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plcnoobie

RSLOGIX500 Help

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Hello, i'm doing a PLC industrial project assignment using RSLOGIX500. Basically, there are 6 cylinders and we have to move the blocks in a sequence. I've used SQC and SQO. The catch is my professor said no timers are allowed to allow the sequence to continuously run. Here is where i'm in a hole; I do not know how to make my plc rung to run without adding a timer. I'm open for any suggestions. I tried adding a counter, but I always have to manually toggle the counter bit in order for my cylinder outputs to advance/retract. Edited by plcnoobie

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I'd use one of the built in internal clock pulses to trigger your sequencers.....

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Hello Do the cylinders have sensors to detect whether the plunger is completely extended or completely retracted? If so, use them (the sensors)

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I like FilterWolf's idea - you'll find the free running clock in the status file - just choose one of it's bits that toggles at a rate you like and use it. Also, it might help if we had more information. For instance, if you have 6 cylinders to move six blocks in sequence, as Chantecler pointed out, you would typically use cylinder #1's "completely extended" switch or sensor to trigger cylinder #2 to extend, and when cylinder #2 is fully extended then it would trigger cylinder #3 etc. So they would "cascade" from one to the next. PS - You're correct in that a counter needs a false to true rung transition to count up. However, you can use the ADD instruction to count up "once per scan" (ADD 1 N7:0 N7:0) just be sure to zero it out before it exceeds 32767 or you'll get a math overflow fault (GEQ 7:0 32000 MOV 0 N7:0) Hope this helps!

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I believe the whole point of this exercise is that NO timers, counters, clock signals etc. are needed.... The SQC instruction reads the input states and when matching the expected or desired pattern for a particular stage, it triggers the SQO to move to the next stage. Think of the SQC as a "group feedback", testing "what I want the inputs to be after the last SQO state" Triggering the SQO from anything else, ignoring the feedback from the field devices, could cause chaos. Edited by daba

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