# What is On-Delay and Off Delay timer

**URL:** <https://forumautomation.com/t/what-is-on-delay-and-off-delay-timer/1750>\
**Category:** Industrial Automation\
**Created:** [February 12, 2017, 4:52pm UTC](https://forumautomation.com/t/what-is-on-delay-and-off-delay-timer/1750 "2017-02-12T16:52:37Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![denizen](https://forumautomation.com/letter_avatar_proxy/v4/letter/d/848f3c/32.png) [@denizen](https://forumautomation.com/u/denizen)\
**Post date:** [February 12, 2017, 4:52pm UTC](https://forumautomation.com/t/what-is-on-delay-and-off-delay-timer/1750/1 "2017-02-12T16:52:38Z")

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Timer are used in PLC program to introduce some delays in a logic transition.

**On-Delay Timer**

For an On-delay timer two different types of contact.

**NOTC - Normally opened,timed -closed.**

This timer is normally open and that is going to take some time to close.

 ![](https://cdn.forumautomation.com/original/1X/081a896b757d25b5c5d972e5039c5f5363156bb5.jpg)

Contact is open when the relay coil (Timer Input for PLC programming) is de-energized.

When the relay is energized there is a time delay in closing.

 ![](https://cdn.forumautomation.com/original/1X/0a2699d172b95248c314f3adee9f4c33df7dde34.jpg)

**NCTO - Normally-Closed,Timed -Open**

This timer is normally closed and that’s going some time to open.

 ![](https://cdn.forumautomation.com/original/1X/f3cbd05e50caa7bd4c9d4db6cd7c4294500ddddd.jpg)

Contact is closed when the relay coil is de-energized

When the relay is energized,there is a time delay in opening.

 ![](https://cdn.forumautomation.com/original/1X/41728064fd236c456e41a15d01e4bb0fbe3c3f67.jpg) **Off delay Timer**

**NOTO (Normally Open,Timed Open)** -

Contact is normally open when the relay coil is de-energized.

When the relay coil is energized,the contact closes instantly.

When the relay coil is de-energized,there is a time delay before the contact open.

 ![](https://cdn.forumautomation.com/original/1X/313f8571df431b6a89073567a120936ae4da0b44.jpg)

**NCTC - Normally Closed,Timed Closed Contacts**

Contact is normally closed when the relay coil is de-energized.

When the relay coil is energized,contacts opens instantly.

When the relay coil is de-energized,there is a time delay before the contact open.

 ![](https://cdn.forumautomation.com/original/1X/37da1b6fe8324a037958f03a006ac9ffc9791592.jpg)