Sequential programming

Hello All,

I have a question on how to program a Micrologix 1000. Program is sort of like a pick & place. One sequence follows another.

I program Mitsubishi FX befor and I use the S0, S10, S11, S21 to accomplish this "sequential programming".

How would I go about doing on the Micrologix 1000?

TIA!

lostpatrol1,

If you are using RSLogix500 to program your Micrologix1000, then there are true Sequencer commands available, SQC (Sequencer Compare, SQL (Sequencer Load), and SQO (Sequencer Output). Let me say here and now that I have never found a practical way to use a Sequencer function in a PLC program. I am sure that is because a PLC usually controls a process that has many input conditions that change and cause subsequent changes in the outputs, where as a Sequencer is a fixed set of steps that executesthe output the same way EVERY cycle. So if you are controlling a dishwasher, then maybe a Sequencer instruction is appropriate. That is the only successful application I have ever seen for a PLC Sequencer, but that was for training in a PLC classs at the local community college. Mostly I have seen people try to use it, then find that there are so many EXCEPTIONS to the normal "sequence", that they give up in frustration, and just program in a subroutine (another ladder "File" in RSLogix) for each process condition, and forget the sequencer as being a lot of trouble for not much gain.

Where I have a sequential set of steps to executes, what I like to do is set up "stepper" relays, one for each step of the process. Then at the end of each routine (say Step 1), I unlatch (reset) the relay Step 1 and on the same rung I latch (set) Step 2 relay, and so on until the end. This helps in troubleshooting the program, for is is easy to find what Step it is working on, or in what Step a problem occurred.

Hey Lancie----Where ya been?

I just recently programmed a Pick and Place (PAP) with a ML1200. The typical PAP has a routine it follows from a start point to a stop point so while they may be VERY important to any other sequencing action, input changes may not pertain to lostpatrol's case.

Now here's the "however" part...

...I'm the only guy in our maintenance\engineering team who would be able to follow a sequencer in a program so I wrote it another (longer) way so I don't need to be on sight if the program needs to be accessed for troubleshooting.

Lost...just unwrap the sequencer and program it the long way or go ahead and read up on the sequencer instructions in RSLogix500. If you've used sequencers in other PLCs, you'll be able to sort thru ABs.

If you decide to go the long way I can help you with the details. My program uses an up/down switch to increase or decrease the number of cycles per minute and has a "load" switch since we use it to load a conveyor (rather than unload).

Good luck.

Thanks for the reply..

I am using RSLogix 500 to program the Micrologix 1000.

I'll see if I can use subroutine (one sub routine call another when done) and see how that goes...but I will read up on sequence thing.

TIA!

Hey Rube,

I guess I am just stuck up here in the hill country of Tennessee and don't get out much. Yeah, I am a hillbilly if ever there was one. I suppose that I have never been fortunate enough to have someone pay me money to do one of those Pick and Place programs...Around here, if it is a simple 1-2-3 operation, they mostly have a good old boy in a straw hat standing by a selector switch labeled "1 2 3".

Lancie1 said:

I am a hillbilly if ever there was one...if it is a simple 1-2-3 operation, they mostly have a good old boy in a straw hat standing by a selector switch labeled "1 2 3".

Click to expand...

I'm a converted cow/plowboy myself. I figure I've done enough of it that I can program some of that silly 1,2,3 **** in to begin with. Now if I could just program the flu out of me. That'll teach me to be quicker to the shot doc next year!

Good to hear from you, I knew you'd been missing for a little while.