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Random LED's

Discussion in 'Beginner Electronics' started by Bill, Jun 30, 2006.

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  1. Bill

    Bill Guest

    Does anyone know a good and simple way to have 4 LEDs blink in a random
    pattern
     
  2. Chris Head

    Chris Head Guest

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    My preference for a simple way would be to use a PIC microcontroller
    (pick your own preferred type here), and put something like a linear
    congruential generator on it (see Wikipedia - generating a number
    requires just a multiply and an add, if you let M be a power of 2).
    Once you generate an 8-bit output, use the upper 4 bits for your LEDs
    and throw away the lower 4 bits (the lower bits of a linear
    congruential generator have awful randomness). With an appropriate
    PIC, you can do this with literally nothing but the chip, a power
    supply, the LEDs, and the current-limiting resistors. Something like
    the 16F627A/16F628A/16F648A have a built-in oscillator and can run
    from 3 to 5.5 volts, so 3 AA batteries would power the whole system.
    You can also get the 16LF variant (instead of 16F) which can run down
    to 2V, so you could use only 2 batteries. I'm not familiar with the
    10F series, but you can probably find a 10F series PIC that'll do the
    job just as well, and the 10F series have only 8 pins where the
    16F648A has 18, so you'd use a lot less space.

    On the other hand, if you've never done any microcontroller work, it's
    a big job to get started.

    Chris
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  3. Bill

    Bill Guest

    I have never used a PIC, do you have a Schematic?
     
  4. Chris Head

    Chris Head Guest

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    Unfortunately a schematic won't help. A PIC is a type of
    microcontroller, so you have to write code and then burn it into the
    chip. Writing the code requires a computer and programming knowledge,
    and burning it into the chip requires specialized hardware (a
    programmer). If you HAD these resources already available, a PIC would
    be both easy and cheap. If you have to acquire any of the above, it
    will be either difficult, expensive, or both, and I would suggest a
    different approach (at this point I stop being able to help you, since
    I don't know off-hand another way to solve your problem).

    Chris

    Bill wrote:
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  5. Tater Schuld

    Tater Schuld Guest

    cripes, why have the guys spend hundreds of dollars in development tools for
    a single application.

    simple solution, get 4 blinking LEDs, wire them in parallel. after an hour
    they'll be random enough.
     
  6. Chris Head

    Chris Head Guest

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    Heh... because if you already HAVE the tools, because you do OTHER
    things with microcontrollers, then it's only a few dollars, and the
    solution is very small in terms of space taken up. I did say that if
    you don't already have the tools and knowledge this probably isn't a
    good idea.

    Chris

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