Lessons · Industrial control · hold-to-run, on purpose
Hold-to-run, on purpose
No branch means no hold: the output follows the button exactly and stops the moment it is released.
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
Half the time this is the bug and half the time it is the requirement, and telling them apart is the job.
How to think about it
Ask whether somebody should have to keep holding it. Setup moves, manual overrides and inching a jam clear are all deliberately hold-to-run. A conveyor is not.
Worked example
[Start] [/Stop] (Motor)Start pressed on scan 2 and released on scan 3. Motor: 0 1 0
Your turn
An operator says it only runs while they hold the button. What is missing?
the branch
Run a rung and watch the scan
The trap
Adding a seal to a control that was meant to be hold-to-run is a serious downgrade wearing the clothes of a bug fix.
Practise hold-to-run, on purpose on HoneA question on it now, a coding challenge where there is one, and it is remembered for review. Free, no email needed.