PLC I/O
PLC input / output
A controller interface point connecting field signals to an identified module channel.
Schematic
Symbols · SEQ
Power-rail sequencer
In plain English
What does Power-rail sequencer mean?
A power sequencer controls the order in which selected supply rails are enabled or disabled.
A simple example
A controller board can bring its supplies up in the order required by its devices.
What the drawings help you do
Show each rail-enable output and any feedback used to decide the next step. An ordered command is different from proof that a supply reached its intended condition. The drawing should therefore distinguish the requested sequence, actual rail voltages and the status inputs used by the controller.
- Rail
- A named supply connection or voltage domain.
- Sequence
- The defined order and conditions of the controlled actions.
Before using this reference
- Identify each controlled rail and enable output.
- Show feedback used to advance or stop the sequence.
- Reference startup, shutdown and fault sequencing.
Does enabling rail two prove rail one is ready?
Only if the selected sequence actually checks the required condition. A timed command alone and a feedback-qualified sequence provide different information, so show the implemented control method.
Read the source: Power supply sequencing
Schematic · SEQ
A distinction that matters
An ordered enable signal does not itself prove that a rail reached its intended voltage.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Power supply sequencing
Power supply sequencing: public technical context for the named function. Product and compliance details remain with the publisher.
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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EN
Power-rail enable interface
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