STATUS -- learning making mistakes - rembering them

NOW if i could just tipe.

School goin good. Overcame confusion on XIC and XIO ( Allen Bradley ), did the timers, figgered em out, made a flasher out of two TONs, worked well SO WELL took that file and used for a subroutine tonite.

PRIDE GOETH ,,,,,,,

So the instructor got me with this task.

Have a pump.
There is pressure switch (# 1) on suction.
PS 1 must be shut to start pump.
There are two more Pressure switches on discharge (2 and 3)

After starting pump
PS 2 and 3 must shut after pump start to keep pump running.
IF NOT pump shuts down 5 sec after start.
A time delay will not let pump run for another 14 seconds.

I could get parts of this to work BUT not all ie had to wait 19 sec before pump could start.
Started off with a 5 sec and a 19 sec TON (Allen Bradley) USING RS LOgix 500 (not starter) PCL is # 1761 L 32 AWA.

Gave up after two hours - fatigue and all that and after two other hours with flashers and flasher subroutine.

SO one of you guys want to take a crack at it.
DO NOT give me solution please.
I need to figure it out on my own.

Let me know how long it took you to do it

Thanks
Dan Bentler

Hi Dan,

I say sleep on it and come back in the morning

Things usually look clear in the morning when you read this. Since you are a "sparky", draw youself a typical pump/motor start circuit using momentary start/stop button. Excuse my drawing, i'm not a EE or sparky.

------] Start PB [----------------------------( Motor )------

   |                         |

   |             Stop PB     |

   |--]Motor[-----]\[---------

You see the branch, right? Now think of the Start Pushbutton as your start condition (#1 Pressure Switch). And now think of the lower branch as your stop logic. Replace the Stop Pushbutton with your conditon to stop, hint Time Done... another hint: PS#2 & PS#3 has nothing to do with your Starting condition.

Hint:
Consider using the .TT bit of the 19 second timer.

Clarify

Thanks guys.

No problem starting pump.
No problem with 5 sec time delay shutdown if PS 1 & 2 dont shut.
BIG problem iwth the 14 (19) sec anti restart. Got it to work but then had to wait 19 sec when went to restart pump.

Used the TT on it and I think I am close.
I think the whole problem is getting the timers to reset.
Gonna have to read the book again and scribble on paper.

Will let you know how I make out
or scream for help

Dan Bentler

OOPS

No problem with 5 sec time delay shutdown if PS 1 & 2 dont shut.

The above in previous message was wrong.
Should have read if PS 2 and 3 don't shut.

Dan

Ok, I'm not 100% clear but it seems you said in your post:

-You push Start button and the pump didn't start until 19 seconds later.

Correct? If so, it is most likely you are mixing the logic for the start and the stop. Try to work on one thing at a time, get the pump to start ok then work on the "interlock" logic. Troubleshoot one thing at a time.

hint: your 19 seconds time should NOT be starting to count if your pump was stopped to begin with. it should only be running when the pump goes from RUN to STOPPED condtion. ie. it's a transition. One shot & Latch are handie for "capturing" a transition event.

-sorry if we confused you more. Give it some time and if still don't work, post your logic.

MAYBE ??

OK I think I got it. Spent some time scribbling on paper. Will test on Tue. Will let you know how made out.

Dan

Why wait until Tues?

Draw the code you have come up with, between the text [LADDER] and [/LADDER] and we'll be able to tell you if what you have will work or not.

Using those pseudo-HTML tags, you code will come out WYSIWYG, with all the spaces that you type.

REPORT

Allen,

Thought I would go to class rewrite erroneous program I have, test it.

THEN (hopefully I am right and I have the solution)
I would copy the RSS file to floppy,
take floppy home attach RSS to email here
and send the whole thing.

THAT way it wold make it easier on you guys to understand by eliminating my "scribbling". Besides the software makes much neater drwaings than I do. AND NO TIPOS.

Dan

Clarification:

I'm a little confused on your specification.
Is it that the motor cannot be restarted for 14 seconds after it was started, or cannot be restarted for 14 seconds after it has stopped?

Here is the Order of Operations as best I can figure

1.If Pressure switch #1 closes Start the pump
2.After the pump is running Pressure switches #2 and #3 must both close if the switchs have not closed within 5 seconds shut the pump off
If the 5 second timer is done do not let the motor restart for another 14 seconds

UNDERSTANDINGS

Ken and MRdrd

Mrdrd has it right.

Tomorrow is the acid test.
Dan

SUCCESS

OK I got it to work. USED two TONs (one for 5 and one for 14 second anti restart).

BIG LESSON easier to start timers than it is to stop them.
Apparently this program will not allow RSS file.

NUTS now I need to figure this out. Too late to get creative.

THEN took out the 5 second timer and reset the 14 to 19 sec. USED GEQ to measure timer accumulate equal to 5 and also 19. WOrked great.

FINALLY took out the GEQs and used the limit (LIM)to measue accumulated time at 5 and 19. Worked so well and so easy I am almost afraid of it. Any thing that looks that easy has to have a catch. I know it will keep on comparing unless stopped.

Any way thank you guys for not giving me the answer. I learn best by figuring it out myself. The hint to use TT did help that I was on the right track.

Dan BEntler

you have to post your RSS file as a zip file use winzip compress then post

WIN ZIP

ANOTHER LEARNING OPPORTUNITY

I wonder if the school has win zip on their computr??

I don't (guess that was kind of obvious)

SO let me explore options and get those files to you guys.

The instructor liked what I did, but I think a review done by guys "in the trenches" is just as if not more valuable.

One of the really neat things I like with this PLC stuff is you can label your contacts so you know what they do as you go thru pages as opposed to now lets see CR3a5 ,,,,,
Gotta get better at that so the next guy can figure out what I did.

Dan Bentler