STUDENT QUESTIONS, please post them here!

Lancie1

Lifetime Supporting Member
Join Date
Jul 2003
Location
Alabama
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Several have asked for a place to post student questions, so here it is. Go to it, all you students!
 
I need program to give my instructor. Does not matter for what plc, we have none here. We have not had program instruction. One day assignment was what is a plc. One day assignment was what is a program. One day assignment was name 2 brands plcs. Most failed that one.

Also, if anyone have autocad, please email me copy.

Thank You.
 
Unregistered,

Here is a LogixPro program and a challenge for all students. This is a ZiPPED LogixPro file, type *.RSL

The situation: You and your buddy Joe flunk out of the PLC training class. Deciding to go into the job market, the best jobs you can find are at a Chicken Processing Plant. Your jobs are to take incoming ckicken carcasses and hang then on the overhead chain conveyor that takes them into the scald-and-dip tank.

The boss finds out that you and Joe have PLC training, so he asks he to make some changes to the Chicken Conveyor program to make it run faster. Joe says that there is no reason to tell him that you had flunked out of PLC school.

One Monday after a wild weekend party, Joe is hanging a chicken on the hooks. He slips on the wet floor, and the next hook catches Joe's belt and drags him off his feet and towards the scald tank. Your job is to stop the conveyor before Joe is scalded like a dead chicken. Unfortunately, the program Stop Pushbutton does not work exactly like you and Joe thought it would....
 
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Chicken

Good Morning lancie1

I too am a student of PLC's evidendly not as savy as you, since I have worked in Poultry for the last ten years.

It is the best Job I ever had, I have worked on a piece of everything in all industies and made good money.

Maybe one day I can be like you Sitting at a desk programming away?

regards

Chicken Man
 
You fail to see the sarcasm in his post, second unregistered guest. He is not poking fun at the Chicken Plant. He is poking fun at him and his buddy. It is classic now, that 95% of the students that come on here want us to do their homework or tests. They have no desire to even give it a try. And then they ask for something like AutoCAD. What a joke.

I am glad you had a good experience there. My own background had me in the Pork and Beef Slaughter industries. They were good jobs, too.

But the fact is, do you want to stay in that kind of job? No, otherwise you wouldn't be here right now.

David
 
Chicken Man,

I do not mean in any way to insult you. I really appreciate that there are those who are willing and able to work in poultry processing so that the world is supplied with chicken and other great foods. You should also see that there are those of us who are not suited for such work, neither physically nor mentally.

My goal was merely to create a problem that was both challenging and fun for new PLC students. Has anyone tried to stop the conveyor before the 180 second timer reaches the kill zone? It might have a few surprises for some of you....

P.S. It is a rare day when I get to sit at a desk and write a program. I consider it a bonus when a new program comes up. I would almost work for free to be able to have the challenge of programming a PLC. I consider the writing of the program to be the bonus that makes all the other things bearable. I would like to be able to do more programming and less specifying, purchasing, contract writing, drawing, designing, calculating, trouble-shooting, consulting, and general customer hand-holding. I hope they build more chicken plants with PLC-controlled equipment, and I hope the remaining small plants in the US don't all move to another country.

Greg, you probably didn't know that I started this thread in the PRACTICE POSTING HERE section, not expecting it to be very popular, but still a place for those requesting a separate student section. Phil must have moved it over here to the main section, or does his computer move a thread automatically once it gets a certain number of hits?
 
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Lancie1

My goal was merely to create a problem that was both challenging and fun for new PLC students. Has anyone tried to stop the conveyor before the 180 second timer reaches the kill zone? It might have a few surprises for some of you....

Thank you for taking the time to create this exercise. It should help others learn to debug a program.

I found the input to stop the conveyor, but I won't spoil the exercise for others.

Barry
 
Barry,

Congratulations on finding the Chicken Conveyor "off" button. Would you like to write a Student Challenge program of your own to submit here?
 
That's okay, Mike. My legs grow longer every time they get pulled. Here is another little off-topic challenge for the electrical and maintenance types. It is a question on motor control wiring that I wrote years ago based on an actual event, too long except as an attachment.
 
Can't help it... I love games...

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There's an interesting side-effect in this design... at least in the Control Room...

Assuming that neither of the lights is burned out, this configuration presents some immediate diagnostic information just by watching how the lights behave. If we assume that the wiring is intact (this is a reasonable initial assumption) and that failures might occur in the devices only, then...

While the pump is off, the Red Light should be on... if not...

- Aux-2 is stuck open

If the Red Light is on, then, when pressing the Start Button in the Control Room, the Red Light should go off just after the Green Light comes on. If the Red Light stays on and the Green Light does not come on, then...

- there is a problem in one of the Stop Contacts or the Control Room Start Contact.

If both lights are on while holding the Start button, then...

- the mag might have tripped out (check the over-loads), or...
- the mag coil is burned out (verified if the over-loads are OK), or...
- the Aux-2 contact is fused closed (verified if the pump is running).

If, while holding the Start button, the Green Light is on and the Red Light is off (the mag-coil is working), and then, after releasing the Start button, the Green Light goes off and the Red Light goes on, then...

- Aux-1 has failed.


Only after performing the light-tests and then verifying that any suspected devices are not faulty should you consider that there might be a break in the wiring. Running down a broken wire is a pain in the a$$... and is also the least likely failure.
 

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