nudge in the right direction

Hello everyone i'm recently new to PLC and i'm working on a garage door simulation and i am stuck. I'm have been trying for the past 4 days to get the garage door to stop while the door is in motion if the open/closed buttons are pressed and released. I'm sure i'm just making it harder than it actually is. If somebody could just point me in the right direction i would greatly appreciate it.

And i cannot use any output latches.

Haven't looked close but I see in rung 000 bottom branch has N.O. and N.C. instruction with the same address, effectively rendering it useless.
Please clarify what this means.

Snip...

I'm have been trying for the past 4 days to get the garage door to stop while the door is in motion if the open/closed buttons are pressed and released.

Click to expand...

Does it mean when the Open AND Closed buttons are pressed at the same time while it is going in either direction?
Does it mean when the Open OR Closed buttons are pressed at the same time while it is going in either direction?
Either way you might need to add another rung to handle this.

you need to check the previous threads or the download section of Flip Flop,
you can do this without using latch/unlatch cmds
Use this control for the up button and duplicate it for the down button.
the Limit switches can be used in both the output cct as well as the up/down cct.

Also - check your contact nesting
use 'right click' - branch down or up
Dont use the bridge like you have now.

One possible reason since this is a simulator - what activates the limit switches?

Also I think I would take second look at the stop switches.

You only wanted a nudge so wont say more.

Dan Bentler

Thanks for the hint and what program do i need in order to view the flip flop download file?

For those scratching their heads about the seemingly dumb questions, the actual LogixPro Door Simulator, Student Exercise #4 can be viewed here:

http://www.thelearningpit.com/lp/doc/dl/dl-rl.html

The LogixPro Door Simulator student problem has been solved here many times before. Look in the "Downloads" section of this site, where there are many solutions. I know that the file "LogixPro DOOR_OPENER_EX_4.rsl" will work, because I wrote that one way back in 2007. I see that it has been downloaded over 4300 times now! I am sure there are other correct versions.

http://www.plcs.net/downloads/index...ey&PHPSESSID=412a934a4ad3a468446863a558e91386

Basically, the method is to use the SAME pushbuttons (the OPEN and CLOSE) to do TWO functions, Open or Close under certain conditions, and STOP under other conditions. PLCs can do that easily. Remember, each pushbutton input can be used in your PLC program as many times as needed (unlike certain Outputs).

Can you figure out some logic that uses (say the Open pushbutton and some other input), to halt the door if it is traveling in the Closed direction?
Can you figure out some logic that uses the Close pushbutton and some other input), to halt the door if it is traveling in the Open direction?

PS: You can use a flip-flop circuit, but it is not really needed in theis case, only some "flagging" relays, as mentioned in the big HINT in the actual problem. Ah, if only they would read and understand, how easy the problems would be!

I found your solution and it does work but the only problem is that i can only use the XIC, XIO and OTE contacts and nothing else you used a OSR contact which i'm not permitted to use yet.

Jose,
There are ways around the OSR. You can write some logic using OTE, XIO and XIC to create an old-fashioned one-shot without using the pre-defined function.

Anyway, here is a solution using the weasely picky restrictions that you have given. This program does use a Latch BUT NOT ON AN OUTPUT. This is the same one that I have posted in the Downloads section. You must have been looking at SOME OTHER PERSON's solution. This shows a certain lack of observation, and such errors are not good if you are going to work with PLCs and PLC programming.

Jose,

In case you need it, here is a method to do a ONE-SHOT using only normal relays and pushbutton switches. I added a Counter to show that the ONE-SHOT only triggers one pulse for each press of the Input pushbutton. The input can be any PLC or relay input.

Lancie i appreciate all your help man. And yeah my professor has put this stimulation on which is kinda of pain cause it would be easier and more efficient to use a timer or latch output. You are right that his limitation are unreasonable.

Sorry to say this Jose,
You are learning this for future income.
Start from the bottom

Jose,

Think of your instructor's limits as a challenge: How can you use and work around what he has allowed you to work with?

Actually learning to work within restrictions is good training for future real projects. Think you will have your choice of PLCs, an unlimited budget, plenty of time, and lots of other people helping you on real-life projects?

That said, now I do think a lot of instructors are placing those limits on programming not to help the students, but to make it easier for them to check the homework. In other words they only want you to learn certain things at certain times. That is not how I was ever able to learn anything. Learning happens whenever and wherever, and trying to place limits on it doesn't help make it any faster.

You are living in a free society, so if you really want to learn MORE than your instructor allows, the sky is the limit. I never took those limits to heart. I usually had read through the text book by the end of the second week, and once in high school got a "free" pass for the entire 6 week period because the algebra teacher said on day, "this next problem in the book got put in out-of-place. If anyone can work it by the end of the week, I will give them a 100 for the 6 weeks, with no test". I worked it, and goofed off the rest of that period....

I have tought many an apprentice to do the Job with no short cuts.
The easy way comes after they master the task.

Reverse engineering is an amazing thing. I think i have finally found the solution that i have been looking for. Again thank you to everyone who helped me.