Learning PLC Programming & Need Help

Hello,

I have recently started studying PLC programmimg on my own. I have taken & and finished a beginners class, and am studying my way through the basic instructions. Approx. a yesr ago I purchased The PLC Trainer 3/LogixPro Bundle. In my spare time I have been reading all of the text, and working the problems. I am currently working on the traffic light arrangement. Although I have this working, it has two problems that I cannot overcome. The author of the text says that although the program can be written with 6 timers, he says that it can be done much cleaner with 4. I had to use 6. My program almost works perfectly, but one of the yellow lights is not as long as it should be. I was hoping that someone may be able to give be a basic 4-timer program of this traffic light so that I can study & understand it. Without going to another class I have nobody to go to for insight & help with my problems.

Thanks In Anvance!

Mike

Mike,

I have worked out many different solutions and variations of the Logixpro traffic light. I have posted some of them here in the Downloads section. Would you be surprised to know that the traffic light can be done with only 1 timer?

The key to solving the traffic light (as for many other PLC problems) is to make a timing diagram that shows only the basic time cycles. Then it becomes clear that only timers for East Green, ast Yellow, North Green, and North Yellow are necessary. The Red lights are combinations of the other 4.

I knew that I only needed timers for east green & yellow, & north green & yellow. I knew that teh north red would be a time product of teh east green & yellow, and vice versa, but I have spent so much time on this so far I was hoping to study someone else's program so that I could move on in teh text. I am new to this site. I saw a download section, but it looked like it was all vendor stuff (Seimens, A-B, etc ...). I will look a little harder to see if I can find some of your work. Thanks for teh response.

Mike

Look under "AB" then look for extensions with *.rsl thats the LoigixPro stuff

Thanks Mickey!

Mike,

The Smartlight program uses 8 timers, but then it has some additional features, such as delayed green, the pedestrian crossing, and automatic adjustment of light times based on traffic flow. Your basic light should only need 4 timers. Delete all the above features and you got it!