Timers (T)

When the timer's Start & Run Condition is OFF, the timer's Bit Value is also OFF.

When the timer's Start & Run Condition rises, the timer's Preset Value is loaded into the timer's Current Value. The timer begins to run. Note that the timer's Bit Value is OFF.

If the timer's Start & Run Condition remains ON during subsequent PLC cycles, the Current Value of the timer continues to decrement.

When the timer has decremented to 0, and the timer's Start & Run Condition is still ON, the timer's Bit Value turns ON. Note that when the timer has finished running, its Current Value is 0.

If the timer's Start & Run Condition falls while the timer is decrementing, the timer stops running. The current value of the timer remains.

Timer Reset takes precedence over the timer's Start & Run Condition. When the timer' Reset Condition rises, the timer's Bit Value turns OFF. The timer's Preset Value is loaded into the Current Value, and the timer's Start & Run Condition cannot activate the timer as long as Reset is ON..

When the timer's Reset Condition falls while the timer's Start & Run Condition is ON, the timer begins to run, exactly the same as when the timer's Start & Run Condition rises.

Below, pressing Key #1 on the Vision keypad activates TD1, which is preset to 5 seconds. If Key #1 is held down for 5 seconds, TD1 decrements to zero. O1 switches on.

If, however, Key #1 is released before TD1 has finished, the timer stops. When Key #1 is pressed again, TD1 again begins to decrement from 5 seconds.

   

When the timer's Run Enable Condition rises, the timer's Preset Value is loaded into the timer's Current Value. The timer begins to run. Note that the timer's Bit Value is OFF. When the timer's Run Enable Condition remains ON during subsequent PLC cycles, the Current Value of the timer continues to decrement.

When the timer has decremented to 0, and the timer's Start & Run Condition is still ON, the timer's Bit Value turns ON. Note that when the timer has finished running, its Current Value is 0.

If the timer's Run Enable Condition falls while the timer is running, the timer stops running, but the current value of the timer is retained.  When the timer is reactivated, it begins decrementing from the retained value.

Timer Reset takes precedence over the timer's Run Enable Condition. When the timer' Reset Condition rises, the timer's Bit Value turns OFF. The timer's Preset Value is loaded into the Current Value, and the timer's Run Enable Condition cannot activate the timer as long as Reset is ON.

When the timer's Reset Condition falls while the timer's Start & Run Condition is ON, the timer begins to run, exactly the same as when the timer's Run Enable Condition rises.

Note  ♦

Once a TA Timer has reached its preset value, its Bit Value remains ON until the timer is reset in the program.  The timer cannot be activated by Run Enable until it has been reset.

 

In the net below, pressing Key #2 on the Vision keypad activates TA2, which is preset to 5 seconds. If Key #2 is held down for 5 seconds, TA2 decrements to zero. O2 switches on.

If, however, Key #2 is released after 2.53 seconds--before TA2 has reached the preset value--the timer stops and its current value is retained . When Key #2 is pressed again, TA2 begins to decrement from 2.53 seconds.  When TA2 decrements to 0, O2 turns ON.

When the timer's Start Condition rises, and the Bit Value is OFF, the timer's Preset Value is loaded into the timer's Current Value. The timer begins to run and the Bit Value turns ON.

If the timer's Start Condition remains ON during subsequent PLC cycles, the Current Value of the timer continues to decrement. However, if the timer's Start Condition rises before the timer has decremented to its Preset Value, the timer reloads the Preset Value into the Current Value, and again begins to decrement. Note that a falling Start condition does not affect the timer.

When the timer has decremented to 0 the timer's Bit Value turns OFF. Note that when the timer has finished running, its Current Value is 0.

Timer Reset takes precedence over the timer's Start Condition. When the timer' Reset Condition rises, the timer's Bit Value turns OFF. The timer's Preset Value is loaded into the Current Value, and the timer's Start Condition cannot activate the timer as long as Reset is ON..

When the timer's Reset Condition falls while the timer's Start Condition is ON, the timer stops. When the Start condition rises, the timer begins to run, counting down from the Preset Value, exactly the same as when the timer's Start Condition rises.

Note  ♦

Once a TE Timer has reached its preset value, its Bit Value remains OFF until the timer is reset in the program.

In the nets below, pressing Key #3 on the Vision keypad activates TE3, which is preset to 5 seconds. Once Key #3 is pressed, TE3 decrements to zero. O3 switches on.

    

To display a list of Timers, click on the Operand tab in the Output Window at bottom of the screen, then select Timers.  Scroll down to view the list.

Timers can also be preset and edited in the Select Operand and Address dialog box when you insert a timer into your program.

You can also use Information Mode to edit or enter a timer value via the controller keyboard while the controller is running its control program.