TON - On Delay Timer

Introduction

The TON on delay timer function block turns an output on after a delay.

Syntax

The TON Function Block has this syntax:

TON(
        IN:=Expression,
        PT:=Expression,
        Q=>Variable-Reference,
        ET=>Variable-Reference );

Note: All parameters are optional.

Parameters

Parameter	Type	Direction	Description
IN	BOOL	Input	A rising edge starts the timer.
PT	TIME	Input	The duration of timer.
Q	BOOL	Output	Set to true after delay PT.
ET	TIME	Output	The elapsed time of the timer.

Remarks

The TON Function Block uses this logic:

If the input IN is FALSE:
- Output Q will be FALSE.
- Output ET will be T#0s.
If the input IN changes to TRUE, output ET increases until it reaches input PT.
When the the output ET equals input PT, output Q is set to TRUE.

These timing diagrams show the relationship of the TON Function Block inputs and outputs:

     Example 1        Example 2
       +--------+       +-+
  IN   |        |       | |
     --+        +---  --+ +---

            +---+
  Q         |   |
     -------+   +---  --------

            +---+
           /    |
          /     |
  ET     /      |         +
        /       |        /|
     --+        +---  --+ +---

Notes:

Example 1 shows input IN equal to TRUE for a time period longer than PT.
Example 2 shows input IN equal to TRUE for a time period shorter than PT.

Standards Compliance

IEC 61131-3 Second Edition: Table 37.2.

IEC 61131-3 Third Edition: Table 46.2a.

Further Information

TOF Function Block

To learn about a function block that turns an output off after a delay.

Standard Function Blocks

To learn about other standard function blocks.

Elementary Data Types

To learn about the different types supported by Fernhill SCADA.

Common Elements

To learn about other IEC 61131-3 Common Elements.

Glossary

For the meaning of terms used in Fernhill SCADA.