TON Timer On Delay in PLC Programming Explained

A TON timer on delay in PLC programming is a timer that starts counting when its input turns ON and only activates its output after the preset time elapses. It delays the output signal by a set time, useful for controlling processes that need a wait before action.

How It Works

Think of a TON timer on delay like a kitchen timer you start when you put food in the oven. When you press start (input ON), the timer begins counting. Only after the set time finishes does the timer 'ring' (output ON).

In PLCs, when the input to the TON timer turns ON, the timer counts up from zero. If the input stays ON continuously for the preset time, the timer's output becomes true. If the input turns OFF before the time ends, the timer resets and the output stays OFF.

This delay helps machines wait before starting the next step, avoiding sudden or premature actions.

Example

This example shows a TON timer that waits 5 seconds after a start button is pressed before turning on a motor.

structured_text

TON_Timer:
  IN := StartButton;
  PT := T#5s;
  Q => MotorOn;
  ET => ElapsedTime;

// Logic:
// When StartButton is TRUE, timer counts 5 seconds.
// After 5 seconds, MotorOn becomes TRUE.

Output

If StartButton = TRUE for 5 seconds, then MotorOn = TRUE; else MotorOn = FALSE.

When to Use

Use a TON timer on delay when you need to delay an action after a condition starts. For example:

• Waiting for a machine to warm up before starting a conveyor belt.
• Delaying a pump start to avoid pressure surges.
• Ensuring safety checks complete before activating equipment.

This timer helps prevent sudden starts and allows processes to stabilize.

Key Points

• Input ON starts timer counting.
• Output turns ON only after preset time elapses.
• Input OFF before time resets timer and output.
• Common in automation to delay actions safely.

Key Takeaways

A TON timer delays output activation until input stays ON for a set time.

If input turns OFF early, the timer resets and output stays OFF.

Use TON timers to safely delay machine actions and avoid sudden starts.

They are essential for controlling timed sequences in automation.

The timer output only activates after the full delay period completes.