looking for home work

Hello all,
I was hoping the great folks on here would be willing to give me some home work.
About me...
I am a Bubba, 15 yr Maint Tech.
I am trying to better myself personally and professionally.
What I have to work with...
@work
RSLogix5,500,5000 and all the hardware associated w/ them. Plc5, Slc500/0,1,3,4,5. PV 300,600, 700+,100+. Micro 1000,1100,1200,1400,1500.
@home
RSLinx2.57, Micro Starter Lite 8.30 and a ML1000, (6 in and 4 out).
What I hope to get...
Some ideas or scenarios to try to program and feed back on what I come up with.

I had a lot of fun trying to do some ones home work from here. I want to get some more skull sweat rolling with all y'alls help.

Thanks in advance
OLSQ

wire up some momentary push buttons as inputs ... wire up a couple of contactors as outputs ...

use a momentary button to START one of the contactors (and presumably the MACHINE_A that it services) ... use a momentary button to STOP that contactor when pressed ...

use a "seal-in" rung construction for that system ...

now use another momentary button to START the other contactor (and presumably the MACHINE_B that it services) ... use a momentary button to STOP that contactor when pressed ...

but use "latch and unlatch" rungs for this system ...

get both systems working correctly – OFF and ON ...

now START both systems and leave them both running ... then put the processor into the Program mode – and then back to the Run mode ... tell us how both of those systems functioned ... did they function as you expected? ...

change the wiring of the buttons around (normally-open vs. normally-closed) ... does that change anything? ... which way gives a more "fail-safe" operation? ...

going MUCH further ... you might want to take a look at the Email Quizzes that are linked from the Sample Lessons page of my website ... there are several experiments (some complete with wiring diagrams) that are meant to be quite "challenging" ... it sounds like you have enough hardware and software available to work through most of those ... I'll guarantee that you'll learn something from those exercises – particularly if you'll put a lot of thought into answering what you "think" will happen before you actually run the experiment ...

good luck with your studies ... I envy you for the fun you're about to have ... just remember that there IS a life besides PLCs – and when the sun comes up – it's time to stop - at least for a little while ...

Ron,
Thank you so much for responding.
This is what I came up with.

well, your first three rungs are exactly what was expected ... not sure what you had in mind with those last three ...

did you try out the operation? ... how did the two programming methods (seal-in vs. latch/unlatch) compare when you put the processor back in the Run mode? ...

write it up ...

how about the "fail safe" idea? ...

write it up ...

Ron Beaufort said:

now START both systems and leave them both running ... then put the processor into the Program mode – and then back to the Run mode ... tell us how both of those systems functioned ... did they function as you expected? ...

change the wiring of the buttons around (normally-open vs. normally-closed) ... does that change anything? ... which way gives a more "fail-safe" operation? ...

Click to expand...

Ron,
The switch to program simulates a power down and restart condition. The "seal in logic" goes off and stays off until the input is made again. The "latch logic" stayed on even after a recovery from pwr dwn. I already knew this so I included a solution for it. I used a B3 bit that unlatches on first scan,

Thanks again for taking the time to learn an 'ol dawg new tricks.

I already knew this so I included a solution for it. I used a B3 bit that unlatches on first scan

Click to expand...

now we're getting somewhere ... how do you KNOW that a "solution" was required? ... just suppose that you WANT that particular machine/cycle/condition/etc. to come back on again after a power/mode cycle ...

if so, then a latch/unlatch construction (NOT a seal-in) is called for ...

now ... about using a Normally-Open button to "stop" MACHINE_B ... many electricians will tell you that ALL "stop" buttons MUST be wired Normally-Closed to make them fail safe ...

but ... is that ALWAYS correct? ...

if we really want the machine/cycle/condition/etc. to come back on again after a power cycle – think about what will happen when the plant suffers a complete power failure ... what happens to the Normally-Closed signal IMMEDIATELY upon the loss of power? (for now let's say that the input is wired with 120VAC) ...

so ... will a Normally-Closed "stop" push button reliably give us the desired "recover-back-on" operation? ...

where I'm going with this: several times over the last 20 years or so I've had the plant engineers phone me up a few weeks after I've taught a class for their "beginner" employees ... the conversation goes something like this: "What the heck kind of beginner class IS this? Our apprentices are coming back and pointing out serious flaws in our wiring and our programming that have been ticking time bombs for years – that we never even knew existed."

the point is that writing a program to "work" isn't really all that hard ... given enough time, most beginners will eventually get the machine to "work" perfectly in day-to-day operation ... the TRICK is to have the machine gracefully recover after all of the "what-if" conditions that pop up in NON-normal operation ... spotting those types of "issues" BEFORE they become "problems" requires a different mindset that takes most programmers years of experience to develop ...

and hint:

The switch to program simulates a power down and restart condition.

Click to expand...

well, maybe it does – but maybe it doesn't ... work through those quizzes I recommended ... you'll find out that (depending on your input wiring, the voltage, and the type of Allen-Bradley platform) it can make a BIG difference when you:

(1) go from Program mode back to Run mode ...

(2) have a plant-wide power failure that lasts for less than a second or so ...

(3) have a plant-wide power failure that lasts for more than a second or so ...

(4) use 24VDC or 120VAC for your Normally-Closed inputs ...

(5) use either MicroLogix, SLC-500, PLC-5, or ControlLogix hardware ...

(6) and so on ...

closing for now: you asked for "home work" ... be careful what you ask for ...