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HELP:electronic billboard

Discussion in 'Electronic Basics' started by nayr_kupal, Feb 11, 2006.

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  1. nayr_kupal

    nayr_kupal Guest

    can anyone please help me in doing my project.its an electronic
    billboard running display using only logic gates and LEDs...i'm having
    trouble with the design because we are not allowed to use PICs...if it
    is not too much to ask, can you please send me an schematic for a
    running display of the word "WELCOME"? thank you for your help
  2. Rob

    Rob Guest

    Hello Nayr
    If you are allowed only logic gates, then this is going to be a large
    project. I mean that there is going to be a lot of circuitry. Are you
    allowed to use counters, flip-flops and latches?
    This is doable if you can use counters and latches (e.g. anything from
    the '74' TTL logic range), but it will involve a lot of circuitry and
    the message it displays will esentially be hardwired into it.
    If can use 74 logic, will post design on website (when I get it
  3. Noway2

    Noway2 Guest

    You do realize that this is almost cerainly a project assignment for

    I can't think of any other reason why somebody would attempt to do this
    discrete logic unless they were trying to enforce combinational and
    sequential logic design.

    Personally, I am getting really tired of reading "Please Send Me" from
    everybody that want to be handed a design for their homework. When I
    was in school, I would have been delighted just to have a usenet group
    to be able to get hints from.
  4. Rob

    Rob Guest

    Yes, It's obviously a school project assignment. Just had some time on
    my hands and thought it sounded like an interesting thing to do.
  5. Chris

    Chris Guest

    Yup. Probably not a direct assignment, more like a "choose your own
    project". No teacher would ask students to do something like this
    directly. Not only that, but this is going to be expensive.

    Mr. Kupal has a couple of options, as I see it. He can go back to his
    teacher and ask for another project, because this one is gonna be
    "acres o' digital". One possibility more within the reach of a novice
    electronics student would be getting one 16-segment alphanumeric LED
    display, and then scrolling the letters at one per second, with two
    blanks after the word. Still a bit of '70s digital logic, but very
    doable, especially if he's allowed a couple of PROMs. And within a
    student's budget, too.

    Second, he can find a copy of Don Lancaster's TV Typewriter Cookbook
    (Mr. Lancaster will be more than willing to send a copy ) and look for hints as to how
    to do something like this. I'd figure he's doomed unless he can use an
    EPROM at least to store the data, then he can probably use a triple
    counter (one for multiplexing, one for data, and another for data start
    position) to achieve the scrolling effect. Not easy. There's a good
    reason why these things didn't exist before microcontrollers.

    The third option is to utilize this newsgroup as the OP says -- you do
    the work, and send him the bill. Ask for cash in advance.

    Good luck
  6. Bob Monsen

    Bob Monsen Guest

    Use a mechanical 'paper tape' loop. Columns of 7 LEDs; when the hole
    in the tape is under the led, it is grounded, and allows current to
    flow through. Each LED should be connected to the supply through a small
    resistor, the value of which is dependent on how bright you want the LED
    to be. Use a little DC motor to turn the tape on a spindle. If you did it
    properly, you could use the actual LED leads as the contact points. A
    gearmotor that runs fairly slowly is the best way to turn it, unless you
    want to get into your own gears or belts.

    Bob Monsen

    We should take care not to make the intellect our god; it has, of
    course, powerful muscles, but no personality.
    Albert Einstein
  7. Rich Grise

    Rich Grise Guest

    Or just use the tape itself to do the scrolling. Perforate a tape that's
    about 3" wide, put it in front of an EL panel or some kind of backlight,
    and put a "diffuser" on the front that's got like an array of little
    bumps, like a bee's eye - that'll give the strobing effect.

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