8 output SLC Sequencer help Pls

[chrisf 0]

Hi All, I need a little help here, i can program a sequence using lots of timers, but what i really need to do is have a one shot input which will step to the next output on every press of a button. i.e. one power up start at output 1, press button step to output 2, press button step to output 3, this goes round in circles thus, 1,2,3,4,5,6,7,8,1,2 etc. Any help on a simple approach to this would be most grateful, any available code for this to suit the SLC would be just wonderful. Regards Chris

[kaiser_will 65]

This sounds like similar to a "state machine". An input changing state, such as a pushbutton, with a one shot bit, moves a constant into an integer (such as Step1=1). Next rung has a test for Step1=1, then execute a change (like turn an output on). The next rungs, with the output on and Step1=1 then increments Step1=2, and so on. At the end of the sequence, reset Step1=0 to be ready to loop again. Here is a quick and dirty example. What is your goal in such a scheme? I use state machine logic, such as this, for a system that has many sequential steps and to make it easier for the customer to follow the logic/troubleshoot. StateMachine.ACD

[Ken Moore 23]

You did not mention the platform, but take at look at the download section: http://forums.mrplc.com/index.php?autocom=downloads&showfile=638 See this post as well: http://forums.mrplc.com/index.php?showtopic=9159

[chrisf 0]

Thanks Kaiser_will, This is to operate 8 valves in sequence, only 1 open at any one time and to keep rotating. I will be using various timings due to various conditions and if valve faults exist, thats why i am going for the step to next valve approach. BTW i cannot view your attachment, what format is it? My PLC platform is the SLC500 5/03 cpu Regards Chris

[Marek32 0]

Did you try the SQO function, it looks just for your aplication sqo.doc

[BobLfoot 302]

I remained silent for a while since I wrote and posted the 48 step sequencer. I have always found the AB SQO sequencer approach to be obtuse and difficult to follow and debug. I prefer a roll your own sequencer or state machine for these types of situations. Good Luck whatever approach you take. The folks here at mrplc will be glad to critique and review your work.