very urgent school question

Discussion in 'Homework Help' started by kortsluiting, Sep 1, 2010.

  1. kortsluiting

    Thread Starter New Member

    Sep 1, 2010
    6
    0
    Hey,

    I got a question:

    I need to make a boolean system,
    and as I am new to boolean, and as I havent got any theory on how to do this, I really want to learn how.

    The question is :

    Make a system, where you have 3 input signals(on/off buttons), and 8 output signals (lamps)
    Make sure, that you can control al 8 lights with the 3 imput signals (on.off switches)

    So I really have no idea on how to do this.

    It is even worse, they never taught me how to make truth-tables, or how to make a system out of a truth table.

    I'm Desperate, as I need to have this system at monday.

    If anyone requires more information, to help it solve, please ask.

    Thanks.

    Edit: BTW, I can use :" And,nand,or,nor,xor and xnor
     
  2. Markd77

    Senior Member

    Sep 7, 2009
    2,803
    594
    You are looking for a 3-8 line decoder/demultiplexer. Have a look at the datasheet for the 74LS138 chip and you might find some help there.
     
  3. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Google 3 bit to 8 line decoder or 3-to-8 decoder and you will have the gist of the problem. There are integrated circuits that will do this for you - or at least provide the heart of the necessary logic.
     
  4. kortsluiting

    Thread Starter New Member

    Sep 1, 2010
    6
    0
    K i will look into it.

    Though i cannot use chips in my system, as it is just digital.

    I use the program Labview, if that makes anything clear.

    I need to do something like this, http://img517.imageshack.us/img517/8229/labview.jpg(dont mention the way i connected these things, its just that i canshow you what the program does.)

    At the bottom, you can see what i can use.
     
  5. kortsluiting

    Thread Starter New Member

    Sep 1, 2010
    6
    0
    Im going to sleep now, feel free to discuss it, as ill read it tomorrow ;) ( 1:14 A.M. here)
     
  6. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
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  7. kortsluiting

    Thread Starter New Member

    Sep 1, 2010
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    Per and,nand,or,nor,xor,xnor port, I only have 2 input and 1 output option, for wiring, as you can see in the imageshack link i posted(scroll up)

    for example: 2 wires go to an Xor port. and only 1 can come out.

    But in the schedule you linked me, I have to add 3 inputs, instead of 2, so I guess that schedule is undoable for me, thanks though.
     
  8. AMIT_GOHEL

    Member

    Jul 13, 2010
    67
    7
    Hello kortsluiting,
    welcome to forum...

    circuit i've atteched may be your reqired once..

    regards...
     
  9. kortsluiting

    Thread Starter New Member

    Sep 1, 2010
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    0
    Yeah thats what i was thinking about aswell, but as you see, 3 wires go into the AND, and with labview you can only get 2 wires inside.

    When i try to put 3 inside them, i get the following error:

    A wire can be connected to only one data source, such as a control's terminal or a function output. This wire is connected to more than one source. If one source is a control, you may wish to change it to an indicator. Otherwise, you must disconnect all but one of the sources.
     
  10. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    If Labview doesn't support 3-input AND gates, you can bypass this constraint by creating a 3-input AND with 2 2-input AND gates. Simply AND the two first inputs and AND the third with the result.
     
  11. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    In Labview you can make 44 input and if you want to do so. But you have to use a function named "Compound Arithmetic" this can be scaled as you want, both in function and width
     
  12. AMIT_GOHEL

    Member

    Jul 13, 2010
    67
    7
    You can use 2 2-input and gate to solve your problem,first AND any two input and then AND the o/p of first AND and rest of input.

    I've conclude a genral rule..
    to AND,OR,XOR n-input with 2-input device you need n-1 gate...

    Regards...
    AMIT GOHEL
     
  13. kortsluiting

    Thread Starter New Member

    Sep 1, 2010
    6
    0
    Solved. Can close it now
     
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