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On-delay timer relay
An on-delay timer postpones a specified output transition after its timing condition becomes active.
Schematic
IEC · KT
IEC timing-relay form: normally open delay on/off
Timing-relay form form: Normally Open Delay ON/OFF.
In plain English
What does IEC timing-relay form: normally open delay on/off mean?
A timing relay separates the initiating signal from the later change of an output contact. The contact state, delayed transition and reset condition are independent: a timer may have immediate contacts alongside delayed contacts under the same device tag. This entry identifies the normally open delay on/off form in the publisher's IEC-context family.
A simple example
A control sequence may start an auxiliary before enabling the main load, or keep a fan running after a stop request. Trace supply, trigger and output separately, then draw a timing chart that includes what happens when the trigger ends before a delay has elapsed. The normally-open designation starts with a non-conducting output or open contact in the documented reference condition; operation changes that state.
What the drawings help you do
The symbol does not supply the time setting, retriggering rule or power-loss behaviour. A three-terminal timing form also needs its actual manufacturer terminal mapping; the vendor name alone does not define a universal pinout.
This particular reference
Timing-relay form form: Normally Open Delay ON/OFF. This entry adds the normally open delay on/off detail to the broader timing-relay form family. The symbol does not supply the time setting, retriggering rule or power-loss behaviour. A three-terminal timing form also needs its actual manufacturer terminal mapping; the vendor name alone does not define a universal pinout.
- Normally open / normally closed
- The contact state in the normal condition defined for the drawing.
- Coil
- A wound conductor that can produce a magnetic field when energised.
- Terminal
- An identified point where a conductor connects.
Read the source: AutoCAD Electrical: Time-delay relays
IEC · Normally Open Delay ON/OFF
Autodesk IEC-60617 Symbol Preview: Time Delay Relays, HTD21DOO / VTD21DOO. This identifies the publisher's library context; exact IEC graphics and database identities are not asserted.
Shown as an independently authored educational illustration. Use the cited publication and drawing legend to verify the required drafting form.
Schematic · KT
What it represents
A timing relay separates the initiating signal from the later change of an output contact. The contact state, delayed transition and reset condition are independent: a timer may have immediate contacts alongside delayed contacts under the same device tag. This entry identifies the normally open delay on/off form in the publisher's IEC-context family.
A control sequence may start an auxiliary before enabling the main load, or keep a fan running after a stop request. Trace supply, trigger and output separately, then draw a timing chart that includes what happens when the trigger ends before a delay has elapsed. The normally-open designation starts with a non-conducting output or open contact in the documented reference condition; operation changes that state.
The symbol does not supply the time setting, retriggering rule or power-loss behaviour. A three-terminal timing form also needs its actual manufacturer terminal mapping; the vendor name alone does not define a universal pinout.
How to read it
- The normally-open designation starts with a non-conducting output or open contact in the documented reference condition; operation changes that state.
- The symbol does not supply the time setting, retriggering rule or power-loss behaviour. A three-terminal timing form also needs its actual manufacturer terminal mapping; the vendor name alone does not define a universal pinout.
Information to show or reference
- Identify the initiating supply or control signal.
- Label delayed and immediate output transitions separately.
- Reference timing settings, reset conditions and the device timing chart.
A distinction that matters
This entry adds the normally open delay on/off detail to the broader timing-relay form family. The symbol does not supply the time setting, retriggering rule or power-loss behaviour. A three-terminal timing form also needs its actual manufacturer terminal mapping; the vendor name alone does not define a universal pinout.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
AutoCAD Electrical: Time-delay relays
Public Time Delay Relays table explicitly lists HTD21DOO / VTD21DOO with this operating or connection form. Vendor graphics are linked, not copied.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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