#### darkmasta

Joined Oct 25, 2009
8
Hey guys I have a question that is confusing me.

It is mentioned that the N.C -[/]- (normally closed) contact is similar to a Logical invertor (NOT).

How is a --|NOT|-- similar to a --[/]-- contact ?

Can someone please explain this with diagrams ?

Thank you very much !!

I am asking this because I want to know if this model is correct :

Son = On Switch
Soff= Off Switch
Lon = ON light
Loff= OFF light
M= Motor

The on switch should turn on the Motor and ON light. The off button should turn off the Motor and ON light, AND turn on the OFF light.
I have a mistake in the picture, the Soff should be N.C --[/]--

#### mik3

Joined Feb 4, 2008
4,846
A normally closed contact is a contact which conducts all the time. It stops condcuting when it is energized. It is the opposite of a normally open contact which conducts only when it is energized.

#### Jony130

Joined Feb 17, 2009
4,925

We have on input switch S1 and two output lights.
When S1 is ON [1] then L1 [1] is ON ans L2 OFF [0]
And when S1 is OFF [0] then L2 is ON [1] and L1 is OFF [0].

And in your diagram you have two switch or only one switch?
And two lights ?

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#### darkmasta

Joined Oct 25, 2009
8
Thank you all for replying. Mik3, yes I know that already, thanks for replying. Bertus I did check that page before posting this topic, thank you anyway .

Jony130 , thank you for explaining that
Yes I have two switches and two lights :

Son = On Switch
Soff= Off Switch
Lon = ON light
Loff= OFF light
M= Motor

Is my ladder diagram correct ? or is it wrong ?

#### Jony130

Joined Feb 17, 2009
4,925
I think it will be something like this

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#### darkmasta

Joined Oct 25, 2009
8
I think it will be something like this

Can you please explain the sketch ? does that mean there are more than 2 buttons ? there is an Son and Soff in the first rung, and the same in the second rung !

And does that mean my ladder model is incorrect ?

Thank you very much.

Last edited:

#### Jony130

Joined Feb 17, 2009
4,925

#### darkmasta

Joined Oct 25, 2009
8
Thank you very much, really helpful

So your model is correct, right ? So I can assume mine is wrong. Can you tell me where is the mistake in my model ?
Thanks

#### Jony130

Joined Feb 17, 2009
4,925
Can you tell me where is the mistake in my model ?
Thanks
You put Son is series with Soff.
So to light Lon the Son and Soff must be ON (1).

#### mik3

Joined Feb 4, 2008
4,846
You put Son is series with Soff.
So to light Lon the Son and Soff must be ON (1).
He said there is a mistake in the diagram and that Soff is N.C.

#### darkmasta

Joined Oct 25, 2009
8
Oh, but i was following those models :

The start and stop are in series there :S

#### JoeJester

Joined Apr 26, 2005
4,074