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element14 presents Forum DIY Discrete Logic LED Countdown Timer
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Related

DIY Discrete Logic LED Countdown Timer

evo
evo 4 months ago

Hey everyone, I'm trying to create a countdown system, but I'm having trouble understanding how everything works together. I'm not really sure how to chain the parts properly. Could someone please show me a clear schematic or example of how to connect everything step by step?

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  • beacon_dave
    beacon_dave 4 months ago +3 suggested
    I'm assuming that you are referring to the element 14 Presents timer project ? /challenges-projects/element14-presents/project-videos/w/documents/5402/diy-discrete-logic-led-countdown-timer----episode…
  • beacon_dave
    beacon_dave 4 months ago +2
    Start with the clock circuit: and connect the 1Hz output (top right) to the Clk input (middle left) of the 1's counter: Then connect the CarryOut (lower right) to the Clk input (upper middle left…
  • evo
    evo 4 months ago in reply to beacon_dave +1
    do you know what the full one is with everyting
  • beacon_dave
    beacon_dave 4 months ago in reply to evo +1
    Yes, but I think you need to remove the reset logic on the 1's counter for the minutes and the 1's counter for the hours as they will need to show 0-9 and not 0-5.
  • beacon_dave
    beacon_dave 4 months ago in reply to evo +1
    It looks like you are almost there. It is perhaps time to start building a prototype on some breadboard to help understand the circuit. If you start with one decade counter connected to one display driver…
  • evo
    0 evo 4 months ago in reply to beacon_dave

    image

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  • beacon_dave
    0 beacon_dave 4 months ago in reply to evo

    Where you have removed the logic you probably want to pull the preset enable pin low rather than leave it floating

    image

    as per the original schematic

    image

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  • evo
    0 evo 4 months ago in reply to beacon_dave

    heb je easyeda, ik ben nog vrij nieuw bij al dit dus zou je mischien kunnen helpen met het maken van alles, je kan ook altijd de webversie gebruiken

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  • beacon_dave
    0 beacon_dave 4 months ago in reply to evo

    It looks like you are almost there. It is perhaps time to start building a prototype on some breadboard to help understand the circuit.

    If you start with one decade counter connected to one display driver you can clock it manually using the switch and watch the results on the display.

    Build a second decade counter circuit and add the preset logic to see it counting down from 5 instead of 9. 

    Then join the two together to see the cascade working.

    Build the clock circuit and test it counting down from 59 seconds. 

    Add in another two decade counters for the minutes display, and then another two decade counters for the hours display.

    There is more information on how decade counters work over on episode 73 of The Learning Circuit:

    /challenges-projects/element14-presents/thelearningcircuit/w/documents/4898/how-decade-counters-work----the-learning-circuit-73

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