Ladder Logic Program Assistance Needed

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https://imgur.com/a/Sjq3jlF

hopefully this works

I use Photoscape to resize images. http://www.photoscape.org/ps/main/index.php

It has a good batch editor where you can resize multiple images at once. Also, it's good for annotating images.

IrishDave45 said:

I am taking this course to get entry level in maintenance...he has already told us that you would need to be on the job for at least 3-5 years and taken specialty programming courses before the companies even let you near their industrial PLCs so I am not sure why he is wasting so much of our class time on this.

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For a maintenance position, you should understand this sort of thing on day one. Every company has their own expectations and requirements, but this is actually a pretty simple exercise to complete. Just work through it one step at a time as dmroeder suggested. The one thing you don't want to do is try to find a shortcut around completing the assignment. You will only be hurting yourself.

Bubba.

If you can get a printout to pdf then upload that. Also do you need to think about vehicles turning left & right in that case both sets of lights need to be red on pedestrian walk.
You need to first write down the sequences for example:
Step 1 (assume on start both sets are red) this is a good start point.
Think about how the sensors are to work: i.e. if no cars north-south can leave east-west on green maybe two timers for each route one for standard time and one for extended time i.e. if north/south no traffic detected then leave east/west green for longer. also interrupt to normal traffic in the case of pedestrian button press so at end of north/south sequence pedestrian sequence initiated. If it was a case that north/south & east-west had no left or right turns it's easy, however, allowing left/right turns means both vehicle routes must be red. try to plan a flow diagram that will make it easier to start your coding.

For any given homework assignment or task at work, you must consider these instructions as the customers specifications.
1. read the specifications several times.
2. write down your understanding of what you read in a step by step fashion.
3. review what you wrote down and see if it makes since, modify if necessary.
4. step through your notes again this time, you are the one following the instructions.
In other words, you are the plc. Write down on paper the events you are doing.
For example, turn on hydraulic motor 1, write down hydraulic motor 1 on.
If a sensor is needed, write that down.
5. continue through the instructions. When you turn off the motor, mark a line thru it.
6. go through your instructions with all the sensors, motor aux. contacts, outputs
Documented. Modify if necessary.
7. repeat step 6 until no changes are made.
8. Try to group your data words into some organized fashion.
The more programs you write, the more organized you become
9. write the plc program using your notes.
10. install the program and leave in program mode if possible so you can to debug your i/o
11. Question for you, when is a machine and plc the most dangerous and why?
When it’s first powered on – when power is first applied to a machine, you don’t know
How things are wired. When you energize the plc outputs, you don’t know how things
are wired. When the plc is put into run mode the first time, it will do what you told it to do,
NOT what you wanted it to do.
12. debug the program.
13. DOCUMENT EVERYTHING!!!
you may remember things today, but in 5 years and hundreds of programs later, you won't
remember, so DOCUMENT EVERYTHING.
14. MAINTENANCE is your best friend or your worst enemy.
if you work with them and find out what they can do, write the program where they can
trouble shoot the program. they will be able to fix the problem and everyone will be happy.
BUT
if you write the program to where you are the only one who understands what is going on,
maintenance can't fix the issue, the machine is down, production is down, management hears about
it, your boss hears about it, then you hear about it - rewrite the program or else.
you get calls all hours of the day and night.

this still holds true, a machine can cost a billion dollars, but it's not worth 10 cents if
maintenance cannot trouble shoot the issue and fix the issue.

everyone has their own style of programming and you must develop your own way as well.

this is the best advice I can give anyone.
of others has more / better suggestions, feel free to post.

james

Street light logic projects has come a long way since I was in school. We just had to worry about the lights and timers. No additional PB's.

IrishDave45 said:

and he wants a subroutine in this as well...which honestly if I can just get something that will get me a passing grade I don't care about the subroutine. I am taking this course to get entry level in maintenance...

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I'm a little surprised this hasn't been brought up yet so here goes my spin on it...
I take issue with your statement above. I've come to find that this web site servers multiple purposes not the least of which is educating people on how to work with PLCs. If all you're looking for is a passing grade then I'm inclined not to help you. I don't want someone in industry who "just got by" in school when I've spent years learning the craft and paying my dues. More importantly I don't want someone out there making mistakes that could (at worst) hurt somebody. What the teacher wants vs. what you want is between you and the teacher but with all due respect, it's the teacher's job, not yours, to define what you need to learn in order to be considered qualified. Having said that, I do appreciate and respect the fact that you are clearly making an effort to figure this out but I'd much rather see you take this as a challenge and an opportunity to learn something that you will need in the future if you are going to work with PLCs. Look at it this way. Maybe you'll learn more about subroutines on the job, but if you learn about them now, you'll be that much further ahead and that much more of a valuable asset to whomever you wind up working for.
On a related note, (if you aren't aware of this) PLC's generally aren't used in the traffic industry. They have their own set of controllers that, to be honest (at least the last time I worked with them) are much more efficient at controlling intersections than a PLC could ever hope to be. Yes you can make a PLC do just about everything a traffic controller will do (so don't message me about how wrong you think I am) but traffic controllers are specifically designed to do what they do where as a PLC has to be able to so a lot more. So, why use them in your PLC course? Because a traffic light application covers all of the basics that PLC's do and what you need to know about how to use them (which by the way is why your instructor is making you learn about subroutines). Traffic applications have inputs and outputs, timers, interrupts, etc... so you can cover a lot of what you need to learn how to do by using a traffic application as a learning tool. The other thing (that I'm sure teachers know about) is that it's a dead giveaway that someone is asking about homework when they ask about how to program a traffic application.
Good luck with the project and don't be afraid to learn as much as you can while you have the chance to make mistakes without consequences.

Terrible way to teach PLC.

I dislike the majority of plc classes I come across. Most of them take what is really a foundational set of concepts and teach things in parallel.

Its kind of like randomly grabbing Joe-Off-the-Street, dropping him into a wood shop, telling him he has to build a wardrobe using rabbit joints, telling him something like a table saw exists but not letting him get good at using it or hints on when to use it.

Asking a student to develop a logical solution (which may or may not be a requirement of the training he is looking for) while using a tool he is unfamiliar with just seems like folly.

Keith

I agree with the last post. The idea of a lecturer should be to teach the basics like how a plc works in general, talk about scan, memory simple logic like and, or etc. once the basics have been learned then give them a project. I was thrown on-site with a Square D programmer and a manual, however, I had experience in low & high-level languages so not too daunting. I have in my 35 years of plc programming taken quite a few apprentices under my wing and in almost all cases the lecturer at college has failed to walk them through the basics. some have told me they just give you a project and expect you to get on with it. When I had opportunities to teach I took them through a number of boring (well they probably thought so) talks on how a plc works and how they can use the scan, for example, a Oneshot and how it scans, etc. although they were itching to get their hands on the equipment my first words to them was would you take a driving test without lessons? I did get one smart alec said I could do it, funny really he failed 3 times even after lessons.

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So I think I have it pretty much completed except one thing...I need to go from a flashing output light to a steady on output light. I need to create a subroutine to make my do not walk flash for 10 seconds and then latch on until I unlatch it. I just cannot figure this out. I have the flashing part done...but don't know how to make it stop flashing and stay on latched. Any help would be greatly appreciated...I have to have this thing completed by EOD tomorrow and this is all I think I need to complete it.

You can branch around your flashing bit to make the output steady, essential bypassing the bit that is flashing. Don't use and OTL to override an OTE instruction.

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ok but I am not sure how to accomplish that. Right now I have 2 TONs that I am using to flash the output light on/off. But it only needs to flash for 10 seconds and then go steady on "don't walk"..so not sure how to achieve what you are suggesting.

Add an additional timer that is active from the start of the flashing phase and has a 10 second preset.

Code a done contact from the 10 second timer in parallel with the already existing timer contact that is causing the light to flash. this will cause the output to toggle with the flash generator timer until the 10 second timer expired. The 10 second timer contact will bypass the flash generator contact, keeping the output on.

Keith

What plc manufacturer?
And a few more details on your process