Lessons · Industrial control · finding the rung that stopped
Finding the rung that stopped
Start at the thing that is not happening, find its coil, and look for the contact that is not made.
Hone is a place to practise programming. This is one of its lessons, written out in full and free to read without an account.
What it is for
Three steps instead of three hundred rungs. It is the difference between a ten-minute fix and an afternoon.
How to think about it
The output names the rung. The rung names a handful of conditions. Online, the made ones are lit and the gap is visible without reading anything. Then repeat on whatever owns that gap.
Worked example
[Guard] [PartPresent] [/Jam] (Motor)Guard closed, no part present, no jam. Motor: 0 -- and it is PartPresent that is false, which is a sensor to go and look at, not a rung to rewrite.
Your turn
In a series rung, how many contacts have to be made?
of them
Run a rung and watch the scan
The trap
If every contact is made and the coil is still off, stop looking at this rung. Something lower down is writing the same coil, which is the next stage.