Sequencing

need to develop a simple system where a fixed no of inputs can be given an order and controlled sequential order of output bits. Is there an instruction set in Function Blocks to perform this. I have up to 6 inputs and need to be able to give them an order of sequence and then give outputs in a sequential order.I am using an Allen Bradley Control Logix system.

Sheethal

This sounds like a FIFO (first in first out) application,

I'm not an allen bradly user, but heres a link to a thread on FIFO.

http://forum1.automationdirect.com/board/Forum1/HTML/001054.html

Hope this helps some

Mike

Do you mean one of your input start your squence or all of them in line?

One input trigers the sequence, and also the outputs are based on individual inputs.

OK

Why not to use move instruction when the input is On move the value of the input word to the output word.You will have to do it not directly.
becuase you only have 6 input and outputs.

I think you should check this : http://www.plctalk.net/qanda/showthread.php?s=&threadid=5278&highlight=Hundikoer

BR
Lauri

Actually I dont think FIFO, MOV or any of those are needed...if I read and understood correctly.

First off will the input that triggers the sequence stay on all thru the sequence? This will affect how the code is written. Lets say it does.

Trigger input comes on and latches a sequence start bit.

NOW create a rung for each output with the sequence start bit first then the necessary inputs to latch that output..ie to latch first output then start bit ON, input 2 ON, output 1 ON. This can be modified to include input 3, 4, 5, 6 etc if you DO NOT want it on if another output is on.
Example:

This is simple and doesnt need anything but contact/coil type instructions. Shouldnt use more than 6 rungs or branches. Easy to understand. There could be other conditioning needed to make sure the process stays in sequence but that you would need to work out or offer more details.

This kind of stuff I can do no problem, even if you need to add time to the sequence it isnt that hard.

I just hope I was able to be understood...ie I explained it in a manner that could be understood.

Let me know if I misunderstood and my idea wont work.

Ron
If I unerstand what he going to do he going to use sequencere function
in that case one bit step forward the sequncere evry time.
the inputs change during the cycle and he dont want to write it again evry step.That what I would do.

there is a standard function block available with modicon's plc programming software - pl7. here its described as drum controller where a complete bit table available for 16 consequtive steps operation in combination. it depends on you how you address the input bits & associate with outputs.

its similar to mechanical cam arrangement. u can also make a derived function block accordingly.

regards

Tried & Tested & in use everywhere

Here is a simple ladder using one timer to sequence the outputs. If the start input is momentary, add a branch around the cycle input for XIC T4:0/EN to keep the timer enabled. (make sure to add a Stop input.)

For more outputs, or a longer sequence time change the Preset time.

Another option used is change the timer preset to 1 second & when done do a bit shift to a register, then XIC your CFG input & XIC a bit of the register shifted to enable an output. When the operation stops, write 0's to all register bits.

[The last output below should be O:3/3 for Pump 3. Cant QuickEdit a photo here.]

Greg, cnrservices, explained what I was saying better and with a picture. To me this is easier to understand and physically troubleshoot for the most part. Yes there are instructions or other ways to do it but as a maintenance/service person this is, for me, the easiest method to understand.

Just my opinion, the actual design depends on..........

Are you thinking of the Sequencer Out function? (SQO)

It's great for Traffic lights among other things.

RSLogix Instruction (Warning Large PDF File)