Normally Open, normally closed

[bernardgreen]

What I mean is , if there is one drawing provided whether in a manual, affixed on the back of a panel door or whatever, it will always without exception show the circuit un-energised.

There are exceptions. Circuit diagrams of a small automatic telephone exchange where some relays are continuously energised show the contacts in the energised state. A symbol indicating normally operated is placed by the contacts and coil of each of these relays.

The relays are alarm relays with a open when de-energised contact completing a loop to the parent exchange to indicate no fault.

 

[Porque223]

If a contactor states its "normally closed" or "normally open", does this mean without power applied to it?

Yes. How it is in the packet when bought.

Yes, otherwise it would have to foresee what position the armature would customarily be in.

Here's one: an amplifier output terminal is labelled 'output' and a speaker input terminal is labelled 'input'. What should the connecting wire be labelled?

 

[RF Lighting]

"Interconnect"

 

[mattylad]

I have often found diagrams showing relays in either state, sometimes they do not even say what state they are in and the reader has to either guess or assume it is de energised.

When drawing a fire alarm or P.A circuit I would always indicate the state that the relay is in, because often it would have to be displayed in the energised state.
That was a company specific thing, a great many companies do things differently - including the symbol that they use.

There are several standards and many different interpretations of how the relay symbol should be drawn which confuses things even more.

These days I see so many different companies using different symbols from ANSI to IEC to ISO, BS etc (or whatever the standards are.)

The symbol using a white (clear) and black (filled) pin is a good way of doing it although I had never realised that this was how it was actually meant to be.
I shall have to try and remember that.

 

[Porque223]

There is also Make before Break and its inverse.

But they mean exactly what they say, with no ambiguity or scope for confusion, don't they?

Kind Regards, John

Can you think of other connections between the OP's Q and this answer besides the more generic "Contact Configurations"?

 

[JohnW2]

There is also Make before Break and its inverse.

But they mean exactly what they say, with no ambiguity or scope for confusion, don't they?

Can you think of other connections between the OP's Q and this answer besides the more generic "Contact Configurations"?

No, I can't . However, my comment was not an answer to the OP's question (which was done and dusted in the first three responses of the thread) but, rather, a response to what you had just written (as above) - and I could ask you exactly the same about that (i.e. "Can you think of other connections between the OP's Q and this answer besides the more generic "Contact Configurations"?"). On-line discussions evolve!

Kind Regards, John

 

[Porque223]

On-line discussions evolve!

Kind Regards, John

Hopefully they eventually converge.
I look for the moral of the story, the forest after seeing the trees.

 

[JohnW2]

On-line discussions evolve! John

Hopefully they eventually converge.

I think that they more often diverge! As I wrote earlier, except when the matter is particularly complex, an OP's questions are usually answered satisfactorily within the first few responses, certainly usually within the 'first page' of responses. When discussions go on a lot longer than that, it's usually because they have gone off on 'tangents' onto issue which may, or may not, be of interest to some forum members.

Given that no-one is forced to participate, I suppsoe one has to assume that those who chose to become involved in such 'tangential' discussions must have some interest in so doing!

Kind Regards, John

 

[scousespark]

yup it is a relay with its N/O contact -closed, but in it's normal standby operating "state"

We all know the facts, but I'm with Bernard on this one - I've often seen considerable confusion about the meaning of 'normal' in relation to relay and switch contacts, and similarly with semiconductor gates.

When annotating diagrams involving relays or gates in order to aid understanding of function, I try as hard as I can to avoid using the word 'normal', instead using words like 'usual', energised/unenergised resting/alarm etc. ... and that's not only for others ('the uninitiated'). Even my own mind can get totally tied in knots when looking at one of my own diagrams when there are lots of relay contacts whith are 'normally' (usually) closed, or gates which 'normally' (usually) have a 'high' input or output.

Kind Regards, John

I would say the purpose of the diagram would deternmine the need for annotation. If the circuit is to be maintained by electricians and the diagram shows the normal (un-energised) state any annotation is superfluous and could be confusing.

 

[JohnW2]

I would say the purpose of the diagram would deternmine the need for annotation. If the circuit is to be maintained by electricians and the diagram shows the normal (un-energised) state any annotation is superfluous and could be confusing.

I suppose it's a personal thing. Speaking personally, if I'm faced with a diagram showing dozens of relays, all shown (as usual) symbolically in their unenergised states, I'm likely to be grateful for some functional annotation. Similarly with dozens, or hundreds, of semiconductor gates, functional annotation is again welcome (at least to me!). The way I see it, in the absence of such annotation, everyone who looks at the diagram has to re-invent the same wheel for themselves, which hardly seems 'efficient'. However, as I said, I suppose it's a matter of personal choice.

Kind Regards, John