Anti -Tie Down - Non Repeat - No Timer

[OkiePC]

Huh?

For last time I am arguing that they have been taught so basic things for now, that it would be too much from their teacher to ask to do "timer" themselves and only thing required is to make sure that both buttons are depressed before pressed again. Ofc that really is not anti tie down as we see it, but it does defeat only one button usage.

This is not anti-tie down. Did this come from the instructor?

Look at this and make sure I am right:

 

[Tharon]

Ya, that logic doesn't provide anti tie-down. I guess if you were to parallel a NO I0.0 and NO I0.1 in the first network, rather than series. Then put a NO I0.0 and NO I:0.1 in series withthe M0.1 "Pulse" in Network 3. But that would require both inputs to turn on within the same scan, not giving you much of a time delay for human and mechanical timing.

 

[TurpoUrpo]

This is not anti-tie down. Did this come from the instructor?

Look at this and make sure I am right:

Did you not read what i did say? its not anti tie down as we see it. Its about very basic code assignment with very basic instructions.

Did you not read that assignment at all? You need to clear everything you know from your mind and step into students shoes who does not know anything about real anti tie down.

"Operator must release both buttons in order to initiate another cycle of the punch press" is underlined in the assignment as is what that code does, one needs to release both buttons before output is turned on again after releasing any one button.

Its school assignment, you cant expect it to be more than it says in it and you need to consider what is level of knowledge that can be asked of students, he said its basic course, they have not covered latches, timers, counters, what do you expect them to just look at crystal ball what anti tie down is?

PS. You can make valid argument about very badly worded assignment, but try to understand what really is wanted in it.

 

[OkiePC]

Did you not read what i did say? its not anti tie down as we see it. Its about very basic code assignment with very basic instructions.

Did you not read that assignment at all? You need to clear everything you know from your mind and step into students shoes who does not know anything about real anti tie down.

Yes, I read the whole paragraph. Here's the last half including your sentence...note the sentence that follows.

...both buttons must be pressed simultaneously in order to fire the punch press solenoid. However, the operator must release both pushbuttons in order to initiate another cycle of the punch press. The operator must not be able to apply duct tape or a wedge to tie one pushbutton down, while operating the machine using a single pushbutton.

Its school assignment, you cant expect it to be more than it says in it and you need to consider what is level of knowledge that can be asked of students, he said its basic course, they have not covered latches, timers, counters, what do you expect them to just look at crystal ball what anti tie down is?.

No, but don't assume you can read the underlined sentence and ignore the rest of the page just because it's just a high school level trainer and nobody will get hurt. I also did read where you stated it was not the same as our conception of two hand safety, but I beg to differ. I think you assumed something about the assignment that I find to be incorrect, and potentially distracting, so I pointed it out.

Please don't be offended, if I make a mistake and someone corrects me, I am grateful.

Thanks,
Paul

 

[TurpoUrpo]

Okie, the assignment itself does not state anti tie down anywhere on it. It says that operator must not be able to tie down other button and operate with only one without releasing another one.

Please just read it with your mind in it.

 

[OkiePC]

...It says that operator must not be able to tie down other button and operate with only one without releasing another one.

Your program allows exactly that violation. You can tie one button down indefinitely, and then cycle the press once by pressing the other button at any time thereafter, no?

 

[TurpoUrpo]

Your program allows exactly that violation. You can tie one button down indefinitely, and then cycle the press once by pressing the other button at any time thereafter, no?

No, both must be released before new cycle.

 

[OkiePC]

this is what happens when we use the wrong tools

So, it's okay that it cycles once per tie down occurence?

 

[TurpoUrpo]

So, it's okay that it cycles once per tie down occurence?

That is what im saying, assignment requires both buttons be pressed simultaneously (eg. not one after one or one only), then it requires that output is turned on, after that it requires that before new can be made, both buttons are released.

Nothing more nothing less.

In school assignments one must see trough the additional decoration of said assignment.

Remember, I did not say that would be ok for press to operate in such manner, I have only been talking what is really required in given assignment.

 

[OkiePC]

Okay, I give up. First, you must not read anything extra into the assignment, now we must see through additional decoration in the assignment like the part about presses, tie down and wedges.

 

[TurpoUrpo]

Okay, I give up. First, you must not read anything extra into the assignment, now we must see through additional decoration in the assignment like the part about presses, tie down and wedges.

No don't give up if you think otherwise. I mentioned that "nice wrapper" for motivation before, so its not "first and now".

Its school assignment, it has nothing to do with real deal. Its meant for students to think how plc works, its just in nice wrapper to do it more motivating for them.

Assignment itself does not require looking for how long one button is pressed, it requires only to not be able to keep it pressed while operated by one button only. Only thing that is needed is to make sure that both buttons are depressed before pressed again.

ps. its about plc's, not presses, not filling machines, requirement is about plc's not about real world application.

 

[Tharon]

Let's break down the info a bit more. Okie is correct here.

Both buttons must be pressed simultaneously in order to fire the punch press solenoid.

Requirement number 1. Two buttons needed to operate

However, the operator must release both pushbuttons in order to initiate another cycle of the punch press.

Requirement number 2. Buttons must be released at the end of a cycle before the next cycle can start.

The operator must not be able to apply duct tape or a wedge to tie one pushbutton down, while operating the machine using a single pushbutton.

Requirement number 3. Either button cannot be tied down and then operate the press using a single button.

Your example does not meet requirement number 3. Notice that it's a separate sentence. A separate requirement, not just a rephrasing of the "must release buttons" requirement.

 

[DamianInRochester]

At the risk of stepping into the line of fire..........

Paul's point is that you have allowed a situation where you are not forcing the operator to press the buttons simultaneously.

Paul interprets what he read as that it is the programmers responsibility to make sure that the operator presses the buttons simultaneously.

Your interpretation was that it is the operator's responsibility to press them simulatanously.

I think 999 out of every 1000 people would interpret it the way Paul has. Including myself. The fact that they gave the problem context by realating it to a well known punch press application makes it difficult to interpret it otherwise.

 

[TurpoUrpo]

Requirement number 3. Either button cannot be tied down and then operate the press using a single button.

Your example does not meet requirement number 3. Notice that it's a separate sentence. A separate requirement, not just a rephrasing of the "must release buttons" requirement.

Fair enough.

 

[Lancie1]

I changed the CPU to a 5/05 and addresses to match the assignment too,...

Paul, I think you have something that will work, although probably more real than the instructor ever imagined! I think though that Raydog needs a SLC 5/02 version instead of the 5/05 version. A lot of those old 5/02's were set up for those PLC trainers.

We are using AB 5/02 PLC in class, if that helps any.