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Using Timers

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I have a question regarding timers and I seem to be finding conflicting information during my research.

If I am using an ON TIMER on a rung of my ladder logic to delay something from happening, does that timer pause the entire program execution, or does it just pause execution on that particular rung?  Will the other rungs continue to execute while this timer is waiting to expire?


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  • 3 weeks later...

ON TIMER is the simplest form of PLC timers. It has a coil and a contact.

When the coil is powered** the timer starts counting time. When coil loses power, it stops counting and resets elapsed time to zero. Contact closes when the coil is powered AND the elapsed time > preset time.

Timers do not halt program execution. The program just tests the status of coil, and updates the contact.

(** by "powered" I mean it has positive/true program logic on its input or left side. If this was a physical timer, then it would mean it has voltage on A1/A2 wire terminals.)

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