washing machine

Hello I am new to this forum. Currently on my adv. plc class and Im writing a program that shows how a washing machine works. I already have the sequence of ops:
-1.0ff
-2.fill
-3.agitate
-4.drain
-5.spin

my problem is now having this op. run on the PLC
FYI:im using rslogix 500
any help is appreciated thanks

Welcome to the forumn. You are in the "advanced" class?

Could you share with the group what you have done so far, and exactly where you are stuck?

Do you have an I/O "map"?

I would add a fill after step 4 so that the soap can be rinsed off the clothes...

You should expand a bit on your operational sequence--think about what is happening and why. Take some time to watch a washing machine and take note of what happens in each step of the cycle from an I/O standpoint, and figure out what makes the sequence advance to the next step. Incorporate your findings into your operational sequence.

I guess I am lost with what you are asking

I would use what I call a "state engine" to control this process.

Go to a binary data table and pick out a block of 16 consecutive bits that will each represent up to 15 mutually exclusive states (I normally reserve bit 15 for a state change indicator).

Then, the core of the program will look like my attachment.

I used internal bits for everything, so those will need to be changed to real I/O addresses, and the processor type needs to match your actual SLC...

Paul

Okie, I've not seen a step by step process controlled that way. That's pretty cool, thanks for sharing.

If you don't mind Okie, will you (or anyone else for that matter), please post your file in PDF form. I'm curious about it but I only have RSLogix MicroLite here at home and can't open it as is. Thanks.

shoelesscraig said:

If you don't mind Okie, will you (or anyone else for that matter), please post your file in PDF form. I'm curious about it but I only have RSLogix MicroLite here at home and can't open it as is. Thanks.

Click to expand...

Here...

Paul B said:

Okie, I've not seen a step by step process controlled that way. That's pretty cool, thanks for sharing.

Click to expand...

That construct is a very easy to understand and very predictable way to write logic for machines that can have not too many states, and can have multiple paths between states. It is easy to take a hand written state diagram and turn it into PLC code that way. When you read the logic at runtime, it is easy to see what state the machine is is, and what transitions can cause its state to change...each arrow on the design document becomes a branch in the state control section of the code.

If there are more than 15 states, you can replace the CLR instructions with FLL with a source of 0, and a length of however many words you need to track the total number of states.

I normally map the inputs to internal addresses in a separate subroutine, put the state engine logic in its own routine, and put the output driver logic in the last subroutine to keep things more organized.

It is probably a method that all instructors should teach. On top of learning the basic instruction sets, the student should be taught how to write clean organized code, and that style is one of the most basic examples of that.

Paul

While I use a similar concept your layout is a LOT cleaner than my programs. I'll think about your method on future programs.

Slick, Paul I like this layout. Not bad for some of these small machines. I do like this alot better than SQO for some small state machines. I will have to keep this in mind on the next system.

Paul You had to have this done before or atleast given it some thought ahead of time. 44 min. total editing time

JeffKiper said:

Slick, Paul I like this layout. Not bad for some of these small machines. I do like this alot better than SQO for some small state machines. I will have to keep this in mind on the next system.

Paul You had to have this done before or atleast given it some thought ahead of time. 44 min. total editing time

Click to expand...

I had a blank state engine to start with, so it took very little time to add step conditions, comments and delete the extra states.

The SQO is great for machines with a lot of steps that always go in the same order. It is especially useful when you need to alter the sequencer "pegs" for different products, you can save a copy of the data and reload it for a variety of different functions.

I never use the SQO instruction any more. I always just use the MVM with indirect addressing. That way, it is easier to step forward and backward or otherwise force the sequencer to the step you want for fault conditions, etc.

The SQI, I replaced with MEQ with indirect addressing too. I really like the SQI/SQO concept, just find problems with the built in advance mechanism. If an SQI instruction causes the sequence to advance, and on the very next scan, all of the conditions are already met, it won't advance again. Using the MEQ/MVM setup with a home-grown step advance/reverse integer solves those issues.

Are there ary tutorials online dealing with stuff like learning to work with indirect addressing, and stuff like SQI/SQO, MVM, MEQ and such?

I'm just beginning to learn PLC programming, but coming from a background as a bit of a crappy hobbyist computer programmer, I have a decent understanding of the concepts. I just need something to act as a referance/help guide for when I get stuck/don't know what to do. The biggest hinderance is just getting used to the PLC system, how things work within it and such.

Anyway, sorry to sidetrack the thread a bit, but it is still related to this sort of thing.

wow thanks guys really appreciate all the input.
sorry BlueByu, the class is called PLC ADVANCED. so far we hav learned everything from sequence of operations to timers and counters in the plc.

I agree Paul/okie gave some of us a lot of information with a washing machine logic. Thank You Paul.
yet the best learning experience is to get trown in with the wolfs, and everyday practice,yet i'm still very far away from the experiance that Paul has, I belive every day practice will get me there soon.
Thanks Again