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Old April 26th, 2009, 08:09 PM   #1
Anthonywade
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Exercise #3 Traffic light with delayed green

I am having problem is here what i has .I need 1 second period when both direction will have their red light illuminated threr sre actually 2 such 0verlaps that need to be acconted for
Red=O:02/00, Green=O:2/02, yellow=O:2/01
Green=O:2/06, Amber=O/05, Red=O:2/04
Green 8
Amber 4
1s
8 sec
4 sec
1s red
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Old April 26th, 2009, 08:20 PM   #2
Tango7
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Exercise #3 - Traffic light with delayed green

Anthony;

I would be glad to help you out, the code does not sound that complicated. I am confused though as to what exactly you need the logic to do.

By the title of the message, it looks like this is an exercise for a class in ladder logic. Perhaps you could type the question exactly as it appears in the assignment.
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Old April 26th, 2009, 08:41 PM   #3
Lancie1
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Tango,

It is the old traffic light program. It has been solved, discusssed, debated, and condemmed on this site for years and years. Surely with a little searching, AnthonyWade can find what he needs.

I will give him some little hints anyway.

1. You can use 6 timers (1 will do), but remember it is a cycle, it should continue to loop. You never want your lights to stop working. When your timer T4:5 finishes, that is the end of cycle and T4:0 should be reset and start the cycle again at 0 seconds. The easiest way is to put a T4:5/DN XIO on Rung 0

2. Go back and do what you should have done first, that is to make a timing diagram showing what time each color light goes on, and what time it goes off.

3. Now look to see if some lights can be defined as combinations of other lights. For example, the red lights should be controlled by just two different timer DN (Done) bits (in series for one red light, in parallel for the other one), while all the others can be controlled by a different single TT (Timer Timing) bit.

4. You are shooting for a 26-second cycle, so set your timers for 80, 40, 20, 80, 40, 20. That gives a 28 second cycle, but the extra 1 second for each Delayed Green results in no crashes.

Last edited by Lancie1; April 26th, 2009 at 08:49 PM.
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Old April 27th, 2009, 01:10 AM   #4
Anthonywade
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Exercise #3 traffic light with delayed green

Quote:
Originally Posted by Tango7 View Post
Anthony;

I would be glad to help you out, the code does not sound that complicated. I am confused though as to what exactly you need the logic to do.

By the title of the message, it looks like this is an exercise for a class in ladder logic. Perhaps you could type the question exactly as it appears in the assignment.
This is from exercise 1 and 2 traffic light, than my instructer want me to modify this one.
Modify your program so that there is a 1 second period when both diresctions will have their red light illuminated. Note that threr are actually 2 such overlaps that need to be accounted for.The timing diagram belows the six discrete timing intervals required to accomplish wiyh desired sequence of operation, and wiyh proper cascading you should be able to come up with an easy to follow solution using just 6 timer.
Red=O:02/00, Green=O:2/02, yellow=O:2/01
Green=O:2/06, Amber=O/05, Red=O:2/04
Green 8
Amber 4
1s
8 sec
4 sec
1s red
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Old April 27th, 2009, 11:07 AM   #5
Controls_Engineer79
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6 timers?
Anthony - you can do this with a single timer that resets and cycles continuiously, and then just use compairson instructions to turn on your lights at cirtain time periods within that cycle - i remember that assignment from my student days, except in our case we had to design the program using as few rungs of logix as possible and only a single timer
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Old April 27th, 2009, 10:00 PM   #6
Lancie1
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Quote:
It has been solved, discusssed, debated, and condemmed on this site for years and years. Surely with a little searching, AnthonyWade can find what he needs.
Search for "traffic light" right here on PLCs.net. The Delayed Green is no problem with 6 timers.
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