Need Help on programming

Hello Experts,

please help me out on programming.

inputs

tank full float switch
tank empty float switch

outputs
inlet solenoid
drain solenoid
mixing pump


Sequence starts with start button.

empty the tank
fill the tank
run mixing pump for 10 minutes
drain again
stop the sequence.

Try writing it out... then make your program

1) close solenoid and fill tank
2) fill tank until float is reached
3) turn on mixer for 10 min
4) bla bla bla

Then after your sequence is wrote convert that into ladder logic

Try thinking of it as a series of 5 steps.
Step 1 is waiting for the start button.
Step 2 is draining the tank.
Step 3 is filling the tank.
Step 4 is mixing.
Step 5 is draining.

The system must always be in one of the steps, but it can't be in more than one at the same time.
Which outputs are on at each step?
What conditions must be true to make the transition from one step to the next?

there is no conditions between the steps

there is no conditions between the steps

Click to expand...

Correct, but when the sequence is in a step there are conditions which make it possible to move from one step to the next.
For example, if you are in step 1 the condition to move to step 2 is that the input from start button must be true.

Not much happening for me today...haven't written code from scratch in many years...do you make sense of attached?

Program Question

@jtteresinski I like your code a lot. If I may ask, how come you use binary outputs instead of actual outputs on your initial rungs? I've noticed many programs at my plant are also set up like this, having one ladder with binary outputs, then a second ladder with the physical outputs.

Thanks.

I dont want to answer for jtteresinski (I agree nicely written) , but I do the same... for several reasons

1) outputs for me should be last as you can have several conditions of the scan affect the condition of the logic

2) large programs I know where to find my outputs and really large will have their own sub-routine

3) keeps it cleaner, I can have several rungs that will latch and unlatch a bit but the work is done at the end

4) small programs I write the known's inputs, outputs, timers, counters, etc then fill in the blanks

Here is an example of the way I typically write sequencing logic.

Thanks for compliments.

The main reason, as @geniusintraing stated first, is that I learned, both through trial and error and then instruction, outputs last! It is likely you will have more than one condition to turn on an output...so if you turn it on in rung 5 and then realize later in the logic you need it on again because of a reset sequence...things can get confusing..both for you and anyone that needs to get into the code later.

I was brought up in the SLC500 world when I learned programming and if you had the same output in 2 or more places in a program, then only the last one worked. The newer stuff (contrologix, etc.) can maybe do this?

I've programmed a fair # of machines using this type of "step" method...it's made sense to my simple mind and I've found it easy to navigate and find where/why machine is stuck as have maintenance personnel that I have reviewed it with.

I don't think there is one right way...every machine is different as is every programmer. Find what makes sense for you.

Where I am know I am a Machine Tester...verify custom equipment meets customer specs., debug, find issues (mechanical, electrical, program) and the controls group here programs in State Logic (if step done, then move 10 to state, if = 10 then do something, when done move 20 and so on)...I hate it! Though it really isn't that different than what I am doing.

I am very much a newbie to programming. I think I have done it a completely different way. I’m happy to take comments/criticism.

Thanks

This is close, but I think the drain step will only happen 1x (after the mix is done), the way I read it?

The sequence was drain, fill, mix, drain.

Thank you for the feedback. I thought that it would automatically drain again ?

Thanks