What is the main difference between TON (On Delay) and TOF (Off Delay) timers?

What is the main difference between TON (On Delay) and TOF (Off Delay) timers?

• A. TON energizes the output after the input has been energized for the preset time; TOF de-energizes the output after the input has been de-energized for the preset time
• B. TON resets automatically after the preset time, TOF increments its timer when energized
• C. TON and TOF are the same
• D. TON acts as a counter, TOF acts as a timer

Answer: (A)

The main idea here is how these timers control when the output changes in response to the input. A delay-on timer waits for the input to stay on for the preset time before energizing the output. If the input goes off before that time is up, the timer resets and the output never turns on. A delay-off timer does the opposite: when the input goes off, it starts counting, and the output remains energized for the preset time after the input has turned off; only after that delay does the output turn off. So, a delay-on timer makes the output switch on after the input has been on long enough; a delay-off timer keeps the output on for a set time after the input has been released. For example, use a delay-on timer if you want a motor to start only after a button has been held for a couple of seconds; use a delay-off timer if you want the motor to keep running for a short while after you release the control. The other statements don’t fit because a delay-on timer does not reset automatically after the preset time—the reset behavior depends on the input staying on; a delay-off timer does not increment its timer while the input is energized, it starts counting when the input goes off; and TON and TOF are different types of timers, not counters.

The main idea here is how these timers control when the output changes in response to the input. A delay-on timer waits for the input to stay on for the preset time before energizing the output. If the input goes off before that time is up, the timer resets and the output never turns on. A delay-off timer does the opposite: when the input goes off, it starts counting, and the output remains energized for the preset time after the input has turned off; only after that delay does the output turn off.

So, a delay-on timer makes the output switch on after the input has been on long enough; a delay-off timer keeps the output on for a set time after the input has been released. For example, use a delay-on timer if you want a motor to start only after a button has been held for a couple of seconds; use a delay-off timer if you want the motor to keep running for a short while after you release the control.

The other statements don’t fit because a delay-on timer does not reset automatically after the preset time—the reset behavior depends on the input staying on; a delay-off timer does not increment its timer while the input is energized, it starts counting when the input goes off; and TON and TOF are different types of timers, not counters.