Forcing bits

[Ron Beaufort]

based on what you've posted so far, here are some examples of what I think the final answer is going to be ...

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[realolman]

If 'bit' doesn't refer to a physical input (one that has or can have a wire attached), you cannot force it.

If you can't , the software certainly gives you every indication that you can

 

[daba]

If you can't , the software certainly gives you every indication that you can

What version of RSLogix5000 are you using?
What "indications" that you can force something that isn't forcible are you seeing?

Can you show us a screen-shot of these "indications"

 

[ceilingwalker]

Output forces are applied between the output address and the actual I/O point. Therefore a force does not affect the output address state, just the hardware.
Input forces are applied between the actual I/O and the input address. Therefore they DO affect the input address state.
quote]
I don't know if you have been to the PLC Bootcamp in South Carolina but the way you describe this is almost verbatim how Ron taught it, as I recall.

 

[realolman]

What version of RSLogix5000 are you using?
What "indications" that you can force something that isn't forcible are you seeing?

Can you show us a screen-shot of these "indications"

Everybody wants a screen shot.

If there was a way I could upload a picture from my computer instead of fooling with photobucket or that sort of thing I would be glad to. The security they have on my laptop, I'm not too comfortable to even come to this site.

I think it's V 19 maybe 17... I'm on a different computer now.

You highlight the element. right click it, click "force on"
A Red ON appears under the element.
I would call that a very good indication that you can force it. If you can't, why does the software display all that? Maybe the right click menu should have it disabled. maybe the red ON should not appear. Maybe when you try to force it, the computer should make some sort of "error" sound or display... I think there would be a number of things the software could do other than what it actually does, as an "indication" that a bit can't be forced. Displaying a red ON is really not a very good "indication" that you can't force the bit

And what I'm saying is that you SHOULD be able to... Why should you NOT be able to force a bit to make sure the logic it controls does what you think it should do.

 

[Anirban Hazra]

I would call that a very good indication that you can force it. If you can't, why does the software display all that? Maybe the right click menu should have it disabled. maybe the red ON should not appear. Maybe when you try to force it, the computer should make some sort of "error" sound or display... I think there would be a number of things the software could do other than what it actually does, as an "indication" that a bit can't be forced. Displaying a red ON is really not a very good "indication" that you can't force the bit

I am using V17.01 and the software does indicate whether you can force a bit or not. When it's a memory bit(by which I mean that it does not refer to any physical signal) only the "Toggle Bit" option is enabled and the forcing options are disabled in the right-click menu.Only when the bit refers to a physical signal, do the forcing options become enabled.So if you are using V17, the fact that you can force that bit clearly indicates that it refer's to a physical signal. I do not know about the later versions though.

 

[Ron Beaufort]

let's see if a screen shot from OUR end of the pipe will help ... here's a picture that shows what Anirban Hazra is saying ...

not sure how obvious it is on YOUR screen display – but the "Force On" and "Force Off" menu selections for the INTERNAL bits are grayed-out and are NOT available ...

Everybody wants a screen shot.

everybody just wants to HELP ... a screen shot would make it much easier to be helpful ...

If there was a way I could upload a picture from my computer instead of fooling with photobucket or that sort of thing I would be glad to.

try hitting your keyboard's Print Screen key – then go to the Windows Paint accessory and click Edit and Paste ... doctor the results if you like – and save the file as a JPG or PNG format ... you should be able to attach that to your forum post – just like the one shown below ...

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[Daniel_LeRoy]

realolman,

Donnchadh mentioned this already but... Up on the top right of 5000 there is a tab that says enable forces. Have you enabled forces in the processor?

 

[realolman]

I know everybody wants to help... and this place is EX CELL ENT for that. Sometimes it seems like some of the folks are a bit condescending though... If everybody knew what Ron Beauford knows, this web site would not have much purpose.

What I tried to do is turn on an internal bit... It was not an input or an output but an internal bit. It appeared to me that when I tried to force the bit on that it was indeed turned on... there was a red ON under it, and it turned green... but the OTE after it did not turn on. WHen I forced the OTE on, it appeared exactly the same in the ladder logic as did the bit... BUT the solenoid it controlled was energized. If the output energized, would that not indicate that enable forces is enabled?

Again I am not on the computer that contains RSLogix5000 but I think it is the latest version... V19??

Also , I did not know you could just paste a picture into these posts... I guess I know that now... thanks

 

[Tharon]

I'll be the third to say given the information it sounds like the rung isn't being scanned. Forcing the output turns it on because that actually forces the output regardless of the rung logic. Forcing the rung logic true will only make the output true if the rung is being executed.

If you have the option to force, then it is force-able. Be it an actual Input/Output or an alias of one.

I'd like the see the screen shot.


And, don't try to take anything very personal if people here sound a little condescending. Most of the regulars don't mean it, and emotions don't convey well through text. I've had a few cases here where I was put off by a few people's perceived rudeness but it's usually just a misunderstanding.

 

[Ron Beaufort]

What I tried to do is turn on an internal bit... It was not an input or an output but an internal bit.

technically speaking such a "bit" can NOT be forced ... but obviously there's SOMETHING going here that needs to be explained ... I suspect that we're simply not talking about one and the same thing when we say "internal bit" ...

It appeared to me that when I tried to force the bit on that it was indeed turned on... there was a red ON under it, and it turned green...

let's just accept that statement at face value ... then maybe the figure below will help us along the way towards the truth ...

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[daba]

Another possibility is that the bit that you "think" is internal could be an alias tag that references a forcible I/O bit.

I would strongly recommend that everyone immediately goes to "Tools->Options : Ladder Editor : Display" and makes sure that the box in the picture is checked ON.

Even if this isn't the OP's problem, I cannot think of any reason why you would NOT want this important information displayed on the ladder display.