RSLogix PLC Programming Timer instruction

• Goal: To learn how timers work

• Instructions:

  1. Go offline and enter the following ladder logic. The Timer function can be found by clicking on the “timer/counter” tab. You can return to the normal functions by clicking on the “user” tab.


  1. Run the ladder logic and observe how the switches change the operation of the timers. Try running the timer by switching the input on and off a few times while it is counting.

  2. After running the timer turn the PLC off and on, does the output stay on?

  3. Change the counter so that it takes 2 seconds to run by clicking on the “preset” on the timer and then entering “2”.

  4. Change the time base to 0.01: you will need to go offline and download the program again. How does this change the operation of the timer?

  5. Edit the ladder diagram to use a “TON” timer, as shown below. You will have to go offline to do this. SHORTCUT: Click on the “RTO” on the top of the timer, and then type in “TON” instead.


  1. Run the ladder logic. This time the input must stay on for a full 10 seconds before the output will turn on. How is this different from the “RTO”?

  2. Edit the ladder diagram so that it looks like the diagram below.


  1. Run the ladder logic. This timer uses the switch turning off to start counting. Try pushing the switch a few times quickly then slowly.