TP Timer Pulse in PLC Programming: Definition and Usage

In PLC programming, a TP (Timer Pulse) is a timer instruction that generates a fixed-length pulse output when triggered. It produces a single ON pulse for a set time duration regardless of how long the input stays ON.

How It Works

Think of a TP timer like a camera flash. When you press the button (trigger), it flashes ON for a short, fixed time, then turns OFF automatically, no matter how long you hold the button. In PLCs, the TP timer starts timing as soon as its input condition becomes TRUE.

Once triggered, the TP timer output immediately turns ON and stays ON for the preset time. After this time passes, the output turns OFF even if the input remains TRUE. This behavior helps create precise, short pulses in automation processes.

Example

This example shows a TP timer that creates a 5-second pulse when a start button is pressed.

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START_BUTTON := TRUE;
TP_TIMER(IN := START_BUTTON, PT := T#5s, Q => OUTPUT_PULSE);

// When START_BUTTON goes TRUE, OUTPUT_PULSE turns ON for 5 seconds then OFF automatically.

Output

When START_BUTTON is TRUE, OUTPUT_PULSE = TRUE for 5 seconds, then OUTPUT_PULSE = FALSE.

When to Use

Use a TP timer when you need a precise, short pulse output triggered by an event. For example:

• Triggering a conveyor belt motor for a fixed time.
• Generating a timed signal to start another machine step.
• Creating a one-shot pulse to reset counters or alarms.

This timer is useful when the pulse length must be exact and independent of how long the input signal lasts.

Key Points

• TP timer outputs a fixed-length pulse on trigger.
• Output pulse duration is set by the timer preset.
• Pulse length is independent of input signal duration.
• Commonly used for one-shot signals in automation.

Key Takeaways

A TP timer creates a fixed-length pulse output when triggered.

The pulse duration is preset and does not depend on input length.

Use TP timers for precise one-shot signals in automation tasks.

TP timers help control devices needing exact timed pulses.