[LOGIC GATES] Constructing Ladders.

Discussion in 'Homework Help' started by darkmasta, Feb 14, 2010.

  1. darkmasta

    Thread Starter New Member

    Oct 25, 2009
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    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 --[/]--

    [​IMG]
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    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.
     
  3. bertus

    Administrator

    Apr 5, 2008
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  4. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    Look at this ladder diagram
    [​IMG]

    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 ?
     
  5. darkmasta

    Thread Starter New Member

    Oct 25, 2009
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    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 ?
     
  6. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    I think it will be something like this
     
  7. darkmasta

    Thread Starter New Member

    Oct 25, 2009
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    Thank you for replying !

    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: Feb 14, 2010
  8. Jony130

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    Feb 17, 2009
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  9. darkmasta

    Thread Starter New Member

    Oct 25, 2009
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    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 :)
     
  10. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    You put Son is series with Soff.
    So to light Lon the Son and Soff must be ON (1).
     
  11. mik3

    Senior Member

    Feb 4, 2008
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    He said there is a mistake in the diagram and that Soff is N.C.
     
  12. darkmasta

    Thread Starter New Member

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

    [​IMG]

    [​IMG]

    The start and stop are in series there :S
     
  13. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    Using your first link ....

    Rung 1 - Depressing the start button, and it is a momentary contact button, relay SI will energize IF the lube oil switch is energized, any of the three valves are closed, there are no alarms, and the motor overloads are not energized. The SI contacts in the Seal-in function forms a latch keeping the relay SI energized. When SI is energized, the Red lamp is energized and the green lamp is de-energized.

    SI relay de-energizes when the momentary push button labeled stop is depressed, or the lube oil switch opens, or the alarm switch opens, or any motor overload switch opens, or all three valve switches open. The Red lamp will de-energize and the Green Lamp will energize.

    My read is the relay contacts are drawn in the relay de-energized state. Of course I've seen diagrams where contacts were depicted in both states, thus making the diagram a little harder to read.
     
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