When does the Timer On Delay instruction energize its DN bit?

The Timer On Delay instruction energizes its Done (DN) bit after the accumulated value reaches and equals the preset value. This functionality is fundamental in controlling the timing operations within a programmable logic controller (PLC) system.

In practice, the Timer On Delay operates by counting for a set duration defined by the preset value. When the timer is first activated, it begins accumulating time. Once the accumulated time matches the preset duration, the DN bit is energized, indicating that the timer cycle is complete, and thus triggering any subsequent actions defined in the program that rely on this completion signal.

Understanding this function is crucial for ensuring that the timing sequences in automation processes occur accurately and predictably, allowing for more reliable control in industrial applications.