LogixPro British Traffic lights

Hi, I was just wondering if anyone could help me out with a bit of a problem I'm having. I know there is many solutions on the internet for the logixpro traiff lights however, I was wondering if anyone had a solution or could help me find one.

Basically I need to find a way of doing the following (I am a total novice at PLCs).
Red light 5 seconds
Red and amber for 5 seconds,
Green 5 seconds,
Amber 5 seconds, and then back up to red (to remain on red whilst the second set of traffic light goes through the same process as above).



I would be very grateful if someone could help me with this as I am at a complete loss of how to do it.

Start with one of the other traffic light solutions and go from there, play around with it. You will learn best by doing and you can't hurt anything - it's just a simulation ;-)

Hi thanks for your reply. I have been trying for this past day and I really haven't got a clue...

Dose anyone have a possible solution?

Possible solutions are in the Downloads section. To get there, Click on the "Downloads" button near the top left side of the screen. Next, Click on Allen Bradley, scroll down to any LogixPro traffic light file, download it, then open it with your LogixPro software. Modify it to meet your requirements. Zip and post your efforts. The forum members will guide you to the necessary changes but you must make an effort.
Of course if you want to start from scratch, open a new file, make as many rungs as you need, one for each output condition. Then add timers for the amount of time you want that condition to exist. There's more but that should get you started.

Take this comment how you wish but only advice is meant.

Copying someone elses solution will not teach you what you are supposed to learn from the assignment. If you have not yet learned/been taught the fundamentals then maybe you are not ready for the traffic light task.

You need to build your understanding and work your way up. The first step is defining what is required.

My advice is to start with a pen and paper and write down the sequence required for the traffic lighs as a kind of flow chart i.e. Step 1 all lights red, Step 2 ..., Step 3 ..., etc Step XX return to step 1.

I've been designing and writing software for 30 years and the pen and paper is always the starting point.

Nick

I was wondering if anyone had a solution or could help me find one.

Click to expand...

Yes, I have many solutions using different methods. I can help you find one, but first tell us ALL the rules and instructions that you have been given, not just what you think are the basics. It does make a difference. Here is how it usually goes:

Me: "Using a sequencer and a timer, your program can be done in 2 or 3 rungs".

OP: "What is a sequencer? I can use that. We haven't studied that yet".

Me: "Using a timer and some comparison instructions, your program can be done in 6 or 7 rungs".

OP: "What are comparison instructions? I can use that. We haven't studied that yet".

Me: "Using a timer and some XIC and XIO instructions, your program can be done in 6 or 7 rungs".

OP: "Our instructor said we would need at least 4 timers. I have to use that. We haven't studied how to do it with 1 timer yet".

It will save everybody a lot of time if you give us ALL the rules up front, instead of having them pulled out 1 at a time.

A timing diagram always help to show the real cycle of the traffic light.

I think this is your 20-second timing cycle, as best I can tell. I found that you need to set the "Scans" rate to about 50% to prevent crashes due to cars running the yellow lights.

Red light 5 seconds
Red and amber for 5 seconds,

Click to expand...

This indicates that your total RED time for each direction is 10 seconds, which means a total cycle time of 2 x 10, or only 20 seconds. Why did you use a 30.7 second cycle time in the program that you sent?

I think this revision of your Amendment 1 program would be closer to your instructions to have RED lights with 10 second ON times (with a total cycle of 20 seconds). This version will run at 100% scan speed with no crashes.

Increasing your cycle time so that the red lights are each ON for 20 seconds (and greens are ON for 15 seconds) means that you must have a 40-second cycle. Your program should look something like the attached file.