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Dividing By Two

Discussion in 'Electronic Basics' started by Chip Hollis, Sep 26, 2003.

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  1. Chip Hollis

    Chip Hollis Guest

    Can someone tell me how to wire a 7490 decade counter to
    divide by two? I can't seem to find a schematic anywhere.
  2. Chip,

    A 7490 contains a divide by two counter and a divide by five counter. As for
    the divide by two counter the input is on pin 14 and the output on pin 12.
    Of course you will have to satisfy the preset and clear inputs 2,3,6 and 7.
    Keep them low. It's also good practice to keep the unused inputs at a fixed
    value. So keep pin 1 high, preferrable via a 10k resistor just to stay on
    the safe side. All of this can be checked by reading the data sheet. A
    little Google and you know all you need and more.

  3. grahamk

    grahamk Guest

    have a look at
    Beginners and Intermediate Electronics
  4. Using a DECADE counter to divide by two? Talk about overkill...

    All you need is a D-type flip-flop. A 7474 will do nicely. Simply
    wire the Q-not output to the 'D' input, send your input to the CLK lead,
    and take your output from the Q output. Simple, neat, reliable.

    73 de KC7GR
  5. Chip Hollis

    Chip Hollis Guest

    I had a few 7490s lying around, but next time I'll keep this
    in mind. Thanks.

    Dr. Anton Squeegee wrote in message ...
  6. Chip Hollis

    Chip Hollis Guest

    Thanks, Pieter.

    petrus bitbyter wrote in message ...
  7. John Fortier

    John Fortier Guest

    You can download the manufacturers specification sheet from
    You'll have to register, but that's free. Just follow the products to the
    7490, and click on the tech info tab. You'll get a choice of half a dozen
    manufacturers data sheets.

    I use RS this way for getting info all the time. They are also an excellent
    source of parts and, although located in the UK, will ship transatlantic at
    very low cost.

    There's also a very good explanation of the whole thing in "The Art of
    Electronics, by Horowitz and Hill, which should be available in the
    technical reference section of any central library close to you.

    If all else fails, e-mail me and I'll scan the relevant pages and send them
    to you.

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