanda/showthread.php?t=16588&page=2&pp=15&highlight=flip+flop

rsdoran · Oct 15, 2005

Latch (L) and unlatch (U) is something you should use once you have
learned when and how. This is basically the same thing http://www.patchn.com/flipflop.htm

Binaural · Oct 15, 2005

rsdoran said:
Latch (L) and unlatch (U) is something you should use once you have
learned when and how. This is basically the same thing http://www.patchn.com/flipflop.htm

Much of the boilerplate code we use for some of our system elements use that template for flip-flops, but I prefer the latch/unlatch form because it is more readable and harder to mess up if you are in a hurry. Otherwise, I don't think I ever use latch/unlatch instructions

bist · Oct 15, 2005

Guys, thanks a million. I'll try this.

I apologize for not using the search function. So I did not know what to look for. Now I do. It's a flipflop.

Thnx

bist · Oct 15, 2005

Guys,,One last question. Sorry to be so stupid. But I have no idea how the OSR must be set

I followed the example from the link in the post above

Can anyone help me?

Mickey · Oct 15, 2005

It would be much easier to use the ONS instruction ( one-shot) for your PLC5

bist · Oct 15, 2005

could you give me an example because i'm a total newbie.

I tried the example above but error. Invalid Output instruction position!

Mickey · Oct 15, 2005

Using Binaural's example:

bist · Oct 15, 2005

woooow that's great. Thanks

TConnolly · Oct 15, 2005

Another slick way to do it in a PLC 5 is with a counter and bit zero of the counter.ACC word.

XIC I:1/0 CTU C5:0 0 0
XIC C5:0.ACC/0 OTE B3/0

Everytime a binary number increments, the least significant bit changes state.
0000
0001
0010
0011
0100

Mickey · Oct 15, 2005

A closer look at Binaural's example, I don't think it will work.

TConnolly · Oct 15, 2005

Mickey said:
A closer look at Binaural's example, I don't think it will work.

In an AB PLC it won't work.
In a Modicon PLC it will work because the modicon solves vertically first. However, since its a PLC/5 we are talking about thats moot.

Simple switch function

bist

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