A Timer operand allows you to count time according to certain logic conditions.
A Timer has
Preset value
Current value
Start and Run condition
Bit Value
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.
Either the current or elapsed timer value may be shown on the HMI display screen.
According to the above example:
When MB 1 goes to logic 1 (ON), T 20 will begin to count down.
When T 20 finished counting and goes to logic 1 (ON), MB 7 will go to logic 1 (ON) and the motor will start.
To place a Timer in your program, place a direct coil in a net, and select T.
Timer resolutions |
10mS (0.01S)(from 00:00:00.01 to 00:02:43.83 ) |
100mS (0.1S)(from 00:00:00.10 to 00:27:18.30) |
1000mS (1.0S)(from 00:00:01.00 to 04:33:03.00 ) |
10000mS (10.0S)(from 00:00:10.00 to 45:30:30.00) |
Note that:
A Timer value can be displayed in a Display as a current or elapsed value/
The Resolution field is Read-only. The resolution is a function of the Timer Preset Value.
You cannot change the resolution of a timer when the application is running.
A timer's current value can be changed at any time , including when the timer is active. The new value can be either greater or smaller than the previous value; storing 0 into a timer's current value stops it immediately.
A change of Timer Preset value without changing the resolution will take effect when the timer restarts.
Changing the resolution of the timer's preset value does not affect the current resolution; it is therefore recommended that the resolution not be changed while the timer is active.
During Stop mode, timers continue to run.