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counter circuit help needed

Discussion in 'Electronic Basics' started by Silvester, Mar 7, 2006.

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  1. Silvester

    Silvester Guest

    I'm looking for some help with a counting circuit.

    I have a schematic from an OLD Radio Shack book that drives a 7490 with
    a 555.
    The 7490 dumps into a 7448, which in turn displays the number on a
    7-segment LED.

    I need a similar circuit that will count DOWN from a predefined number
    - say 255 using DIP switches to set the number in binary.

    The problem is, I have been unable to find anything on the internet.

    I plan to use a matched pair of LEDs (IR emitter/receiver) to count
    objects passing a point rather than the 555 timer portion of the
    And I need a RESET button to send the count back to 255 or what ever
    number is preconfigured by the DIP switches.

    Can anyone help me out?

  2. Rich Grise

    Rich Grise Guest

    Go to the "housewares" or "kitchen aids" department of your local
    supermarket or general store, and get a digital kitchen timer for
    about $10.00.

  3. You can use the 74LS191 for binary up/down counting. Two pieces cascaded
    will count up/down the 0-255 range and you can use dipswitches for the
    preset. It will not be very easy to make a decimal readout but you can use
    binary - using LEDs - instead. Guess you'd best start downloading the
    appropriate datasheet.

    petrus bitbyter
  4. Silvester

    Silvester Guest

    Electronics is really not my thing. I can assemble a schematic, but not
    design a circuit.

    Is there any chance you could set me up with a schematic of what you
    are thinking?
  5. Rich Grise

    Rich Grise Guest

    Three of '190 or '192 would count in BCD, so you could go to 999, if you
    wanted to.

  6. John Fields

    John Fields Guest


    "Summarize what you're following up.

    When you click "Reply" under "show options" to follow up an existing
    article, Google Groups includes the full article in quotes, with the
    cursor at the top of the article. Tempting though it is to just
    start typing your message, please STOP and do two things first. Look
    at the quoted text and remove parts that are irrelevant. Then, go to
    the BOTTOM of the article and start typing there. Doing this makes
    it much easier for your readers to get through your post. They'll
    have a reminder of the relevant text before your comment, but won't
    have to re-read the entire article. And if your reply appears on a
    site before the original article does, they'll get the gist of what
    you're talking about."

    In other words, be considerate and leave a little of the article
    you're responding to in your reply, and bottom post. That makes it
    easy for us all to see to whom and to what you're responding without
    having to backtrack through the header trail to see where you're
    coming from.
  7. John Fields

    John Fields Guest

  8. ehsjr

    ehsjr Guest

    Take a look at the following kit to see if it will work
    for you:
  9. Roy L. Fuchs

    Roy L. Fuchs Guest

    Could you post it again, or the link to the non binary access
  10. John Fields

    John Fields Guest

  11. Roy L. Fuchs

    Roy L. Fuchs Guest


    Funny, I worked for the premiere pharmaceutical tablet counter maker
    at one time (hole in the wall 12 employees).

    It had 16 optical channels, and only got one parallax error per one
    thousand pill drops, if it ever got any.

    It was possible though as two pills could pass a sensor together and
    be read as one, though rare. They were LEDs and detectors in 16
    circumferentially placed pill channels sitting under a cone.

    Pour pills in at top, and stop when your prescription number is
    reached. All channel count up and add to show in the display.
    Pull drawer out pour into bottle.

    Pharmacists that had the bucks didn't have to scrape fives with the
    pill ladle!

    Anyway... thanks.

  12. Now, a lot of the drug companies pre-package in common quantities.
    The medicine that I get from the VA is all pre-packaged for either 30 or
    90 days.

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
  13. Eric R Snow

    Eric R Snow Guest

    They just weigh my pills to count 'em at my local pharmacy.

  14. I don't have to go to a pharmacy. I log in to and click on the refills that I need. They
    show up in my mailbox a few days later. Very handy, since the nearest VA
    pharmacy is over 100 miles away.

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
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