This document discusses different types of timers used in PLC ladder logic programming. It describes on delay timers (TON), off delay timers (TOFF), and retentive timers (RTO). On delay timers activate their output after a preset time when their input is activated. Off delay timers keep their output energized for a preset time after their input turns off. Retentive timers maintain their accumulated time value even during power loss. The document provides timing diagrams and examples of how to program timers in an Omron PLC.

1. UCJ PLC TIMER
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PLC TIMER
 PLC timer is an element in ladder logic programming taken from
electrical systems. Timers are devices that count time increments.
 When the input is activated the timer starts its operation keeping
track of the time. When this time exceeds the programmed time
then the timer activates its output.
TYPES OF PLC TIMERS:
1. ON delay timer (TON)
2. OFF delay timer (TOFF)
3. Retentive Timer (RTO)
ON DELAY TIMER (TON)
 On delay means that once a timer has received a power on signal,
its output will change state after a predetermined delay.
 The timer will be ON when a start input signal is received, and
when a preset timing is reached, the signal state of the output
changes from 0 to 1.
o ON DELAY TIMING DIAGRAM

2. UCJ PLC TIMER
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 The timer starts operating when the rung condition becomes true.
The timer delay starts counting when the rung condition starts to
accumulate.
 The length of the delay can be adjusted by setting the preset value.
 Timer number: The timer file name
 Preset value which means the delay period of the timer,
 Preset value: Numeric valve set as the delay required to the timer.
 Accumulated value which is the current delay of the timer.
 Accumulated value: The values are counting is displayed from
zero. Value becomes zero whenever the timer is reset
OFF DELAY TIMER (TOFF)
 A TOFF timer will keep the output energized for a preset time
after the rung signal has gone false.
 OFF DELAY TIMER TIMING DIAGRAM

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 When the rung timer is true, the output will be true without
any delay. When the rung signal becomes false the timer
starts operating.
 The timer starts accumulating times when the rung
condition becomes true, until the accumulated value
becomes equal to the Preset value.
 The output turns off when the output will turn false when
the accumulated value equals the preset value.
RETENTIVE TIMER (RTO)
 A retentive timer is used when we want to keep accumulated time
value During the power loss/cut.

4. UCJ PLC TIMER
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 A retentive timer accumulates time whenever the device receives
power, and it maintains the current time should power be removed
from the device
 Application of retentive timer: Washing machine, Microwave
Oven and etc.
HOW TO PROGRAMMING TIMER IN OMRON PLC.
 Input TIM<space>000<space>#100 and then press
OK button
TIM = Timer Delay ON / PLC Timer ON Delay
Function
TIM000 = Timer Contact Number
#100 = Setting Value 10 sec (Time of ON
delay)