Retentive On-delay Timer!!!!!!!!!

I NEED SOMEONE TO PLEASE HELP ME OR AT LEAST SOME HINTS ON HOW TO GET LOW VOLTAGE PROTECTION WITH THE DONEBIT BEEN TRUE ALL THE TIME IT SEEMS HARD TO GET L.V.P. (I'M A STUDENT AND IT SEEMS IMPOSSIBLE FOR ME PLEASE I WILL REALLY APPRICIATE IF SOMEONE COULD GIVE ME SOME HINTS ON HOW TO FIGURE THIS PROJECT!!!THANKS

What the ?

What does a done bit have to do with low voltage protection??

Please post the spec's for the project in question, then we can get a greater understanding of what you are asking and trying to do.

Suggestion -
Typing in "ALL CAPS" isn't the best way to ask a question, comes across as though you are "SHOUTING" at everyone.

yeah i am sorry!!!here i go again!

ok i have a I/1 exc on my first rung and at the end of it i have a rto(t4:0) that is preset at 1200 with a time base of .01.rung number 2 there is a donebit(t4:0)exc and at the end of the rung we have and output(O:2).ok so the headache is that when the accumulator reaches the preset value the donebit will be set to one(true)and the output(o:2)will be energized.And when the power goes off (with the plc in the run mode)once the power restores the output(0:2)doesn't have to energized back again(since the donebit(T4:0) will remain true all the time,and it can only be energized by a seperate press button. i think this helps for u guys to understand it better and what i want to accomplish is like in motor control called low voltage protection.
This is the ladder drawing i explain above oooo and if u can help me thank u! my brain will thank uthanks for the help!!!!!!
rto
I/1 timer t4:0
--[ ]-------------------------t. base .01------(en)
preset 1200----(dn)
acc 0

t4:0
---[]------------------------(o:2)--------------

You could use the 'first pass' bit to reset the timer.

I've read your last post 5 times now, and I'm still not sure I understand what you are trying to accomplish.

Let's ignore the ladder logic for a moment. Focus on the action-events that you should witness from the mysterious black (or grey) box.

First assumption: The PLC is always powered, and always in Run mode.

Action: Push and hold the button.
Event: After 12 seconds, the output comes on.

Action: Release the button after the output is on.
Event: The output stays on.

If the above is true, I can't figure out how you turn off the output. Is there a second button somewhere?

Action: (With the output off) Press and hold the button for only 6 seconds.
Event: Nothing happens.

Is this what the PLC should be doing? Or something else.

Hint #1: You say that you are using an RTO timer. RTO timers need a RES instruction to clear themselves (although like all timers, they will clear themselves when the PLC is first powered up or put into Run mode.

Hint #2: Here's a typical motor starter ladder:

     START     STOP    MOTOR

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

   |         |

   |  MOTOR  |

   +---| |---+

Does this suggest something?

Hint #3: When posting ladder diagrams, use the HTML tags [LADDER] before your code and [/LADDER] after your code. Otherwise, all spacing will be reduced to a single space, and things won't line up

I received the following private message:

thanks steve for the hint but it cannot be reset! the acc will have to remain in 1200 .

Let's keep it on the forum, cannonboy10.

If the ACC value is at 1200, then the timer is doing exactly what it's being told. You need to better define what you're trying to accomplish. Twelve seconds after the input comes on, the output gets energized. If power is removed from the PLC (or it gets taken out of RUN mode), the output gets deenergized. One of the reasons for using a retentive timer is to be able to ride through power outages without losing track of accumulated time, so when power gets restored to the PLC, the ACC value is the same as it was prior to loss of power.

So tell us, exactly what do you want to have happen to the output when power to the PLC is interrupted?

lets try it againg!

thanks first of all to all of you guys trying to help me!!! and am sorry I probably dont or cant really explain my self but I try again...

ok what I want to accomplish is.when the plc's power line comes back again the output(o:2) doesn't have to become energized.The donebit(t4:0)has to be true at all times.And I can't reset the timer,at the begining when the acc gets up to the preset value the donebit will become true and the output becomes energized,but when the plc's power line gets interrupeted the output will be deenergized,when the power is back the donebit will remain true but the output should not be energized again unless control by another individual switch.this is what I'm trying to figured out how can I program something like these,without reseting the timer and the donebit been true when the power fails and also when the power is back...once again thanks and hopefully this time u guys can understand what I want to accomplish.

Use a one-shot triggered by the timer's 'Done' bit as the 'Start' signal in the logic Allen posted. I'll leave it up to you to figure out how to work the other switch into the logic.

I hope I don't sound too picky, and I know that I frequently need to practice what I preach, but you could sure benefit from a course in expository writing. You may be a genius worthy of a MacArthur award, but how will anyone ever recognize your genius if you can't write a few clear lines of prose, reasonably punctuated!

If English is not your native tongue, try writing your question in your preferred language and translate it using any of several free translators available.

Thank You Steve!

The one shot Inst. will sure work fine with the Microligix 1200 and 1500,but I'm working with Micrologix 1000 (I'm in school)and I believe these Inst. woun't work with the Micrologix 1000. I believe I'm stuck ??? ooo and Thank You for your advise in my English, yeah I know there is a lot of things I have to improve(Thats why I'm in school)but I have just starter learning plc's and I know its hard for you guys to understand what I'm trying to accomplish so I excuse my self for that

Re: Thank You Steve!

cannonboy10 said:

I know its hard for you guys to understand what I'm trying to accomplish

Click to expand...

No, the problem is that it's hard for you to explain what you're trying to accomplish...

You CAN use one-shots in the ML1000. Check out the OSR instruction...

And since you're in school, I'll quote eastkodakguy... "DON'T GIVE UP!!!!"...

beerchug

-Eric

cannonboy10

I am having a heck of a time trying to figure out what you are trying to accomplish. Your RTO will maintain its acc. value through power outages and switching Run/Test/Program modes as long as the battery is good.
MCR circuits prevent motors and the like from automatically starting when power is restored, someone needs to press a button to reset the MCR.
Is this what you are looking to do?

Allen;
I know you have a good reason and maybe I can learn something here so run it by me one more time.
Why place the stop button after the start/sealing ?
Would you have the field wiring in that same order?
Why use a xic to represent stop. (I know either can be used but why xic)

Thanks in advance
Roger

If I can jump in here, I wpold say the order is just personal preference, and an XIC is used with a normally closed st of contacts on the field stop button so that if there is a broken wire then the machine will stop. With an XIO and normally open field contacts a broken wire will disable the stop function. Regards Alan Case

Alan Case said:

If I can jump in here, I wpold say the order is just personal preference, and an XIC is used with a normally closed st of contacts on the field stop button so that if there is a broken wire then the machine will stop. With an XIO and normally open field contacts a broken wire will disable the stop function. Regards Alan Case

Click to expand...

Or when cable is 'short-connected' disable XIC... What is their probability? It is as Alan wrote, most of case.
How you say it ? 'short-circuited', or ???

Alan Case

Ok.

Thanks Alan Case, you never know when you might learn something.

Roger