LogixPro Traffic Light lab

I'm going through the LogixPro labs and like a critique on my solution to the traffic light lab. I know this can be done many different ways, but I am trying to stick with basic TON and TOF timers right now.

At this point, I am just trying to get the basics working with 4 timers instead of 6 as suggested in the lab. I put in the reset bits because I couldn't get the two red light timers to work properly with the green and amber light timers.

Is there a better way to accomplish the basic traffic light operation using only what I currently have?

Thanks!

Hi paac.

I too am going through the LogixPro exercises. My program is similar to yours but not identical. I used four timers but no resets. I have put it in the download section if you want to download it. On this page http://www.plcs.net/downloads/index.php?&direction=0&order=&directory=Allen_Bradley it is the next to the last one on the page. I don't think it is any better than yours -- just different.

Thanks PhilipD. I see what you did. My thinking was similar to yours, but I was caught up in making sure I had a timer for each of the red lights. I like your solution better.

Anyone else have any other ways to do this using only 4 timers?

Old topic but if you are studying PLC's you should be using an updated text book which gives you your answer in chapter 7 and I won't tell you what book but will give you the outline below. Mind you people out there looking for this answer, teachers are getting smarter and adding in a delay on the red lights before the opposite green is coming on. This delay changes this whole outline completely. Do your studying, read the ideas in here, don't put sheeeet off to the last minute and you will get it. I did it in under an hour and my final outcome is nothing like the standard traffic light program below since it requires additional timers for the red and how you incorporate them and tie them into the other colors.

I would like to thank this site for not giving answers, I wasn't looking for an answer to this age old question just a few ideas to put me on track and this site was perfect to help me in that. Plus having my own controller set up at home (hint hint to you that are taking an automated technology course).

Times are not given and arrangement of outputs not given because you have to learn this. I don't want to be competing for a job with young punks. Age will get you the job before I do when all you did was boost your grade by being book smart and getting a great grade on mid terms and finals (Gotta love when lab tests come up and you book weenies fail it). Figure it out on your own and if you have no idea what any of these are below then you shouldn't even be messing with this stuff. Let us that are going to school for it have your job when we are done and those that are already doing this kind of work keep their job.

How to get there thinking with a timing chart
|----------------|_______________Red E-W
|-----------|____________________Green N-S
__________|-----|________________Amber N-S
_______________|----------------|Red N-S
_______________|-----------|____Green E-W
_________________________|-----|Amber E-W


Here is the answer
-------T4:2.DN XIO---------T4:0
-------T4:0.DN XIC---------T4:1
-------T4:1.DN XIC---------T4:2
-------T4:0.EN XIC---------T4:3
-------T4:0.TT XIC---------O:0/0
-------T4:1.TT XIC---------O:0/1
-------T4:2.TT XIC---------O:0/2
-------T4:3.TT XIC---------O:0/5
-------T4:3.DN XIC---T4:0.DN XI0------O:0/4
-------T4:0.DN XIC---------O:0/3

Only have two comments
1. Label all contacts timers and coils for what they do / control. You will be grateful when you get into revisions - I was.
2. Timers in a PLC are "nearly free". I see no reason to restrict number of timers. Seems to me you have to have overlaps ie red (east west) comes on for two second before green (no south) turns on etc. If the assignment restricts you to number of timers then that is what you better do of course.

Dan Bentler

It gets slightly more complicated if you use UK light sequences

Hi Guys,

I'm after a critique of my solution to the traffic exercise incorporating the walk signs. I'm yet to see a solution on the net so i'm keen to know how I did.