Ladder logic diagram

Join Date
Apr 2021
Location
Ohio
Posts
1
I'm the beginner.
Can anyone help me draw ladder logix diagrams with this? Thank you!

1 . A part is placed on a hook conveyor. The part automatically moves down the conveyor. In the middle of the conveyor, the part goes through a painting booth. The sprayer paints for the time the part is in the booth, during which time the conveyor does not stop. The part then goes through an oven, another paint booth, and another oven. When the part reaches the end of the conveyor, the part is removed. The parts are all metal. Make a ladder logic program that will operate the above specifications properly. Include an 1/0 diaaram.

SmartSelect_20210422-025219.jpg
 
If you are a beginner, your tutor must have given you examples in class on how to approach these type of problems.
Read the question, and make a start on what you think you can do.
Compile your I/O list like it says.
Write the sequence of events like a bulleted list, if you need to.
Only when you have made an attempt at what you think is required, would anyone here assist you in guiding you past the part(s) where you have made an error.
Best of Luck - we all had to start somewhere..!
 
You want help? Programming is about learning to think like a PLC; PLCs are not very complex, so it is not hard; here is my attempt to help you think like that.

This is a word problem.

1) Break it into individual parts: inputs and outputs, because those are the only devices that the program will interact with. Everything else is a distraction, for example, the fact that "The parts are all metal" does not matter very much to the PLC or to the program, so you can ignore that. The color of the paints does not matter, so you can ignore that.

2) Now group those inputs and outputs into individual tasks by asking questions such as "when should paint sprayer 1 be on," or more specifically "when should paint sprayer 1 change from off to on, and when should paint sprayer 1 change from on to off?" Also note any interaction between tasks, for example, "Should paint sprayer 1 run if the hook conveyor is not running?" Because of interactions, some inputs and/or outputs may appear in more than one task.

Gather the list of inputs and outputs from (1) above, also the individual tasks, the tasks' questions, and the tasks' questions' answers from (2) above, and put them in another post here. Then, while you are waiting for more help responses, look at these links:

It is only ones and zeros, it cannot be hard.
 
Last edited:
I would not submit a bid to program that system based on the description and the picture provided. Too many unanswered questions. For example, what are the functions of LS1, the reset PB, and PL1? Are "Automatic", "Pilot Start" and "Stop" pushbuttons wired to the PLC? How does the programmer know the time that the part is in the paint booth? What to do if a part is not removed at the end?
 
I would not submit a bid to program that system based on the description and the picture provided. Too many unanswered questions. For example, what are the functions of LS1, the reset PB, and PL1? Are "Automatic", "Pilot Start" and "Stop" pushbuttons wired to the PLC? How does the programmer know the time that the part is in the paint booth? What to do if a part is not removed at the end?

I read it as the conveyor turns on and continuously runs.

edit - It doesn't really even say to control the paint valves or anything else. Pretty sure I'd fail the assignment by being a smartass.
 
Last edited:
Let's start a pool for which post the OP will finally post another comment; there are sure to be some random number smarta** comments from now 'til then.


I'll start it off by taking #42; DON'T PANIC
 
When I went to college my fraternity had a big file cabinet with copies of past tests in most of the core courses. The professors were generally lazy and recycled the same questions over a period of a few years, so chances were pretty good we had most of the actual questions as well as knowing what concepts they thought were important enough to put on the test. I'm sure that filing cabinet was worth at least a half point on my GPA.
 
Ironically, I did a system like this in 1984 on a SqD symax system, the one I did was a bit more complicated, the conveyor was very similar, hangers for lorry wheels, however, there were something like 10 stations where the hangers would accumulate the idea was there were 10 hangers in each station, when the station in front released one the station before it would release one & so on, there was a loading station the operator placed a wheel on the hanger, and enter the wheel type number, this proceeded down the loop into the first spray booth where a robot would spray the primer (I think it was a Trallfa 4000 series half a megabyte of bubble memory wow!), then onto an oven, another spray booth, another oven etc. we had to track the wheel from the loading to the final spray booth so the robot could determine the wheel type. & to be honest, we had about as much information as in this post.
 
Remembering SQD Symax late at night

Parky:

I did a LOT of Symax work back then. Got referrals from 3 Square D distributors. The stuff was a real technology leader for a short period after AB PLC-2 and before PLC-5. I did a system with some UV-Prom model 300 CPUs. 30 years later they've changed I/O modules and power supplies but the CPUs are still going strong. SyNet had leading-edge routing options. They really got a lot of horsepower out of the processor on the 300s - I think it was a Z-80.

Square D made some architectural definition errors and they lost a lot of their momentum and good people from a company relocation and buyouts. AB got more real performance out of 57.6 kbaud than Square D got from 500 kbaud. Symax was too quick to go to market with an Ethernet CPU. They made their design decisions before TCP/IP and twisted-pair cabling. They also were at a dead end with their fixed register configuration. The PLC-5 ran over them with configurable data table.

It seems that each of us gets our basis from what we had to work through when we started out. You can tell a Fortran guy when he starts variables with I, J, and K. An old DOS C programmer will be paranoid about large local data arrays since he was fighting a limited stack size. Older PLC programmers are much more carefull about packing data to get more out of each communications exchange. I still look at a lot of things through the eyes of a Symax programmer - will the math blow up over 32767, etc? Do I have to worry about alignment on float variables? Am I properly managing one-shots?

Symax got me started on a career that has covered well over 30 years so far and is still going. I'm glad I worked on it and I am glad to have met many of the people that were involved in it. I was blessed to write the first generation of PC interface software for the PowerLogic circuit monitor. Much of what I teach today has a basis of thinking through Symax.

Parky, don't forget the joke about the old bull and the young bull going over the top of the hill. It can be pretty real sometime. I had one time when two young electricians had spent a couple of hours trying to get a burner control going. I walked in, found a bad 5-volt regulator, asked for a cell phone charger, and strutted out of the control room in less than 20 minutes. A definite old bull moment. Us Symax programmers get them occasionally.
 
Yeah, I had a couple of those, one where a well known food manufacturer had a de-palletising system, their engineers spent 2 days when it stopped, I travelled 150 miles to site, spent 2 hours getting in (usual H&S stuff), went to the plant, adjusted a photocell & off it went. Some very embarrassing faces, I was then given a 3 month contract to add a simple 2 digit display for alarm numbers with a printed list, spent the rest of the time sitting by a canal that ran right by, my job was to wait if a problem appeared, monitor what the engineers did & every friday report findings to head office, then another order to do some training of the engineers. Another one was a 200 mile trip to a Pick & Place machine, got to site, saw the problem, removed an exhaust filter off one of the banks of solenoids ^& off it went, I suggested they order some new ones & left site within the hour.
 
Just got to question why the empty hangers have to go through the oven again on the return journey ???

Why can't educators come up with real-life situations, that have a practical purpose, that are used in industry, that are proven to work given correct coding, that will actually be beneficial to the students.

One of my training "aids" is a working model of a dumb waiter (food lift).

The first part of its use in training is to tell students I have forgotten the I/O connections (a blatant lie, but so-what?), and they have to discover them. They have to get that correct so that the next part, the control code they devise, will work.

The only specification given is that it has to be usable in a restaurant, it is up to the students to devise their own control philosophies. The "usable" specification makes people think harder, longer, and more outside the box. I call it a "stretch exercise".
 

Similar Topics

Hi there! I am new to PLC's, and I have undertaken the task of converting a primarily pneumatically-operated machine to electrically &...
Replies
5
Views
2,617
please help i didn't solve this problem with rslogix. I counted but i am not using timer. How i will fix this situation? Please anyone solve this...
Replies
18
Views
4,874
Hello, I am a beginner with PLCs, so I am new to the ladder logic diagrams. I need help with the following: 1:When switch one (SW1) IS CLOSED, THE...
Replies
25
Views
5,383
I need someone help to write a ladder logic in PLC 5 to take an average of 8 input values within 2hrs of an analogue input connected to channel...
Replies
12
Views
7,370
hello all masters PLC, :bow: :bow: :bow: I want to ask something about fuzzy logic. how to apply fuzzy logic into the ladder diagrams? 🤞🏻
Replies
9
Views
6,118
Back
Top Bottom