 Hello everyone, welcome to this session on timers part 2. So, at the end of the session, you will be able to examine symbol and basic usage of on delay timers which are available in the PLC programming standard. You will be also able to write ladder run diagrams with on delay timers for basic operations. So, let us learn more about the on delay timers. On delay timers waits for a preset time that is defined by PT value after an input in a ladder logic becomes true before turning on the output queue. Then queue gets false and ET resets immediately when input becomes false. Let us learn about the on delay timer inputs. Input when changes timer starts, the data type associated with this input is Boolean means you are expecting either 0 or 1, PT that is preset time. This value indicates the desired delay which you want in your operation. And the data type associated with this PT value is time means you have to mention the delay in terms of seconds. Outputs queue shows whether the time has elapsed or not. ET stands for elapsed time. It shows the time still remaining that is the time that has elapsed since the timer was activated. The data type associated with ET is time, so you will get the current value of the timer in seconds at ET whereas the data type associated with queue is Boolean means you are expecting either 0 or 1 at queue. Let us learn about the on delay timer with the help of the waveform. The main function of on delay timer also known as T on timer is to delay the rising age of queue by the predefined preset time. So here you will see at T0 when input changes from 0 to 1 timer starts immediately ET value increments toward PT when ET equals to PT your queue changes its state from 0 to 1. So the rising age of input and the rising age of queue you will see the difference is PT duration. When the condition at the input is satisfied that is it becomes true timer starts and queue gets true after the preset time PT. So here the arrow shows the transition for the output state to change from false to true the input must be true for at least as long as preset time PT. So here you will see that at T2 input changed from 0 to 1 but at T3 it again changes from 1 to 0 and the width of this particular pulse is very short it is less than the PT duration. So here you will see that at T3 when input becomes false the ET value resets to 0 and because of this this particular change in the input is not reflected on the output waveform means it is missed on the output waveform. So because of this your width of the input pulse should be greater than or equal to PT value. So here you will see that at T4 input changes from 0 to 1 and input remained true for more than PT value and because of that you will see that the output changes when ET becomes PT at T4 plus PT value. So at T4 plus PT value you will see that queue changes from 0 to 1. At T5 when the input changes from 1 to 0 ET as well as your queue resets to 0. So here at instant T1 and T5 you will see that when input changes from 1 to 0 ET as well as your output queue resets to 0. This is the typical symbol available in this on PLC editor for a TON that is on-delay timer under standard function block. Let us understand some examples based on on-delay timer. Let us understand this particular example which is used to generate longer delays by cascading multiple on-delay timers. So here you will see three run ladder diagram. In the first run we have one switch one coil. So this coil represents timer one. In second run we have timer one switch which is dependent on timer one coil. Again we have timer two coil in the second run. In the third run we have timer two dependent switch and output one coil. Let us understand the working of this particular ladder diagram with the help of this waveform on the right hand side. So at T0 instant you will see that input changes from 0 to 1 which turns on this timer. So timer starts with PT equal to 999 seconds. After 999 seconds timer one contact closes at T1 and timer two starts with PT equal to 100 seconds. At T2 after 100 seconds timer two contact closes and output one energizes. So if you calculate the total delay inserted is 1099 seconds. So here with the help of two timers you have achieved to get larger delay by cascading two on-delay timers. At T3 when the input one opens output one and all the ETs resets to 0. Let us solve one more problem. Let us develop a ladder diagram for a system that will run a motor after a predefined time when input switch is activated and the time here given is 5.5 seconds. So when input switch is activated after 5.5 seconds motor should start. When the switch is deactivated motor should stop immediately. So let us develop a run ladder diagram for this particular problem. So here is the solution for this example two. We have two runs in the first run we have one switch and one output coil in the second run we have one switch one coil and timer inserted between them. So at T0 when input one contact closes means when input changes from 0 to 1 output also changes from 0 to 1 output 1. So when output one changes from 0 to 1 timer starts with preset value equal to 5.5 seconds. So at T1 that is after 5.5 seconds output two energizes. So here you will see that a 5.5 seconds delay is inserted between input change and the output change. So your motor here will start after 5.5 seconds delay when the input changes. At T2 when the input contact opens that is when the input changes from 1 to 0 output one output two deenergizes and ET value resets to 0. So this is how you can actually use on delay timers for controlling different operations with reference to time. Let us see how to use on delay timer with a simulation example. So this is a PLC FIDL online platform where you will see that ladder diagram is drawn with two switches one on delay timer and one motor. So on the left hand side you will see the controls and the settings related to the timer. So let us set this preset PT value to 10 and let us turn the status of switch A. Let us see what happens. So here you will see that this accumulator which is showing the lapse time is incrementing. So when it reaches 10 the motor coil is activated energized. When I change the status of switch A again the motor coil deenergizes immediately. So this is the online FIDL platform which you can use for simulating simple PLC logics. These are the references which you can refer for further reading. Thank you.