Design ladder diagram

Hi I got an exam question saying:

PROCESS CONTROL

Level tank: between 25%-75%
Normal conditions: indicated
Low Level: indicated
High Level: Indicated

1. Draw a Ladder diagram using above info.

Someone please help with this one. Thanks

We won't do your homework for you -- and we're sure not going to take your test for you.

Now, having said that, this is a test. It will NOT be about something you're not supposed to have already learned in class. Show us what you already have and we'll help. Ask a specific question and we'll answer it.

bravic5 said:

Hi I got an exam question saying:

PROCESS CONTROL

Level tank: between 25%-75%
Normal conditions: indicated
Low Level: indicated
High Level: Indicated

1. Draw a Ladder diagram using above info.

Someone please help with this one. Thanks

Click to expand...

I´m not going to do your homework, but think about how you can do it in your own words, then write down that in ladder language. For instance, if low level is set, then inlet pump must be on to refill the tank until high levet is set and son on.

Moving back to the thread after PM exchange with Bravic...

My intent here is going to be to help guide you to find the solution yourself. To teach you the procedure that we go through in doing this type of work.

Initially, as I read the exam question, it's not a question at all. So, first, before we start anything, you have to define what you intend your system to do...

The first thing in programming any system, whether it's "real" or "imaginary" (like your test question), is to define your system. We all have to do this, regardless of if we're new to PLCs or if we've been programming for a long time. The only thing that experience brings is that you tend to go through the following process in your head instead of on paper, but you still do it. Even after 20+ years, I still do it on paper if it's a very big system.

Answer these questions:

1) Where does the data come from? In your case, how do you get the tank level and in what format...

2) What are your expected results? How do you detect them?

3) Is there a sequential process? If so, define each step. Also, define your "trigger" for transitioning from step to step.

4) What are your system inputs?

5) What are your system outputs? What conditions turn each output device on? What conditions turn each device off?

6) How does the operator interact with the system?

7) How are alarm/fault conditions detected? How does the operator know? How are they cleared?

8) Anything else you/we might need to know about your system??


Write these things down.

If there's a sequence, show a flow chart of each step.

Come back with this type of information and we can proceed from there...

OZEE - you have gone above and beyond.

As I read it the problem could be interpreted as simply as:

Use 3 indicator lights, one when lower than 25%, one when within 25% - 75% and one when above 75%.

I agree with Bernie. It's just three lines. No control was asked for or implied.

You're both right. Part of my answer is prefaced from PMs with him out-of-thread. Yes it's beyond what he was asking, but I'm just trying to help him LEARN to do it himself. To learn the process that we go through. Teaching him to fish instead of giving him a fish...

And I'm not convinced that's the whole question. It may be. But where it says the level is "indicated", does that mean it's a condition (input) or an action (output)??