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seven segment time recorder — Parallax Forums

seven segment time recorder

frosliefroslie Posts: 67
edited 2005-09-08 16:04 in BASIC Stamp
hello,

I am attempting to create counter using seversl seven segment leds. I would like for the display to go up in value for x-amount of time based on an ir input. for instance, if a person is in front of the sensor the counter goes up; when nobody is front of the sensor the counter goes down.

I am considering using a TLC555 timer. I have no experience with this IC.

can anyone please pass advice as to where I can start?

thank you

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-09-08 12:08
    If you insist on using the 555 (really easy) there are a boatload of Internet sites with circuits that will get you going. But do you really need it? Seems to me like you could do this project with a BS2, and IR emitter/detector pair, and an MC14489 to mulitplex the 7-segment displays.

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    Jon Williams
    Applications Engineer, Parallax
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-09-08 14:16
    ·· And if you do decide to go the logic route, there was a schematic for a binary up/down counter in one of the old Forrest Mimms III books from Radio Shack.· It used discrete up/down inputs which could be affected using a pulse from a 555 and a gate with an input connected to the output of the IR Detector, such that when a person is in front of the gate the pulse is directed to the up input of the counter, and when absent the 555 pulse would be directed toward the down input of the counter.· Still, Jon's right, it would be much easier, less part count and more configurable if you use a BASIC Stamp, or even an SX (You could program it in SX/B).

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • frosliefroslie Posts: 67
    edited 2005-09-08 15:36
    jon,

    is the MC14489 completely needed? I would like to get started right away, and not wait for the part. thanks.

    chris,

    i do plan to attempt the SX, the starter kit is back ordered though.
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-09-08 16:04
    That depends ... how many 7-segment displays are you planning to light? If more than one then yes, you need a multiplexer. Of course, there are other ways: You could, for example, use the 74HC595 as a 7-segement driver. By daisy-chaining the 595's you can control a bunch of displays.

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    Jon Williams
    Applications Engineer, Parallax
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