PLC TIMER AND COUNTER
PLC TIMER
WHY TIMERS ARE USED IN PLC?
2. Keep an output on for a specified after an input turns off
3. Keep n output off for a specified time before it turns on
TYPES OF TIMER
1. Timer ON2. Timer OFF
3. RTO Retentive timer
PLC TIMER DEFINITION
Base time:
The duration of the time interval that time is an increment in 1 second, 0.1 seconds, 0.01 second, 0.001 second
Timers are typically programmed with several different time bases
If base time is set to 0.1 and delay increment is 5 second
Time delay ( 0.1 × 50)
The duration of the time interval that time is an increment in 1 second, 0.1 seconds, 0.01 second, 0.001 second
Timers are typically programmed with several different time bases
If base time is set to 0.1 and delay increment is 5 second
Time delay ( 0.1 × 50)
Preset:
Determine the amount of the time that must pass to active done bits (DN)
The preset value is the number of time increments time must count before changing the state of the output.
Time delay = preset value × timebase Preset can be constant or variable
Accumulator:
When the timer is in active mode the accumulator increments in the units of the time base
Timers have one input. When the input transits from low to high, the timer will begin timing.
Timers that do not lose their accumulated time when the enable input line
Transitions to low again are known as Retentive Timers
Retentive Timers continue to maintain accumulated time and increment the time when the input line goes too high again
Non-retentive Timers lose the accumulated time whenever the enable input transitions to low.
Enable bit (EN):
Enable bit is active when the timer input is True
Done bit (DN):
The done bit is true when the accumulator value is equal to the preset time.
Timer timing bit (TT):
The timer timing bit is active when the accumulator is incrementing.
Determine the amount of the time that must pass to active done bits (DN)
The preset value is the number of time increments time must count before changing the state of the output.
Time delay = preset value × timebase Preset can be constant or variable
Accumulator:
When the timer is in active mode the accumulator increments in the units of the time base
Timers have one input. When the input transits from low to high, the timer will begin timing.
Timers that do not lose their accumulated time when the enable input line
Transitions to low again are known as Retentive Timers
Retentive Timers continue to maintain accumulated time and increment the time when the input line goes too high again
Non-retentive Timers lose the accumulated time whenever the enable input transitions to low.
Enable bit (EN):
Enable bit is active when the timer input is True
Done bit (DN):
The done bit is true when the accumulator value is equal to the preset time.
Timer timing bit (TT):
The timer timing bit is active when the accumulator is incrementing.
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