Question

Discussion in 'General Electronics Chat' started by RG23, Feb 29, 2012.

  1. RG23

    Thread Starter Active Member

    Dec 6, 2010
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    I want to use one normally open contact to work as ON button

    one normally closed contact to work as OFF button

    one relay

    one light source

    +5V supply and ground

    the same +5V is the power supply for light source also

    Now my question is as follows:

    When I hit ON the light should stay ON unless I hit OFF

    Once I hit OFF the light should stay OFF unless I hit ON

    How should I connect these contacts alongwith the relay to achieve the above?

    If anyone has an idea please let me know

    Thanks
     
    Last edited: Feb 29, 2012
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Is this homework? You can lie, but God will get you.:D
     
  3. crutschow

    Expert

    Mar 14, 2008
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    Hint: You use the relay contact to power itself when ON.

    The rest you should be able to figure out.
     
  4. RG23

    Thread Starter Active Member

    Dec 6, 2010
    301
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    Sorry but I could not figure out even using your hint
     
  5. RG23

    Thread Starter Active Member

    Dec 6, 2010
    301
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    i tried different ways but still couldn't make it work
     
  6. Ron H

    AAC Fanatic!

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    If this is homework, you won't learn much by getting it handed to you, but here it is.
     
  7. BSomer

    Member

    Dec 28, 2011
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    crutschow's
    hint requires the use of a DPDT relay. One set of contacts will be used for his hint. The other set of contacts will be used for your application.

    This is my hint. :D

    How much experience do you have working with relays and electronics? I could give the answer but will you have learned anything? Experimentation, in my opinion, is part of the fun of learning. :)
     
  8. RG23

    Thread Starter Active Member

    Dec 6, 2010
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    no its not homework

    i am trying to learn ladder logic

    came across this question

    but in your solution once the NO contact opens i think the coil will get de-energised and the relay contact will open

    then how will 5V appear across lamp????
     
  9. RG23

    Thread Starter Active Member

    Dec 6, 2010
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    How much experience do you have working with relays and electronics? I could give the answer but will you have learned anything?
    _______________________________________________________________

    I have never worked with relays before
     
  10. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    The NO switch energizes the relay when it is depressed. The relay contacts close, keeping the relay on and lighting the lamp. The NC contacts release the relay, breaking the circuit.
     
  11. BSomer

    Member

    Dec 28, 2011
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    Well since it is ladder logic you could use an (OTL) and (OTU) instructions for your output.
    OTL = Output Latch
    OTU = Output Unlatch

    The OTL and OTU instructions will use the same address.

    Does this help?
     
  12. RG23

    Thread Starter Active Member

    Dec 6, 2010
    301
    2
    i read the relay concept again

    you are right thanks a lot

    Is there any specific tutorial you would recommend to learn ladder logic?

    I want to be good in plc programming

    Thanks again
     
  13. BSomer

    Member

    Dec 28, 2011
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    As for the relay part...

    I believe this is what crutschow was talking about doing...
     
  14. crutschow

    Expert

    Mar 14, 2008
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    No. Since the same power is used to power the relay that powers the light you only need a SPST relay.;)
     
  15. BSomer

    Member

    Dec 28, 2011
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    look at http://thelearningpit.com/

    They have a fairly useful program that is free to try for around 30 days or so. After that you have to buy a key.
     
  16. BSomer

    Member

    Dec 28, 2011
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    Okay. I know what you thought of then.
     
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