Timer On Delay (TON) instruction is a non-retentive timer that accumulates time when the instruction is enabled (rung-condition-in is true).

Lets see how it reacts before, during and after the timer has elapsed its preset value.

TON instruction is not energized yet as the “GRT” instruction is not true yet (24.863651<25). Note that the “EN” and “DN” are de-energized, and the “Accum” is zero.

The TON instruction is energized as the “GRT” is true. TON time elapsed is 18553 milliseconds. Note that “EN” is energized and “DN” is still de-energized.

TON instruction time elapsed is 43189 milliseconds. “EN” and “DN” state is still the same as before.

TON instruction has just reached preset value (of 60000), Both the “EN” and “DN” are energized. And we are using the “DN” bit to energize “UTL_TT25” coil.

When the TON is de-energized again, both the “EN” and “DN” are de-energized, and the “Accum” is zero again.

The acronym “EN” and “DN” stands for “Enable” and “Done” respectively.

Important: Be sure to scan the timer at least every 69 minutes while it runs. Otherwise, the ACC value won’t be correct.

Cheers!