need help with lm324

Discussion in 'The Projects Forum' started by janosandi, Oct 16, 2013.

  1. janosandi

    Thread Starter New Member

    Dec 29, 2009
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    hello guys
    im not good with analogue curcuits
    i need a circuit to check a voltage if its 6 or 12 v & activate 2 relays depending on this
    any help will be appriciated

    ِACTUALLY i hink to check if volt is >6 or < is enough
     
    Last edited: Oct 16, 2013
  2. BobTPH

    Active Member

    Jun 5, 2013
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    You need to be more specific. The relays should be on only if the voltage is exactly 6 or 12V? That is pretty much impossible. So please explain exactly what the relays should do for 0-6V, 6-12V and above 12V.

    Bob
     
  3. janosandi

    Thread Starter New Member

    Dec 29, 2009
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    thx Bob
    i want to activate 1 relay when i have volt between 4-6 & activate the other when its >6-12 & shut the first one off
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You could use a couple of comparators LM311 maybe and activate the first when something just below 6v and the other when just below 12v and a N.C. contact on the second relay in series with No1 coil.
    Specifics of the application would help.
    Max.
     
  5. janosandi

    Thread Starter New Member

    Dec 29, 2009
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    Thx Max
    i'll download the datasheet & work on it tomorrow
    maybe i need ur help if u r familiar with it
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    LM393 is a dual package.
    Max.
     
  7. janosandi

    Thread Starter New Member

    Dec 29, 2009
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    i have lm324 already does it work with me ?
    it has 4 comparators i know but how to do tht i searched for examples of doing such thing i didnt find
     
  8. #12

    Expert

    Nov 30, 2010
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    It depends on how accurate you need it.
    Here's a crude form that is kinda close.
    Forgot to use an amplifier chip.
    Oh well.
     
    janosandi likes this.
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That should work for a simple comparator.
    Is the voltage constantly varying, does it return to zero after >12v is reached?
    Max.
     
  10. janosandi

    Thread Starter New Member

    Dec 29, 2009
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    no its exactly 13-14 or 17-18
    its an output of digital receiver
    when its 0 its not important wht its doing i need to to know if its in 1st or 2nd condition
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You can set up something like a LM339 as a dual window comparator which has MIN - MAX out or when the minimum is reached.
    Do you need the window option?
    Or what is the desired range and operating points?
    Desired ON OFF or Don't Care voltage points.
    Max.
     
  12. janosandi

    Thread Starter New Member

    Dec 29, 2009
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    on off will be ok with me & no problem which its on or off
    the volt range for the first condition is 13-14
    & the other is 17-18

    Thx Max
     
  13. BobTPH

    Active Member

    Jun 5, 2013
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    What happened to 6 and 12?


    Bob
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You could try something like this, hopefully your voltages are steady?
    Max.
     
    Last edited: Oct 17, 2013
  15. janosandi

    Thread Starter New Member

    Dec 29, 2009
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    0
    thx Max
    i'll buy lm 339 today & try it but i couldnt understand wht resistors i've to put for the inputs U've put 6 value how to decide wht to use ?
     
    Last edited: Oct 17, 2013
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The LM339 is a quad package so you need all four, the other 2 is just a duplicate of the first two, the two sets of resistors are for each window pair.
    For the LM339 you may want to change the 750Ω base resistors to 1.5k.
    Max.
     
    Last edited: Oct 17, 2013
  17. MaxHeadRoom

    Expert

    Jul 18, 2013
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    See modified PDF.
    Max.
     
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