Need help with a question in PLC homework

msk

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So ive chosen the first option. Is it correct? it would be helpful If i could get an explanation too. thanks

2.jpg
 
obviously SK has better eye sight than l,
otherwise l could possible answer.
if it was me, l would look at ; posted/preview and then go post
 
But this is kinda vague and depends on what is meant by 30s after startup. The steps in SFC also have prebuilt-in timers you can use to transition after a preset time

1. so do you want it to hold in step_001 for 30seconds no matter what.
2. or is step_001 the startup routine and you want it held for 30s after it has finished it's execution.
3. or You want it held after the start transistion for 30s before Step_001 executes.

for condition 1
from a quick glance the first rung is correct, the step_001.x bit will be true for the duration of step_001 being active, so as you as you transition into step_001 the timer will start, however if you process takes longer than 30s it will exit prematurely. rung 2 is no good because the 5000 series timer Presets are always in ms so it would only run for 30ms.

for condition 2 you would need
to change the XIC to look at step_001.DN bit which would trigger the timer to start when the step finished it's code execution. and time for 30s

For condition 3:
you would need to trigger the timer on the Start bit and have transition_000 be Timer_step_001.DN
 
Last edited:

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